1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_COMPILER_H
3#define __LINUX_COMPILER_H
4
5#include <linux/compiler_types.h>
6
7#ifndef __ASSEMBLY__
8
9#ifdef __KERNEL__
10
11/*
12 * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
13 * to disable branch tracing on a per file basis.
14 */
15void ftrace_likely_update(struct ftrace_likely_data *f, int val,
16 int expect, int is_constant);
17#if defined(CONFIG_TRACE_BRANCH_PROFILING) \
18 && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
19#define likely_notrace(x) __builtin_expect(!!(x), 1)
20#define unlikely_notrace(x) __builtin_expect(!!(x), 0)
21
22#define __branch_check__(x, expect, is_constant) ({ \
23 long ______r; \
24 static struct ftrace_likely_data \
25 __aligned(4) \
26 __section("_ftrace_annotated_branch") \
27 ______f = { \
28 .data.func = __func__, \
29 .data.file = __FILE__, \
30 .data.line = __LINE__, \
31 }; \
32 ______r = __builtin_expect(!!(x), expect); \
33 ftrace_likely_update(&______f, ______r, \
34 expect, is_constant); \
35 ______r; \
36 })
37
38/*
39 * Using __builtin_constant_p(x) to ignore cases where the return
40 * value is always the same. This idea is taken from a similar patch
41 * written by Daniel Walker.
42 */
43# ifndef likely
44# define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x)))
45# endif
46# ifndef unlikely
47# define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
48# endif
49
50#ifdef CONFIG_PROFILE_ALL_BRANCHES
51/*
52 * "Define 'is'", Bill Clinton
53 * "Define 'if'", Steven Rostedt
54 */
55#define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
56
57#define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
58
59#define __trace_if_value(cond) ({ \
60 static struct ftrace_branch_data \
61 __aligned(4) \
62 __section("_ftrace_branch") \
63 __if_trace = { \
64 .func = __func__, \
65 .file = __FILE__, \
66 .line = __LINE__, \
67 }; \
68 (cond) ? \
69 (__if_trace.miss_hit[1]++,1) : \
70 (__if_trace.miss_hit[0]++,0); \
71})
72
73#endif /* CONFIG_PROFILE_ALL_BRANCHES */
74
75#else
76# define likely(x) __builtin_expect(!!(x), 1)
77# define unlikely(x) __builtin_expect(!!(x), 0)
78# define likely_notrace(x) likely(x)
79# define unlikely_notrace(x) unlikely(x)
80#endif
81
82/* Optimization barrier */
83#ifndef barrier
84/* The "volatile" is due to gcc bugs */
85# define barrier() __asm__ __volatile__("": : :"memory")
86#endif
87
88#ifndef barrier_data
89/*
90 * This version is i.e. to prevent dead stores elimination on @ptr
91 * where gcc and llvm may behave differently when otherwise using
92 * normal barrier(): while gcc behavior gets along with a normal
93 * barrier(), llvm needs an explicit input variable to be assumed
94 * clobbered. The issue is as follows: while the inline asm might
95 * access any memory it wants, the compiler could have fit all of
96 * @ptr into memory registers instead, and since @ptr never escaped
97 * from that, it proved that the inline asm wasn't touching any of
98 * it. This version works well with both compilers, i.e. we're telling
99 * the compiler that the inline asm absolutely may see the contents
100 * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
101 */
102# define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
103#endif
104
105/* workaround for GCC PR82365 if needed */
106#ifndef barrier_before_unreachable
107# define barrier_before_unreachable() do { } while (0)
108#endif
109
110/* Unreachable code */
111#ifdef CONFIG_OBJTOOL
112/*
113 * These macros help objtool understand GCC code flow for unreachable code.
114 * The __COUNTER__ based labels are a hack to make each instance of the macros
115 * unique, to convince GCC not to merge duplicate inline asm statements.
116 */
117#define __stringify_label(n) #n
118
119#define __annotate_unreachable(c) ({ \
120 asm volatile(__stringify_label(c) ":\n\t" \
121 ".pushsection .discard.unreachable\n\t" \
122 ".long " __stringify_label(c) "b - .\n\t" \
123 ".popsection\n\t" : : "i" (c)); \
124})
125#define annotate_unreachable() __annotate_unreachable(__COUNTER__)
126
127/* Annotate a C jump table to allow objtool to follow the code flow */
128#define __annotate_jump_table __section(".rodata..c_jump_table")
129
130#else /* !CONFIG_OBJTOOL */
131#define annotate_unreachable()
132#define __annotate_jump_table
133#endif /* CONFIG_OBJTOOL */
134
135#ifndef unreachable
136# define unreachable() do { \
137 annotate_unreachable(); \
138 __builtin_unreachable(); \
139} while (0)
140#endif
141
142/*
143 * KENTRY - kernel entry point
144 * This can be used to annotate symbols (functions or data) that are used
145 * without their linker symbol being referenced explicitly. For example,
146 * interrupt vector handlers, or functions in the kernel image that are found
147 * programatically.
148 *
149 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
150 * are handled in their own way (with KEEP() in linker scripts).
151 *
152 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
153 * linker script. For example an architecture could KEEP() its entire
154 * boot/exception vector code rather than annotate each function and data.
155 */
156#ifndef KENTRY
157# define KENTRY(sym) \
158 extern typeof(sym) sym; \
159 static const unsigned long __kentry_##sym \
160 __used \
161 __attribute__((__section__("___kentry+" #sym))) \
162 = (unsigned long)&sym;
163#endif
164
165#ifndef RELOC_HIDE
166# define RELOC_HIDE(ptr, off) \
167 ({ unsigned long __ptr; \
168 __ptr = (unsigned long) (ptr); \
169 (typeof(ptr)) (__ptr + (off)); })
170#endif
171
172#define absolute_pointer(val) RELOC_HIDE((void *)(val), 0)
173
174#ifndef OPTIMIZER_HIDE_VAR
175/* Make the optimizer believe the variable can be manipulated arbitrarily. */
176#define OPTIMIZER_HIDE_VAR(var) \
177 __asm__ ("" : "=r" (var) : "0" (var))
178#endif
179
180#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
181
182/**
183 * data_race - mark an expression as containing intentional data races
184 *
185 * This data_race() macro is useful for situations in which data races
186 * should be forgiven. One example is diagnostic code that accesses
187 * shared variables but is not a part of the core synchronization design.
188 *
189 * This macro *does not* affect normal code generation, but is a hint
190 * to tooling that data races here are to be ignored.
191 */
192#define data_race(expr) \
193({ \
194 __unqual_scalar_typeof(({ expr; })) __v = ({ \
195 __kcsan_disable_current(); \
196 expr; \
197 }); \
198 __kcsan_enable_current(); \
199 __v; \
200})
201
202#endif /* __KERNEL__ */
203
204/*
205 * Force the compiler to emit 'sym' as a symbol, so that we can reference
206 * it from inline assembler. Necessary in case 'sym' could be inlined
207 * otherwise, or eliminated entirely due to lack of references that are
208 * visible to the compiler.
209 */
210#define ___ADDRESSABLE(sym, __attrs) \
211 static void * __used __attrs \
212 __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)&sym;
213#define __ADDRESSABLE(sym) \
214 ___ADDRESSABLE(sym, __section(".discard.addressable"))
215
216/**
217 * offset_to_ptr - convert a relative memory offset to an absolute pointer
218 * @off: the address of the 32-bit offset value
219 */
220static inline void *offset_to_ptr(const int *off)
221{
222 return (void *)((unsigned long)off + *off);
223}
224
225#endif /* __ASSEMBLY__ */
226
227/* &a[0] degrades to a pointer: a different type from an array */
228#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
229
230/*
231 * This returns a constant expression while determining if an argument is
232 * a constant expression, most importantly without evaluating the argument.
233 * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
234 */
235#define __is_constexpr(x) \
236 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
237
238/*
239 * Whether 'type' is a signed type or an unsigned type. Supports scalar types,
240 * bool and also pointer types.
241 */
242#define is_signed_type(type) (((type)(-1)) < (__force type)1)
243#define is_unsigned_type(type) (!is_signed_type(type))
244
245/*
246 * This is needed in functions which generate the stack canary, see
247 * arch/x86/kernel/smpboot.c::start_secondary() for an example.
248 */
249#define prevent_tail_call_optimization() mb()
250
251#include <asm/rwonce.h>
252
253#endif /* __LINUX_COMPILER_H */
254

source code of linux/include/linux/compiler.h