This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
Re: [RFC] reviving 'catch syscall' for gdbserver
- From: Philippe Waroquiers <philippe dot waroquiers at skynet dot be>
- To: Josh Stone <jistone at redhat dot com>
- Cc: gdb-patches at sourceware dot org, sergiodj at redhat dot com, palves at redhat dot com
- Date: Sun, 20 Sep 2015 18:53:46 +0200
- Subject: Re: [RFC] reviving 'catch syscall' for gdbserver
- Authentication-results: sourceware.org; auth=none
- References: <55F3838A dot 4010005 at redhat dot com> <1442354461 dot 21802 dot 45 dot camel at skynet dot be> <55FCAF79 dot 7060504 at redhat dot com>
On Fri, 2015-09-18 at 17:42 -0700, Josh Stone wrote:
> On 09/15/2015 03:01 PM, Philippe Waroquiers wrote:
> > On Fri, 2015-09-11 at 18:44 -0700, Josh Stone wrote:
> What about relying on the current target, and use Hg switching? Or is
> it more common for new commands to have an explicit pid? It doesn't
> look like many q packets have a pid, even though many have an action
> specific to one target.
Yes, that will work, and is effectively used for many
operations/packets.
Note that as far as I can see, gdb + gdbserver + multiple arch
inferiors + breakpoints seems somewhat broken.
E.g. I tried 7.10 gdb+gdbserver --multi, with 2 inferiors
of different archs : x86 (badseg) and amd64 (trivialleak).
The way breakpoints are handled seems buggy to me.
E.g. at some point, I had:
(gdb) info break
Num Type Disp Enb Address What
2 breakpoint keep y 0x080484f9 in main at badseg.c:13 inf 2
3 breakpoint keep y 0x000000000040053a in main at trivialleak.c:11 inf 1
(breakpoints set using *0x....)
So, a breakpoint for 'inf 2' and a breakpoint for 'inf 1'.
Then when doing run, gdb reported:
Warning:
Cannot insert breakpoint 2.
Cannot access memory at address 0x80484f9
So, GDB (wronly IMO) tried to insert a breakpoint aimed at the x86 inferior
in the amd64 inferior.
Same problem when running the x86 target: it could not insert the amd64 breakpoint.
What is even more strange is that after that, the info breakpoints gives:
(gdb) info break
Num Type Disp Enb Address What
2 breakpoint keep y 0x080484f9 in main at badseg.c:13 inf 2
3 breakpoint keep y 0x000000000040053a inf 2
So, the breakpoint 3 'was lost' for inferior 1, and was 'transferred' to inferior 2.
I also searched for the regexp 'inf [0-9]' in the doc, and could
not find anything. The description for 'What' in the manual of 'info breakpoints'
does only describe file/line number.
So, this 'inf x' in info breakpoint seems not documented.
More generally, I could not find a description of the behaviour of breakpoints
with multiple inferiors and/or multiple archs inferior.
The doc only says: "Many commands will work the same with multiple programs as with a
single program ..."
No more details found.
Philippe