[U-Boot] [PATCH] powerpc/lib: fix unsafe register handling in wait_ticks
Mats Kärrman
Mats.Karrman at tritech.se
Sun Jan 27 18:03:44 CET 2013
If watchdog is enabled, the arch/powerpc/lib/ticks.S::wait_ticks() function
calls the function specified by the WATCHDOG_RESET macro.
The wait_ticks function depends on the registers r0, r6 and r7 being
preserved however that is not guaranteed, e.g. if the reset function is a
C function this will probably overwrite r0 and cause an endless loop.
The following patch changes to using r14+r15 instead of r6+r7 (to resemble
what would have been generated by a C compiler) and saves all necessary
registers on the stack.
The patch has been tested on a custom MPC5125 based machine using the 512x
powerpc architecture.
Signed-off-by: Mats Karrman <mats.karrman at tritech.se>
Cc: Wolfgang Denk <wd at denx.de>
Acked-by: Joakim Tjernlund <joakim.tjernlund at transmode.se>
---
arch/powerpc/lib/ticks.S | 17 +++++++++++------
1 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/lib/ticks.S b/arch/powerpc/lib/ticks.S
index 1781039..63114bb 100644
--- a/arch/powerpc/lib/ticks.S
+++ b/arch/powerpc/lib/ticks.S
@@ -50,19 +50,24 @@ wait_ticks:
stwu r1, -16(r1)
mflr r0 /* save link register */
stw r0, 20(r1) /* Use r0 or GDB will be unhappy */
- mr r7, r3 /* save tick count */
+ stw r14, 12(r1) /* save used registers */
+ stw r15, 8(r1)
+ mr r14, r3 /* save tick count */
bl get_ticks /* Get start time */
/* Calculate end time */
- addc r7, r4, r7 /* Compute end time lower */
- addze r6, r3 /* and end time upper */
+ addc r14, r4, r14 /* Compute end time lower */
+ addze r15, r3 /* and end time upper */
WATCHDOG_RESET /* Trigger watchdog, if needed */
1: bl get_ticks /* Get current time */
- subfc r4, r4, r7 /* Subtract current time from end time */
- subfe. r3, r3, r6
+ subfc r4, r4, r14 /* Subtract current time from end time */
+ subfe. r3, r3, r15
bge 1b /* Loop until time expired */
- mtlr r0 /* restore link register */
+ lwz r15, 8(r1) /* restore saved registers */
+ lwz r14, 12(r1)
+ lwz r0, 20(r1)
addi r1,r1,16
+ mtlr r0
blr
--
1.7.1
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