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Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h new file mode 100644 index 0000000..2b3f735 --- /dev/null +++ b/include/linux/compiler.h @@ -0,0 +1,206 @@ +/* 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 + +#ifdef __OPTIMIZE__ +# define __compiletime_assert(condition, msg, prefix, suffix) \ + do { \ + extern void prefix ## suffix(void) __compiletime_error(msg); \ + if (!(condition)) \ + prefix ## suffix(); \ + } while (0) +#else +# define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0) +#endif + +#define _compiletime_assert(condition, msg, prefix, suffix) \ + __compiletime_assert(condition, msg, prefix, suffix) + +/** + * compiletime_assert - break build and emit msg if condition is false + * @condition: a compile-time constant condition to check + * @msg: a message to emit if condition is false + * + * In tradition of POSIX assert, this macro will break the build if the + * supplied condition is *false*, emitting the supplied error message if the + * compiler has support to do so. + */ +#define compiletime_assert(condition, msg) \ + _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) + +/* 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 +#ifndef __no_tail_call +#define __no_tail_call +#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 + +#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 + +/* Indirect macros required for expanded argument pasting, eg. __LINE__. */ +#define ___PASTE(a, b) a##b +#define __PASTE(a, b) ___PASTE(a, b) + +#endif /* _TOOLS_LINUX_COMPILER_H */ |