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authorGoran Ferenc <goran.ferenc@imgtec.com>2017-06-28 18:55:29 +0300
committerRalf Baechle <ralf@linux-mips.org>2017-06-29 03:42:29 +0300
commit180902e08f051f72c89ffa366f4e4f7a8e9c753e (patch)
tree2230db590022baf0071409ed226b2934ec78fb5f /arch/mips/vdso
parent8ec7f15b8cca4f790df5cdf33f26e2926d4ee2fd (diff)
downloadlinux-180902e08f051f72c89ffa366f4e4f7a8e9c753e.tar.xz
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: 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>
Diffstat (limited to 'arch/mips/vdso')
-rw-r--r--arch/mips/vdso/gettimeofday.c25
1 files changed, 22 insertions, 3 deletions
diff --git a/arch/mips/vdso/gettimeofday.c b/arch/mips/vdso/gettimeofday.c
index fd7d433970bf..5f6337545ee2 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;
}