kernel/bpf/btf.c

/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (c) 2018 Facebook */

#include <uapi/linux/btf.h>
#include <uapi/linux/bpf.h>
#include <uapi/linux/bpf_perf_event.h>
#include <uapi/linux/types.h>
#include <linux/seq_file.h>
#include <linux/compiler.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/idr.h>
#include <linux/sort.h>
#include <linux/bpf_verifier.h>
#include <linux/btf.h>
#include <linux/skmsg.h>
#include <linux/perf_event.h>
#include <net/sock.h>

/* BTF (BPF Type Format) is the meta data format which describes
 * the data types of BPF program/map.  Hence, it basically focus
 * on the C programming language which the modern BPF is primary
 * using.
 *
 * ELF Section:
 * ~~~~~~~~~~~
 * The BTF data is stored under the ".BTF" ELF section
 *
 * struct btf_type:
 * ~~~~~~~~~~~~~~~
 * Each 'struct btf_type' object describes a C data type.
 * Depending on the type it is describing, a 'struct btf_type'
 * object may be followed by more data.  F.e.
 * To describe an array, 'struct btf_type' is followed by
 * 'struct btf_array'.
 *
 * 'struct btf_type' and any extra data following it are
 * 4 bytes aligned.
 *
 * Type section:
 * ~~~~~~~~~~~~~
 * The BTF type section contains a list of 'struct btf_type' objects.
 * Each one describes a C type.  Recall from the above section
 * that a 'struct btf_type' object could be immediately followed by extra
 * data in order to desribe some particular C types.
 *
 * type_id:
 * ~~~~~~~
 * Each btf_type object is identified by a type_id.  The type_id
 * is implicitly implied by the location of the btf_type object in
 * the BTF type section.  The first one has type_id 1.  The second
 * one has type_id 2...etc.  Hence, an earlier btf_type has
 * a smaller type_id.
 *
 * A btf_type object may refer to another btf_type object by using
 * type_id (i.e. the "type" in the "struct btf_type").
 *
 * NOTE that we cannot assume any reference-order.
 * A btf_type object can refer to an earlier btf_type object
 * but it can also refer to a later btf_type object.
 *
 * For example, to describe "const void *".  A btf_type
 * object describing "const" may refer to another btf_type
 * object describing "void *".  This type-reference is done
 * by specifying type_id:
 *
 * [1] CONST (anon) type_id=2
 * [2] PTR (anon) type_id=0
 *
 * The above is the btf_verifier debug log:
 *   - Each line started with "[?]" is a btf_type object
 *   - [?] is the type_id of the btf_type object.
 *   - CONST/PTR is the BTF_KIND_XXX
 *   - "(anon)" is the name of the type.  It just
 *     happens that CONST and PTR has no name.
 *   - type_id=XXX is the 'u32 type' in btf_type
 *
 * NOTE: "void" has type_id 0
 *
 * String section:
 * ~~~~~~~~~~~~~~
 * The BTF string section contains the names used by the type section.
 * Each string is referred by an "offset" from the beginning of the
 * string section.
 *
 * Each string is '\0' terminated.
 *
 * The first character in the string section must be '\0'
 * which is used to mean 'anonymous'. Some btf_type may not
 * have a name.
 */

/* BTF verification:
 *
 * To verify BTF data, two passes are needed.
 *
 * Pass #1
 * ~~~~~~~
 * The first pass is to collect all btf_type objects to
 * an array: "btf->types".
 *
 * Depending on the C type that a btf_type is describing,
 * a btf_type may be followed by extra data.  We don't know
 * how many btf_type is there, and more importantly we don't
 * know where each btf_type is located in the type section.
 *
 * Without knowing the location of each type_id, most verifications
 * cannot be done.  e.g. an earlier btf_type may refer to a later
 * btf_type (recall the "const void *" above), so we cannot
 * check this type-reference in the first pass.
 *
 * In the first pass, it still does some verifications (e.g.
 * checking the name is a valid offset to the string section).
 *
 * Pass #2
 * ~~~~~~~
 * The main focus is to resolve a btf_type that is referring
 * to another type.
 *
 * We have to ensure the referring type:
 * 1) does exist in the BTF (i.e. in btf->types[])
 * 2) does not cause a loop:
 *	struct A {
 *		struct B b;
 *	};
 *
 *	struct B {
 *		struct A a;
 *	};
 *
 * btf_type_needs_resolve() decides if a btf_type needs
 * to be resolved.
 *
 * The needs_resolve type implements the "resolve()" ops which
 * essentially does a DFS and detects backedge.
 *
 * During resolve (or DFS), different C types have different
 * "RESOLVED" conditions.
 *
 * When resolving a BTF_KIND_STRUCT, we need to resolve all its
 * members because a member is always referring to another
 * type.  A struct's member can be treated as "RESOLVED" if
 * it is referring to a BTF_KIND_PTR.  Otherwise, the
 * following valid C struct would be rejected:
 *
 *	struct A {
 *		int m;
 *		struct A *a;
 *	};
 *
 * When resolving a BTF_KIND_PTR, it needs to keep resolving if
 * it is referring to another BTF_KIND_PTR.  Otherwise, we cannot
 * detect a pointer loop, e.g.:
 * BTF_KIND_CONST -> BTF_KIND_PTR -> BTF_KIND_CONST -> BTF_KIND_PTR +
 *                        ^                                         |
 *                        +-----------------------------------------+
 *
 */

#define BITS_PER_U128 (sizeof(u64) * BITS_PER_BYTE * 2)
#define BITS_PER_BYTE_MASK (BITS_PER_BYTE - 1)
#define BITS_PER_BYTE_MASKED(bits) ((bits) & BITS_PER_BYTE_MASK)
#define BITS_ROUNDDOWN_BYTES(bits) ((bits) >> 3)
#define BITS_ROUNDUP_BYTES(bits) \
	(BITS_ROUNDDOWN_BYTES(bits) + !!BITS_PER_BYTE_MASKED(bits))

#define BTF_INFO_MASK 0x8f00ffff
#define BTF_INT_MASK 0x0fffffff
#define BTF_TYPE_ID_VALID(type_id) ((type_id) <= BTF_MAX_TYPE)
#define BTF_STR_OFFSET_VALID(name_off) ((name_off) <= BTF_MAX_NAME_OFFSET)

/* 16MB for 64k structs and each has 16 members and
 * a few MB spaces for the string section.
 * The hard limit is S32_MAX.
 */
#define BTF_MAX_SIZE (16 * 1024 * 1024)

#define for_each_member_from(i, from, struct_type, member)		\
	for (i = from, member = btf_type_member(struct_type) + from;	\
	     i < btf_type_vlen(struct_type);				\
	     i++, member++)

#define for_each_vsi(i, struct_type, member)			\
	for (i = 0, member = btf_type_var_secinfo(struct_type);	\
	     i < btf_type_vlen(struct_type);			\
	     i++, member++)

#define for_each_vsi_from(i, from, struct_type, member)				\
	for (i = from, member = btf_type_var_secinfo(struct_type) + from;	\
	     i < btf_type_vlen(struct_type);					\
	     i++, member++)

DEFINE_IDR(btf_idr);
DEFINE_SPINLOCK(btf_idr_lock);

struct btf {
	void *data;
	struct btf_type **types;
	u32 *resolved_ids;
	u32 *resolved_sizes;
	const char *strings;
	void *nohdr_data;
	struct btf_header hdr;
	u32 nr_types;
	u32 types_size;
	u32 data_size;
	refcount_t refcnt;
	u32 id;
	struct rcu_head rcu;
};

enum verifier_phase {
	CHECK_META,
	CHECK_TYPE,
};

struct resolve_vertex {
	const struct btf_type *t;
	u32 type_id;
	u16 next_member;
};

enum visit_state {
	NOT_VISITED,
	VISITED,
	RESOLVED,
};

enum resolve_mode {
	RESOLVE_TBD,	/* To Be Determined */
	RESOLVE_PTR,	/* Resolving for Pointer */
	RESOLVE_STRUCT_OR_ARRAY,	/* Resolving for struct/union
					 * or array
					 */
};

#define MAX_RESOLVE_DEPTH 32

struct btf_sec_info {
	u32 off;
	u32 len;
};

struct btf_verifier_env {
	struct btf *btf;
	u8 *visit_states;
	struct resolve_vertex stack[MAX_RESOLVE_DEPTH];
	struct bpf_verifier_log log;
	u32 log_type_id;
	u32 top_stack;
	enum verifier_phase phase;
	enum resolve_mode resolve_mode;
};

static const char * const btf_kind_str[NR_BTF_KINDS] = {
	[BTF_KIND_UNKN]		= "UNKNOWN",
	[BTF_KIND_INT]		= "INT",
	[BTF_KIND_PTR]		= "PTR",
	[BTF_KIND_ARRAY]	= "ARRAY",
	[BTF_KIND_STRUCT]	= "STRUCT",
	[BTF_KIND_UNION]	= "UNION",
	[BTF_KIND_ENUM]		= "ENUM",
	[BTF_KIND_FWD]		= "FWD",
	[BTF_KIND_TYPEDEF]	= "TYPEDEF",
	[BTF_KIND_VOLATILE]	= "VOLATILE",
	[BTF_KIND_CONST]	= "CONST",
	[BTF_KIND_RESTRICT]	= "RESTRICT",
	[BTF_KIND_FUNC]		= "FUNC",
	[BTF_KIND_FUNC_PROTO]	= "FUNC_PROTO",
	[BTF_KIND_VAR]		= "VAR",
	[BTF_KIND_DATASEC]	= "DATASEC",
};

static const char *btf_type_str(const struct btf_type *t)
{
	return btf_kind_str[BTF_INFO_KIND(t->info)];
}

struct btf_kind_operations {
	s32 (*check_meta)(struct btf_verifier_env *env,
			  const struct btf_type *t,
			  u32 meta_left);
	int (*resolve)(struct btf_verifier_env *env,
		       const struct resolve_vertex *v);
	int (*check_member)(struct btf_verifier_env *env,
			    const struct btf_type *struct_type,
			    const struct btf_member *member,
			    const struct btf_type *member_type);
	int (*check_kflag_member)(struct btf_verifier_env *env,
				  const struct btf_type *struct_type,
				  const struct btf_member *member,
				  const struct btf_type *member_type);
	void (*log_details)(struct btf_verifier_env *env,
			    const struct btf_type *t);
	void (*seq_show)(const struct btf *btf, const struct btf_type *t,
			 u32 type_id, void *data, u8 bits_offsets,
			 struct seq_file *m);
};

static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS];
static struct btf_type btf_void;

static int btf_resolve(struct btf_verifier_env *env,
		       const struct btf_type *t, u32 type_id);

static bool btf_type_is_modifier(const struct btf_type *t)
{
	/* Some of them is not strictly a C modifier
	 * but they are grouped into the same bucket
	 * for BTF concern:
	 *   A type (t) that refers to another
	 *   type through t->type AND its size cannot
	 *   be determined without following the t->type.
	 *
	 * ptr does not fall into this bucket
	 * because its size is always sizeof(void *).
	 */
	switch (BTF_INFO_KIND(t->info)) {
	case BTF_KIND_TYPEDEF:
	case BTF_KIND_VOLATILE:
	case BTF_KIND_CONST:
	case BTF_KIND_RESTRICT:
		return true;
	}

	return false;
}

bool btf_type_is_void(const struct btf_type *t)
{
	return t == &btf_void;
}

static bool btf_type_is_fwd(const struct btf_type *t)
{
	return BTF_INFO_KIND(t->info) == BTF_KIND_FWD;
}

static bool btf_type_nosize(const struct btf_type *t)
{
	return btf_type_is_void(t) || btf_type_is_fwd(t) ||
	       btf_type_is_func(t) || btf_type_is_func_proto(t);
}

static bool btf_type_nosize_or_null(const struct btf_type *t)
{
	return !t || btf_type_nosize(t);
}

/* union is only a special case of struct:
 * all its offsetof(member) == 0
 */
static bool btf_type_is_struct(const struct btf_type *t)
{
	u8 kind = BTF_INFO_KIND(t->info);

	return kind == BTF_KIND_STRUCT || kind == BTF_KIND_UNION;
}

static bool __btf_type_is_struct(const struct btf_type *t)
{
	return BTF_INFO_KIND(t->info) == BTF_KIND_STRUCT;
}

static bool btf_type_is_array(const struct btf_type *t)
{
	return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY;
}

static bool btf_type_is_var(const struct btf_type *t)
{
	return BTF_INFO_KIND(t->info) == BTF_KIND_VAR;
}

static bool btf_type_is_datasec(const struct btf_type *t)
{
	return BTF_INFO_KIND(t->info) == BTF_KIND_DATASEC;
}

s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind)
{
	const struct btf_type *t;
	const char *tname;
	u32 i;

	for (i = 1; i <= btf->nr_types; i++) {
		t = btf->types[i];
		if (BTF_INFO_KIND(t->info) != kind)
			continue;

		tname = btf_name_by_offset(btf, t->name_off);
		if (!strcmp(tname, name))
			return i;
	}

	return -ENOENT;
}

const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
					       u32 id, u32 *res_id)
{
	const struct btf_type *t = btf_type_by_id(btf, id);

	while (btf_type_is_modifier(t)) {
		id = t->type;
		t = btf_type_by_id(btf, t->type);
	}

	if (res_id)
		*res_id = id;

	return t;
}

const struct btf_type *btf_type_resolve_ptr(const struct btf *btf,
					    u32 id, u32 *res_id)
{
	const struct btf_type *t;

	t = btf_type_skip_modifiers(btf, id, NULL);
	if (!btf_type_is_ptr(t))
		return NULL;

	return btf_type_skip_modifiers(btf, t->type, res_id);
}

const struct btf_type *btf_type_resolve_func_ptr(const struct btf *btf,
						 u32 id, u32 *res_id)
{
	const struct btf_type *ptype;

	ptype = btf_type_resolve_ptr(btf, id, res_id);
	if (ptype && btf_type_is_func_proto(ptype))
		return ptype;

	return NULL;
}

/* Types that act only as a source, not sink or intermediate
 * type when resolving.
 */
static bool btf_type_is_resolve_source_only(const struct btf_type *t)
{
	return btf_type_is_var(t) ||
	       btf_type_is_datasec(t);
}

/* What types need to be resolved?
 *
 * btf_type_is_modifier() is an obvious one.
 *
 * btf_type_is_struct() because its member refers to
 * another type (through member->type).
 *
 * btf_type_is_var() because the variable refers to
 * another type. btf_type_is_datasec() holds multiple
 * btf_type_is_var() types that need resolving.
 *
 * btf_type_is_array() because its element (array->type)
 * refers to another type.  Array can be thought of a
 * special case of struct while array just has the same
 * member-type repeated by array->nelems of times.
 */
static bool btf_type_needs_resolve(const struct btf_type *t)
{
	return btf_type_is_modifier(t) ||
	       btf_type_is_ptr(t) ||
	       btf_type_is_struct(t) ||
	       btf_type_is_array(t) ||
	       btf_type_is_var(t) ||
	       btf_type_is_datasec(t);
}

/* t->size can be used */
static bool btf_type_has_size(const struct btf_type *t)
{
	switch (BTF_INFO_KIND(t->info)) {
	case BTF_KIND_INT:
	case BTF_KIND_STRUCT:
	case BTF_KIND_UNION:
	case BTF_KIND_ENUM:
	case BTF_KIND_DATASEC:
		return true;
	}

	return false;
}

static const char *btf_int_encoding_str(u8 encoding)
{
	if (encoding == 0)
		return "(none)";
	else if (encoding == BTF_INT_SIGNED)
		return "SIGNED";
	else if (encoding == BTF_INT_CHAR)
		return "CHAR";
	else if (encoding == BTF_INT_BOOL)
		return "BOOL";
	else
		return "UNKN";
}

static u32 btf_type_int(const struct btf_type *t)
{
	return *(u32 *)(t + 1);
}

static const struct btf_array *btf_type_array(const struct btf_type *t)
{
	return (const struct btf_array *)(t + 1);
}

static const struct btf_enum *btf_type_enum(const struct btf_type *t)
{
	return (const struct btf_enum *)(t + 1);
}

static const struct btf_var *btf_type_var(const struct btf_type *t)
{
	return (const struct btf_var *)(t + 1);
}

static const struct btf_var_secinfo *btf_type_var_secinfo(const struct btf_type *t)
{
	return (const struct btf_var_secinfo *)(t + 1);
}

static const struct btf_kind_operations *btf_type_ops(const struct btf_type *t)
{
	return kind_ops[BTF_INFO_KIND(t->info)];
}

static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
{
	return BTF_STR_OFFSET_VALID(offset) &&
		offset < btf->hdr.str_len;
}

static bool __btf_name_char_ok(char c, bool first, bool dot_ok)
{
	if ((first ? !isalpha(c) :
		     !isalnum(c)) &&
	    c != '_' &&
	    ((c == '.' && !dot_ok) ||
	      c != '.'))
		return false;
	return true;
}

static bool __btf_name_valid(const struct btf *btf, u32 offset, bool dot_ok)
{
	/* offset must be valid */
	const char *src = &btf->strings[offset];
	const char *src_limit;

	if (!__btf_name_char_ok(*src, true, dot_ok))
		return false;

	/* set a limit on identifier length */
	src_limit = src + KSYM_NAME_LEN;
	src++;
	while (*src && src < src_limit) {
		if (!__btf_name_char_ok(*src, false, dot_ok))
			return false;
		src++;
	}

	return !*src;
}

/* Only C-style identifier is permitted. This can be relaxed if
 * necessary.
 */
static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
{
	return __btf_name_valid(btf, offset, false);
}

static bool btf_name_valid_section(const struct btf *btf, u32 offset)
{
	return __btf_name_valid(btf, offset, true);
}

static const char *__btf_name_by_offset(const struct btf *btf, u32 offset)
{
	if (!offset)
		return "(anon)";
	else if (offset < btf->hdr.str_len)
		return &btf->strings[offset];
	else
		return "(invalid-name-offset)";
}

const char *btf_name_by_offset(const struct btf *btf, u32 offset)
{
	if (offset < btf->hdr.str_len)
		return &btf->strings[offset];

	return NULL;
}

const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
{
	if (type_id > btf->nr_types)
		return NULL;

	return btf->types[type_id];
}

/*
 * Regular int is not a bit field and it must be either
 * u8/u16/u32/u64 or __int128.
 */
static bool btf_type_int_is_regular(const struct btf_type *t)
{
	u8 nr_bits, nr_bytes;
	u32 int_data;

	int_data = btf_type_int(t);
	nr_bits = BTF_INT_BITS(int_data);
	nr_bytes = BITS_ROUNDUP_BYTES(nr_bits);
	if (BITS_PER_BYTE_MASKED(nr_bits) ||
	    BTF_INT_OFFSET(int_data) ||
	    (nr_bytes != sizeof(u8) && nr_bytes != sizeof(u16) &&
	     nr_bytes != sizeof(u32) && nr_bytes != sizeof(u64) &&
	     nr_bytes != (2 * sizeof(u64)))) {
		return false;
	}

	return true;
}

/*
 * Check that given struct member is a regular int with expected
 * offset and size.
 */
bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
			   const struct btf_member *m,
			   u32 expected_offset, u32 expected_size)
{
	const struct btf_type *t;
	u32 id, int_data;
	u8 nr_bits;

	id = m->type;
	t = btf_type_id_size(btf, &id, NULL);
	if (!t || !btf_type_is_int(t))
		return false;

	int_data = btf_type_int(t);
	nr_bits = BTF_INT_BITS(int_data);
	if (btf_type_kflag(s)) {
		u32 bitfield_size = BTF_MEMBER_BITFIELD_SIZE(m->offset);
		u32 bit_offset = BTF_MEMBER_BIT_OFFSET(m->offset);

		/* if kflag set, int should be a regular int and
		 * bit offset should be at byte boundary.
		 */
		return !bitfield_size &&
		       BITS_ROUNDUP_BYTES(bit_offset) == expected_offset &&
		       BITS_ROUNDUP_BYTES(nr_bits) == expected_size;
	}

	if (BTF_INT_OFFSET(int_data) ||
	    BITS_PER_BYTE_MASKED(m->offset) ||
	    BITS_ROUNDUP_BYTES(m->offset) != expected_offset ||
	    BITS_PER_BYTE_MASKED(nr_bits) ||
	    BITS_ROUNDUP_BYTES(nr_bits) != expected_size)
		return false;

	return true;
}

__printf(2, 3) static void __btf_verifier_log(struct bpf_verifier_log *log,
					      const char *fmt, ...)
{
	va_list args;

	va_start(args, fmt);
	bpf_verifier_vlog(log, fmt, args);
	va_end(args);
}

__printf(2, 3) static void btf_verifier_log(struct btf_verifier_env *env,
					    const char *fmt, ...)
{
	struct bpf_verifier_log *log = &env->log;
	va_list args;

	if (!bpf_verifier_log_needed(log))
		return;

	va_start(args, fmt);
	bpf_verifier_vlog(log, fmt, args);
	va_end(args);
}

__printf(4, 5) static void __btf_verifier_log_type(struct btf_verifier_env *env,
						   const struct btf_type *t,
						   bool log_details,
						   const char *fmt, ...)
{
	struct bpf_verifier_log *log = &env->log;
	u8 kind = BTF_INFO_KIND(t->info);
	struct btf *btf = env->btf;
	va_list args;

	if (!bpf_verifier_log_needed(log))
		return;

	/* btf verifier prints all types it is processing via
	 * btf_verifier_log_type(..., fmt = NULL).
	 * Skip those prints for in-kernel BTF verification.
	 */
	if (log->level == BPF_LOG_KERNEL && !fmt)
		return;

	__btf_verifier_log(log, "[%u] %s %s%s",
			   env->log_type_id,
			   btf_kind_str[kind],
			   __btf_name_by_offset(btf, t->name_off),
			   log_details ? " " : "");

	if (log_details)
		btf_type_ops(t)->log_details(env, t);

	if (fmt && *fmt) {
		__btf_verifier_log(log, " ");
		va_start(args, fmt);
		bpf_verifier_vlog(log, fmt, args);
		va_end(args);
	}

	__btf_verifier_log(log, "\n");
}

#define btf_verifier_log_type(env, t, ...) \
	__btf_verifier_log_type((env), (t), true, __VA_ARGS__)
#define btf_verifier_log_basic(env, t, ...) \
	__btf_verifier_log_type((env), (t), false, __VA_ARGS__)

__printf(4, 5)
static void btf_verifier_log_member(struct btf_verifier_env *env,
				    const struct btf_type *struct_type,
				    const struct btf_member *member,
				    const char *fmt, ...)
{
	struct bpf_verifier_log *log = &env->log;
	struct btf *btf = env->btf;
	va_list args;

	if (!bpf_verifier_log_needed(log))
		return;

	if (log->level == BPF_LOG_KERNEL && !fmt)
		return;
	/* The CHECK_META phase already did a btf dump.
	 *
	 * If member is logged again, it must hit an error in
	 * parsing this member.  It is useful to print out which
	 * struct this member belongs to.
	 */
	if (env->phase != CHECK_META)
		btf_verifier_log_type(env, struct_type, NULL);

	if (btf_type_kflag(struct_type))
		__btf_verifier_log(log,
				   "\t%s type_id=%u bitfield_size=%u bits_offset=%u",
				   __btf_name_by_offset(btf, member->name_off),
				   member->type,
				   BTF_MEMBER_BITFIELD_SIZE(member->offset),
				   BTF_MEMBER_BIT_OFFSET(member->offset));
	else
		__btf_verifier_log(log, "\t%s type_id=%u bits_offset=%u",
				   __btf_name_by_offset(btf, member->name_off),
				   member->type, member->offset);

	if (fmt && *fmt) {
		__btf_verifier_log(log, " ");
		va_start(args, fmt);
		bpf_verifier_vlog(log, fmt, args);
		va_end(args);
	}

	__btf_verifier_log(log, "\n");
}

__printf(4, 5)
static void btf_verifier_log_vsi(struct btf_verifier_env *env,
				 const struct btf_type *datasec_type,
				 const struct btf_var_secinfo *vsi,
				 const char *fmt, ...)
{
	struct bpf_verifier_log *log = &env->log;
	va_list args;

	if (!bpf_verifier_log_needed(log))
		return;
	if (log->level == BPF_LOG_KERNEL && !fmt)
		return;
	if (env->phase != CHECK_META)
		btf_verifier_log_type(env, datasec_type, NULL);

	__btf_verifier_log(log, "\t type_id=%u offset=%u size=%u",
			   vsi->type, vsi->offset, vsi->size);
	if (fmt && *fmt) {
		__btf_verifier_log(log, " ");
		va_start(args, fmt);
		bpf_verifier_vlog(log, fmt, args);
		va_end(args);
	}

	__btf_verifier_log(log, "\n");
}

static void btf_verifier_log_hdr(struct btf_verifier_env *env,
				 u32 btf_data_size)
{
	struct bpf_verifier_log *log = &env->log;
	const struct btf *btf = env->btf;
	const struct btf_header *hdr;

	if (!bpf_verifier_log_needed(log))
		return;

	if (log->level == BPF_LOG_KERNEL)
		return;
	hdr = &btf->hdr;
	__btf_verifier_log(log, "magic: 0x%x\n", hdr->magic);
	__btf_verifier_log(log, "version: %u\n", hdr->version);
	__btf_verifier_log(log, "flags: 0x%x\n", hdr->flags);
	__btf_verifier_log(log, "hdr_len: %u\n", hdr->hdr_len);
	__btf_verifier_log(log, "type_off: %u\n", hdr->type_off);
	__btf_verifier_log(log, "type_len: %u\n", hdr->type_len);
	__btf_verifier_log(log, "str_off: %u\n", hdr->str_off);
	__btf_verifier_log(log, "str_len: %u\n", hdr->str_len);
	__btf_verifier_log(log, "btf_total_size: %u\n", btf_data_size);
}

static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
{
	struct btf *btf = env->btf;

	/* < 2 because +1 for btf_void which is always in btf->types[0].
	 * btf_void is not accounted in btf->nr_types because btf_void
	 * does not come from the BTF file.
	 */
	if (btf->types_size - btf->nr_types < 2) {
		/* Expand 'types' array */

		struct btf_type **new_types;
		u32 expand_by, new_size;

		if (btf->types_size == BTF_MAX_TYPE) {
			btf_verifier_log(env, "Exceeded max num of types");
			return -E2BIG;
		}

		expand_by = max_t(u32, btf->types_size >> 2, 16);
		new_size = min_t(u32, BTF_MAX_TYPE,
				 btf->types_size + expand_by);

		new_types = kvcalloc(new_size, sizeof(*new_types),
				     GFP_KERNEL | __GFP_NOWARN);
		if (!new_types)
			return -ENOMEM;

		if (btf->nr_types == 0)
			new_types[0] = &btf_void;
		else
			memcpy(new_types, btf->types,
			       sizeof(*btf->types) * (btf->nr_types + 1));

		kvfree(btf->types);
		btf->types = new_types;
		btf->types_size = new_size;
	}

	btf->types[++(btf->nr_types)] = t;

	return 0;
}

static int btf_alloc_id(struct btf *btf)
{
	int id;

	idr_preload(GFP_KERNEL);
	spin_lock_bh(&btf_idr_lock);
	id = idr_alloc_cyclic(&btf_idr, btf, 1, INT_MAX, GFP_ATOMIC);
	if (id > 0)
		btf->id = id;
	spin_unlock_bh(&btf_idr_lock);
	idr_preload_end();

	if (WARN_ON_ONCE(!id))
		return -ENOSPC;

	return id > 0 ? 0 : id;
}

static void btf_free_id(struct btf *btf)
{
	unsigned long flags;

	/*
	 * In map-in-map, calling map_delete_elem() on outer
	 * map will call bpf_map_put on the inner map.
	 * It will then eventually call btf_free_id()
	 * on the inner map.  Some of the map_delete_elem()
	 * implementation may have irq disabled, so
	 * we need to use the _irqsave() version instead
	 * of the _bh() version.
	 */
	spin_lock_irqsave(&btf_idr_lock, flags);
	idr_remove(&btf_idr, btf->id);
	spin_unlock_irqrestore(&btf_idr_lock, flags);
}

static void btf_free(struct btf *btf)
{
	kvfree(btf->types);
	kvfree(btf->resolved_sizes);
	kvfree(btf->resolved_ids);
	kvfree(btf->data);
	kfree(btf);
}

static void btf_free_rcu(struct rcu_head *rcu)
{
	struct btf *btf = container_of(rcu, struct btf, rcu);

	btf_free(btf);
}

void btf_put(struct btf *btf)
{
	if (btf && refcount_dec_and_test(&btf->refcnt)) {
		btf_free_id(btf);
		call_rcu(&btf->rcu, btf_free_rcu);
	}
}

static int env_resolve_init(struct btf_verifier_env *env)
{
	struct btf *btf = env->btf;
	u32 nr_types = btf->nr_types;
	u32 *resolved_sizes = NULL;
	u32 *resolved_ids = NULL;
	u8 *visit_states = NULL;

	/* +1 for btf_void */
	resolved_sizes = kvcalloc(nr_types + 1, sizeof(*resolved_sizes),
				  GFP_KERNEL | __GFP_NOWARN);
	if (!resolved_sizes)
		goto nomem;

	resolved_ids = kvcalloc(nr_types + 1, sizeof(*resolved_ids),
				GFP_KERNEL | __GFP_NOWARN);
	if (!resolved_ids)
		goto nomem;

	visit_states = kvcalloc(nr_types + 1, sizeof(*visit_states),
				GFP_KERNEL | __GFP_NOWARN);
	if (!visit_states)
		goto nomem;

	btf->resolved_sizes = resolved_sizes;
	btf->resolved_ids = resolved_ids;
	env->visit_states = visit_states;

	return 0;

nomem:
	kvfree(resolved_sizes);
	kvfree(resolved_ids);
	kvfree(visit_states);
	return -ENOMEM;
}

static void btf_verifier_env_free(struct btf_verifier_env *env)
{
	kvfree(env->visit_states);
	kfree(env);
}

static bool env_type_is_resolve_sink(const struct btf_verifier_env *env,
				     const struct btf_type *next_type)
{
	switch (env->resolve_mode) {
	case RESOLVE_TBD:
		/* int, enum or void is a sink */
		return !btf_type_needs_resolve(next_type);
	case RESOLVE_PTR:
		/* int, enum, void, struct, array, func or func_proto is a sink
		 * for ptr
		 */
		return !btf_type_is_modifier(next_type) &&
			!btf_type_is_ptr(next_type);
	case RESOLVE_STRUCT_OR_ARRAY:
		/* int, enum, void, ptr, func or func_proto is a sink
		 * for struct and array
		 */
		return !btf_type_is_modifier(next_type) &&
			!btf_type_is_array(next_type) &&
			!btf_type_is_struct(next_type);
	default:
		BUG();
	}
}

static bool env_type_is_resolved(const struct btf_verifier_env *env,
				 u32 type_id)
{
	return env->visit_states[type_id] == RESOLVED;
}

static int env_stack_push(struct btf_verifier_env *env,
			  const struct btf_type *t, u32 type_id)
{
	struct resolve_vertex *v;

	if (env->top_stack == MAX_RESOLVE_DEPTH)
		return -E2BIG;

	if (env->visit_states[type_id] != NOT_VISITED)
		return -EEXIST;

	env->visit_states[type_id] = VISITED;

	v = &env->stack[env->top_stack++];
	v->t = t;
	v->type_id = type_id;
	v->next_member = 0;

	if (env->resolve_mode == RESOLVE_TBD) {
		if (btf_type_is_ptr(t))
			env->resolve_mode = RESOLVE_PTR;
		else if (btf_type_is_struct(t) || btf_type_is_array(t))
			env->resolve_mode = RESOLVE_STRUCT_OR_ARRAY;
	}

	return 0;
}

static void env_stack_set_next_member(struct btf_verifier_env *env,
				      u16 next_member)
{
	env->stack[env->top_stack - 1].next_member = next_member;
}

static void env_stack_pop_resolved(struct btf_verifier_env *env,
				   u32 resolved_type_id,
				   u32 resolved_size)
{
	u32 type_id = env->stack[--(env->top_stack)].type_id;
	struct btf *btf = env->btf;

	btf->resolved_sizes[type_id] = resolved_size;
	btf->resolved_ids[type_id] = resolved_type_id;
	env->visit_states[type_id] = RESOLVED;
}

static const struct resolve_vertex *env_stack_peak(struct btf_verifier_env *env)
{
	return env->top_stack ? &env->stack[env->top_stack - 1] : NULL;
}

/* Resolve the size of a passed-in "type"
 *
 * type: is an array (e.g. u32 array[x][y])
 * return type: type "u32[x][y]", i.e. BTF_KIND_ARRAY,
 * *type_size: (x * y * sizeof(u32)).  Hence, *type_size always
 *             corresponds to the return type.
 * *elem_type: u32
 * *total_nelems: (x * y).  Hence, individual elem size is
 *                (*type_size / *total_nelems)
 *
 * type: is not an array (e.g. const struct X)
 * return type: type "struct X"
 * *type_size: sizeof(struct X)
 * *elem_type: same as return type ("struct X")
 * *total_nelems: 1
 */
const struct btf_type *
btf_resolve_size(const struct btf *btf, const struct btf_type *type,
		 u32 *type_size, const struct btf_type **elem_type,
		 u32 *total_nelems)
{
	const struct btf_type *array_type = NULL;
	const struct btf_array *array;
	u32 i, size, nelems = 1;

	for (i = 0; i < MAX_RESOLVE_DEPTH; i++) {
		switch (BTF_INFO_KIND(type->info)) {
		/* type->size can be used */
		case BTF_KIND_INT:
		case BTF_KIND_STRUCT:
		case BTF_KIND_UNION:
		case BTF_KIND_ENUM:
			size = type->size;
			goto resolved;

		case BTF_KIND_PTR:
			size = sizeof(void *);
			goto resolved;

		/* Modifiers */
		case BTF_KIND_TYPEDEF:
		case BTF_KIND_VOLATILE:
		case BTF_KIND_CONST:
		case BTF_KIND_RESTRICT:
			type = btf_type_by_id(btf, type->type);
			break;

		case BTF_KIND_ARRAY:
			if (!array_type)
				array_type = type;
			array = btf_type_array(type);
			if (nelems && array->nelems > U32_MAX / nelems)
				return ERR_PTR(-EINVAL);
			nelems *= array->nelems;
			type = btf_type_by_id(btf, array->type);
			break;

		/* type without size */
		default:
			return ERR_PTR(-EINVAL);
		}
	}

	return ERR_PTR(-EINVAL);

resolved:
	if (nelems && size > U32_MAX / nelems)
		return ERR_PTR(-EINVAL);

	*type_size = nelems * size;
	if (total_nelems)
		*total_nelems = nelems;
	if (elem_type)
		*elem_type = type;

	return array_type ? : type;
}

/* The input param "type_id" must point to a needs_resolve type */
static const struct btf_type *btf_type_id_resolve(const struct btf *btf,
						  u32 *type_id)
{
	*type_id = btf->resolved_ids[*type_id];
	return btf_type_by_id(btf, *type_id);
}

const struct btf_type *btf_type_id_size(const struct btf *btf,
					u32 *type_id, u32 *ret_size)
{
	const struct btf_type *size_type;
	u32 size_type_id = *type_id;
	u32 size = 0;

	size_type = btf_type_by_id(btf, size_type_id);
	if (btf_type_nosize_or_null(size_type))
		return NULL;

	if (btf_type_has_size(size_type)) {
		size = size_type->size;
	} else if (btf_type_is_array(size_type)) {
		size = btf->resolved_sizes[size_type_id];
	} else if (btf_type_is_ptr(size_type)) {
		size = sizeof(void *);
	} else {
		if (WARN_ON_ONCE(!btf_type_is_modifier(size_type) &&
				 !btf_type_is_var(size_type)))
			return NULL;

		size_type_id = btf->resolved_ids[size_type_id];
		size_type = btf_type_by_id(btf, size_type_id);
		if (btf_type_nosize_or_null(size_type))
			return NULL;
		else if (btf_type_has_size(size_type))
			size = size_type->size;
		else if (btf_type_is_array(size_type))
			size = btf->resolved_sizes[size_type_id];
		else if (btf_type_is_ptr(size_type))
			size = sizeof(void *);
		else
			return NULL;
	}

	*type_id = size_type_id;
	if (ret_size)
		*ret_size = size;

	return size_type;
}

static int btf_df_check_member(struct btf_verifier_env *env,
			       const struct btf_type *struct_type,
			       const struct btf_member *member,
			       const struct btf_type *member_type)
{
	btf_verifier_log_basic(env, struct_type,
			       "Unsupported check_member");
	return -EINVAL;
}

static int btf_df_check_kflag_member(struct btf_verifier_env *env,
				     const struct btf_type *struct_type,
				     const struct btf_member *member,
				     const struct btf_type *member_type)
{
	btf_verifier_log_basic(env, struct_type,
			       "Unsupported check_kflag_member");
	return -EINVAL;
}

/* Used for ptr, array and struct/union type members.
 * int, enum and modifier types have their specific callback functions.
 */
static int btf_generic_check_kflag_member(struct btf_verifier_env *env,
					  const struct btf_type *struct_type,
					  const struct btf_member *member,
					  const struct btf_type *member_type)
{
	if (BTF_MEMBER_BITFIELD_SIZE(member->offset)) {
		btf_verifier_log_member(env, struct_type, member,
					"Invalid member bitfield_size");
		return -EINVAL;
	}

	/* bitfield size is 0, so member->offset represents bit offset only.
	 * It is safe to call non kflag check_member variants.
	 */
	return btf_type_ops(member_type)->check_member(env, struct_type,
						       member,
						       member_type);
}

static int btf_df_resolve(struct btf_verifier_env *env,
			  const struct resolve_vertex *v)
{
	btf_verifier_log_basic(env, v->t, "Unsupported resolve");
	return -EINVAL;
}

static void btf_df_seq_show(const struct btf *btf, const struct btf_type *t,
			    u32 type_id, void *data, u8 bits_offsets,
			    struct seq_file *m)
{
	seq_printf(m, "<unsupported kind:%u>", BTF_INFO_KIND(t->info));
}

static int btf_int_check_member(struct btf_verifier_env *env,
				const struct btf_type *struct_type,
				const struct btf_member *member,
				const struct btf_type *member_type)
{
	u32 int_data = btf_type_int(member_type);
	u32 struct_bits_off = member->offset;
	u32 struct_size = struct_type->size;
	u32 nr_copy_bits;
	u32 bytes_offset;

	if (U32_MAX - struct_bits_off < BTF_INT_OFFSET(int_data)) {
		btf_verifier_log_member(env, struct_type, member,
					"bits_offset exceeds U32_MAX");
		return -EINVAL;
	}

	struct_bits_off += BTF_INT_OFFSET(int_data);
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
	nr_copy_bits = BTF_INT_BITS(int_data) +
		BITS_PER_BYTE_MASKED(struct_bits_off);

	if (nr_copy_bits > BITS_PER_U128) {
		btf_verifier_log_member(env, struct_type, member,
					"nr_copy_bits exceeds 128");
		return -EINVAL;
	}

	if (struct_size < bytes_offset ||
	    struct_size - bytes_offset < BITS_ROUNDUP_BYTES(nr_copy_bits)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static int btf_int_check_kflag_member(struct btf_verifier_env *env,
				      const struct btf_type *struct_type,
				      const struct btf_member *member,
				      const struct btf_type *member_type)
{
	u32 struct_bits_off, nr_bits, nr_int_data_bits, bytes_offset;
	u32 int_data = btf_type_int(member_type);
	u32 struct_size = struct_type->size;
	u32 nr_copy_bits;

	/* a regular int type is required for the kflag int member */
	if (!btf_type_int_is_regular(member_type)) {
		btf_verifier_log_member(env, struct_type, member,
					"Invalid member base type");
		return -EINVAL;
	}

	/* check sanity of bitfield size */
	nr_bits = BTF_MEMBER_BITFIELD_SIZE(member->offset);
	struct_bits_off = BTF_MEMBER_BIT_OFFSET(member->offset);
	nr_int_data_bits = BTF_INT_BITS(int_data);
	if (!nr_bits) {
		/* Not a bitfield member, member offset must be at byte
		 * boundary.
		 */
		if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
			btf_verifier_log_member(env, struct_type, member,
						"Invalid member offset");
			return -EINVAL;
		}

		nr_bits = nr_int_data_bits;
	} else if (nr_bits > nr_int_data_bits) {
		btf_verifier_log_member(env, struct_type, member,
					"Invalid member bitfield_size");
		return -EINVAL;
	}

	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
	nr_copy_bits = nr_bits + BITS_PER_BYTE_MASKED(struct_bits_off);
	if (nr_copy_bits > BITS_PER_U128) {
		btf_verifier_log_member(env, struct_type, member,
					"nr_copy_bits exceeds 128");
		return -EINVAL;
	}

	if (struct_size < bytes_offset ||
	    struct_size - bytes_offset < BITS_ROUNDUP_BYTES(nr_copy_bits)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static s32 btf_int_check_meta(struct btf_verifier_env *env,
			      const struct btf_type *t,
			      u32 meta_left)
{
	u32 int_data, nr_bits, meta_needed = sizeof(int_data);
	u16 encoding;

	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	if (btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen != 0");
		return -EINVAL;
	}

	if (btf_type_kflag(t)) {
		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
		return -EINVAL;
	}

	int_data = btf_type_int(t);
	if (int_data & ~BTF_INT_MASK) {
		btf_verifier_log_basic(env, t, "Invalid int_data:%x",
				       int_data);
		return -EINVAL;
	}

	nr_bits = BTF_INT_BITS(int_data) + BTF_INT_OFFSET(int_data);

	if (nr_bits > BITS_PER_U128) {
		btf_verifier_log_type(env, t, "nr_bits exceeds %zu",
				      BITS_PER_U128);
		return -EINVAL;
	}

	if (BITS_ROUNDUP_BYTES(nr_bits) > t->size) {
		btf_verifier_log_type(env, t, "nr_bits exceeds type_size");
		return -EINVAL;
	}

	/*
	 * Only one of the encoding bits is allowed and it
	 * should be sufficient for the pretty print purpose (i.e. decoding).
	 * Multiple bits can be allowed later if it is found
	 * to be insufficient.
	 */
	encoding = BTF_INT_ENCODING(int_data);
	if (encoding &&
	    encoding != BTF_INT_SIGNED &&
	    encoding != BTF_INT_CHAR &&
	    encoding != BTF_INT_BOOL) {
		btf_verifier_log_type(env, t, "Unsupported encoding");
		return -ENOTSUPP;
	}

	btf_verifier_log_type(env, t, NULL);

	return meta_needed;
}

static void btf_int_log(struct btf_verifier_env *env,
			const struct btf_type *t)
{
	int int_data = btf_type_int(t);

	btf_verifier_log(env,
			 "size=%u bits_offset=%u nr_bits=%u encoding=%s",
			 t->size, BTF_INT_OFFSET(int_data),
			 BTF_INT_BITS(int_data),
			 btf_int_encoding_str(BTF_INT_ENCODING(int_data)));
}

static void btf_int128_print(struct seq_file *m, void *data)
{
	/* data points to a __int128 number.
	 * Suppose
	 *     int128_num = *(__int128 *)data;
	 * The below formulas shows what upper_num and lower_num represents:
	 *     upper_num = int128_num >> 64;
	 *     lower_num = int128_num & 0xffffffffFFFFFFFFULL;
	 */
	u64 upper_num, lower_num;

#ifdef __BIG_ENDIAN_BITFIELD
	upper_num = *(u64 *)data;
	lower_num = *(u64 *)(data + 8);
#else
	upper_num = *(u64 *)(data + 8);
	lower_num = *(u64 *)data;
#endif
	if (upper_num == 0)
		seq_printf(m, "0x%llx", lower_num);
	else
		seq_printf(m, "0x%llx%016llx", upper_num, lower_num);
}

static void btf_int128_shift(u64 *print_num, u16 left_shift_bits,
			     u16 right_shift_bits)
{
	u64 upper_num, lower_num;

#ifdef __BIG_ENDIAN_BITFIELD
	upper_num = print_num[0];
	lower_num = print_num[1];
#else
	upper_num = print_num[1];
	lower_num = print_num[0];
#endif

	/* shake out un-needed bits by shift/or operations */
	if (left_shift_bits >= 64) {
		upper_num = lower_num << (left_shift_bits - 64);
		lower_num = 0;
	} else {
		upper_num = (upper_num << left_shift_bits) |
			    (lower_num >> (64 - left_shift_bits));
		lower_num = lower_num << left_shift_bits;
	}

	if (right_shift_bits >= 64) {
		lower_num = upper_num >> (right_shift_bits - 64);
		upper_num = 0;
	} else {
		lower_num = (lower_num >> right_shift_bits) |
			    (upper_num << (64 - right_shift_bits));
		upper_num = upper_num >> right_shift_bits;
	}

#ifdef __BIG_ENDIAN_BITFIELD
	print_num[0] = upper_num;
	print_num[1] = lower_num;
#else
	print_num[0] = lower_num;
	print_num[1] = upper_num;
#endif
}

static void btf_bitfield_seq_show(void *data, u8 bits_offset,
				  u8 nr_bits, struct seq_file *m)
{
	u16 left_shift_bits, right_shift_bits;
	u8 nr_copy_bytes;
	u8 nr_copy_bits;
	u64 print_num[2] = {};

	nr_copy_bits = nr_bits + bits_offset;
	nr_copy_bytes = BITS_ROUNDUP_BYTES(nr_copy_bits);

	memcpy(print_num, data, nr_copy_bytes);

#ifdef __BIG_ENDIAN_BITFIELD
	left_shift_bits = bits_offset;
#else
	left_shift_bits = BITS_PER_U128 - nr_copy_bits;
#endif
	right_shift_bits = BITS_PER_U128 - nr_bits;

	btf_int128_shift(print_num, left_shift_bits, right_shift_bits);
	btf_int128_print(m, print_num);
}


static void btf_int_bits_seq_show(const struct btf *btf,
				  const struct btf_type *t,
				  void *data, u8 bits_offset,
				  struct seq_file *m)
{
	u32 int_data = btf_type_int(t);
	u8 nr_bits = BTF_INT_BITS(int_data);
	u8 total_bits_offset;

	/*
	 * bits_offset is at most 7.
	 * BTF_INT_OFFSET() cannot exceed 128 bits.
	 */
	total_bits_offset = bits_offset + BTF_INT_OFFSET(int_data);
	data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
	bits_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
	btf_bitfield_seq_show(data, bits_offset, nr_bits, m);
}

static void btf_int_seq_show(const struct btf *btf, const struct btf_type *t,
			     u32 type_id, void *data, u8 bits_offset,
			     struct seq_file *m)
{
	u32 int_data = btf_type_int(t);
	u8 encoding = BTF_INT_ENCODING(int_data);
	bool sign = encoding & BTF_INT_SIGNED;
	u8 nr_bits = BTF_INT_BITS(int_data);

	if (bits_offset || BTF_INT_OFFSET(int_data) ||
	    BITS_PER_BYTE_MASKED(nr_bits)) {
		btf_int_bits_seq_show(btf, t, data, bits_offset, m);
		return;
	}

	switch (nr_bits) {
	case 128:
		btf_int128_print(m, data);
		break;
	case 64:
		if (sign)
			seq_printf(m, "%lld", *(s64 *)data);
		else
			seq_printf(m, "%llu", *(u64 *)data);
		break;
	case 32:
		if (sign)
			seq_printf(m, "%d", *(s32 *)data);
		else
			seq_printf(m, "%u", *(u32 *)data);
		break;
	case 16:
		if (sign)
			seq_printf(m, "%d", *(s16 *)data);
		else
			seq_printf(m, "%u", *(u16 *)data);
		break;
	case 8:
		if (sign)
			seq_printf(m, "%d", *(s8 *)data);
		else
			seq_printf(m, "%u", *(u8 *)data);
		break;
	default:
		btf_int_bits_seq_show(btf, t, data, bits_offset, m);
	}
}

static const struct btf_kind_operations int_ops = {
	.check_meta = btf_int_check_meta,
	.resolve = btf_df_resolve,
	.check_member = btf_int_check_member,
	.check_kflag_member = btf_int_check_kflag_member,
	.log_details = btf_int_log,
	.seq_show = btf_int_seq_show,
};

static int btf_modifier_check_member(struct btf_verifier_env *env,
				     const struct btf_type *struct_type,
				     const struct btf_member *member,
				     const struct btf_type *member_type)
{
	const struct btf_type *resolved_type;
	u32 resolved_type_id = member->type;
	struct btf_member resolved_member;
	struct btf *btf = env->btf;

	resolved_type = btf_type_id_size(btf, &resolved_type_id, NULL);
	if (!resolved_type) {
		btf_verifier_log_member(env, struct_type, member,
					"Invalid member");
		return -EINVAL;
	}

	resolved_member = *member;
	resolved_member.type = resolved_type_id;

	return btf_type_ops(resolved_type)->check_member(env, struct_type,
							 &resolved_member,
							 resolved_type);
}

static int btf_modifier_check_kflag_member(struct btf_verifier_env *env,
					   const struct btf_type *struct_type,
					   const struct btf_member *member,
					   const struct btf_type *member_type)
{
	const struct btf_type *resolved_type;
	u32 resolved_type_id = member->type;
	struct btf_member resolved_member;
	struct btf *btf = env->btf;

	resolved_type = btf_type_id_size(btf, &resolved_type_id, NULL);
	if (!resolved_type) {
		btf_verifier_log_member(env, struct_type, member,
					"Invalid member");
		return -EINVAL;
	}

	resolved_member = *member;
	resolved_member.type = resolved_type_id;

	return btf_type_ops(resolved_type)->check_kflag_member(env, struct_type,
							       &resolved_member,
							       resolved_type);
}

static int btf_ptr_check_member(struct btf_verifier_env *env,
				const struct btf_type *struct_type,
				const struct btf_member *member,
				const struct btf_type *member_type)
{
	u32 struct_size, struct_bits_off, bytes_offset;

	struct_size = struct_type->size;
	struct_bits_off = member->offset;
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);

	if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member is not byte aligned");
		return -EINVAL;
	}

	if (struct_size - bytes_offset < sizeof(void *)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static int btf_ref_type_check_meta(struct btf_verifier_env *env,
				   const struct btf_type *t,
				   u32 meta_left)
{
	if (btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen != 0");
		return -EINVAL;
	}

	if (btf_type_kflag(t)) {
		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
		return -EINVAL;
	}

	if (!BTF_TYPE_ID_VALID(t->type)) {
		btf_verifier_log_type(env, t, "Invalid type_id");
		return -EINVAL;
	}

	/* typedef type must have a valid name, and other ref types,
	 * volatile, const, restrict, should have a null name.
	 */
	if (BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF) {
		if (!t->name_off ||
		    !btf_name_valid_identifier(env->btf, t->name_off)) {
			btf_verifier_log_type(env, t, "Invalid name");
			return -EINVAL;
		}
	} else {
		if (t->name_off) {
			btf_verifier_log_type(env, t, "Invalid name");
			return -EINVAL;
		}
	}

	btf_verifier_log_type(env, t, NULL);

	return 0;
}

static int btf_modifier_resolve(struct btf_verifier_env *env,
				const struct resolve_vertex *v)
{
	const struct btf_type *t = v->t;
	const struct btf_type *next_type;
	u32 next_type_id = t->type;
	struct btf *btf = env->btf;

	next_type = btf_type_by_id(btf, next_type_id);
	if (!next_type || btf_type_is_resolve_source_only(next_type)) {
		btf_verifier_log_type(env, v->t, "Invalid type_id");
		return -EINVAL;
	}

	if (!env_type_is_resolve_sink(env, next_type) &&
	    !env_type_is_resolved(env, next_type_id))
		return env_stack_push(env, next_type, next_type_id);

	/* Figure out the resolved next_type_id with size.
	 * They will be stored in the current modifier's
	 * resolved_ids and resolved_sizes such that it can
	 * save us a few type-following when we use it later (e.g. in
	 * pretty print).
	 */
	if (!btf_type_id_size(btf, &next_type_id, NULL)) {
		if (env_type_is_resolved(env, next_type_id))
			next_type = btf_type_id_resolve(btf, &next_type_id);

		/* "typedef void new_void", "const void"...etc */
		if (!btf_type_is_void(next_type) &&
		    !btf_type_is_fwd(next_type) &&
		    !btf_type_is_func_proto(next_type)) {
			btf_verifier_log_type(env, v->t, "Invalid type_id");
			return -EINVAL;
		}
	}

	env_stack_pop_resolved(env, next_type_id, 0);

	return 0;
}

static int btf_var_resolve(struct btf_verifier_env *env,
			   const struct resolve_vertex *v)
{
	const struct btf_type *next_type;
	const struct btf_type *t = v->t;
	u32 next_type_id = t->type;
	struct btf *btf = env->btf;

	next_type = btf_type_by_id(btf, next_type_id);
	if (!next_type || btf_type_is_resolve_source_only(next_type)) {
		btf_verifier_log_type(env, v->t, "Invalid type_id");
		return -EINVAL;
	}

	if (!env_type_is_resolve_sink(env, next_type) &&
	    !env_type_is_resolved(env, next_type_id))
		return env_stack_push(env, next_type, next_type_id);

	if (btf_type_is_modifier(next_type)) {
		const struct btf_type *resolved_type;
		u32 resolved_type_id;

		resolved_type_id = next_type_id;
		resolved_type = btf_type_id_resolve(btf, &resolved_type_id);

		if (btf_type_is_ptr(resolved_type) &&
		    !env_type_is_resolve_sink(env, resolved_type) &&
		    !env_type_is_resolved(env, resolved_type_id))
			return env_stack_push(env, resolved_type,
					      resolved_type_id);
	}

	/* We must resolve to something concrete at this point, no
	 * forward types or similar that would resolve to size of
	 * zero is allowed.
	 */
	if (!btf_type_id_size(btf, &next_type_id, NULL)) {
		btf_verifier_log_type(env, v->t, "Invalid type_id");
		return -EINVAL;
	}

	env_stack_pop_resolved(env, next_type_id, 0);

	return 0;
}

static int btf_ptr_resolve(struct btf_verifier_env *env,
			   const struct resolve_vertex *v)
{
	const struct btf_type *next_type;
	const struct btf_type *t = v->t;
	u32 next_type_id = t->type;
	struct btf *btf = env->btf;

	next_type = btf_type_by_id(btf, next_type_id);
	if (!next_type || btf_type_is_resolve_source_only(next_type)) {
		btf_verifier_log_type(env, v->t, "Invalid type_id");
		return -EINVAL;
	}

	if (!env_type_is_resolve_sink(env, next_type) &&
	    !env_type_is_resolved(env, next_type_id))
		return env_stack_push(env, next_type, next_type_id);

	/* If the modifier was RESOLVED during RESOLVE_STRUCT_OR_ARRAY,
	 * the modifier may have stopped resolving when it was resolved
	 * to a ptr (last-resolved-ptr).
	 *
	 * We now need to continue from the last-resolved-ptr to
	 * ensure the last-resolved-ptr will not referring back to
	 * the currenct ptr (t).
	 */
	if (btf_type_is_modifier(next_type)) {
		const struct btf_type *resolved_type;
		u32 resolved_type_id;

		resolved_type_id = next_type_id;
		resolved_type = btf_type_id_resolve(btf, &resolved_type_id);

		if (btf_type_is_ptr(resolved_type) &&
		    !env_type_is_resolve_sink(env, resolved_type) &&
		    !env_type_is_resolved(env, resolved_type_id))
			return env_stack_push(env, resolved_type,
					      resolved_type_id);
	}

	if (!btf_type_id_size(btf, &next_type_id, NULL)) {
		if (env_type_is_resolved(env, next_type_id))
			next_type = btf_type_id_resolve(btf, &next_type_id);

		if (!btf_type_is_void(next_type) &&
		    !btf_type_is_fwd(next_type) &&
		    !btf_type_is_func_proto(next_type)) {
			btf_verifier_log_type(env, v->t, "Invalid type_id");
			return -EINVAL;
		}
	}

	env_stack_pop_resolved(env, next_type_id, 0);

	return 0;
}

static void btf_modifier_seq_show(const struct btf *btf,
				  const struct btf_type *t,
				  u32 type_id, void *data,
				  u8 bits_offset, struct seq_file *m)
{
	if (btf->resolved_ids)
		t = btf_type_id_resolve(btf, &type_id);
	else
		t = btf_type_skip_modifiers(btf, type_id, NULL);

	btf_type_ops(t)->seq_show(btf, t, type_id, data, bits_offset, m);
}

static void btf_var_seq_show(const struct btf *btf, const struct btf_type *t,
			     u32 type_id, void *data, u8 bits_offset,
			     struct seq_file *m)
{
	t = btf_type_id_resolve(btf, &type_id);

	btf_type_ops(t)->seq_show(btf, t, type_id, data, bits_offset, m);
}

static void btf_ptr_seq_show(const struct btf *btf, const struct btf_type *t,
			     u32 type_id, void *data, u8 bits_offset,
			     struct seq_file *m)
{
	/* It is a hashed value */
	seq_printf(m, "%p", *(void **)data);
}

static void btf_ref_type_log(struct btf_verifier_env *env,
			     const struct btf_type *t)
{
	btf_verifier_log(env, "type_id=%u", t->type);
}

static struct btf_kind_operations modifier_ops = {
	.check_meta = btf_ref_type_check_meta,
	.resolve = btf_modifier_resolve,
	.check_member = btf_modifier_check_member,
	.check_kflag_member = btf_modifier_check_kflag_member,
	.log_details = btf_ref_type_log,
	.seq_show = btf_modifier_seq_show,
};

static struct btf_kind_operations ptr_ops = {
	.check_meta = btf_ref_type_check_meta,
	.resolve = btf_ptr_resolve,
	.check_member = btf_ptr_check_member,
	.check_kflag_member = btf_generic_check_kflag_member,
	.log_details = btf_ref_type_log,
	.seq_show = btf_ptr_seq_show,
};

static s32 btf_fwd_check_meta(struct btf_verifier_env *env,
			      const struct btf_type *t,
			      u32 meta_left)
{
	if (btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen != 0");
		return -EINVAL;
	}

	if (t->type) {
		btf_verifier_log_type(env, t, "type != 0");
		return -EINVAL;
	}

	/* fwd type must have a valid name */
	if (!t->name_off ||
	    !btf_name_valid_identifier(env->btf, t->name_off)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	return 0;
}

static void btf_fwd_type_log(struct btf_verifier_env *env,
			     const struct btf_type *t)
{
	btf_verifier_log(env, "%s", btf_type_kflag(t) ? "union" : "struct");
}

static struct btf_kind_operations fwd_ops = {
	.check_meta = btf_fwd_check_meta,
	.resolve = btf_df_resolve,
	.check_member = btf_df_check_member,
	.check_kflag_member = btf_df_check_kflag_member,
	.log_details = btf_fwd_type_log,
	.seq_show = btf_df_seq_show,
};

static int btf_array_check_member(struct btf_verifier_env *env,
				  const struct btf_type *struct_type,
				  const struct btf_member *member,
				  const struct btf_type *member_type)
{
	u32 struct_bits_off = member->offset;
	u32 struct_size, bytes_offset;
	u32 array_type_id, array_size;
	struct btf *btf = env->btf;

	if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member is not byte aligned");
		return -EINVAL;
	}

	array_type_id = member->type;
	btf_type_id_size(btf, &array_type_id, &array_size);
	struct_size = struct_type->size;
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
	if (struct_size - bytes_offset < array_size) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static s32 btf_array_check_meta(struct btf_verifier_env *env,
				const struct btf_type *t,
				u32 meta_left)
{
	const struct btf_array *array = btf_type_array(t);
	u32 meta_needed = sizeof(*array);

	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	/* array type should not have a name */
	if (t->name_off) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	if (btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen != 0");
		return -EINVAL;
	}

	if (btf_type_kflag(t)) {
		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
		return -EINVAL;
	}

	if (t->size) {
		btf_verifier_log_type(env, t, "size != 0");
		return -EINVAL;
	}

	/* Array elem type and index type cannot be in type void,
	 * so !array->type and !array->index_type are not allowed.
	 */
	if (!array->type || !BTF_TYPE_ID_VALID(array->type)) {
		btf_verifier_log_type(env, t, "Invalid elem");
		return -EINVAL;
	}

	if (!array->index_type || !BTF_TYPE_ID_VALID(array->index_type)) {
		btf_verifier_log_type(env, t, "Invalid index");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	return meta_needed;
}

static int btf_array_resolve(struct btf_verifier_env *env,
			     const struct resolve_vertex *v)
{
	const struct btf_array *array = btf_type_array(v->t);
	const struct btf_type *elem_type, *index_type;
	u32 elem_type_id, index_type_id;
	struct btf *btf = env->btf;
	u32 elem_size;

	/* Check array->index_type */
	index_type_id = array->index_type;
	index_type = btf_type_by_id(btf, index_type_id);
	if (btf_type_nosize_or_null(index_type) ||
	    btf_type_is_resolve_source_only(index_type)) {
		btf_verifier_log_type(env, v->t, "Invalid index");
		return -EINVAL;
	}

	if (!env_type_is_resolve_sink(env, index_type) &&
	    !env_type_is_resolved(env, index_type_id))
		return env_stack_push(env, index_type, index_type_id);

	index_type = btf_type_id_size(btf, &index_type_id, NULL);
	if (!index_type || !btf_type_is_int(index_type) ||
	    !btf_type_int_is_regular(index_type)) {
		btf_verifier_log_type(env, v->t, "Invalid index");
		return -EINVAL;
	}

	/* Check array->type */
	elem_type_id = array->type;
	elem_type = btf_type_by_id(btf, elem_type_id);
	if (btf_type_nosize_or_null(elem_type) ||
	    btf_type_is_resolve_source_only(elem_type)) {
		btf_verifier_log_type(env, v->t,
				      "Invalid elem");
		return -EINVAL;
	}

	if (!env_type_is_resolve_sink(env, elem_type) &&
	    !env_type_is_resolved(env, elem_type_id))
		return env_stack_push(env, elem_type, elem_type_id);

	elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
	if (!elem_type) {
		btf_verifier_log_type(env, v->t, "Invalid elem");
		return -EINVAL;
	}

	if (btf_type_is_int(elem_type) && !btf_type_int_is_regular(elem_type)) {
		btf_verifier_log_type(env, v->t, "Invalid array of int");
		return -EINVAL;
	}

	if (array->nelems && elem_size > U32_MAX / array->nelems) {
		btf_verifier_log_type(env, v->t,
				      "Array size overflows U32_MAX");
		return -EINVAL;
	}

	env_stack_pop_resolved(env, elem_type_id, elem_size * array->nelems);

	return 0;
}

static void btf_array_log(struct btf_verifier_env *env,
			  const struct btf_type *t)
{
	const struct btf_array *array = btf_type_array(t);

	btf_verifier_log(env, "type_id=%u index_type_id=%u nr_elems=%u",
			 array->type, array->index_type, array->nelems);
}

static void btf_array_seq_show(const struct btf *btf, const struct btf_type *t,
			       u32 type_id, void *data, u8 bits_offset,
			       struct seq_file *m)
{
	const struct btf_array *array = btf_type_array(t);
	const struct btf_kind_operations *elem_ops;
	const struct btf_type *elem_type;
	u32 i, elem_size, elem_type_id;

	elem_type_id = array->type;
	elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
	elem_ops = btf_type_ops(elem_type);
	seq_puts(m, "[");
	for (i = 0; i < array->nelems; i++) {
		if (i)
			seq_puts(m, ",");

		elem_ops->seq_show(btf, elem_type, elem_type_id, data,
				   bits_offset, m);
		data += elem_size;
	}
	seq_puts(m, "]");
}

static struct btf_kind_operations array_ops = {
	.check_meta = btf_array_check_meta,
	.resolve = btf_array_resolve,
	.check_member = btf_array_check_member,
	.check_kflag_member = btf_generic_check_kflag_member,
	.log_details = btf_array_log,
	.seq_show = btf_array_seq_show,
};

static int btf_struct_check_member(struct btf_verifier_env *env,
				   const struct btf_type *struct_type,
				   const struct btf_member *member,
				   const struct btf_type *member_type)
{
	u32 struct_bits_off = member->offset;
	u32 struct_size, bytes_offset;

	if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member is not byte aligned");
		return -EINVAL;
	}

	struct_size = struct_type->size;
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
	if (struct_size - bytes_offset < member_type->size) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static s32 btf_struct_check_meta(struct btf_verifier_env *env,
				 const struct btf_type *t,
				 u32 meta_left)
{
	bool is_union = BTF_INFO_KIND(t->info) == BTF_KIND_UNION;
	const struct btf_member *member;
	u32 meta_needed, last_offset;
	struct btf *btf = env->btf;
	u32 struct_size = t->size;
	u32 offset;
	u16 i;

	meta_needed = btf_type_vlen(t) * sizeof(*member);
	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	/* struct type either no name or a valid one */
	if (t->name_off &&
	    !btf_name_valid_identifier(env->btf, t->name_off)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	last_offset = 0;
	for_each_member(i, t, member) {
		if (!btf_name_offset_valid(btf, member->name_off)) {
			btf_verifier_log_member(env, t, member,
						"Invalid member name_offset:%u",
						member->name_off);
			return -EINVAL;
		}

		/* struct member either no name or a valid one */
		if (member->name_off &&
		    !btf_name_valid_identifier(btf, member->name_off)) {
			btf_verifier_log_member(env, t, member, "Invalid name");
			return -EINVAL;
		}
		/* A member cannot be in type void */
		if (!member->type || !BTF_TYPE_ID_VALID(member->type)) {
			btf_verifier_log_member(env, t, member,
						"Invalid type_id");
			return -EINVAL;
		}

		offset = btf_member_bit_offset(t, member);
		if (is_union && offset) {
			btf_verifier_log_member(env, t, member,
						"Invalid member bits_offset");
			return -EINVAL;
		}

		/*
		 * ">" instead of ">=" because the last member could be
		 * "char a[0];"
		 */
		if (last_offset > offset) {
			btf_verifier_log_member(env, t, member,
						"Invalid member bits_offset");
			return -EINVAL;
		}

		if (BITS_ROUNDUP_BYTES(offset) > struct_size) {
			btf_verifier_log_member(env, t, member,
						"Member bits_offset exceeds its struct size");
			return -EINVAL;
		}

		btf_verifier_log_member(env, t, member, NULL);
		last_offset = offset;
	}

	return meta_needed;
}

static int btf_struct_resolve(struct btf_verifier_env *env,
			      const struct resolve_vertex *v)
{
	const struct btf_member *member;
	int err;
	u16 i;

	/* Before continue resolving the next_member,
	 * ensure the last member is indeed resolved to a
	 * type with size info.
	 */
	if (v->next_member) {
		const struct btf_type *last_member_type;
		const struct btf_member *last_member;
		u16 last_member_type_id;

		last_member = btf_type_member(v->t) + v->next_member - 1;
		last_member_type_id = last_member->type;
		if (WARN_ON_ONCE(!env_type_is_resolved(env,
						       last_member_type_id)))
			return -EINVAL;

		last_member_type = btf_type_by_id(env->btf,
						  last_member_type_id);
		if (btf_type_kflag(v->t))
			err = btf_type_ops(last_member_type)->check_kflag_member(env, v->t,
								last_member,
								last_member_type);
		else
			err = btf_type_ops(last_member_type)->check_member(env, v->t,
								last_member,
								last_member_type);
		if (err)
			return err;
	}

	for_each_member_from(i, v->next_member, v->t, member) {
		u32 member_type_id = member->type;
		const struct btf_type *member_type = btf_type_by_id(env->btf,
								member_type_id);

		if (btf_type_nosize_or_null(member_type) ||
		    btf_type_is_resolve_source_only(member_type)) {
			btf_verifier_log_member(env, v->t, member,
						"Invalid member");
			return -EINVAL;
		}

		if (!env_type_is_resolve_sink(env, member_type) &&
		    !env_type_is_resolved(env, member_type_id)) {
			env_stack_set_next_member(env, i + 1);
			return env_stack_push(env, member_type, member_type_id);
		}

		if (btf_type_kflag(v->t))
			err = btf_type_ops(member_type)->check_kflag_member(env, v->t,
									    member,
									    member_type);
		else
			err = btf_type_ops(member_type)->check_member(env, v->t,
								      member,
								      member_type);
		if (err)
			return err;
	}

	env_stack_pop_resolved(env, 0, 0);

	return 0;
}

static void btf_struct_log(struct btf_verifier_env *env,
			   const struct btf_type *t)
{
	btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

/* find 'struct bpf_spin_lock' in map value.
 * return >= 0 offset if found
 * and < 0 in case of error
 */
int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t)
{
	const struct btf_member *member;
	u32 i, off = -ENOENT;

	if (!__btf_type_is_struct(t))
		return -EINVAL;

	for_each_member(i, t, member) {
		const struct btf_type *member_type = btf_type_by_id(btf,
								    member->type);
		if (!__btf_type_is_struct(member_type))
			continue;
		if (member_type->size != sizeof(struct bpf_spin_lock))
			continue;
		if (strcmp(__btf_name_by_offset(btf, member_type->name_off),
			   "bpf_spin_lock"))
			continue;
		if (off != -ENOENT)
			/* only one 'struct bpf_spin_lock' is allowed */
			return -E2BIG;
		off = btf_member_bit_offset(t, member);
		if (off % 8)
			/* valid C code cannot generate such BTF */
			return -EINVAL;
		off /= 8;
		if (off % __alignof__(struct bpf_spin_lock))
			/* valid struct bpf_spin_lock will be 4 byte aligned */
			return -EINVAL;
	}
	return off;
}

static void btf_struct_seq_show(const struct btf *btf, const struct btf_type *t,
				u32 type_id, void *data, u8 bits_offset,
				struct seq_file *m)
{
	const char *seq = BTF_INFO_KIND(t->info) == BTF_KIND_UNION ? "|" : ",";
	const struct btf_member *member;
	u32 i;

	seq_puts(m, "{");
	for_each_member(i, t, member) {
		const struct btf_type *member_type = btf_type_by_id(btf,
								member->type);
		const struct btf_kind_operations *ops;
		u32 member_offset, bitfield_size;
		u32 bytes_offset;
		u8 bits8_offset;

		if (i)
			seq_puts(m, seq);

		member_offset = btf_member_bit_offset(t, member);
		bitfield_size = btf_member_bitfield_size(t, member);
		bytes_offset = BITS_ROUNDDOWN_BYTES(member_offset);
		bits8_offset = BITS_PER_BYTE_MASKED(member_offset);
		if (bitfield_size) {
			btf_bitfield_seq_show(data + bytes_offset, bits8_offset,
					      bitfield_size, m);
		} else {
			ops = btf_type_ops(member_type);
			ops->seq_show(btf, member_type, member->type,
				      data + bytes_offset, bits8_offset, m);
		}
	}
	seq_puts(m, "}");
}

static struct btf_kind_operations struct_ops = {
	.check_meta = btf_struct_check_meta,
	.resolve = btf_struct_resolve,
	.check_member = btf_struct_check_member,
	.check_kflag_member = btf_generic_check_kflag_member,
	.log_details = btf_struct_log,
	.seq_show = btf_struct_seq_show,
};

static int btf_enum_check_member(struct btf_verifier_env *env,
				 const struct btf_type *struct_type,
				 const struct btf_member *member,
				 const struct btf_type *member_type)
{
	u32 struct_bits_off = member->offset;
	u32 struct_size, bytes_offset;

	if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member is not byte aligned");
		return -EINVAL;
	}

	struct_size = struct_type->size;
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
	if (struct_size - bytes_offset < sizeof(int)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static int btf_enum_check_kflag_member(struct btf_verifier_env *env,
				       const struct btf_type *struct_type,
				       const struct btf_member *member,
				       const struct btf_type *member_type)
{
	u32 struct_bits_off, nr_bits, bytes_end, struct_size;
	u32 int_bitsize = sizeof(int) * BITS_PER_BYTE;

	struct_bits_off = BTF_MEMBER_BIT_OFFSET(member->offset);
	nr_bits = BTF_MEMBER_BITFIELD_SIZE(member->offset);
	if (!nr_bits) {
		if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
			btf_verifier_log_member(env, struct_type, member,
						"Member is not byte aligned");
			return -EINVAL;
		}

		nr_bits = int_bitsize;
	} else if (nr_bits > int_bitsize) {
		btf_verifier_log_member(env, struct_type, member,
					"Invalid member bitfield_size");
		return -EINVAL;
	}

	struct_size = struct_type->size;
	bytes_end = BITS_ROUNDUP_BYTES(struct_bits_off + nr_bits);
	if (struct_size < bytes_end) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static s32 btf_enum_check_meta(struct btf_verifier_env *env,
			       const struct btf_type *t,
			       u32 meta_left)
{
	const struct btf_enum *enums = btf_type_enum(t);
	struct btf *btf = env->btf;
	u16 i, nr_enums;
	u32 meta_needed;

	nr_enums = btf_type_vlen(t);
	meta_needed = nr_enums * sizeof(*enums);

	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	if (btf_type_kflag(t)) {
		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
		return -EINVAL;
	}

	if (t->size > 8 || !is_power_of_2(t->size)) {
		btf_verifier_log_type(env, t, "Unexpected size");
		return -EINVAL;
	}

	/* enum type either no name or a valid one */
	if (t->name_off &&
	    !btf_name_valid_identifier(env->btf, t->name_off)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	for (i = 0; i < nr_enums; i++) {
		if (!btf_name_offset_valid(btf, enums[i].name_off)) {
			btf_verifier_log(env, "\tInvalid name_offset:%u",
					 enums[i].name_off);
			return -EINVAL;
		}

		/* enum member must have a valid name */
		if (!enums[i].name_off ||
		    !btf_name_valid_identifier(btf, enums[i].name_off)) {
			btf_verifier_log_type(env, t, "Invalid name");
			return -EINVAL;
		}

		if (env->log.level == BPF_LOG_KERNEL)
			continue;
		btf_verifier_log(env, "\t%s val=%d\n",
				 __btf_name_by_offset(btf, enums[i].name_off),
				 enums[i].val);
	}

	return meta_needed;
}

static void btf_enum_log(struct btf_verifier_env *env,
			 const struct btf_type *t)
{
	btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

static void btf_enum_seq_show(const struct btf *btf, const struct btf_type *t,
			      u32 type_id, void *data, u8 bits_offset,
			      struct seq_file *m)
{
	const struct btf_enum *enums = btf_type_enum(t);
	u32 i, nr_enums = btf_type_vlen(t);
	int v = *(int *)data;

	for (i = 0; i < nr_enums; i++) {
		if (v == enums[i].val) {
			seq_printf(m, "%s",
				   __btf_name_by_offset(btf,
							enums[i].name_off));
			return;
		}
	}

	seq_printf(m, "%d", v);
}

static struct btf_kind_operations enum_ops = {
	.check_meta = btf_enum_check_meta,
	.resolve = btf_df_resolve,
	.check_member = btf_enum_check_member,
	.check_kflag_member = btf_enum_check_kflag_member,
	.log_details = btf_enum_log,
	.seq_show = btf_enum_seq_show,
};

static s32 btf_func_proto_check_meta(struct btf_verifier_env *env,
				     const struct btf_type *t,
				     u32 meta_left)
{
	u32 meta_needed = btf_type_vlen(t) * sizeof(struct btf_param);

	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	if (t->name_off) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	if (btf_type_kflag(t)) {
		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	return meta_needed;
}

static void btf_func_proto_log(struct btf_verifier_env *env,
			       const struct btf_type *t)
{
	const struct btf_param *args = (const struct btf_param *)(t + 1);
	u16 nr_args = btf_type_vlen(t), i;

	btf_verifier_log(env, "return=%u args=(", t->type);
	if (!nr_args) {
		btf_verifier_log(env, "void");
		goto done;
	}

	if (nr_args == 1 && !args[0].type) {
		/* Only one vararg */
		btf_verifier_log(env, "vararg");
		goto done;
	}

	btf_verifier_log(env, "%u %s", args[0].type,
			 __btf_name_by_offset(env->btf,
					      args[0].name_off));
	for (i = 1; i < nr_args - 1; i++)
		btf_verifier_log(env, ", %u %s", args[i].type,
				 __btf_name_by_offset(env->btf,
						      args[i].name_off));

	if (nr_args > 1) {
		const struct btf_param *last_arg = &args[nr_args - 1];

		if (last_arg->type)
			btf_verifier_log(env, ", %u %s", last_arg->type,
					 __btf_name_by_offset(env->btf,
							      last_arg->name_off));
		else
			btf_verifier_log(env, ", vararg");
	}

done:
	btf_verifier_log(env, ")");
}

static struct btf_kind_operations func_proto_ops = {
	.check_meta = btf_func_proto_check_meta,
	.resolve = btf_df_resolve,
	/*
	 * BTF_KIND_FUNC_PROTO cannot be directly referred by
	 * a struct's member.
	 *
	 * It should be a funciton pointer instead.
	 * (i.e. struct's member -> BTF_KIND_PTR -> BTF_KIND_FUNC_PROTO)
	 *
	 * Hence, there is no btf_func_check_member().
	 */
	.check_member = btf_df_check_member,
	.check_kflag_member = btf_df_check_kflag_member,
	.log_details = btf_func_proto_log,
	.seq_show = btf_df_seq_show,
};

static s32 btf_func_check_meta(struct btf_verifier_env *env,
			       const struct btf_type *t,
			       u32 meta_left)
{
	if (!t->name_off ||
	    !btf_name_valid_identifier(env->btf, t->name_off)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	if (btf_type_vlen(t) > BTF_FUNC_GLOBAL) {
		btf_verifier_log_type(env, t, "Invalid func linkage");
		return -EINVAL;
	}

	if (btf_type_kflag(t)) {
		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	return 0;
}

static struct btf_kind_operations func_ops = {
	.check_meta = btf_func_check_meta,
	.resolve = btf_df_resolve,
	.check_member = btf_df_check_member,
	.check_kflag_member = btf_df_check_kflag_member,
	.log_details = btf_ref_type_log,
	.seq_show = btf_df_seq_show,
};

static s32 btf_var_check_meta(struct btf_verifier_env *env,
			      const struct btf_type *t,
			      u32 meta_left)
{
	const struct btf_var *var;
	u32 meta_needed = sizeof(*var);

	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	if (btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen != 0");
		return -EINVAL;
	}

	if (btf_type_kflag(t)) {
		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
		return -EINVAL;
	}

	if (!t->name_off ||
	    !__btf_name_valid(env->btf, t->name_off, true)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	/* A var cannot be in type void */
	if (!t->type || !BTF_TYPE_ID_VALID(t->type)) {
		btf_verifier_log_type(env, t, "Invalid type_id");
		return -EINVAL;
	}

	var = btf_type_var(t);
	if (var->linkage != BTF_VAR_STATIC &&
	    var->linkage != BTF_VAR_GLOBAL_ALLOCATED) {
		btf_verifier_log_type(env, t, "Linkage not supported");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	return meta_needed;
}

static void btf_var_log(struct btf_verifier_env *env, const struct btf_type *t)
{
	const struct btf_var *var = btf_type_var(t);

	btf_verifier_log(env, "type_id=%u linkage=%u", t->type, var->linkage);
}

static const struct btf_kind_operations var_ops = {
	.check_meta		= btf_var_check_meta,
	.resolve		= btf_var_resolve,
	.check_member		= btf_df_check_member,
	.check_kflag_member	= btf_df_check_kflag_member,
	.log_details		= btf_var_log,
	.seq_show		= btf_var_seq_show,
};

static s32 btf_datasec_check_meta(struct btf_verifier_env *env,
				  const struct btf_type *t,
				  u32 meta_left)
{
	const struct btf_var_secinfo *vsi;
	u64 last_vsi_end_off = 0, sum = 0;
	u32 i, meta_needed;

	meta_needed = btf_type_vlen(t) * sizeof(*vsi);
	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	if (!btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen == 0");
		return -EINVAL;
	}

	if (!t->size) {
		btf_verifier_log_type(env, t, "size == 0");
		return -EINVAL;
	}

	if (btf_type_kflag(t)) {
		btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
		return -EINVAL;
	}

	if (!t->name_off ||
	    !btf_name_valid_section(env->btf, t->name_off)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	for_each_vsi(i, t, vsi) {
		/* A var cannot be in type void */
		if (!vsi->type || !BTF_TYPE_ID_VALID(vsi->type)) {
			btf_verifier_log_vsi(env, t, vsi,
					     "Invalid type_id");
			return -EINVAL;
		}

		if (vsi->offset < last_vsi_end_off || vsi->offset >= t->size) {
			btf_verifier_log_vsi(env, t, vsi,
					     "Invalid offset");
			return -EINVAL;
		}

		if (!vsi->size || vsi->size > t->size) {
			btf_verifier_log_vsi(env, t, vsi,
					     "Invalid size");
			return -EINVAL;
		}

		last_vsi_end_off = vsi->offset + vsi->size;
		if (last_vsi_end_off > t->size) {
			btf_verifier_log_vsi(env, t, vsi,
					     "Invalid offset+size");
			return -EINVAL;
		}

		btf_verifier_log_vsi(env, t, vsi, NULL);
		sum += vsi->size;
	}

	if (t->size < sum) {
		btf_verifier_log_type(env, t, "Invalid btf_info size");
		return -EINVAL;
	}

	return meta_needed;
}

static int btf_datasec_resolve(struct btf_verifier_env *env,
			       const struct resolve_vertex *v)
{
	const struct btf_var_secinfo *vsi;
	struct btf *btf = env->btf;
	u16 i;

	for_each_vsi_from(i, v->next_member, v->t, vsi) {
		u32 var_type_id = vsi->type, type_id, type_size = 0;
		const struct btf_type *var_type = btf_type_by_id(env->btf,
								 var_type_id);
		if (!var_type || !btf_type_is_var(var_type)) {
			btf_verifier_log_vsi(env, v->t, vsi,
					     "Not a VAR kind member");
			return -EINVAL;
		}

		if (!env_type_is_resolve_sink(env, var_type) &&
		    !env_type_is_resolved(env, var_type_id)) {
			env_stack_set_next_member(env, i + 1);
			return env_stack_push(env, var_type, var_type_id);
		}

		type_id = var_type->type;
		if (!btf_type_id_size(btf, &type_id, &type_size)) {
			btf_verifier_log_vsi(env, v->t, vsi, "Invalid type");
			return -EINVAL;
		}

		if (vsi->size < type_size) {
			btf_verifier_log_vsi(env, v->t, vsi, "Invalid size");
			return -EINVAL;
		}
	}

	env_stack_pop_resolved(env, 0, 0);
	return 0;
}

static void btf_datasec_log(struct btf_verifier_env *env,
			    const struct btf_type *t)
{
	btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

static void btf_datasec_seq_show(const struct btf *btf,
				 const struct btf_type *t, u32 type_id,
				 void *data, u8 bits_offset,
				 struct seq_file *m)
{
	const struct btf_var_secinfo *vsi;
	const struct btf_type *var;
	u32 i;

	seq_printf(m, "section (\"%s\") = {", __btf_name_by_offset(btf, t->name_off));
	for_each_vsi(i, t, vsi) {
		var = btf_type_by_id(btf, vsi->type);
		if (i)
			seq_puts(m, ",");
		btf_type_ops(var)->seq_show(btf, var, vsi->type,
					    data + vsi->offset, bits_offset, m);
	}
	seq_puts(m, "}");
}

static const struct btf_kind_operations datasec_ops = {
	.check_meta		= btf_datasec_check_meta,
	.resolve		= btf_datasec_resolve,
	.check_member		= btf_df_check_member,
	.check_kflag_member	= btf_df_check_kflag_member,
	.log_details		= btf_datasec_log,
	.seq_show		= btf_datasec_seq_show,
};

static int btf_func_proto_check(struct btf_verifier_env *env,
				const struct btf_type *t)
{
	const struct btf_type *ret_type;
	const struct btf_param *args;
	const struct btf *btf;
	u16 nr_args, i;
	int err;

	btf = env->btf;
	args = (const struct btf_param *)(t + 1);
	nr_args = btf_type_vlen(t);

	/* Check func return type which could be "void" (t->type == 0) */
	if (t->type) {
		u32 ret_type_id = t->type;

		ret_type = btf_type_by_id(btf, ret_type_id);
		if (!ret_type) {
			btf_verifier_log_type(env, t, "Invalid return type");
			return -EINVAL;
		}

		if (btf_type_needs_resolve(ret_type) &&
		    !env_type_is_resolved(env, ret_type_id)) {
			err = btf_resolve(env, ret_type, ret_type_id);
			if (err)
				return err;
		}

		/* Ensure the return type is a type that has a size */
		if (!btf_type_id_size(btf, &ret_type_id, NULL)) {
			btf_verifier_log_type(env, t, "Invalid return type");
			return -EINVAL;
		}
	}

	if (!nr_args)
		return 0;

	/* Last func arg type_id could be 0 if it is a vararg */
	if (!args[nr_args - 1].type) {
		if (args[nr_args - 1].name_off) {
			btf_verifier_log_type(env, t, "Invalid arg#%u",
					      nr_args);
			return -EINVAL;
		}
		nr_args--;
	}

	err = 0;
	for (i = 0; i < nr_args; i++) {
		const struct btf_type *arg_type;
		u32 arg_type_id;

		arg_type_id = args[i].type;
		arg_type = btf_type_by_id(btf, arg_type_id);
		if (!arg_type) {
			btf_verifier_log_type(env, t, "Invalid arg#%u", i + 1);
			err = -EINVAL;
			break;
		}

		if (args[i].name_off &&
		    (!btf_name_offset_valid(btf, args[i].name_off) ||
		     !btf_name_valid_identifier(btf, args[i].name_off))) {
			btf_verifier_log_type(env, t,
					      "Invalid arg#%u", i + 1);
			err = -EINVAL;
			break;
		}

		if (btf_type_needs_resolve(arg_type) &&
		    !env_type_is_resolved(env, arg_type_id)) {
			err = btf_resolve(env, arg_type, arg_type_id);
			if (err)
				break;
		}

		if (!btf_type_id_size(btf, &arg_type_id, NULL)) {
			btf_verifier_log_type(env, t, "Invalid arg#%u", i + 1);
			err = -EINVAL;
			break;
		}
	}

	return err;
}

static int btf_func_check(struct btf_verifier_env *env,
			  const struct btf_type *t)
{
	const struct btf_type *proto_type;
	const struct btf_param *args;
	const struct btf *btf;
	u16 nr_args, i;

	btf = env->btf;
	proto_type = btf_type_by_id(btf, t->type);

	if (!proto_type || !btf_type_is_func_proto(proto_type)) {
		btf_verifier_log_type(env, t, "Invalid type_id");
		return -EINVAL;
	}

	args = (const struct btf_param *)(proto_type + 1);
	nr_args = btf_type_vlen(proto_type);
	for (i = 0; i < nr_args; i++) {
		if (!args[i].name_off && args[i].type) {
			btf_verifier_log_type(env, t, "Invalid arg#%u", i + 1);
			return -EINVAL;
		}
	}

	return 0;
}

static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS] = {
	[BTF_KIND_INT] = &int_ops,
	[BTF_KIND_PTR] = &ptr_ops,
	[BTF_KIND_ARRAY] = &array_ops,
	[BTF_KIND_STRUCT] = &struct_ops,
	[BTF_KIND_UNION] = &struct_ops,
	[BTF_KIND_ENUM] = &enum_ops,
	[BTF_KIND_FWD] = &fwd_ops,
	[BTF_KIND_TYPEDEF] = &modifier_ops,
	[BTF_KIND_VOLATILE] = &modifier_ops,
	[BTF_KIND_CONST] = &modifier_ops,
	[BTF_KIND_RESTRICT] = &modifier_ops,
	[BTF_KIND_FUNC] = &func_ops,
	[BTF_KIND_FUNC_PROTO] = &func_proto_ops,
	[BTF_KIND_VAR] = &var_ops,
	[BTF_KIND_DATASEC] = &datasec_ops,
};

static s32 btf_check_meta(struct btf_verifier_env *env,
			  const struct btf_type *t,
			  u32 meta_left)
{
	u32 saved_meta_left = meta_left;
	s32 var_meta_size;

	if (meta_left < sizeof(*t)) {
		btf_verifier_log(env, "[%u] meta_left:%u meta_needed:%zu",
				 env->log_type_id, meta_left, sizeof(*t));
		return -EINVAL;
	}
	meta_left -= sizeof(*t);

	if (t->info & ~BTF_INFO_MASK) {
		btf_verifier_log(env, "[%u] Invalid btf_info:%x",
				 env->log_type_id, t->info);
		return -EINVAL;
	}

	if (BTF_INFO_KIND(t->info) > BTF_KIND_MAX ||
	    BTF_INFO_KIND(t->info) == BTF_KIND_UNKN) {
		btf_verifier_log(env, "[%u] Invalid kind:%u",
				 env->log_type_id, BTF_INFO_KIND(t->info));
		return -EINVAL;
	}

	if (!btf_name_offset_valid(env->btf, t->name_off)) {
		btf_verifier_log(env, "[%u] Invalid name_offset:%u",
				 env->log_type_id, t->name_off);
		return -EINVAL;
	}

	var_meta_size = btf_type_ops(t)->check_meta(env, t, meta_left);
	if (var_meta_size < 0)
		return var_meta_size;

	meta_left -= var_meta_size;

	return saved_meta_left - meta_left;
}

static int btf_check_all_metas(struct btf_verifier_env *env)
{
	struct btf *btf = env->btf;
	struct btf_header *hdr;
	void *cur, *end;

	hdr = &btf->hdr;
	cur = btf->nohdr_data + hdr->type_off;
	end = cur + hdr->type_len;

	env->log_type_id = 1;
	while (cur < end) {
		struct btf_type *t = cur;
		s32 meta_size;

		meta_size = btf_check_meta(env, t, end - cur);
		if (meta_size < 0)
			return meta_size;

		btf_add_type(env, t);
		cur += meta_size;
		env->log_type_id++;
	}

	return 0;
}

static bool btf_resolve_valid(struct btf_verifier_env *env,
			      const struct btf_type *t,
			      u32 type_id)
{
	struct btf *btf = env->btf;

	if (!env_type_is_resolved(env, type_id))
		return false;

	if (btf_type_is_struct(t) || btf_type_is_datasec(t))
		return !btf->resolved_ids[type_id] &&
		       !btf->resolved_sizes[type_id];

	if (btf_type_is_modifier(t) || btf_type_is_ptr(t) ||
	    btf_type_is_var(t)) {
		t = btf_type_id_resolve(btf, &type_id);
		return t &&
		       !btf_type_is_modifier(t) &&
		       !btf_type_is_var(t) &&
		       !btf_type_is_datasec(t);
	}

	if (btf_type_is_array(t)) {
		const struct btf_array *array = btf_type_array(t);
		const struct btf_type *elem_type;
		u32 elem_type_id = array->type;
		u32 elem_size;

		elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
		return elem_type && !btf_type_is_modifier(elem_type) &&
			(array->nelems * elem_size ==
			 btf->resolved_sizes[type_id]);
	}

	return false;
}

static int btf_resolve(struct btf_verifier_env *env,
		       const struct btf_type *t, u32 type_id)
{
	u32 save_log_type_id = env->log_type_id;
	const struct resolve_vertex *v;
	int err = 0;

	env->resolve_mode = RESOLVE_TBD;
	env_stack_push(env, t, type_id);
	while (!err && (v = env_stack_peak(env))) {
		env->log_type_id = v->type_id;
		err = btf_type_ops(v->t)->resolve(env, v);
	}

	env->log_type_id = type_id;
	if (err == -E2BIG) {
		btf_verifier_log_type(env, t,
				      "Exceeded max resolving depth:%u",
				      MAX_RESOLVE_DEPTH);
	} else if (err == -EEXIST) {
		btf_verifier_log_type(env, t, "Loop detected");
	}

	/* Final sanity check */
	if (!err && !btf_resolve_valid(env, t, type_id)) {
		btf_verifier_log_type(env, t, "Invalid resolve state");
		err = -EINVAL;
	}

	env->log_type_id = save_log_type_id;
	return err;
}

static int btf_check_all_types(struct btf_verifier_env *env)
{
	struct btf *btf = env->btf;
	u32 type_id;
	int err;

	err = env_resolve_init(env);
	if (err)
		return err;

	env->phase++;
	for (type_id = 1; type_id <= btf->nr_types; type_id++) {
		const struct btf_type *t = btf_type_by_id(btf, type_id);

		env->log_type_id = type_id;
		if (btf_type_needs_resolve(t) &&
		    !env_type_is_resolved(env, type_id)) {
			err = btf_resolve(env, t, type_id);
			if (err)
				return err;
		}

		if (btf_type_is_func_proto(t)) {
			err = btf_func_proto_check(env, t);
			if (err)
				return err;
		}

		if (btf_type_is_func(t)) {
			err = btf_func_check(env, t);
			if (err)
				return err;
		}
	}

	return 0;
}

static int btf_parse_type_sec(struct btf_verifier_env *env)
{
	const struct btf_header *hdr = &env->btf->hdr;
	int err;

	/* Type section must align to 4 bytes */
	if (hdr->type_off & (sizeof(u32) - 1)) {
		btf_verifier_log(env, "Unaligned type_off");
		return -EINVAL;
	}

	if (!hdr->type_len) {
		btf_verifier_log(env, "No type found");
		return -EINVAL;
	}

	err = btf_check_all_metas(env);
	if (err)
		return err;

	return btf_check_all_types(env);
}

static int btf_parse_str_sec(struct btf_verifier_env *env)
{
	const struct btf_header *hdr;
	struct btf *btf = env->btf;
	const char *start, *end;

	hdr = &btf->hdr;
	start = btf->nohdr_data + hdr->str_off;
	end = start + hdr->str_len;

	if (end != btf->data + btf->data_size) {
		btf_verifier_log(env, "String section is not at the end");
		return -EINVAL;
	}

	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET ||
	    start[0] || end[-1]) {
		btf_verifier_log(env, "Invalid string section");
		return -EINVAL;
	}

	btf->strings = start;

	return 0;
}

static const size_t btf_sec_info_offset[] = {
	offsetof(struct btf_header, type_off),
	offsetof(struct btf_header, str_off),
};

static int btf_sec_info_cmp(const void *a, const void *b)
{
	const struct btf_sec_info *x = a;
	const struct btf_sec_info *y = b;

	return (int)(x->off - y->off) ? : (int)(x->len - y->len);
}

static int btf_check_sec_info(struct btf_verifier_env *env,
			      u32 btf_data_size)
{
	struct btf_sec_info secs[ARRAY_SIZE(btf_sec_info_offset)];
	u32 total, expected_total, i;
	const struct btf_header *hdr;
	const struct btf *btf;

	btf = env->btf;
	hdr = &btf->hdr;

	/* Populate the secs from hdr */
	for (i = 0; i < ARRAY_SIZE(btf_sec_info_offset); i++)
		secs[i] = *(struct btf_sec_info *)((void *)hdr +
						   btf_sec_info_offset[i]);

	sort(secs, ARRAY_SIZE(btf_sec_info_offset),
	     sizeof(struct btf_sec_info), btf_sec_info_cmp, NULL);

	/* Check for gaps and overlap among sections */
	total = 0;
	expected_total = btf_data_size - hdr->hdr_len;
	for (i = 0; i < ARRAY_SIZE(btf_sec_info_offset); i++) {
		if (expected_total < secs[i].off) {
			btf_verifier_log(env, "Invalid section offset");
			return -EINVAL;
		}
		if (total < secs[i].off) {
			/* gap */
			btf_verifier_log(env, "Unsupported section found");
			return -EINVAL;
		}
		if (total > secs[i].off) {
			btf_verifier_log(env, "Section overlap found");
			return -EINVAL;
		}
		if (expected_total - total < secs[i].len) {
			btf_verifier_log(env,
					 "Total section length too long");
			return -EINVAL;
		}
		total += secs[i].len;
	}

	/* There is data other than hdr and known sections */
	if (expected_total != total) {
		btf_verifier_log(env, "Unsupported section found");
		return -EINVAL;
	}

	return 0;
}

static int btf_parse_hdr(struct btf_verifier_env *env)
{
	u32 hdr_len, hdr_copy, btf_data_size;
	const struct btf_header *hdr;
	struct btf *btf;
	int err;

	btf = env->btf;
	btf_data_size = btf->data_size;

	if (btf_data_size <
	    offsetof(struct btf_header, hdr_len) + sizeof(hdr->hdr_len)) {
		btf_verifier_log(env, "hdr_len not found");
		return -EINVAL;
	}

	hdr = btf->data;
	hdr_len = hdr->hdr_len;
	if (btf_data_size < hdr_len) {
		btf_verifier_log(env, "btf_header not found");
		return -EINVAL;
	}

	/* Ensure the unsupported header fields are zero */
	if (hdr_len > sizeof(btf->hdr)) {
		u8 *expected_zero = btf->data + sizeof(btf->hdr);
		u8 *end = btf->data + hdr_len;

		for (; expected_zero < end; expected_zero++) {
			if (*expected_zero) {
				btf_verifier_log(env, "Unsupported btf_header");
				return -E2BIG;
			}
		}
	}

	hdr_copy = min_t(u32, hdr_len, sizeof(btf->hdr));
	memcpy(&btf->hdr, btf->data, hdr_copy);

	hdr = &btf->hdr;

	btf_verifier_log_hdr(env, btf_data_size);

	if (hdr->magic != BTF_MAGIC) {
		btf_verifier_log(env, "Invalid magic");
		return -EINVAL;
	}

	if (hdr->version != BTF_VERSION) {
		btf_verifier_log(env, "Unsupported version");
		return -ENOTSUPP;
	}

	if (hdr->flags) {
		btf_verifier_log(env, "Unsupported flags");
		return -ENOTSUPP;
	}

	if (btf_data_size == hdr->hdr_len) {
		btf_verifier_log(env, "No data");
		return -EINVAL;
	}

	err = btf_check_sec_info(env, btf_data_size);
	if (err)
		return err;

	return 0;
}

static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size,
			     u32 log_level, char __user *log_ubuf, u32 log_size)
{
	struct btf_verifier_env *env = NULL;
	struct bpf_verifier_log *log;
	struct btf *btf = NULL;
	u8 *data;
	int err;

	if (btf_data_size > BTF_MAX_SIZE)
		return ERR_PTR(-E2BIG);

	env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
	if (!env)
		return ERR_PTR(-ENOMEM);

	log = &env->log;
	if (log_level || log_ubuf || log_size) {
		/* user requested verbose verifier output
		 * and supplied buffer to store the verification trace
		 */
		log->level = log_level;
		log->ubuf = log_ubuf;
		log->len_total = log_size;

		/* log attributes have to be sane */
		if (log->len_total < 128 || log->len_total > UINT_MAX >> 8 ||
		    !log->level || !log->ubuf) {
			err = -EINVAL;
			goto errout;
		}
	}

	btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
	if (!btf) {
		err = -ENOMEM;
		goto errout;
	}
	env->btf = btf;

	data = kvmalloc(btf_data_size, GFP_KERNEL | __GFP_NOWARN);
	if (!data) {
		err = -ENOMEM;
		goto errout;
	}

	btf->data = data;
	btf->data_size = btf_data_size;

	if (copy_from_user(data, btf_data, btf_data_size)) {
		err = -EFAULT;
		goto errout;
	}

	err = btf_parse_hdr(env);
	if (err)
		goto errout;

	btf->nohdr_data = btf->data + btf->hdr.hdr_len;

	err = btf_parse_str_sec(env);
	if (err)
		goto errout;

	err = btf_parse_type_sec(env);
	if (err)
		goto errout;

	if (log->level && bpf_verifier_log_full(log)) {
		err = -ENOSPC;
		goto errout;
	}

	btf_verifier_env_free(env);
	refcount_set(&btf->refcnt, 1);
	return btf;

errout:
	btf_verifier_env_free(env);
	if (btf)
		btf_free(btf);
	return ERR_PTR(err);
}

extern char __weak _binary__btf_vmlinux_bin_start[];
extern char __weak _binary__btf_vmlinux_bin_end[];
extern struct btf *btf_vmlinux;

#define BPF_MAP_TYPE(_id, _ops)
static union {
	struct bpf_ctx_convert {
#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \
	prog_ctx_type _id##_prog; \
	kern_ctx_type _id##_kern;
#include <linux/bpf_types.h>
#undef BPF_PROG_TYPE
	} *__t;
	/* 't' is written once under lock. Read many times. */
	const struct btf_type *t;
} bpf_ctx_convert;
enum {
#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \
	__ctx_convert##_id,
#include <linux/bpf_types.h>
#undef BPF_PROG_TYPE
	__ctx_convert_unused, /* to avoid empty enum in extreme .config */
};
static u8 bpf_ctx_convert_map[] = {
#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \
	[_id] = __ctx_convert##_id,
#include <linux/bpf_types.h>
#undef BPF_PROG_TYPE
	0, /* avoid empty array */
};
#undef BPF_MAP_TYPE

static const struct btf_member *
btf_get_prog_ctx_type(struct bpf_verifier_log *log, struct btf *btf,
		      const struct btf_type *t, enum bpf_prog_type prog_type,
		      int arg)
{
	const struct btf_type *conv_struct;
	const struct btf_type *ctx_struct;
	const struct btf_member *ctx_type;
	const char *tname, *ctx_tname;

	conv_struct = bpf_ctx_convert.t;
	if (!conv_struct) {
		bpf_log(log, "btf_vmlinux is malformed\n");
		return NULL;
	}
	t = btf_type_by_id(btf, t->type);
	while (btf_type_is_modifier(t))
		t = btf_type_by_id(btf, t->type);
	if (!btf_type_is_struct(t)) {
		/* Only pointer to struct is supported for now.
		 * That means that BPF_PROG_TYPE_TRACEPOINT with BTF
		 * is not supported yet.
		 * BPF_PROG_TYPE_RAW_TRACEPOINT is fine.
		 */
		if (log->level & BPF_LOG_LEVEL)
			bpf_log(log, "arg#%d type is not a struct\n", arg);
		return NULL;
	}
	tname = btf_name_by_offset(btf, t->name_off);
	if (!tname) {
		bpf_log(log, "arg#%d struct doesn't have a name\n", arg);
		return NULL;
	}
	/* prog_type is valid bpf program type. No need for bounds check. */
	ctx_type = btf_type_member(conv_struct) + bpf_ctx_convert_map[prog_type] * 2;
	/* ctx_struct is a pointer to prog_ctx_type in vmlinux.
	 * Like 'struct __sk_buff'
	 */
	ctx_struct = btf_type_by_id(btf_vmlinux, ctx_type->type);
	if (!ctx_struct)
		/* should not happen */
		return NULL;
	ctx_tname = btf_name_by_offset(btf_vmlinux, ctx_struct->name_off);
	if (!ctx_tname) {
		/* should not happen */
		bpf_log(log, "Please fix kernel include/linux/bpf_types.h\n");
		return NULL;
	}
	/* only compare that prog's ctx type name is the same as
	 * kernel expects. No need to compare field by field.
	 * It's ok for bpf prog to do:
	 * struct __sk_buff {};
	 * int socket_filter_bpf_prog(struct __sk_buff *skb)
	 * { // no fields of skb are ever used }
	 */
	if (strcmp(ctx_tname, tname))
		return NULL;
	return ctx_type;
}

static int btf_translate_to_vmlinux(struct bpf_verifier_log *log,
				     struct btf *btf,
				     const struct btf_type *t,
				     enum bpf_prog_type prog_type,
				     int arg)
{
	const struct btf_member *prog_ctx_type, *kern_ctx_type;

	prog_ctx_type = btf_get_prog_ctx_type(log, btf, t, prog_type, arg);
	if (!prog_ctx_type)
		return -ENOENT;
	kern_ctx_type = prog_ctx_type + 1;
	return kern_ctx_type->type;
}

struct btf *btf_parse_vmlinux(void)
{
	struct btf_verifier_env *env = NULL;
	struct bpf_verifier_log *log;
	struct btf *btf = NULL;
	int err, i;

	env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
	if (!env)
		return ERR_PTR(-ENOMEM);

	log = &env->log;
	log->level = BPF_LOG_KERNEL;

	btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
	if (!btf) {
		err = -ENOMEM;
		goto errout;
	}
	env->btf = btf;

	btf->data = _binary__btf_vmlinux_bin_start;
	btf->data_size = _binary__btf_vmlinux_bin_end -
		_binary__btf_vmlinux_bin_start;

	err = btf_parse_hdr(env);
	if (err)
		goto errout;

	btf->nohdr_data = btf->data + btf->hdr.hdr_len;

	err = btf_parse_str_sec(env);
	if (err)
		goto errout;

	err = btf_check_all_metas(env);
	if (err)
		goto errout;

	/* find struct bpf_ctx_convert for type checking later */
	for (i = 1; i <= btf->nr_types; i++) {
		const struct btf_type *t;
		const char *tname;

		t = btf_type_by_id(btf, i);
		if (!__btf_type_is_struct(t))
			continue;
		tname = __btf_name_by_offset(btf, t->name_off);
		if (!strcmp(tname, "bpf_ctx_convert")) {
			/* btf_parse_vmlinux() runs under bpf_verifier_lock */
			bpf_ctx_convert.t = t;
			break;
		}
	}
	if (i > btf->nr_types) {
		err = -ENOENT;
		goto errout;
	}

	bpf_struct_ops_init(btf, log);

	btf_verifier_env_free(env);
	refcount_set(&btf->refcnt, 1);
	return btf;

errout:
	btf_verifier_env_free(env);
	if (btf) {
		kvfree(btf->types);
		kfree(btf);
	}
	return ERR_PTR(err);
}

struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog)
{
	struct bpf_prog *tgt_prog = prog->aux->linked_prog;

	if (tgt_prog) {
		return tgt_prog->aux->btf;
	} else {
		return btf_vmlinux;
	}
}

static bool is_string_ptr(struct btf *btf, const struct btf_type *t)
{
	/* t comes in already as a pointer */
	t = btf_type_by_id(btf, t->type);

	/* allow const */
	if (BTF_INFO_KIND(t->info) == BTF_KIND_CONST)
		t = btf_type_by_id(btf, t->type);

	/* char, signed char, unsigned char */
	return btf_type_is_int(t) && t->size == 1;
}

bool btf_ctx_access(int off, int size, enum bpf_access_type type,
		    const struct bpf_prog *prog,
		    struct bpf_insn_access_aux *info)
{
	const struct btf_type *t = prog->aux->attach_func_proto;
	struct bpf_prog *tgt_prog = prog->aux->linked_prog;
	struct btf *btf = bpf_prog_get_target_btf(prog);
	const char *tname = prog->aux->attach_func_name;
	struct bpf_verifier_log *log = info->log;
	const struct btf_param *args;
	u32 nr_args, arg;
	int ret;

	if (off % 8) {
		bpf_log(log, "func '%s' offset %d is not multiple of 8\n",
			tname, off);
		return false;
	}
	arg = off / 8;
	args = (const struct btf_param *)(t + 1);
	/* if (t == NULL) Fall back to default BPF prog with 5 u64 arguments */
	nr_args = t ? btf_type_vlen(t) : 5;
	if (prog->aux->attach_btf_trace) {
		/* skip first 'void *__data' argument in btf_trace_##name typedef */
		args++;
		nr_args--;
	}

	if (prog->expected_attach_type == BPF_TRACE_FEXIT &&
	    arg == nr_args) {
		if (!t)
			/* Default prog with 5 args. 6th arg is retval. */
			return true;
		/* function return type */
		t = btf_type_by_id(btf, t->type);
	} else if (arg >= nr_args) {
		bpf_log(log, "func '%s' doesn't have %d-th argument\n",
			tname, arg + 1);
		return false;
	} else {
		if (!t)
			/* Default prog with 5 args */
			return true;
		t = btf_type_by_id(btf, args[arg].type);
	}
	/* skip modifiers */
	while (btf_type_is_modifier(t))
		t = btf_type_by_id(btf, t->type);
	if (btf_type_is_int(t) || btf_type_is_enum(t))
		/* accessing a scalar */
		return true;
	if (!btf_type_is_ptr(t)) {
		bpf_log(log,
			"func '%s' arg%d '%s' has type %s. Only pointer access is allowed\n",
			tname, arg,
			__btf_name_by_offset(btf, t->name_off),
			btf_kind_str[BTF_INFO_KIND(t->info)]);
		return false;
	}
	if (t->type == 0)
		/* This is a pointer to void.
		 * It is the same as scalar from the verifier safety pov.
		 * No further pointer walking is allowed.
		 */
		return true;

	if (is_string_ptr(btf, t))
		return true;

	/* this is a pointer to another type */
	info->reg_type = PTR_TO_BTF_ID;

	if (tgt_prog) {
		ret = btf_translate_to_vmlinux(log, btf, t, tgt_prog->type, arg);
		if (ret > 0) {
			info->btf_id = ret;
			return true;
		} else {
			return false;
		}
	}

	info->btf_id = t->type;
	t = btf_type_by_id(btf, t->type);
	/* skip modifiers */
	while (btf_type_is_modifier(t)) {
		info->btf_id = t->type;
		t = btf_type_by_id(btf, t->type);
	}
	if (!btf_type_is_struct(t)) {
		bpf_log(log,
			"func '%s' arg%d type %s is not a struct\n",
			tname, arg, btf_kind_str[BTF_INFO_KIND(t->info)]);
		return false;
	}
	bpf_log(log, "func '%s' arg%d has btf_id %d type %s '%s'\n",
		tname, arg, info->btf_id, btf_kind_str[BTF_INFO_KIND(t->info)],
		__btf_name_by_offset(btf, t->name_off));
	return true;
}

int btf_struct_access(struct bpf_verifier_log *log,
		      const struct btf_type *t, int off, int size,
		      enum bpf_access_type atype,
		      u32 *next_btf_id)
{
	u32 i, moff, mtrue_end, msize = 0, total_nelems = 0;
	const struct btf_type *mtype, *elem_type = NULL;
	const struct btf_member *member;
	const char *tname, *mname;

again:
	tname = __btf_name_by_offset(btf_vmlinux, t->name_off);
	if (!btf_type_is_struct(t)) {
		bpf_log(log, "Type '%s' is not a struct\n", tname);
		return -EINVAL;
	}

	if (off + size > t->size) {
		bpf_log(log, "access beyond struct %s at off %u size %u\n",
			tname, off, size);
		return -EACCES;
	}

	for_each_member(i, t, member) {
		/* offset of the field in bytes */
		moff = btf_member_bit_offset(t, member) / 8;
		if (off + size <= moff)
			/* won't find anything, field is already too far */
			break;

		if (btf_member_bitfield_size(t, member)) {
			u32 end_bit = btf_member_bit_offset(t, member) +
				btf_member_bitfield_size(t, member);

			/* off <= moff instead of off == moff because clang
			 * does not generate a BTF member for anonymous
			 * bitfield like the ":16" here:
			 * struct {
			 *	int :16;
			 *	int x:8;
			 * };
			 */
			if (off <= moff &&
			    BITS_ROUNDUP_BYTES(end_bit) <= off + size)
				return SCALAR_VALUE;

			/* off may be accessing a following member
			 *
			 * or
			 *
			 * Doing partial access at either end of this
			 * bitfield.  Continue on this case also to
			 * treat it as not accessing this bitfield
			 * and eventually error out as field not
			 * found to keep it simple.
			 * It could be relaxed if there was a legit
			 * partial access case later.
			 */
			continue;
		}

		/* In case of "off" is pointing to holes of a struct */
		if (off < moff)
			break;

		/* type of the field */
		mtype = btf_type_by_id(btf_vmlinux, member->type);
		mname = __btf_name_by_offset(btf_vmlinux, member->name_off);

		mtype = btf_resolve_size(btf_vmlinux, mtype, &msize,
					 &elem_type, &total_nelems);
		if (IS_ERR(mtype)) {
			bpf_log(log, "field %s doesn't have size\n", mname);
			return -EFAULT;
		}

		mtrue_end = moff + msize;
		if (off >= mtrue_end)
			/* no overlap with member, keep iterating */
			continue;

		if (btf_type_is_array(mtype)) {
			u32 elem_idx;

			/* btf_resolve_size() above helps to
			 * linearize a multi-dimensional array.
			 *
			 * The logic here is treating an array
			 * in a struct as the following way:
			 *
			 * struct outer {
			 *	struct inner array[2][2];
			 * };
			 *
			 * looks like:
			 *
			 * struct outer {
			 *	struct inner array_elem0;
			 *	struct inner array_elem1;
			 *	struct inner array_elem2;
			 *	struct inner array_elem3;
			 * };
			 *
			 * When accessing outer->array[1][0], it moves
			 * moff to "array_elem2", set mtype to
			 * "struct inner", and msize also becomes
			 * sizeof(struct inner).  Then most of the
			 * remaining logic will fall through without
			 * caring the current member is an array or
			 * not.
			 *
			 * Unlike mtype/msize/moff, mtrue_end does not
			 * change.  The naming difference ("_true") tells
			 * that it is not always corresponding to
			 * the current mtype/msize/moff.
			 * It is the true end of the current
			 * member (i.e. array in this case).  That
			 * will allow an int array to be accessed like
			 * a scratch space,
			 * i.e. allow access beyond the size of
			 *      the array's element as long as it is
			 *      within the mtrue_end boundary.
			 */

			/* skip empty array */
			if (moff == mtrue_end)
				continue;

			msize /= total_nelems;
			elem_idx = (off - moff) / msize;
			moff += elem_idx * msize;
			mtype = elem_type;
		}

		/* the 'off' we're looking for is either equal to start
		 * of this field or inside of this struct
		 */
		if (btf_type_is_struct(mtype)) {
			/* our field must be inside that union or struct */
			t = mtype;

			/* adjust offset we're looking for */
			off -= moff;
			goto again;
		}

		if (btf_type_is_ptr(mtype)) {
			const struct btf_type *stype;
			u32 id;

			if (msize != size || off != moff) {
				bpf_log(log,
					"cannot access ptr member %s with moff %u in struct %s with off %u size %u\n",
					mname, moff, tname, off, size);
				return -EACCES;
			}

			stype = btf_type_skip_modifiers(btf_vmlinux, mtype->type, &id);
			if (btf_type_is_struct(stype)) {
				*next_btf_id = id;
				return PTR_TO_BTF_ID;
			}
		}

		/* Allow more flexible access within an int as long as
		 * it is within mtrue_end.
		 * Since mtrue_end could be the end of an array,
		 * that also allows using an array of int as a scratch
		 * space. e.g. skb->cb[].
		 */
		if (off + size > mtrue_end) {
			bpf_log(log,
				"access beyond the end of member %s (mend:%u) in struct %s with off %u size %u\n",
				mname, mtrue_end, tname, off, size);
			return -EACCES;
		}

		return SCALAR_VALUE;
	}
	bpf_log(log, "struct %s doesn't have field at offset %d\n", tname, off);
	return -EINVAL;
}

static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn,
				   int arg)
{
	char fnname[KSYM_SYMBOL_LEN + 4] = "btf_";
	const struct btf_param *args;
	const struct btf_type *t;
	const char *tname, *sym;
	u32 btf_id, i;

	if (IS_ERR(btf_vmlinux)) {
		bpf_log(log, "btf_vmlinux is malformed\n");
		return -EINVAL;
	}

	sym = kallsyms_lookup((long)fn, NULL, NULL, NULL, fnname + 4);
	if (!sym) {
		bpf_log(log, "kernel doesn't have kallsyms\n");
		return -EFAULT;
	}

	for (i = 1; i <= btf_vmlinux->nr_types; i++) {
		t = btf_type_by_id(btf_vmlinux, i);
		if (BTF_INFO_KIND(t->info) != BTF_KIND_TYPEDEF)
			continue;
		tname = __btf_name_by_offset(btf_vmlinux, t->name_off);
		if (!strcmp(tname, fnname))
			break;
	}
	if (i > btf_vmlinux->nr_types) {
		bpf_log(log, "helper %s type is not found\n", fnname);
		return -ENOENT;
	}

	t = btf_type_by_id(btf_vmlinux, t->type);
	if (!btf_type_is_ptr(t))
		return -EFAULT;
	t = btf_type_by_id(btf_vmlinux, t->type);
	if (!btf_type_is_func_proto(t))
		return -EFAULT;

	args = (const struct btf_param *)(t + 1);
	if (arg >= btf_type_vlen(t)) {
		bpf_log(log, "bpf helper %s doesn't have %d-th argument\n",
			fnname, arg);
		return -EINVAL;
	}

	t = btf_type_by_id(btf_vmlinux, args[arg].type);
	if (!btf_type_is_ptr(t) || !t->type) {
		/* anything but the pointer to struct is a helper config bug */
		bpf_log(log, "ARG_PTR_TO_BTF is misconfigured\n");
		return -EFAULT;
	}
	btf_id = t->type;
	t = btf_type_by_id(btf_vmlinux, t->type);
	/* skip modifiers */
	while (btf_type_is_modifier(t)) {
		btf_id = t->type;
		t = btf_type_by_id(btf_vmlinux, t->type);
	}
	if (!btf_type_is_struct(t)) {
		bpf_log(log, "ARG_PTR_TO_BTF is not a struct\n");
		return -EFAULT;
	}
	bpf_log(log, "helper %s arg%d has btf_id %d struct %s\n", fnname + 4,
		arg, btf_id, __btf_name_by_offset(btf_vmlinux, t->name_off));
	return btf_id;
}

int btf_resolve_helper_id(struct bpf_verifier_log *log,
			  const struct bpf_func_proto *fn, int arg)
{
	int *btf_id = &fn->btf_id[arg];
	int ret;

	if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID)
		return -EINVAL;

	ret = READ_ONCE(*btf_id);
	if (ret)
		return ret;
	/* ok to race the search. The result is the same */
	ret = __btf_resolve_helper_id(log, fn->func, arg);
	if (!ret) {
		/* Function argument cannot be type 'void' */
		bpf_log(log, "BTF resolution bug\n");
		return -EFAULT;
	}
	WRITE_ONCE(*btf_id, ret);
	return ret;
}

static int __get_type_size(struct btf *btf, u32 btf_id,
			   const struct btf_type **bad_type)
{
	const struct btf_type *t;

	if (!btf_id)
		/* void */
		return 0;
	t = btf_type_by_id(btf, btf_id);
	while (t && btf_type_is_modifier(t))
		t = btf_type_by_id(btf, t->type);
	if (!t) {
		*bad_type = btf->types[0];
		return -EINVAL;
	}
	if (btf_type_is_ptr(t))
		/* kernel size of pointer. Not BPF's size of pointer*/
		return sizeof(void *);
	if (btf_type_is_int(t) || btf_type_is_enum(t))
		return t->size;
	*bad_type = t;
	return -EINVAL;
}

int btf_distill_func_proto(struct bpf_verifier_log *log,
			   struct btf *btf,
			   const struct btf_type *func,
			   const char *tname,
			   struct btf_func_model *m)
{
	const struct btf_param *args;
	const struct btf_type *t;
	u32 i, nargs;
	int ret;

	if (!func) {
		/* BTF function prototype doesn't match the verifier types.
		 * Fall back to 5 u64 args.
		 */
		for (i = 0; i < 5; i++)
			m->arg_size[i] = 8;
		m->ret_size = 8;
		m->nr_args = 5;
		return 0;
	}
	args = (const struct btf_param *)(func + 1);
	nargs = btf_type_vlen(func);
	if (nargs >= MAX_BPF_FUNC_ARGS) {
		bpf_log(log,
			"The function %s has %d arguments. Too many.\n",
			tname, nargs);
		return -EINVAL;
	}
	ret = __get_type_size(btf, func->type, &t);
	if (ret < 0) {
		bpf_log(log,
			"The function %s return type %s is unsupported.\n",
			tname, btf_kind_str[BTF_INFO_KIND(t->info)]);
		return -EINVAL;
	}
	m->ret_size = ret;

	for (i = 0; i < nargs; i++) {
		ret = __get_type_size(btf, args[i].type, &t);
		if (ret < 0) {
			bpf_log(log,
				"The function %s arg%d type %s is unsupported.\n",
				tname, i, btf_kind_str[BTF_INFO_KIND(t->info)]);
			return -EINVAL;
		}
		m->arg_size[i] = ret;
	}
	m->nr_args = nargs;
	return 0;
}

/* Compare BTFs of two functions assuming only scalars and pointers to context.
 * t1 points to BTF_KIND_FUNC in btf1
 * t2 points to BTF_KIND_FUNC in btf2
 * Returns:
 * EINVAL - function prototype mismatch
 * EFAULT - verifier bug
 * 0 - 99% match. The last 1% is validated by the verifier.
 */
static int btf_check_func_type_match(struct bpf_verifier_log *log,
				     struct btf *btf1, const struct btf_type *t1,
				     struct btf *btf2, const struct btf_type *t2)
{
	const struct btf_param *args1, *args2;
	const char *fn1, *fn2, *s1, *s2;
	u32 nargs1, nargs2, i;

	fn1 = btf_name_by_offset(btf1, t1->name_off);
	fn2 = btf_name_by_offset(btf2, t2->name_off);

	if (btf_func_linkage(t1) != BTF_FUNC_GLOBAL) {
		bpf_log(log, "%s() is not a global function\n", fn1);
		return -EINVAL;
	}
	if (btf_func_linkage(t2) != BTF_FUNC_GLOBAL) {
		bpf_log(log, "%s() is not a global function\n", fn2);
		return -EINVAL;
	}

	t1 = btf_type_by_id(btf1, t1->type);
	if (!t1 || !btf_type_is_func_proto(t1))
		return -EFAULT;
	t2 = btf_type_by_id(btf2, t2->type);
	if (!t2 || !btf_type_is_func_proto(t2))
		return -EFAULT;

	args1 = (const struct btf_param *)(t1 + 1);
	nargs1 = btf_type_vlen(t1);
	args2 = (const struct btf_param *)(t2 + 1);
	nargs2 = btf_type_vlen(t2);

	if (nargs1 != nargs2) {
		bpf_log(log, "%s() has %d args while %s() has %d args\n",
			fn1, nargs1, fn2, nargs2);
		return -EINVAL;
	}

	t1 = btf_type_skip_modifiers(btf1, t1->type, NULL);
	t2 = btf_type_skip_modifiers(btf2, t2->type, NULL);
	if (t1->info != t2->info) {
		bpf_log(log,
			"Return type %s of %s() doesn't match type %s of %s()\n",
			btf_type_str(t1), fn1,
			btf_type_str(t2), fn2);
		return -EINVAL;
	}

	for (i = 0; i < nargs1; i++) {
		t1 = btf_type_skip_modifiers(btf1, args1[i].type, NULL);
		t2 = btf_type_skip_modifiers(btf2, args2[i].type, NULL);

		if (t1->info != t2->info) {
			bpf_log(log, "arg%d in %s() is %s while %s() has %s\n",
				i, fn1, btf_type_str(t1),
				fn2, btf_type_str(t2));
			return -EINVAL;
		}
		if (btf_type_has_size(t1) && t1->size != t2->size) {
			bpf_log(log,
				"arg%d in %s() has size %d while %s() has %d\n",
				i, fn1, t1->size,
				fn2, t2->size);
			return -EINVAL;
		}

		/* global functions are validated with scalars and pointers
		 * to context only. And only global functions can be replaced.
		 * Hence type check only those types.
		 */
		if (btf_type_is_int(t1) || btf_type_is_enum(t1))
			continue;
		if (!btf_type_is_ptr(t1)) {
			bpf_log(log,
				"arg%d in %s() has unrecognized type\n",
				i, fn1);
			return -EINVAL;
		}
		t1 = btf_type_skip_modifiers(btf1, t1->type, NULL);
		t2 = btf_type_skip_modifiers(btf2, t2->type, NULL);
		if (!btf_type_is_struct(t1)) {
			bpf_log(log,
				"arg%d in %s() is not a pointer to context\n",
				i, fn1);
			return -EINVAL;
		}
		if (!btf_type_is_struct(t2)) {
			bpf_log(log,
				"arg%d in %s() is not a pointer to context\n",
				i, fn2);
			return -EINVAL;
		}
		/* This is an optional check to make program writing easier.
		 * Compare names of structs and report an error to the user.
		 * btf_prepare_func_args() already checked that t2 struct
		 * is a context type. btf_prepare_func_args() will check
		 * later that t1 struct is a context type as well.
		 */
		s1 = btf_name_by_offset(btf1, t1->name_off);
		s2 = btf_name_by_offset(btf2, t2->name_off);
		if (strcmp(s1, s2)) {
			bpf_log(log,
				"arg%d %s(struct %s *) doesn't match %s(struct %s *)\n",
				i, fn1, s1, fn2, s2);
			return -EINVAL;
		}
	}
	return 0;
}

/* Compare BTFs of given program with BTF of target program */
int btf_check_type_match(struct bpf_verifier_env *env, struct bpf_prog *prog,
			 struct btf *btf2, const struct btf_type *t2)
{
	struct btf *btf1 = prog->aux->btf;
	const struct btf_type *t1;
	u32 btf_id = 0;

	if (!prog->aux->func_info) {
		bpf_log(&env->log, "Program extension requires BTF\n");
		return -EINVAL;
	}

	btf_id = prog->aux->func_info[0].type_id;
	if (!btf_id)
		return -EFAULT;

	t1 = btf_type_by_id(btf1, btf_id);
	if (!t1 || !btf_type_is_func(t1))
		return -EFAULT;

	return btf_check_func_type_match(&env->log, btf1, t1, btf2, t2);
}

/* Compare BTF of a function with given bpf_reg_state.
 * Returns:
 * EFAULT - there is a verifier bug. Abort verification.
 * EINVAL - there is a type mismatch or BTF is not available.
 * 0 - BTF matches with what bpf_reg_state expects.
 * Only PTR_TO_CTX and SCALAR_VALUE states are recognized.
 */
int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
			     struct bpf_reg_state *reg)
{
	struct bpf_verifier_log *log = &env->log;
	struct bpf_prog *prog = env->prog;
	struct btf *btf = prog->aux->btf;
	const struct btf_param *args;
	const struct btf_type *t;
	u32 i, nargs, btf_id;
	const char *tname;

	if (!prog->aux->func_info)
		return -EINVAL;

	btf_id = prog->aux->func_info[subprog].type_id;
	if (!btf_id)
		return -EFAULT;

	if (prog->aux->func_info_aux[subprog].unreliable)
		return -EINVAL;

	t = btf_type_by_id(btf, btf_id);
	if (!t || !btf_type_is_func(t)) {
		/* These checks were already done by the verifier while loading
		 * struct bpf_func_info
		 */
		bpf_log(log, "BTF of func#%d doesn't point to KIND_FUNC\n",
			subprog);
		return -EFAULT;
	}
	tname = btf_name_by_offset(btf, t->name_off);

	t = btf_type_by_id(btf, t->type);
	if (!t || !btf_type_is_func_proto(t)) {
		bpf_log(log, "Invalid BTF of func %s\n", tname);
		return -EFAULT;
	}
	args = (const struct btf_param *)(t + 1);
	nargs = btf_type_vlen(t);
	if (nargs > 5) {
		bpf_log(log, "Function %s has %d > 5 args\n", tname, nargs);
		goto out;
	}
	/* check that BTF function arguments match actual types that the
	 * verifier sees.
	 */
	for (i = 0; i < nargs; i++) {
		t = btf_type_by_id(btf, args[i].type);
		while (btf_type_is_modifier(t))
			t = btf_type_by_id(btf, t->type);
		if (btf_type_is_int(t) || btf_type_is_enum(t)) {
			if (reg[i + 1].type == SCALAR_VALUE)
				continue;
			bpf_log(log, "R%d is not a scalar\n", i + 1);
			goto out;
		}
		if (btf_type_is_ptr(t)) {
			if (reg[i + 1].type == SCALAR_VALUE) {
				bpf_log(log, "R%d is not a pointer\n", i + 1);
				goto out;
			}
			/* If function expects ctx type in BTF check that caller
			 * is passing PTR_TO_CTX.
			 */
			if (btf_get_prog_ctx_type(log, btf, t, prog->type, i)) {
				if (reg[i + 1].type != PTR_TO_CTX) {
					bpf_log(log,
						"arg#%d expected pointer to ctx, but got %s\n",
						i, btf_kind_str[BTF_INFO_KIND(t->info)]);
					goto out;
				}
				if (check_ctx_reg(env, &reg[i + 1], i + 1))
					goto out;
				continue;
			}
		}
		bpf_log(log, "Unrecognized arg#%d type %s\n",
			i, btf_kind_str[BTF_INFO_KIND(t->info)]);
		goto out;
	}
	return 0;
out:
	/* Compiler optimizations can remove arguments from static functions
	 * or mismatched type can be passed into a global function.
	 * In such cases mark the function as unreliable from BTF point of view.
	 */
	prog->aux->func_info_aux[subprog].unreliable = true;
	return -EINVAL;
}

/* Convert BTF of a function into bpf_reg_state if possible
 * Returns:
 * EFAULT - there is a verifier bug. Abort verification.
 * EINVAL - cannot convert BTF.
 * 0 - Successfully converted BTF into bpf_reg_state
 * (either PTR_TO_CTX or SCALAR_VALUE).
 */
int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
			  struct bpf_reg_state *reg)
{
	struct bpf_verifier_log *log = &env->log;
	struct bpf_prog *prog = env->prog;
	enum bpf_prog_type prog_type = prog->type;
	struct btf *btf = prog->aux->btf;
	const struct btf_param *args;
	const struct btf_type *t;
	u32 i, nargs, btf_id;
	const char *tname;

	if (!prog->aux->func_info ||
	    prog->aux->func_info_aux[subprog].linkage != BTF_FUNC_GLOBAL) {
		bpf_log(log, "Verifier bug\n");
		return -EFAULT;
	}

	btf_id = prog->aux->func_info[subprog].type_id;
	if (!btf_id) {
		bpf_log(log, "Global functions need valid BTF\n");
		return -EFAULT;
	}

	t = btf_type_by_id(btf, btf_id);
	if (!t || !btf_type_is_func(t)) {
		/* These checks were already done by the verifier while loading
		 * struct bpf_func_info
		 */
		bpf_log(log, "BTF of func#%d doesn't point to KIND_FUNC\n",
			subprog);
		return -EFAULT;
	}
	tname = btf_name_by_offset(btf, t->name_off);

	if (log->level & BPF_LOG_LEVEL)
		bpf_log(log, "Validating %s() func#%d...\n",
			tname, subprog);

	if (prog->aux->func_info_aux[subprog].unreliable) {
		bpf_log(log, "Verifier bug in function %s()\n", tname);
		return -EFAULT;
	}
	if (prog_type == BPF_PROG_TYPE_EXT)
		prog_type = prog->aux->linked_prog->type;

	t = btf_type_by_id(btf, t->type);
	if (!t || !btf_type_is_func_proto(t)) {
		bpf_log(log, "Invalid type of function %s()\n", tname);
		return -EFAULT;
	}
	args = (const struct btf_param *)(t + 1);
	nargs = btf_type_vlen(t);
	if (nargs > 5) {
		bpf_log(log, "Global function %s() with %d > 5 args. Buggy compiler.\n",
			tname, nargs);
		return -EINVAL;
	}
	/* check that function returns int */
	t = btf_type_by_id(btf, t->type);
	while (btf_type_is_modifier(t))
		t = btf_type_by_id(btf, t->type);
	if (!btf_type_is_int(t) && !btf_type_is_enum(t)) {
		bpf_log(log,
			"Global function %s() doesn't return scalar. Only those are supported.\n",
			tname);
		return -EINVAL;
	}
	/* Convert BTF function arguments into verifier types.
	 * Only PTR_TO_CTX and SCALAR are supported atm.
	 */
	for (i = 0; i < nargs; i++) {
		t = btf_type_by_id(btf, args[i].type);
		while (btf_type_is_modifier(t))
			t = btf_type_by_id(btf, t->type);
		if (btf_type_is_int(t) || btf_type_is_enum(t)) {
			reg[i + 1].type = SCALAR_VALUE;
			continue;
		}
		if (btf_type_is_ptr(t) &&
		    btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
			reg[i + 1].type = PTR_TO_CTX;
			continue;
		}
		bpf_log(log, "Arg#%d type %s in %s() is not supported yet.\n",
			i, btf_kind_str[BTF_INFO_KIND(t->info)], tname);
		return -EINVAL;
	}
	return 0;
}

void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
		       struct seq_file *m)
{
	const struct btf_type *t = btf_type_by_id(btf, type_id);

	btf_type_ops(t)->seq_show(btf, t, type_id, obj, 0, m);
}

#ifdef CONFIG_PROC_FS
static void bpf_btf_show_fdinfo(struct seq_file *m, struct file *filp)
{
	const struct btf *btf = filp->private_data;

	seq_printf(m, "btf_id:\t%u\n", btf->id);
}
#endif

static int btf_release(struct inode *inode, struct file *filp)
{
	btf_put(filp->private_data);
	return 0;
}

const struct file_operations btf_fops = {
#ifdef CONFIG_PROC_FS
	.show_fdinfo	= bpf_btf_show_fdinfo,
#endif
	.release	= btf_release,
};

static int __btf_new_fd(struct btf *btf)
{
	return anon_inode_getfd("btf", &btf_fops, btf, O_RDONLY | O_CLOEXEC);
}

int btf_new_fd(const union bpf_attr *attr)
{
	struct btf *btf;
	int ret;

	btf = btf_parse(u64_to_user_ptr(attr->btf),
			attr->btf_size, attr->btf_log_level,
			u64_to_user_ptr(attr->btf_log_buf),
			attr->btf_log_size);
	if (IS_ERR(btf))
		return PTR_ERR(btf);

	ret = btf_alloc_id(btf);
	if (ret) {
		btf_free(btf);
		return ret;
	}

	/*
	 * The BTF ID is published to the userspace.
	 * All BTF free must go through call_rcu() from
	 * now on (i.e. free by calling btf_put()).
	 */

	ret = __btf_new_fd(btf);
	if (ret < 0)
		btf_put(btf);

	return ret;
}

struct btf *btf_get_by_fd(int fd)
{
	struct btf *btf;
	struct fd f;

	f = fdget(fd);

	if (!f.file)
		return ERR_PTR(-EBADF);

	if (f.file->f_op != &btf_fops) {
		fdput(f);
		return ERR_PTR(-EINVAL);
	}

	btf = f.file->private_data;
	refcount_inc(&btf->refcnt);
	fdput(f);

	return btf;
}

int btf_get_info_by_fd(const struct btf *btf,
		       const union bpf_attr *attr,
		       union bpf_attr __user *uattr)
{
	struct bpf_btf_info __user *uinfo;
	struct bpf_btf_info info = {};
	u32 info_copy, btf_copy;
	void __user *ubtf;
	u32 uinfo_len;

	uinfo = u64_to_user_ptr(attr->info.info);
	uinfo_len = attr->info.info_len;

	info_copy = min_t(u32, uinfo_len, sizeof(info));
	if (copy_from_user(&info, uinfo, info_copy))
		return -EFAULT;

	info.id = btf->id;
	ubtf = u64_to_user_ptr(info.btf);
	btf_copy = min_t(u32, btf->data_size, info.btf_size);
	if (copy_to_user(ubtf, btf->data, btf_copy))
		return -EFAULT;
	info.btf_size = btf->data_size;

	if (copy_to_user(uinfo, &info, info_copy) ||
	    put_user(info_copy, &uattr->info.info_len))
		return -EFAULT;

	return 0;
}

int btf_get_fd_by_id(u32 id)
{
	struct btf *btf;
	int fd;

	rcu_read_lock();
	btf = idr_find(&btf_idr, id);
	if (!btf || !refcount_inc_not_zero(&btf->refcnt))
		btf = ERR_PTR(-ENOENT);
	rcu_read_unlock();

	if (IS_ERR(btf))
		return PTR_ERR(btf);

	fd = __btf_new_fd(btf);
	if (fd < 0)
		btf_put(btf);

	return fd;
}

u32 btf_id(const struct btf *btf)
{
	return btf->id;
}