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, ...) 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         __attribute__((__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 /**
 181  * data_race - mark an expression as containing intentional data races
 182  *
 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.
 186  *
 187  * This macro *does not* affect normal code generation, but is a hint
 188  * to tooling that data races here are to be ignored.
 189  */
 190 #define data_race(expr)                                                 \
 191 ({                                                                      \
 192         __unqual_scalar_typeof(({ expr; })) __v = ({                    \
 193                 __kcsan_disable_current();                              \
 194                 expr;                                                   \
 195         });                                                             \
 196         __kcsan_enable_current();                                       \
 197         __v;                                                            \
 198 })
 199
 200 #endif /* __KERNEL__ */
 201
 202 /*
 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.
 207  */
 208 #define __ADDRESSABLE(sym) \
 209         static void * __section(".discard.addressable") __used \
 210                 __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)&sym;
 211
 212 /**
 213  * offset_to_ptr - convert a relative memory offset to an absolute pointer
 214  * @off:        the address of the 32-bit offset value
 215  */
 216 static inline void *offset_to_ptr(const int *off)
 217 {
 218         return (void *)((unsigned long)off + *off);
 219 }
 220
 221 #endif /* __ASSEMBLY__ */
 222
 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]))
 225
 226 /*
 227  * This is needed in functions which generate the stack canary, see
 228  * arch/x86/kernel/smpboot.c::start_secondary() for an example.
 229  */
 230 #define prevent_tail_call_optimization()        mb()
 231
 232 #include <asm/rwonce.h>
 233
 234 #endif /* __LINUX_COMPILER_H */