linux-kernel - [PATCH] pstore/ftrace: add a kernel parameter to start pstore recording

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Date:   Thu, 10 Jun 2021 10:21:34 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Kees Cook <keescook@...omium.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: [PATCH] pstore/ftrace: add a kernel parameter to start pstore recording

With this knob you can enable pstore recording early enough to debug
hangs happening during the boot process before userspace is up enough to
enable it via sysfs.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
 fs/pstore/ftrace.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
index 5939595f0115..92d35ee83c95 100644
--- a/fs/pstore/ftrace.c
+++ b/fs/pstore/ftrace.c
@@ -117,13 +117,26 @@ static const struct file_operations pstore_knob_fops = {
 
 static struct dentry *pstore_ftrace_dir;
 
+static unsigned int record_ftrace_init;
+module_param(record_ftrace_init, uint, 0400);
+
 void pstore_register_ftrace(void)
 {
+	int ret;
+
 	if (!psinfo->write)
 		return;
 
 	pstore_ftrace_dir = debugfs_create_dir("pstore", NULL);
 
+	if (record_ftrace_init) {
+		ret = register_ftrace_function(&pstore_ftrace_ops);
+		if (ret)
+			return;
+
+		pstore_ftrace_enabled = 1;
+	}
+
 	debugfs_create_file("record_ftrace", 0600, pstore_ftrace_dir, NULL,
 			    &pstore_knob_fops);
 }
-- 
2.29.2