From patchwork Tue May 7 13:18:41 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lukasz Majewski X-Patchwork-Id: 32582 Received: (qmail 125353 invoked by alias); 7 May 2019 13:19:21 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 125279 invoked by uid 89); 7 May 2019 13:19:21 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-19.7 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 spammy=hour, 1000000000 X-HELO: mail-out.m-online.net From: Lukasz Majewski To: libc-alpha@sourceware.org Cc: Stepan Golosunov , Arnd Bergmann , Paul Eggert , Joseph Myers , Lukasz Majewski Subject: [PATCH v3 4/5] y2038: linux: Provide __clock_settime64 implementation Date: Tue, 7 May 2019 15:18:41 +0200 Message-Id: <20190507131848.30980-5-lukma@denx.de> In-Reply-To: <20190507131848.30980-1-lukma@denx.de> References: <20190414220841.20243-1-lukma@denx.de> <20190507131848.30980-1-lukma@denx.de> This patch provides new __clock_settime64 explicit 64 bit function for setting the time. Moreover, a 32 bit version - __clock_settime has been refactored to internally use __clock_settime64. The __clock_settime is now supposed to be used on systems still supporting 32 bit time - hence the necessary checks and conversion to 64 bit type. After this change it is intrinsically Y2038 safe. The new 64 bit syscall (clock_settime64) available from Linux 5.1+ has been used when applicable on 32 bit systems. The __ASSUME_TIME64_SYSCALLS flag indicates if the Linux kernel provides 64 bit version of clock_settime (i.e. clock_settime64). If this syscall is not provided by the kernel - the 32 bit version of it is executed instead. When working on 32 bit systems without Y2038 time support the clock_settime returns error when one wants to set time with wrong (overflowed) tv_sec value. Moreover, the correctness of tv_nsec is checked. In this patch the internal padding (tv_pad) of struct __timespec64 is left untouched (on 32 bit systems) as Linux kernel ignores upper 32 bits of tv_nsec. The execution path on 64 bit systems has not been changed or affected in any way. Tests: - The code has been tested with x86_64/x86 (native compilation): make PARALLELMFLAGS="-j8" && make xcheck PARALLELMFLAGS="-j8" - 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 on kernels with and without 64 bit time support. No regressions were observed. * include/time.h (__clock_settime64): Add __clock_settime alias according to __TIMESIZE define * sysdeps/unix/sysv/linux/clock_settime.c (__clock_settime): Refactor this function to be used only on 32 bit machines as a wrapper on __clock_settime64. * sysdeps/unix/sysv/linux/clock_settime.c (__clock_settime64): Add * sysdeps/unix/sysv/linux/clock_settime.c (__clock_settime64): Use clock_settime64 kernel syscall (available from 5.1-rc1+ Linux) by 32 bit Y2038 safe systems --- Changes for v3: - Rename __ASSUME_64BIT_TIME to __ASSUME_TIME64_SYSCALLS - Refactor in-code comment (add information regarding Linux kernel ignorance of padding - Do not use __TIMESIZE to select main execution path (for Y2038 systems __TIMESIZE would be changed from 32 to 64 bits at some point to indicate full Y2038 support Changes for v2: - Add support for __ASSUME_64BIT_TIME flag when Linux kernel provides syscalls supporting 64 bit time on 32 bit systems - Provide fallback to 32 bit version of clock_settime when clock_settime64 is not available - Do not copy *tp to timespec - this seems like an overkill as in clock_settime() the 32 bit struct timespec is copied to internal 64 bit struct __timespec64 --- include/time.h | 8 +++++ sysdeps/unix/sysv/linux/clock_settime.c | 53 +++++++++++++++++++++++++++++++-- 2 files changed, 58 insertions(+), 3 deletions(-) diff --git a/include/time.h b/include/time.h index 18587fdd8b..670226df0c 100644 --- a/include/time.h +++ b/include/time.h @@ -127,6 +127,14 @@ extern __time64_t __timegm64 (struct tm *__tp) __THROW; libc_hidden_proto (__timegm64) #endif +#if __TIMESIZE == 64 +# define __clock_settime64 __clock_settime +#else +extern int __clock_settime64 (clockid_t clock_id, + const struct __timespec64 *tp); +libc_hidden_proto (__clock_settime64) +#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. diff --git a/sysdeps/unix/sysv/linux/clock_settime.c b/sysdeps/unix/sysv/linux/clock_settime.c index d837e3019c..084edeaa61 100644 --- a/sysdeps/unix/sysv/linux/clock_settime.c +++ b/sysdeps/unix/sysv/linux/clock_settime.c @@ -19,11 +19,9 @@ #include #include -#include "kernel-posix-cpu-timers.h" - /* Set CLOCK to value TP. */ int -__clock_settime (clockid_t clock_id, const struct timespec *tp) +__clock_settime64 (clockid_t clock_id, const struct __timespec64 *tp) { /* Make sure the time cvalue is OK. */ if (tp->tv_nsec < 0 || tp->tv_nsec >= 1000000000) @@ -32,6 +30,55 @@ __clock_settime (clockid_t clock_id, const struct timespec *tp) return -1; } +#ifdef __ASSUME_TIME64_SYSCALLS +# ifdef __NR_clock_settime64 + /* For Y2038 safe systems with __WORDSIZE==32 and __TIMESIZE==64 + (x86, arm) the glibc exported struct timespec has 64 bit tv_sec, + 32 bit tv_nsec (to be still POSIX compliant -> long tv_nsec ) + and 32 bits of unnamed padding. + + It may happen that due to dynamic allocation the tv_pad, which + corresponds to upper 32 bits of kernel's 64 bit tv_nsec accepted + by syscalls, may not be zero. + + However, the Linux kernel is ignoring those 32 bits (to be more + precise - as of 5.1 - it casts 64 bit tv_nsec to internal's 32 bit + representation) and hence the padding clearing is not needed. */ + int ret = INLINE_SYSCALL_CALL (clock_settime64, clock_id, tp); + if (ret == 0 || errno != ENOSYS) + return ret; +# endif +#endif + +/* For systems supporting 32 bit time only __WORDSIZE==32 and + __TIMESIZE==32 (!=64) the passed struct __timespec64 must be + converted to 32 bit one before invoking Linux syscall. */ +#if __WORDSIZE == 32 && __TIMESIZE != 64 + /* Fall back to syscall supporting 32bit struct timespec. */ + struct timespec ts32; + valid_timespec64_to_timespec (tp, &ts32); + return INLINE_SYSCALL_CALL (clock_settime, clock_id, &ts32); +#else +/* Systems with __WORDSIZE==64 (i.e. x86_64, aarch64) or + __WORDSIZE==32 && __TIMESIZE == 64 (i.e. x32 - special case). */ return INLINE_SYSCALL_CALL (clock_settime, clock_id, tp); +#endif } weak_alias (__clock_settime, clock_settime) + +#if __TIMESIZE != 64 +int +__clock_settime (clockid_t clock_id, const struct timespec *tp) +{ + struct __timespec64 ts64; + + if (! in_time_t_range (tp->tv_sec)) + { + __set_errno (EOVERFLOW); + return -1; + } + + valid_timespec_to_timespec64 (tp, &ts64); + return __clock_settime64 (clock_id, &ts64); +} +#endif