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 #if GCC_VERSION < 40600
  14 # error Sorry, your compiler is too old - please upgrade it.
  15 #endif
  16
  17 /* Optimization barrier */
  18
  19 /* The "volatile" is due to gcc bugs */
  20 #define barrier() __asm__ __volatile__("": : :"memory")
  21 /*
  22  * This version is i.e. to prevent dead stores elimination on @ptr
  23  * where gcc and llvm may behave differently when otherwise using
  24  * normal barrier(): while gcc behavior gets along with a normal
  25  * barrier(), llvm needs an explicit input variable to be assumed
  26  * clobbered. The issue is as follows: while the inline asm might
  27  * access any memory it wants, the compiler could have fit all of
  28  * @ptr into memory registers instead, and since @ptr never escaped
  29  * from that, it proved that the inline asm wasn't touching any of
  30  * it. This version works well with both compilers, i.e. we're telling
  31  * the compiler that the inline asm absolutely may see the contents
  32  * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
  33  */
  34 #define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
  35
  36 /*
  37  * This macro obfuscates arithmetic on a variable address so that gcc
  38  * shouldn't recognize the original var, and make assumptions about it.
  39  *
  40  * This is needed because the C standard makes it undefined to do
  41  * pointer arithmetic on "objects" outside their boundaries and the
  42  * gcc optimizers assume this is the case. In particular they
  43  * assume such arithmetic does not wrap.
  44  *
  45  * A miscompilation has been observed because of this on PPC.
  46  * To work around it we hide the relationship of the pointer and the object
  47  * using this macro.
  48  *
  49  * Versions of the ppc64 compiler before 4.1 had a bug where use of
  50  * RELOC_HIDE could trash r30. The bug can be worked around by changing
  51  * the inline assembly constraint from =g to =r, in this particular
  52  * case either is valid.
  53  */
  54 #define RELOC_HIDE(ptr, off)                                            \
  55 ({                                                                      \
  56         unsigned long __ptr;                                            \
  57         __asm__ ("" : "=r"(__ptr) : "0"(ptr));                          \
  58         (typeof(ptr)) (__ptr + (off));                                  \
  59 })
  60
  61 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
  62 #define OPTIMIZER_HIDE_VAR(var)                                         \
  63         __asm__ ("" : "=r" (var) : "0" (var))
  64
  65 /*
  66  * A trick to suppress uninitialized variable warning without generating any
  67  * code
  68  */
  69 #define uninitialized_var(x) x = x
  70
  71 #ifdef __CHECKER__
  72 #define __must_be_array(a)      0
  73 #else
  74 /* &a[0] degrades to a pointer: a different type from an array */
  75 #define __must_be_array(a)      BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
  76 #endif
  77
  78 /*
  79  * Feature detection for gnu_inline (gnu89 extern inline semantics). Either
  80  * __GNUC_STDC_INLINE__ is defined (not using gnu89 extern inline semantics,
  81  * and we opt in to the gnu89 semantics), or __GNUC_STDC_INLINE__ is not
  82  * defined so the gnu89 semantics are the default.
  83  */
  84 #ifdef __GNUC_STDC_INLINE__
  85 # define __gnu_inline   __attribute__((gnu_inline))
  86 #else
  87 # define __gnu_inline
  88 #endif
  89
  90 /*
  91  * Force always-inline if the user requests it so via the .config,
  92  * or if gcc is too old.
  93  * GCC does not warn about unused static inline functions for
  94  * -Wunused-function.  This turns out to avoid the need for complex #ifdef
  95  * directives.  Suppress the warning in clang as well by using "unused"
  96  * function attribute, which is redundant but not harmful for gcc.
  97  * Prefer gnu_inline, so that extern inline functions do not emit an
  98  * externally visible function. This makes extern inline behave as per gnu89
  99  * semantics rather than c99. This prevents multiple symbol definition errors
 100  * of extern inline functions at link time.
 101  * A lot of inline functions can cause havoc with function tracing.
 102  */
 103 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||                \
 104     !defined(CONFIG_OPTIMIZE_INLINING)
 105 #define inline \
 106         inline __attribute__((always_inline, unused)) notrace __gnu_inline
 107 #else
 108 #define inline inline           __attribute__((unused)) notrace __gnu_inline
 109 #endif
 110
 111 #define __inline__ inline
 112 #define __inline inline
 113 #define __always_inline inline __attribute__((always_inline))
 114 #define  noinline       __attribute__((noinline))
 115
 116 #define __packed        __attribute__((packed))
 117 #define __weak          __attribute__((weak))
 118 #define __alias(symbol) __attribute__((alias(#symbol)))
 119
 120 #ifdef RETPOLINE
 121 #define __noretpoline __attribute__((indirect_branch("keep")))
 122 #endif
 123
 124 /*
 125  * it doesn't make sense on ARM (currently the only user of __naked)
 126  * to trace naked functions because then mcount is called without
 127  * stack and frame pointer being set up and there is no chance to
 128  * restore the lr register to the value before mcount was called.
 129  *
 130  * The asm() bodies of naked functions often depend on standard calling
 131  * conventions, therefore they must be noinline and noclone.
 132  *
 133  * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
 134  * See GCC PR44290.
 135  */
 136 #define __naked         __attribute__((naked)) noinline __noclone notrace
 137
 138 #define __noreturn      __attribute__((noreturn))
 139
 140 /*
 141  * From the GCC manual:
 142  *
 143  * Many functions have no effects except the return value and their
 144  * return value depends only on the parameters and/or global
 145  * variables.  Such a function can be subject to common subexpression
 146  * elimination and loop optimization just as an arithmetic operator
 147  * would be.
 148  * [...]
 149  */
 150 #define __pure                  __attribute__((pure))
 151 #define __aligned(x)            __attribute__((aligned(x)))
 152 #define __aligned_largest       __attribute__((aligned))
 153 #define __printf(a, b)          __attribute__((format(printf, a, b)))
 154 #define __scanf(a, b)           __attribute__((format(scanf, a, b)))
 155 #define __attribute_const__     __attribute__((__const__))
 156 #define __maybe_unused          __attribute__((unused))
 157 #define __always_unused         __attribute__((unused))
 158 #define __mode(x)               __attribute__((mode(x)))
 159
 160 #define __must_check            __attribute__((warn_unused_result))
 161 #define __malloc                __attribute__((__malloc__))
 162
 163 #define __used                  __attribute__((__used__))
 164 #define __compiler_offsetof(a, b)                                       \
 165         __builtin_offsetof(a, b)
 166
 167 /* Mark functions as cold. gcc will assume any path leading to a call
 168  * to them will be unlikely.  This means a lot of manual unlikely()s
 169  * are unnecessary now for any paths leading to the usual suspects
 170  * like BUG(), printk(), panic() etc. [but let's keep them for now for
 171  * older compilers]
 172  *
 173  * Early snapshots of gcc 4.3 don't support this and we can't detect this
 174  * in the preprocessor, but we can live with this because they're unreleased.
 175  * Maketime probing would be overkill here.
 176  *
 177  * gcc also has a __attribute__((__hot__)) to move hot functions into
 178  * a special section, but I don't see any sense in this right now in
 179  * the kernel context
 180  */
 181 #define __cold                  __attribute__((__cold__))
 182
 183 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
 184
 185 #define __optimize(level)       __attribute__((__optimize__(level)))
 186 #define __nostackprotector      __optimize("no-stack-protector")
 187
 188 #define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
 189
 190 #ifndef __CHECKER__
 191 #define __compiletime_warning(message) __attribute__((warning(message)))
 192 #define __compiletime_error(message) __attribute__((error(message)))
 193
 194 #ifdef LATENT_ENTROPY_PLUGIN
 195 #define __latent_entropy __attribute__((latent_entropy))
 196 #endif
 197 #endif /* __CHECKER__ */
 198
 199 /*
 200  * calling noreturn functions, __builtin_unreachable() and __builtin_trap()
 201  * confuse the stack allocation in gcc, leading to overly large stack
 202  * frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
 203  *
 204  * Adding an empty inline assembly before it works around the problem
 205  */
 206 #define barrier_before_unreachable() asm volatile("")
 207
 208 /*
 209  * Mark a position in code as unreachable.  This can be used to
 210  * suppress control flow warnings after asm blocks that transfer
 211  * control elsewhere.
 212  *
 213  * Early snapshots of gcc 4.5 don't support this and we can't detect
 214  * this in the preprocessor, but we can live with this because they're
 215  * unreleased.  Really, we need to have autoconf for the kernel.
 216  */
 217 #define unreachable() \
 218         do {                                    \
 219                 annotate_unreachable();         \
 220                 barrier_before_unreachable();   \
 221                 __builtin_unreachable();        \
 222         } while (0)
 223
 224 /* Mark a function definition as prohibited from being cloned. */
 225 #define __noclone       __attribute__((__noclone__, __optimize__("no-tracer")))
 226
 227 #if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
 228 #define __randomize_layout __attribute__((randomize_layout))
 229 #define __no_randomize_layout __attribute__((no_randomize_layout))
 230 /* This anon struct can add padding, so only enable it under randstruct. */
 231 #define randomized_struct_fields_start  struct {
 232 #define randomized_struct_fields_end    } __randomize_layout;
 233 #endif
 234
 235 /*
 236  * When used with Link Time Optimization, gcc can optimize away C functions or
 237  * variables which are referenced only from assembly code.  __visible tells the
 238  * optimizer that something else uses this function or variable, thus preventing
 239  * this.
 240  */
 241 #define __visible       __attribute__((externally_visible))
 242
 243 /* gcc version specific checks */
 244
 245 #if GCC_VERSION >= 40900 && !defined(__CHECKER__)
 246 /*
 247  * __assume_aligned(n, k): Tell the optimizer that the returned
 248  * pointer can be assumed to be k modulo n. The second argument is
 249  * optional (default 0), so we use a variadic macro to make the
 250  * shorthand.
 251  *
 252  * Beware: Do not apply this to functions which may return
 253  * ERR_PTRs. Also, it is probably unwise to apply it to functions
 254  * returning extra information in the low bits (but in that case the
 255  * compiler should see some alignment anyway, when the return value is
 256  * massaged by 'flags = ptr & 3; ptr &= ~3;').
 257  */
 258 #define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
 259 #endif
 260
 261 /*
 262  * GCC 'asm goto' miscompiles certain code sequences:
 263  *
 264  *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
 265  *
 266  * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
 267  *
 268  * (asm goto is automatically volatile - the naming reflects this.)
 269  */
 270 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
 271
 272 /*
 273  * sparse (__CHECKER__) pretends to be gcc, but can't do constant
 274  * folding in __builtin_bswap*() (yet), so don't set these for it.
 275  */
 276 #if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
 277 #define __HAVE_BUILTIN_BSWAP32__
 278 #define __HAVE_BUILTIN_BSWAP64__
 279 #if GCC_VERSION >= 40800
 280 #define __HAVE_BUILTIN_BSWAP16__
 281 #endif
 282 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
 283
 284 #if GCC_VERSION >= 70000
 285 #define KASAN_ABI_VERSION 5
 286 #elif GCC_VERSION >= 50000
 287 #define KASAN_ABI_VERSION 4
 288 #elif GCC_VERSION >= 40902
 289 #define KASAN_ABI_VERSION 3
 290 #endif
 291
 292 #if GCC_VERSION >= 40902
 293 /*
 294  * Tell the compiler that address safety instrumentation (KASAN)
 295  * should not be applied to that function.
 296  * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
 297  */
 298 #define __no_sanitize_address __attribute__((no_sanitize_address))
 299 #endif
 300
 301 #if GCC_VERSION >= 50100
 302 /*
 303  * Mark structures as requiring designated initializers.
 304  * https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
 305  */
 306 #define __designated_init __attribute__((designated_init))
 307 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 308 #endif
 309
 310 #if !defined(__noclone)
 311 #define __noclone       /* not needed */
 312 #endif
 313
 314 #if !defined(__no_sanitize_address)
 315 #define __no_sanitize_address
 316 #endif
 317
 318 /*
 319  * Turn individual warnings and errors on and off locally, depending
 320  * on version.
 321  */
 322 #define __diag_GCC(version, severity, s) \
 323         __diag_GCC_ ## version(__diag_GCC_ ## severity s)
 324
 325 /* Severity used in pragma directives */
 326 #define __diag_GCC_ignore       ignored
 327 #define __diag_GCC_warn         warning
 328 #define __diag_GCC_error        error
 329
 330 #define __diag_str1(s)          #s
 331 #define __diag_str(s)           __diag_str1(s)
 332 #define __diag(s)               _Pragma(__diag_str(GCC diagnostic s))
 333
 334 #if GCC_VERSION >= 80000
 335 #define __diag_GCC_8(s)         __diag(s)
 336 #else
 337 #define __diag_GCC_8(s)
 338 #endif