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957c61cbbf
This change upgrades to GCC 12.3 and GNU binutils 2.42. The GNU linker appears to have changed things so that only a single de-duplicated str table is present in the binary, and it gets placed wherever the linker wants, regardless of what the linker script says. To cope with that we need to stop using .ident to embed licenses. As such, this change does significant work to revamp how third party licenses are defined in the codebase, using `.section .notice,"aR",@progbits`. This new GCC 12.3 toolchain has support for GNU indirect functions. It lets us support __target_clones__ for the first time. This is used for optimizing the performance of libc string functions such as strlen and friends so far on x86, by ensuring AVX systems favor a second codepath that uses VEX encoding. It shaves some latency off certain operations. It's a useful feature to have for scientific computing for the reasons explained by the test/libcxx/openmp_test.cc example which compiles for fifteen different microarchitectures. Thanks to the upgrades, it's now also possible to use newer instruction sets, such as AVX512FP16, VNNI. Cosmo now uses the %gs register on x86 by default for TLS. Doing it is helpful for any program that links `cosmo_dlopen()`. Such programs had to recompile their binaries at startup to change the TLS instructions. That's not great, since it means every page in the executable needs to be faulted. The work of rewriting TLS-related x86 opcodes, is moved to fixupobj.com instead. This is great news for MacOS x86 users, since we previously needed to morph the binary every time for that platform but now that's no longer necessary. The only platforms where we need fixup of TLS x86 opcodes at runtime are now Windows, OpenBSD, and NetBSD. On Windows we morph TLS to point deeper into the TIB, based on a TlsAlloc assignment, and on OpenBSD/NetBSD we morph %gs back into %fs since the kernels do not allow us to specify a value for the %gs register. OpenBSD users are now required to use APE Loader to run Cosmo binaries and assimilation is no longer possible. OpenBSD kernel needs to change to allow programs to specify a value for the %gs register, or it needs to stop marking executable pages loaded by the kernel as mimmutable(). This release fixes __constructor__, .ctor, .init_array, and lastly the .preinit_array so they behave the exact same way as glibc. We no longer use hex constants to define math.h symbols like M_PI.
96 lines
5.3 KiB
C
96 lines
5.3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2014 Google Inc. │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/limits.h"
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#include "libc/str/str.h"
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__notice(timingsafe_memcmp_notice, "\
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timingsafe_memcmp (ISC License)\n\
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Copyright 2014 Google Inc.");
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/**
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* Lexicographically compares the first 𝑛 bytes in 𝑝 and 𝑞.
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*
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* The following expression:
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*
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* timingsafe_memcmp(p, q, n)
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*
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* Is functionally equivalent to:
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*
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* MAX(-1, MIN(1, memcmp(p, q, n)))
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*
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* Running time is independent of the byte sequences compared, making
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* this safe to use for comparing secret values such as cryptographic
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* MACs. In contrast, memcmp() may short-circuit after finding the first
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* differing byte.
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*
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* timingsafe_memcmp n=0 661 picoseconds
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* timingsafe_memcmp n=1 1 ns/byte 590 mb/s
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* timingsafe_memcmp n=2 1 ns/byte 738 mb/s
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* timingsafe_memcmp n=3 1 ns/byte 805 mb/s
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* timingsafe_memcmp n=4 1 ns/byte 843 mb/s
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* timingsafe_memcmp n=5 1 ns/byte 922 mb/s
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* timingsafe_memcmp n=6 1 ns/byte 932 mb/s
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* timingsafe_memcmp n=7 1 ns/byte 939 mb/s
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* timingsafe_memcmp n=8 992 ps/byte 984 mb/s
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* timingsafe_memcmp n=9 992 ps/byte 984 mb/s
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* timingsafe_memcmp n=15 926 ps/byte 1,054 mb/s
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* timingsafe_memcmp n=16 950 ps/byte 1,026 mb/s
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* timingsafe_memcmp n=17 933 ps/byte 1,045 mb/s
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* timingsafe_memcmp n=31 896 ps/byte 1,089 mb/s
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* timingsafe_memcmp n=32 888 ps/byte 1,098 mb/s
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* timingsafe_memcmp n=33 972 ps/byte 1,004 mb/s
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* timingsafe_memcmp n=80 913 ps/byte 1,068 mb/s
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* timingsafe_memcmp n=128 891 ps/byte 1,095 mb/s
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* timingsafe_memcmp n=256 873 ps/byte 1,118 mb/s
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* timingsafe_memcmp n=16384 858 ps/byte 1,138 mb/s
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* timingsafe_memcmp n=32768 856 ps/byte 1,140 mb/s
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* timingsafe_memcmp n=131072 857 ps/byte 1,138 mb/s
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* bcmp ne n=256 3 ps/byte 246 gb/s
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* bcmp eq n=256 32 ps/byte 30,233 mb/s
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* memcmp ne n=256 3 ps/byte 246 gb/s
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* memcmp eq n=256 31 ps/byte 31,493 mb/s
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* timingsafe_bcmp ne n=256 27 ps/byte 35,992 mb/s
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* timingsafe_bcmp eq n=256 27 ps/byte 35,992 mb/s
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* timingsafe_memcmp ne n=256 877 ps/byte 1,113 mb/s
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* timingsafe_memcmp eq n=256 883 ps/byte 1,105 mb/s
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*
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* @note each byte is interpreted as unsigned char
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* @return -1, 0, or 1 based on comparison
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* @see timingsafe_bcmp() it's 100x faster
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* @asyncsignalsafe
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*/
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int timingsafe_memcmp(const void *p, const void *q, size_t n) {
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const unsigned char *p1 = p, *p2 = q;
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size_t i;
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int res = 0, done = 0;
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for (i = 0; i < n; i++) {
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/* lt is -1 if p1[i] < p2[i]; else 0. */
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int lt = (p1[i] - p2[i]) >> CHAR_BIT;
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/* gt is -1 if p1[i] > p2[i]; else 0. */
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int gt = (p2[i] - p1[i]) >> CHAR_BIT;
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/* cmp is 1 if p1[i] > p2[i]; -1 if p1[i] < p2[i]; else 0. */
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int cmp = lt - gt;
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/* set res = cmp if !done. */
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res |= cmp & ~done;
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/* set done if p1[i] != p2[i]. */
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done |= lt | gt;
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}
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return res;
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}
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