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 void ftrace_likely_update(struct ftrace_likely_data *f, int val,
16 			  int expect, int is_constant);
17 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
18     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
19 #define likely_notrace(x)	__builtin_expect(!!(x), 1)
20 #define unlikely_notrace(x)	__builtin_expect(!!(x), 0)
21 
22 #define __branch_check__(x, expect, is_constant) ({			\
23 			long ______r;					\
24 			static struct ftrace_likely_data		\
25 				__aligned(4)				\
26 				__section("_ftrace_annotated_branch")	\
27 				______f = {				\
28 				.data.func = __func__,			\
29 				.data.file = __FILE__,			\
30 				.data.line = __LINE__,			\
31 			};						\
32 			______r = __builtin_expect(!!(x), expect);	\
33 			ftrace_likely_update(&______f, ______r,		\
34 					     expect, is_constant);	\
35 			______r;					\
36 		})
37 
38 /*
39  * Using __builtin_constant_p(x) to ignore cases where the return
40  * value is always the same.  This idea is taken from a similar patch
41  * written by Daniel Walker.
42  */
43 # ifndef likely
44 #  define likely(x)	(__branch_check__(x, 1, __builtin_constant_p(x)))
45 # endif
46 # ifndef unlikely
47 #  define unlikely(x)	(__branch_check__(x, 0, __builtin_constant_p(x)))
48 # endif
49 
50 #ifdef CONFIG_PROFILE_ALL_BRANCHES
51 /*
52  * "Define 'is'", Bill Clinton
53  * "Define 'if'", Steven Rostedt
54  */
55 #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
56 
57 #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
58 
59 #define __trace_if_value(cond) ({			\
60 	static struct ftrace_branch_data		\
61 		__aligned(4)				\
62 		__section("_ftrace_branch")		\
63 		__if_trace = {				\
64 			.func = __func__,		\
65 			.file = __FILE__,		\
66 			.line = __LINE__,		\
67 		};					\
68 	(cond) ?					\
69 		(__if_trace.miss_hit[1]++,1) :		\
70 		(__if_trace.miss_hit[0]++,0);		\
71 })
72 
73 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
74 
75 #else
76 # define likely(x)	__builtin_expect(!!(x), 1)
77 # define unlikely(x)	__builtin_expect(!!(x), 0)
78 # define likely_notrace(x)	likely(x)
79 # define unlikely_notrace(x)	unlikely(x)
80 #endif
81 
82 /* Optimization barrier */
83 #ifndef barrier
84 /* The "volatile" is due to gcc bugs */
85 # define barrier() __asm__ __volatile__("": : :"memory")
86 #endif
87 
88 #ifndef barrier_data
89 /*
90  * This version is i.e. to prevent dead stores elimination on @ptr
91  * where gcc and llvm may behave differently when otherwise using
92  * normal barrier(): while gcc behavior gets along with a normal
93  * barrier(), llvm needs an explicit input variable to be assumed
94  * clobbered. The issue is as follows: while the inline asm might
95  * access any memory it wants, the compiler could have fit all of
96  * @ptr into memory registers instead, and since @ptr never escaped
97  * from that, it proved that the inline asm wasn't touching any of
98  * it. This version works well with both compilers, i.e. we're telling
99  * the compiler that the inline asm absolutely may see the contents
100  * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
101  */
102 # define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
103 #endif
104 
105 /* workaround for GCC PR82365 if needed */
106 #ifndef barrier_before_unreachable
107 # define barrier_before_unreachable() do { } while (0)
108 #endif
109 
110 /* Unreachable code */
111 #ifdef CONFIG_OBJTOOL
112 /*
113  * These macros help objtool understand GCC code flow for unreachable code.
114  * The __COUNTER__ based labels are a hack to make each instance of the macros
115  * unique, to convince GCC not to merge duplicate inline asm statements.
116  */
117 #define __stringify_label(n) #n
118 
119 #define __annotate_unreachable(c) ({					\
120 	asm volatile(__stringify_label(c) ":\n\t"			\
121 		     ".pushsection .discard.unreachable\n\t"		\
122 		     ".long " __stringify_label(c) "b - .\n\t"		\
123 		     ".popsection\n\t" : : "i" (c));			\
124 })
125 #define annotate_unreachable() __annotate_unreachable(__COUNTER__)
126 
127 /* Annotate a C jump table to allow objtool to follow the code flow */
128 #define __annotate_jump_table __section(".rodata..c_jump_table")
129 
130 #else /* !CONFIG_OBJTOOL */
131 #define annotate_unreachable()
132 #define __annotate_jump_table
133 #endif /* CONFIG_OBJTOOL */
134 
135 #ifndef unreachable
136 # define unreachable() do {		\
137 	annotate_unreachable();		\
138 	__builtin_unreachable();	\
139 } while (0)
140 #endif
141 
142 /*
143  * KENTRY - kernel entry point
144  * This can be used to annotate symbols (functions or data) that are used
145  * without their linker symbol being referenced explicitly. For example,
146  * interrupt vector handlers, or functions in the kernel image that are found
147  * programatically.
148  *
149  * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
150  * are handled in their own way (with KEEP() in linker scripts).
151  *
152  * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
153  * linker script. For example an architecture could KEEP() its entire
154  * boot/exception vector code rather than annotate each function and data.
155  */
156 #ifndef KENTRY
157 # define KENTRY(sym)						\
158 	extern typeof(sym) sym;					\
159 	static const unsigned long __kentry_##sym		\
160 	__used							\
161 	__attribute__((__section__("___kentry+" #sym)))		\
162 	= (unsigned long)&sym;
163 #endif
164 
165 #ifndef RELOC_HIDE
166 # define RELOC_HIDE(ptr, off)					\
167   ({ unsigned long __ptr;					\
168      __ptr = (unsigned long) (ptr);				\
169     (typeof(ptr)) (__ptr + (off)); })
170 #endif
171 
172 #define absolute_pointer(val)	RELOC_HIDE((void *)(val), 0)
173 
174 #ifndef OPTIMIZER_HIDE_VAR
175 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
176 #define OPTIMIZER_HIDE_VAR(var)						\
177 	__asm__ ("" : "=r" (var) : "0" (var))
178 #endif
179 
180 /* Not-quite-unique ID. */
181 #ifndef __UNIQUE_ID
182 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
183 #endif
184 
185 /**
186  * data_race - mark an expression as containing intentional data races
187  *
188  * This data_race() macro is useful for situations in which data races
189  * should be forgiven.  One example is diagnostic code that accesses
190  * shared variables but is not a part of the core synchronization design.
191  *
192  * This macro *does not* affect normal code generation, but is a hint
193  * to tooling that data races here are to be ignored.
194  */
195 #define data_race(expr)							\
196 ({									\
197 	__unqual_scalar_typeof(({ expr; })) __v = ({			\
198 		__kcsan_disable_current();				\
199 		expr;							\
200 	});								\
201 	__kcsan_enable_current();					\
202 	__v;								\
203 })
204 
205 #endif /* __KERNEL__ */
206 
207 /*
208  * Force the compiler to emit 'sym' as a symbol, so that we can reference
209  * it from inline assembler. Necessary in case 'sym' could be inlined
210  * otherwise, or eliminated entirely due to lack of references that are
211  * visible to the compiler.
212  */
213 #define ___ADDRESSABLE(sym, __attrs) \
214 	static void * __used __attrs \
215 		__UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)&sym;
216 #define __ADDRESSABLE(sym) \
217 	___ADDRESSABLE(sym, __section(".discard.addressable"))
218 
219 /**
220  * offset_to_ptr - convert a relative memory offset to an absolute pointer
221  * @off:	the address of the 32-bit offset value
222  */
offset_to_ptr(const int * off)223 static inline void *offset_to_ptr(const int *off)
224 {
225 	return (void *)((unsigned long)off + *off);
226 }
227 
228 #endif /* __ASSEMBLY__ */
229 
230 /* &a[0] degrades to a pointer: a different type from an array */
231 #define __must_be_array(a)	BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
232 
233 /*
234  * Whether 'type' is a signed type or an unsigned type. Supports scalar types,
235  * bool and also pointer types.
236  */
237 #define is_signed_type(type) (((type)(-1)) < (__force type)1)
238 #define is_unsigned_type(type) (!is_signed_type(type))
239 
240 /*
241  * This is needed in functions which generate the stack canary, see
242  * arch/x86/kernel/smpboot.c::start_secondary() for an example.
243  */
244 #define prevent_tail_call_optimization()	mb()
245 
246 #include <asm/rwonce.h>
247 
248 #endif /* __LINUX_COMPILER_H */
249