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Mail Archives: cygwin-developers/2001/01/24/16:07:03

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Date: Wed, 24 Jan 2001 15:33:44 -0500
Message-Id: <200101242033.PAA16287@envy.delorie.com>
X-Authentication-Warning: envy.delorie.com: dj set sender to dj AT envy DOT delorie DOT com using -f
From: DJ Delorie <dj AT delorie DOT com>
To: cygwin-developers AT cygwin DOT com
Subject: [hjl AT valinux DOT com: Re: A PE patch.]

Could people please look at this patch and try it?  The original code
assumed things it shouldn't, and thus you couldn't run, say, objdump
on MS system DLLs.  I like the idea about making bfd dynamic, but I
refuse to accept patches to this code without a "gut feeling" that it
will work *and* lots of testing, so the more people test it the
better.


------- Start of forwarded message -------
Date: Wed, 24 Jan 2001 11:15:05 -0800
From: "H . J . Lu" <hjl AT valinux DOT com>
To: DJ Delorie <dj AT redhat DOT com>
Subject: Re: A PE patch.
Content-Disposition: inline
User-Agent: Mutt/1.2.5i
In-Reply-To: <200101241909 DOT OAA06907 AT greed DOT delorie DOT com>; from dj AT redhat DOT com on Wed, Jan 24, 2001 at 02:09:12PM -0500
Content-Type: text/plain; charset=us-ascii

Here is the updated version. There is a bug in my old patch.

-- 
H.J. Lu (hjl AT valinux DOT com)
---
2001-01-23  H.J. Lu  <hjl AT gnu DOT org>

	* include/coff/pe.h (struct external_PEI_DOS_hdr): New.
	(struct external_PEI_IMAGE_hdr): New.
	
	* bfd/peicode.h (coff_swap_filehdr_in): Remove the e_magic
	checking.
	(pe_bfd_object_p): Rewrite with external_PEI_DOS_hdr and
	external_PEI_IMAGE_hdr.

Index: include/coff/pe.h
===================================================================
RCS file: /work/cvs/gnu/binutils/include/coff/pe.h,v
retrieving revision 1.1.1.7
diff -u -p -r1.1.1.7 pe.h
--- include/coff/pe.h	2000/09/05 17:49:11	1.1.1.7
+++ include/coff/pe.h	2001/01/24 18:46:34
@@ -125,6 +125,45 @@
 #undef  FILNMLEN
 #define FILNMLEN	18	/* # characters in a file name.  */
 
+struct external_PEI_DOS_hdr
+{
+  /* DOS header fields - always at offset zero in the EXE file.  */
+  char e_magic[2];		/* Magic number, 0x5a4d.  */
+  char e_cblp[2];		/* Bytes on last page of file, 0x90.  */
+  char e_cp[2];			/* Pages in file, 0x3.  */
+  char e_crlc[2];		/* Relocations, 0x0.  */
+  char e_cparhdr[2];		/* Size of header in paragraphs, 0x4.  */
+  char e_minalloc[2];		/* Minimum extra paragraphs needed, 0x0.  */
+  char e_maxalloc[2];		/* Maximum extra paragraphs needed, 0xFFFF.  */
+  char e_ss[2];			/* Initial (relative) SS value, 0x0.  */
+  char e_sp[2];			/* Initial SP value, 0xb8.  */
+  char e_csum[2];		/* Checksum, 0x0.  */
+  char e_ip[2];			/* Initial IP value, 0x0.  */
+  char e_cs[2];			/* Initial (relative) CS value, 0x0.  */
+  char e_lfarlc[2];		/* File address of relocation table, 0x40.  */
+  char e_ovno[2];		/* Overlay number, 0x0.  */
+  char e_res[4][2];		/* Reserved words, all 0x0.  */
+  char e_oemid[2];		/* OEM identifier (for e_oeminfo), 0x0.  */
+  char e_oeminfo[2];		/* OEM information; e_oemid specific, 0x0.  */
+  char e_res2[10][2];		/* Reserved words, all 0x0.  */
+  char e_lfanew[4];		/* File address of new exe header, usually 0x80.  */
+  char dos_message[16][4];	/* Other stuff, always follow DOS header.  */
+};
+
+struct external_PEI_IMAGE_hdr
+{
+  char nt_signature[4];		/* required NT signature, 0x4550.  */
+
+  /* From standard header.  */
+  char f_magic[2];		/* Magic number.		*/
+  char f_nscns[2];		/* Number of sections.		*/
+  char f_timdat[4];		/* Time & date stamp.		*/
+  char f_symptr[4];		/* File pointer to symtab.	*/
+  char f_nsyms[4];		/* Number of symtab entries.	*/
+  char f_opthdr[2];		/* Sizeof(optional hdr).	*/
+  char f_flags[2];		/* Flags.			*/
+};
+
 struct external_PEI_filehdr
 {
   /* DOS header fields - always at offset zero in the EXE file.  */
Index: bfd/peicode.h
===================================================================
RCS file: /work/cvs/gnu/binutils/bfd/peicode.h,v
retrieving revision 1.9
diff -u -p -r1.9 peicode.h
--- bfd/peicode.h	2001/01/23 20:11:14	1.9
+++ bfd/peicode.h	2001/01/24 18:36:09
@@ -208,26 +208,6 @@ coff_swap_filehdr_in (abfd, src, dst)
   filehdr_dst->f_flags = bfd_h_get_16(abfd, (bfd_byte *)filehdr_src-> f_flags);
   filehdr_dst->f_symptr = bfd_h_get_32 (abfd, (bfd_byte *) filehdr_src->f_symptr);
 
-#ifdef COFF_IMAGE_WITH_PE
-  /* There are really two magic numbers involved; the magic number
-     that says this is a NT executable (PEI) and the magic number that
-     determines the architecture.  The former is DOSMAGIC, stored in
-     the e_magic field.  The latter is stored in the f_magic field.
-     If the NT magic number isn't valid, the architecture magic number
-     could be mimicked by some other field (specifically, the number
-     of relocs in section 3).  Since this routine can only be called
-     correctly for a PEI file, check the e_magic number here, and, if
-     it doesn't match, clobber the f_magic number so that we don't get
-     a false match.  */
-#if 0
-  /* We can't assume that the PE header is at offset 0x80.  When it
-     isn't, the DOS header isn't read correctly, so we can't assume
-     e_magic is set even for valid PE files.  */
-  if (bfd_h_get_16 (abfd, (bfd_byte *) filehdr_src->e_magic) != DOSMAGIC)
-    filehdr_dst->f_magic = -1;
-#endif
-#endif
-
   /* Other people's tools sometimes generate headers with an nsyms but
      a zero symptr.  */
   if (filehdr_dst->f_nsyms != 0 && filehdr_dst->f_symptr == 0)
@@ -1255,16 +1235,10 @@ _("%s: Recognised but unhandled machine 
 static const bfd_target *
 pe_bfd_object_p (bfd * abfd)
 {
-  /* We need to handle a PE image correctly.  In PE images created by
-     the GNU linker, the offset to the COFF header is always the size.
-     However, this is not the case in images generated by other PE
-     linkers.  The PE format stores a four byte offset to the PE
-     signature just before the COFF header at location 0x3c of the file.
-     We pick up that offset, verify that the PE signature is there, and
-     then set ourselves up to read in the COFF header.  */
   bfd_byte buffer[4];
+  struct external_PEI_DOS_hdr dos_hdr;
+  struct external_PEI_IMAGE_hdr image_hdr;
   file_ptr offset;
-  unsigned long signature;
 
   /* Detect if this a Microsoft Import Library Format element.  */
   if (bfd_seek (abfd, 0x00, SEEK_SET) != 0
@@ -1275,44 +1249,56 @@ pe_bfd_object_p (bfd * abfd)
       return NULL;
     }
 
-  signature = bfd_h_get_32 (abfd, buffer);
-
-  if (signature == 0xffff0000)
+  if (bfd_h_get_32 (abfd, buffer) == 0xffff0000)
     return pe_ILF_object_p (abfd);
 
-  if (bfd_seek (abfd, 0x3c, SEEK_SET) != 0
-      || bfd_read (buffer, 1, 4, abfd) != 4)
+  if (bfd_seek (abfd, 0x00, SEEK_SET) != 0
+      || bfd_read (&dos_hdr, 1, sizeof (dos_hdr), abfd)
+	 != sizeof (dos_hdr))
     {
       if (bfd_get_error () != bfd_error_system_call)
 	bfd_set_error (bfd_error_wrong_format);
       return NULL;
     }
 
-  offset = bfd_h_get_32 (abfd, buffer);
+  /* There are really two magic numbers involved; the magic number
+     that says this is a NT executable (PEI) and the magic number that
+     determines the architecture.  The former is DOSMAGIC, stored in
+     the e_magic field.  The latter is stored in the f_magic field.
+     If the NT magic number isn't valid, the architecture magic number
+     could be mimicked by some other field (specifically, the number
+     of relocs in section 3).  Since this routine can only be called
+     correctly for a PEI file, check the e_magic number here, and, if
+     it doesn't match, clobber the f_magic number so that we don't get
+     a false match.  */
+  if (bfd_h_get_16 (abfd, (bfd_byte *) dos_hdr.e_magic) != DOSMAGIC)
+    {
+      bfd_set_error (bfd_error_wrong_format);
+      return NULL;
+    }
 
-  if (bfd_seek (abfd, offset, SEEK_SET) != 0
-      || bfd_read (buffer, 1, 4, abfd) != 4)
+  offset = bfd_h_get_32 (abfd, (bfd_byte *) dos_hdr.e_lfanew);
+  if (bfd_seek (abfd, (file_ptr) offset, SEEK_SET) != 0
+      || bfd_read (&image_hdr, 1, sizeof (image_hdr), abfd)
+	 != sizeof (image_hdr))
     {
       if (bfd_get_error () != bfd_error_system_call)
 	bfd_set_error (bfd_error_wrong_format);
       return NULL;
     }
-
-  signature = bfd_h_get_32 (abfd, buffer);
 
-  if (signature != 0x4550)
+  if (bfd_h_get_32 (abfd, (bfd_byte *) image_hdr.nt_signature)
+      != 0x4550)
     {
       bfd_set_error (bfd_error_wrong_format);
       return NULL;
     }
 
   /* Here is the hack.  coff_object_p wants to read filhsz bytes to
-     pick up the COFF header.  We adjust so that that will work.  20
-     is the size of the i386 COFF filehdr.  */
+     pick up the COFF header for PE, see "struct external_PEI_filehdr"
+     in include/coff/pe.h.  We adjust so that that will work. */
   if (bfd_seek (abfd,
-		(bfd_tell (abfd)
-		 - bfd_coff_filhsz (abfd)
-		 + 20),
+		(file_ptr) (offset - sizeof (dos_hdr)),
 		SEEK_SET)
       != 0)
     {
------- End of forwarded message -------

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