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Make LD_HWCAP_MASK usable for static binaries

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The LD_HWCAP_MASK environment variable was ignored in static binaries,
which is inconsistent with the behaviour of dynamically linked
binaries.  This seems to have been because of the inability of
ld_hwcap_mask being read early enough to influence anything but now
that it is in tunables, the mask is usable in static binaries as well.

This feature is important for aarch64, which relies on HWCAP_CPUID
being masked out to disable multiarch.  A sanity test on x86_64 shows
that there are no failures.  Likewise for aarch64.

	* elf/dl-hwcaps.h [HAVE_TUNABLES]: Always read hwcap_mask.
	* sysdeps/sparc/sparc32/dl-machine.h [HAVE_TUNABLES]:
	Likewise.
	* sysdeps/x86/cpu-features.c (init_cpu_features): Always set
	up hwcap and hwcap_mask.
This commit is contained in:
Siddhesh Poyarekar
2017-05-23 00:59:16 +05:30
parent f82e9672ad
commit 511c5a1087
4 changed files with 18 additions and 15 deletions
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6
ChangeLog
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@ -1,5 +1,11 @@
2017-06-07 Siddhesh Poyarekar <siddhesh@sourceware.org> 2017-06-07 Siddhesh Poyarekar <siddhesh@sourceware.org>
* elf/dl-hwcaps.h [HAVE_TUNABLES]: Always read hwcap_mask.
* sysdeps/sparc/sparc32/dl-machine.h [HAVE_TUNABLES]:
Likewise.
* sysdeps/x86/cpu-features.c (init_cpu_features): Always set
up hwcap and hwcap_mask.
* sysdeps/unix/sysv/linux/aarch64/cpu-features.c * sysdeps/unix/sysv/linux/aarch64/cpu-features.c
(init_cpu_features): Use glibc.tune.hwcap_mask. (init_cpu_features): Use glibc.tune.hwcap_mask.
* sysdeps/unix/sysv/linux/aarch64/dl-procinfo.h: New file. * sysdeps/unix/sysv/linux/aarch64/dl-procinfo.h: New file.

17
elf/dl-hwcaps.h
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@ -18,14 +18,13 @@
#include <elf/dl-tunables.h> #include <elf/dl-tunables.h>
#ifdef SHARED #if HAVE_TUNABLES
# if HAVE_TUNABLES # define GET_HWCAP_MASK() TUNABLE_GET (glibc, tune, hwcap_mask, uint64_t, NULL)
# define GET_HWCAP_MASK() \
TUNABLE_GET (glibc, tune, hwcap_mask, uint64_t, NULL)
# else
# define GET_HWCAP_MASK() GLRO(dl_hwcap_mask)
# endif
#else #else
/* HWCAP_MASK is ignored in static binaries. */ # ifdef SHARED
# define GET_HWCAP_MASK() (0) # define GET_HWCAP_MASK() GLRO(dl_hwcap_mask)
# else
/* HWCAP_MASK is ignored in static binaries when built without tunables. */
# define GET_HWCAP_MASK() (0)
# endif
#endif #endif

2
sysdeps/sparc/sparc32/dl-machine.h
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@ -37,7 +37,7 @@ elf_machine_matches_host (const Elf32_Ehdr *ehdr)
return 1; return 1;
else if (ehdr->e_machine == EM_SPARC32PLUS) else if (ehdr->e_machine == EM_SPARC32PLUS)
{ {
#ifdef SHARED #if HAVE_TUNABLES || defined SHARED
uint64_t hwcap_mask = GET_HWCAP_MASK(); uint64_t hwcap_mask = GET_HWCAP_MASK();
return GLRO(dl_hwcap) & hwcap_mask & HWCAP_SPARC_V9; return GLRO(dl_hwcap) & hwcap_mask & HWCAP_SPARC_V9;
#else #else

8
sysdeps/x86/cpu-features.c
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@ -312,17 +312,16 @@ no_cpuid:
cpu_features->model = model; cpu_features->model = model;
cpu_features->kind = kind; cpu_features->kind = kind;
#if IS_IN (rtld)
/* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86. */ /* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86. */
GLRO(dl_platform) = NULL; GLRO(dl_platform) = NULL;
GLRO(dl_hwcap) = 0; GLRO(dl_hwcap) = 0;
#if !HAVE_TUNABLES #if !HAVE_TUNABLES && defined SHARED
/* The glibc.tune.hwcap_mask tunable is initialized already, so no need to do /* The glibc.tune.hwcap_mask tunable is initialized already, so no need to do
this. */ this. */
GLRO(dl_hwcap_mask) = HWCAP_IMPORTANT; GLRO(dl_hwcap_mask) = HWCAP_IMPORTANT;
#endif #endif
# ifdef __x86_64__ #ifdef __x86_64__
if (cpu_features->kind == arch_kind_intel) if (cpu_features->kind == arch_kind_intel)
{ {
if (CPU_FEATURES_ARCH_P (cpu_features, AVX512F_Usable) if (CPU_FEATURES_ARCH_P (cpu_features, AVX512F_Usable)
@ -352,7 +351,7 @@ no_cpuid:
&& CPU_FEATURES_CPU_P (cpu_features, POPCNT)) && CPU_FEATURES_CPU_P (cpu_features, POPCNT))
GLRO(dl_platform) = "haswell"; GLRO(dl_platform) = "haswell";
} }
# else #else
if (CPU_FEATURES_CPU_P (cpu_features, SSE2)) if (CPU_FEATURES_CPU_P (cpu_features, SSE2))
GLRO(dl_hwcap) |= HWCAP_X86_SSE2; GLRO(dl_hwcap) |= HWCAP_X86_SSE2;
@ -360,6 +359,5 @@ no_cpuid:
GLRO(dl_platform) = "i686"; GLRO(dl_platform) = "i686";
else if (CPU_FEATURES_ARCH_P (cpu_features, I586)) else if (CPU_FEATURES_ARCH_P (cpu_features, I586))
GLRO(dl_platform) = "i586"; GLRO(dl_platform) = "i586";
# endif
#endif #endif
} }