1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_COMPILER_H
3 #define __LINUX_COMPILER_H
5 #include <linux/compiler_types.h>
12 * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
13 * to disable branch tracing on a per file basis.
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);
20 #define likely_notrace(x) __builtin_expect(!!(x), 1)
21 #define unlikely_notrace(x) __builtin_expect(!!(x), 0)
23 #define __branch_check__(x, expect, is_constant) ({ \
25 static struct ftrace_likely_data \
27 __section(_ftrace_annotated_branch) \
29 .data.func = __func__, \
30 .data.file = __FILE__, \
31 .data.line = __LINE__, \
33 ______r = __builtin_expect(!!(x), expect); \
34 ftrace_likely_update(&______f, ______r, \
35 expect, is_constant); \
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.
45 # define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x)))
48 # define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
51 #ifdef CONFIG_PROFILE_ALL_BRANCHES
53 * "Define 'is'", Bill Clinton
54 * "Define 'if'", Steven Rostedt
56 #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
58 #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
60 #define __trace_if_value(cond) ({ \
61 static struct ftrace_branch_data \
63 __section(_ftrace_branch) \
70 (__if_trace.miss_hit[1]++,1) : \
71 (__if_trace.miss_hit[0]++,0); \
74 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
77 # define likely(x) __builtin_expect(!!(x), 1)
78 # define unlikely(x) __builtin_expect(!!(x), 0)
81 /* Optimization barrier */
83 # define barrier() __memory_barrier()
87 # define barrier_data(ptr) barrier()
90 /* workaround for GCC PR82365 if needed */
91 #ifndef barrier_before_unreachable
92 # define barrier_before_unreachable() do { } while (0)
95 /* Unreachable code */
96 #ifdef CONFIG_STACK_VALIDATION
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.
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__)); \
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__)); \
114 #define ASM_UNREACHABLE \
116 ".pushsection .discard.unreachable\n\t" \
117 ".long 999b - .\n\t" \
120 /* Annotate a C jump table to allow objtool to follow the code flow */
121 #define __annotate_jump_table __section(.rodata..c_jump_table)
124 #define annotate_reachable()
125 #define annotate_unreachable()
126 #define __annotate_jump_table
129 #ifndef ASM_UNREACHABLE
130 # define ASM_UNREACHABLE
133 # define unreachable() do { \
134 annotate_unreachable(); \
135 __builtin_unreachable(); \
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
146 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
147 * are handled in their own way (with KEEP() in linker scripts).
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.
154 # define KENTRY(sym) \
155 extern typeof(sym) sym; \
156 static const unsigned long __kentry_##sym \
158 __attribute__((__section__("___kentry+" #sym))) \
159 = (unsigned long)&sym;
163 # define RELOC_HIDE(ptr, off) \
164 ({ unsigned long __ptr; \
165 __ptr = (unsigned long) (ptr); \
166 (typeof(ptr)) (__ptr + (off)); })
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))
175 /* Not-quite-unique ID. */
177 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
181 * data_race - mark an expression as containing intentional data races
183 * This data_race() macro is useful for situations in which data races
184 * should be forgiven. One example is diagnostic code that accesses
185 * shared variables but is not a part of the core synchronization design.
187 * This macro *does not* affect normal code generation, but is a hint
188 * to tooling that data races here are to be ignored.
190 #define data_race(expr) \
192 __unqual_scalar_typeof(({ expr; })) __v = ({ \
193 __kcsan_disable_current(); \
196 __kcsan_enable_current(); \
200 #endif /* __KERNEL__ */
203 * Force the compiler to emit 'sym' as a symbol, so that we can reference
204 * it from inline assembler. Necessary in case 'sym' could be inlined
205 * otherwise, or eliminated entirely due to lack of references that are
206 * visible to the compiler.
208 #define __ADDRESSABLE(sym) \
209 static void * __section(.discard.addressable) __used \
210 __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)&sym;
213 * offset_to_ptr - convert a relative memory offset to an absolute pointer
214 * @off: the address of the 32-bit offset value
216 static inline void *offset_to_ptr(const int *off)
218 return (void *)((unsigned long)off + *off);
221 #endif /* __ASSEMBLY__ */
223 /* &a[0] degrades to a pointer: a different type from an array */
224 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
227 * This is needed in functions which generate the stack canary, see
228 * arch/x86/kernel/smpboot.c::start_secondary() for an example.
230 #define prevent_tail_call_optimization() mb()
232 #include <asm/rwonce.h>
234 #endif /* __LINUX_COMPILER_H */