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55d63e7312
Not all CET enabled applications and libraries have been properly tested in CET enabled environments. Some CET enabled applications or libraries will crash or misbehave when CET is enabled. Don't set CET active by default so that all applications and libraries will run normally regardless of whether CET is active or not. Shadow stack can be enabled by $ export GLIBC_TUNABLES=glibc.cpu.hwcaps=SHSTK at run-time if shadow stack can be enabled by kernel. NB: This commit can be reverted if it is OK to enable CET by default for all applications and libraries.
280 lines
9 KiB
C
280 lines
9 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) 2017-2023 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_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 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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