[PATCH 3.16.y-ckt 065/128] ARM: 8471/1: need to save/restore arm register(r11) when it is corrupted

From: Luis Henriques
Date: Sun Jan 24 2016 - 17:24:46 EST

3.16.7-ckt23 -stable review patch. If anyone has any objections, please let me know.


From: Anson Huang <Anson.Huang@xxxxxxxxxxxxx>

commit fa0708b320f6da4c1104fe56e01b7abf66fd16ad upstream.

In cpu_v7_do_suspend routine, r11 is used while it is NOT
saved/restored, different compiler may have different usage
of ARM general registers, so it may cause issues during
calling cpu_v7_do_suspend.

We meet kernel fault occurs when using GCC 4.8.3, r11 contains
valid value before calling into cpu_v7_do_suspend, but when returned
from this routine, r11 is corrupted and lead to kernel fault.
Doing save/restore for those corrupted registers is a must in
assemble code.

Signed-off-by: Anson Huang <Anson.Huang@xxxxxxxxxxxxx>
Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
arch/arm/mm/proc-v7.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 0eba0d1fd65a..ce9444e9d001 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -95,7 +95,7 @@ ENDPROC(cpu_v7_dcache_clean_area)
.equ cpu_v7_suspend_size, 4 * 9
- stmfd sp!, {r4 - r10, lr}
+ stmfd sp!, {r4 - r11, lr}
mrc p15, 0, r4, c13, c0, 0 @ FCSE/PID
mrc p15, 0, r5, c13, c0, 3 @ User r/o thread ID
stmia r0!, {r4 - r5}
@@ -112,7 +112,7 @@ ENTRY(cpu_v7_do_suspend)
mrc p15, 0, r9, c1, c0, 1 @ Auxiliary control register
mrc p15, 0, r10, c1, c0, 2 @ Co-processor access control
stmia r0, {r5 - r11}
- ldmfd sp!, {r4 - r10, pc}
+ ldmfd sp!, {r4 - r11, pc}