Re: [PATCH] ld (bfd) arm32 elf invalid strings offset in .strtab

[Alan Modra <amodra at gmail dot com>]

On Tue, Aug 20, 2019 at 05:46:52PM +0200, tlaronde@polynum.com wrote:
> diff --git a/bfd/elf.c b/bfd/elf.c
> index 42ae162..dd7efd8 100644
> --- a/bfd/elf.c
> +++ b/bfd/elf.c
> @@ -498,6 +498,19 @@ bfd_elf_get_elf_syms (bfd *ibfd,
>  
>    /* Convert the symbols to internal form.  */
>    isymend = intsym_buf + symcount;
> +	{
> +		/* arm32 deals with names during the call of (*swap_symbol_in).
> +		 * It thus needs to associate the correct strings to the
> +		 * symbols. So we temporarily redefine the private data with
> +		 * the correct symtab_hdr so that using elf_symtab_hdr (ibfd)
> +		 * will give the correct information and we restore after in
> +		 * order to keep it as it for the various callers.
> +		 */
> +		Elf_Internal_Shdr bak;	
> +
> +		bak = elf_symtab_hdr (ibfd);
> +		elf_symtab_hdr (ibfd) = *symtab_hdr;
> +
>    for (esym = (const bfd_byte *) extsym_buf, isym = intsym_buf,
>  	   shndx = extshndx_buf;
>         isym < isymend;
> @@ -512,8 +525,11 @@ bfd_elf_get_elf_syms (bfd *ibfd,
>  	if (alloc_intsym != NULL)
>  	  free (alloc_intsym);
>  	intsym_buf = NULL;
> +			elf_symtab_hdr (ibfd) = bak;
>  	goto out;
>        }
> +		elf_symtab_hdr (ibfd) = bak;
> +	}
>  
>   out:
>    if (alloc_ext != NULL)

This is just piling on horrible hacks.  elf32_arm_swap_symbol_in
should not be calling bfd_elf_sym_name.  I would recommend just
deleting ARM_{GET,SET}_SYM_CMSE_SPCL and instead replacing uses of
ARM_GET_SYM_CMSE_SPCL with a string compare of the name with
CMSE_PREFIX.  I don't believe there is any need to use
st_target_internal & 4 to cache the result of a name comparison,
and swap_symbol_in is not the best place to do so in terms of speed.

BTW, if you and the ARM maintainers do want to continue with
horrible hacks, the following in elf32_arm_swap_symbol_in probably
will work.

diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
index f1895df278..430c8feaa5 100644
--- a/bfd/elf32-arm.c
+++ b/bfd/elf32-arm.c
@@ -19960,7 +19960,10 @@ elf32_arm_swap_symbol_in (bfd * abfd,
     ARM_SET_SYM_BRANCH_TYPE (dst->st_target_internal, ST_BRANCH_UNKNOWN);
 
   /* Mark CMSE special symbols.  */
-  symtab_hdr = & elf_symtab_hdr (abfd);
+  if ((abfd->flags & DYNAMIC) == 0 || elf_dynsymtab (abfd) == 0)
+    symtab_hdr = &elf_tdata (abfd)->symtab_hdr;
+  else
+    symtab_hdr = &elf_tdata (abfd)->dynsymtab_hdr;
   if (symtab_hdr->sh_size)
     name = bfd_elf_sym_name (abfd, symtab_hdr, dst, NULL);
   if (name && CONST_STRNEQ (name, CMSE_PREFIX))

-- 
Alan Modra
Australia Development Lab, IBM