[patch] Fix assert crashes with minidebuginfo

Jan Kratochvil
2013-02-01T18:21:51Z

Hi Tom,

original bugreport:
https://bugzilla.redhat.com/show_bug.cgi?id=903522

in some cases GDB added separate debug info to minidebuginfo (which itself is
a separate debug info). separate debug info of a separate debug info is not
supported by GDB and it caused a gdb_assert failure.

So the added gdb_assert calls print such violation immediately at
add_separate_debug_objfile, not only in a some rare case found by the
bugreport.

And I have found multiple such fragile checks in GDB so I have protected them
all so that minidebuginfo is always only a sole separate debug info.

No regressions on {x86_64,x86_64-m32,i686}-fedora19pre-linux-gnu.

With the new gdb_asserts (and without the fix) GDB crashes on gdb.gdb/ tests
due to current ncurses-libs-5.9-7.20121017.fc19.x86_64 files.

Thanks,
Jan

gdb/
2013-02-01 Jan Kratochvil <jan.kratochvil@redhat.com>

* elfread.c (elf_symfile_read): Limit separate debug info additions to
files with no separate debug info.
* objfiles.c (add_separate_debug_objfile): Add gdb_assert calls.
* symfile.c (read_symbols): Call find_separate_debug_file_in_section
only for files with no separate debug info.

gdb/testsuite/
2013-02-01 Jan Kratochvil <jan.kratochvil@redhat.com>

* gdb.base/gnu-debugdata.exp): Create ${binfile}.debug,
${binfile}.mini_debuginfo-debuglink, add -k to xz, use now
${binfile}.mini_debuginfo-debuglink and
${binfile}.mini_debuginfo-debuglink.xz.

diff --git a/gdb/elfread.c b/gdb/elfread.c
index 9d630cd..6ca659f 100644
--- a/gdb/elfread.c
+++ b/gdb/elfread.c
@@ -1431,8 +1431,18 @@ elf_symfile_read (struct objfile *objfile, int symfile_flags)
/* If the file has its own symbol tables it has no separate debug
info. `.dynsym'/`.symtab' go to MSYMBOLS, `.debug_info' goes to
SYMTABS/PSYMTABS. `.gnu_debuglink' may no longer be present with
- `.note.gnu.build-id'. */
- else if (!objfile_has_partial_symbols (objfile))
+ `.note.gnu.build-id'.
+
+ .gnu_debugdata is !objfile_has_partial_symbols because it contains only
+ .symtab, not .debug_* section. But if we already added .gnu_debugdata as
+ an objfile via find_separate_debug_file_in_section there was no separate
+ debug info available. Therefore do not attempt to search for another one,
+ objfile->separate_debug_objfile->separate_debug_objfile GDB guarantees to
+ be NULL and we would possibly violate it. */
+
+ else if (!objfile_has_partial_symbols (objfile)
+ && objfile->separate_debug_objfile == NULL
+ && objfile->separate_debug_objfile_backlink == NULL)
{
char *debugfile;

diff --git a/gdb/objfiles.c b/gdb/objfiles.c
index 5232c8f..5829699 100644
--- a/gdb/objfiles.c
+++ b/gdb/objfiles.c
@@ -476,6 +476,9 @@ add_separate_debug_objfile (struct objfile *objfile, struct objfile *parent)
/* Must not be already in a list. */
gdb_assert (objfile->separate_debug_objfile_backlink == NULL);
gdb_assert (objfile->separate_debug_objfile_link == NULL);
+ gdb_assert (objfile->separate_debug_objfile == NULL);
+ gdb_assert (parent->separate_debug_objfile_backlink == NULL);
+ gdb_assert (parent->separate_debug_objfile_link == NULL);

objfile->separate_debug_objfile_backlink = parent;
objfile->separate_debug_objfile_link = parent->separate_debug_objfile;
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 63bf329..6f968b7 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -823,7 +823,12 @@ static void
read_symbols (struct objfile *objfile, int add_flags)
{
(*objfile->sf->sym_read) (objfile, add_flags);
- if (!objfile_has_partial_symbols (objfile))
+
+ /* find_separate_debug_file_in_section should be called only if there is
+ single binary with no existing separate debug info file. */
+ if (!objfile_has_partial_symbols (objfile)
+ && objfile->separate_debug_objfile == NULL
+ && objfile->separate_debug_objfile_backlink == NULL)
{
bfd *abfd = find_separate_debug_file_in_section (objfile);
struct cleanup *cleanup = make_cleanup_bfd_unref (abfd);
diff --git a/gdb/testsuite/gdb.base/gnu-debugdata.exp b/gdb/testsuite/gdb.base/gnu-debugdata.exp
index f34e4e8..55aa3c6 100644
--- a/gdb/testsuite/gdb.base/gnu-debugdata.exp
+++ b/gdb/testsuite/gdb.base/gnu-debugdata.exp
@@ -127,14 +127,30 @@ if {[run "strip" [transform strip] \
return -1
}

+# Separate full debug info into ${binfile}.debug.
+remote_file host delete ${binfile}.debug
+if {[run "copydebug" [transform objcopy] \
+ "--only-keep-debug ${binfile} ${binfile}.debug"]} {
+ return -1
+}
+
+# Add the .gnu_debuglink section to the .gnu_debugdata file.
+# .gnu_debuglink is normally not present in the .gnu_debugdata section but in
+# some files there may be PT_NOTE with NT_GNU_BUILD_ID and GDB could look up
+# the .debug file from it.
+if {[run "addlink" [transform objcopy] \
+ "--add-gnu-debuglink=${binfile}.debug ${binfile}.mini_debuginfo ${binfile}.mini_debuginfo-debuglink"]} {
+ return -1
+}
+
# Inject the compressed data into the .gnu_debugdata section of the
# original binary.
-remote_file host delete ${binfile}.mini_debuginfo.xz
-if {[run "xz" "xz" "${binfile}.mini_debuginfo"]} {
+remote_file host delete ${binfile}.mini_debuginfo-debuglink.xz
+if {[run "xz" "xz" "-k ${binfile}.mini_debuginfo-debuglink"]} {
return -1
}
remote_file host delete ${binfile}.test
-if {[run "objcopy 2" [transform objcopy] "--add-section .gnu_debugdata=${binfile}.mini_debuginfo.xz ${binfile}.strip ${binfile}.test"]} {
+if {[run "objcopy 2" [transform objcopy] "--add-section .gnu_debugdata=${binfile}.mini_debuginfo-debuglink.xz ${binfile}.strip ${binfile}.test"]} {
return -1
}