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some preliminaries for vdso clock support

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these changes also make it so clock_gettime(CLOCK_REALTIME, &ts) works
even on pre-2.6 kernels, emulated via the gettimeofday syscall. there
is no cost for the fallback check, as it falls under the error case
that already must be checked for storing the error code in errno, but
which would normally be hidden inside __syscall_ret.
This commit is contained in:
Rich Felker 2011-07-23 23:45:33 -04:00
parent c0fe5b9da9
commit e3eb49321c
3 changed files with 35 additions and 7 deletions
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25
src/time/clock_gettime.c
View File

@ -1,7 +1,28 @@
#include <time.h>
#include <errno.h>
#include <stdint.h>
#include "syscall.h"
#include "libc.h"
int clock_gettime(clockid_t clk, struct timespec *ts)
int __vdso_clock_gettime(clockid_t, struct timespec *) __attribute__((weak));
static int (*cgt)(clockid_t, struct timespec *) = __vdso_clock_gettime;
int __clock_gettime(clockid_t clk, struct timespec *ts)
{
return syscall(SYS_clock_gettime, clk, ts);
int r;
if (cgt) return cgt(clk, ts);
r = __syscall(SYS_clock_gettime, clk, ts);
if (!r) return r;
if (r == -ENOSYS) {
if (clk == CLOCK_REALTIME) {
__syscall(SYS_gettimeofday, clk, ts, 0);
ts->tv_nsec = (int)ts->tv_nsec * 1000;
return 0;
}
r = -EINVAL;
}
errno = -r;
return -1;
}
weak_alias(__clock_gettime, clock_gettime);

7
src/time/gettimeofday.c
View File

@ -1,8 +1,13 @@
#include <time.h>
#include <sys/time.h>
#include "syscall.h"
int gettimeofday(struct timeval *tv, void *tz)
{
__syscall(SYS_gettimeofday, tv, 0);
struct timespec ts;
if (!tv) return 0;
clock_gettime(CLOCK_REALTIME, &ts);
tv->tv_sec = ts.tv_sec;
tv->tv_usec = (int)ts.tv_nsec / 1000;
return 0;
}

10
src/time/time.c
View File

@ -2,10 +2,12 @@
#include <sys/time.h>
#include "syscall.h"
int __clock_gettime(clockid_t, struct timespec *);
time_t time(time_t *t)
{
struct timeval tv;
__syscall(SYS_gettimeofday, &tv, 0);
if (t) *t = tv.tv_sec;
return tv.tv_sec;
struct timespec ts;
__clock_gettime(CLOCK_REALTIME, &ts);
if (t) *t = ts.tv_sec;
return ts.tv_sec;
}