Date: Thu, 28 Dec 2023 17:20:16 GMT From: Robert Clausecker <fuz@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 1347ec5d5845 - stable/14 - lib/libc/amd64/string: add timingsafe_bcmp(3) scalar, baseline implementations Message-ID: <202312281720.3BSHKGnS081402@gitrepo.freebsd.org>
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The branch stable/14 has been updated by fuz: URL: https://cgit.FreeBSD.org/src/commit/?id=1347ec5d5845886a9da0903700f54110f0241b8a commit 1347ec5d5845886a9da0903700f54110f0241b8a Author: Robert Clausecker <fuz@FreeBSD.org> AuthorDate: 2023-08-30 15:37:26 +0000 Commit: Robert Clausecker <fuz@FreeBSD.org> CommitDate: 2023-12-28 17:02:41 +0000 lib/libc/amd64/string: add timingsafe_bcmp(3) scalar, baseline implementations Very straightforward and similar to memcmp(3). The code has been written to use only instructions specified as having data operand independent timing by Intel. Sponsored by: The FreeBSD Foundation Approved by: security (cperciva) Differential Revision: https://reviews.freebsd.org/D41673 (cherry picked from commit 76c2b331bcd9f73c5c8c43a06e328fa0c7b8c39a) --- lib/libc/amd64/string/Makefile.inc | 3 +- lib/libc/amd64/string/timingsafe_bcmp.S | 232 ++++++++++++++++++++++++++++++++ 2 files changed, 234 insertions(+), 1 deletion(-) diff --git a/lib/libc/amd64/string/Makefile.inc b/lib/libc/amd64/string/Makefile.inc index 73973a6d69de..fc420de0450e 100644 --- a/lib/libc/amd64/string/Makefile.inc +++ b/lib/libc/amd64/string/Makefile.inc @@ -15,4 +15,5 @@ MDSRCS+= \ strcspn.S \ strlen.S \ strnlen.c \ - strspn.S + strspn.S \ + timingsafe_bcmp.S diff --git a/lib/libc/amd64/string/timingsafe_bcmp.S b/lib/libc/amd64/string/timingsafe_bcmp.S new file mode 100644 index 000000000000..c003da2ea9a7 --- /dev/null +++ b/lib/libc/amd64/string/timingsafe_bcmp.S @@ -0,0 +1,232 @@ +/*- + * Copyright (c) 2023 The FreeBSD Foundation + * + * This software was developed by Robert Clausecker <fuz@FreeBSD.org> + * under sponsorship from the FreeBSD Foundation. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE + */ + +#include <machine/asm.h> + +#include "amd64_archlevel.h" + +#define ALIGN_TEXT .p2align 4,0x90 /* 16-byte alignment, nop filled */ + +ARCHFUNCS(timingsafe_bcmp) + ARCHFUNC(timingsafe_bcmp, scalar) + ARCHFUNC(timingsafe_bcmp, baseline) +ENDARCHFUNCS(timingsafe_bcmp) + +ARCHENTRY(timingsafe_bcmp, scalar) + cmp $16, %rdx # at least 17 bytes to process? + ja .Lgt16 + + cmp $8, %edx # at least 9 bytes to process? + ja .L0916 + + cmp $4, %edx # at least 5 bytes to process? + ja .L0508 + + cmp $2, %edx # at least 3 bytes to process? + ja .L0304 + + test %edx, %edx # buffer empty? + jnz .L0102 + + xor %eax, %eax # empty buffer always matches + ret + +.L0102: movzbl (%rdi), %eax # load 1--2 bytes from first buffer + movzbl -1(%rdi, %rdx, 1), %ecx + xor (%rsi), %al # xor in second buffer + xor -1(%rsi, %rdx, 1), %cl + or %ecx, %eax # mismatch in any of the two? + ret + +.L0304: movzwl (%rdi), %eax + movzwl -2(%rdi, %rdx, 1), %ecx + xor (%rsi), %ax + xor -2(%rsi, %rdx, 1), %cx + or %ecx, %eax + ret + +.L0508: mov (%rdi), %eax + mov -4(%rdi, %rdx, 1), %ecx + xor (%rsi), %eax + xor -4(%rsi, %rdx, 1), %ecx + or %ecx, %eax + ret + +.L0916: mov (%rdi), %rax + mov -8(%rdi, %rdx, 1), %rcx + xor (%rsi), %rax + xor -8(%rsi, %rdx, 1), %rcx + or %rcx, %rax + setnz %al # ensure EAX nonzero even if only + ret # high bits of RAX were set + + /* more than 16 bytes: process buffer in a loop */ +.Lgt16: mov (%rdi), %rax # process first 16 bytes + mov 8(%rdi), %r9 + mov $32, %ecx + xor (%rsi), %rax + xor 8(%rsi), %r9 + or %r9, %rax + + cmp %rdx, %rcx # enough left for a full iteration? + jae .Ltail + + /* main loop processing 16 bytes per iteration */ + ALIGN_TEXT +0: mov -16(%rdi, %rcx, 1), %r8 + mov -8(%rdi, %rcx, 1), %r9 + xor -16(%rsi, %rcx, 1), %r8 + xor -8(%rsi, %rcx, 1), %r9 + add $16, %rcx + or %r9, %r8 + or %r8, %rax + + cmp %rdx, %rcx + jb 0b + + /* process last 16 bytes */ +.Ltail: mov -16(%rdi, %rdx, 1), %r8 + mov -8(%rdi, %rdx, 1), %r9 + xor -16(%rsi, %rdx, 1), %r8 + xor -8(%rsi, %rdx, 1), %r9 + or %r9, %r8 + or %r8, %rax + setnz %al + ret +ARCHEND(timingsafe_bcmp, scalar) + +ARCHENTRY(timingsafe_bcmp, baseline) + cmp $32, %rdx # at least 33 bytes to process? + ja .Lgt32b + + cmp $16, %edx # at least 17 bytes to process? + ja .L1732b + + cmp $8, %edx # at least 9 bytes to process? + ja .L0916b + + cmp $4, %edx # at least 5 bytes to process? + ja .L0508b + + cmp $2, %edx # at least 3 bytes to process? + ja .L0304b + + test %edx, %edx # buffer empty? + jnz .L0102b + + xor %eax, %eax # empty buffer always matches + ret + +.L0102b: + movzbl (%rdi), %eax # load 1--2 bytes from first buffer + movzbl -1(%rdi, %rdx, 1), %ecx + xor (%rsi), %al # xor in second buffer + xor -1(%rsi, %rdx, 1), %cl + or %ecx, %eax # mismatch in any of the two? + ret + +.L0304b: + movzwl (%rdi), %eax + movzwl -2(%rdi, %rdx, 1), %ecx + xor (%rsi), %ax + xor -2(%rsi, %rdx, 1), %cx + or %ecx, %eax + ret + +.L0508b: + mov (%rdi), %eax + mov -4(%rdi, %rdx, 1), %ecx + xor (%rsi), %eax + xor -4(%rsi, %rdx, 1), %ecx + or %ecx, %eax + ret + +.L0916b: + mov (%rdi), %rax + mov -8(%rdi, %rdx, 1), %rcx + xor (%rsi), %rax + xor -8(%rsi, %rdx, 1), %rcx + or %rcx, %rax + setnz %al # ensure EAX nonzero even if only + ret # high bits of RAX were set + +.L1732b: + movdqu (%rdi), %xmm0 + movdqu (%rsi), %xmm2 + movdqu -16(%rdi, %rdx, 1), %xmm1 + movdqu -16(%rsi, %rdx, 1), %xmm3 + pcmpeqb %xmm2, %xmm0 + pcmpeqb %xmm3, %xmm1 + pand %xmm1, %xmm0 + pmovmskb %xmm0, %eax # 1 where equal + xor $0xffff, %eax # 1 where not equal + ret + + /* more than 32 bytes: process buffer in a loop */ +.Lgt32b: + movdqu (%rdi), %xmm4 + movdqu (%rsi), %xmm2 + movdqu 16(%rdi), %xmm1 + movdqu 16(%rsi), %xmm3 + mov $64, %ecx + pcmpeqb %xmm2, %xmm4 + pcmpeqb %xmm3, %xmm1 + pand %xmm1, %xmm4 + cmp %rdx, %rcx # enough left for a full iteration? + jae .Ltailb + + /* main loop processing 32 bytes per iteration */ + ALIGN_TEXT +0: movdqu -32(%rdi, %rcx, 1), %xmm0 + movdqu -32(%rsi, %rcx, 1), %xmm2 + movdqu -16(%rdi, %rcx, 1), %xmm1 + movdqu -16(%rsi, %rcx, 1), %xmm3 + add $32, %rcx + pcmpeqb %xmm2, %xmm0 + pcmpeqb %xmm3, %xmm1 + pand %xmm1, %xmm0 + pand %xmm0, %xmm4 + cmp %rdx, %rcx + jb 0b + + /* process last 32 bytes */ +.Ltailb: + movdqu -32(%rdi, %rdx, 1), %xmm0 + movdqu -32(%rsi, %rdx, 1), %xmm2 + movdqu -16(%rdi, %rdx, 1), %xmm1 + movdqu -16(%rsi, %rdx, 1), %xmm3 + pcmpeqb %xmm2, %xmm0 + pcmpeqb %xmm3, %xmm1 + pand %xmm1, %xmm0 + pand %xmm4, %xmm0 + pmovmskb %xmm0, %eax + xor $0xffff, %eax + ret +ARCHEND(timingsafe_bcmp, baseline) + + .section .note.GNU-stack,"",%progbits
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