709e5a08d4
On older kernels (5.4 and older), building the kernel with clang can
cause the section name to end up with "" in them, which can cause lots
of runtime issues as that is not normally a valid portion of the string.
This was fixed up in newer kernels with commit 33def8498fdd ("treewide:
Convert macro and uses of __section(foo) to __section("foo")") but
that's too heavy-handed for older kernels.
So for now, fix up the problem that commit 62c07983bef9 ("once: add
DO_ONCE_SLOW() for sleepable contexts") caused by being backported by
removing the "" characters from the section definition.
Reported-by: Oleksandr Tymoshenko <ovt@google.com>
Reported-by: Yongqin Liu <yongqin.liu@linaro.org>
Tested-by: Yongqin Liu <yongqin.liu@linaro.org>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Link: https://lore.kernel.org/r/20221029011211.4049810-1-ovt@google.com
Link: https://lore.kernel.org/r/CAMSo37XApZ_F5nSQYWFsSqKdMv_gBpfdKG3KN1TDB+QNXqSh0A@mail.gmail.com
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David S. Miller <davem@davemloft.net>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
89 lines
2.8 KiB
C
89 lines
2.8 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_slow_start(bool *done);
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void __do_once_slow_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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* Not 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 ___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_SLOW(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_slow_start(&___done); \
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if (unlikely(___ret)) { \
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func(__VA_ARGS__); \
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__do_once_slow_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_once_wait(buf, nbytes) \
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DO_ONCE(get_random_bytes_wait, (buf), (nbytes)) \
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#define get_random_slow_once(buf, nbytes) \
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DO_ONCE_SLOW(get_random_bytes, (buf), (nbytes))
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#endif /* _LINUX_ONCE_H */
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