| 1 |
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| 2 | #ifndef __LINUX_COMPILER_H
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| 3 | #define __LINUX_COMPILER_H
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| 4 |
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| 5 | #include <linux/compiler_types.h>
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| 6 |
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| 7 | #ifndef __ASSEMBLY__
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| 8 |
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| 9 | #ifdef __KERNEL__
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| 10 |
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| 11 | |
| 12 | * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
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| 13 | * to disable branch tracing on a per file basis.
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| 14 |
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| 15 | void ftrace_likely_update(struct ftrace_likely_data *f, int val,
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| 16 | int expect, int is_constant);
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| 17 | #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
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| 18 | && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
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| 19 | #define likely_notrace(x) __builtin_expect(!!(x), 1)
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| 20 | #define unlikely_notrace(x) __builtin_expect(!!(x), 0)
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| 21 |
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| 22 | #define __branch_check__(x, expect, is_constant) ({ \
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| 23 | long ______r; \
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| 24 | static struct ftrace_likely_data \
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| 25 | __aligned(4) \
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| 26 | __section("_ftrace_annotated_branch") \
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| 27 | ______f = { \
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| 28 | .data.func = __func__, \
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| 29 | .data.file = __FILE__, \
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| 30 | .data.line = __LINE__, \
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| 31 | }; \
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| 32 | ______r = __builtin_expect(!!(x), expect); \
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| 33 | ftrace_likely_update(&______f, ______r, \
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| 34 | expect, is_constant); \
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| 35 | ______r; \
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| 36 | })
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| 37 |
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| 38 | |
| 39 | * Using __builtin_constant_p(x) to ignore cases where the return
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| 40 | * value is always the same. This idea is taken from a similar patch
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| 41 | * written by Daniel Walker.
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| 42 |
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| 43 | # ifndef likely
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| 44 | # define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x)))
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| 45 | # endif
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| 46 | # ifndef unlikely
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| 47 | # define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
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| 48 | # endif
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| 49 |
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| 50 | #ifdef CONFIG_PROFILE_ALL_BRANCHES
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| 51 | |
| 52 | * "Define 'is'", Bill Clinton
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| 53 | * "Define 'if'", Steven Rostedt
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| 54 |
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| 55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
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| 56 |
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| 57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
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| 58 |
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| 59 | #define __trace_if_value(cond) ({ \
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| 60 | static struct ftrace_branch_data \
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| 61 | __aligned(4) \
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| 62 | __section("_ftrace_branch") \
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| 63 | __if_trace = { \
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| 64 | .func = __func__, \
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| 65 | .file = __FILE__, \
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| 66 | .line = __LINE__, \
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| 67 | }; \
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| 68 | (cond) ? \
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| 69 | (__if_trace.miss_hit[1]++,1) : \
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| 70 | (__if_trace.miss_hit[0]++,0); \
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| 71 | })
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| 72 |
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| 73 | #endif
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| 74 |
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| 75 | #else
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| 76 | # define likely(x) __builtin_expect(!!(x), 1)
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| 77 | # define unlikely(x) __builtin_expect(!!(x), 0)
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| 78 | # define likely_notrace(x) likely(x)
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| 79 | # define unlikely_notrace(x) unlikely(x)
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| 80 | #endif
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| 81 |
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| 82 |
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| 83 | #ifndef barrier
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| 84 |
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| 85 | # define barrier() __asm__ __volatile__("": : :"memory")
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| 86 | #endif
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| 87 |
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| 88 | #ifndef barrier_data
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| 89 | |
| 90 | * This version is i.e. to prevent dead stores elimination on @ptr
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| 91 | * where gcc and llvm may behave differently when otherwise using
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| 92 | * normal barrier(): while gcc behavior gets along with a normal
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| 93 | * barrier(), llvm needs an explicit input variable to be assumed
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| 94 | * clobbered. The issue is as follows: while the inline asm might
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| 95 | * access any memory it wants, the compiler could have fit all of
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| 96 | * @ptr into memory registers instead, and since @ptr never escaped
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| 97 | * from that, it proved that the inline asm wasn't touching any of
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| 98 | * it. This version works well with both compilers, i.e. we're telling
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| 99 | * the compiler that the inline asm absolutely may see the contents
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| 100 | * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
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| 101 |
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| 102 | # define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
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| 103 | #endif
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| 104 |
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| 105 |
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| 106 | #ifndef barrier_before_unreachable
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| 107 | # define barrier_before_unreachable() do { } while (0)
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| 108 | #endif
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| 109 |
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| 110 |
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| 111 | #ifdef CONFIG_OBJTOOL
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| 112 |
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| 113 | #define __annotate_jump_table __section(".data.rel.ro.c_jump_table")
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| 114 | #else
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| 115 | #define __annotate_jump_table
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| 116 | #endif
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| 117 |
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| 118 | |
| 119 | * Mark a position in code as unreachable. This can be used to
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| 120 | * suppress control flow warnings after asm blocks that transfer
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| 121 | * control elsewhere.
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| 122 |
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| 123 | #define unreachable() do { \
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| 124 | barrier_before_unreachable(); \
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| 125 | __builtin_unreachable(); \
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| 126 | } while (0)
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| 127 |
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| 128 | |
| 129 | * KENTRY - kernel entry point
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| 130 | * This can be used to annotate symbols (functions or data) that are used
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| 131 | * without their linker symbol being referenced explicitly. For example,
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| 132 | * interrupt vector handlers, or functions in the kernel image that are found
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| 133 | * programatically.
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| 134 | *
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| 135 | * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
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| 136 | * are handled in their own way (with KEEP() in linker scripts).
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| 137 | *
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| 138 | * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
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| 139 | * linker script. For example an architecture could KEEP() its entire
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| 140 | * boot/exception vector code rather than annotate each function and data.
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| 141 |
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| 142 | #ifndef KENTRY
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| 143 | # define KENTRY(sym) \
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| 144 | extern typeof(sym) sym; \
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| 145 | static const unsigned long __kentry_##sym \
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| 146 | __used \
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| 147 | __attribute__((__section__("___kentry+" #sym))) \
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| 148 | = (unsigned long)&sym;
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| 149 | #endif
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| 150 |
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| 151 | #ifndef RELOC_HIDE
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| 152 | # define RELOC_HIDE(ptr, off) ((typeof(ptr))((unsigned long)(ptr) + (off)))
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| 153 | #endif
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| 154 |
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| 155 | #define absolute_pointer(val) RELOC_HIDE((void *)(val), 0)
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| 156 |
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| 157 | #ifndef OPTIMIZER_HIDE_VAR
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| 158 |
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| 159 | #define OPTIMIZER_HIDE_VAR(var) \
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| 160 | __asm__ ("" : "=r" (var) : "0" (var))
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| 161 | #endif
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| 162 |
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| 163 |
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| 164 | #define __UNIQUE_ID(name) \
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| 165 | __PASTE(__UNIQUE_ID_, \
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| 166 | __PASTE(name, \
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| 167 | __PASTE(_, __COUNTER__)))
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| 168 |
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| 169 | |
| 170 | * data_race - mark an expression as containing intentional data races
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| 171 | *
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| 172 | * This data_race() macro is useful for situations in which data races
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| 173 | * should be forgiven. One example is diagnostic code that accesses
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| 174 | * shared variables but is not a part of the core synchronization design.
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| 175 | * For example, if accesses to a given variable are protected by a lock,
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| 176 | * except for diagnostic code, then the accesses under the lock should
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| 177 | * be plain C-language accesses and those in the diagnostic code should
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| 178 | * use data_race(). This way, KCSAN will complain if buggy lockless
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| 179 | * accesses to that variable are introduced, even if the buggy accesses
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| 180 | * are protected by READ_ONCE() or WRITE_ONCE().
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| 181 | *
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| 182 | * This macro *does not* affect normal code generation, but is a hint
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| 183 | * to tooling that data races here are to be ignored. If the access must
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| 184 | * be atomic *and* KCSAN should ignore the access, use both data_race()
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| 185 | * and READ_ONCE(), for example, data_race(READ_ONCE(x)).
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| 186 |
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| 187 | #define data_race(expr) \
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| 188 | ({ \
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| 189 | __kcsan_disable_current(); \
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| 190 | disable_context_analysis(); \
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| 191 | auto __v = (expr); \
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| 192 | enable_context_analysis(); \
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| 193 | __kcsan_enable_current(); \
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| 194 | __v; \
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| 195 | })
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| 196 |
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| 197 | #ifdef __CHECKER__
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| 198 | #define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) (0)
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| 199 | #else
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| 200 | #define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) ((int)sizeof(struct {_Static_assert(!(e), msg);}))
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| 201 | #endif
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| 202 |
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| 203 |
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| 204 | #define __is_array(a) (!__same_type((a), &(a)[0]))
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| 205 | #define __must_be_array(a) __BUILD_BUG_ON_ZERO_MSG(!__is_array(a), \
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| 206 | "must be array")
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| 207 |
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| 208 | #define __is_byte_array(a) (__is_array(a) && sizeof((a)[0]) == 1)
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| 209 | #define __must_be_byte_array(a) __BUILD_BUG_ON_ZERO_MSG(!__is_byte_array(a), \
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| 210 | "must be byte array")
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| 211 |
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| 212 | |
| 213 | * If the "nonstring" attribute isn't available, we have to return true
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| 214 | * so the __must_*() checks pass when "nonstring" isn't supported.
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| 215 |
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| 216 | #if __has_attribute(__nonstring__) && defined(__annotated)
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| 217 | #define __is_cstr(a) (!__annotated(a, nonstring))
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| 218 | #define __is_noncstr(a) (__annotated(a, nonstring))
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| 219 | #else
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| 220 | #define __is_cstr(a) (true)
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| 221 | #define __is_noncstr(a) (true)
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| 222 | #endif
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| 223 |
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| 224 |
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| 225 | #define __must_be_cstr(p) \
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| 226 | __BUILD_BUG_ON_ZERO_MSG(!__is_cstr(p), \
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| 227 | "must be C-string (NUL-terminated)")
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| 228 | #define __must_be_noncstr(p) \
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| 229 | __BUILD_BUG_ON_ZERO_MSG(!__is_noncstr(p), \
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| 230 | "must be non-C-string (not NUL-terminated)")
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| 231 |
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| 232 | |
| 233 | * Define TYPEOF_UNQUAL() to use __typeof_unqual__() as typeof
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| 234 | * operator when available, to return an unqualified type of the exp.
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| 235 |
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| 236 | #if defined(USE_TYPEOF_UNQUAL)
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| 237 | # define TYPEOF_UNQUAL(exp) __typeof_unqual__(exp)
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| 238 | #else
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| 239 | # define TYPEOF_UNQUAL(exp) __typeof__(exp)
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| 240 | #endif
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| 241 |
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| 242 | #endif
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| 243 |
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| 244 | #if defined(CONFIG_CFI) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO)
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| 245 | |
| 246 | * Force a reference to the external symbol so the compiler generates
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| 247 | * __kcfi_typid.
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| 248 |
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| 249 | #define KCFI_REFERENCE(sym) __ADDRESSABLE(sym)
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| 250 | #else
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| 251 | #define KCFI_REFERENCE(sym)
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| 252 | #endif
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| 253 |
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| 254 | |
| 255 | * offset_to_ptr - convert a relative memory offset to an absolute pointer
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| 256 | * @off: the address of the 32-bit offset value
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| 257 |
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| 258 | static inline void *offset_to_ptr(const int *off)
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| 259 | {
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| 260 | return (void *)((unsigned long)off + *off);
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| 261 | }
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| 262 |
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| 263 | #endif
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| 264 |
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| 265 | |
| 266 | * Force the compiler to emit 'sym' as a symbol, so that we can reference
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| 267 | * it from inline assembler. Necessary in case 'sym' could be inlined
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| 268 | * otherwise, or eliminated entirely due to lack of references that are
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| 269 | * visible to the compiler.
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| 270 |
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| 271 | #define ___ADDRESSABLE(sym, __attrs) \
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| 272 | static void * __used __attrs \
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| 273 | __UNIQUE_ID(__PASTE(addressable_, sym)) = (void *)(uintptr_t)&sym;
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| 274 |
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| 275 | #define __ADDRESSABLE(sym) \
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| 276 | ___ADDRESSABLE(sym, __section(".discard.addressable"))
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| 277 |
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| 278 | |
| 279 | * This returns a constant expression while determining if an argument is
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| 280 | * a constant expression, most importantly without evaluating the argument.
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| 281 | * Glory to Martin Uecker <[email protected]>
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| 282 | *
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| 283 | * Details:
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| 284 | * - sizeof() return an integer constant expression, and does not evaluate
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| 285 | * the value of its operand; it only examines the type of its operand.
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| 286 | * - The results of comparing two integer constant expressions is also
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| 287 | * an integer constant expression.
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| 288 | * - The first literal "8" isn't important. It could be any literal value.
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| 289 | * - The second literal "8" is to avoid warnings about unaligned pointers;
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| 290 | * this could otherwise just be "1".
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| 291 | * - (long)(x) is used to avoid warnings about 64-bit types on 32-bit
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| 292 | * architectures.
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| 293 | * - The C Standard defines "null pointer constant", "(void *)0", as
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| 294 | * distinct from other void pointers.
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| 295 | * - If (x) is an integer constant expression, then the "* 0l" resolves
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| 296 | * it into an integer constant expression of value 0. Since it is cast to
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| 297 | * "void *", this makes the second operand a null pointer constant.
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| 298 | * - If (x) is not an integer constant expression, then the second operand
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| 299 | * resolves to a void pointer (but not a null pointer constant: the value
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| 300 | * is not an integer constant 0).
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| 301 | * - The conditional operator's third operand, "(int *)8", is an object
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| 302 | * pointer (to type "int").
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| 303 | * - The behavior (including the return type) of the conditional operator
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| 304 | * ("operand1 ? operand2 : operand3") depends on the kind of expressions
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| 305 | * given for the second and third operands. This is the central mechanism
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| 306 | * of the macro:
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| 307 | * - When one operand is a null pointer constant (i.e. when x is an integer
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| 308 | * constant expression) and the other is an object pointer (i.e. our
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| 309 | * third operand), the conditional operator returns the type of the
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| 310 | * object pointer operand (i.e. "int *"). Here, within the sizeof(), we
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| 311 | * would then get:
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| 312 | * sizeof(*((int *)(...)) == sizeof(int) == 4
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| 313 | * - When one operand is a void pointer (i.e. when x is not an integer
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| 314 | * constant expression) and the other is an object pointer (i.e. our
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| 315 | * third operand), the conditional operator returns a "void *" type.
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| 316 | * Here, within the sizeof(), we would then get:
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| 317 | * sizeof(*((void *)(...)) == sizeof(void) == 1
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| 318 | * - The equality comparison to "sizeof(int)" therefore depends on (x):
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| 319 | * sizeof(int) == sizeof(int) (x) was a constant expression
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| 320 | * sizeof(int) != sizeof(void) (x) was not a constant expression
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| 321 |
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| 322 | #define __is_constexpr(x) \
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| 323 | (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
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| 324 |
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| 325 | |
| 326 | * Whether 'type' is a signed type or an unsigned type. Supports scalar types,
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| 327 | * bool and also pointer types.
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| 328 |
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| 329 | #define is_signed_type(type) (((type)(-1)) < (__force type)1)
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| 330 | #define is_unsigned_type(type) (!is_signed_type(type))
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| 331 |
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| 332 | |
| 333 | * Useful shorthand for "is this condition known at compile-time?"
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| 334 | *
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| 335 | * Note that the condition may involve non-constant values,
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| 336 | * but the compiler may know enough about the details of the
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| 337 | * values to determine that the condition is statically true.
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| 338 |
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| 339 | #define statically_true(x) (__builtin_constant_p(x) && (x))
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| 340 |
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| 341 | |
| 342 | * Similar to statically_true() but produces a constant expression
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| 343 | *
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| 344 | * To be used in conjunction with macros, such as BUILD_BUG_ON_ZERO(),
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| 345 | * which require their input to be a constant expression and for which
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| 346 | * statically_true() would otherwise fail.
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| 347 | *
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| 348 | * This is a trade-off: const_true() requires all its operands to be
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| 349 | * compile time constants. Else, it would always returns false even on
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| 350 | * the most trivial cases like:
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| 351 | *
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| 352 | * true || non_const_var
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| 353 | *
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| 354 | * On the opposite, statically_true() is able to fold more complex
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| 355 | * tautologies and will return true on expressions such as:
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| 356 | *
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| 357 | * !(non_const_var * 8 % 4)
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| 358 | *
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| 359 | * For the general case, statically_true() is better.
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| 360 |
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| 361 | #define const_true(x) __builtin_choose_expr(__is_constexpr(x), x, false)
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| 362 |
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| 363 | |
| 364 | * This is needed in functions which generate the stack canary, see
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| 365 | * arch/x86/kernel/smpboot.c::start_secondary() for an example.
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| 366 |
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| 367 | #define prevent_tail_call_optimization() mb()
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| 368 |
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| 369 | #include <asm/rwonce.h>
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| 370 |
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| 371 | #endif
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