/* strcpy/stpcpy checking implementation for x86-64. Copyright (C) 2002-2015 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Andreas Jaeger , 2002. Adopted into checking version by Jakub Jelinek . The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, see . */ #include #include "asm-syntax.h" #ifndef USE_AS_STPCPY_CHK # define STRCPY_CHK __strcpy_chk #endif .text ENTRY (STRCPY_CHK) movq %rsi, %rcx /* Source register. */ andl $7, %ecx /* mask alignment bits */ #ifndef USE_AS_STPCPY_CHK movq %rdi, %r10 /* Duplicate destination pointer. */ #endif jz 5f /* aligned => start loop */ cmpq $8, %rdx /* Check if only few bytes left in destination. */ jb 50f subq $8, %rcx /* We need to align to 8 bytes. */ addq %rcx, %rdx /* Subtract count of stored bytes in the cycle below from destlen. */ /* Search the first bytes directly. */ 0: movb (%rsi), %al /* Fetch a byte */ testb %al, %al /* Is it NUL? */ movb %al, (%rdi) /* Store it */ jz 4f /* If it was NUL, done! */ incq %rsi incq %rdi incl %ecx jnz 0b 5: movq $0xfefefefefefefeff,%r8 cmpq $32, %rdx /* Are there enough bytes in destination for the next unrolled round? */ jb 60f /* If not, avoid the unrolled loop. */ /* Now the sources is aligned. Unfortunatly we cannot force to have both source and destination aligned, so ignore the alignment of the destination. */ .p2align 4 1: /* 1st unroll. */ movq (%rsi), %rax /* Read double word (8 bytes). */ addq $8, %rsi /* Adjust pointer for next word. */ movq %rax, %r9 /* Save a copy for NUL finding. */ addq %r8, %r9 /* add the magic value to the word. We get carry bits reported for each byte which is *not* 0 */ jnc 3f /* highest byte is NUL => return pointer */ xorq %rax, %r9 /* (word+magic)^word */ orq %r8, %r9 /* set all non-carry bits */ incq %r9 /* add 1: if one carry bit was *not* set the addition will not result in 0. */ jnz 3f /* found NUL => return pointer */ movq %rax, (%rdi) /* Write value to destination. */ addq $8, %rdi /* Adjust pointer. */ /* 2nd unroll. */ movq (%rsi), %rax /* Read double word (8 bytes). */ addq $8, %rsi /* Adjust pointer for next word. */ movq %rax, %r9 /* Save a copy for NUL finding. */ addq %r8, %r9 /* add the magic value to the word. We get carry bits reported for each byte which is *not* 0 */ jnc 3f /* highest byte is NUL => return pointer */ xorq %rax, %r9 /* (word+magic)^word */ orq %r8, %r9 /* set all non-carry bits */ incq %r9 /* add 1: if one carry bit was *not* set the addition will not result in 0. */ jnz 3f /* found NUL => return pointer */ movq %rax, (%rdi) /* Write value to destination. */ addq $8, %rdi /* Adjust pointer. */ /* 3rd unroll. */ movq (%rsi), %rax /* Read double word (8 bytes). */ addq $8, %rsi /* Adjust pointer for next word. */ movq %rax, %r9 /* Save a copy for NUL finding. */ addq %r8, %r9 /* add the magic value to the word. We get carry bits reported for each byte which is *not* 0 */ jnc 3f /* highest byte is NUL => return pointer */ xorq %rax, %r9 /* (word+magic)^word */ orq %r8, %r9 /* set all non-carry bits */ incq %r9 /* add 1: if one carry bit was *not* set the addition will not result in 0. */ jnz 3f /* found NUL => return pointer */ movq %rax, (%rdi) /* Write value to destination. */ addq $8, %rdi /* Adjust pointer. */ /* 4th unroll. */ movq (%rsi), %rax /* Read double word (8 bytes). */ addq $8, %rsi /* Adjust pointer for next word. */ movq %rax, %r9 /* Save a copy for NUL finding. */ addq %r8, %r9 /* add the magic value to the word. We get carry bits reported for each byte which is *not* 0 */ jnc 3f /* highest byte is NUL => return pointer */ xorq %rax, %r9 /* (word+magic)^word */ orq %r8, %r9 /* set all non-carry bits */ incq %r9 /* add 1: if one carry bit was *not* set the addition will not result in 0. */ jnz 3f /* found NUL => return pointer */ subq $32, %rdx /* Adjust destlen. */ movq %rax, (%rdi) /* Write value to destination. */ addq $8, %rdi /* Adjust pointer. */ cmpq $32, %rdx /* Are there enough bytes in destination for the next unrolled round? */ jae 1b /* Next iteration. */ 60: cmpq $8, %rdx /* Are there enough bytes in destination for the next unrolled round? */ jb 50f /* Now, copy and check byte by byte. */ movq (%rsi), %rax /* Read double word (8 bytes). */ addq $8, %rsi /* Adjust pointer for next word. */ movq %rax, %r9 /* Save a copy for NUL finding. */ addq %r8, %r9 /* add the magic value to the word. We get carry bits reported for each byte which is *not* 0 */ jnc 3f /* highest byte is NUL => return pointer */ xorq %rax, %r9 /* (word+magic)^word */ orq %r8, %r9 /* set all non-carry bits */ incq %r9 /* add 1: if one carry bit was *not* set the addition will not result in 0. */ jnz 3f /* found NUL => return pointer */ subq $8, %rdx /* Adjust destlen. */ movq %rax, (%rdi) /* Write value to destination. */ addq $8, %rdi /* Adjust pointer. */ jmp 60b /* Next iteration. */ /* Do the last few bytes. %rax contains the value to write. The loop is unrolled twice. */ .p2align 4 3: /* Note that stpcpy needs to return with the value of the NUL byte. */ movb %al, (%rdi) /* 1st byte. */ testb %al, %al /* Is it NUL. */ jz 4f /* yes, finish. */ incq %rdi /* Increment destination. */ movb %ah, (%rdi) /* 2nd byte. */ testb %ah, %ah /* Is it NUL?. */ jz 4f /* yes, finish. */ incq %rdi /* Increment destination. */ shrq $16, %rax /* Shift... */ jmp 3b /* and look at next two bytes in %rax. */ 51: /* Search the bytes directly, checking for overflows. */ incq %rsi incq %rdi decq %rdx jz HIDDEN_JUMPTARGET (__chk_fail) 52: movb (%rsi), %al /* Fetch a byte */ testb %al, %al /* Is it NUL? */ movb %al, (%rdi) /* Store it */ jnz 51b /* If it was NUL, done! */ 4: #ifdef USE_AS_STPCPY_CHK movq %rdi, %rax /* Destination is return value. */ #else movq %r10, %rax /* Source is return value. */ #endif retq 50: testq %rdx, %rdx jnz 52b jmp HIDDEN_JUMPTARGET (__chk_fail) END (STRCPY_CHK)