Re: Bug fix for gldelf_i386_place_orphan in elf32.em [version 2.20.1]

[Alan Modra <amodra at gmail dot com>]

On Wed, Jan 12, 2011 at 03:48:50PM +0800, Sheng, Yongjie wrote:
> Please see my small linker-test.tgz test package.
> With "-gstabs" compiling option, a hello world (binutils-2.20.1) links with a mangled-section.o(two section names are mangled, being orphan sections).
> It will crash in running (in ld-linux.so.2).
> It will not crash if built with binutils-2.17.50 (FC8).

Thanks.  That nicely illuminates the bug, which is that using
lookup->prev can result in hold[orphan_nonalloc].os equal to
hold[orphan_bss].os.  If that happens, then orphan bss sections and
orphan non-alloc sections might be intermingled.

I'll test the following patch overnight, to find the inevitable
testsuite failures this will cause..

Index: ld/emultempl/elf32.em
===================================================================
RCS file: /cvs/src/src/ld/emultempl/elf32.em,v
retrieving revision 1.216
diff -u -p -r1.216 elf32.em
--- ld/emultempl/elf32.em	20 Dec 2010 13:00:14 -0000	1.216
+++ ld/emultempl/elf32.em	12 Jan 2011 13:30:55 -0000
@@ -1788,7 +1788,7 @@ gld${EMULATION_NAME}_place_orphan (asect
       { ".sdata",
 	SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD | SEC_DATA | SEC_SMALL_DATA,
 	0, 0, 0, 0 },
-      { 0,
+      { ".comment",
 	SEC_HAS_CONTENTS,
 	0, 0, 0, 0 },
     };
@@ -1880,7 +1880,6 @@ gld${EMULATION_NAME}_place_orphan (asect
 
   if (!orphan_init_done)
     {
-      lang_output_section_statement_type *lookup;
       struct orphan_save *ho;
 
       for (ho = hold; ho < hold + sizeof (hold) / sizeof (hold[0]); ++ho)
@@ -1890,16 +1889,6 @@ gld${EMULATION_NAME}_place_orphan (asect
 	    if (ho->os != NULL && ho->os->flags == 0)
 	      ho->os->flags = ho->flags;
 	  }
-      lookup = hold[orphan_bss].os;
-      if (lookup == NULL)
-	lookup = &lang_output_section_statement.head->output_section_statement;
-      for (; lookup != NULL; lookup = lookup->next)
-	if ((lookup->bfd_section != NULL
-	     && (lookup->bfd_section->flags & SEC_DEBUGGING) != 0)
-	    || strcmp (lookup->name, ".comment") == 0)
-	  break;
-      hold[orphan_nonalloc].os = lookup ? lookup->prev : NULL;
-      hold[orphan_nonalloc].name = ".comment";
       orphan_init_done = 1;
     }
 
-- 
Alan Modra
Australia Development Lab, IBM