tracing: Have stack tracing set filtered functions at boot
Add stacktrace_filter= to the kernel command line that lets
the user pick specific functions to check the stack on.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index fd5c913..fde2ae0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2435,6 +2435,14 @@
stacktrace [FTRACE]
Enabled the stack tracer on boot up.
+ stacktrace_filter=[function-list]
+ [FTRACE] Limit the functions that the stack tracer
+ will trace at boot up. function-list is a comma separated
+ list of functions. This list can be changed at run
+ time by the stack_trace_filter file in the debugfs
+ tracing directory. Note, this enables stack tracing
+ and the stacktrace above is not needed.
+
sti= [PARISC,HW]
Format: <num>
Set the STI (builtin display/keyboard on the HP-PARISC
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 0398b7c..d4545f4 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -13,6 +13,9 @@
#include <linux/sysctl.h>
#include <linux/init.h>
#include <linux/fs.h>
+
+#include <asm/setup.h>
+
#include "trace.h"
#define STACK_TRACE_ENTRIES 500
@@ -352,8 +355,13 @@
return ret;
}
+static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
+
static __init int enable_stacktrace(char *str)
{
+ if (strncmp(str, "_filter=", 8) == 0)
+ strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
+
stack_tracer_enabled = 1;
last_stack_tracer_enabled = 1;
return 1;
@@ -375,6 +383,9 @@
trace_create_file("stack_trace_filter", 0444, d_tracer,
NULL, &stack_trace_filter_fops);
+ if (stack_trace_filter_buf[0])
+ ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
+
if (stack_tracer_enabled)
register_ftrace_function(&trace_ops);