From: Goran Ferenc goran.ferenc@imgtec.com
[ Upstream commit 180902e08f051f72c89ffa366f4e4f7a8e9c753e ]
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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- 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 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; }