diff options
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 546 |
1 files changed, 284 insertions, 262 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 92669cd182a6..04487c9bd751 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -1,114 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ #ifndef __LINUX_COMPILER_H #define __LINUX_COMPILER_H -#ifndef __ASSEMBLY__ - -#ifdef __CHECKER__ -# define __user __attribute__((noderef, address_space(1))) -# define __kernel __attribute__((address_space(0))) -# define __safe __attribute__((safe)) -# define __force __attribute__((force)) -# define __nocast __attribute__((nocast)) -# define __iomem __attribute__((noderef, address_space(2))) -# define __must_hold(x) __attribute__((context(x,1,1))) -# define __acquires(x) __attribute__((context(x,0,1))) -# define __releases(x) __attribute__((context(x,1,0))) -# define __acquire(x) __context__(x,1) -# define __release(x) __context__(x,-1) -# define __cond_lock(x,c) ((c) ? ({ __acquire(x); 1; }) : 0) -# define __percpu __attribute__((noderef, address_space(3))) -#ifdef CONFIG_SPARSE_RCU_POINTER -# define __rcu __attribute__((noderef, address_space(4))) -#else -# define __rcu -#endif -extern void __chk_user_ptr(const volatile void __user *); -extern void __chk_io_ptr(const volatile void __iomem *); -#else -# define __user -# define __kernel -# define __safe -# define __force -# define __nocast -# define __iomem -# define __chk_user_ptr(x) (void)0 -# define __chk_io_ptr(x) (void)0 -# define __builtin_warning(x, y...) (1) -# define __must_hold(x) -# define __acquires(x) -# define __releases(x) -# define __acquire(x) (void)0 -# define __release(x) (void)0 -# define __cond_lock(x,c) (c) -# define __percpu -# define __rcu -#endif +#include <linux/compiler_types.h> -/* Indirect macros required for expanded argument pasting, eg. __LINE__. */ -#define ___PASTE(a,b) a##b -#define __PASTE(a,b) ___PASTE(a,b) +#ifndef __ASSEMBLY__ #ifdef __KERNEL__ -#ifdef __GNUC__ -#include <linux/compiler-gcc.h> -#endif - -#define notrace __attribute__((no_instrument_function)) - -/* Intel compiler defines __GNUC__. So we will overwrite implementations - * coming from above header files here - */ -#ifdef __INTEL_COMPILER -# include <linux/compiler-intel.h> -#endif - -/* - * Generic compiler-dependent macros required for kernel - * build go below this comment. Actual compiler/compiler version - * specific implementations come from the above header files - */ - -struct ftrace_branch_data { - const char *func; - const char *file; - unsigned line; - union { - struct { - unsigned long correct; - unsigned long incorrect; - }; - struct { - unsigned long miss; - unsigned long hit; - }; - unsigned long miss_hit[2]; - }; -}; - /* * 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__) -void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); - #define likely_notrace(x) __builtin_expect(!!(x), 1) #define unlikely_notrace(x) __builtin_expect(!!(x), 0) -#define __branch_check__(x, expect) ({ \ - int ______r; \ - static struct ftrace_branch_data \ - __attribute__((__aligned__(4))) \ - __attribute__((section("_ftrace_annotated_branch"))) \ +#define __branch_check__(x, expect, is_constant) ({ \ + long ______r; \ + static struct ftrace_likely_data \ + __aligned(4) \ + __section("_ftrace_annotated_branch") \ ______f = { \ - .func = __func__, \ - .file = __FILE__, \ - .line = __LINE__, \ + .data.func = __func__, \ + .data.file = __FILE__, \ + .data.line = __LINE__, \ }; \ - ______r = likely_notrace(x); \ - ftrace_likely_update(&______f, ______r, expect); \ + ______r = __builtin_expect(!!(x), expect); \ + ftrace_likely_update(&______f, ______r, \ + expect, is_constant); \ ______r; \ }) @@ -118,10 +41,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); * written by Daniel Walker. */ # ifndef likely -# define likely(x) (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1)) +# define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x))) # endif # ifndef unlikely -# define unlikely(x) (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0)) +# define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x))) # endif #ifdef CONFIG_PROFILE_ALL_BRANCHES @@ -129,232 +52,331 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); * "Define 'is'", Bill Clinton * "Define 'if'", Steven Rostedt */ -#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) ) -#define __trace_if(cond) \ - if (__builtin_constant_p((cond)) ? !!(cond) : \ - ({ \ - int ______r; \ - static struct ftrace_branch_data \ - __attribute__((__aligned__(4))) \ - __attribute__((section("_ftrace_branch"))) \ - ______f = { \ - .func = __func__, \ - .file = __FILE__, \ - .line = __LINE__, \ - }; \ - ______r = !!(cond); \ - ______f.miss_hit[______r]++; \ - ______r; \ - })) +#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 -# define barrier() __memory_barrier() -#endif - -/* Unreachable code */ -#ifndef unreachable -# define unreachable() do { } while (1) +/* The "volatile" is due to gcc bugs */ +# define barrier() __asm__ __volatile__("": : :"memory") #endif -#ifndef RELOC_HIDE -# define RELOC_HIDE(ptr, off) \ - ({ unsigned long __ptr; \ - __ptr = (unsigned long) (ptr); \ - (typeof(ptr)) (__ptr + (off)); }) +#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 -/* Not-quite-unique ID. */ -#ifndef __UNIQUE_ID -# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__) +/* workaround for GCC PR82365 if needed */ +#ifndef barrier_before_unreachable +# define barrier_before_unreachable() do { } while (0) #endif -#endif /* __KERNEL__ */ +/* 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 */ -#endif /* __ASSEMBLY__ */ +/* + * 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) -#ifdef __KERNEL__ /* - * Allow us to mark functions as 'deprecated' and have gcc emit a nice - * warning for each use, in hopes of speeding the functions removal. - * Usage is: - * int __deprecated foo(void) + * 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 __deprecated -# define __deprecated /* unimplemented */ +#ifndef KENTRY +# define KENTRY(sym) \ + extern typeof(sym) sym; \ + static const unsigned long __kentry_##sym \ + __used \ + __attribute__((__section__("___kentry+" #sym))) \ + = (unsigned long)&sym; #endif -#ifdef MODULE -#define __deprecated_for_modules __deprecated -#else -#define __deprecated_for_modules +#ifndef RELOC_HIDE +# define RELOC_HIDE(ptr, off) \ + ({ unsigned long __ptr; \ + __ptr = (unsigned long) (ptr); \ + (typeof(ptr)) (__ptr + (off)); }) #endif -#ifndef __must_check -#define __must_check -#endif +#define absolute_pointer(val) RELOC_HIDE((void *)(val), 0) -#ifndef CONFIG_ENABLE_MUST_CHECK -#undef __must_check -#define __must_check -#endif -#ifndef CONFIG_ENABLE_WARN_DEPRECATED -#undef __deprecated -#undef __deprecated_for_modules -#define __deprecated -#define __deprecated_for_modules +#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 -/* - * Allow us to avoid 'defined but not used' warnings on functions and data, - * as well as force them to be emitted to the assembly file. - * - * As of gcc 3.4, static functions that are not marked with attribute((used)) - * may be elided from the assembly file. As of gcc 3.4, static data not so - * marked will not be elided, but this may change in a future gcc version. - * - * NOTE: Because distributions shipped with a backported unit-at-a-time - * compiler in gcc 3.3, we must define __used to be __attribute__((used)) - * for gcc >=3.3 instead of 3.4. +/* 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 * - * In prior versions of gcc, such functions and data would be emitted, but - * would be warned about except with attribute((unused)). + * 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(). * - * Mark functions that are referenced only in inline assembly as __used so - * the code is emitted even though it appears to be unreferenced. + * 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)). */ -#ifndef __used -# define __used /* unimplemented */ -#endif +#define data_race(expr) \ +({ \ + __kcsan_disable_current(); \ + auto __v = (expr); \ + __kcsan_enable_current(); \ + __v; \ +}) -#ifndef __maybe_unused -# define __maybe_unused /* unimplemented */ -#endif +#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__ */ -#ifndef __always_unused -# define __always_unused /* unimplemented */ -#endif +/* &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") -#ifndef noinline -#define noinline -#endif +#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") /* - * Rather then using noinline to prevent stack consumption, use - * noinline_for_stack instead. For documentation reasons. + * If the "nonstring" attribute isn't available, we have to return true + * so the __must_*() checks pass when "nonstring" isn't supported. */ -#define noinline_for_stack noinline - -#ifndef __always_inline -#define __always_inline inline +#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 -#endif /* __KERNEL__ */ +/* 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)") /* - * From the GCC manual: - * - * Many functions do not examine any values except their arguments, - * and have no effects except the return value. Basically this is - * just slightly more strict class than the `pure' attribute above, - * since function is not allowed to read global memory. + * Use __typeof_unqual__() when available. * - * Note that a function that has pointer arguments and examines the - * data pointed to must _not_ be declared `const'. Likewise, a - * function that calls a non-`const' function usually must not be - * `const'. It does not make sense for a `const' function to return - * `void'. + * XXX: Remove test for __CHECKER__ once + * sparse learns about __typeof_unqual__(). */ -#ifndef __attribute_const__ -# define __attribute_const__ /* unimplemented */ +#if CC_HAS_TYPEOF_UNQUAL && !defined(__CHECKER__) +# define USE_TYPEOF_UNQUAL 1 #endif /* - * Tell gcc if a function is cold. The compiler will assume any path - * directly leading to the call is unlikely. + * Define TYPEOF_UNQUAL() to use __typeof_unqual__() as typeof + * operator when available, to return an unqualified type of the exp. */ - -#ifndef __cold -#define __cold +#if defined(USE_TYPEOF_UNQUAL) +# define TYPEOF_UNQUAL(exp) __typeof_unqual__(exp) +#else +# define TYPEOF_UNQUAL(exp) __typeof__(exp) #endif -/* Simple shorthand for a section definition */ -#ifndef __section -# define __section(S) __attribute__ ((__section__(#S))) -#endif +#endif /* __KERNEL__ */ -#ifndef __visible -#define __visible +#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 -/* Are two types/vars the same type (ignoring qualifiers)? */ -#ifndef __same_type -# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) -#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); +} -/* Compile time object size, -1 for unknown */ -#ifndef __compiletime_object_size -# define __compiletime_object_size(obj) -1 -#endif -#ifndef __compiletime_warning -# define __compiletime_warning(message) -#endif -#ifndef __compiletime_error -# define __compiletime_error(message) -# define __compiletime_error_fallback(condition) \ - do { ((void)sizeof(char[1 - 2 * condition])); } while (0) -#else -# define __compiletime_error_fallback(condition) do { } while (0) -#endif +#endif /* __ASSEMBLY__ */ -#define __compiletime_assert(condition, msg, prefix, suffix) \ - do { \ - bool __cond = !(condition); \ - extern void prefix ## suffix(void) __compiletime_error(msg); \ - if (__cond) \ - prefix ## suffix(); \ - __compiletime_error_fallback(__cond); \ - } while (0) +/* + * 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 _compiletime_assert(condition, msg, prefix, suffix) \ - __compiletime_assert(condition, msg, prefix, suffix) +#define __ADDRESSABLE(sym) \ + ___ADDRESSABLE(sym, __section(".discard.addressable")) -/** - * compiletime_assert - break build and emit msg if condition is false - * @condition: a compile-time constant condition to check - * @msg: a message to emit if condition is false +/* + * 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> * - * In tradition of POSIX assert, this macro will break the build if the - * supplied condition is *false*, emitting the supplied error message if the - * compiler has support to do so. + * 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 compiletime_assert(condition, msg) \ - _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) +#define __is_constexpr(x) \ + (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) /* - * Prevent the compiler from merging or refetching accesses. The compiler - * is also forbidden from reordering successive instances of ACCESS_ONCE(), - * but only when the compiler is aware of some particular ordering. One way - * to make the compiler aware of ordering is to put the two invocations of - * ACCESS_ONCE() in different C statements. + * 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?" * - * This macro does absolutely -nothing- to prevent the CPU from reordering, - * merging, or refetching absolutely anything at any time. Its main intended - * use is to mediate communication between process-level code and irq/NMI - * handlers, all running on the same CPU. + * 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 ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x)) +#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> -/* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */ -#ifdef CONFIG_KPROBES -# define __kprobes __attribute__((__section__(".kprobes.text"))) -#else -# define __kprobes -#endif #endif /* __LINUX_COMPILER_H */ |