bcachefs-tools/include/linux/compiler.h

#ifndef _TOOLS_LINUX_COMPILER_H_
#define _TOOLS_LINUX_COMPILER_H_

/* Optimization barrier */
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")

#ifndef __always_inline
# define __always_inline	inline __attribute__((always_inline))
#endif

#ifndef __attribute_const__
#define __attribute_const__     __attribute__((__const__))
#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 noinline
#define noinline_for_stack noinline

#define __user
#define __kernel

#define __pure			__attribute__((pure))
#define __aligned(x)		__attribute__((aligned(x)))
#define __printf(a, b)		__attribute__((format(printf, a, b)))
#define __used			__attribute__((__used__))
#define __maybe_unused		__attribute__((unused))
#define __always_unused		__attribute__((unused))
#define __packed		__attribute__((__packed__))
#define __flatten		__attribute__((flatten))
#define __force
#define __nocast
#define __iomem
#define __chk_user_ptr(x) (void)0
#define __chk_io_ptr(x) (void)0
#define __builtin_warning(x, y...) (1)
#define __must_hold(x)
#define __acquires(x)
#define __releases(x)
#define __acquire(x) (void)0
#define __release(x) (void)0
#define __cond_lock(x,c) (c)
#define __percpu
#define __rcu
#define __sched
#define __init
#define __exit
#define __private
#define __must_check
#define __malloc
#define __weak			__attribute__((weak))
#define likely(x)		__builtin_expect(!!(x), 1)
#define unlikely(x)		__builtin_expect(!!(x), 0)
#define unreachable()		__builtin_unreachable()
#define __same_type(a, b)	__builtin_types_compatible_p(typeof(a), typeof(b))
#define fallthrough		__attribute__((__fallthrough__))
#define __noreturn		__attribute__((__noreturn__))

#ifndef __counted_by
#define __counted_by(nr)
#endif

#define ___PASTE(a,b) a##b
#define __PASTE(a,b) ___PASTE(a,b)
#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)

#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))

#define __initcall(x)	/* unimplemented */
#define __exitcall(x)	/* unimplemented */

#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, WRITE_ONCE and ACCESS_ONCE (see below), 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,
 * WRITE_ONCE or ACCESS_ONCE() in different C statements.
 *
 * In contrast to ACCESS_ONCE 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; __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; })

#define lockless_dereference(p) \
({ \
	typeof(p) _________p1 = READ_ONCE(p); \
	typeof(*(p)) *___typecheck_p __maybe_unused; \
	smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
	(_________p1); \
})

#define flush_cache_all()			do { } while (0)
#define flush_cache_mm(mm)			do { } while (0)
#define flush_cache_dup_mm(mm)			do { } while (0)
#define flush_cache_range(vma, start, end)	do { } while (0)
#define flush_cache_page(vma, vmaddr, pfn)	do { } while (0)
#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
#define flush_dcache_page(page)			do { } while (0)
#define flush_dcache_mmap_lock(mapping)		do { } while (0)
#define flush_dcache_mmap_unlock(mapping)	do { } while (0)
#define flush_icache_range(start, end)		do { } while (0)
#define flush_icache_page(vma,pg)		do { } while (0)
#define flush_icache_user_range(vma,pg,adr,len)	do { } while (0)
#define flush_cache_vmap(start, end)		do { } while (0)
#define flush_cache_vunmap(start, end)		do { } while (0)

#ifdef __x86_64
#define CONFIG_X86_64	y
#endif

#endif /* _TOOLS_LINUX_COMPILER_H */