include/linux/compiler-gcc.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_COMPILER_TYPES_H
   3 #error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
   4 #endif
   5
   6 /*
   7  * Common definitions for all gcc versions go here.
   8  */
   9 #define GCC_VERSION (__GNUC__ * 10000           \
  10                      + __GNUC_MINOR__ * 100     \
  11                      + __GNUC_PATCHLEVEL__)
  12
  13 /* Optimization barrier */
  14
  15 /* The "volatile" is due to gcc bugs */
  16 #define barrier() __asm__ __volatile__("": : :"memory")
  17 /*
  18  * This version is i.e. to prevent dead stores elimination on @ptr
  19  * where gcc and llvm may behave differently when otherwise using
  20  * normal barrier(): while gcc behavior gets along with a normal
  21  * barrier(), llvm needs an explicit input variable to be assumed
  22  * clobbered. The issue is as follows: while the inline asm might
  23  * access any memory it wants, the compiler could have fit all of
  24  * @ptr into memory registers instead, and since @ptr never escaped
  25  * from that, it proved that the inline asm wasn't touching any of
  26  * it. This version works well with both compilers, i.e. we're telling
  27  * the compiler that the inline asm absolutely may see the contents
  28  * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
  29  */
  30 #define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
  31
  32 /*
  33  * This macro obfuscates arithmetic on a variable address so that gcc
  34  * shouldn't recognize the original var, and make assumptions about it.
  35  *
  36  * This is needed because the C standard makes it undefined to do
  37  * pointer arithmetic on "objects" outside their boundaries and the
  38  * gcc optimizers assume this is the case. In particular they
  39  * assume such arithmetic does not wrap.
  40  *
  41  * A miscompilation has been observed because of this on PPC.
  42  * To work around it we hide the relationship of the pointer and the object
  43  * using this macro.
  44  *
  45  * Versions of the ppc64 compiler before 4.1 had a bug where use of
  46  * RELOC_HIDE could trash r30. The bug can be worked around by changing
  47  * the inline assembly constraint from =g to =r, in this particular
  48  * case either is valid.
  49  */
  50 #define RELOC_HIDE(ptr, off)                                            \
  51 ({                                                                      \
  52         unsigned long __ptr;                                            \
  53         __asm__ ("" : "=r"(__ptr) : "0"(ptr));                          \
  54         (typeof(ptr)) (__ptr + (off));                                  \
  55 })
  56
  57 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
  58 #define OPTIMIZER_HIDE_VAR(var)                                         \
  59         __asm__ ("" : "=r" (var) : "0" (var))
  60
  61 #ifdef __CHECKER__
  62 #define __must_be_array(a)      0
  63 #else
  64 /* &a[0] degrades to a pointer: a different type from an array */
  65 #define __must_be_array(a)      BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
  66 #endif
  67
  68 /*
  69  * Feature detection for gnu_inline (gnu89 extern inline semantics). Either
  70  * __GNUC_STDC_INLINE__ is defined (not using gnu89 extern inline semantics,
  71  * and we opt in to the gnu89 semantics), or __GNUC_STDC_INLINE__ is not
  72  * defined so the gnu89 semantics are the default.
  73  */
  74 #ifdef __GNUC_STDC_INLINE__
  75 # define __gnu_inline   __attribute__((gnu_inline))
  76 #else
  77 # define __gnu_inline
  78 #endif
  79
  80 /*
  81  * Force always-inline if the user requests it so via the .config,
  82  * or if gcc is too old.
  83  * GCC does not warn about unused static inline functions for
  84  * -Wunused-function.  This turns out to avoid the need for complex #ifdef
  85  * directives.  Suppress the warning in clang as well by using "unused"
  86  * function attribute, which is redundant but not harmful for gcc.
  87  * Prefer gnu_inline, so that extern inline functions do not emit an
  88  * externally visible function. This makes extern inline behave as per gnu89
  89  * semantics rather than c99. This prevents multiple symbol definition errors
  90  * of extern inline functions at link time.
  91  * A lot of inline functions can cause havoc with function tracing.
  92  */
  93 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||                \
  94     !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
  95 #define inline \
  96         inline __attribute__((always_inline, unused)) notrace __gnu_inline
  97 #else
  98 #define inline inline           __attribute__((unused)) notrace __gnu_inline
  99 #endif
 100
 101 #define __inline__ inline
 102 #define __inline inline
 103 #define __always_inline inline __attribute__((always_inline))
 104 #define  noinline       __attribute__((noinline))
 105
 106 #define __deprecated    __attribute__((deprecated))
 107 #define __packed        __attribute__((packed))
 108 #define __weak          __attribute__((weak))
 109 #define __alias(symbol) __attribute__((alias(#symbol)))
 110
 111 #ifdef CONFIG_RETPOLINE
 112 #define __noretpoline __attribute__((indirect_branch("keep")))
 113 #endif
 114
 115 /*
 116  * it doesn't make sense on ARM (currently the only user of __naked)
 117  * to trace naked functions because then mcount is called without
 118  * stack and frame pointer being set up and there is no chance to
 119  * restore the lr register to the value before mcount was called.
 120  *
 121  * The asm() bodies of naked functions often depend on standard calling
 122  * conventions, therefore they must be noinline and noclone.
 123  *
 124  * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
 125  * See GCC PR44290.
 126  */
 127 #define __naked         __attribute__((naked)) noinline __noclone notrace
 128
 129 #define __noreturn      __attribute__((noreturn))
 130
 131 /*
 132  * From the GCC manual:
 133  *
 134  * Many functions have no effects except the return value and their
 135  * return value depends only on the parameters and/or global
 136  * variables.  Such a function can be subject to common subexpression
 137  * elimination and loop optimization just as an arithmetic operator
 138  * would be.
 139  * [...]
 140  */
 141 #define __pure                  __attribute__((pure))
 142 #define __aligned(x)            __attribute__((aligned(x)))
 143 #define __aligned_largest       __attribute__((aligned))
 144 #define __printf(a, b)          __attribute__((format(printf, a, b)))
 145 #define __scanf(a, b)           __attribute__((format(scanf, a, b)))
 146 #define __attribute_const__     __attribute__((__const__))
 147 #define __maybe_unused          __attribute__((unused))
 148 #define __always_unused         __attribute__((unused))
 149 #define __mode(x)               __attribute__((mode(x)))
 150
 151 /* gcc version specific checks */
 152
 153 #if GCC_VERSION < 30200
 154 # error Sorry, your compiler is too old - please upgrade it.
 155 #endif
 156
 157 #if GCC_VERSION < 30300
 158 # define __used                 __attribute__((__unused__))
 159 #else
 160 # define __used                 __attribute__((__used__))
 161 #endif
 162
 163 #ifdef CONFIG_GCOV_KERNEL
 164 # if GCC_VERSION < 30400
 165 #   error "GCOV profiling support for gcc versions below 3.4 not included"
 166 # endif /* __GNUC_MINOR__ */
 167 #endif /* CONFIG_GCOV_KERNEL */
 168
 169 #if GCC_VERSION >= 30400
 170 #define __must_check            __attribute__((warn_unused_result))
 171 #define __malloc                __attribute__((__malloc__))
 172 #endif
 173
 174 #if GCC_VERSION >= 40000
 175
 176 /* GCC 4.1.[01] miscompiles __weak */
 177 #ifdef __KERNEL__
 178 # if GCC_VERSION >= 40100 &&  GCC_VERSION <= 40101
 179 #  error Your version of gcc miscompiles the __weak directive
 180 # endif
 181 #endif
 182
 183 #define __used                  __attribute__((__used__))
 184 #define __compiler_offsetof(a, b)                                       \
 185         __builtin_offsetof(a, b)
 186
 187 #if GCC_VERSION >= 40100
 188 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
 189 #endif
 190
 191 #if GCC_VERSION >= 40300
 192 /* Mark functions as cold. gcc will assume any path leading to a call
 193  * to them will be unlikely.  This means a lot of manual unlikely()s
 194  * are unnecessary now for any paths leading to the usual suspects
 195  * like BUG(), printk(), panic() etc. [but let's keep them for now for
 196  * older compilers]
 197  *
 198  * Early snapshots of gcc 4.3 don't support this and we can't detect this
 199  * in the preprocessor, but we can live with this because they're unreleased.
 200  * Maketime probing would be overkill here.
 201  *
 202  * gcc also has a __attribute__((__hot__)) to move hot functions into
 203  * a special section, but I don't see any sense in this right now in
 204  * the kernel context
 205  */
 206 #define __cold                  __attribute__((__cold__))
 207
 208 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
 209
 210 #ifndef __CHECKER__
 211 # define __compiletime_warning(message) __attribute__((warning(message)))
 212 # define __compiletime_error(message) __attribute__((error(message)))
 213 #endif /* __CHECKER__ */
 214 #endif /* GCC_VERSION >= 40300 */
 215
 216 #if GCC_VERSION >= 40400
 217 #define __optimize(level)       __attribute__((__optimize__(level)))
 218 #define __nostackprotector      __optimize("no-stack-protector")
 219 #endif /* GCC_VERSION >= 40400 */
 220
 221 #if GCC_VERSION >= 40500
 222
 223 #ifndef __CHECKER__
 224 #ifdef LATENT_ENTROPY_PLUGIN
 225 #define __latent_entropy __attribute__((latent_entropy))
 226 #endif
 227 #endif
 228
 229 /*
 230  * calling noreturn functions, __builtin_unreachable() and __builtin_trap()
 231  * confuse the stack allocation in gcc, leading to overly large stack
 232  * frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
 233  *
 234  * Adding an empty inline assembly before it works around the problem
 235  */
 236 #define barrier_before_unreachable() asm volatile("")
 237
 238 /*
 239  * Mark a position in code as unreachable.  This can be used to
 240  * suppress control flow warnings after asm blocks that transfer
 241  * control elsewhere.
 242  *
 243  * Early snapshots of gcc 4.5 don't support this and we can't detect
 244  * this in the preprocessor, but we can live with this because they're
 245  * unreleased.  Really, we need to have autoconf for the kernel.
 246  */
 247 #define unreachable() \
 248         do {                                    \
 249                 annotate_unreachable();         \
 250                 barrier_before_unreachable();   \
 251                 __builtin_unreachable();        \
 252         } while (0)
 253
 254 /* Mark a function definition as prohibited from being cloned. */
 255 #define __noclone       __attribute__((__noclone__, __optimize__("no-tracer")))
 256
 257 #if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
 258 #define __randomize_layout __attribute__((randomize_layout))
 259 #define __no_randomize_layout __attribute__((no_randomize_layout))
 260 /* This anon struct can add padding, so only enable it under randstruct. */
 261 #define randomized_struct_fields_start  struct {
 262 #define randomized_struct_fields_end    } __randomize_layout;
 263 #endif
 264
 265 #endif /* GCC_VERSION >= 40500 */
 266
 267 #if GCC_VERSION >= 40600
 268
 269 /*
 270  * When used with Link Time Optimization, gcc can optimize away C functions or
 271  * variables which are referenced only from assembly code.  __visible tells the
 272  * optimizer that something else uses this function or variable, thus preventing
 273  * this.
 274  */
 275 #define __visible       __attribute__((externally_visible))
 276
 277 #endif /* GCC_VERSION >= 40600 */
 278
 279
 280 #if GCC_VERSION >= 40900 && !defined(__CHECKER__)
 281 /*
 282  * __assume_aligned(n, k): Tell the optimizer that the returned
 283  * pointer can be assumed to be k modulo n. The second argument is
 284  * optional (default 0), so we use a variadic macro to make the
 285  * shorthand.
 286  *
 287  * Beware: Do not apply this to functions which may return
 288  * ERR_PTRs. Also, it is probably unwise to apply it to functions
 289  * returning extra information in the low bits (but in that case the
 290  * compiler should see some alignment anyway, when the return value is
 291  * massaged by 'flags = ptr & 3; ptr &= ~3;').
 292  */
 293 #define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
 294 #endif
 295
 296 /*
 297  * GCC 'asm goto' miscompiles certain code sequences:
 298  *
 299  *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
 300  *
 301  * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
 302  *
 303  * (asm goto is automatically volatile - the naming reflects this.)
 304  */
 305 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
 306
 307 /*
 308  * sparse (__CHECKER__) pretends to be gcc, but can't do constant
 309  * folding in __builtin_bswap*() (yet), so don't set these for it.
 310  */
 311 #if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
 312 #if GCC_VERSION >= 40400
 313 #define __HAVE_BUILTIN_BSWAP32__
 314 #define __HAVE_BUILTIN_BSWAP64__
 315 #endif
 316 #if GCC_VERSION >= 40800
 317 #define __HAVE_BUILTIN_BSWAP16__
 318 #endif
 319 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
 320
 321 #if GCC_VERSION >= 70000
 322 #define KASAN_ABI_VERSION 5
 323 #elif GCC_VERSION >= 50000
 324 #define KASAN_ABI_VERSION 4
 325 #elif GCC_VERSION >= 40902
 326 #define KASAN_ABI_VERSION 3
 327 #endif
 328
 329 #if GCC_VERSION >= 40902
 330 /*
 331  * Tell the compiler that address safety instrumentation (KASAN)
 332  * should not be applied to that function.
 333  * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
 334  */
 335 #define __no_sanitize_address __attribute__((no_sanitize_address))
 336 #endif
 337
 338 #if GCC_VERSION >= 50100
 339 /*
 340  * Mark structures as requiring designated initializers.
 341  * https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
 342  */
 343 #define __designated_init __attribute__((designated_init))
 344 #endif
 345
 346 #if GCC_VERSION >= 90100
 347 #define __copy(symbol)                 __attribute__((__copy__(symbol)))
 348 #endif
 349
 350 #endif  /* gcc version >= 40000 specific checks */
 351
 352 #if !defined(__noclone)
 353 #define __noclone       /* not needed */
 354 #endif
 355
 356 #if !defined(__no_sanitize_address)
 357 #define __no_sanitize_address
 358 #endif
 359
 360 /*
 361  * A trick to suppress uninitialized variable warning without generating any
 362  * code
 363  */
 364 #define uninitialized_var(x) x = x
 365
 366 #if GCC_VERSION >= 50100
 367 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 368 #endif