powerpc/vdso: Provide __kernel_clock_gettime64() on vdso32

Provides __kernel_clock_gettime64() on vdso32. This is the
64 bits version of __kernel_clock_gettime() which is
y2038 compliant.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201126131006.2431205-9-mpe@ellerman.id.au

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

@@ -187,6 +187,8 @@ int __c_kernel_clock_getres(clockid_t clock_id, struct __kernel_timespec *res,
 #else
 int __c_kernel_clock_gettime(clockid_t clock, struct old_timespec32 *ts,
 			     const struct vdso_data *vd);
+int __c_kernel_clock_gettime64(clockid_t clock, struct __kernel_timespec *ts,
+			       const struct vdso_data *vd);
 int __c_kernel_clock_getres(clockid_t clock_id, struct old_timespec32 *res,
 			    const struct vdso_data *vd);
 #endif

arch/powerpc/kernel/vdso32/gettimeofday.S

@@ -35,6 +35,15 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
 	cvdso_call __c_kernel_clock_gettime
 V_FUNCTION_END(__kernel_clock_gettime)
 
+/*
+ * Exact prototype of clock_gettime64()
+ *
+ * int __kernel_clock_gettime64(clockid_t clock_id, struct __timespec64 *ts);
+ *
+ */
+V_FUNCTION_BEGIN(__kernel_clock_gettime64)
+	cvdso_call __c_kernel_clock_gettime64
+V_FUNCTION_END(__kernel_clock_gettime64)
 
 /*
  * Exact prototype of clock_getres()

arch/powerpc/kernel/vdso32/vdso32.lds.S

@@ -147,6 +147,7 @@ VERSION
 		__kernel_get_syscall_map;
 		__kernel_gettimeofday;
 		__kernel_clock_gettime;
+		__kernel_clock_gettime64;
 		__kernel_clock_getres;
 		__kernel_time;
 		__kernel_get_tbfreq;

arch/powerpc/kernel/vdso32/vgettimeofday.c

@@ -10,6 +10,12 @@ int __c_kernel_clock_gettime(clockid_t clock, struct old_timespec32 *ts,
 	return __cvdso_clock_gettime32_data(vd, clock, ts);
 }
 
+int __c_kernel_clock_gettime64(clockid_t clock, struct __kernel_timespec *ts,
+			       const struct vdso_data *vd)
+{
+	return __cvdso_clock_gettime_data(vd, clock, ts);
+}
+
 int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz,
 			    const struct vdso_data *vd)
 {