diff options
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 284 |
1 files changed, 221 insertions, 63 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 6810d80acb0b..6f04a1d8c720 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -12,11 +12,10 @@ * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code * to disable branch tracing on a per file basis. */ -#if defined(CONFIG_TRACE_BRANCH_PROFILING) \ - && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__) 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) @@ -24,7 +23,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, long ______r; \ static struct ftrace_likely_data \ __aligned(4) \ - __section(_ftrace_annotated_branch) \ + __section("_ftrace_annotated_branch") \ ______f = { \ .data.func = __func__, \ .data.file = __FILE__, \ @@ -60,7 +59,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #define __trace_if_value(cond) ({ \ static struct ftrace_branch_data \ __aligned(4) \ - __section(_ftrace_branch) \ + __section("_ftrace_branch") \ __if_trace = { \ .func = __func__, \ .file = __FILE__, \ @@ -76,15 +75,31 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #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() +/* The "volatile" is due to gcc bugs */ +# define barrier() __asm__ __volatile__("": : :"memory") #endif #ifndef barrier_data -# define barrier_data(ptr) barrier() +/* + * 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 */ @@ -93,48 +108,22 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #endif /* Unreachable code */ -#ifdef CONFIG_STACK_VALIDATION -/* - * 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 annotate_reachable() ({ \ - asm volatile("%c0:\n\t" \ - ".pushsection .discard.reachable\n\t" \ - ".long %c0b - .\n\t" \ - ".popsection\n\t" : : "i" (__COUNTER__)); \ -}) -#define annotate_unreachable() ({ \ - asm volatile("%c0:\n\t" \ - ".pushsection .discard.unreachable\n\t" \ - ".long %c0b - .\n\t" \ - ".popsection\n\t" : : "i" (__COUNTER__)); \ -}) -#define ASM_UNREACHABLE \ - "999:\n\t" \ - ".pushsection .discard.unreachable\n\t" \ - ".long 999b - .\n\t" \ - ".popsection\n\t" - +#ifdef CONFIG_OBJTOOL /* Annotate a C jump table to allow objtool to follow the code flow */ -#define __annotate_jump_table __section(.rodata..c_jump_table) - -#else -#define annotate_reachable() -#define annotate_unreachable() +#define __annotate_jump_table __section(".data.rel.ro.c_jump_table") +#else /* !CONFIG_OBJTOOL */ #define __annotate_jump_table -#endif +#endif /* CONFIG_OBJTOOL */ -#ifndef ASM_UNREACHABLE -# define ASM_UNREACHABLE -#endif -#ifndef unreachable -# define unreachable() do { \ - annotate_unreachable(); \ +/* + * 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) -#endif /* * KENTRY - kernel entry point @@ -155,7 +144,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, extern typeof(sym) sym; \ static const unsigned long __kentry_##sym \ __used \ - __section("___kentry" "+" #sym ) \ + __attribute__((__section__("___kentry+" #sym))) \ = (unsigned long)&sym; #endif @@ -166,16 +155,15 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, (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 -/* Not-quite-unique ID. */ -#ifndef __UNIQUE_ID -# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__) -#endif +#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) /** * data_race - mark an expression as containing intentional data races @@ -183,31 +171,92 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, * 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. + * 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) \ ({ \ - __unqual_scalar_typeof(({ expr; })) __v = ({ \ - __kcsan_disable_current(); \ - expr; \ - }); \ + __kcsan_disable_current(); \ + __auto_type __v = (expr); \ __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)") + +/* + * Use __typeof_unqual__() when available. + * + * XXX: Remove test for __CHECKER__ once + * sparse learns about __typeof_unqual__(). + */ +#if CC_HAS_TYPEOF_UNQUAL && !defined(__CHECKER__) +# define USE_TYPEOF_UNQUAL 1 +#endif + +/* + * 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_CLANG) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO) /* - * 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. + * Force a reference to the external symbol so the compiler generates + * __kcfi_typid. */ -#define __ADDRESSABLE(sym) \ - static void * __section(.discard.addressable) __used \ - __PASTE(__addressable_##sym, __LINE__) = (void *)&sym; +#define KCFI_REFERENCE(sym) __ADDRESSABLE(sym) +#else +#define KCFI_REFERENCE(sym) +#endif /** * offset_to_ptr - convert a relative memory offset to an absolute pointer @@ -220,8 +269,117 @@ static inline void *offset_to_ptr(const int *off) #endif /* __ASSEMBLY__ */ -/* &a[0] degrades to a pointer: a different type from an array */ -#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) +#ifdef CONFIG_64BIT +#define ARCH_SEL(a,b) a +#else +#define ARCH_SEL(a,b) b +#endif + +/* + * 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")) + +#define __ADDRESSABLE_ASM(sym) \ + .pushsection .discard.addressable,"aw"; \ + .align ARCH_SEL(8,4); \ + ARCH_SEL(.quad, .long) __stringify(sym); \ + .popsection; + +#define __ADDRESSABLE_ASM_STR(sym) __stringify(__ADDRESSABLE_ASM(sym)) + +/* + * 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 |