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

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