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__)
17 void 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 #endif
80
81 /* Optimization barrier */
82 #ifndef barrier
83 /* The "volatile" is due to gcc bugs */
84 # define barrier() __asm__ __volatile__("": : :"memory")
85 #endif
86
87 #ifndef barrier_data
88 /*
89 * This version is i.e. to prevent dead stores elimination on @ptr
90 * where gcc and llvm may behave differently when otherwise using
91 * normal barrier(): while gcc behavior gets along with a normal
92 * barrier(), llvm needs an explicit input variable to be assumed
93 * clobbered. The issue is as follows: while the inline asm might
94 * access any memory it wants, the compiler could have fit all of
95 * @ptr into memory registers instead, and since @ptr never escaped
96 * from that, it proved that the inline asm wasn't touching any of
97 * it. This version works well with both compilers, i.e. we're telling
98 * the compiler that the inline asm absolutely may see the contents
99 * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
100 */
101 # define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
102 #endif
103
104 /* workaround for GCC PR82365 if needed */
105 #ifndef barrier_before_unreachable
106 # define barrier_before_unreachable() do { } while (0)
107 #endif
108
109 /* Unreachable code */
110 #ifdef CONFIG_STACK_VALIDATION
111 /*
112 * These macros help objtool understand GCC code flow for unreachable code.
113 * The __COUNTER__ based labels are a hack to make each instance of the macros
114 * unique, to convince GCC not to merge duplicate inline asm statements.
115 */
116 #define annotate_reachable() ({ \
117 asm volatile("%c0:\n\t" \
118 ".pushsection .discard.reachable\n\t" \
119 ".long %c0b - .\n\t" \
120 ".popsection\n\t" : : "i" (__COUNTER__)); \
121 })
122 #define annotate_unreachable() ({ \
123 asm volatile("%c0:\n\t" \
124 ".pushsection .discard.unreachable\n\t" \
125 ".long %c0b - .\n\t" \
126 ".popsection\n\t" : : "i" (__COUNTER__)); \
127 })
128 #define ASM_UNREACHABLE \
129 "999:\n\t" \
130 ".pushsection .discard.unreachable\n\t" \
131 ".long 999b - .\n\t" \
132 ".popsection\n\t"
133
134 /* Annotate a C jump table to allow objtool to follow the code flow */
135 #define __annotate_jump_table __section(".rodata..c_jump_table")
136
137 #else
138 #define annotate_reachable()
139 #define annotate_unreachable()
140 #define __annotate_jump_table
141 #endif
142
143 #ifndef ASM_UNREACHABLE
144 # define ASM_UNREACHABLE
145 #endif
146 #ifndef unreachable
147 # define unreachable() do { \
148 annotate_unreachable(); \
149 __builtin_unreachable(); \
150 } while (0)
151 #endif
152
153 /*
154 * KENTRY - kernel entry point
155 * This can be used to annotate symbols (functions or data) that are used
156 * without their linker symbol being referenced explicitly. For example,
157 * interrupt vector handlers, or functions in the kernel image that are found
158 * programatically.
159 *
160 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
161 * are handled in their own way (with KEEP() in linker scripts).
162 *
163 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
164 * linker script. For example an architecture could KEEP() its entire
165 * boot/exception vector code rather than annotate each function and data.
166 */
167 #ifndef KENTRY
168 # define KENTRY(sym) \
169 extern typeof(sym) sym; \
170 static const unsigned long __kentry_##sym \
171 __used \
172 __attribute__((__section__("___kentry+" #sym))) \
173 = (unsigned long)&sym;
174 #endif
175
176 #ifndef RELOC_HIDE
177 # define RELOC_HIDE(ptr, off) \
178 ({ unsigned long __ptr; \
179 __ptr = (unsigned long) (ptr); \
180 (typeof(ptr)) (__ptr + (off)); })
181 #endif
182
183 #ifndef OPTIMIZER_HIDE_VAR
184 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
185 #define OPTIMIZER_HIDE_VAR(var) \
186 __asm__ ("" : "=r" (var) : "0" (var))
187 #endif
188
189 /* Not-quite-unique ID. */
190 #ifndef __UNIQUE_ID
191 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
192 #endif
193
194 /**
195 * data_race - mark an expression as containing intentional data races
196 *
197 * This data_race() macro is useful for situations in which data races
198 * should be forgiven. One example is diagnostic code that accesses
199 * shared variables but is not a part of the core synchronization design.
200 *
201 * This macro *does not* affect normal code generation, but is a hint
202 * to tooling that data races here are to be ignored.
203 */
204 #define data_race(expr) \
205 ({ \
206 __unqual_scalar_typeof(({ expr; })) __v = ({ \
207 __kcsan_disable_current(); \
208 expr; \
209 }); \
210 __kcsan_enable_current(); \
211 __v; \
212 })
213
214 #endif /* __KERNEL__ */
215
216 /*
217 * Force the compiler to emit 'sym' as a symbol, so that we can reference
218 * it from inline assembler. Necessary in case 'sym' could be inlined
219 * otherwise, or eliminated entirely due to lack of references that are
220 * visible to the compiler.
221 */
222 #define __ADDRESSABLE(sym) \
223 static void * __section(".discard.addressable") __used \
224 __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)&sym;
225
226 /**
227 * offset_to_ptr - convert a relative memory offset to an absolute pointer
228 * @off: the address of the 32-bit offset value
229 */
offset_to_ptr(const int * off)230 static inline void *offset_to_ptr(const int *off)
231 {
232 return (void *)((unsigned long)off + *off);
233 }
234
235 #endif /* __ASSEMBLY__ */
236
237 /* &a[0] degrades to a pointer: a different type from an array */
238 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
239
240 /*
241 * This is needed in functions which generate the stack canary, see
242 * arch/x86/kernel/smpboot.c::start_secondary() for an example.
243 */
244 #define prevent_tail_call_optimization() mb()
245
246 #include <asm/rwonce.h>
247
248 #endif /* __LINUX_COMPILER_H */
249
