[14.5/23] Avoid another inferior_ptid reference in gdb/remote.c (Re: [PATCH 14/23] Tweak handling of remote errors in response to resumption packet)
Commit Message
On 10/9/19 2:34 PM, Aktemur, Tankut Baris wrote:
> * On September 7, 2019 1:28 AM, Pedro Alves wrote:
> A similar problem could occur in case of an exit event, too -- for instance,
> if the remote target does not support the multi-process packet or if the
> packet is disabled.
>
> This can be checked by modifying the test
>
> testsuite/gdb.server/connect-without-multi-process.exp
>
> to continue the inferior to termination.
Oh, excellent, this is the same issue that Philippe discovered with
Valgrind, for which I sent a patch earlier:
https://sourceware.org/ml/gdb-patches/2019-10/msg00512.html
I did not realize you had already analyzed it. I was having second
thoughts on whether we can use general_thread, and for that I like
your patch better than mine. In haste, had completely forgot that
patch #14 added first_remote_resumed_thread. Also, I wrote a new test
from scratch, not realizing we already had connect-without-multi-process.exp.
Sigh. Well, I actually originally wrote that one too, so I just
completely forgot it. :-D Thanks for finding it.
> I'm attaching these as a patch in case one wants to test. It should be applied
> after the main multi-target patch.
I tweaked it a bit further, reused the commit log from my version of
the patch, and rebased it on top of patch #14. Here it is:
From 25f279aa79a9860c64d228a9eb7fc974c2367c64 Mon Sep 17 00:00:00 2001
From: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Date: Thu, 17 Oct 2019 01:34:19 +0100
Subject: [PATCH] Avoid another inferior_ptid reference in gdb/remote.c
The multi-target patch makes inferior_ptid point to null_ptid before
calling into target_wait, which catches bad uses of inferior_ptid,
since the current selected thread in gdb shouldn't have much relation
to the thread that reports an event.
One such bad use is found in remote_target::remote_parse_stop_reply,
where we handle the 'W' or 'X' packets (process exit), and the remote
target does not support the multi-process extensions, i.e., it does
not report the PID of the process that exited.
With the multi-target patch, that would result in a failed assertion,
trying to find the inferior for process pid 0.
gdb/ChangeLog:
yyyy-mm-dd Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Pedro Alves <palves@redhat.com>
* remote.c (remote_target::remote_parse_stop_reply) <W/X packets>:
If no process is specified, return null_ptid instead of
inferior_ptid.
(remote_target::wait_as): Handle TARGET_WAITKIND_EXITED /
TARGET_WAITKIND_SIGNALLED with no pid.
gdb/testsuite/ChangeLog:
yyyy-mm-dd Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Pedro Alves <palves@redhat.com>
* gdb.server/connect-without-multi-process.exp: Also test
continuing to end.
---
gdb/remote.c | 18 +++++++++++++-----
.../gdb.server/connect-without-multi-process.exp | 7 ++++++-
2 files changed, 19 insertions(+), 6 deletions(-)
Comments
* On Thursday, October 17, 2019 2:54 AM, Pedro Alves wrote:
>
> On 10/9/19 2:34 PM, Aktemur, Tankut Baris wrote:
> > * On September 7, 2019 1:28 AM, Pedro Alves wrote:
>
> > A similar problem could occur in case of an exit event, too -- for instance,
> > if the remote target does not support the multi-process packet or if the
> > packet is disabled.
> >
> > This can be checked by modifying the test
> >
> > testsuite/gdb.server/connect-without-multi-process.exp
> >
> > to continue the inferior to termination.
>
> Oh, excellent, this is the same issue that Philippe discovered with
> Valgrind, for which I sent a patch earlier:
>
> https://sourceware.org/ml/gdb-patches/2019-10/msg00512.html
>
> I did not realize you had already analyzed it. I was having second
> thoughts on whether we can use general_thread, and for that I like
> your patch better than mine. In haste, had completely forgot that
> patch #14 added first_remote_resumed_thread. Also, I wrote a new test
> from scratch, not realizing we already had connect-without-multi-process.exp.
> Sigh. Well, I actually originally wrote that one too, so I just
> completely forgot it. :-D Thanks for finding it.
>
> > I'm attaching these as a patch in case one wants to test. It should be applied
> > after the main multi-target patch.
>
> I tweaked it a bit further, reused the commit log from my version of
> the patch, and rebased it on top of patch #14. Here it is:
Thank you, this looks good to me.
Regards,
-Baris
>
> From 25f279aa79a9860c64d228a9eb7fc974c2367c64 Mon Sep 17 00:00:00 2001
> From: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
> Date: Thu, 17 Oct 2019 01:34:19 +0100
> Subject: [PATCH] Avoid another inferior_ptid reference in gdb/remote.c
>
> The multi-target patch makes inferior_ptid point to null_ptid before
> calling into target_wait, which catches bad uses of inferior_ptid,
> since the current selected thread in gdb shouldn't have much relation
> to the thread that reports an event.
>
> One such bad use is found in remote_target::remote_parse_stop_reply,
> where we handle the 'W' or 'X' packets (process exit), and the remote
> target does not support the multi-process extensions, i.e., it does
> not report the PID of the process that exited.
>
> With the multi-target patch, that would result in a failed assertion,
> trying to find the inferior for process pid 0.
>
> gdb/ChangeLog:
> yyyy-mm-dd Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
> Pedro Alves <palves@redhat.com>
>
> * remote.c (remote_target::remote_parse_stop_reply) <W/X packets>:
> If no process is specified, return null_ptid instead of
> inferior_ptid.
> (remote_target::wait_as): Handle TARGET_WAITKIND_EXITED /
> TARGET_WAITKIND_SIGNALLED with no pid.
>
> gdb/testsuite/ChangeLog:
> yyyy-mm-dd Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
> Pedro Alves <palves@redhat.com>
>
> * gdb.server/connect-without-multi-process.exp: Also test
> continuing to end.
> ---
> gdb/remote.c | 18 +++++++++++++-----
> .../gdb.server/connect-without-multi-process.exp | 7 ++++++-
> 2 files changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/gdb/remote.c b/gdb/remote.c
> index 8f3fdf098d..ad8a14d80b 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -7446,7 +7446,6 @@ Packet: '%s'\n"),
> case 'W': /* Target exited. */
> case 'X':
> {
> - int pid;
> ULONGEST value;
>
> /* GDB used to accept only 2 hex chars here. Stubs should
> @@ -7470,8 +7469,9 @@ Packet: '%s'\n"),
> event->ws.value.sig = GDB_SIGNAL_UNKNOWN;
> }
>
> - /* If no process is specified, assume inferior_ptid. */
> - pid = inferior_ptid.pid ();
> + /* If no process is specified, return null_ptid, and let the
> + caller figure out the right process to use. */
> + int pid = 0;
> if (*p == '\0')
> ;
> else if (*p == ';')
> @@ -7847,8 +7847,16 @@ remote_target::wait_as (ptid_t ptid, target_waitstatus *status, int options)
> event_ptid = first_remote_resumed_thread ();
> }
> else
> - /* A process exit. Invalidate our notion of current thread. */
> - record_currthread (rs, minus_one_ptid);
> + {
> + /* A process exit. Invalidate our notion of current thread. */
> + record_currthread (rs, minus_one_ptid);
> + /* It's possible that the packet did not include a pid. */
> + if (event_ptid == null_ptid)
> + event_ptid = first_remote_resumed_thread ();
> + /* EVENT_PTID could still be NULL_PTID. Double-check. */
> + if (event_ptid == null_ptid)
> + event_ptid = magic_null_ptid;
> + }
>
> return event_ptid;
> }
> diff --git a/gdb/testsuite/gdb.server/connect-without-multi-process.exp b/gdb/testsuite/gdb.server/connect-without-
> multi-process.exp
> index fba20a6a0b..6ba35bf508 100644
> --- a/gdb/testsuite/gdb.server/connect-without-multi-process.exp
> +++ b/gdb/testsuite/gdb.server/connect-without-multi-process.exp
> @@ -14,7 +14,7 @@
> # along with this program. If not, see <http://www.gnu.org/licenses/>. */
>
> # Check that we can connect to GDBserver with the multiprocess
> -# extensions disabled, and run to main.
> +# extensions disabled, run to main, and finish the process.
>
> load_lib gdbserver-support.exp
>
> @@ -52,6 +52,11 @@ proc do_test {multiprocess} {
> "target $gdbserver_protocol"
>
> gdb_test "continue" "main .*" "continue to main"
> +
> + # The W/X packets do not include the PID of the exiting process
> + # without the multi-process extensions. Check that we handle
> + # process exit correctly in that case.
> + gdb_continue_to_end
> }
>
> foreach multiprocess { "off" "auto" } {
> --
> 2.14.5
>
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Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Christin Eisenschmid, Gary Kershaw
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Commercial Register: Amtsgericht Muenchen HRB 186928
@@ -7446,7 +7446,6 @@ Packet: '%s'\n"),
case 'W': /* Target exited. */
case 'X':
{
- int pid;
ULONGEST value;
/* GDB used to accept only 2 hex chars here. Stubs should
@@ -7470,8 +7469,9 @@ Packet: '%s'\n"),
event->ws.value.sig = GDB_SIGNAL_UNKNOWN;
}
- /* If no process is specified, assume inferior_ptid. */
- pid = inferior_ptid.pid ();
+ /* If no process is specified, return null_ptid, and let the
+ caller figure out the right process to use. */
+ int pid = 0;
if (*p == '\0')
;
else if (*p == ';')
@@ -7847,8 +7847,16 @@ remote_target::wait_as (ptid_t ptid, target_waitstatus *status, int options)
event_ptid = first_remote_resumed_thread ();
}
else
- /* A process exit. Invalidate our notion of current thread. */
- record_currthread (rs, minus_one_ptid);
+ {
+ /* A process exit. Invalidate our notion of current thread. */
+ record_currthread (rs, minus_one_ptid);
+ /* It's possible that the packet did not include a pid. */
+ if (event_ptid == null_ptid)
+ event_ptid = first_remote_resumed_thread ();
+ /* EVENT_PTID could still be NULL_PTID. Double-check. */
+ if (event_ptid == null_ptid)
+ event_ptid = magic_null_ptid;
+ }
return event_ptid;
}
@@ -14,7 +14,7 @@
# along with this program. If not, see <http://www.gnu.org/licenses/>. */
# Check that we can connect to GDBserver with the multiprocess
-# extensions disabled, and run to main.
+# extensions disabled, run to main, and finish the process.
load_lib gdbserver-support.exp
@@ -52,6 +52,11 @@ proc do_test {multiprocess} {
"target $gdbserver_protocol"
gdb_test "continue" "main .*" "continue to main"
+
+ # The W/X packets do not include the PID of the exiting process
+ # without the multi-process extensions. Check that we handle
+ # process exit correctly in that case.
+ gdb_continue_to_end
}
foreach multiprocess { "off" "auto" } {