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a84d116916
Dealing with 'struct timeval' users in the y2038 series is a bit tricky: We have two definitions of timeval that are visible to user space, one comes from glibc (or some other C library), the other comes from linux/time.h. The kernel copy is what we want to be used for a number of structures defined by the kernel itself, e.g. elf_prstatus (used it core dumps), sysinfo and rusage (used in system calls). These generally tend to be used for passing time intervals rather than absolute (epoch-based) times, so they do not suffer from the y2038 overflow. Some of them could be changed to use 64-bit timestamps by creating new system calls, others like the core files cannot easily be changed. An application using these interfaces likely also uses gettimeofday() or other interfaces that use absolute times, and pass 'struct timeval' pointers directly into kernel interfaces, so glibc must redefine their timeval based on a 64-bit time_t when they introduce their y2038-safe interfaces. The only reasonable way forward I see is to remove the 'timeval' definion from the kernel's uapi headers, and change the interfaces that we do not want to (or cannot) duplicate for 64-bit times to use a new __kernel_old_timeval definition instead. This type should be avoided for all new interfaces (those can use 64-bit nanoseconds, or the 64-bit version of timespec instead), and should be used with great care when converting existing interfaces from timeval, to be sure they don't suffer from the y2038 overflow, and only with consensus for the particular user that using __kernel_old_timeval is better than moving to a 64-bit based interface. The structure name is intentionally chosen to not conflict with user space types, and to be ugly enough to discourage its use. Note that ioctl based interfaces that pass a bare 'timeval' pointer cannot change to '__kernel_old_timeval' because the user space source code refers to 'timeval' instead, and we don't want to modify the user space sources if possible. However, any application that relies on a structure to contain an embedded 'timeval' (e.g. by passing a pointer to the member into a function call that expects a timeval pointer) is broken when that structure gets converted to __kernel_old_timeval. I don't see any way around that, and we have to rely on the compiler to produce a warning or compile failure that will alert users when they recompile their sources against a new libc. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Link: https://lkml.kernel.org/r/20180315161739.576085-1-arnd@arndb.de
88 lines
2.1 KiB
C
88 lines
2.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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#ifndef _UAPI_LINUX_TIME_H
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#define _UAPI_LINUX_TIME_H
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#include <linux/types.h>
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#ifndef _STRUCT_TIMESPEC
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#define _STRUCT_TIMESPEC
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struct timespec {
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__kernel_time_t tv_sec; /* seconds */
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long tv_nsec; /* nanoseconds */
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};
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#endif
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struct timeval {
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__kernel_time_t tv_sec; /* seconds */
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__kernel_suseconds_t tv_usec; /* microseconds */
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};
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struct timezone {
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int tz_minuteswest; /* minutes west of Greenwich */
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int tz_dsttime; /* type of dst correction */
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};
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/*
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* Names of the interval timers, and structure
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* defining a timer setting:
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*/
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#define ITIMER_REAL 0
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#define ITIMER_VIRTUAL 1
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#define ITIMER_PROF 2
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struct itimerspec {
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struct timespec it_interval; /* timer period */
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struct timespec it_value; /* timer expiration */
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};
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struct itimerval {
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struct timeval it_interval; /* timer interval */
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struct timeval it_value; /* current value */
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};
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/*
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* legacy timeval structure, only embedded in structures that
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* traditionally used 'timeval' to pass time intervals (not absolute
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* times). Do not add new users. If user space fails to compile
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* here, this is probably because it is not y2038 safe and needs to
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* be changed to use another interface.
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*/
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struct __kernel_old_timeval {
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__kernel_long_t tv_sec;
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__kernel_long_t tv_usec;
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};
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/*
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* The IDs of the various system clocks (for POSIX.1b interval timers):
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*/
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#define CLOCK_REALTIME 0
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#define CLOCK_MONOTONIC 1
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#define CLOCK_PROCESS_CPUTIME_ID 2
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#define CLOCK_THREAD_CPUTIME_ID 3
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#define CLOCK_MONOTONIC_RAW 4
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#define CLOCK_REALTIME_COARSE 5
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#define CLOCK_MONOTONIC_COARSE 6
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#define CLOCK_BOOTTIME 7
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#define CLOCK_REALTIME_ALARM 8
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#define CLOCK_BOOTTIME_ALARM 9
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/*
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* The driver implementing this got removed. The clock ID is kept as a
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* place holder. Do not reuse!
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*/
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#define CLOCK_SGI_CYCLE 10
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#define CLOCK_TAI 11
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#define CLOCK_MONOTONIC_ACTIVE 12
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#define MAX_CLOCKS 16
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#define CLOCKS_MASK (CLOCK_REALTIME | CLOCK_MONOTONIC)
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#define CLOCKS_MONO CLOCK_MONOTONIC
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/*
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* The various flags for setting POSIX.1b interval timers:
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*/
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#define TIMER_ABSTIME 0x01
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#endif /* _UAPI_LINUX_TIME_H */
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