/* SPDX-License-Identifier: GPL-2.0 */ #ifndef __LINUX_COMPILER_H #define __LINUX_COMPILER_H #include <linux/compiler_types.h> #ifndef __ASSEMBLY__ #ifdef __KERNEL__ /* * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code * to disable branch tracing on a per file basis. */ void ftrace_likely_update(struct ftrace_likely_data *f, int val, int expect, int is_constant); #if defined(CONFIG_TRACE_BRANCH_PROFILING) \ && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__) #define likely_notrace … #define unlikely_notrace … #define __branch_check__ … /* * Using __builtin_constant_p(x) to ignore cases where the return * value is always the same. This idea is taken from a similar patch * written by Daniel Walker. */ # ifndef likely #define likely … # endif # ifndef unlikely #define unlikely … # endif #ifdef CONFIG_PROFILE_ALL_BRANCHES /* * "Define 'is'", Bill Clinton * "Define 'if'", Steven Rostedt */ #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) ) #define __trace_if_var … #define __trace_if_value … #endif /* CONFIG_PROFILE_ALL_BRANCHES */ #else #define likely … #define unlikely … #define likely_notrace … #define unlikely_notrace … #endif /* Optimization barrier */ #ifndef barrier /* The "volatile" is due to gcc bugs */ #define barrier … #endif #ifndef barrier_data /* * This version is i.e. to prevent dead stores elimination on @ptr * where gcc and llvm may behave differently when otherwise using * normal barrier(): while gcc behavior gets along with a normal * barrier(), llvm needs an explicit input variable to be assumed * clobbered. The issue is as follows: while the inline asm might * access any memory it wants, the compiler could have fit all of * @ptr into memory registers instead, and since @ptr never escaped * from that, it proved that the inline asm wasn't touching any of * it. This version works well with both compilers, i.e. we're telling * the compiler that the inline asm absolutely may see the contents * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495 */ #define barrier_data … #endif /* workaround for GCC PR82365 if needed */ #ifndef barrier_before_unreachable #define barrier_before_unreachable … #endif /* Unreachable code */ #ifdef CONFIG_OBJTOOL /* * These macros help objtool understand GCC code flow for unreachable code. * The __COUNTER__ based labels are a hack to make each instance of the macros * unique, to convince GCC not to merge duplicate inline asm statements. */ #define __stringify_label … #define __annotate_reachable … #define annotate_reachable … #define __annotate_unreachable … #define annotate_unreachable … /* Annotate a C jump table to allow objtool to follow the code flow */ #define __annotate_jump_table … #else /* !CONFIG_OBJTOOL */ #define annotate_reachable … #define annotate_unreachable … #define __annotate_jump_table #endif /* CONFIG_OBJTOOL */ #ifndef unreachable #define unreachable … #endif /* * KENTRY - kernel entry point * This can be used to annotate symbols (functions or data) that are used * without their linker symbol being referenced explicitly. For example, * interrupt vector handlers, or functions in the kernel image that are found * programatically. * * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those * are handled in their own way (with KEEP() in linker scripts). * * KENTRY can be avoided if the symbols in question are marked as KEEP() in the * linker script. For example an architecture could KEEP() its entire * boot/exception vector code rather than annotate each function and data. */ #ifndef KENTRY #define KENTRY … #endif #ifndef RELOC_HIDE #define RELOC_HIDE … #endif #define absolute_pointer … #ifndef OPTIMIZER_HIDE_VAR /* Make the optimizer believe the variable can be manipulated arbitrarily. */ #define OPTIMIZER_HIDE_VAR … #endif #define __UNIQUE_ID … /** * data_race - mark an expression as containing intentional data races * * This data_race() macro is useful for situations in which data races * should be forgiven. One example is diagnostic code that accesses * shared variables but is not a part of the core synchronization design. * For example, if accesses to a given variable are protected by a lock, * except for diagnostic code, then the accesses under the lock should * be plain C-language accesses and those in the diagnostic code should * use data_race(). This way, KCSAN will complain if buggy lockless * accesses to that variable are introduced, even if the buggy accesses * are protected by READ_ONCE() or WRITE_ONCE(). * * This macro *does not* affect normal code generation, but is a hint * to tooling that data races here are to be ignored. If the access must * be atomic *and* KCSAN should ignore the access, use both data_race() * and READ_ONCE(), for example, data_race(READ_ONCE(x)). */ #define data_race … #endif /* __KERNEL__ */ /* * Force the compiler to emit 'sym' as a symbol, so that we can reference * it from inline assembler. Necessary in case 'sym' could be inlined * otherwise, or eliminated entirely due to lack of references that are * visible to the compiler. */ #define ___ADDRESSABLE … #define __ADDRESSABLE … /** * offset_to_ptr - convert a relative memory offset to an absolute pointer * @off: the address of the 32-bit offset value */ static inline void *offset_to_ptr(const int *off) { return (void *)((unsigned long)off + *off); } #endif /* __ASSEMBLY__ */ /* &a[0] degrades to a pointer: a different type from an array */ #define __must_be_array(a) … /* * This returns a constant expression while determining if an argument is * a constant expression, most importantly without evaluating the argument. * Glory to Martin Uecker <[email protected]> * * Details: * - sizeof() return an integer constant expression, and does not evaluate * the value of its operand; it only examines the type of its operand. * - The results of comparing two integer constant expressions is also * an integer constant expression. * - The first literal "8" isn't important. It could be any literal value. * - The second literal "8" is to avoid warnings about unaligned pointers; * this could otherwise just be "1". * - (long)(x) is used to avoid warnings about 64-bit types on 32-bit * architectures. * - The C Standard defines "null pointer constant", "(void *)0", as * distinct from other void pointers. * - If (x) is an integer constant expression, then the "* 0l" resolves * it into an integer constant expression of value 0. Since it is cast to * "void *", this makes the second operand a null pointer constant. * - If (x) is not an integer constant expression, then the second operand * resolves to a void pointer (but not a null pointer constant: the value * is not an integer constant 0). * - The conditional operator's third operand, "(int *)8", is an object * pointer (to type "int"). * - The behavior (including the return type) of the conditional operator * ("operand1 ? operand2 : operand3") depends on the kind of expressions * given for the second and third operands. This is the central mechanism * of the macro: * - When one operand is a null pointer constant (i.e. when x is an integer * constant expression) and the other is an object pointer (i.e. our * third operand), the conditional operator returns the type of the * object pointer operand (i.e. "int *"). Here, within the sizeof(), we * would then get: * sizeof(*((int *)(...)) == sizeof(int) == 4 * - When one operand is a void pointer (i.e. when x is not an integer * constant expression) and the other is an object pointer (i.e. our * third operand), the conditional operator returns a "void *" type. * Here, within the sizeof(), we would then get: * sizeof(*((void *)(...)) == sizeof(void) == 1 * - The equality comparison to "sizeof(int)" therefore depends on (x): * sizeof(int) == sizeof(int) (x) was a constant expression * sizeof(int) != sizeof(void) (x) was not a constant expression */ #define __is_constexpr(x) … /* * Whether 'type' is a signed type or an unsigned type. Supports scalar types, * bool and also pointer types. */ #define is_signed_type(type) … #define is_unsigned_type(type) … /* * Useful shorthand for "is this condition known at compile-time?" * * Note that the condition may involve non-constant values, * but the compiler may know enough about the details of the * values to determine that the condition is statically true. */ #define statically_true(x) … /* * This is needed in functions which generate the stack canary, see * arch/x86/kernel/smpboot.c::start_secondary() for an example. */ #define prevent_tail_call_optimization() … #include <asm/rwonce.h> #endif /* __LINUX_COMPILER_H */
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