ARM: 8931/1: Add clock_getres entry point

The generic vDSO library provides an implementation of clock_getres() that
can be leveraged by each architecture.

Add clock_getres() entry point on arm to be on pair with arm64.
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

arch/arm/include/asm/vdso/gettimeofday.h

@@ -12,6 +12,8 @@
 #include <asm/unistd.h>
 #include <uapi/linux/time.h>
 
+#define VDSO_HAS_CLOCK_GETRES		1
+
 extern struct vdso_data *__get_datapage(void);
 
 static __always_inline int gettimeofday_fallback(
@@ -50,6 +52,24 @@ static __always_inline long clock_gettime_fallback(
 	return ret;
 }
 
+static __always_inline int clock_getres_fallback(
+					clockid_t _clkid,
+					struct __kernel_timespec *_ts)
+{
+	register struct __kernel_timespec *ts asm("r1") = _ts;
+	register clockid_t clkid asm("r0") = _clkid;
+	register long ret asm ("r0");
+	register long nr asm("r7") = __NR_clock_getres_time64;
+
+	asm volatile(
+	"       swi #0\n"
+	: "=r" (ret)
+	: "r" (clkid), "r" (ts), "r" (nr)
+	: "memory");
+
+	return ret;
+}
+
 static __always_inline u64 __arch_get_hw_counter(int clock_mode)
 {
 #ifdef CONFIG_ARM_ARCH_TIMER

arch/arm/vdso/vdso.lds.S

@@ -71,6 +71,7 @@ VERSION
 	global:
 		__vdso_clock_gettime;
 		__vdso_gettimeofday;
+		__vdso_clock_getres;
 	local: *;
 	};
 }

arch/arm/vdso/vgettimeofday.c

@@ -19,6 +19,12 @@ int __vdso_gettimeofday(struct __kernel_old_timeval *tv,
 	return __cvdso_gettimeofday(tv, tz);
 }
 
+int __vdso_clock_getres(clockid_t clock_id,
+			struct old_timespec32 *res)
+{
+	return __cvdso_clock_getres_time32(clock_id, res);
+}
+
 /* Avoid unresolved references emitted by GCC */
 
 void __aeabi_unwind_cpp_pr0(void)