From 72e84d1db22203e01a43268de71ea8669eca2863 Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Sat, 10 Jul 2021 17:03:49 -0300 Subject: Linux: Use 32-bit vDSO for clock_gettime, gettimeofday, time (BZ# 28071) The previous approach defeats the vDSO optimization on older kernels because a failing clock_gettime64 system call is performed on every function call. It also results in a clobbered errno value, exposing an OpenJDK bug (JDK-8270244). This patch fixes by open-code INLINE_VSYSCALL macro and replace all INLINE_SYSCALL_CALL with INTERNAL_SYSCALL_CALLS. Now for __clock_gettime64x, the 64-bit vDSO is used and the 32-bit vDSO is tried before falling back to 64-bit syscalls. The previous code preferred 64-bit syscall for the case where the kernel provides 64-bit time_t syscalls *and* also a 32-bit vDSO (in this case the *64-bit* syscall should be preferable over the vDSO). All architectures that provides 32-bit vDSO (i386, mips, powerpc, s390) modulo sparc; but I am not sure if some kernels versions do provide only 32-bit vDSO while still providing 64-bit time_t syscall. Regardless, for such cases the 64-bit time_t syscall is used if the vDSO returns overflowed 32-bit time_t. Tested on i686-linux-gnu (with a time64 and non-time64 kernel), x86_64-linux-gnu. Built with build-many-glibcs.py. Co-authored-by: Florian Weimer --- sysdeps/unix/sysv/linux/clock_gettime.c | 51 +++++++++++++++++++++++++-------- 1 file changed, 39 insertions(+), 12 deletions(-) (limited to 'sysdeps/unix/sysv/linux/clock_gettime.c') diff --git a/sysdeps/unix/sysv/linux/clock_gettime.c b/sysdeps/unix/sysv/linux/clock_gettime.c index cfe9370455..91df6b3d96 100644 --- a/sysdeps/unix/sysv/linux/clock_gettime.c +++ b/sysdeps/unix/sysv/linux/clock_gettime.c @@ -35,27 +35,54 @@ __clock_gettime64 (clockid_t clock_id, struct __timespec64 *tp) #endif #ifdef HAVE_CLOCK_GETTIME64_VSYSCALL - r = INLINE_VSYSCALL (clock_gettime64, 2, clock_id, tp); -#else - r = INLINE_SYSCALL_CALL (clock_gettime64, clock_id, tp); + int (*vdso_time64) (clockid_t clock_id, struct __timespec64 *tp) + = GLRO(dl_vdso_clock_gettime64); + if (vdso_time64 != NULL) + { + r = INTERNAL_VSYSCALL_CALL (vdso_time64, 2, clock_id, tp); + if (r == 0) + return 0; + return INLINE_SYSCALL_ERROR_RETURN_VALUE (-r); + } #endif - if (r == 0 || errno != ENOSYS) - return r; +#ifdef HAVE_CLOCK_GETTIME_VSYSCALL + int (*vdso_time) (clockid_t clock_id, struct timespec *tp) + = GLRO(dl_vdso_clock_gettime); + if (vdso_time != NULL) + { + struct timespec tp32; + r = INTERNAL_VSYSCALL_CALL (vdso_time, 2, clock_id, &tp32); + if (r == 0 && tp32.tv_sec > 0) + { + *tp = valid_timespec_to_timespec64 (tp32); + return 0; + } + else if (r != 0) + return INLINE_SYSCALL_ERROR_RETURN_VALUE (-r); + + /* Fallback to syscall if the 32-bit time_t vDSO returns overflows. */ + } +#endif + + r = INTERNAL_SYSCALL_CALL (clock_gettime64, clock_id, tp); + if (r == 0) + return 0; + if (r != -ENOSYS) + return INLINE_SYSCALL_ERROR_RETURN_VALUE (-r); #ifndef __ASSUME_TIME64_SYSCALLS /* Fallback code that uses 32-bit support. */ struct timespec tp32; -# ifdef HAVE_CLOCK_GETTIME_VSYSCALL - r = INLINE_VSYSCALL (clock_gettime, 2, clock_id, &tp32); -# else - r = INLINE_SYSCALL_CALL (clock_gettime, clock_id, &tp32); -# endif + r = INTERNAL_SYSCALL_CALL (clock_gettime, clock_id, &tp32); if (r == 0) - *tp = valid_timespec_to_timespec64 (tp32); + { + *tp = valid_timespec_to_timespec64 (tp32); + return 0; + } #endif - return r; + return INLINE_SYSCALL_ERROR_RETURN_VALUE (-r); } #if __TIMESIZE != 64 -- cgit 1.4.1