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In <sys/platform/x86.h>, define CPU features as enum instead of using the C preprocessor magic to make it easier to wrap this functionality in other languages. Move the C preprocessor magic to internal header for better GCC codegen when more than one features are checked in a single expression as in x86-64 dl-hwcaps-subdirs.c. 1. Rename COMMON_CPUID_INDEX_XXX to CPUID_INDEX_XXX. 2. Move CPUID_INDEX_MAX to sysdeps/x86/include/cpu-features.h. 3. Remove struct cpu_features and __x86_get_cpu_features from <sys/platform/x86.h>. 4. Add __x86_get_cpuid_feature_leaf to <sys/platform/x86.h> and put it in libc. 5. Make __get_cpu_features() private to glibc. 6. Replace __x86_get_cpu_features(N) with __get_cpu_features(). 7. Add _dl_x86_get_cpu_features to GLIBC_PRIVATE. 8. Use a single enum index for each CPU feature detection. 9. Pass the CPUID feature leaf to __x86_get_cpuid_feature_leaf. 10. Return zero struct cpuid_feature for the older glibc binary with a smaller CPUID_INDEX_MAX [BZ #27104]. 11. Inside glibc, use the C preprocessor magic so that cpu_features data can be loaded just once leading to more compact code for glibc. 256 bits are used for each CPUID leaf. Some leaves only contain a few features. We can add exceptions to such leaves. But it will increase code sizes and it is harder to provide backward/forward compatibilities when new features are added to such leaves in the future. When new leaves are added, _rtld_global_ro offsets will change which leads to race condition during in-place updates. We may avoid in-place updates by 1. Rename the old glibc. 2. Install the new glibc. 3. Remove the old glibc. NB: A function, __x86_get_cpuid_feature_leaf , is used to avoid the copy relocation issue with IFUNC resolver as shown in IFUNC resolver tests.
66 lines
2.2 KiB
C
66 lines
2.2 KiB
C
/* Data structure for x86 CPU features.
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This file is part of the GNU C Library.
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Copyright (C) 2008-2021 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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#ifndef _SYS_PLATFORM_X86_H
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#define _SYS_PLATFORM_X86_H
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#include <features.h>
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#include <stdbool.h>
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#include <bits/platform/x86.h>
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__BEGIN_DECLS
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/* Get a pointer to the CPU feature structure. */
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extern const struct cpuid_feature *__x86_get_cpuid_feature_leaf (unsigned int)
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__attribute__ ((pure));
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static __inline__ _Bool
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x86_cpu_has_feature (unsigned int __index)
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{
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const struct cpuid_feature *__ptr = __x86_get_cpuid_feature_leaf
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(__index / (8 * sizeof (unsigned int) * 4));
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unsigned int __reg
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= __index & (8 * sizeof (unsigned int) * 4 - 1);
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unsigned int __bit = __reg & (8 * sizeof (unsigned int) - 1);
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__reg /= 8 * sizeof (unsigned int);
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return __ptr->cpuid_array[__reg] & (1 << __bit);
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}
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static __inline__ _Bool
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x86_cpu_is_usable (unsigned int __index)
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{
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const struct cpuid_feature *__ptr = __x86_get_cpuid_feature_leaf
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(__index / (8 * sizeof (unsigned int) * 4));
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unsigned int __reg
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= __index & (8 * sizeof (unsigned int) * 4 - 1);
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unsigned int __bit = __reg & (8 * sizeof (unsigned int) - 1);
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__reg /= 8 * sizeof (unsigned int);
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return __ptr->usable_array[__reg] & (1 << __bit);
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}
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/* HAS_CPU_FEATURE evaluates to true if CPU supports the feature. */
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#define HAS_CPU_FEATURE(name) x86_cpu_has_feature (x86_cpu_##name)
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/* CPU_FEATURE_USABLE evaluates to true if the feature is usable. */
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#define CPU_FEATURE_USABLE(name) x86_cpu_is_usable (x86_cpu_##name)
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__END_DECLS
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#endif /* _SYS_PLATFORM_X86_H */
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