From: Goran Ferenc <goran.ferenc@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Miodrag Dinic <miodrag.dinic@xxxxxxxxxx>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@xxxxxxxxxx>
---
arch/mips/vdso/gettimeofday.c | 25 ++++++++++++++++++++++---
1 file changed, 22 insertions(+), 3 deletions(-)
diff --git a/arch/mips/vdso/gettimeofday.c b/arch/mips/vdso/gettimeofday.c
index fd7d433..5f63375 100644
--- a/arch/mips/vdso/gettimeofday.c
+++ b/arch/mips/vdso/gettimeofday.c
@@ -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;
}
--
2.7.4
