Re: [Patch] Fix PE dll -auto-import breakage from enforcing PE specs for section flags

[Danny Smith <danny_r_smith_2001 at yahoo dot co dot nz>]

 --- Nick Clifton <nickc@redhat.com> wrote: > Hi Danny,

> >
> > What about using WP_TEXT file flag (set by default) as a runtime flag?
> > ld --omagic already unsets this flag. Make --enable-auto-import do the
> > same when it is actually exercised.
> 
> Yeah that is a good idea.  I like the patch too.
> 
> > As I post, I realize that ld.texi probably needs to include warnings 
> > that the use of --enable-auto-import or --omagic will break strict PE specs.
> > I'll add those, once this is sorted.
> 
> OK, please do that as well.
> 
Hi,

Here is a slightly revised version of the patch. I can see no reason to
do all the bfd_set_file_flags() error checking (for each data symbol import)
when setting a known flag on a bfd of known format, so I just set the flag
directly with 'output_bfd->flags &= ~WP_TEXT'  

I've also have added notes to ld.texinfo.

Danny

bfd/ChangeLog

2003-01-16  Danny Smith  <dannysmith@users.sourceforge.net>

	* peXXigen.c (_bfd_XXi_swap_scnhdr_out): Don't remove
	IMAGE_SCN_MEM_WRITE flag from .text section if WP_TEXT
	has been unset.

1d/ChangeLog

2003-01-16  Danny Smith  <dannysmith@users.sourceforge.net>

	* pe-dll.c (pe_create_import_fixup): Unset WP_TEXT.
	* ld.texinfo (--omagic): Note that writable text section
	does not conform to published PE-COFF specs.
	(--enable-auto-import): Likewise.

Index: bfd/peXXigen.c
===================================================================
RCS file: /cvs/src/src/bfd/peXXigen.c,v
retrieving revision 1.20
diff -c -3 -p -r1.20 peXXigen.c
*** bfd/peXXigen.c	15 Dec 2003 11:50:11 -0000	1.20
--- bfd/peXXigen.c	16 Jan 2004 21:23:41 -0000
*************** _bfd_XXi_swap_scnhdr_out (abfd, in, out)
*** 985,997 ****
      pe_required_section_flags * p;
      int flags = scnhdr_int->s_flags;
  
      for (p = known_sections; p->section_name; p++)
        if (strcmp (scnhdr_int->s_name, p->section_name) == 0)
  	{
- 	  /* We have defaulted to adding the IMAGE_SCN_MEM_WRITE flag, but now
- 	     we know exactly what this specific section wants so we remove it
- 	     and then allow the must_have field to add it back in if necessary.  */
- 	  flags &= ~IMAGE_SCN_MEM_WRITE;
  	  flags |= p->must_have;
  	  break;
  	}
--- 985,1003 ----
      pe_required_section_flags * p;
      int flags = scnhdr_int->s_flags;
  
+     /* We have defaulted to adding the IMAGE_SCN_MEM_WRITE flag, but now
+        we know exactly what this specific section wants so we remove it
+        and then allow the must_have field to add it back in if necessary.
+        However, we don't remove IMAGE_SCN_MEM_WRITE flag from .text if the
+        default WP_TEXT file flag has been unset. */
+   
+     if (strcmp (scnhdr_int->s_name, ".text") 
+ 	|| (bfd_get_file_flags (abfd) & WP_TEXT))
+       flags &= ~IMAGE_SCN_MEM_WRITE;
+ 
      for (p = known_sections; p->section_name; p++)
        if (strcmp (scnhdr_int->s_name, p->section_name) == 0)
  	{
  	  flags |= p->must_have;
  	  break;
  	}
Index: ld/pe-dll.c
===================================================================
RCS file: /cvs/src/src/ld/pe-dll.c,v
retrieving revision 1.65
diff -c -3 -p -r1.65 pe-dll.c
*** ld/pe-dll.c	5 Dec 2003 11:30:18 -0000	1.65
--- ld/pe-dll.c	16 Jan 2004 21:23:45 -0000
*************** pe_create_import_fixup (arelent *rel, as
*** 2176,2181 ****
--- 2176,2182 ----
  
        /* If we ever use autoimport, we have to cast text section writable.  */
        config.text_read_only = FALSE;
+       output_bfd->flags &= ~WP_TEXT;   
      }
  
    if (addend == 0 || link_info.pei386_runtime_pseudo_reloc)
Index: ld/ld.texinfo
===================================================================
RCS file: /cvs/src/src/ld/ld.texinfo,v
retrieving revision 1.103
diff -c -3 -p -r1.103 ld.texinfo
*** ld/ld.texinfo	13 Jan 2004 11:10:53 -0000	1.103
--- ld/ld.texinfo	16 Jan 2004 21:24:02 -0000
*************** Turn off page alignment of sections, and
*** 687,693 ****
  Set the text and data sections to be readable and writable.  Also, do
  not page-align the data segment, and disable linking against shared
  libraries.  If the output format supports Unix style magic numbers,
! mark the output as @code{OMAGIC}.
  
  @kindex --no-omagic
  @cindex OMAGIC
--- 687,695 ----
  Set the text and data sections to be readable and writable.  Also, do
  not page-align the data segment, and disable linking against shared
  libraries.  If the output format supports Unix style magic numbers,
! mark the output as @code{OMAGIC}. Note: Although a writable text section
! is allowed for PE-COFF targets, it does not conform to the format
! specification published by Microsoft.
  
  @kindex --no-omagic
  @cindex OMAGIC
*************** uwin, pw, etc.  For instance, cygwin DLL
*** 1950,1957 ****
  @item --enable-auto-import
  Do sophisticated linking of @code{_symbol} to @code{__imp__symbol} for 
  DATA imports from DLLs, and create the necessary thunking symbols when 
! building the import libraries with those DATA exports.  This generally 
! will 'just work' -- but sometimes you may see this message:
  
  "variable '<var>' can't be auto-imported. Please read the 
  documentation for ld's @code{--enable-auto-import} for details."
--- 1952,1964 ----
  @item --enable-auto-import
  Do sophisticated linking of @code{_symbol} to @code{__imp__symbol} for 
  DATA imports from DLLs, and create the necessary thunking symbols when 
! building the import libraries with those DATA exports. Note: Use of the
! 'auto-import' extension will cause the text section of the image file
! to be made writable. This is does not conform to the PE-COFF format
! specification published by Microsoft.
! 
! Using 'auto-import' generally will 'just work' -- but sometimes you may
! see this message:
  
  "variable '<var>' can't be auto-imported. Please read the 
  documentation for ld's @code{--enable-auto-import} for details."

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