From a5d05b07961a2df47d3b4aae3bdae61ac095a43c Mon Sep 17 00:00:00 2001 From: Uwe Kleine-König Date: Thu, 10 Jun 2021 10:21:34 +0200 Subject: pstore/ftrace: Allow immediate recording MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Without a module param knob there was no way to enable pstore ftrace recording early enough to debug hangs happening during the boot process before userspace is up enough to enable it via the regular debugfs knobs. Signed-off-by: Uwe Kleine-König Co-developed-by: Kees Cook Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20210610082134.20636-1-u.kleine-koenig@pengutronix.de --- fs/pstore/ftrace.c | 46 ++++++++++++++++++++++++++++++---------------- 1 file changed, 30 insertions(+), 16 deletions(-) (limited to 'fs/pstore') diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c index 5939595f0115..776cae20af4e 100644 --- a/fs/pstore/ftrace.c +++ b/fs/pstore/ftrace.c @@ -64,20 +64,12 @@ static struct ftrace_ops pstore_ftrace_ops __read_mostly = { 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) +static int pstore_set_ftrace_enabled(bool on) { - 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 == pstore_ftrace_enabled) + return 0; if (on) { ftrace_ops_set_global_filter(&pstore_ftrace_ops); @@ -89,15 +81,30 @@ static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf, if (ret) { pr_err("%s: unable to %sregister ftrace ops: %zd\n", __func__, on ? "" : "un", ret); - goto err; + } else { + pstore_ftrace_enabled = on; } - pstore_ftrace_enabled = on; -out: - ret = count; -err: + return ret; +} + +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); + ret = pstore_set_ftrace_enabled(on); mutex_unlock(&pstore_ftrace_lock); + if (ret == 0) + ret = count; + return ret; } @@ -117,6 +124,11 @@ static const struct file_operations pstore_knob_fops = { static struct dentry *pstore_ftrace_dir; +static bool record_ftrace; +module_param(record_ftrace, bool, 0400); +MODULE_PARM_DESC(record_ftrace, + "enable ftrace recording immediately (default: off)"); + void pstore_register_ftrace(void) { if (!psinfo->write) @@ -124,6 +136,8 @@ void pstore_register_ftrace(void) pstore_ftrace_dir = debugfs_create_dir("pstore", NULL); + pstore_set_ftrace_enabled(record_ftrace); + debugfs_create_file("record_ftrace", 0600, pstore_ftrace_dir, NULL, &pstore_knob_fops); } -- cgit v1.2.3-70-g09d2