From 72f50245d018af0c31b38dec83c557a4e5dd1ea8 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 31 Jul 2019 00:26:16 -0400 Subject: [PATCH] clock_gettime: add time64 syscall support, decouple 32-bit time_t the time64 syscall has to be used if time_t is 64-bit, since there's no way of knowing before making a syscall whether the result will fit in 32 bits, and the 32-bit syscalls do not report overflow as an error. on 64-bit archs, there is no change to the code after preprocessing. on current 32-bit archs, the result is now read from the kernel through long[2] array, then copied into the timespec, to remove the assumption that time_t is the same as long. vdso clock_gettime is still used in place of a syscall if available. 32-bit archs with 64-bit time_t must use the time64 version of the vdso function; if it's not available, performance will significantly suffer. support for both vdso functions could be added, but would break the ability to move a long-lived process from a pre-time64 kernel to one that can outlast Y2038 with checkpoint/resume, at least without added hacks to identify that the 32-bit function is no longer usable and stop using it (e.g. by seeing negative tv_sec). this possibility may be explored in future work on the function. --- src/time/clock_gettime.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/src/time/clock_gettime.c b/src/time/clock_gettime.c index 8fd1b8f5..46083759 100644 --- a/src/time/clock_gettime.c +++ b/src/time/clock_gettime.c @@ -40,6 +40,24 @@ int __clock_gettime(clockid_t clk, struct timespec *ts) } #endif +#ifdef SYS_clock_gettime64 + if (sizeof(time_t) > 4) + r = __syscall(SYS_clock_gettime64, clk, ts); + if (SYS_clock_gettime == SYS_clock_gettime64 || r!=-ENOSYS) + return __syscall_ret(r); + long ts32[2]; + r = __syscall(SYS_clock_gettime, clk, ts32); + if (r==-ENOSYS && clk==CLOCK_REALTIME) { + r = __syscall(SYS_gettimeofday, ts32, 0); + ts32[1] *= 1000; + } + if (!r) { + ts->tv_sec = ts32[0]; + ts->tv_nsec = ts32[1]; + return r; + } + return __syscall_ret(r); +#else r = __syscall(SYS_clock_gettime, clk, ts); if (r == -ENOSYS) { if (clk == CLOCK_REALTIME) { @@ -50,6 +68,7 @@ int __clock_gettime(clockid_t clk, struct timespec *ts) r = -EINVAL; } return __syscall_ret(r); +#endif } weak_alias(__clock_gettime, clock_gettime); -- 2.25.1