diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2015-10-12 10:02:52 +0200 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2015-10-29 17:59:26 +0000 |
| commit | 1138f24645e9e1e2d55d280caab4e2539dfcdb49 (patch) | |
| tree | fd5f95413812b7f0929ae4cfc0ae557162440cac | |
| parent | 7bc8e0c967a4ef77657174d28af775691e18b4ce (diff) | |
qemu-gdb: allow using glibc_pointer_guard() on core dumps
get_fs_base() cannot be run on a core dump, because it uses the arch_prctl
system call. The fs base is the value that is returned by pthread_self(),
and it would be nice to just glean it from the "info threads" output:
* 1 Thread 0x7f16a3fff700 (LWP 33642) pthread_cond_wait@@GLIBC_2.3.2 ()
^^^^^^^^^^^^^^
but unfortunately the gdb API does not provide that. Instead, we can
look for the "arg" argument of the start_thread function if glibc debug
information are available. If not, fall back to the old mechanism.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1444636974-19950-2-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
| -rw-r--r-- | scripts/qemugdb/coroutine.py | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/scripts/qemugdb/coroutine.py b/scripts/qemugdb/coroutine.py index 3c54918b5d..b1d4546fe6 100644 --- a/scripts/qemugdb/coroutine.py +++ b/scripts/qemugdb/coroutine.py @@ -16,7 +16,8 @@ import gdb def get_fs_base(): - '''Fetch %fs base value using arch_prctl(ARCH_GET_FS)''' + '''Fetch %fs base value using arch_prctl(ARCH_GET_FS). This is + pthread_self().''' # %rsp - 120 is scratch space according to the SystemV ABI old = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)') gdb.execute('call arch_prctl(0x1003, $rsp - 120)', False, True) @@ -24,9 +25,22 @@ def get_fs_base(): gdb.execute('set *(uint64_t*)($rsp - 120) = %s' % old, False, True) return fs_base +def pthread_self(): + '''Fetch pthread_self() from the glibc start_thread function.''' + f = gdb.newest_frame() + while f.name() != 'start_thread': + f = f.older() + if f is None: + return get_fs_base() + + try: + return f.read_var("arg") + except ValueError: + return get_fs_base() + def get_glibc_pointer_guard(): '''Fetch glibc pointer guard value''' - fs_base = get_fs_base() + fs_base = pthread_self() return gdb.parse_and_eval('*(uint64_t*)((uint64_t)%s + 0x30)' % fs_base) def glibc_ptr_demangle(val, pointer_guard): |