forked from Minki/linux
92b0729c34
Make use of the EXTABLE_FAULT exception table entries to write a kernel copy routine that doesn't crash the system if it encounters a machine check. Prime use case for this is to copy from large arrays of non-volatile memory used as storage. We have to use an unrolled copy loop for now because current hardware implementations treat a machine check in "rep mov" as fatal. When that is fixed we can simplify. Return type is a "bool". True means that we copied OK, false means that it didn't. Signed-off-by: Tony Luck <tony.luck@intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@gmail.com> Link: http://lkml.kernel.org/r/a44e1055efc2d2a9473307b22c91caa437aa3f8b.1456439214.git.tony.luck@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
297 lines
6.0 KiB
ArmAsm
297 lines
6.0 KiB
ArmAsm
/* Copyright 2002 Andi Kleen */
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#include <linux/linkage.h>
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#include <asm/cpufeature.h>
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#include <asm/alternative-asm.h>
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/*
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* We build a jump to memcpy_orig by default which gets NOPped out on
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* the majority of x86 CPUs which set REP_GOOD. In addition, CPUs which
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* have the enhanced REP MOVSB/STOSB feature (ERMS), change those NOPs
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* to a jmp to memcpy_erms which does the REP; MOVSB mem copy.
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*/
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.weak memcpy
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/*
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* memcpy - Copy a memory block.
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*
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* Input:
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* rdi destination
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* rsi source
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* rdx count
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*
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* Output:
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* rax original destination
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*/
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ENTRY(__memcpy)
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ENTRY(memcpy)
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ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \
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"jmp memcpy_erms", X86_FEATURE_ERMS
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movq %rdi, %rax
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movq %rdx, %rcx
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shrq $3, %rcx
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andl $7, %edx
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rep movsq
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movl %edx, %ecx
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rep movsb
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ret
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ENDPROC(memcpy)
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ENDPROC(__memcpy)
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/*
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* memcpy_erms() - enhanced fast string memcpy. This is faster and
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* simpler than memcpy. Use memcpy_erms when possible.
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*/
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ENTRY(memcpy_erms)
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movq %rdi, %rax
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movq %rdx, %rcx
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rep movsb
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ret
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ENDPROC(memcpy_erms)
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ENTRY(memcpy_orig)
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movq %rdi, %rax
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cmpq $0x20, %rdx
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jb .Lhandle_tail
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/*
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* We check whether memory false dependence could occur,
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* then jump to corresponding copy mode.
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*/
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cmp %dil, %sil
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jl .Lcopy_backward
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subq $0x20, %rdx
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.Lcopy_forward_loop:
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subq $0x20, %rdx
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/*
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* Move in blocks of 4x8 bytes:
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*/
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movq 0*8(%rsi), %r8
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movq 1*8(%rsi), %r9
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movq 2*8(%rsi), %r10
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movq 3*8(%rsi), %r11
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leaq 4*8(%rsi), %rsi
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movq %r8, 0*8(%rdi)
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movq %r9, 1*8(%rdi)
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movq %r10, 2*8(%rdi)
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movq %r11, 3*8(%rdi)
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leaq 4*8(%rdi), %rdi
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jae .Lcopy_forward_loop
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addl $0x20, %edx
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jmp .Lhandle_tail
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.Lcopy_backward:
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/*
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* Calculate copy position to tail.
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*/
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addq %rdx, %rsi
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addq %rdx, %rdi
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subq $0x20, %rdx
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/*
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* At most 3 ALU operations in one cycle,
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* so append NOPS in the same 16 bytes trunk.
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*/
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.p2align 4
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.Lcopy_backward_loop:
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subq $0x20, %rdx
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movq -1*8(%rsi), %r8
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movq -2*8(%rsi), %r9
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movq -3*8(%rsi), %r10
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movq -4*8(%rsi), %r11
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leaq -4*8(%rsi), %rsi
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movq %r8, -1*8(%rdi)
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movq %r9, -2*8(%rdi)
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movq %r10, -3*8(%rdi)
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movq %r11, -4*8(%rdi)
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leaq -4*8(%rdi), %rdi
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jae .Lcopy_backward_loop
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/*
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* Calculate copy position to head.
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*/
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addl $0x20, %edx
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subq %rdx, %rsi
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subq %rdx, %rdi
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.Lhandle_tail:
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cmpl $16, %edx
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jb .Lless_16bytes
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/*
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* Move data from 16 bytes to 31 bytes.
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*/
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movq 0*8(%rsi), %r8
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movq 1*8(%rsi), %r9
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movq -2*8(%rsi, %rdx), %r10
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movq -1*8(%rsi, %rdx), %r11
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movq %r8, 0*8(%rdi)
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movq %r9, 1*8(%rdi)
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movq %r10, -2*8(%rdi, %rdx)
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movq %r11, -1*8(%rdi, %rdx)
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retq
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.p2align 4
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.Lless_16bytes:
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cmpl $8, %edx
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jb .Lless_8bytes
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/*
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* Move data from 8 bytes to 15 bytes.
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*/
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movq 0*8(%rsi), %r8
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movq -1*8(%rsi, %rdx), %r9
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movq %r8, 0*8(%rdi)
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movq %r9, -1*8(%rdi, %rdx)
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retq
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.p2align 4
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.Lless_8bytes:
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cmpl $4, %edx
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jb .Lless_3bytes
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/*
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* Move data from 4 bytes to 7 bytes.
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*/
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movl (%rsi), %ecx
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movl -4(%rsi, %rdx), %r8d
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movl %ecx, (%rdi)
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movl %r8d, -4(%rdi, %rdx)
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retq
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.p2align 4
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.Lless_3bytes:
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subl $1, %edx
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jb .Lend
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/*
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* Move data from 1 bytes to 3 bytes.
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*/
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movzbl (%rsi), %ecx
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jz .Lstore_1byte
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movzbq 1(%rsi), %r8
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movzbq (%rsi, %rdx), %r9
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movb %r8b, 1(%rdi)
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movb %r9b, (%rdi, %rdx)
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.Lstore_1byte:
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movb %cl, (%rdi)
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.Lend:
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retq
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ENDPROC(memcpy_orig)
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#ifndef CONFIG_UML
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/*
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* memcpy_mcsafe - memory copy with machine check exception handling
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* Note that we only catch machine checks when reading the source addresses.
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* Writes to target are posted and don't generate machine checks.
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*/
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ENTRY(memcpy_mcsafe)
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cmpl $8, %edx
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/* Less than 8 bytes? Go to byte copy loop */
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jb .L_no_whole_words
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/* Check for bad alignment of source */
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testl $7, %esi
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/* Already aligned */
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jz .L_8byte_aligned
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/* Copy one byte at a time until source is 8-byte aligned */
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movl %esi, %ecx
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andl $7, %ecx
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subl $8, %ecx
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negl %ecx
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subl %ecx, %edx
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.L_copy_leading_bytes:
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movb (%rsi), %al
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movb %al, (%rdi)
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incq %rsi
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incq %rdi
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decl %ecx
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jnz .L_copy_leading_bytes
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.L_8byte_aligned:
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/* Figure out how many whole cache lines (64-bytes) to copy */
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movl %edx, %ecx
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andl $63, %edx
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shrl $6, %ecx
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jz .L_no_whole_cache_lines
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/* Loop copying whole cache lines */
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.L_cache_w0: movq (%rsi), %r8
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.L_cache_w1: movq 1*8(%rsi), %r9
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.L_cache_w2: movq 2*8(%rsi), %r10
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.L_cache_w3: movq 3*8(%rsi), %r11
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movq %r8, (%rdi)
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movq %r9, 1*8(%rdi)
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movq %r10, 2*8(%rdi)
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movq %r11, 3*8(%rdi)
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.L_cache_w4: movq 4*8(%rsi), %r8
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.L_cache_w5: movq 5*8(%rsi), %r9
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.L_cache_w6: movq 6*8(%rsi), %r10
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.L_cache_w7: movq 7*8(%rsi), %r11
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movq %r8, 4*8(%rdi)
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movq %r9, 5*8(%rdi)
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movq %r10, 6*8(%rdi)
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movq %r11, 7*8(%rdi)
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leaq 64(%rsi), %rsi
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leaq 64(%rdi), %rdi
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decl %ecx
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jnz .L_cache_w0
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/* Are there any trailing 8-byte words? */
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.L_no_whole_cache_lines:
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movl %edx, %ecx
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andl $7, %edx
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shrl $3, %ecx
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jz .L_no_whole_words
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/* Copy trailing words */
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.L_copy_trailing_words:
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movq (%rsi), %r8
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mov %r8, (%rdi)
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leaq 8(%rsi), %rsi
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leaq 8(%rdi), %rdi
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decl %ecx
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jnz .L_copy_trailing_words
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/* Any trailing bytes? */
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.L_no_whole_words:
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andl %edx, %edx
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jz .L_done_memcpy_trap
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/* Copy trailing bytes */
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movl %edx, %ecx
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.L_copy_trailing_bytes:
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movb (%rsi), %al
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movb %al, (%rdi)
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incq %rsi
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incq %rdi
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decl %ecx
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jnz .L_copy_trailing_bytes
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/* Copy successful. Return true */
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.L_done_memcpy_trap:
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xorq %rax, %rax
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ret
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ENDPROC(memcpy_mcsafe)
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.section .fixup, "ax"
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/* Return false for any failure */
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.L_memcpy_mcsafe_fail:
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mov $1, %rax
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ret
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.previous
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_ASM_EXTABLE_FAULT(.L_copy_leading_bytes, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_cache_w0, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_cache_w1, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_cache_w3, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_cache_w3, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_cache_w4, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_cache_w5, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_cache_w6, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_cache_w7, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_copy_trailing_words, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_copy_trailing_bytes, .L_memcpy_mcsafe_fail)
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#endif
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