[PATCH+7.10.1] PR remote/18965: vforkdone stop reply should indicate parent PID

[PATCH+7.10.1] PR remote/18965: vforkdone stop reply should indicate parent PID

[Pedro Alves]

Hi Eli,

Are the doc bits OK?

I'd like to push this to the 7.10 branch too, so I filed a PR.

From 5e5467a6d2efe08f91e5e79edecc5d15ab8e2eb6 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Tue, 15 Sep 2015 17:05:41 +0100
Subject: [PATCH] PR remote/18965: vforkdone stop reply should indicate parent
 PID

The vforkdone stop reply misses indicating the thread ID of the vfork
parent which the event relates to:

 @cindex vfork events, remote reply
 @item vfork
 The packet indicates that @code{vfork} was called, and @var{r}
 is the thread ID of the new child process. Refer to
 @ref{thread-id syntax} for the format of the @var{thread-id}
 field.  This packet is only applicable to targets that support
 vfork events.

 @cindex vforkdone events, remote reply
 @item vforkdone
 The packet indicates that a child process created by a vfork
 has either called @code{exec} or terminated, so that the
 address spaces of the parent and child process are no longer
 shared. The @var{r} part is ignored.  This packet is only
 applicable to targets that support vforkdone events.

Unfortunately, this is not just a documentation issue.  GDBserver
is really not specifying the thread ID.  I noticed because
in non-stop mode, gdb complains:

 [Thread 6089.6089] #1 stopped.
 #0  0x0000003615a011f0 in ?? ()
 0x0000003615a011f0 in ?? ()
 (gdb) set debug remote 1
 (gdb) c
 Continuing.
 Sending packet: $QPassSignals:e;10;14;17;1a;1b;1c;21;24;25;2c;4c;#5f...Packet received: OK
 Sending packet: $vCont;c:p17c9.17c9#88...Packet received: OK
   Notification received: Stop:T05vfork:p17ce.17ce;06:40d7ffffff7f0000;07:30d7ffffff7f0000;10:e4c9eb1536000000;thread:p17c9.17c9;core:2;
 Sending packet: $vStopped#55...Packet received: OK
 Sending packet: $D;17ce#af...Packet received: OK
 Sending packet: $vCont;c:p17c9.17c9#88...Packet received: OK
   Notification received: Stop:T05vforkdone:;
 No process or thread specified in stop reply: T05vforkdone:;
 (gdb)

This is not non-stop-mode-specific, however.  Consider e.g., that in
all-stop, you may be debugging more than one process at the same time.
You continue, and both processes vfork.  So when you next get a
T05vforkdone, there's no way to tell which of the parent processes is
done with the vfork.

Tests will be added later.

Tested on x86_64 Fedora 20.

gdb/ChangeLog:
2015-09-15  Pedro Alves  <palves@redhat.com>

	PR remote/18965
	* remote-utils.c (prepare_resume_reply): Merge
	TARGET_WAITKIND_VFORK_DONE switch case with the
	TARGET_WAITKIND_FORKED case.

gdb/doc/ChangeLog:
2015-09-15  Pedro Alves  <palves@redhat.com>

	PR remote/18965
	* gdb.texinfo (Stop Reply Packets): Explain that vforkdone's 'r'
	part indicates the thread ID of the parent process.
---
 gdb/ChangeLog                |  7 +++++++
 gdb/doc/ChangeLog            |  6 ++++++
 gdb/doc/gdb.texinfo          | 11 ++++++-----
 gdb/gdbserver/remote-utils.c | 17 +++++++----------
 4 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9932d60..d19c71a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2015-09-15  Pedro Alves  <palves@redhat.com>
+
+	PR remote/18965
+	* remote-utils.c (prepare_resume_reply): Merge
+	TARGET_WAITKIND_VFORK_DONE switch case with the
+	TARGET_WAITKIND_FORKED case.
+
 2015-09-15  Yao Qi  <yao.qi@linaro.org>

 	* aarch64-linux-nat.c (aarch64_linux_can_do_single_step): New
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index b5de969..2cc6039 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,9 @@
+2015-09-15  Pedro Alves  <palves@redhat.com>
+
+	PR remote/18965
+	* gdb.texinfo (Stop Reply Packets): Explain that vforkdone's 'r'
+	part indicates the thread ID of the parent process.
+
 2015-09-15  Yao Qi  <yao.qi@linaro.org>

 	* gdb.texinfo (General Query Packets): Add vContSupported to
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 4ecdb8f..e80e695 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35498,11 +35498,12 @@ indicating support.

 @cindex vforkdone events, remote reply
 @item vforkdone
-The packet indicates that a child process created by a vfork
-has either called @code{exec} or terminated, so that the
-address spaces of the parent and child process are no longer
-shared. The @var{r} part is ignored.  This packet is only
-applicable to targets that support vforkdone events.
+The packet indicates that a child process created by a vfork has
+either called @code{exec} or terminated, so that the address spaces of
+the parent and child process are no longer shared.  The @var{r} part
+is the thread ID of the parent process.  Refer to @ref{thread-id
+syntax} for the format of the @var{thread-id} field.  This packet is
+only applicable to targets that support vforkdone events.

 This packet should not be sent by default; older @value{GDBN} versions
 did not support it.  @value{GDBN} requests it, by supplying an
diff --git a/gdb/gdbserver/remote-utils.c b/gdb/gdbserver/remote-utils.c
index ac86dd5..78fbfac 100644
--- a/gdb/gdbserver/remote-utils.c
+++ b/gdb/gdbserver/remote-utils.c
@@ -1117,6 +1117,7 @@ prepare_resume_reply (char *buf, ptid_t ptid,
     case TARGET_WAITKIND_STOPPED:
     case TARGET_WAITKIND_FORKED:
     case TARGET_WAITKIND_VFORKED:
+    case TARGET_WAITKIND_VFORK_DONE:
     case TARGET_WAITKIND_EXECD:
       {
 	struct thread_info *saved_thread;
@@ -1135,6 +1136,12 @@ prepare_resume_reply (char *buf, ptid_t ptid,
 	    buf = write_ptid (buf, status->value.related_pid);
 	    strcat (buf, ";");
 	  }
+	else if (status->kind == TARGET_WAITKIND_VFORK_DONE && report_vfork_events)
+	  {
+	    enum gdb_signal signal = GDB_SIGNAL_TRAP;
+
+	    sprintf (buf, "T%02xvforkdone:;", signal);
+	  }
 	else if (status->kind == TARGET_WAITKIND_EXECD && multi_process)
 	  {
 	    enum gdb_signal signal = GDB_SIGNAL_TRAP;
@@ -1269,16 +1276,6 @@ prepare_resume_reply (char *buf, ptid_t ptid,
       else
 	sprintf (buf, "X%02x", status->value.sig);
       break;
-    case TARGET_WAITKIND_VFORK_DONE:
-      if (report_vfork_events)
-	{
-	  enum gdb_signal signal = GDB_SIGNAL_TRAP;
-
-	  sprintf (buf, "T%02xvforkdone:;", signal);
-	}
-      else
-	sprintf (buf, "T%02x", GDB_SIGNAL_0);
-      break;
     default:
       error ("unhandled waitkind");
       break;
-- 
1.9.3

Re: [PATCH+7.10.1] PR remote/18965: vforkdone stop reply should indicate parent PID

[Eli Zaretskii]

> Date: Tue, 15 Sep 2015 17:20:16 +0100
> From: Pedro Alves <palves@redhat.com>
> CC: GDB Patches <gdb-patches@sourceware.org>,
>         "Breazeal, Don" <donb@codesourcery.com>
> 
> Hi Eli,
> 
> Are the doc bits OK?

Yes, thanks.

Re: [PATCH+7.10.1] PR remote/18965: vforkdone stop reply should indicate parent PID

[Pedro Alves]

On 09/15/2015 05:28 PM, Eli Zaretskii wrote:
>> Date: Tue, 15 Sep 2015 17:20:16 +0100
>> From: Pedro Alves <palves@redhat.com>
>> CC: GDB Patches <gdb-patches@sourceware.org>,
>>         "Breazeal, Don" <donb@codesourcery.com>
>>
>> Hi Eli,
>>
>> Are the doc bits OK?
> 
> Yes, thanks.

Thanks Eli.  However, I realized the docs change was plain wrong.
I've reverted it now, with the patch below.  Sorry about that.

Thanks,
Pedro Alves

From e68fa6f07666ec4726cfef59f641a81244cc2e00 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Tue, 15 Sep 2015 19:29:37 +0100
Subject: [PATCH] gdb/doc: revert previous vforkdone change

The previous manual change was wrong.  The vfork parent thread ID
should be reported with the usual "thread" magic register:

   Sending packet: $vCont;c:p7260.7260#1e...Packet received: OK
 -   Notification received: Stop:T05vforkdone:;
 +   Notification received: Stop:T05vforkdone:;thread:p7260.7260
                                               ^^^^^^^^^^^^^^^^^

This is already how the parent is reported in the vfork/fork events,
and is actually what the fix made gdbserver do.  Following the
documentation change, the event would have been reported like this
instead:

    Notification received: Stop:T05vforkdone:p7260.7260

gdb/doc/ChangeLog:
2015-09-15  Pedro Alves  <palves@redhat.com>

	PR remote/18965
	* gdb.texinfo (Stop Reply Packets): Revert previous change to
	the vforkdone description.
---
 gdb/doc/ChangeLog   |  6 ++++++
 gdb/doc/gdb.texinfo | 11 +++++------
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 2cc6039..1e16e92 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,6 +1,12 @@
 2015-09-15  Pedro Alves  <palves@redhat.com>
 
 	PR remote/18965
+	* gdb.texinfo (Stop Reply Packets): Revert previous change to
+	the vforkdone description.
+
+2015-09-15  Pedro Alves  <palves@redhat.com>
+
+	PR remote/18965
 	* gdb.texinfo (Stop Reply Packets): Explain that vforkdone's 'r'
 	part indicates the thread ID of the parent process.
 
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index e80e695..4ecdb8f 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35498,12 +35498,11 @@ indicating support.
 
 @cindex vforkdone events, remote reply
 @item vforkdone
-The packet indicates that a child process created by a vfork has
-either called @code{exec} or terminated, so that the address spaces of
-the parent and child process are no longer shared.  The @var{r} part
-is the thread ID of the parent process.  Refer to @ref{thread-id
-syntax} for the format of the @var{thread-id} field.  This packet is
-only applicable to targets that support vforkdone events.
+The packet indicates that a child process created by a vfork
+has either called @code{exec} or terminated, so that the
+address spaces of the parent and child process are no longer
+shared. The @var{r} part is ignored.  This packet is only
+applicable to targets that support vforkdone events.
 
 This packet should not be sent by default; older @value{GDBN} versions
 did not support it.  @value{GDBN} requests it, by supplying an
-- 
1.9.3