[PATCH] Add panic tapset

["Bryn M. Reeves" <bmr at redhat dot com>]

Hi Folks,

This patch adds a tapset with a single function to call the native
panic() routine. This is useful in order to trigger a core dump to
collect post-mortem debugging data when some condition occurs.

I've used this sort of trick several times (e.g. the PanicOnOom war
story in the systemtap wiki) and find it a very handy tool.

E.g.:

stap -g -e 'probe end { panic("whoops!") }'

Regards,
Bryn.

>From 16f8bd43fddeec7bec370562b68d3baac256282c Mon Sep 17 00:00:00 2001
From: "Bryn M. Reeves" <bmr@redhat.com>
Date: Mon, 18 Jun 2012 18:09:47 +0100
Subject: [PATCH] Add panic tapset

Add a tapset to expose the kernel's panic() routine.
---
 tapset/panic.stp |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)
 create mode 100644 tapset/panic.stp

diff --git a/tapset/panic.stp b/tapset/panic.stp
new file mode 100644
index 0000000..48ea2c9
--- /dev/null
+++ b/tapset/panic.stp
@@ -0,0 +1,32 @@
+// Copyright (C) 2012 Red Hat Inc., Bryn M. Reeves <bmr@redhat.com>
+//
+// This file is part of systemtap, and is free software.  You can
+// redistribute it and/or modify it under the terms of the GNU General
+// Public License (GPL); either version 2, or (at your option) any
+// later version.
+//
+
+// <tapsetdescription>
+// Functions in the panic tapset allow a probe handler to invoke
+// the system panic routine with a user-specified message.
+//
+// This may be used with a crash dump collection facility such as 
+// kexec/kdump in order to capture data for post-mortem debugging.
+//
+// Due to the fact that this will bring the system to an immediate
+// halt the functions in this tapset require guru mode.
+// </tapsetdescription>
+
+/**
+ * sfunction panic - trigger a panic
+ * @msg: message to pass to kernel's panic() function
+ *
+ * Description: this function triggers an immediate panic of the running
+ * kernel with a user-specified panic message.
+ * It requires guru mode.
+ */
+function panic(msg:string) %{
+        /* guru */
+        panic("%s", THIS->msg);
+%}
+
-- 
1.7.6.5