diff options
Diffstat (limited to 'arch/x86/entry/vdso/vclock_gettime.c')
-rw-r--r-- | arch/x86/entry/vdso/vclock_gettime.c | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c index 9c35dc0a9d64..9f4b1081dee0 100644 --- a/arch/x86/entry/vdso/vclock_gettime.c +++ b/arch/x86/entry/vdso/vclock_gettime.c @@ -29,12 +29,12 @@ extern int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz); extern time_t __vdso_time(time_t *t); #ifdef CONFIG_PARAVIRT_CLOCK -extern u8 pvclock_page +extern u8 pvclock_page[PAGE_SIZE] __attribute__((visibility("hidden"))); #endif #ifdef CONFIG_HYPERV_TSCPAGE -extern u8 hvclock_page +extern u8 hvclock_page[PAGE_SIZE] __attribute__((visibility("hidden"))); #endif @@ -191,13 +191,24 @@ notrace static inline u64 vgetsns(int *mode) if (gtod->vclock_mode == VCLOCK_TSC) cycles = vread_tsc(); + + /* + * For any memory-mapped vclock type, we need to make sure that gcc + * doesn't cleverly hoist a load before the mode check. Otherwise we + * might end up touching the memory-mapped page even if the vclock in + * question isn't enabled, which will segfault. Hence the barriers. + */ #ifdef CONFIG_PARAVIRT_CLOCK - else if (gtod->vclock_mode == VCLOCK_PVCLOCK) + else if (gtod->vclock_mode == VCLOCK_PVCLOCK) { + barrier(); cycles = vread_pvclock(mode); + } #endif #ifdef CONFIG_HYPERV_TSCPAGE - else if (gtod->vclock_mode == VCLOCK_HVCLOCK) + else if (gtod->vclock_mode == VCLOCK_HVCLOCK) { + barrier(); cycles = vread_hvclock(mode); + } #endif else return 0; |