mirror of
https://github.com/edk2-porting/linux-next.git
synced 2025-01-15 09:03:59 +08:00
068df05363
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>
139 lines
4.3 KiB
C
139 lines
4.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
|
|
/*
|
|
* This file provides wrappers with sanitizer instrumentation for non-atomic
|
|
* bit operations.
|
|
*
|
|
* To use this functionality, an arch's bitops.h file needs to define each of
|
|
* the below bit operations with an arch_ prefix (e.g. arch_set_bit(),
|
|
* arch___set_bit(), etc.).
|
|
*/
|
|
#ifndef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
|
|
#define _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
|
|
|
|
#include <linux/instrumented.h>
|
|
|
|
/**
|
|
* __set_bit - Set a bit in memory
|
|
* @nr: the bit to set
|
|
* @addr: the address to start counting from
|
|
*
|
|
* Unlike set_bit(), this function is non-atomic. If it is called on the same
|
|
* region of memory concurrently, the effect may be that only one operation
|
|
* succeeds.
|
|
*/
|
|
static inline void __set_bit(long nr, volatile unsigned long *addr)
|
|
{
|
|
instrument_write(addr + BIT_WORD(nr), sizeof(long));
|
|
arch___set_bit(nr, addr);
|
|
}
|
|
|
|
/**
|
|
* __clear_bit - Clears a bit in memory
|
|
* @nr: the bit to clear
|
|
* @addr: the address to start counting from
|
|
*
|
|
* Unlike clear_bit(), this function is non-atomic. If it is called on the same
|
|
* region of memory concurrently, the effect may be that only one operation
|
|
* succeeds.
|
|
*/
|
|
static inline void __clear_bit(long nr, volatile unsigned long *addr)
|
|
{
|
|
instrument_write(addr + BIT_WORD(nr), sizeof(long));
|
|
arch___clear_bit(nr, addr);
|
|
}
|
|
|
|
/**
|
|
* __change_bit - Toggle a bit in memory
|
|
* @nr: the bit to change
|
|
* @addr: the address to start counting from
|
|
*
|
|
* Unlike change_bit(), this function is non-atomic. If it is called on the same
|
|
* region of memory concurrently, the effect may be that only one operation
|
|
* succeeds.
|
|
*/
|
|
static inline void __change_bit(long nr, volatile unsigned long *addr)
|
|
{
|
|
instrument_write(addr + BIT_WORD(nr), sizeof(long));
|
|
arch___change_bit(nr, addr);
|
|
}
|
|
|
|
static inline void __instrument_read_write_bitop(long nr, volatile unsigned long *addr)
|
|
{
|
|
if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC)) {
|
|
/*
|
|
* We treat non-atomic read-write bitops a little more special.
|
|
* 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):
|
|
* 1. report read-modify-write races -> check read;
|
|
* 2. do not report races with marked readers, but do report
|
|
* races with unmarked readers -> check "atomic" write.
|
|
*/
|
|
kcsan_check_read(addr + BIT_WORD(nr), sizeof(long));
|
|
/*
|
|
* Use generic write instrumentation, in case other sanitizers
|
|
* or tools are enabled alongside KCSAN.
|
|
*/
|
|
instrument_write(addr + BIT_WORD(nr), sizeof(long));
|
|
} else {
|
|
instrument_read_write(addr + BIT_WORD(nr), sizeof(long));
|
|
}
|
|
}
|
|
|
|
/**
|
|
* __test_and_set_bit - Set a bit and return its old value
|
|
* @nr: Bit to set
|
|
* @addr: Address to count from
|
|
*
|
|
* This operation is non-atomic. If two instances of this operation race, one
|
|
* can appear to succeed but actually fail.
|
|
*/
|
|
static inline bool __test_and_set_bit(long nr, volatile unsigned long *addr)
|
|
{
|
|
__instrument_read_write_bitop(nr, addr);
|
|
return arch___test_and_set_bit(nr, addr);
|
|
}
|
|
|
|
/**
|
|
* __test_and_clear_bit - Clear a bit and return its old value
|
|
* @nr: Bit to clear
|
|
* @addr: Address to count from
|
|
*
|
|
* This operation is non-atomic. If two instances of this operation race, one
|
|
* can appear to succeed but actually fail.
|
|
*/
|
|
static inline bool __test_and_clear_bit(long nr, volatile unsigned long *addr)
|
|
{
|
|
__instrument_read_write_bitop(nr, addr);
|
|
return arch___test_and_clear_bit(nr, addr);
|
|
}
|
|
|
|
/**
|
|
* __test_and_change_bit - Change a bit and return its old value
|
|
* @nr: Bit to change
|
|
* @addr: Address to count from
|
|
*
|
|
* This operation is non-atomic. If two instances of this operation race, one
|
|
* can appear to succeed but actually fail.
|
|
*/
|
|
static inline bool __test_and_change_bit(long nr, volatile unsigned long *addr)
|
|
{
|
|
__instrument_read_write_bitop(nr, addr);
|
|
return arch___test_and_change_bit(nr, addr);
|
|
}
|
|
|
|
/**
|
|
* test_bit - Determine whether a bit is set
|
|
* @nr: bit number to test
|
|
* @addr: Address to start counting from
|
|
*/
|
|
static inline bool test_bit(long nr, const volatile unsigned long *addr)
|
|
{
|
|
instrument_atomic_read(addr + BIT_WORD(nr), sizeof(long));
|
|
return arch_test_bit(nr, addr);
|
|
}
|
|
|
|
#endif /* _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H */
|