vpanic() is useful for implementing runtime verification reactors. Add it.

Signed-off-by: Nam Cao <namcao@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
---
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 include/linux/panic.h |  3 +++
 kernel/panic.c        | 17 ++++++++++++-----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/include/linux/panic.h b/include/linux/panic.h
index 54d90b6c5f47..3522f8c441f4 100644
--- a/include/linux/panic.h
+++ b/include/linux/panic.h
@@ -3,6 +3,7 @@
 #define _LINUX_PANIC_H
 
 #include <linux/compiler_attributes.h>
+#include <linux/stdarg.h>
 #include <linux/types.h>
 
 struct pt_regs;
@@ -10,6 +11,8 @@ struct pt_regs;
 extern long (*panic_blink)(int state);
 __printf(1, 2)
 void panic(const char *fmt, ...) __noreturn __cold;
+__printf(1, 0)
+void vpanic(const char *fmt, va_list args) __noreturn __cold;
 void nmi_panic(struct pt_regs *regs, const char *msg);
 void check_panic_on_warn(const char *origin);
 extern void oops_enter(void);
diff --git a/kernel/panic.c b/kernel/panic.c
index d8635d5cecb2..df799d784b61 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -277,17 +277,16 @@ static void panic_other_cpus_shutdown(bool crash_kexec)
 }
 
 /**
- *	panic - halt the system
+ *	vpanic - halt the system
  *	@fmt: The text string to print
  *
  *	Display a message, then perform cleanups.
  *
  *	This function never returns.
  */
-void panic(const char *fmt, ...)
+void vpanic(const char *fmt, va_list args)
 {
 	static char buf[1024];
-	va_list args;
 	long i, i_next = 0, len;
 	int state = 0;
 	int old_cpu, this_cpu;
@@ -338,9 +337,7 @@ void panic(const char *fmt, ...)
 
 	console_verbose();
 	bust_spinlocks(1);
-	va_start(args, fmt);
 	len = vscnprintf(buf, sizeof(buf), fmt, args);
-	va_end(args);
 
 	if (len && buf[len - 1] == '\n')
 		buf[len - 1] = '\0';
@@ -477,7 +474,17 @@ void panic(const char *fmt, ...)
 		mdelay(PANIC_TIMER_STEP);
 	}
 }
+EXPORT_SYMBOL(vpanic);
 
+/* Identical to vpanic(), except it takes variadic arguments instead of va_list */
+void panic(const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	vpanic(fmt, args);
+	va_end(args);
+}
 EXPORT_SYMBOL(panic);
 
 #define TAINT_FLAG(taint, _c_true, _c_false, _module)			\
-- 
2.39.5

On Wed 2025-04-30 13:02:18, Nam Cao wrote:
> vpanic() is useful for implementing runtime verification reactors. Add it.
> 
> Signed-off-by: Nam Cao <namcao@linutronix.de>
> Reviewed-by: Petr Mladek <pmladek@suse.com>
> ---
> Cc: John Ogness <john.ogness@linutronix.de>
> Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  include/linux/panic.h |  3 +++
>  kernel/panic.c        | 17 ++++++++++++-----
>  2 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/panic.h b/include/linux/panic.h
> index 54d90b6c5f47..3522f8c441f4 100644
> --- a/include/linux/panic.h
> +++ b/include/linux/panic.h
> @@ -3,6 +3,7 @@
>  #define _LINUX_PANIC_H
>  
>  #include <linux/compiler_attributes.h>
> +#include <linux/stdarg.h>
>  #include <linux/types.h>
>  
>  struct pt_regs;
> @@ -10,6 +11,8 @@ struct pt_regs;
>  extern long (*panic_blink)(int state);
>  __printf(1, 2)
>  void panic(const char *fmt, ...) __noreturn __cold;
> +__printf(1, 0)
> +void vpanic(const char *fmt, va_list args) __noreturn __cold;
>  void nmi_panic(struct pt_regs *regs, const char *msg);
>  void check_panic_on_warn(const char *origin);
>  extern void oops_enter(void);
> diff --git a/kernel/panic.c b/kernel/panic.c
> index d8635d5cecb2..df799d784b61 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -277,17 +277,16 @@ static void panic_other_cpus_shutdown(bool crash_kexec)
>  }
>  
>  /**
> - *	panic - halt the system
> + *	vpanic - halt the system
>   *	@fmt: The text string to print
>   *
I wanted to double check the __printf attributtes and compiled this
file with W=1:

$> make W=1 kernel/panic.o
  CC      kernel/panic.o
kernel/panic.c:288: warning: Function parameter or struct member 'args' not described in 'vpanic'

So, we should add description of the new @args parameter...


>   *	Display a message, then perform cleanups.
>   *
>   *	This function never returns.
>   */
> -void panic(const char *fmt, ...)
> +void vpanic(const char *fmt, va_list args)
>  {
>  	static char buf[1024];
> -	va_list args;
>  	long i, i_next = 0, len;
>  	int state = 0;
>  	int old_cpu, this_cpu;

Otherwise, it looks good.

Best Regards,
Petr