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 # 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_STACK_VALIDATION
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_reachable(c) ({ \
121 asm volatile(__stringify_label(c) ":\n\t" \
122 ".pushsection .discard.reachable\n\t" \
123 ".long " __stringify_label(c) "b - .\n\t" \
124 ".popsection\n\t" : : "i" (c)); \
125 })
126 #define annotate_reachable() __annotate_reachable(__COUNTER__)
127
128 #define __annotate_unreachable(c) ({ \
129 asm volatile(__stringify_label(c) ":\n\t" \
130 ".pushsection .discard.unreachable\n\t" \
131 ".long " __stringify_label(c) "b - .\n\t" \
132 ".popsection\n\t" : : "i" (c)); \
133 })
134 #define annotate_unreachable() __annotate_unreachable(__COUNTER__)
135
136 #define ASM_UNREACHABLE \
137 "999:\n\t" \
138 ".pushsection .discard.unreachable\n\t" \
139 ".long 999b - .\n\t" \
140 ".popsection\n\t"
141
142 /* Annotate a C jump table to allow objtool to follow the code flow */
143 #define __annotate_jump_table __section(".rodata..c_jump_table")
144
145 #else
146 #define annotate_reachable()
147 #define annotate_unreachable()
148 #define __annotate_jump_table
149 #endif
150
151 #ifndef ASM_UNREACHABLE
152 # define ASM_UNREACHABLE
153 #endif
154 #ifndef unreachable
155 # define unreachable() do { \
156 annotate_unreachable(); \
157 __builtin_unreachable(); \
158 } while (0)
159 #endif
160
161 /*
162 * KENTRY - kernel entry point
163 * This can be used to annotate symbols (functions or data) that are used
164 * without their linker symbol being referenced explicitly. For example,
165 * interrupt vector handlers, or functions in the kernel image that are found
166 * programatically.
167 *
168 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
169 * are handled in their own way (with KEEP() in linker scripts).
170 *
171 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
172 * linker script. For example an architecture could KEEP() its entire
173 * boot/exception vector code rather than annotate each function and data.
174 */
175 #ifndef KENTRY
176 # define KENTRY(sym) \
177 extern typeof(sym) sym; \
178 static const unsigned long __kentry_##sym \
179 __used \
180 __attribute__((__section__("___kentry+" #sym))) \
181 = (unsigned long)&sym;
182 #endif
183
184 #ifndef RELOC_HIDE
185 # define RELOC_HIDE(ptr, off) \
186 ({ unsigned long __ptr; \
187 __ptr = (unsigned long) (ptr); \
188 (typeof(ptr)) (__ptr + (off)); })
189 #endif
190
191 #define absolute_pointer(val) RELOC_HIDE((void *)(val), 0)
192
193 #ifndef OPTIMIZER_HIDE_VAR
194 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
195 #define OPTIMIZER_HIDE_VAR(var) \
196 __asm__ ("" : "=r" (var) : "0" (var))
197 #endif
198
199 /* Not-quite-unique ID. */
200 #ifndef __UNIQUE_ID
201 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
202 #endif
203
204 /**
205 * data_race - mark an expression as containing intentional data races
206 *
207 * This data_race() macro is useful for situations in which data races
208 * should be forgiven. One example is diagnostic code that accesses
209 * shared variables but is not a part of the core synchronization design.
210 *
211 * This macro *does not* affect normal code generation, but is a hint
212 * to tooling that data races here are to be ignored.
213 */
214 #define data_race(expr) \
215 ({ \
216 __unqual_scalar_typeof(({ expr; })) __v = ({ \
217 __kcsan_disable_current(); \
218 expr; \
219 }); \
220 __kcsan_enable_current(); \
221 __v; \
222 })
223
224 /*
225 * With CONFIG_CFI_CLANG, the compiler replaces function addresses in
226 * instrumented C code with jump table addresses. Architectures that
227 * support CFI can define this macro to return the actual function address
228 * when needed.
229 */
230 #ifndef function_nocfi
231 #define function_nocfi(x) (x)
232 #endif
233
234 #endif /* __KERNEL__ */
235
236 /*
237 * Force the compiler to emit 'sym' as a symbol, so that we can reference
238 * it from inline assembler. Necessary in case 'sym' could be inlined
239 * otherwise, or eliminated entirely due to lack of references that are
240 * visible to the compiler.
241 */
242 #define __ADDRESSABLE(sym) \
243 static void * __section(".discard.addressable") __used \
244 __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)&sym;
245
246 /**
247 * offset_to_ptr - convert a relative memory offset to an absolute pointer
248 * @off: the address of the 32-bit offset value
249 */
offset_to_ptr(const int * off)250 static inline void *offset_to_ptr(const int *off)
251 {
252 return (void *)((unsigned long)off + *off);
253 }
254
255 #endif /* __ASSEMBLY__ */
256
257 /* &a[0] degrades to a pointer: a different type from an array */
258 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
259
260 /*
261 * This is needed in functions which generate the stack canary, see
262 * arch/x86/kernel/smpboot.c::start_secondary() for an example.
263 */
264 #define prevent_tail_call_optimization() mb()
265
266 #include <asm/rwonce.h>
267
268 #endif /* __LINUX_COMPILER_H */
269