include/linux/init.h

   1 #ifndef _LINUX_INIT_H
   2 #define _LINUX_INIT_H
   3
   4 #include <linux/compiler.h>
   5 #include <linux/types.h>
   6
   7 /* These macros are used to mark some functions or
   8  * initialized data (doesn't apply to uninitialized data)
   9  * as `initialization' functions. The kernel can take this
  10  * as hint that the function is used only during the initialization
  11  * phase and free up used memory resources after
  12  *
  13  * Usage:
  14  * For functions:
  15  *
  16  * You should add __init immediately before the function name, like:
  17  *
  18  * static void __init initme(int x, int y)
  19  * {
  20  *    extern int z; z = x * y;
  21  * }
  22  *
  23  * If the function has a prototype somewhere, you can also add
  24  * __init between closing brace of the prototype and semicolon:
  25  *
  26  * extern int initialize_foobar_device(int, int, int) __init;
  27  *
  28  * For initialized data:
  29  * You should insert __initdata or __initconst between the variable name
  30  * and equal sign followed by value, e.g.:
  31  *
  32  * static int init_variable __initdata = 0;
  33  * static const char linux_logo[] __initconst = { 0x32, 0x36, ... };
  34  *
  35  * Don't forget to initialize data not at file scope, i.e. within a function,
  36  * as gcc otherwise puts the data into the bss section and not into the init
  37  * section.
  38  */
  39
  40 /* These are for everybody (although not all archs will actually
  41    discard it in modules) */
  42 #define __init          __section(.init.text) __cold notrace
  43 #define __initdata      __section(.init.data)
  44 #define __initconst     __section(.init.rodata)
  45 #define __exitdata      __section(.exit.data)
  46 #define __exit_call     __used __section(.exitcall.exit)
  47
  48 /*
  49  * modpost check for section mismatches during the kernel build.
  50  * A section mismatch happens when there are references from a
  51  * code or data section to an init section (both code or data).
  52  * The init sections are (for most archs) discarded by the kernel
  53  * when early init has completed so all such references are potential bugs.
  54  * For exit sections the same issue exists.
  55  *
  56  * The following markers are used for the cases where the reference to
  57  * the *init / *exit section (code or data) is valid and will teach
  58  * modpost not to issue a warning.  Intended semantics is that a code or
  59  * data tagged __ref* can reference code or data from init section without
  60  * producing a warning (of course, no warning does not mean code is
  61  * correct, so optimally document why the __ref is needed and why it's OK).
  62  *
  63  * The markers follow same syntax rules as __init / __initdata.
  64  */
  65 #define __ref            __section(.ref.text) noinline
  66 #define __refdata        __section(.ref.data)
  67 #define __refconst       __section(.ref.rodata)
  68
  69 #ifdef MODULE
  70 #define __exitused
  71 #else
  72 #define __exitused  __used
  73 #endif
  74
  75 #define __exit          __section(.exit.text) __exitused __cold notrace
  76
  77 /* Used for MEMORY_HOTPLUG */
  78 #define __meminit        __section(.meminit.text) __cold notrace
  79 #define __meminitdata    __section(.meminit.data)
  80 #define __meminitconst   __section(.meminit.rodata)
  81 #define __memexit        __section(.memexit.text) __exitused __cold notrace
  82 #define __memexitdata    __section(.memexit.data)
  83 #define __memexitconst   __section(.memexit.rodata)
  84
  85 /* For assembly routines */
  86 #define __HEAD          .section        ".head.text","ax"
  87 #define __INIT          .section        ".init.text","ax"
  88 #define __FINIT         .previous
  89
  90 #define __INITDATA      .section        ".init.data","aw",%progbits
  91 #define __INITRODATA    .section        ".init.rodata","a",%progbits
  92 #define __FINITDATA     .previous
  93
  94 #define __MEMINIT        .section       ".meminit.text", "ax"
  95 #define __MEMINITDATA    .section       ".meminit.data", "aw"
  96 #define __MEMINITRODATA  .section       ".meminit.rodata", "a"
  97
  98 /* silence warnings when references are OK */
  99 #define __REF            .section       ".ref.text", "ax"
 100 #define __REFDATA        .section       ".ref.data", "aw"
 101 #define __REFCONST       .section       ".ref.rodata", "a"
 102
 103 #ifndef __ASSEMBLY__
 104 /*
 105  * Used for initialization calls..
 106  */
 107 typedef int (*initcall_t)(void);
 108 typedef void (*exitcall_t)(void);
 109
 110 extern initcall_t __con_initcall_start[], __con_initcall_end[];
 111 extern initcall_t __security_initcall_start[], __security_initcall_end[];
 112
 113 /* Used for contructor calls. */
 114 typedef void (*ctor_fn_t)(void);
 115
 116 /* Defined in init/main.c */
 117 extern int do_one_initcall(initcall_t fn);
 118 extern char __initdata boot_command_line[];
 119 extern char *saved_command_line;
 120 extern unsigned int reset_devices;
 121
 122 /* used by init/main.c */
 123 void setup_arch(char **);
 124 void prepare_namespace(void);
 125 void __init load_default_modules(void);
 126 int __init init_rootfs(void);
 127
 128 #ifdef CONFIG_DEBUG_RODATA
 129 void mark_rodata_ro(void);
 130 #endif
 131
 132 extern void (*late_time_init)(void);
 133
 134 extern bool initcall_debug;
 135
 136 #endif
 137
 138 #ifndef MODULE
 139
 140 #ifndef __ASSEMBLY__
 141
 142 #ifdef CONFIG_LTO
 143 /* Work around a LTO gcc problem: when there is no reference to a variable
 144  * in a module it will be moved to the end of the program. This causes
 145  * reordering of initcalls which the kernel does not like.
 146  * Add a dummy reference function to avoid this. The function is
 147  * deleted by the linker.
 148  */
 149 #define LTO_REFERENCE_INITCALL(x) \
 150         ; /* yes this is needed */                      \
 151         static __used __exit void *reference_##x(void)  \
 152         {                                               \
 153                 return &x;                              \
 154         }
 155 #else
 156 #define LTO_REFERENCE_INITCALL(x)
 157 #endif
 158
 159 /* initcalls are now grouped by functionality into separate
 160  * subsections. Ordering inside the subsections is determined
 161  * by link order.
 162  * For backwards compatibility, initcall() puts the call in
 163  * the device init subsection.
 164  *
 165  * The `id' arg to __define_initcall() is needed so that multiple initcalls
 166  * can point at the same handler without causing duplicate-symbol build errors.
 167  */
 168
 169 #define __define_initcall(fn, id) \
 170         static initcall_t __initcall_##fn##id __used \
 171         __attribute__((__section__(".initcall" #id ".init"))) = fn; \
 172         LTO_REFERENCE_INITCALL(__initcall_##fn##id)
 173
 174 /*
 175  * Early initcalls run before initializing SMP.
 176  *
 177  * Only for built-in code, not modules.
 178  */
 179 #define early_initcall(fn)              __define_initcall(fn, early)
 180
 181 /*
 182  * A "pure" initcall has no dependencies on anything else, and purely
 183  * initializes variables that couldn't be statically initialized.
 184  *
 185  * This only exists for built-in code, not for modules.
 186  * Keep main.c:initcall_level_names[] in sync.
 187  */
 188 #define pure_initcall(fn)               __define_initcall(fn, 0)
 189
 190 #define core_initcall(fn)               __define_initcall(fn, 1)
 191 #define core_initcall_sync(fn)          __define_initcall(fn, 1s)
 192 #define postcore_initcall(fn)           __define_initcall(fn, 2)
 193 #define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
 194 #define arch_initcall(fn)               __define_initcall(fn, 3)
 195 #define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
 196 #define subsys_initcall(fn)             __define_initcall(fn, 4)
 197 #define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
 198 #define fs_initcall(fn)                 __define_initcall(fn, 5)
 199 #define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
 200 #define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
 201 #define device_initcall(fn)             __define_initcall(fn, 6)
 202 #define device_initcall_sync(fn)        __define_initcall(fn, 6s)
 203 #define late_initcall(fn)               __define_initcall(fn, 7)
 204 #define late_initcall_sync(fn)          __define_initcall(fn, 7s)
 205
 206 #define __initcall(fn) device_initcall(fn)
 207
 208 #define __exitcall(fn) \
 209         static exitcall_t __exitcall_##fn __exit_call = fn
 210
 211 #define console_initcall(fn) \
 212         static initcall_t __initcall_##fn \
 213         __used __section(.con_initcall.init) = fn
 214
 215 #define security_initcall(fn) \
 216         static initcall_t __initcall_##fn \
 217         __used __section(.security_initcall.init) = fn
 218
 219 struct obs_kernel_param {
 220         const char *str;
 221         int (*setup_func)(char *);
 222         int early;
 223 };
 224
 225 /*
 226  * Only for really core code.  See moduleparam.h for the normal way.
 227  *
 228  * Force the alignment so the compiler doesn't space elements of the
 229  * obs_kernel_param "array" too far apart in .init.setup.
 230  */
 231 #define __setup_param(str, unique_id, fn, early)                        \
 232         static const char __setup_str_##unique_id[] __initconst         \
 233                 __aligned(1) = str;                                     \
 234         static struct obs_kernel_param __setup_##unique_id              \
 235                 __used __section(.init.setup)                           \
 236                 __attribute__((aligned((sizeof(long)))))                \
 237                 = { __setup_str_##unique_id, fn, early }
 238
 239 #define __setup(str, fn)                                                \
 240         __setup_param(str, fn, fn, 0)
 241
 242 /*
 243  * NOTE: fn is as per module_param, not __setup!
 244  * Emits warning if fn returns non-zero.
 245  */
 246 #define early_param(str, fn)                                            \
 247         __setup_param(str, fn, fn, 1)
 248
 249 #define early_param_on_off(str_on, str_off, var, config)                \
 250                                                                         \
 251         int var = IS_ENABLED(config);                                   \
 252                                                                         \
 253         static int __init parse_##var##_on(char *arg)                   \
 254         {                                                               \
 255                 var = 1;                                                \
 256                 return 0;                                               \
 257         }                                                               \
 258         __setup_param(str_on, parse_##var##_on, parse_##var##_on, 1);   \
 259                                                                         \
 260         static int __init parse_##var##_off(char *arg)                  \
 261         {                                                               \
 262                 var = 0;                                                \
 263                 return 0;                                               \
 264         }                                                               \
 265         __setup_param(str_off, parse_##var##_off, parse_##var##_off, 1)
 266
 267 /* Relies on boot_command_line being set */
 268 void __init parse_early_param(void);
 269 void __init parse_early_options(char *cmdline);
 270 #endif /* __ASSEMBLY__ */
 271
 272 #else /* MODULE */
 273
 274 #define __setup_param(str, unique_id, fn)       /* nothing */
 275 #define __setup(str, func)                      /* nothing */
 276 #endif
 277
 278 /* Data marked not to be saved by software suspend */
 279 #define __nosavedata __section(.data..nosave)
 280
 281 #ifdef MODULE
 282 #define __exit_p(x) x
 283 #else
 284 #define __exit_p(x) NULL
 285 #endif
 286
 287 #endif /* _LINUX_INIT_H */