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 __attribute__((__aligned__(4))) \
27 __attribute__((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, ...) __trace_if( (cond , ## __VA_ARGS__) )
57 #define __trace_if(cond) \
58 if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
59 ({ \
60 int ______r; \
61 static struct ftrace_branch_data \
62 __attribute__((__aligned__(4))) \
63 __attribute__((section("_ftrace_branch"))) \
64 ______f = { \
65 .func = __func__, \
66 .file = __FILE__, \
67 .line = __LINE__, \
68 }; \
69 ______r = !!(cond); \
70 ______f.miss_hit[______r]++; \
71 ______r; \
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 #endif
79
80 /* Optimization barrier */
81 #ifndef barrier
82 # define barrier() __memory_barrier()
83 #endif
84
85 #ifndef barrier_data
86 # define barrier_data(ptr) barrier()
87 #endif
88
89 /* workaround for GCC PR82365 if needed */
90 #ifndef barrier_before_unreachable
91 # define barrier_before_unreachable() do { } while (0)
92 #endif
93
94 /* Unreachable code */
95 #ifdef CONFIG_STACK_VALIDATION
96 /*
97 * These macros help objtool understand GCC code flow for unreachable code.
98 * The __COUNTER__ based labels are a hack to make each instance of the macros
99 * unique, to convince GCC not to merge duplicate inline asm statements.
100 */
101 #define annotate_reachable() ({ \
102 asm volatile("%c0:\n\t" \
103 ".pushsection .discard.reachable\n\t" \
104 ".long %c0b - .\n\t" \
105 ".popsection\n\t" : : "i" (__COUNTER__)); \
106 })
107 #define annotate_unreachable() ({ \
108 asm volatile("%c0:\n\t" \
109 ".pushsection .discard.unreachable\n\t" \
110 ".long %c0b - .\n\t" \
111 ".popsection\n\t" : : "i" (__COUNTER__)); \
112 })
113 #define ASM_UNREACHABLE \
114 "999:\n\t" \
115 ".pushsection .discard.unreachable\n\t" \
116 ".long 999b - .\n\t" \
117 ".popsection\n\t"
118 #else
119 #define annotate_reachable()
120 #define annotate_unreachable()
121 #endif
122
123 #ifndef ASM_UNREACHABLE
124 # define ASM_UNREACHABLE
125 #endif
126 #ifndef unreachable
127 # define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
128 #endif
129
130 /*
131 * KENTRY - kernel entry point
132 * This can be used to annotate symbols (functions or data) that are used
133 * without their linker symbol being referenced explicitly. For example,
134 * interrupt vector handlers, or functions in the kernel image that are found
135 * programatically.
136 *
137 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
138 * are handled in their own way (with KEEP() in linker scripts).
139 *
140 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
141 * linker script. For example an architecture could KEEP() its entire
142 * boot/exception vector code rather than annotate each function and data.
143 */
144 #ifndef KENTRY
145 # define KENTRY(sym) \
146 extern typeof(sym) sym; \
147 static const unsigned long __kentry_##sym \
148 __used \
149 __attribute__((section("___kentry" "+" #sym ), used)) \
150 = (unsigned long)&sym;
151 #endif
152
153 #ifndef RELOC_HIDE
154 # define RELOC_HIDE(ptr, off) \
155 ({ unsigned long __ptr; \
156 __ptr = (unsigned long) (ptr); \
157 (typeof(ptr)) (__ptr + (off)); })
158 #endif
159
160 #ifndef OPTIMIZER_HIDE_VAR
161 #define OPTIMIZER_HIDE_VAR(var) barrier()
162 #endif
163
164 /* Not-quite-unique ID. */
165 #ifndef __UNIQUE_ID
166 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
167 #endif
168
169 #include <uapi/linux/types.h>
170
171 #define __READ_ONCE_SIZE \
172 ({ \
173 switch (size) { \
174 case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \
175 case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \
176 case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \
177 case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
178 default: \
179 barrier(); \
180 __builtin_memcpy((void *)res, (const void *)p, size); \
181 barrier(); \
182 } \
183 })
184
185 static __always_inline
__read_once_size(const volatile void * p,void * res,int size)186 void __read_once_size(const volatile void *p, void *res, int size)
187 {
188 __READ_ONCE_SIZE;
189 }
190
191 #ifdef CONFIG_KASAN
192 /*
193 * We can't declare function 'inline' because __no_sanitize_address confilcts
194 * with inlining. Attempt to inline it may cause a build failure.
195 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
196 * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
197 */
198 # define __no_kasan_or_inline __no_sanitize_address __maybe_unused
199 #else
200 # define __no_kasan_or_inline __always_inline
201 #endif
202
203 static __no_kasan_or_inline
__read_once_size_nocheck(const volatile void * p,void * res,int size)204 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
205 {
206 __READ_ONCE_SIZE;
207 }
208
__write_once_size(volatile void * p,void * res,int size)209 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
210 {
211 switch (size) {
212 case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
213 case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
214 case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
215 case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
216 default:
217 barrier();
218 __builtin_memcpy((void *)p, (const void *)res, size);
219 barrier();
220 }
221 }
222
223 /*
224 * Prevent the compiler from merging or refetching reads or writes. The
225 * compiler is also forbidden from reordering successive instances of
226 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
227 * particular ordering. One way to make the compiler aware of ordering is to
228 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
229 * statements.
230 *
231 * These two macros will also work on aggregate data types like structs or
232 * unions. If the size of the accessed data type exceeds the word size of
233 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
234 * fall back to memcpy(). There's at least two memcpy()s: one for the
235 * __builtin_memcpy() and then one for the macro doing the copy of variable
236 * - '__u' allocated on the stack.
237 *
238 * Their two major use cases are: (1) Mediating communication between
239 * process-level code and irq/NMI handlers, all running on the same CPU,
240 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
241 * mutilate accesses that either do not require ordering or that interact
242 * with an explicit memory barrier or atomic instruction that provides the
243 * required ordering.
244 */
245 #include <asm/barrier.h>
246 #include <linux/kasan-checks.h>
247
248 #define __READ_ONCE(x, check) \
249 ({ \
250 union { typeof(x) __val; char __c[1]; } __u; \
251 if (check) \
252 __read_once_size(&(x), __u.__c, sizeof(x)); \
253 else \
254 __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
255 smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
256 __u.__val; \
257 })
258 #define READ_ONCE(x) __READ_ONCE(x, 1)
259
260 /*
261 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
262 * to hide memory access from KASAN.
263 */
264 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
265
266 static __no_kasan_or_inline
read_word_at_a_time(const void * addr)267 unsigned long read_word_at_a_time(const void *addr)
268 {
269 kasan_check_read(addr, 1);
270 return *(unsigned long *)addr;
271 }
272
273 #define WRITE_ONCE(x, val) \
274 ({ \
275 union { typeof(x) __val; char __c[1]; } __u = \
276 { .__val = (__force typeof(x)) (val) }; \
277 __write_once_size(&(x), __u.__c, sizeof(x)); \
278 __u.__val; \
279 })
280
281 #endif /* __KERNEL__ */
282
283 /*
284 * Force the compiler to emit 'sym' as a symbol, so that we can reference
285 * it from inline assembler. Necessary in case 'sym' could be inlined
286 * otherwise, or eliminated entirely due to lack of references that are
287 * visible to the compiler.
288 */
289 #define __ADDRESSABLE(sym) \
290 static void * __attribute__((section(".discard.addressable"), used)) \
291 __PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
292
293 /**
294 * offset_to_ptr - convert a relative memory offset to an absolute pointer
295 * @off: the address of the 32-bit offset value
296 */
offset_to_ptr(const int * off)297 static inline void *offset_to_ptr(const int *off)
298 {
299 return (void *)((unsigned long)off + *off);
300 }
301
302 #endif /* __ASSEMBLY__ */
303
304 #ifndef __optimize
305 # define __optimize(level)
306 #endif
307
308 /* Compile time object size, -1 for unknown */
309 #ifndef __compiletime_object_size
310 # define __compiletime_object_size(obj) -1
311 #endif
312 #ifndef __compiletime_warning
313 # define __compiletime_warning(message)
314 #endif
315 #ifndef __compiletime_error
316 # define __compiletime_error(message)
317 /*
318 * Sparse complains of variable sized arrays due to the temporary variable in
319 * __compiletime_assert. Unfortunately we can't just expand it out to make
320 * sparse see a constant array size without breaking compiletime_assert on old
321 * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
322 */
323 # ifndef __CHECKER__
324 # define __compiletime_error_fallback(condition) \
325 do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
326 # endif
327 #endif
328 #ifndef __compiletime_error_fallback
329 # define __compiletime_error_fallback(condition) do { } while (0)
330 #endif
331
332 #ifdef __OPTIMIZE__
333 # define __compiletime_assert(condition, msg, prefix, suffix) \
334 do { \
335 int __cond = !(condition); \
336 extern void prefix ## suffix(void) __compiletime_error(msg); \
337 if (__cond) \
338 prefix ## suffix(); \
339 __compiletime_error_fallback(__cond); \
340 } while (0)
341 #else
342 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
343 #endif
344
345 #define _compiletime_assert(condition, msg, prefix, suffix) \
346 __compiletime_assert(condition, msg, prefix, suffix)
347
348 /**
349 * compiletime_assert - break build and emit msg if condition is false
350 * @condition: a compile-time constant condition to check
351 * @msg: a message to emit if condition is false
352 *
353 * In tradition of POSIX assert, this macro will break the build if the
354 * supplied condition is *false*, emitting the supplied error message if the
355 * compiler has support to do so.
356 */
357 #define compiletime_assert(condition, msg) \
358 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
359
360 #define compiletime_assert_atomic_type(t) \
361 compiletime_assert(__native_word(t), \
362 "Need native word sized stores/loads for atomicity.")
363
364 #endif /* __LINUX_COMPILER_H */
365
