|
 |
0a406a |
From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
|
|
|
0a406a |
From: Keith Seitz <keiths@redhat.com>
|
|
|
0a406a |
Date: Thu, 25 Mar 2021 10:31:48 -0700
|
|
|
0a406a |
Subject: gdb-rhbz1931344-bfd_seek-elf_read_notes.patch
|
|
|
0a406a |
|
|
|
0a406a |
;; Backport "Save/restore file offset while reading notes in core file"
|
|
|
0a406a |
;; (Keith Seitz, RHBZ 1931344)
|
|
|
0a406a |
|
|
|
0a406a |
A recent bug (RH BZ 1931344) has exposed a bug in the core file
|
|
|
0a406a |
build-ID support that I introduced a while ago. It is pretty
|
|
|
0a406a |
easy to demonstate the problem following a simplified procedure
|
|
|
0a406a |
outlined in that bug:
|
|
|
0a406a |
|
|
|
0a406a |
[shell1]
|
|
|
0a406a |
shell1$ /usr/libexec/qemu-kvm
|
|
|
0a406a |
|
|
|
0a406a |
[shell2]
|
|
|
0a406a |
shell2$ pkill -SEGV -x qemu-kvm
|
|
|
0a406a |
|
|
|
0a406a |
[shell1]
|
|
|
0a406a |
Segmentation fault (core dumped)
|
|
|
0a406a |
|
|
|
0a406a |
Load this core file into GDB without specifying an executable
|
|
|
0a406a |
(an unfortunate Fedora/RHEL-ism), and GDB will inform the user
|
|
|
0a406a |
to install debuginfo for the "missing" executable:
|
|
|
0a406a |
|
|
|
0a406a |
$ gdb -nx -q core.12345
|
|
|
0a406a |
...
|
|
|
0a406a |
Missing separate debuginfo for the main executable file
|
|
|
0a406a |
Try: dnf --enablerepo='*debug*' install /usr/lib/debug/.build-id/e2/e9c66d3117fb2bbb5b2be122f04f2664e5df54
|
|
|
0a406a |
Core was generated by `/usr/libexec/qemu-kvm'.
|
|
|
0a406a |
Program terminated with signal SIGSEGV, Segmentation fault.
|
|
|
0a406a |
...
|
|
|
0a406a |
|
|
|
0a406a |
The suggested build-ID is actaully for gmp not qemu-kvm. The problem
|
|
|
0a406a |
lies in _bfd_elf_core_find_build_id, where we loop over program headers
|
|
|
0a406a |
looking for note segments:
|
|
|
0a406a |
|
|
|
0a406a |
/* Read in program headers and parse notes. */
|
|
|
0a406a |
for (i = 0; i < i_ehdr.e_phnum; ++i, ++i_phdr)
|
|
|
0a406a |
{
|
|
|
0a406a |
Elf_External_Phdr x_phdr;
|
|
|
0a406a |
|
|
|
0a406a |
if (bfd_bread (&x_phdr, sizeof (x_phdr), abfd) != sizeof (x_phdr))
|
|
|
0a406a |
goto fail;
|
|
|
0a406a |
elf_swap_phdr_in (abfd, &x_phdr, i_phdr);
|
|
|
0a406a |
|
|
|
0a406a |
if (i_phdr->p_type == PT_NOTE && i_phdr->p_filesz > 0)
|
|
|
0a406a |
{
|
|
|
0a406a |
elf_read_notes (abfd, offset + i_phdr->p_offset,
|
|
|
0a406a |
i_phdr->p_filesz, i_phdr->p_align);
|
|
|
0a406a |
|
|
|
0a406a |
if (abfd->build_id != NULL)
|
|
|
0a406a |
return TRUE;
|
|
|
0a406a |
}
|
|
|
0a406a |
|
|
|
0a406a |
elf_read_notes uses bfd_seek to forward the stream to the location of
|
|
|
0a406a |
the note segment. When control returns to _bfd_elf_core_fild_build_id,
|
|
|
0a406a |
the stream is no longer in the location looking at program headers, and
|
|
|
0a406a |
all subsequent reads will read from the wrong file offset.
|
|
|
0a406a |
|
|
|
0a406a |
To fix this, this patch marks the stream location and ensures
|
|
|
0a406a |
that it is restored after elf_read_notes is called.
|
|
|
0a406a |
|
|
|
0a406a |
bfd/ChangeLog
|
|
|
0a406a |
2021-03-26 Keith Seitz <keiths@redhat.com>
|
|
|
0a406a |
|
|
|
0a406a |
* elfcore.h (_bfd_elf_core_find_build_id): Seek file
|
|
|
0a406a |
offset of program headers after calling elf_read_notes.
|
|
|
0a406a |
|
|
|
0a406a |
diff --git a/bfd/elfcore.h b/bfd/elfcore.h
|
|
|
0a406a |
--- a/bfd/elfcore.h
|
|
|
0a406a |
+++ b/bfd/elfcore.h
|
|
|
0a406a |
@@ -410,6 +410,13 @@ NAME(_bfd_elf, core_find_build_id)
|
|
|
0a406a |
{
|
|
|
0a406a |
elf_read_notes (abfd, offset + i_phdr->p_offset,
|
|
|
0a406a |
i_phdr->p_filesz, i_phdr->p_align);
|
|
|
0a406a |
+
|
|
|
0a406a |
+ /* Make sure ABFD returns to processing the program headers. */
|
|
|
0a406a |
+ if (bfd_seek (abfd, (file_ptr) (offset + i_ehdr.e_phoff
|
|
|
0a406a |
+ + (i + 1) * sizeof (x_phdr)),
|
|
|
0a406a |
+ SEEK_SET) != 0)
|
|
|
0a406a |
+ goto fail;
|
|
|
0a406a |
+
|
|
|
0a406a |
if (abfd->build_id != NULL)
|
|
|
0a406a |
return TRUE;
|
|
|
0a406a |
}
|