4 files changed, 168 insertions, 3 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 703eb53cfa2b..899ec4b26b6c 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -181,6 +181,8 @@ static inline void __ftrace_enabled_restore(int enabled)
 #endif
 
 #ifdef CONFIG_TRACING
+extern int ftrace_dump_on_oops;
+
 extern void
 ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 9d048fa2d902..6b6b727258b5 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -484,6 +484,16 @@ static struct ctl_table kern_table[] = {
                 .proc_handler   = &ftrace_enable_sysctl,
         },
 #endif
+#ifdef CONFIG_TRACING
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "ftrace_dump_on_opps",
+                .data           = &ftrace_dump_on_oops,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec,
+        },
+#endif
 #ifdef CONFIG_MODULES
         {
                 .ctl_name       = KERN_MODPROBE,
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a610ca771558..8741e5c4313b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -64,6 +64,28 @@ static cpumask_t __read_mostly		tracing_buffer_mask;
 
 static int tracing_disabled = 1;
 
+/*
+ * ftrace_dump_on_oops - variable to dump ftrace buffer on oops
+ *
+ * If there is an oops (or kernel panic) and the ftrace_dump_on_oops
+ * is set, then ftrace_dump is called. This will output the contents
+ * of the ftrace buffers to the console.  This is very useful for
+ * capturing traces that lead to crashes and outputing it to a
+ * serial console.
+ *
+ * It is default off, but you can enable it with either specifying
+ * "ftrace_dump_on_oops" in the kernel command line, or setting
+ * /proc/sys/kernel/ftrace_dump_on_oops to true.
+ */
+int ftrace_dump_on_oops;
+
+static int __init set_ftrace_dump_on_oops(char *str)
+{
+        ftrace_dump_on_oops = 1;
+        return 1;
+}
+__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);
+
 long
 ns2usecs(cycle_t nsec)
 {
@@ -3020,7 +3042,8 @@ EXPORT_SYMBOL_GPL(__ftrace_printk);
 static int trace_panic_handler(struct notifier_block *this,
                                unsigned long event, void *unused)
 {
-        ftrace_dump();
+        if (ftrace_dump_on_oops)
+                ftrace_dump();
         return NOTIFY_OK;
 }
 
@@ -3036,7 +3059,8 @@ static int trace_die_handler(struct notifier_block *self,
 {
         switch (val) {
         case DIE_OOPS:
-                ftrace_dump();
+                if (ftrace_dump_on_oops)
+                        ftrace_dump();
                 break;
         default:
                 break;
@@ -3077,7 +3101,6 @@ trace_printk_seq(struct trace_seq *s)
         trace_seq_reset(s);
 }
 
-
 void ftrace_dump(void)
 {
         static DEFINE_SPINLOCK(ftrace_dump_lock);
diff --git a/scripts/tracing/draw_functrace.py b/scripts/tracing/draw_functrace.py
new file mode 100644
index 000000000000..902f9a992620
--- /dev/null
+++ b/scripts/tracing/draw_functrace.py
@@ -0,0 +1,130 @@
+#!/usr/bin/python
+
+"""
+Copyright 2008 (c) Frederic Weisbecker <fweisbec@gmail.com>
+Licensed under the terms of the GNU GPL License version 2
+
+This script parses a trace provided by the function tracer in
+kernel/trace/trace_functions.c
+The resulted trace is processed into a tree to produce a more human
+view of the call stack by drawing textual but hierarchical tree of
+calls. Only the functions's names and the the call time are provided.
+
+Usage:
+        Be sure that you have CONFIG_FUNCTION_TRACER
+        # mkdir /debugfs
+        # mount -t debug debug /debug
+        # echo function > /debug/tracing/current_tracer
+        $ cat /debug/tracing/trace_pipe > ~/raw_trace_func
+        Wait some times but not too much, the script is a bit slow.
+        Break the pipe (Ctrl + Z)
+        $ scripts/draw_functrace.py < raw_trace_func > draw_functrace
+        Then you have your drawn trace in draw_functrace
+"""
+
+
+import sys, re
+
+class CallTree:
+        """ This class provides a tree representation of the functions
+                call stack. If a function has no parent in the kernel (interrupt,
+                syscall, kernel thread...) then it is attached to a virtual parent
+                called ROOT.
+        """
+        ROOT = None
+
+        def __init__(self, func, time = None, parent = None):
+                self._func = func
+                self._time = time
+                if parent is None:
+                        self._parent = CallTree.ROOT
+                else:
+                        self._parent = parent
+                self._children = []
+
+        def calls(self, func, calltime):
+                """ If a function calls another one, call this method to insert it
+                        into the tree at the appropriate place.
+                        @return: A reference to the newly created child node.
+                """
+                child = CallTree(func, calltime, self)
+                self._children.append(child)
+                return child
+
+        def getParent(self, func):
+                """ Retrieve the last parent of the current node that
+                        has the name given by func. If this function is not
+                        on a parent, then create it as new child of root
+                        @return: A reference to the parent.
+                """
+                tree = self
+                while tree != CallTree.ROOT and tree._func != func:
+                        tree = tree._parent
+                if tree == CallTree.ROOT:
+                        child = CallTree.ROOT.calls(func, None)
+                        return child
+                return tree
+
+        def __repr__(self):
+                return self.__toString("", True)
+
+        def __toString(self, branch, lastChild):
+                if self._time is not None:
+                        s = "%s----%s (%s)\n" % (branch, self._func, self._time)
+                else:
+                        s = "%s----%s\n" % (branch, self._func)
+
+                i = 0
+                if lastChild:
+                        branch = branch[:-1] + " "
+                while i < len(self._children):
+                        if i != len(self._children) - 1:
+                                s += "%s" % self._children[i].__toString(branch +\
+                                                                "    |", False)
+                        else:
+                                s += "%s" % self._children[i].__toString(branch +\
+                                                                "    |", True)
+                        i += 1
+                return s
+
+class BrokenLineException(Exception):
+        """If the last line is not complete because of the pipe breakage,
+           we want to stop the processing and ignore this line.
+        """
+        pass
+
+class CommentLineException(Exception):
+        """ If the line is a comment (as in the beginning of the trace file),
+            just ignore it.
+        """
+        pass
+
+
+def parseLine(line):
+        line = line.strip()
+        if line.startswith("#"):
+                raise CommentLineException
+        m = re.match("[^]]+?\\] +([0-9.]+): (\\w+) <-(\\w+)", line)
+        if m is None:
+                raise BrokenLineException
+        return (m.group(1), m.group(2), m.group(3))
+
+
+def main():
+        CallTree.ROOT = CallTree("Root (Nowhere)", None, None)
+        tree = CallTree.ROOT
+
+        for line in sys.stdin:
+                try:
+                        calltime, callee, caller = parseLine(line)
+                except BrokenLineException:
+                        break
+                except CommentLineException:
+                        continue
+                tree = tree.getParent(caller)
+                tree = tree.calls(callee, calltime)
+
+        print CallTree.ROOT
+
+if __name__ == "__main__":
+        main()