From: Masami Hiramatsu <mhiramat@redhat.com>
Date: Wed, 9 Dec 2009 19:56:20 -0500
Subject: [trace] add signal tracepoints
Message-id: <4B2000E4.8090903@redhat.com>
Patchwork-id: 21830
O-Subject: [PATCH RHEL5.5][REPOST] tracepoint: add signal tracepoints
Bugzilla: 517121
RH-Acked-by: Dave Anderson <anderson@redhat.com>

Hi,

This patch is related to BZ#517121, add signal tracepoints.

BZ:
   Bug 517121 -  Tracepoint for signal delivery event

Description:
This patch adds new tracepoints for signal events including
signal generation, delivery, lost. These tracepoints help us
to find out who terminated a process, when and why a signal was
lost, and whether a signal is delivered.

I've ported below 3 patches to rhel5 kernel and folded it
into 1 patch. Major differences from upstream are:
- Use DEFINE_TRACE instead of TRACE_EVENT.
- Remove 'group' parameter from signal loss events because there
   is no group flag in rhel5 kernel.
- Signal generate event is put at the beginning of specific_send_sig_info
   and __group_send_sig_info.

Upstream status:
Backported from latest Ingo's -tip tree. Commits are below.
   d1eb650ff4130972fa21462fa49cd35a2865403b
   f9d4257e01d266e67420cc99d456b6d4c8464f54
   ba005e1f417295d28cd1563ab82bc33af07fb16a

Test status:
Successfully tested.

Brew status:
https://brewweb.devel.redhat.com/taskinfo?taskID=2113573

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
This patch is related to BZ#517121, add signal tracepoints.

BZ:
   Bug 517121 -  Tracepoint for signal delivery event

Description:
This patch adds new tracepoints for signal events including
signal generation, delivery, lost. These tracepoints help us
to find out who terminated a process, when and why a signal was
lost, and whether a signal is delivered.

I've ported below 3 patches to rhel5 kernel and folded it
into 1 patch. Major differences from upstream are:
- Use DEFINE_TRACE instead of TRACE_EVENT.
- Remove 'group' parameter from signal loss events because there
   is no group flag in rhel5 kernel.
- Signal generate event is put at the beginning of specific_send_sig_info
   and __group_send_sig_info.

Upstream status:
Backported from latest Ingo's -tip tree. Commits are below.
   d1eb650ff4130972fa21462fa49cd35a2865403b
   f9d4257e01d266e67420cc99d456b6d4c8464f54
   ba005e1f417295d28cd1563ab82bc33af07fb16a

Test status:
Successfully tested.

Brew status:
https://brewweb.devel.redhat.com/taskinfo?taskID=2113573

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>

diff --git a/include/trace/signal.h b/include/trace/signal.h
new file mode 100644
index 0000000..adc8bb1
--- /dev/null
+++ b/include/trace/signal.h
@@ -0,0 +1,71 @@
+#ifndef _TRACE_SIGNAL_H
+#define _TRACE_SIGNAL_H
+
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/tracepoint.h>
+
+/**
+ * signal_generate - called when a signal is generated
+ * @sig: signal number
+ * @info: pointer to struct siginfo
+ * @task: pointer to struct task_struct
+ *
+ * Current process sends a 'sig' signal to 'task' process with
+ * 'info' siginfo. If 'info' is SEND_SIG_NOINFO or SEND_SIG_PRIV,
+ * 'info' is not a pointer and you can't access its field. Instead,
+ * SEND_SIG_NOINFO means that si_code is SI_USER, and SEND_SIG_PRIV
+ * means that si_code is SI_KERNEL.
+ */
+DEFINE_TRACE(signal_generate,
+	TPPROTO(int sig, struct siginfo *info, struct task_struct *task),
+	TPARGS(sig, info, task)
+);
+
+/**
+ * signal_deliver - called when a signal is delivered
+ * @sig: signal number
+ * @info: pointer to struct siginfo
+ * @ka: pointer to struct k_sigaction
+ *
+ * A 'sig' signal is delivered to current process with 'info' siginfo,
+ * and it will be handled by 'ka'. ka->sa.sa_handler can be SIG_IGN or
+ * SIG_DFL.
+ * Note that some signals reported by signal_generate tracepoint can be
+ * lost, ignored or modified (by debugger) before hitting this tracepoint.
+ * This means, this can show which signals are actually delivered, but
+ * matching generated signals and delivered signals may not be correct.
+ */
+DEFINE_TRACE(signal_deliver,
+	TPPROTO(int sig, struct siginfo *info, struct k_sigaction *ka),
+	TPARGS(sig, info, ka)
+);
+
+/**
+ * signal_overflow_fail - called when signal queue is overflow
+ * @sig: signal number
+ * @info: pointer to struct siginfo
+ *
+ * Kernel fails to generate 'sig' signal with 'info' siginfo, because
+ * siginfo queue is overflow, and the signal is dropped.
+ * 'sig' is always one of RT signals.
+ */
+DEFINE_TRACE(signal_overflow_fail,
+	TPPROTO(int sig, struct siginfo *info),
+	TPARGS(sig, info)
+);
+
+/**
+ * signal_lose_info - called when siginfo is lost
+ * @sig: signal number
+ * @info: pointer to struct siginfo
+ *
+ * Kernel generates 'sig' signal but loses 'info' siginfo, because siginfo
+ * queue is overflow.
+ * 'sig' is always one of non-RT signals.
+ */
+DEFINE_TRACE(signal_lose_info,
+	TPPROTO(int sig, struct siginfo *info),
+	TPARGS(sig, info)
+);
+#endif /* _TRACE_SIGNAL_H */
diff --git a/kernel/signal.c b/kernel/signal.c
index da9b46f..2b5e7ac 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -28,6 +28,7 @@
 #include <asm/unistd.h>
 #include <asm/siginfo.h>
 #include "audit.h"	/* audit_signal_info() */
+#include <trace/signal.h>
 
 /*
  * SLAB caches for signal bits.
@@ -652,12 +653,21 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
 			break;
 		}
 	} else if (!is_si_special(info)) {
-		if (sig >= SIGRTMIN && info->si_code != SI_USER)
-		/*
-		 * Queue overflow, abort.  We may abort if the signal was rt
-		 * and sent by user using something other than kill().
-		 */
+		if (sig >= SIGRTMIN && info->si_code != SI_USER) {
+			/*
+			 * Queue overflow, abort.  We may abort if the
+			 * signal was rt and sent by user using something
+			 * other than kill().
+			 */
+			trace_signal_overflow_fail(sig, info);
 			return -EAGAIN;
+		} else {
+			/*
+			 * This is a silent loss of information.  We still
+			 * send the signal, but the *info bits are lost.
+			 */
+			trace_signal_lose_info(sig, info);
+		}
 	}
 
 out_set:
@@ -705,6 +715,8 @@ specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t)
 {
 	int ret = 0;
 
+	trace_signal_generate(sig, info, t);
+
 	BUG_ON(!irqs_disabled());
 	assert_spin_locked(&t->sighand->siglock);
 
@@ -893,6 +905,8 @@ __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 {
 	int ret = 0;
 
+	trace_signal_generate(sig, info, p);
+
 	assert_spin_locked(&p->sighand->siglock);
 	handle_stop_signal(sig, p);
 
@@ -1638,6 +1652,9 @@ relock:
 			ka = &current->sighand->action[signr-1];
 		}
 
+		/* Trace actually delivered signals. */
+		trace_signal_deliver(signr, info, ka);
+
 		if (ka->sa.sa_handler == SIG_IGN) /* Do nothing.  */
 			continue;
 		if (ka->sa.sa_handler != SIG_DFL) {