mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-23 23:08:42 +07:00
4d3b57da15
Our userspace <linux/compiler.h> defines READ_ONCE() in a way that clang
doesn't like, as we have an anonymous union in which neither field is
initialized.
WRITE_ONCE() is fine since it initializes the __val field. For
READ_ONCE() we can keep clang and GCC happy with a dummy initialization
of the __c field, so let's do that.
At the same time, let's split READ_ONCE() and WRITE_ONCE() over several
lines for legibility, as we do in the in-kernel <linux/compiler.h>.
Reported-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Reported-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Tested-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Fixes: 6aa7de0591 ("locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()")
Link: http://lkml.kernel.org/r/20180404163445.16492-1-mark.rutland@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
176 lines
4.6 KiB
C
176 lines
4.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _TOOLS_LINUX_COMPILER_H_
|
|
#define _TOOLS_LINUX_COMPILER_H_
|
|
|
|
#ifdef __GNUC__
|
|
#include <linux/compiler-gcc.h>
|
|
#endif
|
|
|
|
#ifndef __compiletime_error
|
|
# define __compiletime_error(message)
|
|
#endif
|
|
|
|
/* Optimization barrier */
|
|
/* The "volatile" is due to gcc bugs */
|
|
#define barrier() __asm__ __volatile__("": : :"memory")
|
|
|
|
#ifndef __always_inline
|
|
# define __always_inline inline __attribute__((always_inline))
|
|
#endif
|
|
|
|
#ifndef noinline
|
|
#define noinline
|
|
#endif
|
|
|
|
/* Are two types/vars the same type (ignoring qualifiers)? */
|
|
#ifndef __same_type
|
|
# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
|
|
#endif
|
|
|
|
#ifdef __ANDROID__
|
|
/*
|
|
* FIXME: Big hammer to get rid of tons of:
|
|
* "warning: always_inline function might not be inlinable"
|
|
*
|
|
* At least on android-ndk-r12/platforms/android-24/arch-arm
|
|
*/
|
|
#undef __always_inline
|
|
#define __always_inline inline
|
|
#endif
|
|
|
|
#define __user
|
|
#define __rcu
|
|
#define __read_mostly
|
|
|
|
#ifndef __attribute_const__
|
|
# define __attribute_const__
|
|
#endif
|
|
|
|
#ifndef __maybe_unused
|
|
# define __maybe_unused __attribute__((unused))
|
|
#endif
|
|
|
|
#ifndef __used
|
|
# define __used __attribute__((__unused__))
|
|
#endif
|
|
|
|
#ifndef __packed
|
|
# define __packed __attribute__((__packed__))
|
|
#endif
|
|
|
|
#ifndef __force
|
|
# define __force
|
|
#endif
|
|
|
|
#ifndef __weak
|
|
# define __weak __attribute__((weak))
|
|
#endif
|
|
|
|
#ifndef likely
|
|
# define likely(x) __builtin_expect(!!(x), 1)
|
|
#endif
|
|
|
|
#ifndef unlikely
|
|
# define unlikely(x) __builtin_expect(!!(x), 0)
|
|
#endif
|
|
|
|
#ifndef __init
|
|
# define __init
|
|
#endif
|
|
|
|
#ifndef noinline
|
|
# define noinline
|
|
#endif
|
|
|
|
#define uninitialized_var(x) x = *(&(x))
|
|
|
|
#include <linux/types.h>
|
|
|
|
/*
|
|
* Following functions are taken from kernel sources and
|
|
* break aliasing rules in their original form.
|
|
*
|
|
* While kernel is compiled with -fno-strict-aliasing,
|
|
* perf uses -Wstrict-aliasing=3 which makes build fail
|
|
* under gcc 4.4.
|
|
*
|
|
* Using extra __may_alias__ type to allow aliasing
|
|
* in this case.
|
|
*/
|
|
typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
|
|
typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
|
|
typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
|
|
typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
|
|
|
|
static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
|
|
{
|
|
switch (size) {
|
|
case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break;
|
|
case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
|
|
case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
|
|
case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
|
|
default:
|
|
barrier();
|
|
__builtin_memcpy((void *)res, (const void *)p, size);
|
|
barrier();
|
|
}
|
|
}
|
|
|
|
static __always_inline void __write_once_size(volatile void *p, void *res, int size)
|
|
{
|
|
switch (size) {
|
|
case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break;
|
|
case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
|
|
case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
|
|
case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
|
|
default:
|
|
barrier();
|
|
__builtin_memcpy((void *)p, (const void *)res, size);
|
|
barrier();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Prevent the compiler from merging or refetching reads or writes. The
|
|
* compiler is also forbidden from reordering successive instances of
|
|
* READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
|
|
* particular ordering. One way to make the compiler aware of ordering is to
|
|
* put the two invocations of READ_ONCE or WRITE_ONCE in different C
|
|
* statements.
|
|
*
|
|
* These two macros will also work on aggregate data types like structs or
|
|
* unions. If the size of the accessed data type exceeds the word size of
|
|
* the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
|
|
* fall back to memcpy and print a compile-time warning.
|
|
*
|
|
* Their two major use cases are: (1) Mediating communication between
|
|
* process-level code and irq/NMI handlers, all running on the same CPU,
|
|
* and (2) Ensuring that the compiler does not fold, spindle, or otherwise
|
|
* mutilate accesses that either do not require ordering or that interact
|
|
* with an explicit memory barrier or atomic instruction that provides the
|
|
* required ordering.
|
|
*/
|
|
|
|
#define READ_ONCE(x) \
|
|
({ \
|
|
union { typeof(x) __val; char __c[1]; } __u = \
|
|
{ .__c = { 0 } }; \
|
|
__read_once_size(&(x), __u.__c, sizeof(x)); \
|
|
__u.__val; \
|
|
})
|
|
|
|
#define WRITE_ONCE(x, val) \
|
|
({ \
|
|
union { typeof(x) __val; char __c[1]; } __u = \
|
|
{ .__val = (val) }; \
|
|
__write_once_size(&(x), __u.__c, sizeof(x)); \
|
|
__u.__val; \
|
|
})
|
|
|
|
|
|
#ifndef __fallthrough
|
|
# define __fallthrough
|
|
#endif
|
|
|
|
#endif /* _TOOLS_LINUX_COMPILER_H */
|