From cb3c90cc4253cc236a4d5669a893562b202570e5 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Wed, 23 May 2018 13:13:05 +0200 Subject: [PATCH] x86: libatomic: Do not assume ELF constructors run before IFUNC resolvers 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 --- libatomic/ChangeLog | 15 +++++++++++++ libatomic/config/x86/host-config.h | 34 ++++++++++++++++++++++++++---- libatomic/config/x86/init.c | 14 +++++++----- 3 files changed, 54 insertions(+), 9 deletions(-) diff --git a/libatomic/ChangeLog b/libatomic/ChangeLog index 82a2e040c6b..dcb1bae089a 100644 --- a/libatomic/ChangeLog +++ b/libatomic/ChangeLog @@ -1,3 +1,18 @@ +2018-05-23 Florian Weimer + + 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 PR testsuite/85106 diff --git a/libatomic/config/x86/host-config.h b/libatomic/config/x86/host-config.h index 4a9ab4a6d94..0b6c33862ec 100644 --- a/libatomic/config/x86/host-config.h +++ b/libatomic/config/x86/host-config.h @@ -25,13 +25,39 @@ #if HAVE_IFUNC #include -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__ diff --git a/libatomic/config/x86/init.c b/libatomic/config/x86/init.c index 8b9ccd3b3de..5a4cf8b0456 100644 --- a/libatomic/config/x86/init.c +++ b/libatomic/config/x86/init.c @@ -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 */ -- 2.30.2