[PATCH printk v5 04/30] printk: Check printk_deferred_enter()/_exit() usage

John Ogness
2024-05-02T21:38:46Z

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Add validation that printk_deferred_enter()/_exit() are called in
non-migration contexts.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
---
include/linux/printk.h | 9 +++++----
kernel/printk/internal.h | 3 +++
kernel/printk/printk_safe.c | 12 ++++++++++++
3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 2fde40cc9677..d8b3f51d9e98 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -157,15 +157,16 @@ int _printk(const char *fmt, ...);
*/
__printf(1, 2) __cold int _printk_deferred(const char *fmt, ...);

-extern void __printk_safe_enter(void);
-extern void __printk_safe_exit(void);
+extern void __printk_deferred_enter(void);
+extern void __printk_deferred_exit(void);
+
/*
* The printk_deferred_enter/exit macros are available only as a hack for
* some code paths that need to defer all printk console printing. Interrupts
* must be disabled for the deferred duration.
*/
-#define printk_deferred_enter __printk_safe_enter
-#define printk_deferred_exit __printk_safe_exit
+#define printk_deferred_enter() __printk_deferred_enter()
+#define printk_deferred_exit() __printk_deferred_exit()

/*
* Please don't use printk_ratelimit(), because it shares ratelimiting state
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 739b82adc383..831f95f26d48 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -53,6 +53,9 @@ int vprintk_store(int facility, int level,
__printf(1, 0) int vprintk_default(const char *fmt, va_list args);
__printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);

+void __printk_safe_enter(void);
+void __printk_safe_exit(void);
+
bool printk_percpu_data_ready(void);

#define printk_safe_enter_irqsave(flags) \
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 6d10927a07d8..4421ccac3113 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -26,6 +26,18 @@ void __printk_safe_exit(void)
this_cpu_dec(printk_context);
}

+void __printk_deferred_enter(void)
+{
+ cant_migrate();
+ __printk_safe_enter();
+}
+
+void __printk_deferred_exit(void)
+{
+ cant_migrate();
+ __printk_safe_exit();
+}
+
asmlinkage int vprintk(const char *fmt, va_list args)
{
#ifdef CONFIG_KGDB_KDB
--
2.39.2