The existing clear_warn_once variable is write-only; used as per the
documentation to reset the warn_once to as-booted state with:
echo 1 > /sys/kernel/debug/clear_warn_once
The objective is to expand on that functionality, which requires the
debugfs variable to be read/write and not just write-only.
Here, we deal with the debugfs boilerplate associated with converting
it from write-only to read-write, in order to factor that out for easier
review, and for what may be a possible future useful bisect point.
Existing functionality is unchanged - the only difference is that we
have tied in a variable that lets you now read the variable and see
the last value written.
Link:
https://lore.kernel.org/r/[email protected]
Signed-off-by: Paul Gortmaker <[email protected]>
---
kernel/panic.c | 25 ++++++++++++++++++++-----
1 file changed, 20 insertions(+), 5 deletions(-)
diff --git a/kernel/panic.c b/kernel/panic.c
index f470a038b05b..53088219d7df 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -635,21 +635,36 @@ EXPORT_SYMBOL(__warn_printk);
/* Support resetting WARN*_ONCE state */
-static int clear_warn_once_set(void *data, u64 val)
+static u64 clear_warn_once;
+
+static void do_clear_warn_once(void)
{
generic_bug_clear_once();
memset(__start_once, 0, __end_once - __start_once);
+}
+
+static int warn_once_get(void *data, u64 *val)
+{
+ *val = clear_warn_once;
+ return 0;
+}
+
+static int warn_once_set(void *data, u64 val)
+{
+ clear_warn_once = val;
+
+ do_clear_warn_once();
return 0;
}
-DEFINE_DEBUGFS_ATTRIBUTE(clear_warn_once_fops, NULL, clear_warn_once_set,
- "%lld\n");
+DEFINE_DEBUGFS_ATTRIBUTE(clear_warn_once_fops, warn_once_get, warn_once_set,
+ "%llu\n");
static __init int register_warn_debugfs(void)
{
/* Don't care about failure */
- debugfs_create_file_unsafe("clear_warn_once", 0200, NULL, NULL,
- &clear_warn_once_fops);
+ debugfs_create_file_unsafe("clear_warn_once", 0600, NULL,
+ &clear_warn_once, &clear_warn_once_fops);
return 0;
}
--
2.17.1
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