[Crash-utility] [PATCH] ARM: fix unwinding on recent kernels

[Mika Westerberg]

On Sat, Feb 11, 2012 at 08:00:34PM +0530, Rabin Vincent wrote:
> Unwinding doesn't work on recent ARM kernels since after the following
> commit the kernel doesn't perform the prel31_to_addr() conversion of the
> offsets in the index table.  The leads to crash not finding the correct
> unwind instructions.
> 
> http://git.kernel.org/linus/de66a979012dbc66b1ec0125795a3f79ee667b8a
> 
> The patch below makes crash do the conversion itself if necessary.
> 
> Rabin
> 
> diff --git a/unwind_arm.c b/unwind_arm.c
> index d86ec63..e804cfb 100644
> --- a/unwind_arm.c
> +++ b/unwind_arm.c
> @@ -71,6 +71,8 @@ struct unwind_table {
>  static struct unwind_table	*kernel_unwind_table;
>  static struct unwind_table	*module_unwind_tables;
>  
> +static int index_in_prel31;
> +
>  struct unwind_ctrl_block {
>  	ulong	vrs[16];
>  	ulong	insn;
> @@ -104,6 +106,7 @@ static int is_core_kernel_text(ulong);
>  static struct unwind_table *search_table(ulong);
>  static struct unwind_idx *search_index(const struct unwind_table *, ulong);
>  static ulong prel31_to_addr(ulong, ulong);
> +static void index_prel31_to_addr(struct unwind_table *);
>  static int unwind_frame(struct stackframe *, ulong);
>  
>  /*
> @@ -187,6 +190,8 @@ init_kernel_unwind_table(void)
>  		goto fail;
>  	}
>  
> +	index_in_prel31 = !is_kernel_text(kernel_unwind_table->idx[0].addr);

Maybe add some comment explaining why we do this check (a reference to the
kernel commit perhaps)?

Otherwise looks good and my older ARM crashdumps still seem to work with this
change.