/* 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(x) __builtin_expect(!!(x), 1) #define unlikely_notrace(x) __builtin_expect(!!(x), 0) #define __branch_check__(x, expect, is_constant) ({ \ long ______r; \ static struct ftrace_likely_data \ __aligned(4) \ __section("_ftrace_annotated_branch") \ ______f = { \ .data.func = __func__, \ .data.file = __FILE__, \ .data.line = __LINE__, \ }; \ ______r = __builtin_expect(!!(x), expect); \ ftrace_likely_update(&______f, ______r, \ expect, is_constant); \ ______r; \ }) /* * 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(x) (__branch_check__(x, 1, __builtin_constant_p(x))) # endif # ifndef unlikely # define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x))) # 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(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond)) #define __trace_if_value(cond) ({ \ static struct ftrace_branch_data \ __aligned(4) \ __section("_ftrace_branch") \ __if_trace = { \ .func = __func__, \ .file = __FILE__, \ .line = __LINE__, \ }; \ (cond) ? \ (__if_trace.miss_hit[1]++,1) : \ (__if_trace.miss_hit[0]++,0); \ }) #endif /* CONFIG_PROFILE_ALL_BRANCHES */ #else # define likely(x) __builtin_expect(!!(x), 1) # define unlikely(x) __builtin_expect(!!(x), 0) # define likely_notrace(x) likely(x) # define unlikely_notrace(x) unlikely(x) #endif /* Optimization barrier */ #ifndef barrier /* The "volatile" is due to gcc bugs */ # define barrier() __asm__ __volatile__("": : :"memory") #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(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory") #endif /* workaround for GCC PR82365 if needed */ #ifndef barrier_before_unreachable # define barrier_before_unreachable() do { } while (0) #endif /* Unreachable code */ #ifdef CONFIG_OBJTOOL /* Annotate a C jump table to allow objtool to follow the code flow */ #define __annotate_jump_table __section(".data.rel.ro.c_jump_table") #else /* !CONFIG_OBJTOOL */ #define __annotate_jump_table #endif /* CONFIG_OBJTOOL */ /* * Mark a position in code as unreachable. This can be used to * suppress control flow warnings after asm blocks that transfer * control elsewhere. */ #define unreachable() do { \ barrier_before_unreachable(); \ __builtin_unreachable(); \ } while (0) /* * 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(sym) \ extern typeof(sym) sym; \ static const unsigned long __kentry_##sym \ __used \ __attribute__((__section__("___kentry+" #sym))) \ = (unsigned long)&sym; #endif #ifndef RELOC_HIDE # define RELOC_HIDE(ptr, off) \ ({ unsigned long __ptr; \ __ptr = (unsigned long) (ptr); \ (typeof(ptr)) (__ptr + (off)); }) #endif #define absolute_pointer(val) RELOC_HIDE((void *)(val), 0) #ifndef OPTIMIZER_HIDE_VAR /* Make the optimizer believe the variable can be manipulated arbitrarily. */ #define OPTIMIZER_HIDE_VAR(var) \ __asm__ ("" : "=r" (var) : "0" (var)) #endif /* Format: __UNIQUE_ID_<name>_<__COUNTER__> */ #define __UNIQUE_ID(name) \ __PASTE(__UNIQUE_ID_, \ __PASTE(name, \ __PASTE(_, __COUNTER__))) /** * 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(expr) \ ({ \ __kcsan_disable_current(); \ disable_context_analysis(); \ auto __v = (expr); \ enable_context_analysis(); \ __kcsan_enable_current(); \ __v; \ }) #ifdef __CHECKER__ #define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) (0) #else /* __CHECKER__ */ #define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) ((int)sizeof(struct {_Static_assert(!(e), msg);})) #endif /* __CHECKER__ */ /* &a[0] degrades to a pointer: a different type from an array */ #define __is_array(a) (!__same_type((a), &(a)[0])) #define __must_be_array(a) __BUILD_BUG_ON_ZERO_MSG(!__is_array(a), \ "must be array") #define __is_byte_array(a) (__is_array(a) && sizeof((a)[0]) == 1) #define __must_be_byte_array(a) __BUILD_BUG_ON_ZERO_MSG(!__is_byte_array(a), \ "must be byte array") /* * If the "nonstring" attribute isn't available, we have to return true * so the __must_*() checks pass when "nonstring" isn't supported. */ #if __has_attribute(__nonstring__) && defined(__annotated) #define __is_cstr(a) (!__annotated(a, nonstring)) #define __is_noncstr(a) (__annotated(a, nonstring)) #else #define __is_cstr(a) (true) #define __is_noncstr(a) (true) #endif /* Require C Strings (i.e. NUL-terminated) lack the "nonstring" attribute. */ #define __must_be_cstr(p) \ __BUILD_BUG_ON_ZERO_MSG(!__is_cstr(p), \ "must be C-string (NUL-terminated)") #define __must_be_noncstr(p) \ __BUILD_BUG_ON_ZERO_MSG(!__is_noncstr(p), \ "must be non-C-string (not NUL-terminated)") /* * Define TYPEOF_UNQUAL() to use __typeof_unqual__() as typeof * operator when available, to return an unqualified type of the exp. */ #if defined(USE_TYPEOF_UNQUAL) # define TYPEOF_UNQUAL(exp) __typeof_unqual__(exp) #else # define TYPEOF_UNQUAL(exp) __typeof__(exp) #endif #endif /* __KERNEL__ */ #if defined(CONFIG_CFI) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO) /* * Force a reference to the external symbol so the compiler generates * __kcfi_typid. */ #define KCFI_REFERENCE(sym) __ADDRESSABLE(sym) #else #define KCFI_REFERENCE(sym) #endif /** * 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__ */ /* * 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(sym, __attrs) \ static void * __used __attrs \ __UNIQUE_ID(__PASTE(addressable_, sym)) = (void *)(uintptr_t)&sym; #define __ADDRESSABLE(sym) \ ___ADDRESSABLE(sym, __section(".discard.addressable")) /* * This returns a constant expression while determining if an argument is * a constant expression, most importantly without evaluating the argument. * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> * * 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) \ (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) /* * Whether 'type' is a signed type or an unsigned type. Supports scalar types, * bool and also pointer types. */ #define is_signed_type(type) (((type)(-1)) < (__force type)1) #define is_unsigned_type(type) (!is_signed_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) (__builtin_constant_p(x) && (x)) /* * Similar to statically_true() but produces a constant expression * * To be used in conjunction with macros, such as BUILD_BUG_ON_ZERO(), * which require their input to be a constant expression and for which * statically_true() would otherwise fail. * * This is a trade-off: const_true() requires all its operands to be * compile time constants. Else, it would always returns false even on * the most trivial cases like: * * true || non_const_var * * On the opposite, statically_true() is able to fold more complex * tautologies and will return true on expressions such as: * * !(non_const_var * 8 % 4) * * For the general case, statically_true() is better. */ #define const_true(x) __builtin_choose_expr(__is_constexpr(x), x, false) /* * 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() mb() #include <asm/rwonce.h> #endif /* __LINUX_COMPILER_H */
