S390: Add use of unavailable-stack frame ID
Commit Message
When determining the frame ID of an inline frame, GDB currently asserts
that a valid ID of the underlying real frame is found, and that it does
not match outer_frame_id. From inline_frame_this_id():
/* For now, require we don't match outer_frame_id either (see
comment above). */
gdb_assert (!frame_id_eq (*this_id, outer_frame_id));
However, this assertion may fail when the real frame's unwinder can not
determine the frame ID. This happened on an s390x target with a binary
that lacked call frame information and also confused the prologue
analyzer, because then s390_frame_this_id() left the frame ID at its
default.
To fix this, this change enhances s390_frame_this_id such that an
unavailable-stack frame ID is built if no frame base can be determined
but the function address is available.
gdb/ChangeLog:
* s390-linux-tdep.c (s390_prologue_frame_unwind_cache): Store
frame func's PC in info->func before any other failure can occur.
(s390_frame_this_id): Use frame_id_build_unavailable_stack if
info->func has been filled out.
---
gdb/s390-linux-tdep.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
Comments
Pushed.
On Mon, Mar 07 2016, Andreas Arnez wrote:
> When determining the frame ID of an inline frame, GDB currently asserts
> that a valid ID of the underlying real frame is found, and that it does
> not match outer_frame_id. From inline_frame_this_id():
>
> /* For now, require we don't match outer_frame_id either (see
> comment above). */
> gdb_assert (!frame_id_eq (*this_id, outer_frame_id));
>
> However, this assertion may fail when the real frame's unwinder can not
> determine the frame ID. This happened on an s390x target with a binary
> that lacked call frame information and also confused the prologue
> analyzer, because then s390_frame_this_id() left the frame ID at its
> default.
>
> To fix this, this change enhances s390_frame_this_id such that an
> unavailable-stack frame ID is built if no frame base can be determined
> but the function address is available.
>
> gdb/ChangeLog:
>
> * s390-linux-tdep.c (s390_prologue_frame_unwind_cache): Store
> frame func's PC in info->func before any other failure can occur.
> (s390_frame_this_id): Use frame_id_build_unavailable_stack if
> info->func has been filled out.
On 03/07/2016 10:19 AM, Andreas Arnez wrote:
> When determining the frame ID of an inline frame, GDB currently asserts
> that a valid ID of the underlying real frame is found, and that it does
> not match outer_frame_id. From inline_frame_this_id():
>
> /* For now, require we don't match outer_frame_id either (see
> comment above). */
> gdb_assert (!frame_id_eq (*this_id, outer_frame_id));
>
> However, this assertion may fail when the real frame's unwinder can not
> determine the frame ID. This happened on an s390x target with a binary
> that lacked call frame information and also confused the prologue
> analyzer, because then s390_frame_this_id() left the frame ID at its
> default.
>
> To fix this, this change enhances s390_frame_this_id such that an
> unavailable-stack frame ID is built if no frame base can be determined
> but the function address is available.
>
Seeing all these makes me want this:
https://sourceware.org/ml/gdb-patches/2016-02/msg00778.html
even more. :-)
Thanks,
Pedro Alves
On Thu, Mar 10 2016, Pedro Alves wrote:
> On 03/07/2016 10:19 AM, Andreas Arnez wrote:
>> When determining the frame ID of an inline frame, GDB currently asserts
>> that a valid ID of the underlying real frame is found, and that it does
>> not match outer_frame_id. From inline_frame_this_id():
>>
>> /* For now, require we don't match outer_frame_id either (see
>> comment above). */
>> gdb_assert (!frame_id_eq (*this_id, outer_frame_id));
>>
>> However, this assertion may fail when the real frame's unwinder can not
>> determine the frame ID. This happened on an s390x target with a binary
>> that lacked call frame information and also confused the prologue
>> analyzer, because then s390_frame_this_id() left the frame ID at its
>> default.
>>
>> To fix this, this change enhances s390_frame_this_id such that an
>> unavailable-stack frame ID is built if no frame base can be determined
>> but the function address is available.
>>
>
> Seeing all these makes me want this:
>
> https://sourceware.org/ml/gdb-patches/2016-02/msg00778.html
>
> even more. :-)
Agreed. It's on Yao's todo list, right? ;-) --
https://sourceware.org/ml/gdb-patches/2016-02/msg00858.html
--
Andreas
Andreas Arnez <arnez@linux.vnet.ibm.com> writes:
>> Seeing all these makes me want this:
>>
>> https://sourceware.org/ml/gdb-patches/2016-02/msg00778.html
>>
>> even more. :-)
>
> Agreed. It's on Yao's todo list, right? ;-) --
>
> https://sourceware.org/ml/gdb-patches/2016-02/msg00858.html
Yes, but it is in the bottom. Your patch is a good evidence that we
need to fix all "unavailable stack" stuff in target independent part.
@@ -2011,9 +2011,12 @@ s390_prologue_frame_unwind_cache (struct frame_info *this_frame,
bother searching for it -- with modern compilers this would be mostly
pointless anyway. Trust that we'll either have valid DWARF-2 CFI data
or else a valid backchain ... */
- func = get_frame_func (this_frame);
- if (!func)
- return 0;
+ if (!get_frame_func_if_available (this_frame, &info->func))
+ {
+ info->func = -1;
+ return 0;
+ }
+ func = info->func;
/* Try to analyze the prologue. */
result = s390_analyze_prologue (gdbarch, func,
@@ -2167,7 +2170,6 @@ s390_prologue_frame_unwind_cache (struct frame_info *this_frame,
info->local_base = prev_sp - size;
}
- info->func = func;
return 1;
}
@@ -2267,7 +2269,11 @@ s390_frame_this_id (struct frame_info *this_frame,
= s390_frame_unwind_cache (this_frame, this_prologue_cache);
if (info->frame_base == -1)
- return;
+ {
+ if (info->func != -1)
+ *this_id = frame_id_build_unavailable_stack (info->func);
+ return;
+ }
*this_id = frame_id_build (info->frame_base, info->func);
}