mirror of
https://sourceware.org/git/glibc.git
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289 lines
9.2 KiB
C
289 lines
9.2 KiB
C
/* x86 CPU feature tuning.
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This file is part of the GNU C Library.
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Copyright (C) 2017-2025 Free Software Foundation, Inc.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#define TUNABLE_NAMESPACE cpu
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#include <stdbool.h>
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#include <stdint.h>
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#include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
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#include <elf/dl-tunables.h>
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#include <string.h>
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#include <cpu-features.h>
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#include <ldsodefs.h>
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#include <dl-tunables-parse.h>
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#include <dl-symbol-redir-ifunc.h>
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#define CHECK_GLIBC_IFUNC_CPU_OFF(f, cpu_features, name, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (tunable_str_comma_strcmp_cte (&f, #name)) \
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{ \
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CPU_FEATURE_UNSET (cpu_features, name) \
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break; \
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}
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#define CHECK_GLIBC_IFUNC_CPU_BOTH(f, cpu_features, name, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (tunable_str_comma_strcmp_cte (&f, #name)) \
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{ \
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if (f.disable) \
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CPU_FEATURE_UNSET (cpu_features, name) \
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else \
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CPU_FEATURE_SET_ACTIVE (cpu_features, name) \
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break; \
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}
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/* Disable a preferred feature NAME. We don't enable a preferred feature
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which isn't available. */
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#define CHECK_GLIBC_IFUNC_PREFERRED_OFF(f, cpu_features, name, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (tunable_str_comma_strcmp_cte (&f, #name)) \
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{ \
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cpu_features->preferred[index_arch_##name] \
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&= ~bit_arch_##name; \
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break; \
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}
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/* Enable/disable a preferred feature NAME. */
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#define CHECK_GLIBC_IFUNC_PREFERRED_BOTH(f, cpu_features, name, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (tunable_str_comma_strcmp_cte (&f, #name)) \
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{ \
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if (f.disable) \
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cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name; \
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else \
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cpu_features->preferred[index_arch_##name] |= bit_arch_##name; \
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break; \
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}
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/* Enable/disable a preferred feature NAME. Enable a preferred feature
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only if the feature NEED is usable. */
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#define CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH(f, cpu_features, name, \
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need, len) \
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_Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \
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if (tunable_str_comma_strcmp_cte (&f, #name)) \
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{ \
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if (f.disable) \
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cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name; \
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else if (CPU_FEATURE_USABLE_P (cpu_features, need)) \
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cpu_features->preferred[index_arch_##name] |= bit_arch_##name; \
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break; \
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}
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attribute_hidden
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void
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TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
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{
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/* The current IFUNC selection is based on microbenchmarks in glibc.
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It should give the best performance for most workloads. But other
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choices may have better performance for a particular workload or on
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the hardware which wasn't available when the selection was made.
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The environment variable:
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GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,-zzz,....
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can be used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature
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yyy and zzz, where the feature name is case-sensitive and has to
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match the ones in cpu-features.h. It can be used by glibc developers
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to tune for a new processor or override the IFUNC selection to
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improve performance for a particular workload.
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NOTE: the IFUNC selection may change over time. Please check all
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multiarch implementations when experimenting. */
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struct cpu_features *cpu_features = &GLRO(dl_x86_cpu_features);
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struct tunable_str_comma_state_t ts;
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tunable_str_comma_init (&ts, valp);
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struct tunable_str_comma_t n;
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while (tunable_str_comma_next (&ts, &n))
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{
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switch (n.len)
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{
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default:
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break;
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case 3:
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if (n.disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CX8, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, HTT, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, IBT, 3);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, RTM, 3);
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}
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break;
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case 4:
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if (n.disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX2, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI1, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI2, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CMOV, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, ERMS, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA4, 4);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE2, 4);
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CHECK_GLIBC_IFUNC_PREFERRED_OFF (n, cpu_features, I586, 4);
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CHECK_GLIBC_IFUNC_PREFERRED_OFF (n, cpu_features, I686, 4);
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}
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break;
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case 5:
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{
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CHECK_GLIBC_IFUNC_CPU_BOTH (n, cpu_features, SHSTK, 5);
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}
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if (n.disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, LZCNT, 5);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, MOVBE, 5);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSSE3, 5);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, XSAVE, 5);
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}
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break;
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case 6:
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if (n.disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, POPCNT, 6);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_1, 6);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_2, 6);
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if (memcmp (n.str, "XSAVEC", 6) == 0)
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{
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/* Update xsave_state_size to XSAVE state size. */
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cpu_features->xsave_state_size
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= cpu_features->xsave_state_full_size;
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CPU_FEATURE_UNSET (cpu_features, XSAVEC);
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}
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}
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break;
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case 7:
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if (n.disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512F, 7);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, OSXSAVE, 7);
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}
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break;
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case 8:
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if (n.disable)
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{
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512CD, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512BW, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512DQ, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512ER, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512PF, 8);
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CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512VL, 8);
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}
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Slow_BSF, 8);
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break;
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case 11:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Prefer_ERMS,
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11);
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Prefer_FSRM,
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11);
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Avoid_STOSB,
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11);
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH (n, cpu_features,
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Slow_SSE4_2,
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SSE4_2,
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11);
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}
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break;
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case 15:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Fast_Rep_String, 15);
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}
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break;
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case 16:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, Prefer_No_AVX512, AVX512F, 16);
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}
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break;
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case 18:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Fast_Copy_Backward, 18);
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}
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break;
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case 19:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Fast_Unaligned_Load, 19);
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Fast_Unaligned_Copy, 19);
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}
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break;
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case 20:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, Prefer_No_VZEROUPPER, AVX, 20);
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}
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break;
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case 23:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, AVX_Fast_Unaligned_Load, AVX, 23);
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}
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break;
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case 24:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, MathVec_Prefer_No_AVX512, AVX512F, 24);
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}
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break;
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case 25:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Avoid_Non_Temporal_Memset, 25);
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}
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break;
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case 26:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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(n, cpu_features, Prefer_PMINUB_for_stringop, SSE2, 26);
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}
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break;
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}
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}
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}
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#if CET_ENABLED
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attribute_hidden
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void
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TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *valp)
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{
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if (tunable_strcmp_cte (valp, "on"))
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GL(dl_x86_feature_control).ibt = cet_always_on;
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else if (tunable_strcmp_cte (valp, "off"))
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GL(dl_x86_feature_control).ibt = cet_always_off;
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else if (tunable_strcmp_cte (valp, "permissive"))
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GL(dl_x86_feature_control).ibt = cet_permissive;
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}
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attribute_hidden
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void
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TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *valp)
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{
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if (tunable_strcmp_cte (valp, "on"))
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GL(dl_x86_feature_control).shstk = cet_always_on;
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else if (tunable_strcmp_cte (valp, "off"))
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GL(dl_x86_feature_control).shstk = cet_always_off;
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else if (tunable_strcmp_cte (valp, "permissive"))
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GL(dl_x86_feature_control).shstk = cet_permissive;
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}
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#endif
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