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authorRoland McGrath <roland@redhat.com>2008-07-25 19:45:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-26 12:00:09 -0700
commit7bcf6a2ca5f639b038c48711ebe6c4eca2036641 (patch)
tree4219a0725d581310f729d4616361febd700f0574
parent283d7559e7712f95a05331eb0a85394c6368101b (diff)
tracehook: get_signal_to_deliver
This defines the tracehook_get_signal() hook to allow tracing code to slip in before normal signal dequeuing. This lays the groundwork for new tracing features that can inject synthetic signals outside the normal queue or control the disposition of delivered signals. The calling convention lets tracehook_get_signal() decide both exactly what will happen and what signal number to report in the handler/exit. Signed-off-by: Roland McGrath <roland@redhat.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Reviewed-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/tracehook.h29
-rw-r--r--kernel/signal.c38
2 files changed, 56 insertions, 11 deletions
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 3548694a24db..42a0d7b11959 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -422,4 +422,33 @@ static inline int tracehook_consider_fatal_signal(struct task_struct *task,
return (task_ptrace(task) & PT_PTRACED) != 0;
}
+/**
+ * tracehook_get_signal - deliver synthetic signal to traced task
+ * @task: @current
+ * @regs: task_pt_regs(@current)
+ * @info: details of synthetic signal
+ * @return_ka: sigaction for synthetic signal
+ *
+ * Return zero to check for a real pending signal normally.
+ * Return -1 after releasing the siglock to repeat the check.
+ * Return a signal number to induce an artifical signal delivery,
+ * setting *@info and *@return_ka to specify its details and behavior.
+ *
+ * The @return_ka->sa_handler value controls the disposition of the
+ * signal, no matter the signal number. For %SIG_DFL, the return value
+ * is a representative signal to indicate the behavior (e.g. %SIGTERM
+ * for death, %SIGQUIT for core dump, %SIGSTOP for job control stop,
+ * %SIGTSTP for stop unless in an orphaned pgrp), but the signal number
+ * reported will be @info->si_signo instead.
+ *
+ * Called with @task->sighand->siglock held, before dequeuing pending signals.
+ */
+static inline int tracehook_get_signal(struct task_struct *task,
+ struct pt_regs *regs,
+ siginfo_t *info,
+ struct k_sigaction *return_ka)
+{
+ return 0;
+}
+
#endif /* <linux/tracehook.h> */
diff --git a/kernel/signal.c b/kernel/signal.c
index 1a942ce32ba0..10b31ecdd9c8 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1754,17 +1754,33 @@ relock:
do_signal_stop(0))
goto relock;
- signr = dequeue_signal(current, &current->blocked, info);
- if (!signr)
- break; /* will return 0 */
+ /*
+ * Tracing can induce an artifical signal and choose sigaction.
+ * The return value in @signr determines the default action,
+ * but @info->si_signo is the signal number we will report.
+ */
+ signr = tracehook_get_signal(current, regs, info, return_ka);
+ if (unlikely(signr < 0))
+ goto relock;
+ if (unlikely(signr != 0))
+ ka = return_ka;
+ else {
+ signr = dequeue_signal(current, &current->blocked,
+ info);
- if (signr != SIGKILL) {
- signr = ptrace_signal(signr, info, regs, cookie);
if (!signr)
- continue;
+ break; /* will return 0 */
+
+ if (signr != SIGKILL) {
+ signr = ptrace_signal(signr, info,
+ regs, cookie);
+ if (!signr)
+ continue;
+ }
+
+ ka = &sighand->action[signr-1];
}
- ka = &sighand->action[signr-1];
if (ka->sa.sa_handler == SIG_IGN) /* Do nothing. */
continue;
if (ka->sa.sa_handler != SIG_DFL) {
@@ -1812,7 +1828,7 @@ relock:
spin_lock_irq(&sighand->siglock);
}
- if (likely(do_signal_stop(signr))) {
+ if (likely(do_signal_stop(info->si_signo))) {
/* It released the siglock. */
goto relock;
}
@@ -1833,7 +1849,7 @@ relock:
if (sig_kernel_coredump(signr)) {
if (print_fatal_signals)
- print_fatal_signal(regs, signr);
+ print_fatal_signal(regs, info->si_signo);
/*
* If it was able to dump core, this kills all
* other threads in the group and synchronizes with
@@ -1842,13 +1858,13 @@ relock:
* first and our do_group_exit call below will use
* that value and ignore the one we pass it.
*/
- do_coredump((long)signr, signr, regs);
+ do_coredump(info->si_signo, info->si_signo, regs);
}
/*
* Death signals, no core dump.
*/
- do_group_exit(signr);
+ do_group_exit(info->si_signo);
/* NOTREACHED */
}
spin_unlock_irq(&sighand->siglock);