[patch] .gdb_index: Do not crash on NOBITS

[Jan Kratochvil <jan.kratochvil@redhat.com>]

Hi,

elfutils-0.148 still do not contain patch of its GIT
804e9ca4d644e64a6125307cbf0a0b89477d7611 where the .gdb_index section has been
also split into the separate debug info file.

Due to it binaries split using elfutils-0.148 contain
  [38] .gdb_index        NOBITS           0000000000000000  0000338c
instead of expected
  [28] .gdb_index        PROGBITS         0000000000000000  0000211c

and due to it GDB while reading the file can error() by:
Reading symbols from x.debug...Dwarf Error: Can't read DWARF data from 'x.debug'

which should not be fatal but due to some other bugs therein it can crash GDB.

The wrong separate debug info file is for example:
http://kojipkgs.fedoraproject.org/packages/glibc/2.12.90/10/x86_64/glibc-debuginfo-2.12.90-10.x86_64.rpm
/usr/lib/debug/lib64/libutil-2.12.90.so.debug

OK to check-in?

It does not attempt to use .gdb_index from the main binary, it will just
disable .gdb_index usage on these binaries.


Thanks,
Jan


gdb/
2010-09-08  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* dwarf2read.c (dwarf2_read_index): Return on no SEC_HAS_CONTENTS.

--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -1904,6 +1904,13 @@ dwarf2_read_index (struct objfile *objfile)
   if (dwarf2_per_objfile->gdb_index.asection == NULL
       || dwarf2_per_objfile->gdb_index.size == 0)
     return 0;
+
+  /* Older elfutils strip versions could keep the section in the main
+     executable while splitting it for the separate debug info file.  */
+  if ((bfd_get_file_flags (dwarf2_per_objfile->gdb_index.asection)
+       & SEC_HAS_CONTENTS) == 0)
+    return 0;
+
   dwarf2_read_section (objfile, &dwarf2_per_objfile->gdb_index);
 
   addr = dwarf2_per_objfile->gdb_index.buffer;