Commit 180902e0 authored by Goran Ferenc's avatar Goran Ferenc Committed by Ralf Baechle

MIPS: VDSO: Add implementation of clock_gettime() fallback

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: default avatarGoran Ferenc <>
Signed-off-by: default avatarMiodrag Dinic <>
Signed-off-by: default avatarAleksandar Markovic <>
Cc: Douglas Leung <>
Cc: James Hogan <>
Cc: Paul Burton <>
Cc: Petar Jovanovic <>
Cc: Raghu Gandham <>
Patchwork: default avatarRalf Baechle <>
parent 8ec7f15b
......@@ -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) {
......@@ -223,10 +241,11 @@ int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
ret = do_monotonic(ts, data);
ret = -ENOSYS;
/* If we return -ENOSYS libc should fall back to a syscall. */
if (ret)
ret = clock_gettime_fallback(clkid, ts);
return ret;
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