From 177a3d48a1c74d7b2cd6bfd48901519d25a5ecad Mon Sep 17 00:00:00 2001 From: Lukasz Majewski Date: Tue, 15 Oct 2019 17:57:05 +0200 Subject: y2038: linux: Provide __clock_getres64 implementation This patch provides new __clock_getres64 explicit 64 bit function for getting the resolution (precision) of specified clock ID. Moreover, a 32 bit version - __clock_getres has been refactored to internally use __clock_getres64. The __clock_getres is now supposed to be used on systems still supporting 32 bit time (__TIMESIZE != 64) - hence the necessary conversion from 64 bit struct __timespec64 to struct timespec. The new clock_getres_time64 syscall available from Linux 5.1+ has been used, when applicable. On systems which are not supporting clock_getres_time64 (as their clock_getres supports 64 bit time ABI) the vDSO syscall is attempted. On the contrary the non-vDSO syscall is used for clock_getres_time64 as up till now the kernel is not providing such interface. No additional checks (i.e. if tv_nsec value overflow) are performed on values returned via clock_getres{_time64} syscall, as it is assumed that the Linux kernel will either return 0 and provide correct value or error. The check for tv_sec being out of range on systems still supporting 32 bit time (__TIMESIZE != 64) without Y2038 time support is also omitted as it is _very_ unlikely that we would have a timer with resolution which exceeds 32 bit time_t range. Build tests: - The code has been tested on x86_64/x86 (native compilation): make PARALLELMFLAGS="-j8" && make xcheck PARALLELMFLAGS="-j8" - The glibc has been build tested (make PARALLELMFLAGS="-j8") for x86 (i386), x86_64-x32, and armv7 Run-time tests: - Run specific tests on ARM/x86 32bit systems (qemu): https://github.com/lmajewski/meta-y2038 and run tests: https://github.com/lmajewski/y2038-tests/commits/master - Use of cross-test-ssh.sh for ARM (armv7): make PARALLELMFLAGS="-j8" test-wrapper='./cross-test-ssh.sh root@192.168.7.2' xcheck Linux kernel, headers and minimal kernel version for glibc build test matrix: - Linux v5.1 (with clock_getres_time64) and glibc build with v5.1 as minimal kernel version (--enable-kernel="5.1.0") The __ASSUME_TIME64_SYSCALLS flag defined. - Linux v5.1 and default minimal kernel version The __ASSUME_TIME64_SYSCALLS not defined, but kernel supports clock_getres_time64 syscall. - Linux v4.19 (no clock_getres_time64 support) with default minimal kernel version for contemporary glibc This kernel doesn't support clock_getres_time64 syscall, so the fallback to clock_getres is tested. The above tests were performed with Y2038 redirection applied as well as without (so the __TIMESIZE != 64 execution path is checked as well). No regressions were observed. --- include/time.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include') diff --git a/include/time.h b/include/time.h index 1f6507ef5f..de660f7f57 100644 --- a/include/time.h +++ b/include/time.h @@ -133,6 +133,14 @@ extern int __clock_settime64 (clockid_t clock_id, libc_hidden_proto (__clock_settime64) #endif +#if __TIMESIZE == 64 +# define __clock_getres64 __clock_getres +#else +extern int __clock_getres64 (clockid_t clock_id, + struct __timespec64 *tp); +libc_hidden_proto (__clock_getres64); +#endif + /* Compute the `struct tm' representation of T, offset OFFSET seconds east of UTC, and store year, yday, mon, mday, wday, hour, min, sec into *TP. -- cgit v1.2.3