On 10/06/2016 07:18 AM, Mark Wielaard wrote:
> Having a symbol in an allocated symbol table (like .dynsym) that
> points to an unallocated section is wrong. Traditionally strip
> has removed such symbols if they are section or group symbols.
> But removing a real symbol from an allocate symbol table is hard
> and probably a mistake. Really removing it means rewriting the
> dynamic segment and hash sections. Since we don't do that, don't
> remove the symbol (and corrupt the ELF file). Do warn and set
> the symbol section to SHN_UNDEF.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=1380961
> 
> Signed-off-by: Mark Wielaard <mjw@redhat.com>

Works for me.  On the test from bugzilla, I get the expected warning:

  strip: Cannot remove symbol [1550] from allocated symbol table [3]

but ldd is perfectly happy with the result.

I also tried it with a manual "objcopy -R .rustc" beforehand, which I
will probably do in the rpm to prevent that section from even being
saved to debuginfo -- just discard it entirely.  Strip still works with
the same warning and a working result.

> ---
>  src/ChangeLog |  5 +++++
>  src/strip.c   | 35 ++++++++++++++++++++++++-----------
>  2 files changed, 29 insertions(+), 11 deletions(-)
> 
> diff --git a/src/ChangeLog b/src/ChangeLog
> index e5b3b20..70d11f2 100644
> --- a/src/ChangeLog
> +++ b/src/ChangeLog
> @@ -1,3 +1,8 @@
> +2016-10-06  Mark Wielaard  <mjw@redhat.com>
> +
> +	* strip.c (handle_elf): Don't remove real symbols from allocated
> +	symbol tables.
> +
>  2016-08-25  Mark Wielaard  <mjw@redhat.com>
>  
>  	* strip.c (handle_elf): Recompress with ELF_CHF_FORCE.
> diff --git a/src/strip.c b/src/strip.c
> index da093e9..819b67e 100644
> --- a/src/strip.c
> +++ b/src/strip.c
> @@ -1341,15 +1341,12 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
>  
>  		    /* Get the full section index, if necessary from the
>  		       XINDEX table.  */
> -		    if (sym->st_shndx != SHN_XINDEX)
> -		      sec = shdr_info[sym->st_shndx].idx;
> -		    else
> -		      {
> -			elf_assert (shndxdata != NULL
> -				    && shndxdata->d_buf != NULL);
> -
> -			sec = shdr_info[xshndx].idx;
> -		      }
> +		    if (sym->st_shndx == SHN_XINDEX)
> +		      elf_assert (shndxdata != NULL
> +				  && shndxdata->d_buf != NULL);
> +		    size_t sidx = (sym->st_shndx != SHN_XINDEX
> +				   ? sym->st_shndx : xshndx);
> +		    sec = shdr_info[sidx].idx;
>  
>  		    if (sec != 0)
>  		      {
> @@ -1387,6 +1384,24 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
>  			    shdr_info[cnt].shdr.sh_info = destidx - 1;
>  			  }
>  		      }
> +		    else if ((shdr_info[cnt].shdr.sh_flags & SHF_ALLOC) != 0
> +			     && GELF_ST_TYPE (sym->st_info) != STT_SECTION
> +			     && shdr_info[sidx].shdr.sh_type != SHT_GROUP)
> +		      {
> +			/* Removing a real symbol from an allocated
> +			   symbol table is hard and probably a
> +			   mistake.  Really removing it means
> +			   rewriting the dynamic segment and hash
> +			   sections.  Just warn and set the symbol
> +			   section to UNDEF.  */
> +			error (0, 0,
> +			       gettext ("Cannot remove symbol [%zd] from allocated symbol table [%zd]"), inner, cnt);
> +			sym->st_shndx = SHN_UNDEF;
> +			if (gelf_update_sym (shdr_info[cnt].data, destidx,
> +					     sym) == 0)
> +			  INTERNAL_ERROR (fname);
> +			shdr_info[cnt].newsymidx[inner] = destidx++;
> +		      }
>  		    else if (debug_fname != NULL
>  			     && shdr_info[cnt].debug_data == NULL)
>  		      /* The symbol points to a section that is discarded
> @@ -1394,8 +1409,6 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
>  			 this is a section or group signature symbol
>  			 for a section which has been removed.  */
>  		      {
> -			size_t sidx = (sym->st_shndx != SHN_XINDEX
> -					? sym->st_shndx : xshndx);
>  			elf_assert (GELF_ST_TYPE (sym->st_info) == STT_SECTION
>  				    || ((shdr_info[sidx].shdr.sh_type
>  					 == SHT_GROUP)
>