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[PATCH v2 7/9] gas: Warn if SFrame FDE is skipped due to non-default return column

Indu Bhagat indu.bhagat@oracle.com
Sat Feb 24 08:43:29 GMT 2024 
On 2/23/24 09:07, Jens Remus wrote:
> Print a warning message if SFrame FDE is skipped due to a non-default
> DWARF return column (i.e. return address (RA) register number). This
> may be caused by the use of CFI directive .cfi_return_column with a
> non-default return address (RA) register number in the processed
> assembler source code.
> 
>    Warning: skipping SFrame FDE due to non-default DWARF return column
> 
> gas/
> 	* gen-sframe.c: Warn if SFrame FDE is skipped due to non-default
> 	  DWARF return column.
> 
> gas/testsuite/
> 	* gas/cfi-sframe/common-empty-3.d: Update test case to expect
> 	  for new warning message when SFrame FDE is skipped due to
> 	  a non-default DWARF return column.
> 

One request in my comments below.

LGTM, Thanks!

PS: I will take a look at the next 2 patches (Patch 8/9 and Patch 9/9) 
in the series soon.

> Reviewed-by: Andreas Krebbel <krebbel@linux.ibm.com>
> Signed-off-by: Jens Remus <jremus@linux.ibm.com>
> ---
> 
> Notes (jremus):
>      Without this patch the assembler would erroneously generate bad SFrame
>      information for the s390-specific SFrame error test case 4, that gets
>      introduced by patch "s390: Initial support to generate .sframe from CFI
>      directives in assembler".
> 

This patch is only adding a warning.  The absence of it shouldn't have 
caused any bad SFrame info.

>   gas/gen-sframe.c                              | 8 ++++++--
>   gas/testsuite/gas/cfi-sframe/common-empty-3.d | 1 +
>   2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c
> index 1269b2b77c54..28b49a2a8425 100644
> --- a/gas/gen-sframe.c
> +++ b/gas/gen-sframe.c
> @@ -1345,7 +1345,10 @@ sframe_do_fde (struct sframe_xlate_ctx *xlate_ctx,
>   
>     /* If the return column is not RIP, SFrame format cannot represent it.  */

May I ask you to also include an update to this incorrect comment in 
your patch to something like:

/* SFrame format cannot represent a non-default DWARF return column reg.  */
>     if (xlate_ctx->dw_fde->return_column != DWARF2_DEFAULT_RETURN_COLUMN)
> -    return SFRAME_XLATE_ERR_NOTREPRESENTED;
> +    {
> +      as_warn (_("skipping SFrame FDE due to non-default DWARF return column"));
> +      return SFRAME_XLATE_ERR_NOTREPRESENTED;
> +    }
>   
>     /* Iterate over the CFIs and create SFrame FREs.  */
>     for (cfi_insn = dw_fde->data; cfi_insn; cfi_insn = cfi_insn->next)
> @@ -1355,7 +1358,8 @@ sframe_do_fde (struct sframe_xlate_ctx *xlate_ctx,
>         if (err != SFRAME_XLATE_OK)
>   	{
>   	  /* Skip generating SFrame stack trace info for the function if any
> -	     offending CFI is encountered by sframe_do_cfi_insn ().  */
> +	     offending CFI is encountered by sframe_do_cfi_insn ().  Warning
> +	     message already printed by sframe_do_cfi_insn ().  */
>   	  return err; /* Return the error code.  */
>   	}
>       }
> diff --git a/gas/testsuite/gas/cfi-sframe/common-empty-3.d b/gas/testsuite/gas/cfi-sframe/common-empty-3.d
> index 5914c620760d..d17521dd88ea 100644
> --- a/gas/testsuite/gas/cfi-sframe/common-empty-3.d
> +++ b/gas/testsuite/gas/cfi-sframe/common-empty-3.d
> @@ -1,4 +1,5 @@
>   #as: --gsframe
> +#warning: skipping SFrame FDE due to non-default DWARF return column
>   #objdump: --sframe=.sframe
>   #name: SFrame supports only default return column
>   #...
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