[PATCH] Don't handle blocks as exprlocs for DWARF version 4 or higher.

Mark Wielaard mark@klomp.org
Thu Feb 18 13:40:36 GMT 2021


On Sat, 2021-02-13 at 23:46 +0100, Mark Wielaard wrote:
> Since DWARF version 4 blocks just contain bytes, trying to interpret
> them as exprlocs will most likely fail.
> 
>      * dwz.c (add_locexpr_dummy_dies): Only handle block as exprloc
>      for cu_version < 4.
>      (checksum_die): Likewise.
>      (write_die): Likewise.
> 
> https://sourceware.org/bugzilla/show_bug.cgi?id=26987

Ping. Any comments?

>  dwz.c | 166 +++++++++++++++++++++++++++++---------------------------
> --
>  1 file changed, 84 insertions(+), 82 deletions(-)
> 
> diff --git a/dwz.c b/dwz.c
> index d6b9df0..02fcd8c 100644
> --- a/dwz.c
> +++ b/dwz.c
> @@ -2913,43 +2913,44 @@ add_locexpr_dummy_dies (DSO *dso, dw_cu_ref
> cu, dw_die_ref die,
>    if (form == DW_FORM_block1)
>      {
>        /* Old DWARF uses blocks instead of exprlocs.  */
> -      switch (attr)
> -	{
> -	case DW_AT_frame_base:
> -	case DW_AT_location:
> -	case DW_AT_data_member_location:
> -	case DW_AT_vtable_elem_location:
> -	case DW_AT_byte_size:
> -	case DW_AT_bit_offset:
> -	case DW_AT_bit_size:
> -	case DW_AT_string_length:
> -	case DW_AT_lower_bound:
> -	case DW_AT_return_addr:
> -	case DW_AT_bit_stride:
> -	case DW_AT_upper_bound:
> -	case DW_AT_count:
> -	case DW_AT_segment:
> -	case DW_AT_static_link:
> -	case DW_AT_use_location:
> -	case DW_AT_allocated:
> -	case DW_AT_associated:
> -	case DW_AT_data_location:
> -	case DW_AT_byte_stride:
> -	case DW_AT_rank:
> -	case DW_AT_call_value:
> -	case DW_AT_call_target:
> -	case DW_AT_call_target_clobbered:
> -	case DW_AT_call_data_location:
> -	case DW_AT_call_data_value:
> -	case DW_AT_GNU_call_site_value:
> -	case DW_AT_GNU_call_site_data_value:
> -	case DW_AT_GNU_call_site_target:
> -	case DW_AT_GNU_call_site_target_clobbered:
> -	  if (read_exprloc_low_mem_phase1 (dso, die, ptr, len))
> -	    return 1;
> -	default:
> -	  break;
> -	}
> +      if (cu->cu_version < 4)
> +	switch (attr)
> +	  {
> +	  case DW_AT_frame_base:
> +	  case DW_AT_location:
> +	  case DW_AT_data_member_location:
> +	  case DW_AT_vtable_elem_location:
> +	  case DW_AT_byte_size:
> +	  case DW_AT_bit_offset:
> +	  case DW_AT_bit_size:
> +	  case DW_AT_string_length:
> +	  case DW_AT_lower_bound:
> +	  case DW_AT_return_addr:
> +	  case DW_AT_bit_stride:
> +	  case DW_AT_upper_bound:
> +	  case DW_AT_count:
> +	  case DW_AT_segment:
> +	  case DW_AT_static_link:
> +	  case DW_AT_use_location:
> +	  case DW_AT_allocated:
> +	  case DW_AT_associated:
> +	  case DW_AT_data_location:
> +	  case DW_AT_byte_stride:
> +	  case DW_AT_rank:
> +	  case DW_AT_call_value:
> +	  case DW_AT_call_target:
> +	  case DW_AT_call_target_clobbered:
> +	  case DW_AT_call_data_location:
> +	  case DW_AT_call_data_value:
> +	  case DW_AT_GNU_call_site_value:
> +	  case DW_AT_GNU_call_site_data_value:
> +	  case DW_AT_GNU_call_site_target:
> +	  case DW_AT_GNU_call_site_target_clobbered:
> +	    if (read_exprloc_low_mem_phase1 (dso, die, ptr, len))
> +	      return 1;
> +	  default:
> +	    break;
> +	  }
>  
>        return 0;
>      }
> @@ -3736,50 +3737,51 @@ checksum_die (DSO *dso, dw_cu_ref cu,
> dw_die_ref top_die, dw_die_ref die)
>        if (form == DW_FORM_block1)
>  	{
>  	  /* Old DWARF uses blocks instead of exprlocs.  */
> -	  switch (t->attr[i].attr)
> -	    {
> -	    case DW_AT_frame_base:
> -	    case DW_AT_location:
> -	    case DW_AT_data_member_location:
> -	    case DW_AT_vtable_elem_location:
> -	    case DW_AT_byte_size:
> -	    case DW_AT_bit_offset:
> -	    case DW_AT_bit_size:
> -	    case DW_AT_string_length:
> -	    case DW_AT_lower_bound:
> -	    case DW_AT_return_addr:
> -	    case DW_AT_bit_stride:
> -	    case DW_AT_upper_bound:
> -	    case DW_AT_count:
> -	    case DW_AT_segment:
> -	    case DW_AT_static_link:
> -	    case DW_AT_use_location:
> -	    case DW_AT_allocated:
> -	    case DW_AT_associated:
> -	    case DW_AT_data_location:
> -	    case DW_AT_byte_stride:
> -	    case DW_AT_rank:
> -	    case DW_AT_call_value:
> -	    case DW_AT_call_target:
> -	    case DW_AT_call_target_clobbered:
> -	    case DW_AT_call_data_location:
> -	    case DW_AT_call_data_value:
> -	    case DW_AT_GNU_call_site_value:
> -	    case DW_AT_GNU_call_site_data_value:
> -	    case DW_AT_GNU_call_site_target:
> -	    case DW_AT_GNU_call_site_target_clobbered:
> -	      if (die->die_ck_state != CK_BAD)
> -		{
> -		  s = t->attr[i].attr;
> -		  die->u.p1.die_hash
> -		    = iterative_hash_object (s, die->u.p1.die_hash);
> -		}
> -	      if (read_exprloc (dso, die, ptr, len, NULL))
> -		return 1;
> -	      handled = true;
> -	    default:
> -	      break;
> -	    }
> +	  if (cu->cu_version < 4)
> +	    switch (t->attr[i].attr)
> +	      {
> +	      case DW_AT_frame_base:
> +	      case DW_AT_location:
> +	      case DW_AT_data_member_location:
> +	      case DW_AT_vtable_elem_location:
> +	      case DW_AT_byte_size:
> +	      case DW_AT_bit_offset:
> +	      case DW_AT_bit_size:
> +	      case DW_AT_string_length:
> +	      case DW_AT_lower_bound:
> +	      case DW_AT_return_addr:
> +	      case DW_AT_bit_stride:
> +	      case DW_AT_upper_bound:
> +	      case DW_AT_count:
> +	      case DW_AT_segment:
> +	      case DW_AT_static_link:
> +	      case DW_AT_use_location:
> +	      case DW_AT_allocated:
> +	      case DW_AT_associated:
> +	      case DW_AT_data_location:
> +	      case DW_AT_byte_stride:
> +	      case DW_AT_rank:
> +	      case DW_AT_call_value:
> +	      case DW_AT_call_target:
> +	      case DW_AT_call_target_clobbered:
> +	      case DW_AT_call_data_location:
> +	      case DW_AT_call_data_value:
> +	      case DW_AT_GNU_call_site_value:
> +	      case DW_AT_GNU_call_site_data_value:
> +	      case DW_AT_GNU_call_site_target:
> +	      case DW_AT_GNU_call_site_target_clobbered:
> +		if (die->die_ck_state != CK_BAD)
> +		  {
> +		    s = t->attr[i].attr;
> +		    die->u.p1.die_hash
> +		      = iterative_hash_object (s, die->u.p1.die_hash);
> +		  }
> +		if (read_exprloc (dso, die, ptr, len, NULL))
> +		  return 1;
> +		handled = true;
> +	      default:
> +		break;
> +	      }
>  	  ptr += len;
>  	}
>        else if (form == DW_FORM_exprloc)
> @@ -12392,7 +12394,7 @@ write_die (unsigned char *ptr, dw_cu_ref cu,
> dw_die_ref die,
>  	  ptr += inptr - orig_ptr;
>  
>  	  /* Old DWARF uses blocks instead of exprlocs.  */
> -	  if (form == DW_FORM_block1)
> +	  if (form == DW_FORM_block1 && cu->cu_version < 4)
>  	    switch (reft->attr[i].attr)
>  	      {
>  	      case DW_AT_frame_base:


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