[RFA/Linux] Ask kernel to kill inferior when GDB terminates
Commit Message
> This makes it sound like "interruptible sleep" is some kind of wedged
> state waiting for a debugger. But, this simply means your process is just
> running as normal, and your test's case, normal means idling. Most likely,
> your test program had a "sleep" call in it. IOW, it'd be in sleep state
> even if had been started outside gdb. Another test program could go
> to "T (stopped)", "R (running)", etc.
You're right. Rev log updated.
> This test must be called unconditionally. current_ptrace_options is
> only initialized once:
>
> void
> linux_enable_event_reporting (pid_t pid)
> {
> /* Check if we have initialized the ptrace features for this
> target. If not, do it now. */
> if (current_ptrace_options == -1)
> linux_check_ptrace_features ();
>
> so if the first process gdbserver debugs is an "attach" process,
> but the second one is not, you'll miss setting PTRACE_O_EXITKILL on
> the second process.
>
> Instead, always call linux_test_for_exitkill, and then in
> linux_enable_event_reporting mask out PTRACE_O_EXITKILL
> from current_ptrace_options if 'attached' is false.
Right again.
Here is an attached patch. Re-tested on x86_64-linux as previously
done.
gdb/ChangeLog:
* nat/linux-ptrace.h (PTRACE_O_EXITKILL): Define if not
already defined.
(linux_enable_event_reporting): Add parameter "attached".
* nat/linux-ptrace.c (linux_test_for_exitkill): New advance
declaration. New function.
(linux_check_ptrace_features): Add linux_test_for_exitkill call.
(linux_enable_event_reporting): Add new parameter "attached".
Do not call ptrace with the PTRACE_O_EXITKILL if ATTACHED is
nonzero.
* linux-nat.c (linux_init_ptrace): Add parameter "attached".
Use it. Update function description.
(linux_child_post_attach, linux_child_post_startup_inferior):
Update call to linux_enable_event_reporting.
gdb/gdbserver/ChangeLog:
* linux-low.c (linux_low_filter_event): Update call to
linux_enable_event_reporting following the addition of
a new parameter to that function.
Thanks, Pedro.
Comments
On 12/16/2014 12:39 AM, Joel Brobecker wrote:
> Here is an attached patch. Re-tested on x86_64-linux as previously
> done.
Looks good. Thanks Joel.
> > Here is an attached patch. Re-tested on x86_64-linux as previously
> > done.
>
> Looks good. Thanks Joel.
Thanks, Pedro. Patch now pushed, with the small ChangeLog fix you
suggested off list.
From 4ad92cbfc3dfdfffe46f20e2b6e8df7a793c9ea7 Mon Sep 17 00:00:00 2001
From: Joel Brobecker <brobecker@adacore.com>
Date: Tue, 11 Nov 2014 10:07:21 +0400
Subject: [PATCH] [Linux] Ask kernel to kill inferior when GDB terminates
This patch enhances GDB on GNU/Linux systems in the situation where
we are debugging an inferior that was created from GDB (as opposed
to attached to), by asking the kernel to kill the inferior if GDB
terminates without doing it itself.
This would typically happen when GDB encounters a problem and
crashes, or when it gets killed by an external process. This can
be observed by starting a program under GDB, and then killing
GDB with signal 9. After GDB is killed, the inferior still remains.
This patch also fixes GDBserver similarly.
This fix is conditional on the kernel supporting the PTRACE_O_EXITKILL
feature. On older kernels, the behavior remains unchanged.
gdb/ChangeLog:
* nat/linux-ptrace.h (PTRACE_O_EXITKILL): Define if not
already defined.
(linux_enable_event_reporting): Add parameter "attached".
* nat/linux-ptrace.c (linux_test_for_exitkill): New advance
declaration. New function.
(linux_check_ptrace_features): Add linux_test_for_exitkill call.
(linux_enable_event_reporting): Add new parameter "attached".
Do not call ptrace with the PTRACE_O_EXITKILL if ATTACHED is
nonzero.
* linux-nat.c (linux_init_ptrace): Add parameter "attached".
Use it. Update function description.
(linux_child_post_attach, linux_child_post_startup_inferior):
Update call to linux_enable_event_reporting.
gdb/gdbserver/ChangeLog:
* linux-low.c (linux_low_filter_event): Update call to
linux_enable_event_reporting following the addition of
a new parameter to that function.
Tested on x86_64-linux, native and native-gdbserver.
I also verified by hand that the inferior gets killed when killing
GDB in the "run" case, while the inferior remains in the "attach"
case. Same for GDBserver.
---
gdb/gdbserver/linux-low.c | 4 +++-
gdb/linux-nat.c | 12 +++++++-----
gdb/nat/linux-ptrace.c | 34 +++++++++++++++++++++++++++++++---
gdb/nat/linux-ptrace.h | 7 ++++++-
4 files changed, 47 insertions(+), 10 deletions(-)
@@ -1878,7 +1878,9 @@ linux_low_filter_event (ptid_t filter_ptid, int lwpid, int wstat)
if (WIFSTOPPED (wstat) && child->must_set_ptrace_flags)
{
- linux_enable_event_reporting (lwpid);
+ struct process_info *proc = find_process_pid (pid_of (thread));
+
+ linux_enable_event_reporting (lwpid, proc->attached);
child->must_set_ptrace_flags = 0;
}
@@ -321,25 +321,27 @@ pull_pid_from_list (struct simple_pid_list **listp, int pid, int *statusp)
}
/* Initialize ptrace warnings and check for supported ptrace
- features given PID. */
+ features given PID.
+
+ ATTACHED should be nonzero iff we attached to the inferior. */
static void
-linux_init_ptrace (pid_t pid)
+linux_init_ptrace (pid_t pid, int attached)
{
- linux_enable_event_reporting (pid);
+ linux_enable_event_reporting (pid, attached);
linux_ptrace_init_warnings ();
}
static void
linux_child_post_attach (struct target_ops *self, int pid)
{
- linux_init_ptrace (pid);
+ linux_init_ptrace (pid, 1);
}
static void
linux_child_post_startup_inferior (struct target_ops *self, ptid_t ptid)
{
- linux_init_ptrace (ptid_get_pid (ptid));
+ linux_init_ptrace (ptid_get_pid (ptid), 0);
}
/* Return the number of known LWPs in the tgid given by PID. */
@@ -307,6 +307,7 @@ linux_child_function (gdb_byte *child_stack)
static void linux_test_for_tracesysgood (int child_pid);
static void linux_test_for_tracefork (int child_pid);
+static void linux_test_for_exitkill (int child_pid);
/* Determine ptrace features available on this target. */
@@ -338,6 +339,8 @@ linux_check_ptrace_features (void)
linux_test_for_tracefork (child_pid);
+ linux_test_for_exitkill (child_pid);
+
/* Clean things up and kill any pending children. */
do
{
@@ -449,19 +452,44 @@ linux_test_for_tracefork (int child_pid)
"(%d, status 0x%x)"), ret, status);
}
-/* Enable reporting of all currently supported ptrace events. */
+/* Determine if PTRACE_O_EXITKILL can be used. */
+
+static void
+linux_test_for_exitkill (int child_pid)
+{
+ int ret;
+
+ ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
+ (PTRACE_TYPE_ARG4) PTRACE_O_EXITKILL);
+
+ if (ret == 0)
+ current_ptrace_options |= PTRACE_O_EXITKILL;
+}
+
+/* Enable reporting of all currently supported ptrace events.
+ ATTACHED should be nonzero if we have attached to the inferior. */
void
-linux_enable_event_reporting (pid_t pid)
+linux_enable_event_reporting (pid_t pid, int attached)
{
+ int ptrace_options;
+
/* Check if we have initialized the ptrace features for this
target. If not, do it now. */
if (current_ptrace_options == -1)
linux_check_ptrace_features ();
+ ptrace_options = current_ptrace_options;
+ if (attached)
+ {
+ /* When attached to our inferior, we do not want the inferior
+ to die with us if we terminate unexpectedly. */
+ ptrace_options &= ~PTRACE_O_EXITKILL;
+ }
+
/* Set the options. */
ptrace (PTRACE_SETOPTIONS, pid, (PTRACE_TYPE_ARG3) 0,
- (PTRACE_TYPE_ARG4) (uintptr_t) current_ptrace_options);
+ (PTRACE_TYPE_ARG4) (uintptr_t) ptrace_options);
}
/* Disable reporting of all currently supported ptrace events. */
@@ -69,6 +69,11 @@ struct buffer;
#endif /* PTRACE_EVENT_FORK */
+#ifndef PTRACE_O_EXITKILL
+/* Only defined in Linux Kernel 3.8 or later. */
+#define PTRACE_O_EXITKILL 0x00100000
+#endif
+
#if (defined __bfin__ || defined __frv__ || defined __sh__) \
&& !defined PTRACE_GETFDPIC
#define PTRACE_GETFDPIC 31
@@ -85,7 +90,7 @@ struct buffer;
extern void linux_ptrace_attach_fail_reason (pid_t pid, struct buffer *buffer);
extern void linux_ptrace_init_warnings (void);
-extern void linux_enable_event_reporting (pid_t pid);
+extern void linux_enable_event_reporting (pid_t pid, int attached);
extern void linux_disable_event_reporting (pid_t pid);
extern int linux_supports_tracefork (void);
extern int linux_supports_traceclone (void);
--
1.9.1