lib/test_meminit.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Test cases for SL[AOU]B/page initialization at alloc/free time.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/vmalloc.h>

#define GARBAGE_INT (0x09A7BA9E)
#define GARBAGE_BYTE (0x9E)

#define REPORT_FAILURES_IN_FN() \
	do {	\
		if (failures)	\
			pr_info("%s failed %d out of %d times\n",	\
				__func__, failures, num_tests);		\
		else		\
			pr_info("all %d tests in %s passed\n",		\
				num_tests, __func__);			\
	} while (0)

/* Calculate the number of uninitialized bytes in the buffer. */
static int __init count_nonzero_bytes(void *ptr, size_t size)
{
	int i, ret = 0;
	unsigned char *p = (unsigned char *)ptr;

	for (i = 0; i < size; i++)
		if (p[i])
			ret++;
	return ret;
}

/* Fill a buffer with garbage, skipping |skip| first bytes. */
static void __init fill_with_garbage_skip(void *ptr, int size, size_t skip)
{
	unsigned int *p = (unsigned int *)((char *)ptr + skip);
	int i = 0;

	WARN_ON(skip > size);
	size -= skip;

	while (size >= sizeof(*p)) {
		p[i] = GARBAGE_INT;
		i++;
		size -= sizeof(*p);
	}
	if (size)
		memset(&p[i], GARBAGE_BYTE, size);
}

static void __init fill_with_garbage(void *ptr, size_t size)
{
	fill_with_garbage_skip(ptr, size, 0);
}

static int __init do_alloc_pages_order(int order, int *total_failures)
{
	struct page *page;
	void *buf;
	size_t size = PAGE_SIZE << order;

	page = alloc_pages(GFP_KERNEL, order);
	buf = page_address(page);
	fill_with_garbage(buf, size);
	__free_pages(page, order);

	page = alloc_pages(GFP_KERNEL, order);
	buf = page_address(page);
	if (count_nonzero_bytes(buf, size))
		(*total_failures)++;
	fill_with_garbage(buf, size);
	__free_pages(page, order);
	return 1;
}

/* Test the page allocator by calling alloc_pages with different orders. */
static int __init test_pages(int *total_failures)
{
	int failures = 0, num_tests = 0;
	int i;

	for (i = 0; i < 10; i++)
		num_tests += do_alloc_pages_order(i, &failures);

	REPORT_FAILURES_IN_FN();
	*total_failures += failures;
	return num_tests;
}

/* Test kmalloc() with given parameters. */
static int __init do_kmalloc_size(size_t size, int *total_failures)
{
	void *buf;

	buf = kmalloc(size, GFP_KERNEL);
	fill_with_garbage(buf, size);
	kfree(buf);

	buf = kmalloc(size, GFP_KERNEL);
	if (count_nonzero_bytes(buf, size))
		(*total_failures)++;
	fill_with_garbage(buf, size);
	kfree(buf);
	return 1;
}

/* Test vmalloc() with given parameters. */
static int __init do_vmalloc_size(size_t size, int *total_failures)
{
	void *buf;

	buf = vmalloc(size);
	fill_with_garbage(buf, size);
	vfree(buf);

	buf = vmalloc(size);
	if (count_nonzero_bytes(buf, size))
		(*total_failures)++;
	fill_with_garbage(buf, size);
	vfree(buf);
	return 1;
}

/* Test kmalloc()/vmalloc() by allocating objects of different sizes. */
static int __init test_kvmalloc(int *total_failures)
{
	int failures = 0, num_tests = 0;
	int i, size;

	for (i = 0; i < 20; i++) {
		size = 1 << i;
		num_tests += do_kmalloc_size(size, &failures);
		num_tests += do_vmalloc_size(size, &failures);
	}

	REPORT_FAILURES_IN_FN();
	*total_failures += failures;
	return num_tests;
}

#define CTOR_BYTES (sizeof(unsigned int))
#define CTOR_PATTERN (0x41414141)
/* Initialize the first 4 bytes of the object. */
static void test_ctor(void *obj)
{
	*(unsigned int *)obj = CTOR_PATTERN;
}

/*
 * Check the invariants for the buffer allocated from a slab cache.
 * If the cache has a test constructor, the first 4 bytes of the object must
 * always remain equal to CTOR_PATTERN.
 * If the cache isn't an RCU-typesafe one, or if the allocation is done with
 * __GFP_ZERO, then the object contents must be zeroed after allocation.
 * If the cache is an RCU-typesafe one, the object contents must never be
 * zeroed after the first use. This is checked by memcmp() in
 * do_kmem_cache_size().
 */
static bool __init check_buf(void *buf, int size, bool want_ctor,
			     bool want_rcu, bool want_zero)
{
	int bytes;
	bool fail = false;

	bytes = count_nonzero_bytes(buf, size);
	WARN_ON(want_ctor && want_zero);
	if (want_zero)
		return bytes;
	if (want_ctor) {
		if (*(unsigned int *)buf != CTOR_PATTERN)
			fail = 1;
	} else {
		if (bytes)
			fail = !want_rcu;
	}
	return fail;
}

/*
 * Test kmem_cache with given parameters:
 *  want_ctor - use a constructor;
 *  want_rcu - use SLAB_TYPESAFE_BY_RCU;
 *  want_zero - use __GFP_ZERO.
 */
static int __init do_kmem_cache_size(size_t size, bool want_ctor,
				     bool want_rcu, bool want_zero,
				     int *total_failures)
{
	struct kmem_cache *c;
	int iter;
	bool fail = false;
	gfp_t alloc_mask = GFP_KERNEL | (want_zero ? __GFP_ZERO : 0);
	void *buf, *buf_copy;

	c = kmem_cache_create("test_cache", size, 1,
			      want_rcu ? SLAB_TYPESAFE_BY_RCU : 0,
			      want_ctor ? test_ctor : NULL);
	for (iter = 0; iter < 10; iter++) {
		buf = kmem_cache_alloc(c, alloc_mask);
		/* Check that buf is zeroed, if it must be. */
		fail = check_buf(buf, size, want_ctor, want_rcu, want_zero);
		fill_with_garbage_skip(buf, size, want_ctor ? CTOR_BYTES : 0);

		if (!want_rcu) {
			kmem_cache_free(c, buf);
			continue;
		}

		/*
		 * If this is an RCU cache, use a critical section to ensure we
		 * can touch objects after they're freed.
		 */
		rcu_read_lock();
		/*
		 * Copy the buffer to check that it's not wiped on
		 * free().
		 */
		buf_copy = kmalloc(size, GFP_ATOMIC);
		if (buf_copy)
			memcpy(buf_copy, buf, size);

		kmem_cache_free(c, buf);
		/*
		 * Check that |buf| is intact after kmem_cache_free().
		 * |want_zero| is false, because we wrote garbage to
		 * the buffer already.
		 */
		fail |= check_buf(buf, size, want_ctor, want_rcu,
				  false);
		if (buf_copy) {
			fail |= (bool)memcmp(buf, buf_copy, size);
			kfree(buf_copy);
		}
		rcu_read_unlock();
	}
	kmem_cache_destroy(c);

	*total_failures += fail;
	return 1;
}

/*
 * Check that the data written to an RCU-allocated object survives
 * reallocation.
 */
static int __init do_kmem_cache_rcu_persistent(int size, int *total_failures)
{
	struct kmem_cache *c;
	void *buf, *buf_contents, *saved_ptr;
	void **used_objects;
	int i, iter, maxiter = 1024;
	bool fail = false;

	c = kmem_cache_create("test_cache", size, size, SLAB_TYPESAFE_BY_RCU,
			      NULL);
	buf = kmem_cache_alloc(c, GFP_KERNEL);
	saved_ptr = buf;
	fill_with_garbage(buf, size);
	buf_contents = kmalloc(size, GFP_KERNEL);
	if (!buf_contents)
		goto out;
	used_objects = kmalloc_array(maxiter, sizeof(void *), GFP_KERNEL);
	if (!used_objects) {
		kfree(buf_contents);
		goto out;
	}
	memcpy(buf_contents, buf, size);
	kmem_cache_free(c, buf);
	/*
	 * Run for a fixed number of iterations. If we never hit saved_ptr,
	 * assume the test passes.
	 */
	for (iter = 0; iter < maxiter; iter++) {
		buf = kmem_cache_alloc(c, GFP_KERNEL);
		used_objects[iter] = buf;
		if (buf == saved_ptr) {
			fail = memcmp(buf_contents, buf, size);
			for (i = 0; i <= iter; i++)
				kmem_cache_free(c, used_objects[i]);
			goto free_out;
		}
	}

free_out:
	kmem_cache_destroy(c);
	kfree(buf_contents);
	kfree(used_objects);
out:
	*total_failures += fail;
	return 1;
}

/*
 * Test kmem_cache allocation by creating caches of different sizes, with and
 * without constructors, with and without SLAB_TYPESAFE_BY_RCU.
 */
static int __init test_kmemcache(int *total_failures)
{
	int failures = 0, num_tests = 0;
	int i, flags, size;
	bool ctor, rcu, zero;

	for (i = 0; i < 10; i++) {
		size = 8 << i;
		for (flags = 0; flags < 8; flags++) {
			ctor = flags & 1;
			rcu = flags & 2;
			zero = flags & 4;
			if (ctor & zero)
				continue;
			num_tests += do_kmem_cache_size(size, ctor, rcu, zero,
							&failures);
		}
	}
	REPORT_FAILURES_IN_FN();
	*total_failures += failures;
	return num_tests;
}

/* Test the behavior of SLAB_TYPESAFE_BY_RCU caches of different sizes. */
static int __init test_rcu_persistent(int *total_failures)
{
	int failures = 0, num_tests = 0;
	int i, size;

	for (i = 0; i < 10; i++) {
		size = 8 << i;
		num_tests += do_kmem_cache_rcu_persistent(size, &failures);
	}
	REPORT_FAILURES_IN_FN();
	*total_failures += failures;
	return num_tests;
}

/*
 * Run the tests. Each test function returns the number of executed tests and
 * updates |failures| with the number of failed tests.
 */
static int __init test_meminit_init(void)
{
	int failures = 0, num_tests = 0;

	num_tests += test_pages(&failures);
	num_tests += test_kvmalloc(&failures);
	num_tests += test_kmemcache(&failures);
	num_tests += test_rcu_persistent(&failures);

	if (failures == 0)
		pr_info("all %d tests passed!\n", num_tests);
	else
		pr_info("failures: %d out of %d\n", failures, num_tests);

	return failures ? -EINVAL : 0;
}
module_init(test_meminit_init);

MODULE_LICENSE("GPL");