2019-08-20 02:49:40 +00:00
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* This file provides wrappers with sanitizer instrumentation for non-atomic
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* bit operations.
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*
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* To use this functionality, an arch's bitops.h file needs to define each of
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* the below bit operations with an arch_ prefix (e.g. arch_set_bit(),
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* arch___set_bit(), etc.).
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*/
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#ifndef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
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#define _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
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2020-01-21 16:05:10 +00:00
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#include <linux/instrumented.h>
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2019-08-20 02:49:40 +00:00
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/**
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* __set_bit - Set a bit in memory
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* @nr: the bit to set
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* @addr: the address to start counting from
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*
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* Unlike set_bit(), this function is non-atomic. If it is called on the same
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* region of memory concurrently, the effect may be that only one operation
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* succeeds.
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*/
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2022-01-13 15:53:56 +00:00
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static __always_inline void __set_bit(long nr, volatile unsigned long *addr)
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2019-08-20 02:49:40 +00:00
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{
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2020-01-21 16:05:10 +00:00
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instrument_write(addr + BIT_WORD(nr), sizeof(long));
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2019-08-20 02:49:40 +00:00
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arch___set_bit(nr, addr);
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}
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/**
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* __clear_bit - Clears a bit in memory
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* @nr: the bit to clear
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* @addr: the address to start counting from
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*
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* Unlike clear_bit(), this function is non-atomic. If it is called on the same
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* region of memory concurrently, the effect may be that only one operation
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* succeeds.
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*/
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2022-01-13 15:53:56 +00:00
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static __always_inline void __clear_bit(long nr, volatile unsigned long *addr)
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2019-08-20 02:49:40 +00:00
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{
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2020-01-21 16:05:10 +00:00
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instrument_write(addr + BIT_WORD(nr), sizeof(long));
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2019-08-20 02:49:40 +00:00
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arch___clear_bit(nr, addr);
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}
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/**
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* __change_bit - Toggle a bit in memory
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* @nr: the bit to change
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* @addr: the address to start counting from
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*
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* Unlike change_bit(), this function is non-atomic. If it is called on the same
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* region of memory concurrently, the effect may be that only one operation
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* succeeds.
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*/
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2022-01-13 15:53:56 +00:00
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static __always_inline void __change_bit(long nr, volatile unsigned long *addr)
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2019-08-20 02:49:40 +00:00
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{
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2020-01-21 16:05:10 +00:00
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instrument_write(addr + BIT_WORD(nr), sizeof(long));
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2019-08-20 02:49:40 +00:00
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arch___change_bit(nr, addr);
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}
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2022-01-13 15:53:56 +00:00
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static __always_inline void __instrument_read_write_bitop(long nr, volatile unsigned long *addr)
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bitops, kcsan: Partially revert instrumentation for non-atomic bitops
Previous to the change to distinguish read-write accesses, when
CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=y is set, KCSAN would consider
the non-atomic bitops as atomic. We want to partially revert to this
behaviour, but with one important distinction: report racing
modifications, since lost bits due to non-atomicity are certainly
possible.
Given the operations here only modify a single bit, assuming
non-atomicity of the writer is sufficient may be reasonable for certain
usage (and follows the permissible nature of the "assume plain writes
atomic" rule). In other words:
1. We want non-atomic read-modify-write races to be reported;
this is accomplished by kcsan_check_read(), where any
concurrent write (atomic or not) will generate a report.
2. We do not want to report races with marked readers, but -do-
want to report races with unmarked readers; this is
accomplished by the instrument_write() ("assume atomic
write" with Kconfig option set).
With the above rules, when KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected,
it is hoped that KCSAN's reporting behaviour is better aligned with
current expected permissible usage for non-atomic bitops.
Note that, a side-effect of not telling KCSAN that the accesses are
read-writes, is that this information is not displayed in the access
summary in the report. It is, however, visible in inline-expanded stack
traces. For now, it does not make sense to introduce yet another special
case to KCSAN's runtime, only to cater to the case here.
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-13 16:38:59 +00:00
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{
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if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC)) {
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/*
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* We treat non-atomic read-write bitops a little more special.
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* Given the operations here only modify a single bit, assuming
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* non-atomicity of the writer is sufficient may be reasonable
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* for certain usage (and follows the permissible nature of the
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* assume-plain-writes-atomic rule):
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* 1. report read-modify-write races -> check read;
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* 2. do not report races with marked readers, but do report
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* races with unmarked readers -> check "atomic" write.
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*/
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kcsan_check_read(addr + BIT_WORD(nr), sizeof(long));
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/*
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* Use generic write instrumentation, in case other sanitizers
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* or tools are enabled alongside KCSAN.
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*/
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instrument_write(addr + BIT_WORD(nr), sizeof(long));
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} else {
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instrument_read_write(addr + BIT_WORD(nr), sizeof(long));
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}
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}
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2019-08-20 02:49:40 +00:00
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/**
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* __test_and_set_bit - Set a bit and return its old value
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* @nr: Bit to set
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* @addr: Address to count from
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*
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* This operation is non-atomic. If two instances of this operation race, one
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* can appear to succeed but actually fail.
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*/
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2022-01-13 15:53:56 +00:00
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static __always_inline bool __test_and_set_bit(long nr, volatile unsigned long *addr)
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2019-08-20 02:49:40 +00:00
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{
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bitops, kcsan: Partially revert instrumentation for non-atomic bitops
Previous to the change to distinguish read-write accesses, when
CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=y is set, KCSAN would consider
the non-atomic bitops as atomic. We want to partially revert to this
behaviour, but with one important distinction: report racing
modifications, since lost bits due to non-atomicity are certainly
possible.
Given the operations here only modify a single bit, assuming
non-atomicity of the writer is sufficient may be reasonable for certain
usage (and follows the permissible nature of the "assume plain writes
atomic" rule). In other words:
1. We want non-atomic read-modify-write races to be reported;
this is accomplished by kcsan_check_read(), where any
concurrent write (atomic or not) will generate a report.
2. We do not want to report races with marked readers, but -do-
want to report races with unmarked readers; this is
accomplished by the instrument_write() ("assume atomic
write" with Kconfig option set).
With the above rules, when KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected,
it is hoped that KCSAN's reporting behaviour is better aligned with
current expected permissible usage for non-atomic bitops.
Note that, a side-effect of not telling KCSAN that the accesses are
read-writes, is that this information is not displayed in the access
summary in the report. It is, however, visible in inline-expanded stack
traces. For now, it does not make sense to introduce yet another special
case to KCSAN's runtime, only to cater to the case here.
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-13 16:38:59 +00:00
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__instrument_read_write_bitop(nr, addr);
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2019-08-20 02:49:40 +00:00
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return arch___test_and_set_bit(nr, addr);
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}
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/**
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* __test_and_clear_bit - Clear a bit and return its old value
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* @nr: Bit to clear
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* @addr: Address to count from
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*
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* This operation is non-atomic. If two instances of this operation race, one
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* can appear to succeed but actually fail.
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*/
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2022-01-13 15:53:56 +00:00
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static __always_inline bool __test_and_clear_bit(long nr, volatile unsigned long *addr)
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2019-08-20 02:49:40 +00:00
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{
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bitops, kcsan: Partially revert instrumentation for non-atomic bitops
Previous to the change to distinguish read-write accesses, when
CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=y is set, KCSAN would consider
the non-atomic bitops as atomic. We want to partially revert to this
behaviour, but with one important distinction: report racing
modifications, since lost bits due to non-atomicity are certainly
possible.
Given the operations here only modify a single bit, assuming
non-atomicity of the writer is sufficient may be reasonable for certain
usage (and follows the permissible nature of the "assume plain writes
atomic" rule). In other words:
1. We want non-atomic read-modify-write races to be reported;
this is accomplished by kcsan_check_read(), where any
concurrent write (atomic or not) will generate a report.
2. We do not want to report races with marked readers, but -do-
want to report races with unmarked readers; this is
accomplished by the instrument_write() ("assume atomic
write" with Kconfig option set).
With the above rules, when KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected,
it is hoped that KCSAN's reporting behaviour is better aligned with
current expected permissible usage for non-atomic bitops.
Note that, a side-effect of not telling KCSAN that the accesses are
read-writes, is that this information is not displayed in the access
summary in the report. It is, however, visible in inline-expanded stack
traces. For now, it does not make sense to introduce yet another special
case to KCSAN's runtime, only to cater to the case here.
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-13 16:38:59 +00:00
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__instrument_read_write_bitop(nr, addr);
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2019-08-20 02:49:40 +00:00
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return arch___test_and_clear_bit(nr, addr);
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}
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/**
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* __test_and_change_bit - Change a bit and return its old value
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* @nr: Bit to change
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* @addr: Address to count from
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*
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* This operation is non-atomic. If two instances of this operation race, one
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* can appear to succeed but actually fail.
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*/
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2022-01-13 15:53:56 +00:00
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static __always_inline bool __test_and_change_bit(long nr, volatile unsigned long *addr)
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2019-08-20 02:49:40 +00:00
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{
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bitops, kcsan: Partially revert instrumentation for non-atomic bitops
Previous to the change to distinguish read-write accesses, when
CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=y is set, KCSAN would consider
the non-atomic bitops as atomic. We want to partially revert to this
behaviour, but with one important distinction: report racing
modifications, since lost bits due to non-atomicity are certainly
possible.
Given the operations here only modify a single bit, assuming
non-atomicity of the writer is sufficient may be reasonable for certain
usage (and follows the permissible nature of the "assume plain writes
atomic" rule). In other words:
1. We want non-atomic read-modify-write races to be reported;
this is accomplished by kcsan_check_read(), where any
concurrent write (atomic or not) will generate a report.
2. We do not want to report races with marked readers, but -do-
want to report races with unmarked readers; this is
accomplished by the instrument_write() ("assume atomic
write" with Kconfig option set).
With the above rules, when KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected,
it is hoped that KCSAN's reporting behaviour is better aligned with
current expected permissible usage for non-atomic bitops.
Note that, a side-effect of not telling KCSAN that the accesses are
read-writes, is that this information is not displayed in the access
summary in the report. It is, however, visible in inline-expanded stack
traces. For now, it does not make sense to introduce yet another special
case to KCSAN's runtime, only to cater to the case here.
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-13 16:38:59 +00:00
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__instrument_read_write_bitop(nr, addr);
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2019-08-20 02:49:40 +00:00
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return arch___test_and_change_bit(nr, addr);
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}
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/**
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* test_bit - Determine whether a bit is set
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* @nr: bit number to test
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* @addr: Address to start counting from
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*/
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2022-01-13 15:53:56 +00:00
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static __always_inline bool test_bit(long nr, const volatile unsigned long *addr)
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2019-08-20 02:49:40 +00:00
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{
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2020-01-21 16:05:10 +00:00
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instrument_atomic_read(addr + BIT_WORD(nr), sizeof(long));
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2019-08-20 02:49:40 +00:00
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return arch_test_bit(nr, addr);
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}
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#endif /* _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H */
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