[PATCH 1/2] arm64: vdso: fix coarse clock handling

[Nathan Lynch]

When __kernel_clock_gettime is called with a CLOCK_MONOTONIC_COARSE or
CLOCK_REALTIME_COARSE clock id, it returns incorrectly to whatever the
caller has placed in x2.  Fix this by saving x30/LR to x2
unconditionally.

Also: the tv_nsec field in the result is shifted by the value in x12.
In the high-precision case x12 is cs_shift from the data page, but
for coarse clocks x12 is uninitialized.  Fix this by setting x12 to 0
once we know we are dealing with a coarse clock.

Signed-off-by: Nathan Lynch <nathan_lynch at mentor.com>
---
 arch/arm64/kernel/vdso/gettimeofday.S | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S
index f0a6d10b5211..6c37ae4a70c0 100644
--- a/arch/arm64/kernel/vdso/gettimeofday.S
+++ b/arch/arm64/kernel/vdso/gettimeofday.S
@@ -88,13 +88,13 @@ ENDPROC(__kernel_gettimeofday)
 /* int __kernel_clock_gettime(clockid_t clock_id, struct timespec *tp); */
 ENTRY(__kernel_clock_gettime)
 	.cfi_startproc
+	mov	x2, x30
+	.cfi_register x30, x2
+
 	cmp	w0, #CLOCK_REALTIME
 	ccmp	w0, #CLOCK_MONOTONIC, #0x4, ne
 	b.ne	2f
 
-	mov	x2, x30
-	.cfi_register x30, x2
-
 	/* Get kernel timespec. */
 	adr	vdso_data, _vdso_data
 1:	seqcnt_acquire
@@ -118,6 +118,9 @@ ENTRY(__kernel_clock_gettime)
 	ccmp	w0, #CLOCK_MONOTONIC_COARSE, #0x4, ne
 	b.ne	8f
 
+	/* Set shift to 0 for coarse clocks */
+	mov	x12, #0
+
 	/* Get coarse timespec. */
 	adr	vdso_data, _vdso_data
 3:	seqcnt_acquire
-- 
1.8.3.1