Revision 8c89ecf5c13b0504018c5045896a0b78d5d811e6 authored by Alexander Potapenko on 11 January 2023, 10:50:12 UTC, committed by Alexander Potapenko on 07 February 2023, 09:50:25 UTC
When building the kernel with W=1, the compiler reports numerous warnings about the missing prototypes for KMSAN instrumentation hooks. Because these functions are not supposed to be called explicitly by the kernel code (calls to them are emitted by the compiler), they do not have to be declared in the headers. Instead, we add forward declarations right before the definitions to silence the warnings produced by -Wmissing-prototypes. Reported-by: kernel test robot <lkp@intel.com> Link: https://lore.kernel.org/lkml/202301020356.dFruA4I5-lkp@intel.com/T/ Reported-by: Vlastimil Babka <vbabka@suse.cz> Suggested-by: Marco Elver <elver@google.com> Signed-off-by: Alexander Potapenko <glider@google.com>
1 parent 8b0ffea
once.h
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_ONCE_H
#define _LINUX_ONCE_H
#include <linux/types.h>
#include <linux/jump_label.h>
/* Helpers used from arbitrary contexts.
* Hard irqs are blocked, be cautious.
*/
bool __do_once_start(bool *done, unsigned long *flags);
void __do_once_done(bool *done, struct static_key_true *once_key,
unsigned long *flags, struct module *mod);
/* Variant for process contexts only. */
bool __do_once_sleepable_start(bool *done);
void __do_once_sleepable_done(bool *done, struct static_key_true *once_key,
struct module *mod);
/* Call a function exactly once. The idea of DO_ONCE() is to perform
* a function call such as initialization of random seeds, etc, only
* once, where DO_ONCE() can live in the fast-path. After @func has
* been called with the passed arguments, the static key will patch
* out the condition into a nop. DO_ONCE() guarantees type safety of
* arguments!
*
* Note that the following is not equivalent ...
*
* DO_ONCE(func, arg);
* DO_ONCE(func, arg);
*
* ... to this version:
*
* void foo(void)
* {
* DO_ONCE(func, arg);
* }
*
* foo();
* foo();
*
* In case the one-time invocation could be triggered from multiple
* places, then a common helper function must be defined, so that only
* a single static key will be placed there!
*/
#define DO_ONCE(func, ...) \
({ \
bool ___ret = false; \
static bool __section(".data.once") ___done = false; \
static DEFINE_STATIC_KEY_TRUE(___once_key); \
if (static_branch_unlikely(&___once_key)) { \
unsigned long ___flags; \
___ret = __do_once_start(&___done, &___flags); \
if (unlikely(___ret)) { \
func(__VA_ARGS__); \
__do_once_done(&___done, &___once_key, \
&___flags, THIS_MODULE); \
} \
} \
___ret; \
})
/* Variant of DO_ONCE() for process/sleepable contexts. */
#define DO_ONCE_SLEEPABLE(func, ...) \
({ \
bool ___ret = false; \
static bool __section(".data.once") ___done = false; \
static DEFINE_STATIC_KEY_TRUE(___once_key); \
if (static_branch_unlikely(&___once_key)) { \
___ret = __do_once_sleepable_start(&___done); \
if (unlikely(___ret)) { \
func(__VA_ARGS__); \
__do_once_sleepable_done(&___done, &___once_key,\
THIS_MODULE); \
} \
} \
___ret; \
})
#define get_random_once(buf, nbytes) \
DO_ONCE(get_random_bytes, (buf), (nbytes))
#define get_random_sleepable_once(buf, nbytes) \
DO_ONCE_SLEEPABLE(get_random_bytes, (buf), (nbytes))
#endif /* _LINUX_ONCE_H */
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