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MIPS: VDSO: Add implementation of clock_gettime() fallback

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This patch adds clock_gettime_fallback() function that wraps assembly
invocation of clock_gettime() syscall using __NR_clock_gettime.

This function is used if pure VDSO implementation of clock_gettime()
does not succeed for any reason. For example, it is called if the
clkid parameter of clock_gettime() is not one of the clkids listed
in the switch-case block of the function __vdso_clock_gettime()
(one such case for clkid is CLOCK_BOOTIME).

If syscall invocation via __NR_clock_gettime fails, register a3 will
be set. So, after the syscall, register a3 is tested and the return
value is negated if it's set.

Signed-off-by: Goran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Cc: Douglas Leung <douglas.leung@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Petar Jovanovic <petar.jovanovic@imgtec.com>
Cc: Raghu Gandham <raghu.gandham@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16639/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Goran Ferenc 2017-06-28 17:55:29 +02:00 committed by Ralf Baechle
parent 8ec7f15b8c
commit 180902e08f
1 changed files with 22 additions and 3 deletions
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25
arch/mips/vdso/gettimeofday.c
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@ -20,6 +20,24 @@
#include <asm/unistd.h>
#include <asm/vdso.h>
static __always_inline long clock_gettime_fallback(clockid_t _clkid,
struct timespec *_ts)
{
register struct timespec *ts asm("a1") = _ts;
register clockid_t clkid asm("a0") = _clkid;
register long ret asm("v0");
register long nr asm("v0") = __NR_clock_gettime;
register long error asm("a3");
asm volatile(
" syscall\n"
: "=r" (ret), "=r" (error)
: "r" (clkid), "r" (ts), "r" (nr)
: "memory");
return error ? -ret : ret;
}
static __always_inline int do_realtime_coarse(struct timespec *ts,
const union mips_vdso_data *data)
{
@ -207,7 +225,7 @@ int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
{
const union mips_vdso_data *data = get_vdso_data();
int ret;
int ret = -1;
switch (clkid) {
case CLOCK_REALTIME_COARSE:
@ -223,10 +241,11 @@ int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
ret = do_monotonic(ts, data);
break;
default:
ret = -ENOSYS;
break;
}
/* If we return -ENOSYS libc should fall back to a syscall. */
if (ret)
ret = clock_gettime_fallback(clkid, ts);
return ret;
}