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Re: gdb: Incorrect stack unwinding if compressed debug info is used
- From: Tom Tromey <tromey at redhat dot com>
- To: Vladimir Simonov <sv at sw dot ru>
- Cc: gdb-patches at sourceware dot org
- Date: Fri, 04 Feb 2011 10:56:19 -0700
- Subject: Re: gdb: Incorrect stack unwinding if compressed debug info is used
- References: <1296238472.3009.ezmlm@sourceware.org> <4D46D872.6080407@sw.ru> <m3y65vahdf.fsf@fleche.redhat.com> <4D4C383A.3000203@sw.ru>
>>>>> "Vladimir" == Vladimir Simonov <sv@sw.ru> writes:
Vladimir> I'd also suggest to remove dwarf2_read_section from
Vladimir> fill_in_loclist_baton. Without it all works ok also.
There is another caller of fill_in_loclist_baton, and it wasn't obvious
to me that this change would be safe.
Vladimir> But resulted code looks a bit hackish:
I agree. Also, I audited all other uses of the 'size' field.
I found one more where it was not obvious whether the use was safe.
And, I found another area that could use a little cleanup.
So, I came up with the appended. Let me know what you think. If you
could try it, that would be helpful.
I am running it through the test suite. I plan to commit it if it all
passes.
Tom
2011-02-04 Tom Tromey <tromey@redhat.com>
* dwarf2read.c (dwarf2_section_empty_p): New function.
(dwarf2_read_section): Use dwarf2_section_empty_p.
(dwarf2_section_size): New function.
(dwarf2_get_section_info): Unconditionally read section.
(dwarf2_read_index): Use dwarf2_section_empty_p.
(partial_read_comp_unit_head): Use dwarf2_section_size.
(dwarf2_symbol_mark_computed): Likewise.
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 6a98d57..d7dd3d5 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -1509,6 +1509,14 @@ zlib_decompress_section (struct objfile *objfile, asection *sectp,
#endif
}
+/* A helper function that decides whether a section is empty. */
+
+static int
+dwarf2_section_empty_p (struct dwarf2_section_info *info)
+{
+ return info->asection == NULL || info->size == 0;
+}
+
/* Read the contents of the section SECTP from object file specified by
OBJFILE, store info about the section into INFO.
If the section is compressed, uncompress it before returning. */
@@ -1527,7 +1535,7 @@ dwarf2_read_section (struct objfile *objfile, struct dwarf2_section_info *info)
info->was_mmapped = 0;
info->readin = 1;
- if (info->asection == NULL || info->size == 0)
+ if (dwarf2_section_empty_p (info))
return;
/* Check if the file has a 4-byte header indicating compression. */
@@ -1592,6 +1600,18 @@ dwarf2_read_section (struct objfile *objfile, struct dwarf2_section_info *info)
bfd_get_filename (abfd));
}
+/* A helper function that returns the size of a section in a safe
+ way. */
+
+static bfd_size_type
+dwarf2_section_size (struct objfile *objfile,
+ struct dwarf2_section_info *info)
+{
+ if (!info->readin)
+ dwarf2_read_section (objfile, info);
+ return info->size;
+}
+
/* Fill in SECTP, BUFP and SIZEP with section info, given OBJFILE and
SECTION_NAME. */
@@ -1620,9 +1640,7 @@ dwarf2_get_section_info (struct objfile *objfile, const char *section_name,
else
gdb_assert_not_reached ("unexpected section");
- if (info->asection != NULL && info->size != 0 && info->buffer == NULL)
- /* We haven't read this section in yet. Do it now. */
- dwarf2_read_section (objfile, info);
+ dwarf2_read_section (objfile, info);
*sectp = info->asection;
*bufp = info->buffer;
@@ -2008,8 +2026,7 @@ dwarf2_read_index (struct objfile *objfile)
offset_type types_list_elements = 0;
int i;
- if (dwarf2_per_objfile->gdb_index.asection == NULL
- || dwarf2_per_objfile->gdb_index.size == 0)
+ if (dwarf2_section_empty_p (&dwarf2_per_objfile->gdb_index))
return 0;
/* Older elfutils strip versions could keep the section in the main
@@ -2823,7 +2840,9 @@ partial_read_comp_unit_head (struct comp_unit_head *header, gdb_byte *info_ptr,
"(is %d, should be 2, 3, or 4) [in module %s]"), header->version,
bfd_get_filename (abfd));
- if (header->abbrev_offset >= dwarf2_per_objfile->abbrev.size)
+ if (header->abbrev_offset
+ >= dwarf2_section_size (dwarf2_per_objfile->objfile,
+ &dwarf2_per_objfile->abbrev))
error (_("Dwarf Error: bad offset (0x%lx) in compilation unit header "
"(offset 0x%lx + 6) [in module %s]"),
(long) header->abbrev_offset,
@@ -14365,7 +14384,8 @@ dwarf2_symbol_mark_computed (struct attribute *attr, struct symbol *sym,
/* ".debug_loc" may not exist at all, or the offset may be outside
the section. If so, fall through to the complaint in the
other branch. */
- && DW_UNSND (attr) < dwarf2_per_objfile->loc.size)
+ && DW_UNSND (attr) < dwarf2_section_size (dwarf2_per_objfile->objfile,
+ &dwarf2_per_objfile->loc))
{
struct dwarf2_loclist_baton *baton;