printk: rename vprintk_func to vprintk

The printk code is already hard enough to understand. Remove an
unnecessary indirection by renaming vprintk_func to vprintk (adding
the asmlinkage annotation), and removing the vprintk definition from
printk.c. That way, printk is implemented in terms of vprintk as one
would expect, and there's no "vprintk_func, what's that? Some function
pointer that gets set where?"

The declaration of vprintk in linux/printk.h already has the
__printf(1,0) attribute, there's no point repeating that with the
definition - it's for diagnostics in callers.

linux/printk.h already contains a static inline {return 0;} definition
of vprintk when !CONFIG_PRINTK.

Since the corresponding stub definition of vprintk_func was not marked
"static inline", any translation unit including internal.h would get a
definition of vprintk_func - it just so happens that for
!CONFIG_PRINTK, there is precisely one such TU, namely printk.c. Had
there been more, it would be a link error; now it's just a silly waste
of a few bytes of .text, which one must assume are rather precious to
anyone disabling PRINTK.

$ objdump -dr kernel/printk/printk.o
00000330 <vprintk_func>:
 330:   31 c0                   xor    %eax,%eax
 332:   c3                      ret
 333:   8d b4 26 00 00 00 00    lea    0x0(%esi,%eiz,1),%esi
 33a:   8d b6 00 00 00 00       lea    0x0(%esi),%esi

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210323144201.486050-1-linux@rasmusvillemoes.dk

1 files changed, 2 insertions, 1 deletions

diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index bbf5c1993636..7a1414622051 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -357,7 +357,7 @@ void __printk_safe_exit(void)
 	this_cpu_dec(printk_context);
 }
 
-__printf(1, 0) int vprintk_func(const char *fmt, va_list args)
+asmlinkage int vprintk(const char *fmt, va_list args)
 {
 #ifdef CONFIG_KGDB_KDB
 	/* Allow to pass printk() to kdb but avoid a recursion. */
@@ -411,3 +411,4 @@ void __init printk_safe_init(void)
 	/* Flush pending messages that did not have scheduled IRQ works. */
 	printk_safe_flush();
 }
+EXPORT_SYMBOL(vprintk);