linux/include/linux/init.h
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   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     __constsection(.init.rodata)
  45#define __exitdata      __section(.exit.data)
  46#define __exit_call     __used __section(.exitcall.exit)
  47
  48/*
  49 * Some architecture have tool chains which do not handle rodata attributes
  50 * correctly. For those disable special sections for const, so that other
  51 * architectures can annotate correctly.
  52 */
  53#ifdef CONFIG_BROKEN_RODATA
  54#define __constsection(x)
  55#else
  56#define __constsection(x) __section(x)
  57#endif
  58
  59/*
  60 * modpost check for section mismatches during the kernel build.
  61 * A section mismatch happens when there are references from a
  62 * code or data section to an init section (both code or data).
  63 * The init sections are (for most archs) discarded by the kernel
  64 * when early init has completed so all such references are potential bugs.
  65 * For exit sections the same issue exists.
  66 *
  67 * The following markers are used for the cases where the reference to
  68 * the *init / *exit section (code or data) is valid and will teach
  69 * modpost not to issue a warning.  Intended semantics is that a code or
  70 * data tagged __ref* can reference code or data from init section without
  71 * producing a warning (of course, no warning does not mean code is
  72 * correct, so optimally document why the __ref is needed and why it's OK).
  73 *
  74 * The markers follow same syntax rules as __init / __initdata.
  75 */
  76#define __ref            __section(.ref.text) noinline
  77#define __refdata        __section(.ref.data)
  78#define __refconst       __constsection(.ref.rodata)
  79
  80/* compatibility defines */
  81#define __init_refok     __ref
  82#define __initdata_refok __refdata
  83#define __exit_refok     __ref
  84
  85
  86#ifdef MODULE
  87#define __exitused
  88#else
  89#define __exitused  __used
  90#endif
  91
  92#define __exit          __section(.exit.text) __exitused __cold notrace
  93
  94/* temporary, until all users are removed */
  95#define __cpuinit
  96#define __cpuinitdata
  97#define __cpuinitconst
  98#define __cpuexit
  99#define __cpuexitdata
 100#define __cpuexitconst
 101
 102/* Used for MEMORY_HOTPLUG */
 103#define __meminit        __section(.meminit.text) __cold notrace
 104#define __meminitdata    __section(.meminit.data)
 105#define __meminitconst   __constsection(.meminit.rodata)
 106#define __memexit        __section(.memexit.text) __exitused __cold notrace
 107#define __memexitdata    __section(.memexit.data)
 108#define __memexitconst   __constsection(.memexit.rodata)
 109
 110/* For assembly routines */
 111#define __HEAD          .section        ".head.text","ax"
 112#define __INIT          .section        ".init.text","ax"
 113#define __FINIT         .previous
 114
 115#define __INITDATA      .section        ".init.data","aw",%progbits
 116#define __INITRODATA    .section        ".init.rodata","a",%progbits
 117#define __FINITDATA     .previous
 118
 119/* temporary, until all users are removed */
 120#define __CPUINIT
 121
 122#define __MEMINIT        .section       ".meminit.text", "ax"
 123#define __MEMINITDATA    .section       ".meminit.data", "aw"
 124#define __MEMINITRODATA  .section       ".meminit.rodata", "a"
 125
 126/* silence warnings when references are OK */
 127#define __REF            .section       ".ref.text", "ax"
 128#define __REFDATA        .section       ".ref.data", "aw"
 129#define __REFCONST       .section       ".ref.rodata", "a"
 130
 131#ifndef __ASSEMBLY__
 132/*
 133 * Used for initialization calls..
 134 */
 135typedef int (*initcall_t)(void);
 136typedef void (*exitcall_t)(void);
 137
 138extern initcall_t __con_initcall_start[], __con_initcall_end[];
 139extern initcall_t __security_initcall_start[], __security_initcall_end[];
 140
 141/* Used for contructor calls. */
 142typedef void (*ctor_fn_t)(void);
 143
 144/* Defined in init/main.c */
 145extern int do_one_initcall(initcall_t fn);
 146extern char __initdata boot_command_line[];
 147extern char *saved_command_line;
 148extern unsigned int reset_devices;
 149
 150/* used by init/main.c */
 151void setup_arch(char **);
 152void prepare_namespace(void);
 153void __init load_default_modules(void);
 154int __init init_rootfs(void);
 155
 156extern void (*late_time_init)(void);
 157
 158extern bool initcall_debug;
 159
 160#endif
 161  
 162#ifndef MODULE
 163
 164#ifndef __ASSEMBLY__
 165
 166#ifdef CONFIG_LTO
 167/* Work around a LTO gcc problem: when there is no reference to a variable
 168 * in a module it will be moved to the end of the program. This causes
 169 * reordering of initcalls which the kernel does not like.
 170 * Add a dummy reference function to avoid this. The function is
 171 * deleted by the linker.
 172 */
 173#define LTO_REFERENCE_INITCALL(x) \
 174        ; /* yes this is needed */                      \
 175        static __used __exit void *reference_##x(void)  \
 176        {                                               \
 177                return &x;                              \
 178        }
 179#else
 180#define LTO_REFERENCE_INITCALL(x)
 181#endif
 182
 183/* initcalls are now grouped by functionality into separate 
 184 * subsections. Ordering inside the subsections is determined
 185 * by link order. 
 186 * For backwards compatibility, initcall() puts the call in 
 187 * the device init subsection.
 188 *
 189 * The `id' arg to __define_initcall() is needed so that multiple initcalls
 190 * can point at the same handler without causing duplicate-symbol build errors.
 191 */
 192
 193#define __define_initcall(fn, id) \
 194        static initcall_t __initcall_##fn##id __used \
 195        __attribute__((__section__(".initcall" #id ".init"))) = fn; \
 196        LTO_REFERENCE_INITCALL(__initcall_##fn##id)
 197
 198/*
 199 * Early initcalls run before initializing SMP.
 200 *
 201 * Only for built-in code, not modules.
 202 */
 203#define early_initcall(fn)              __define_initcall(fn, early)
 204
 205/*
 206 * A "pure" initcall has no dependencies on anything else, and purely
 207 * initializes variables that couldn't be statically initialized.
 208 *
 209 * This only exists for built-in code, not for modules.
 210 * Keep main.c:initcall_level_names[] in sync.
 211 */
 212#define pure_initcall(fn)               __define_initcall(fn, 0)
 213
 214#define core_initcall(fn)               __define_initcall(fn, 1)
 215#define core_initcall_sync(fn)          __define_initcall(fn, 1s)
 216#define postcore_initcall(fn)           __define_initcall(fn, 2)
 217#define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
 218#define arch_initcall(fn)               __define_initcall(fn, 3)
 219#define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
 220#define subsys_initcall(fn)             __define_initcall(fn, 4)
 221#define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
 222#define fs_initcall(fn)                 __define_initcall(fn, 5)
 223#define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
 224#define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
 225#define device_initcall(fn)             __define_initcall(fn, 6)
 226#define device_initcall_sync(fn)        __define_initcall(fn, 6s)
 227#define late_initcall(fn)               __define_initcall(fn, 7)
 228#define late_initcall_sync(fn)          __define_initcall(fn, 7s)
 229
 230#define __initcall(fn) device_initcall(fn)
 231
 232#define __exitcall(fn) \
 233        static exitcall_t __exitcall_##fn __exit_call = fn
 234
 235#define console_initcall(fn) \
 236        static initcall_t __initcall_##fn \
 237        __used __section(.con_initcall.init) = fn
 238
 239#define security_initcall(fn) \
 240        static initcall_t __initcall_##fn \
 241        __used __section(.security_initcall.init) = fn
 242
 243struct obs_kernel_param {
 244        const char *str;
 245        int (*setup_func)(char *);
 246        int early;
 247};
 248
 249/*
 250 * Only for really core code.  See moduleparam.h for the normal way.
 251 *
 252 * Force the alignment so the compiler doesn't space elements of the
 253 * obs_kernel_param "array" too far apart in .init.setup.
 254 */
 255#define __setup_param(str, unique_id, fn, early)                        \
 256        static const char __setup_str_##unique_id[] __initconst \
 257                __aligned(1) = str; \
 258        static struct obs_kernel_param __setup_##unique_id      \
 259                __used __section(.init.setup)                   \
 260                __attribute__((aligned((sizeof(long)))))        \
 261                = { __setup_str_##unique_id, fn, early }
 262
 263#define __setup(str, fn)                                        \
 264        __setup_param(str, fn, fn, 0)
 265
 266/* NOTE: fn is as per module_param, not __setup!  Emits warning if fn
 267 * returns non-zero. */
 268#define early_param(str, fn)                                    \
 269        __setup_param(str, fn, fn, 1)
 270
 271/* Relies on boot_command_line being set */
 272void __init parse_early_param(void);
 273void __init parse_early_options(char *cmdline);
 274#endif /* __ASSEMBLY__ */
 275
 276/**
 277 * module_init() - driver initialization entry point
 278 * @x: function to be run at kernel boot time or module insertion
 279 * 
 280 * module_init() will either be called during do_initcalls() (if
 281 * builtin) or at module insertion time (if a module).  There can only
 282 * be one per module.
 283 */
 284#define module_init(x)  __initcall(x);
 285
 286/**
 287 * module_exit() - driver exit entry point
 288 * @x: function to be run when driver is removed
 289 * 
 290 * module_exit() will wrap the driver clean-up code
 291 * with cleanup_module() when used with rmmod when
 292 * the driver is a module.  If the driver is statically
 293 * compiled into the kernel, module_exit() has no effect.
 294 * There can only be one per module.
 295 */
 296#define module_exit(x)  __exitcall(x);
 297
 298#else /* MODULE */
 299
 300/*
 301 * In most cases loadable modules do not need custom
 302 * initcall levels. There are still some valid cases where
 303 * a driver may be needed early if built in, and does not
 304 * matter when built as a loadable module. Like bus
 305 * snooping debug drivers.
 306 */
 307#define early_initcall(fn)              module_init(fn)
 308#define core_initcall(fn)               module_init(fn)
 309#define core_initcall_sync(fn)          module_init(fn)
 310#define postcore_initcall(fn)           module_init(fn)
 311#define postcore_initcall_sync(fn)      module_init(fn)
 312#define arch_initcall(fn)               module_init(fn)
 313#define subsys_initcall(fn)             module_init(fn)
 314#define subsys_initcall_sync(fn)        module_init(fn)
 315#define fs_initcall(fn)                 module_init(fn)
 316#define fs_initcall_sync(fn)            module_init(fn)
 317#define rootfs_initcall(fn)             module_init(fn)
 318#define device_initcall(fn)             module_init(fn)
 319#define device_initcall_sync(fn)        module_init(fn)
 320#define late_initcall(fn)               module_init(fn)
 321#define late_initcall_sync(fn)          module_init(fn)
 322
 323#define console_initcall(fn)            module_init(fn)
 324#define security_initcall(fn)           module_init(fn)
 325
 326/* Each module must use one module_init(). */
 327#define module_init(initfn)                                     \
 328        static inline initcall_t __inittest(void)               \
 329        { return initfn; }                                      \
 330        int init_module(void) __attribute__((alias(#initfn)));
 331
 332/* This is only required if you want to be unloadable. */
 333#define module_exit(exitfn)                                     \
 334        static inline exitcall_t __exittest(void)               \
 335        { return exitfn; }                                      \
 336        void cleanup_module(void) __attribute__((alias(#exitfn)));
 337
 338#define __setup_param(str, unique_id, fn)       /* nothing */
 339#define __setup(str, func)                      /* nothing */
 340#endif
 341
 342/* Data marked not to be saved by software suspend */
 343#define __nosavedata __section(.data..nosave)
 344
 345/* This means "can be init if no module support, otherwise module load
 346   may call it." */
 347#ifdef CONFIG_MODULES
 348#define __init_or_module
 349#define __initdata_or_module
 350#define __initconst_or_module
 351#define __INIT_OR_MODULE        .text
 352#define __INITDATA_OR_MODULE    .data
 353#define __INITRODATA_OR_MODULE  .section ".rodata","a",%progbits
 354#else
 355#define __init_or_module __init
 356#define __initdata_or_module __initdata
 357#define __initconst_or_module __initconst
 358#define __INIT_OR_MODULE __INIT
 359#define __INITDATA_OR_MODULE __INITDATA
 360#define __INITRODATA_OR_MODULE __INITRODATA
 361#endif /*CONFIG_MODULES*/
 362
 363#ifdef MODULE
 364#define __exit_p(x) x
 365#else
 366#define __exit_p(x) NULL
 367#endif
 368
 369#endif /* _LINUX_INIT_H */
 370
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