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/Makefile | 6 +++ sysdeps/unix/sysv/linux/clock_gettime.c | 51 ++++++++++++++----- .../unix/sysv/linux/tst-clock_gettime-clobber.c | 57 ++++++++++++++++++++++ sysdeps/unix/sysv/linux/tst-gettimeofday-clobber.c | 37 ++++++++++++++ sysdeps/unix/sysv/linux/tst-time-clobber.c | 36 ++++++++++++++ 5 files changed, 175 insertions(+), 12 deletions(-) create mode 100644 sysdeps/unix/sysv/linux/tst-clock_gettime-clobber.c create mode 100644 sysdeps/unix/sysv/linux/tst-gettimeofday-clobber.c create mode 100644 sysdeps/unix/sysv/linux/tst-time-clobber.c (limited to 'sysdeps') diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile index 8257e5b548..feb8fd4ce1 100644 --- a/sysdeps/unix/sysv/linux/Makefile +++ b/sysdeps/unix/sysv/linux/Makefile @@ -213,6 +213,12 @@ ifeq ($(subdir),time) sysdep_headers += sys/timex.h bits/timex.h sysdep_routines += ntp_gettime ntp_gettimex + +tests += \ + tst-clock_gettime-clobber \ + tst-gettimeofday-clobber \ + tst-time-clobber \ + # tests endif ifeq ($(subdir),signal) 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 diff --git a/sysdeps/unix/sysv/linux/tst-clock_gettime-clobber.c b/sysdeps/unix/sysv/linux/tst-clock_gettime-clobber.c new file mode 100644 index 0000000000..81a32bd15a --- /dev/null +++ b/sysdeps/unix/sysv/linux/tst-clock_gettime-clobber.c @@ -0,0 +1,57 @@ +/* Check that clock_gettime does not clobber errno on success. + Copyright (C) 2021 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include +#include +#include +#include + +static void +test_clock (clockid_t clk) +{ + printf ("info: testing clock: %d\n", (int) clk); + + for (int original_errno = 0; original_errno < 2; ++original_errno) + { + errno = original_errno; + struct timespec ts; + if (clock_gettime (clk, &ts) == 0) + TEST_COMPARE (errno, original_errno); + } +} + +static int +do_test (void) +{ + test_clock (CLOCK_BOOTTIME); + test_clock (CLOCK_BOOTTIME_ALARM); + test_clock (CLOCK_MONOTONIC); + test_clock (CLOCK_MONOTONIC_COARSE); + test_clock (CLOCK_MONOTONIC_RAW); + test_clock (CLOCK_PROCESS_CPUTIME_ID); + test_clock (CLOCK_REALTIME); + test_clock (CLOCK_REALTIME_ALARM); + test_clock (CLOCK_REALTIME_COARSE); +#ifdef CLOCK_TAI + test_clock (CLOCK_TAI); +#endif + test_clock (CLOCK_THREAD_CPUTIME_ID); + return 0; +} + +#include diff --git a/sysdeps/unix/sysv/linux/tst-gettimeofday-clobber.c b/sysdeps/unix/sysv/linux/tst-gettimeofday-clobber.c new file mode 100644 index 0000000000..bb9bdb67b0 --- /dev/null +++ b/sysdeps/unix/sysv/linux/tst-gettimeofday-clobber.c @@ -0,0 +1,37 @@ +/* Check that gettimeofday does not clobber errno. + Copyright (C) 2021 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include +#include +#include +#include + +static int +do_test (void) +{ + for (int original_errno = 0; original_errno < 2; ++original_errno) + { + errno = original_errno; + struct timeval tv; + gettimeofday (&tv, NULL); + TEST_COMPARE (errno, original_errno); + } + return 0; +} + +#include diff --git a/sysdeps/unix/sysv/linux/tst-time-clobber.c b/sysdeps/unix/sysv/linux/tst-time-clobber.c new file mode 100644 index 0000000000..ad83be9be8 --- /dev/null +++ b/sysdeps/unix/sysv/linux/tst-time-clobber.c @@ -0,0 +1,36 @@ +/* Check that time does not clobber errno. + Copyright (C) 2021 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include +#include +#include +#include + +static int +do_test (void) +{ + for (int original_errno = 0; original_errno < 2; ++original_errno) + { + errno = original_errno; + time (NULL); + TEST_COMPARE (errno, original_errno); + } + return 0; +} + +#include -- cgit 1.4.1