compiler-gcc: remove comment about gcc 4.5 from unreachable()
[muen/linux.git] / include / linux / compiler.h
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, ...) __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                         __aligned(4)                                    \
63                         __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 {             \
128         annotate_unreachable();         \
129         __builtin_unreachable();        \
130 } while (0)
131 #endif
132
133 /*
134  * KENTRY - kernel entry point
135  * This can be used to annotate symbols (functions or data) that are used
136  * without their linker symbol being referenced explicitly. For example,
137  * interrupt vector handlers, or functions in the kernel image that are found
138  * programatically.
139  *
140  * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
141  * are handled in their own way (with KEEP() in linker scripts).
142  *
143  * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
144  * linker script. For example an architecture could KEEP() its entire
145  * boot/exception vector code rather than annotate each function and data.
146  */
147 #ifndef KENTRY
148 # define KENTRY(sym)                                            \
149         extern typeof(sym) sym;                                 \
150         static const unsigned long __kentry_##sym               \
151         __used                                                  \
152         __section("___kentry" "+" #sym )                        \
153         = (unsigned long)&sym;
154 #endif
155
156 #ifndef RELOC_HIDE
157 # define RELOC_HIDE(ptr, off)                                   \
158   ({ unsigned long __ptr;                                       \
159      __ptr = (unsigned long) (ptr);                             \
160     (typeof(ptr)) (__ptr + (off)); })
161 #endif
162
163 #ifndef OPTIMIZER_HIDE_VAR
164 #define OPTIMIZER_HIDE_VAR(var) barrier()
165 #endif
166
167 /* Not-quite-unique ID. */
168 #ifndef __UNIQUE_ID
169 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
170 #endif
171
172 #include <uapi/linux/types.h>
173
174 #define __READ_ONCE_SIZE                                                \
175 ({                                                                      \
176         switch (size) {                                                 \
177         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;              \
178         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;            \
179         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;            \
180         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;            \
181         default:                                                        \
182                 barrier();                                              \
183                 __builtin_memcpy((void *)res, (const void *)p, size);   \
184                 barrier();                                              \
185         }                                                               \
186 })
187
188 static __always_inline
189 void __read_once_size(const volatile void *p, void *res, int size)
190 {
191         __READ_ONCE_SIZE;
192 }
193
194 #ifdef CONFIG_KASAN
195 /*
196  * We can't declare function 'inline' because __no_sanitize_address confilcts
197  * with inlining. Attempt to inline it may cause a build failure.
198  *      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
199  * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
200  */
201 # define __no_kasan_or_inline __no_sanitize_address __maybe_unused
202 #else
203 # define __no_kasan_or_inline __always_inline
204 #endif
205
206 static __no_kasan_or_inline
207 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
208 {
209         __READ_ONCE_SIZE;
210 }
211
212 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
213 {
214         switch (size) {
215         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
216         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
217         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
218         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
219         default:
220                 barrier();
221                 __builtin_memcpy((void *)p, (const void *)res, size);
222                 barrier();
223         }
224 }
225
226 /*
227  * Prevent the compiler from merging or refetching reads or writes. The
228  * compiler is also forbidden from reordering successive instances of
229  * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
230  * particular ordering. One way to make the compiler aware of ordering is to
231  * put the two invocations of READ_ONCE or WRITE_ONCE in different C
232  * statements.
233  *
234  * These two macros will also work on aggregate data types like structs or
235  * unions. If the size of the accessed data type exceeds the word size of
236  * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
237  * fall back to memcpy(). There's at least two memcpy()s: one for the
238  * __builtin_memcpy() and then one for the macro doing the copy of variable
239  * - '__u' allocated on the stack.
240  *
241  * Their two major use cases are: (1) Mediating communication between
242  * process-level code and irq/NMI handlers, all running on the same CPU,
243  * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
244  * mutilate accesses that either do not require ordering or that interact
245  * with an explicit memory barrier or atomic instruction that provides the
246  * required ordering.
247  */
248 #include <asm/barrier.h>
249 #include <linux/kasan-checks.h>
250
251 #define __READ_ONCE(x, check)                                           \
252 ({                                                                      \
253         union { typeof(x) __val; char __c[1]; } __u;                    \
254         if (check)                                                      \
255                 __read_once_size(&(x), __u.__c, sizeof(x));             \
256         else                                                            \
257                 __read_once_size_nocheck(&(x), __u.__c, sizeof(x));     \
258         smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
259         __u.__val;                                                      \
260 })
261 #define READ_ONCE(x) __READ_ONCE(x, 1)
262
263 /*
264  * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
265  * to hide memory access from KASAN.
266  */
267 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
268
269 static __no_kasan_or_inline
270 unsigned long read_word_at_a_time(const void *addr)
271 {
272         kasan_check_read(addr, 1);
273         return *(unsigned long *)addr;
274 }
275
276 #define WRITE_ONCE(x, val) \
277 ({                                                      \
278         union { typeof(x) __val; char __c[1]; } __u =   \
279                 { .__val = (__force typeof(x)) (val) }; \
280         __write_once_size(&(x), __u.__c, sizeof(x));    \
281         __u.__val;                                      \
282 })
283
284 #endif /* __KERNEL__ */
285
286 /*
287  * Force the compiler to emit 'sym' as a symbol, so that we can reference
288  * it from inline assembler. Necessary in case 'sym' could be inlined
289  * otherwise, or eliminated entirely due to lack of references that are
290  * visible to the compiler.
291  */
292 #define __ADDRESSABLE(sym) \
293         static void * __section(".discard.addressable") __used \
294                 __PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
295
296 /**
297  * offset_to_ptr - convert a relative memory offset to an absolute pointer
298  * @off:        the address of the 32-bit offset value
299  */
300 static inline void *offset_to_ptr(const int *off)
301 {
302         return (void *)((unsigned long)off + *off);
303 }
304
305 #endif /* __ASSEMBLY__ */
306
307 /* Compile time object size, -1 for unknown */
308 #ifndef __compiletime_object_size
309 # define __compiletime_object_size(obj) -1
310 #endif
311 #ifndef __compiletime_warning
312 # define __compiletime_warning(message)
313 #endif
314 #ifndef __compiletime_error
315 # define __compiletime_error(message)
316 /*
317  * Sparse complains of variable sized arrays due to the temporary variable in
318  * __compiletime_assert. Unfortunately we can't just expand it out to make
319  * sparse see a constant array size without breaking compiletime_assert on old
320  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
321  */
322 # ifndef __CHECKER__
323 #  define __compiletime_error_fallback(condition) \
324         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
325 # endif
326 #endif
327 #ifndef __compiletime_error_fallback
328 # define __compiletime_error_fallback(condition) do { } while (0)
329 #endif
330
331 #ifdef __OPTIMIZE__
332 # define __compiletime_assert(condition, msg, prefix, suffix)           \
333         do {                                                            \
334                 int __cond = !(condition);                              \
335                 extern void prefix ## suffix(void) __compiletime_error(msg); \
336                 if (__cond)                                             \
337                         prefix ## suffix();                             \
338                 __compiletime_error_fallback(__cond);                   \
339         } while (0)
340 #else
341 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
342 #endif
343
344 #define _compiletime_assert(condition, msg, prefix, suffix) \
345         __compiletime_assert(condition, msg, prefix, suffix)
346
347 /**
348  * compiletime_assert - break build and emit msg if condition is false
349  * @condition: a compile-time constant condition to check
350  * @msg:       a message to emit if condition is false
351  *
352  * In tradition of POSIX assert, this macro will break the build if the
353  * supplied condition is *false*, emitting the supplied error message if the
354  * compiler has support to do so.
355  */
356 #define compiletime_assert(condition, msg) \
357         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
358
359 #define compiletime_assert_atomic_type(t)                               \
360         compiletime_assert(__native_word(t),                            \
361                 "Need native word sized stores/loads for atomicity.")
362
363 /* &a[0] degrades to a pointer: a different type from an array */
364 #define __must_be_array(a)      BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
365
366 #endif /* __LINUX_COMPILER_H */