[PATCH 4.14 14/16] panic: Expose "warn_count" to sysfs

Eric Biggers
2023-02-02T05:46:23Z

From: Kees Cook <keescook@chromium.org>

commit 8b05aa26336113c4cea25f1c333ee8cd4fc212a6 upstream.

Since Warn count is now tracked and is a fairly interesting signal, add
the entry /sys/kernel/warn_count to expose it to userspace.

Cc: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: tangmeng <tangmeng@uniontech.com>
Cc: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221117234328.594699-6-keescook@chromium.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
.../ABI/testing/sysfs-kernel-warn_count | 6 +++++
kernel/panic.c | 22 +++++++++++++++++--
2 files changed, 26 insertions(+), 2 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-warn_count

diff --git a/Documentation/ABI/testing/sysfs-kernel-warn_count b/Documentation/ABI/testing/sysfs-kernel-warn_count
new file mode 100644
index 0000000000000..08f083d2fd51b
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-warn_count
@@ -0,0 +1,6 @@
+What: /sys/kernel/oops_count
+Date: November 2022
+KernelVersion: 6.2.0
+Contact: Linux Kernel Hardening List <linux-hardening@vger.kernel.org>
+Description:
+ Shows how many times the system has Warned since last boot.
diff --git a/kernel/panic.c b/kernel/panic.c
index bfe6e4c5cd0e7..8f7bf0a8cef1a 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -28,6 +28,7 @@
#include <linux/console.h>
#include <linux/bug.h>
#include <linux/ratelimit.h>
+#include <linux/sysfs.h>

#define PANIC_TIMER_STEP 100
#define PANIC_BLINK_SPD 18
@@ -68,6 +69,25 @@ static __init int kernel_panic_sysctls_init(void)
late_initcall(kernel_panic_sysctls_init);
#endif

+static atomic_t warn_count = ATOMIC_INIT(0);
+
+#ifdef CONFIG_SYSFS
+static ssize_t warn_count_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *page)
+{
+ return sysfs_emit(page, "%d\n", atomic_read(&warn_count));
+}
+
+static struct kobj_attribute warn_count_attr = __ATTR_RO(warn_count);
+
+static __init int kernel_panic_sysfs_init(void)
+{
+ sysfs_add_file_to_group(kernel_kobj, &warn_count_attr.attr, NULL);
+ return 0;
+}
+late_initcall(kernel_panic_sysfs_init);
+#endif
+
static long no_blink(int state)
{
return 0;
@@ -145,8 +165,6 @@ EXPORT_SYMBOL(nmi_panic);

void check_panic_on_warn(const char *origin)
{
- static atomic_t warn_count = ATOMIC_INIT(0);
-
if (panic_on_warn)
panic("%s: panic_on_warn set ...\n", origin);

--
2.39.1