[Crash-utility] [PATCH] ARM: fp when unwinding

[Dave Anderson]

----- Original Message -----
> Hi Dave, Mika, Jan and anyone else interested in the Crash ARM
> support,
> 
> The table based unwind code potentially unwinds the stack pointer to the
> existing value of any other register except the PC:
> 
> 	} else if ((insn & 0xf0) == 0x90 &&
> 		   (insn & 0x0d) != 0x0d) {
> 		/* 1001 nnnn: set vsp = r[nnnn] */
> 		ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
> 
>   The 'struct stackframe' we use to keep unwind state when going from
> one frame to the next (or should I say previous) only contains fp, sp,
> lr and pc, which might be something we should consider changing. Even as
> it stands however, frame.fp is assigned an incorrect value for active
> tasks. Here's a patch to fix that.
> 
> 
> diff --git a/unwind_arm.c b/unwind_arm.c
> index fd6ac65..6554804 100644
> --- a/unwind_arm.c
> +++ b/unwind_arm.c
> @@ -710,6 +710,7 @@ unwind_backtrace(struct bt_info *bt)
>           */
>          if (bt->machdep) {
>                  const struct arm_pt_regs *regs = bt->machdep;
> +               frame.fp = regs->ARM_fp;
>                  frame.lr = regs->ARM_lr;
>          }
> 
> 
> And this time I did remember to run a 'make warn' =o)
> 
> Regards,
> Per

I can't comment on the backtrace functionality/query, but the patch
looks reasonable -- although it appears that with the current code,
as is, it would only affect CRASHDEBUG(5) output in unwind_frame()?

Dave