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 # define barrier() __memory_barrier()
84 #endif
85
86 #ifndef barrier_data
87 # define barrier_data(ptr) barrier()
88 #endif
89
90 /* workaround for GCC PR82365 if needed */
91 #ifndef barrier_before_unreachable
92 # define barrier_before_unreachable() do { } while (0)
93 #endif
94
95 /* Unreachable code */
96 #ifdef CONFIG_STACK_VALIDATION
97 /*
98 * These macros help objtool understand GCC code flow for unreachable code.
99 * The __COUNTER__ based labels are a hack to make each instance of the macros
100 * unique, to convince GCC not to merge duplicate inline asm statements.
101 */
102 #define annotate_reachable() ({ \
103 asm volatile("%c0:\n\t" \
104 ".pushsection .discard.reachable\n\t" \
105 ".long %c0b - .\n\t" \
106 ".popsection\n\t" : : "i" (__COUNTER__)); \
107 })
108 #define annotate_unreachable() ({ \
109 asm volatile("%c0:\n\t" \
110 ".pushsection .discard.unreachable\n\t" \
111 ".long %c0b - .\n\t" \
112 ".popsection\n\t" : : "i" (__COUNTER__)); \
113 })
114 #define ASM_UNREACHABLE \
115 "999:\n\t" \
116 ".pushsection .discard.unreachable\n\t" \
117 ".long 999b - .\n\t" \
118 ".popsection\n\t"
119
120 /* Annotate a C jump table to allow objtool to follow the code flow */
121 #define __annotate_jump_table __section(.rodata..c_jump_table)
122
123 #else
124 #define annotate_reachable()
125 #define annotate_unreachable()
126 #define __annotate_jump_table
127 #endif
128
129 #ifndef ASM_UNREACHABLE
130 # define ASM_UNREACHABLE
131 #endif
132 #ifndef unreachable
133 # define unreachable() do { \
134 annotate_unreachable(); \
135 __builtin_unreachable(); \
136 } while (0)
137 #endif
138
139 /*
140 * KENTRY - kernel entry point
141 * This can be used to annotate symbols (functions or data) that are used
142 * without their linker symbol being referenced explicitly. For example,
143 * interrupt vector handlers, or functions in the kernel image that are found
144 * programatically.
145 *
146 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
147 * are handled in their own way (with KEEP() in linker scripts).
148 *
149 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
150 * linker script. For example an architecture could KEEP() its entire
151 * boot/exception vector code rather than annotate each function and data.
152 */
153 #ifndef KENTRY
154 # define KENTRY(sym) \
155 extern typeof(sym) sym; \
156 static const unsigned long __kentry_##sym \
157 __used \
158 __section("___kentry" "+" #sym ) \
159 = (unsigned long)&sym;
160 #endif
161
162 #ifndef RELOC_HIDE
163 # define RELOC_HIDE(ptr, off) \
164 ({ unsigned long __ptr; \
165 __ptr = (unsigned long) (ptr); \
166 (typeof(ptr)) (__ptr + (off)); })
167 #endif
168
169 #ifndef OPTIMIZER_HIDE_VAR
170 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
171 #define OPTIMIZER_HIDE_VAR(var) \
172 __asm__ ("" : "=r" (var) : "0" (var))
173 #endif
174
175 /* Not-quite-unique ID. */
176 #ifndef __UNIQUE_ID
177 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
178 #endif
179
180 #include <uapi/linux/types.h>
181
182 #define __READ_ONCE_SIZE \
183 ({ \
184 switch (size) { \
185 case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \
186 case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \
187 case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \
188 case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
189 default: \
190 barrier(); \
191 __builtin_memcpy((void *)res, (const void *)p, size); \
192 barrier(); \
193 } \
194 })
195
196 static __always_inline
197 void __read_once_size(const volatile void *p, void *res, int size)
198 {
199 __READ_ONCE_SIZE;
200 }
201
202 #ifdef CONFIG_KASAN
203 /*
204 * We can't declare function 'inline' because __no_sanitize_address confilcts
205 * with inlining. Attempt to inline it may cause a build failure.
206 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
207 * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
208 */
209 # define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused
210 #else
211 # define __no_kasan_or_inline __always_inline
212 #endif
213
214 static __no_kasan_or_inline
215 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
216 {
217 __READ_ONCE_SIZE;
218 }
219
220 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
221 {
222 switch (size) {
223 case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
224 case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
225 case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
226 case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
227 default:
228 barrier();
229 __builtin_memcpy((void *)p, (const void *)res, size);
230 barrier();
231 }
232 }
233
234 /*
235 * Prevent the compiler from merging or refetching reads or writes. The
236 * compiler is also forbidden from reordering successive instances of
237 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
238 * particular ordering. One way to make the compiler aware of ordering is to
239 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
240 * statements.
241 *
242 * These two macros will also work on aggregate data types like structs or
243 * unions. If the size of the accessed data type exceeds the word size of
244 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
245 * fall back to memcpy(). There's at least two memcpy()s: one for the
246 * __builtin_memcpy() and then one for the macro doing the copy of variable
247 * - '__u' allocated on the stack.
248 *
249 * Their two major use cases are: (1) Mediating communication between
250 * process-level code and irq/NMI handlers, all running on the same CPU,
251 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
252 * mutilate accesses that either do not require ordering or that interact
253 * with an explicit memory barrier or atomic instruction that provides the
254 * required ordering.
255 */
256 #include <asm/barrier.h>
257 #include <linux/kasan-checks.h>
258
259 #define __READ_ONCE(x, check) \
260 ({ \
261 union { typeof(x) __val; char __c[1]; } __u; \
262 if (check) \
263 __read_once_size(&(x), __u.__c, sizeof(x)); \
264 else \
265 __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
266 smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
267 __u.__val; \
268 })
269 #define READ_ONCE(x) __READ_ONCE(x, 1)
270
271 /*
272 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
273 * to hide memory access from KASAN.
274 */
275 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
276
277 static __no_kasan_or_inline
278 unsigned long read_word_at_a_time(const void *addr)
279 {
280 kasan_check_read(addr, 1);
281 return *(unsigned long *)addr;
282 }
283
284 #define WRITE_ONCE(x, val) \
285 ({ \
286 union { typeof(x) __val; char __c[1]; } __u = \
287 { .__val = (__force typeof(x)) (val) }; \
288 __write_once_size(&(x), __u.__c, sizeof(x)); \
289 __u.__val; \
290 })
291
292 #endif /* __KERNEL__ */
293
294 /*
295 * Force the compiler to emit 'sym' as a symbol, so that we can reference
296 * it from inline assembler. Necessary in case 'sym' could be inlined
297 * otherwise, or eliminated entirely due to lack of references that are
298 * visible to the compiler.
299 */
300 #define __ADDRESSABLE(sym) \
301 static void * __section(.discard.addressable) __used \
302 __PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
303
304 /**
305 * offset_to_ptr - convert a relative memory offset to an absolute pointer
306 * @off: the address of the 32-bit offset value
307 */
308 static inline void *offset_to_ptr(const int *off)
309 {
310 return (void *)((unsigned long)off + *off);
311 }
312
313 #endif /* __ASSEMBLY__ */
314
315 /* Compile time object size, -1 for unknown */
316 #ifndef __compiletime_object_size
317 # define __compiletime_object_size(obj) -1
318 #endif
319 #ifndef __compiletime_warning
320 # define __compiletime_warning(message)
321 #endif
322 #ifndef __compiletime_error
323 # define __compiletime_error(message)
324 #endif
325
326 #ifdef __OPTIMIZE__
327 # define __compiletime_assert(condition, msg, prefix, suffix) \
328 do { \
329 extern void prefix ## suffix(void) __compiletime_error(msg); \
330 if (!(condition)) \
331 prefix ## suffix(); \
332 } while (0)
333 #else
334 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
335 #endif
336
337 #define _compiletime_assert(condition, msg, prefix, suffix) \
338 __compiletime_assert(condition, msg, prefix, suffix)
339
340 /**
341 * compiletime_assert - break build and emit msg if condition is false
342 * @condition: a compile-time constant condition to check
343 * @msg: a message to emit if condition is false
344 *
345 * In tradition of POSIX assert, this macro will break the build if the
346 * supplied condition is *false*, emitting the supplied error message if the
347 * compiler has support to do so.
348 */
349 #define compiletime_assert(condition, msg) \
350 _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
351
352 #define compiletime_assert_atomic_type(t) \
353 compiletime_assert(__native_word(t), \
354 "Need native word sized stores/loads for atomicity.")
355
356 /* &a[0] degrades to a pointer: a different type from an array */
357 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
358
359 /*
360 * This is needed in functions which generate the stack canary, see
361 * arch/x86/kernel/smpboot.c::start_secondary() for an example.
362 */
363 #define prevent_tail_call_optimization() mb()
364
365 #endif /* __LINUX_COMPILER_H */