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[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 forward
        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.
This commit is contained in:
Joel Brobecker 2014-11-11 10:07:21 +04:00
parent bf330350c2
commit beed38b827
6 changed files with 69 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
gdb/ChangeLog
View File

@ -1,3 +1,19 @@
2014-12-16 Joel Brobecker <brobecker@adacore.com>
* 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 forward
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.
2014-12-16 Yao Qi <yao@codesourcery.com>
* NEWS: Move some entries to "Changes since GDB 7.8" section.

6
gdb/gdbserver/ChangeLog
View File

@ -1,3 +1,9 @@
2014-12-16 Joel Brobecker <brobecker@adacore.com>
* linux-low.c (linux_low_filter_event): Update call to
linux_enable_event_reporting following the addition of
a new parameter to that function.
2014-12-16 Catalin Udma <catalin.udma@freescale.com>
PR server/17457

4
gdb/gdbserver/linux-low.c
View File

@ -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;
}

12
gdb/linux-nat.c
View File

@ -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. */

34
gdb/nat/linux-ptrace.c
View File

@ -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. */

7
gdb/nat/linux-ptrace.h
View File

@ -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);