From patchwork Sun Jan 27 17:03:44 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [U-Boot] powerpc/lib: fix unsafe register handling in wait_ticks Date: Sun, 27 Jan 2013 07:03:44 -0000 From: =?utf-8?b?TWF0cyBLw6Rycm1hbiA8TWF0cy5LYXJybWFuQHRyaXRlY2guc2U+?= X-Patchwork-Id: 216022 Message-Id: To: "u-boot@lists.denx.de" 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 Cc: Wolfgang Denk Acked-by: Joakim Tjernlund Tested-by: Stefan Roese --- 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