[RFC] Support command "catch syscall" properly on different targets
Pedro Alves
palves@redhat.com
Tue Mar 3 12:14:00 GMT 2015
On 03/03/2015 11:55 AM, Yao Qi wrote:
> Doug Evans <dje@google.com> writes:
>
>> 1) Do we have a story yet for how to handle differences across
>> multiple targets/inferiors?
>
> I don't have such story in my mind. Taking a look at
> https://sourceware.org/gdb/wiki/MultiTarget and I don't see anything on
> handling differences across multiple targets.
Pasting from:
https://sourceware.org/bugzilla/show_bug.cgi?id=10737#c5
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A related question is how to handle syscalls by name ("catch syscall open"):
#1 - when the user kills the program, and then starts another one, of a different architecture, in the same inferior. E.g.,
- file prog64
- start
- catch syscall open
- kill
- file prog32
- run
#2 - similarly, when a 64-bit inferior execs a 32-bit inferior.
- file prog64
- start
- catch syscall open (2 on 64-bit)
- continue
- inferior execs prog32
- inferior now calls syscall 2, which is something else on i386.
These two cases may end up handled by the breakpoint_re_set machinery.
#3 - in the presence of multiple inferiors, each with its own arch.
- file prog64
- start
- add-inferior -exec prog32
- inferior 2
- start
- catch syscall open
- set schedule-multiple on
- c
- both inferiors call "open"
Here, I don't think we'll catch inferior 1's.
syscall catchpoints is presently inferior-specific; while I think it
should end up with a location per inferior instead, and "open" should be
parsed in each inferior's/location's arch.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>> E.g., while not completely supported today, what if I'm
>> debugging two targets and one supports "catch syscall"
>> and one doesn't? "break" applies across all inferiors
>> (though I really don't like this as a default behaviour),
>> and it would be odd if "catch" didn't work similarly
>> by default.
>
> When GDB goes to multi-target, syscall catchpoint should be skipped for
> targets don't support it, IMO.
Agreed.
>> "catch syscall" is target(arch)-specific.
>> Multi-arch doesn't work today (except for special cases),
>> but we should understand how we want it to work tomorrow.
>> And similarly for all such target-specific commands.
>
> Oh, multi-arch is supported, isn't? done by these two patch sets in
> both GDB and GDBserver side respectively,
>
> https://sourceware.org/ml/gdb-patches/2012-11/msg00228.html
> https://sourceware.org/ml/gdb-patches/2013-05/msg01057.html
Yeah.
> In the future, IMHO, each command has a scope, a term from itset
> patches, and the command is applied to the given scope. The scope
> is a set of targets, inferiors and threads. If "catch syscall" command
> is applied to a scope in which one target doesn't support it, GDB can
> report an error like "Target foo in scope bar doesn't support
> 'catch syscall'".
>
*nod*
FYI, I'm getting very close to posting the all-stop-on-top-of-non-stop
patch. The remaining dependency (that I had identified) was the
moribund locations rework posted recently. Itsets will follow.
Thanks,
Pedro Alves
More information about the Gdb-patches
mailing list