forked from mirrors/linux
dbefa1f31a
Commitb1fca27d38("kernel debug: support resetting WARN*_ONCE") added support for clearing the state of once warnings. However, it is not functional when CONFIG_LD_DEAD_CODE_DATA_ELIMINATION or CONFIG_LTO_CLANG is enabled, because .data.once matches the .data.[0-9a-zA-Z_]* pattern in the DATA_MAIN macro. Commitcb87481ee8("kbuild: linker script do not match C names unless LD_DEAD_CODE_DATA_ELIMINATION is configured") was introduced to suppress the issue for the default CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=n case, providing a minimal fix for stable backporting. We were aware this did not address the issue for CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y. The plan was to apply correct fixes and then revertcb87481ee8. [1] Seven years have passed since then, yet the #ifdef workaround remains in place. Meanwhile, commitb1fca27d38introduced the .data.once section, and commitdc5723b02e("kbuild: add support for Clang LTO") extended the #ifdef. Using a ".." separator in the section name fixes the issue for CONFIG_LD_DEAD_CODE_DATA_ELIMINATION and CONFIG_LTO_CLANG. [1]: https://lore.kernel.org/linux-kbuild/CAK7LNASck6BfdLnESxXUeECYL26yUDm0cwRZuM4gmaWUkxjL5g@mail.gmail.com/ Fixes:b1fca27d38("kernel debug: support resetting WARN*_ONCE") Fixes:dc5723b02e("kbuild: add support for Clang LTO") Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
86 lines
2.7 KiB
C
86 lines
2.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_ONCE_H
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#define _LINUX_ONCE_H
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#include <linux/types.h>
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#include <linux/jump_label.h>
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/* Helpers used from arbitrary contexts.
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* Hard irqs are blocked, be cautious.
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*/
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bool __do_once_start(bool *done, unsigned long *flags);
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void __do_once_done(bool *done, struct static_key_true *once_key,
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unsigned long *flags, struct module *mod);
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/* Variant for process contexts only. */
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bool __do_once_sleepable_start(bool *done);
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void __do_once_sleepable_done(bool *done, struct static_key_true *once_key,
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struct module *mod);
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/* Call a function exactly once. The idea of DO_ONCE() is to perform
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* a function call such as initialization of random seeds, etc, only
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* once, where DO_ONCE() can live in the fast-path. After @func has
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* been called with the passed arguments, the static key will patch
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* out the condition into a nop. DO_ONCE() guarantees type safety of
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* arguments!
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*
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* Note that the following is not equivalent ...
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*
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* DO_ONCE(func, arg);
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* DO_ONCE(func, arg);
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*
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* ... to this version:
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*
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* void foo(void)
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* {
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* DO_ONCE(func, arg);
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* }
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*
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* foo();
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* foo();
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*
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* In case the one-time invocation could be triggered from multiple
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* places, then a common helper function must be defined, so that only
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* a single static key will be placed there!
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*/
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#define DO_ONCE(func, ...) \
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({ \
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bool ___ret = false; \
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static bool __section(".data..once") ___done = false; \
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static DEFINE_STATIC_KEY_TRUE(___once_key); \
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if (static_branch_unlikely(&___once_key)) { \
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unsigned long ___flags; \
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___ret = __do_once_start(&___done, &___flags); \
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if (unlikely(___ret)) { \
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func(__VA_ARGS__); \
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__do_once_done(&___done, &___once_key, \
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&___flags, THIS_MODULE); \
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} \
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} \
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___ret; \
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})
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/* Variant of DO_ONCE() for process/sleepable contexts. */
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#define DO_ONCE_SLEEPABLE(func, ...) \
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({ \
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bool ___ret = false; \
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static bool __section(".data..once") ___done = false; \
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static DEFINE_STATIC_KEY_TRUE(___once_key); \
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if (static_branch_unlikely(&___once_key)) { \
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___ret = __do_once_sleepable_start(&___done); \
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if (unlikely(___ret)) { \
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func(__VA_ARGS__); \
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__do_once_sleepable_done(&___done, &___once_key,\
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THIS_MODULE); \
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} \
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} \
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___ret; \
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})
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#define get_random_once(buf, nbytes) \
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DO_ONCE(get_random_bytes, (buf), (nbytes))
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#define get_random_sleepable_once(buf, nbytes) \
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DO_ONCE_SLEEPABLE(get_random_bytes, (buf), (nbytes))
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#endif /* _LINUX_ONCE_H */
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