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Commit 180902e0 authored by Goran Ferenc's avatar Goran Ferenc Committed by Ralf Baechle
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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 <goran.ferenc@imgtec.com>
Signed-off-by: default avatarMiodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: default avatarAleksandar 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: default avatarRalf Baechle <ralf@linux-mips.org>
parent 8ec7f15b

arch/mips/vdso/gettimeofday.c

+22 −3
Original line number Diff line number Diff line
@@ -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;

}