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x86: libatomic: Do not assume ELF constructors run before IFUNC resolvers

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PR libgcc/60790
	x86: Do not assume ELF constructors run before IFUNC resolvers.
	* config/x86/host-config.h (libat_feat1_ecx, libat_feat1_edx):
	Remove declarations.
	(__libat_feat1, __libat_feat1_init): Declare.
	(FEAT1_REGISTER): Define.
	(load_feat1): New function.
	(IFUNC_COND_1): Adjust.
	* config/x86/init.c (libat_feat1_ecx, libat_feat1_edx)
	(init_cpuid): Remove definitions.
	(__libat_feat1): New variable.
	(__libat_feat1_init): New function.

From-SVN: r260603
This commit is contained in:
Florian Weimer 2018-05-23 13:13:05 +02:00 committed by Florian Weimer
parent 159440699b
commit cb3c90cc42
3 changed files with 54 additions and 9 deletions
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15
libatomic/ChangeLog
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@ -1,3 +1,18 @@
2018-05-23 Florian Weimer <fweimer@redhat.com>
PR libgcc/60790
x86: Do not assume ELF constructors run before IFUNC resolvers.
* config/x86/host-config.h (libat_feat1_ecx, libat_feat1_edx):
Remove declarations.
(__libat_feat1, __libat_feat1_init): Declare.
(FEAT1_REGISTER): Define.
(load_feat1): New function.
(IFUNC_COND_1): Adjust.
* config/x86/init.c (libat_feat1_ecx, libat_feat1_edx)
(init_cpuid): Remove definitions.
(__libat_feat1): New variable.
(__libat_feat1_init): New function.
2018-05-02 Tom de Vries <tom@codesourcery.com>
PR testsuite/85106

34
libatomic/config/x86/host-config.h
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@ -25,13 +25,39 @@
#if HAVE_IFUNC
#include <cpuid.h>
extern unsigned int libat_feat1_ecx HIDDEN;
extern unsigned int libat_feat1_edx HIDDEN;
#ifdef __x86_64__
# define FEAT1_REGISTER ecx
#else
# define FEAT1_REGISTER edx
#endif
/* Value of the CPUID feature register FEAT1_REGISTER for the cmpxchg
bit for IFUNC_COND1 below. */
extern unsigned int __libat_feat1 HIDDEN;
/* Initialize libat_feat1 and return its value. */
unsigned int __libat_feat1_init (void) HIDDEN;
/* Return the value of the relevant feature register for the relevant
cmpxchg bit, or 0 if there is no CPUID support. */
static inline unsigned int
__attribute__ ((const))
load_feat1 (void)
{
/* See the store in __libat_feat1_init. */
unsigned int feat1 = __atomic_load_n (&__libat_feat1, __ATOMIC_RELAXED);
if (feat1 == 0)
/* Assume that initialization has not happened yet. This may get
called repeatedly if the CPU does not have any feature bits at
all. */
feat1 = __libat_feat1_init ();
return feat1;
}
#ifdef __x86_64__
# define IFUNC_COND_1 (libat_feat1_ecx & bit_CMPXCHG16B)
# define IFUNC_COND_1 (load_feat1 () & bit_CMPXCHG16B)
#else
# define IFUNC_COND_1 (libat_feat1_edx & bit_CMPXCHG8B)
# define IFUNC_COND_1 (load_feat1 () & bit_CMPXCHG8B)
#endif
#ifdef __x86_64__

14
libatomic/config/x86/init.c
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@ -26,13 +26,17 @@
#if HAVE_IFUNC
unsigned int libat_feat1_ecx, libat_feat1_edx;
unsigned int __libat_feat1;
static void __attribute__((constructor))
init_cpuid (void)
unsigned int
__libat_feat1_init (void)
{
unsigned int eax, ebx;
__get_cpuid (1, &eax, &ebx, &libat_feat1_ecx, &libat_feat1_edx);
unsigned int eax, ebx, ecx, edx;
FEAT1_REGISTER = 0;
__get_cpuid (1, &eax, &ebx, &ecx, &edx);
/* See the load in load_feat1. */
__atomic_store_n (&__libat_feat1, FEAT1_REGISTER, __ATOMIC_RELAXED);
return FEAT1_REGISTER;
}
#endif /* HAVE_IFUNC */