[RFC PATCH 07/22 -v2] tracer add debugfs interface

Steven Rostedt
2008-01-09T23:37:12Z

[-- Attachment #1: mcount-tracer-debugfs.patch --]
[-- Type: text/plain, Size: 3672 bytes --]

This patch adds an interface into debugfs.

/debugfs/tracing/ctrl

echoing 1 into the ctrl file turns on the tracer,
and echoing 0 turns it off.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
lib/tracing/tracer.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++-
lib/tracing/tracer.h | 1
2 files changed, 87 insertions(+), 1 deletion(-)

Index: linux-compile-i386.git/lib/tracing/tracer.c
===================================================================
--- linux-compile-i386.git.orig/lib/tracing/tracer.c 2008-01-09 14:10:46.000000000 -0500
+++ linux-compile-i386.git/lib/tracing/tracer.c 2008-01-09 15:17:43.000000000 -0500
@@ -15,6 +15,8 @@
#include <linux/init.h>
#include <linux/linkage.h>
#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/uaccess.h>
#include <linux/mcount.h>

#include "tracer.h"
@@ -71,6 +73,89 @@ static notrace void trace_function(const
raw_local_irq_restore(flags);
}

+#ifdef CONFIG_DEBUG_FS
+static int mctracer_open_generic(struct inode *inode, struct file *filp)
+{
+ filp->private_data = inode->i_private;
+ return 0;
+}
+
+
+static ssize_t mctracer_ctrl_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct mctracer_trace *tr = filp->private_data;
+ char buf[16];
+ int r;
+
+ r = sprintf(buf, "%ld\n", tr->ctrl);
+ return simple_read_from_buffer(ubuf, cnt, ppos,
+ buf, r);
+}
+
+static ssize_t mctracer_ctrl_write(struct file *filp,
+ const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct mctracer_trace *tr = filp->private_data;
+ long val;
+ char buf[16];
+
+ if (cnt > 15)
+ cnt = 15;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+
+ buf[cnt] = 0;
+
+ val = !!simple_strtoul(buf, NULL, 10);
+
+ if (tr->ctrl ^ val) {
+ if (val)
+ register_mcount_function(trace_function);
+ else
+ clear_mcount_function();
+ tr->ctrl = val;
+ }
+
+ filp->f_pos += cnt;
+
+ return cnt;
+}
+
+static struct file_operations mctracer_ctrl_fops = {
+ .open = mctracer_open_generic,
+ .read = mctracer_ctrl_read,
+ .write = mctracer_ctrl_write,
+};
+
+static void mctrace_init_debugfs(void)
+{
+ struct dentry *d_mctracer;
+ struct dentry *entry;
+
+ d_mctracer = debugfs_create_dir("tracing", NULL);
+ if (!d_mctracer) {
+ pr_warning("Could not create debugfs directory mctracer\n");
+ return;
+ }
+
+ entry = debugfs_create_file("ctrl", 0644, d_mctracer,
+ &mctracer_trace, &mctracer_ctrl_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs 'ctrl' entry\n");
+}
+#else /* CONFIG_DEBUG_FS */
+static void mctrace_init_debugfs(void)
+{
+ /*
+ * No way to turn on or off the trace function
+ * without debugfs, so we just turn it on.
+ */
+ register_mcount_function(trace_function);
+}
+#endif /* CONFIG_DEBUG_FS */

static notrace int page_order(const unsigned long size)
{
@@ -106,7 +191,7 @@ static notrace int mctracer_alloc_buffer
size, MCTRACER_NR_ENTRIES, MCTRACER_ENTRY_SIZE);
pr_info(" actual entries %ld\n", mctracer_trace.entries);

- register_mcount_function(trace_function);
+ mctrace_init_debugfs();

return 0;

Index: linux-compile-i386.git/lib/tracing/tracer.h
===================================================================
--- linux-compile-i386.git.orig/lib/tracing/tracer.h 2008-01-09 14:10:46.000000000 -0500
+++ linux-compile-i386.git/lib/tracing/tracer.h 2008-01-09 15:17:41.000000000 -0500
@@ -13,6 +13,7 @@ struct mctracer_trace {
void *trace[NR_CPUS];
unsigned long trace_idx[NR_CPUS];
unsigned long entries;
+ long ctrl;
atomic_t cnt;
atomic_t disabled[NR_CPUS];
atomic_t underrun[NR_CPUS];

--