arch/x86/lib/copy_user_64.S

/* Copyright 2002 Andi Kleen, SuSE Labs.
 * Subject to the GNU Public License v2.
 * 
 * Functions to copy from and to user space.		
 */		 

#include <linux/linkage.h>
#include <asm/dwarf2.h>

#define FIX_ALIGNMENT 1

#include <asm/current.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/cpufeature.h>

	.macro ALTERNATIVE_JUMP feature,orig,alt
0:
	.byte 0xe9	/* 32bit jump */
	.long \orig-1f	/* by default jump to orig */
1:
	.section .altinstr_replacement,"ax"
2:	.byte 0xe9	             /* near jump with 32bit immediate */
	.long \alt-1b /* offset */   /* or alternatively to alt */
	.previous
	.section .altinstructions,"a"
	.align 8
	.quad  0b
	.quad  2b
	.byte  \feature		     /* when feature is set */
	.byte  5
	.byte  5
	.previous
	.endm

/* Standard copy_to_user with segment limit checking */		
ENTRY(copy_to_user)
	CFI_STARTPROC
	GET_THREAD_INFO(%rax)
	movq %rdi,%rcx
	addq %rdx,%rcx
	jc  bad_to_user
	cmpq TI_addr_limit(%rax),%rcx
	jae bad_to_user
	xorl %eax,%eax	/* clear zero flag */
	ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
	CFI_ENDPROC

ENTRY(copy_user_generic)
	CFI_STARTPROC
	movl $1,%ecx	/* set zero flag */
	ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
	CFI_ENDPROC

ENTRY(__copy_from_user_inatomic)
	CFI_STARTPROC
	xorl %ecx,%ecx	/* clear zero flag */
	ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
	CFI_ENDPROC

/* Standard copy_from_user with segment limit checking */	
ENTRY(copy_from_user)
	CFI_STARTPROC
	GET_THREAD_INFO(%rax)
	movq %rsi,%rcx
	addq %rdx,%rcx
	jc  bad_from_user
	cmpq TI_addr_limit(%rax),%rcx
	jae  bad_from_user
	movl $1,%ecx	/* set zero flag */
	ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
	CFI_ENDPROC
ENDPROC(copy_from_user)
	
	.section .fixup,"ax"
	/* must zero dest */
bad_from_user:
	CFI_STARTPROC
	movl %edx,%ecx
	xorl %eax,%eax
	rep
	stosb
bad_to_user:
	movl	%edx,%eax
	ret
	CFI_ENDPROC
END(bad_from_user)
	.previous
	
		
/*
 * copy_user_generic_unrolled - memory copy with exception handling.
 * This version is for CPUs like P4 that don't have efficient micro code for rep movsq
 * 	
 * Input:	
 * rdi destination
 * rsi source
 * rdx count
 * ecx zero flag -- if true zero destination on error
 *
 * Output:		
 * eax uncopied bytes or 0 if successful.
 */
ENTRY(copy_user_generic_unrolled)
	CFI_STARTPROC
	pushq %rbx
	CFI_ADJUST_CFA_OFFSET 8
	CFI_REL_OFFSET rbx, 0
	pushq %rcx
	CFI_ADJUST_CFA_OFFSET 8
	CFI_REL_OFFSET rcx, 0
	xorl %eax,%eax		/*zero for the exception handler */

#ifdef FIX_ALIGNMENT
	/* check for bad alignment of destination */
	movl %edi,%ecx
	andl $7,%ecx
	jnz  .Lbad_alignment
.Lafter_bad_alignment:
#endif

	movq %rdx,%rcx

	movl $64,%ebx
	shrq $6,%rdx
	decq %rdx
	js   .Lhandle_tail

	.p2align 4
.Lloop:
.Ls1:	movq (%rsi),%r11
.Ls2:	movq 1*8(%rsi),%r8
.Ls3:	movq 2*8(%rsi),%r9
.Ls4:	movq 3*8(%rsi),%r10
.Ld1:	movq %r11,(%rdi)
.Ld2:	movq %r8,1*8(%rdi)
.Ld3:	movq %r9,2*8(%rdi)
.Ld4:	movq %r10,3*8(%rdi)

.Ls5:	movq 4*8(%rsi),%r11
.Ls6:	movq 5*8(%rsi),%r8
.Ls7:	movq 6*8(%rsi),%r9
.Ls8:	movq 7*8(%rsi),%r10
.Ld5:	movq %r11,4*8(%rdi)
.Ld6:	movq %r8,5*8(%rdi)
.Ld7:	movq %r9,6*8(%rdi)
.Ld8:	movq %r10,7*8(%rdi)

	decq %rdx

	leaq 64(%rsi),%rsi
	leaq 64(%rdi),%rdi

	jns  .Lloop

	.p2align 4
.Lhandle_tail:
	movl %ecx,%edx
	andl $63,%ecx
	shrl $3,%ecx
	jz   .Lhandle_7
	movl $8,%ebx
	.p2align 4
.Lloop_8:
.Ls9:	movq (%rsi),%r8
.Ld9:	movq %r8,(%rdi)
	decl %ecx
	leaq 8(%rdi),%rdi
	leaq 8(%rsi),%rsi
	jnz .Lloop_8

.Lhandle_7:
	movl %edx,%ecx
	andl $7,%ecx
	jz   .Lende
	.p2align 4
.Lloop_1:
.Ls10:	movb (%rsi),%bl
.Ld10:	movb %bl,(%rdi)
	incq %rdi
	incq %rsi
	decl %ecx
	jnz .Lloop_1

	CFI_REMEMBER_STATE
.Lende:
	popq %rcx
	CFI_ADJUST_CFA_OFFSET -8
	CFI_RESTORE rcx
	popq %rbx
	CFI_ADJUST_CFA_OFFSET -8
	CFI_RESTORE rbx
	ret
	CFI_RESTORE_STATE

#ifdef FIX_ALIGNMENT
	/* align destination */
	.p2align 4
.Lbad_alignment:
	movl $8,%r9d
	subl %ecx,%r9d
	movl %r9d,%ecx
	cmpq %r9,%rdx
	jz   .Lhandle_7
	js   .Lhandle_7
.Lalign_1:
.Ls11:	movb (%rsi),%bl
.Ld11:	movb %bl,(%rdi)
	incq %rsi
	incq %rdi
	decl %ecx
	jnz .Lalign_1
	subq %r9,%rdx
	jmp .Lafter_bad_alignment
#endif

	/* table sorted by exception address */
	.section __ex_table,"a"
	.align 8
	.quad .Ls1,.Ls1e	/* Ls1-Ls4 have copied zero bytes */
	.quad .Ls2,.Ls1e
	.quad .Ls3,.Ls1e
	.quad .Ls4,.Ls1e
	.quad .Ld1,.Ls1e	/* Ld1-Ld4 have copied 0-24 bytes */
	.quad .Ld2,.Ls2e
	.quad .Ld3,.Ls3e
	.quad .Ld4,.Ls4e
	.quad .Ls5,.Ls5e	/* Ls5-Ls8 have copied 32 bytes */
	.quad .Ls6,.Ls5e
	.quad .Ls7,.Ls5e
	.quad .Ls8,.Ls5e
	.quad .Ld5,.Ls5e	/* Ld5-Ld8 have copied 32-56 bytes */
	.quad .Ld6,.Ls6e
	.quad .Ld7,.Ls7e
	.quad .Ld8,.Ls8e
	.quad .Ls9,.Le_quad
	.quad .Ld9,.Le_quad
	.quad .Ls10,.Le_byte
	.quad .Ld10,.Le_byte
#ifdef FIX_ALIGNMENT
	.quad .Ls11,.Lzero_rest
	.quad .Ld11,.Lzero_rest
#endif
	.quad .Le5,.Le_zero
	.previous

	/* eax: zero, ebx: 64 */
.Ls1e: 	addl $8,%eax		/* eax is bytes left uncopied within the loop (Ls1e: 64 .. Ls8e: 8) */
.Ls2e: 	addl $8,%eax
.Ls3e: 	addl $8,%eax
.Ls4e: 	addl $8,%eax
.Ls5e: 	addl $8,%eax
.Ls6e: 	addl $8,%eax
.Ls7e: 	addl $8,%eax
.Ls8e: 	addl $8,%eax
	addq %rbx,%rdi	/* +64 */
	subq %rax,%rdi  /* correct destination with computed offset */

	shlq $6,%rdx	/* loop counter * 64 (stride length) */
	addq %rax,%rdx	/* add offset to loopcnt */
	andl $63,%ecx	/* remaining bytes */
	addq %rcx,%rdx	/* add them */
	jmp .Lzero_rest

	/* exception on quad word loop in tail handling */
	/* ecx:	loopcnt/8, %edx: length, rdi: correct */
.Le_quad:
	shll $3,%ecx
	andl $7,%edx
	addl %ecx,%edx
	/* edx: bytes to zero, rdi: dest, eax:zero */
.Lzero_rest:
	cmpl $0,(%rsp)
	jz   .Le_zero
	movq %rdx,%rcx
.Le_byte:
	xorl %eax,%eax
.Le5:	rep
	stosb
	/* when there is another exception while zeroing the rest just return */
.Le_zero:
	movq %rdx,%rax
	jmp .Lende
	CFI_ENDPROC
ENDPROC(copy_user_generic)


	/* Some CPUs run faster using the string copy instructions.
	   This is also a lot simpler. Use them when possible.
	   Patch in jmps to this code instead of copying it fully
	   to avoid unwanted aliasing in the exception tables. */

 /* rdi	destination
  * rsi source
  * rdx count
  * ecx zero flag
  *
  * Output:
  * eax uncopied bytes or 0 if successfull.
  *
  * Only 4GB of copy is supported. This shouldn't be a problem
  * because the kernel normally only writes from/to page sized chunks
  * even if user space passed a longer buffer.
  * And more would be dangerous because both Intel and AMD have
  * errata with rep movsq > 4GB. If someone feels the need to fix
  * this please consider this.
  */
ENTRY(copy_user_generic_string)
	CFI_STARTPROC
	movl %ecx,%r8d		/* save zero flag */
	movl %edx,%ecx
	shrl $3,%ecx
	andl $7,%edx	
	jz   10f
1:	rep 
	movsq 
	movl %edx,%ecx
2:	rep
	movsb
9:	movl %ecx,%eax
	ret

	/* multiple of 8 byte */
10:	rep
	movsq
	xor %eax,%eax
	ret

	/* exception handling */
3:      lea (%rdx,%rcx,8),%rax	/* exception on quad loop */
	jmp 6f
5:	movl %ecx,%eax		/* exception on byte loop */
	/* eax: left over bytes */
6:	testl %r8d,%r8d		/* zero flag set? */
	jz 7f
	movl %eax,%ecx		/* initialize x86 loop counter */
	push %rax
	xorl %eax,%eax
8:	rep
	stosb 			/* zero the rest */
11:	pop %rax
7:	ret
	CFI_ENDPROC
END(copy_user_generic_c)

	.section __ex_table,"a"
	.quad 1b,3b
	.quad 2b,5b
	.quad 8b,11b
	.quad 10b,3b
	.previous