[patch] Fix gdb crash on some missing ELF debug info
Jan Kratochvil
lace@jankratochvil.net
Fri Jun 23 13:08:00 GMT 2006
Hi Daniel,
On Fri, 23 Jun 2006 14:39:13 +0200, Daniel Jacobowitz wrote:
...
> The idea is definitely right - thanks! The patch could be a bit
> better:
>
> - We really ought to check that it fits within .debug_loc while we're
> here.
OK, fixed (I feel that the DWARF2 processing code is not so foolproof).
> - And I really can't figure out what what you mean by the comment. Do
> you mean "if we get here, and DW_UNSND (attr) != 0, and we hadn't added
> the next condition, then we'd end up with bogus ->size"?
sorry, it references the code below in dwarf2_symbol_mark_computed().
dwarf2_symbol_mark_computed():
if (".debug_loc" is missing) {
assume (dwarf2_per_objfile->loc_size == 0);
assume (dwarf2_per_objfile->loc_buffer == NULL);
}
assume(DW_UNSND (attr) != 0);
baton->size = dwarf2_per_objfile->loc_size - DW_UNSND (attr);
baton->data = dwarf2_per_objfile->loc_buffer + DW_UNSND (attr);
dwarf_expr_frame_base():
*start = symbaton->data;
MISSED, *(*start) crashes:
if (*start == NULL) error ("Could not find the frame base ...");
> You've been submitting a lot of fixes recently; while most of them are
> small, some are big enough to probably require a copyright assignment.
> Have you got one, or shall I send you the forms?
I already signed the copyright assignment to FSF intended for GNU Libtool
but the assignment form looks completely project unspecific to me.
I should be listed there as "Jan Kratochvil", it may be for the e-mail address
<project-libtool@jankratochvil.net>. Bradley M. Kuhn signed it on 7 Feb 2003.
> - Oh, and no ChangeLog
2006-06-23 Jan Kratochvil <lace@jankratochvil.net>
* dwarf2read.c (dwarf2_symbol_mark_computed): Fixed later crash
on location list reference if the ".debug_loc" section is missing.
Regards,
Jan Kratochvil
-------------- next part --------------
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=196439
Fedora Core 5:
gdb /usr/lib/valgrind/x86-linux/memcheck
break _start_in_C
run
segfault
eu-readelf -w /usr/lib/valgrind/x86-linux/memcheck
DWARF section '.debug_info' at offset 0x14759c:
...
[ 176d4] subprogram
...
name "_start_in_C"
...
frame_base location list [ 116d7]
corrupted as no location lists (.debug_loc) exist there at all.
Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.199
diff -u -p -r1.199 dwarf2read.c
--- dwarf2read.c 14 Jun 2006 15:06:35 -0000 1.199
+++ dwarf2read.c 23 Jun 2006 12:46:34 -0000
@@ -9324,7 +9324,9 @@ static void
dwarf2_symbol_mark_computed (struct attribute *attr, struct symbol *sym,
struct dwarf2_cu *cu)
{
- if (attr->form == DW_FORM_data4 || attr->form == DW_FORM_data8)
+ if ((attr->form == DW_FORM_data4 || attr->form == DW_FORM_data8)
+ /* ".debug_loc" may not exist at all. */
+ && DW_UNSND (attr) < dwarf2_per_objfile->loc_size)
{
struct dwarf2_loclist_baton *baton;
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