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authorAnton Vorontsov <anton.vorontsov@linaro.org>2012-07-17 14:26:15 -0700
committerAnton Vorontsov <anton.vorontsov@linaro.org>2012-09-06 22:16:58 -0700
commit65f8c95e46a1827ae8bbc52a817ea308dd7d65ae (patch)
treeadc856e8b50441b055350d8f1d83e3f641c77456 /fs/pstore/ftrace.c
parentb4a871bce619dc5ca03cc6c78e1c467ceacb8e7e (diff)
pstore/ftrace: Convert to its own enable/disable debugfs knob
With this patch we no longer reuse function tracer infrastructure, now we register our own tracer back-end via a debugfs knob. It's a bit more code, but that is the only downside. On the bright side we have: - Ability to make persistent_ram module removable (when needed, we can move ftrace_ops struct into a module). Note that persistent_ram is still not removable for other reasons, but with this patch it's just one thing less to worry about; - Pstore part is more isolated from the generic function tracer. We tried it already by registering our own tracer in available_tracers, but that way we're loosing ability to see the traces while we record them to pstore. This solution is somewhere in the middle: we only register "internal ftracer" back-end, but not the "front-end"; - When there is only pstore tracing enabled, the kernel will only write to the pstore buffer, omitting function tracer buffer (which, of course, still can be enabled via 'echo function > current_tracer'). Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Diffstat (limited to 'fs/pstore/ftrace.c')
-rw-r--r--fs/pstore/ftrace.c96
1 files changed, 95 insertions, 1 deletions
diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
index a130d484b7d3..2d57e1ac0115 100644
--- a/fs/pstore/ftrace.c
+++ b/fs/pstore/ftrace.c
@@ -17,19 +17,113 @@
#include <linux/percpu.h>
#include <linux/smp.h>
#include <linux/atomic.h>
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/ftrace.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/err.h>
+#include <linux/cache.h>
#include <asm/barrier.h>
#include "internal.h"
-void notrace pstore_ftrace_call(unsigned long ip, unsigned long parent_ip)
+static void notrace pstore_ftrace_call(unsigned long ip,
+ unsigned long parent_ip)
{
+ unsigned long flags;
struct pstore_ftrace_record rec = {};
if (unlikely(oops_in_progress))
return;
+ local_irq_save(flags);
+
rec.ip = ip;
rec.parent_ip = parent_ip;
pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
sizeof(rec), psinfo);
+
+ local_irq_restore(flags);
+}
+
+static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
+ .func = pstore_ftrace_call,
+};
+
+static DEFINE_MUTEX(pstore_ftrace_lock);
+static bool pstore_ftrace_enabled;
+
+static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ u8 on;
+ ssize_t ret;
+
+ ret = kstrtou8_from_user(buf, count, 2, &on);
+ if (ret)
+ return ret;
+
+ mutex_lock(&pstore_ftrace_lock);
+
+ if (!on ^ pstore_ftrace_enabled)
+ goto out;
+
+ if (on)
+ ret = register_ftrace_function(&pstore_ftrace_ops);
+ else
+ ret = unregister_ftrace_function(&pstore_ftrace_ops);
+ if (ret) {
+ pr_err("%s: unable to %sregister ftrace ops: %zd\n",
+ __func__, on ? "" : "un", ret);
+ goto err;
+ }
+
+ pstore_ftrace_enabled = on;
+out:
+ ret = count;
+err:
+ mutex_unlock(&pstore_ftrace_lock);
+
+ return ret;
+}
+
+static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ char val[] = { '0' + pstore_ftrace_enabled, '\n' };
+
+ return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
+}
+
+static const struct file_operations pstore_knob_fops = {
+ .open = simple_open,
+ .read = pstore_ftrace_knob_read,
+ .write = pstore_ftrace_knob_write,
+};
+
+void pstore_register_ftrace(void)
+{
+ struct dentry *dir;
+ struct dentry *file;
+
+ if (!psinfo->write_buf)
+ return;
+
+ dir = debugfs_create_dir("pstore", NULL);
+ if (!dir) {
+ pr_err("%s: unable to create pstore directory\n", __func__);
+ return;
+ }
+
+ file = debugfs_create_file("record_ftrace", 0600, dir, NULL,
+ &pstore_knob_fops);
+ if (!file) {
+ pr_err("%s: unable to create record_ftrace file\n", __func__);
+ goto err_file;
+ }
+
+ return;
+err_file:
+ debugfs_remove(dir);
}