On 07/20/2012 04:20 AM, Joakim Tjernlund wrote:
PowerPC mandates SP to be 16 bytes aligned. Furthermore, a stack frame is added, pointing to the reset vector which is just get in the way when gdb is walking the stack because the reset vector may not accessible depending on emulator settings. Also use a temp register so gdb doesn't pick up intermediate values.
Signed-off-by: Joakim Tjernlund Joakim.Tjernlund@transmode.se
arch/powerpc/cpu/mpc85xx/start.S | 16 +++++----------- 1 files changed, 5 insertions(+), 11 deletions(-)
diff --git arch/powerpc/cpu/mpc85xx/start.S arch/powerpc/cpu/mpc85xx/start.S index 8d66cf1..8c75af9 100644 --- arch/powerpc/cpu/mpc85xx/start.S +++ arch/powerpc/cpu/mpc85xx/start.S @@ -848,18 +848,12 @@ version_string: .globl _start_cont _start_cont: /* Setup the stack in initial RAM,could be L2-as-SRAM or L1 dcache*/
- lis r1,CONFIG_SYS_INIT_RAM_ADDR@h
- ori r1,r1,CONFIG_SYS_INIT_SP_OFFSET@l
- lis r2,(CONFIG_SYS_INIT_RAM_ADDR)@h
- ori r2,r2,((CONFIG_SYS_INIT_SP_OFFSET-16)&~0xf)@l /* Align to 16 */
Please don't use r2 as a general purpose register -- even if it's early enough that we haven't started using it for its fixed purpose yet.
- stw r0,-4(r2) /* Store a NULL LR */
- stw r0,0(r2) /* Store a NULL Back Chain */
- mr r1,r2 /* Transfer to SP(r1) */
Why are you storing anything below the stack pointer? LR goes above the backchain, not below -- and it's not valid anyway for the current stack frame. If you want to have a terminating stack frame with a NULL LR, you need to create a second stack frame, like the code currently does.
-Scott