[PATCH 12/23] tracehook: tracehook_consider_fatal_signal

Roland McGrath
2008-07-17T07:32:28Z

This defines tracehook_consider_fatal_signal() has a fine-grained
hook for deciding to skip the special cases for a fatal signal,
as ptrace does. There is no change, only cleanup.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
include/linux/tracehook.h | 21 +++++++++++++++++++++
kernel/signal.c | 9 +++++----
2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 8cffd34..8b4c15e 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -331,4 +331,25 @@ static inline int tracehook_consider_ignored_signal(struct task_struct *task,
return (task_ptrace(task) & PT_PTRACED) != 0;
}

+/**
+ * tracehook_consider_fatal_signal - suppress special handling of fatal signal
+ * @task: task receiving the signal
+ * @sig: signal number being sent
+ * @handler: %SIG_DFL or %SIG_IGN
+ *
+ * Return nonzero to prevent special handling of this termination signal.
+ * Normally @handler is %SIG_DFL. It can be %SIG_IGN if @sig is ignored,
+ * in which case force_sig() is about to reset it to %SIG_DFL.
+ * When this returns zero, this signal might cause a quick termination
+ * that does not give the debugger a chance to intercept the signal.
+ *
+ * Called with or without @task->sighand->siglock held.
+ */
+static inline int tracehook_consider_fatal_signal(struct task_struct *task,
+ int sig,
+ void __user *handler)
+{
+ return (task_ptrace(task) & PT_PTRACED) != 0;
+}
+
#endif /* <linux/tracehook.h> */
diff --git a/kernel/signal.c b/kernel/signal.c
index f68fb01..860afb8 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -300,12 +300,12 @@ flush_signal_handlers(struct task_struct *t, int force_default)

int unhandled_signal(struct task_struct *tsk, int sig)
{
+ void __user *handler = tsk->sighand->action[sig-1].sa.sa_handler;
if (is_global_init(tsk))
return 1;
- if (tsk->ptrace & PT_PTRACED)
+ if (handler != SIG_IGN && handler != SIG_DFL)
return 0;
- return (tsk->sighand->action[sig-1].sa.sa_handler == SIG_IGN) ||
- (tsk->sighand->action[sig-1].sa.sa_handler == SIG_DFL);
+ return !tracehook_consider_fatal_signal(tsk, sig, handler);
}

@@ -770,7 +770,8 @@ static void complete_signal(int sig, struct task_struct *p, int group)
if (sig_fatal(p, sig) &&
!(signal->flags & (SIGNAL_UNKILLABLE | SIGNAL_GROUP_EXIT)) &&
!sigismember(&t->real_blocked, sig) &&
- (sig == SIGKILL || !(t->ptrace & PT_PTRACED))) {
+ (sig == SIGKILL ||
+ !tracehook_consider_fatal_signal(t, sig, SIG_DFL))) {
/*
* This signal will be fatal to the whole group.
*/