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#ifdef MODULE
  81#define __exitused
  82#else
  83#define __exitused  __used
  84#endif
  85
  86#define __exit          __section(.exit.text) __exitused __cold notrace
  87
  88/* Used for MEMORY_HOTPLUG */
  89#define __meminit        __section(.meminit.text) __cold notrace
  90#define __meminitdata    __section(.meminit.data)
  91#define __meminitconst   __constsection(.meminit.rodata)
  92#define __memexit        __section(.memexit.text) __exitused __cold notrace
  93#define __memexitdata    __section(.memexit.data)
  94#define __memexitconst   __constsection(.memexit.rodata)
  95
  96/* For assembly routines */
  97#define __HEAD          .section        ".head.text","ax"
  98#define __INIT          .section        ".init.text","ax"
  99#define __FINIT         .previous
 100
 101#define __INITDATA      .section        ".init.data","aw",%progbits
 102#define __INITRODATA    .section        ".init.rodata","a",%progbits
 103#define __FINITDATA     .previous
 104
 105#define __MEMINIT        .section       ".meminit.text", "ax"
 106#define __MEMINITDATA    .section       ".meminit.data", "aw"
 107#define __MEMINITRODATA  .section       ".meminit.rodata", "a"
 108
 109/* silence warnings when references are OK */
 110#define __REF            .section       ".ref.text", "ax"
 111#define __REFDATA        .section       ".ref.data", "aw"
 112#define __REFCONST       .section       ".ref.rodata", "a"
 113
 114#ifndef __ASSEMBLY__
 115/*
 116 * Used for initialization calls..
 117 */
 118typedef int (*initcall_t)(void);
 119typedef void (*exitcall_t)(void);
 120
 121extern initcall_t __con_initcall_start[], __con_initcall_end[];
 122extern initcall_t __security_initcall_start[], __security_initcall_end[];
 123
 124/* Used for contructor calls. */
 125typedef void (*ctor_fn_t)(void);
 126
 127/* Defined in init/main.c */
 128extern int do_one_initcall(initcall_t fn);
 129extern char __initdata boot_command_line[];
 130extern char *saved_command_line;
 131extern unsigned int reset_devices;
 132
 133/* used by init/main.c */
 134void setup_arch(char **);
 135void prepare_namespace(void);
 136void __init load_default_modules(void);
 137int __init init_rootfs(void);
 138
 139#ifdef CONFIG_DEBUG_RODATA
 140void mark_rodata_ro(void);
 141#endif
 142
 143extern void (*late_time_init)(void);
 144
 145extern bool initcall_debug;
 146
 147#endif
 148  
 149#ifndef MODULE
 150
 151#ifndef __ASSEMBLY__
 152
 153#ifdef CONFIG_LTO
 154/* Work around a LTO gcc problem: when there is no reference to a variable
 155 * in a module it will be moved to the end of the program. This causes
 156 * reordering of initcalls which the kernel does not like.
 157 * Add a dummy reference function to avoid this. The function is
 158 * deleted by the linker.
 159 */
 160#define LTO_REFERENCE_INITCALL(x) \
 161        ; /* yes this is needed */                      \
 162        static __used __exit void *reference_##x(void)  \
 163        {                                               \
 164                return &x;                              \
 165        }
 166#else
 167#define LTO_REFERENCE_INITCALL(x)
 168#endif
 169
 170/* initcalls are now grouped by functionality into separate 
 171 * subsections. Ordering inside the subsections is determined
 172 * by link order. 
 173 * For backwards compatibility, initcall() puts the call in 
 174 * the device init subsection.
 175 *
 176 * The `id' arg to __define_initcall() is needed so that multiple initcalls
 177 * can point at the same handler without causing duplicate-symbol build errors.
 178 */
 179
 180#define __define_initcall(fn, id) \
 181        static initcall_t __initcall_##fn##id __used \
 182        __attribute__((__section__(".initcall" #id ".init"))) = fn; \
 183        LTO_REFERENCE_INITCALL(__initcall_##fn##id)
 184
 185/*
 186 * Early initcalls run before initializing SMP.
 187 *
 188 * Only for built-in code, not modules.
 189 */
 190#define early_initcall(fn)              __define_initcall(fn, early)
 191
 192/*
 193 * A "pure" initcall has no dependencies on anything else, and purely
 194 * initializes variables that couldn't be statically initialized.
 195 *
 196 * This only exists for built-in code, not for modules.
 197 * Keep main.c:initcall_level_names[] in sync.
 198 */
 199#define pure_initcall(fn)               __define_initcall(fn, 0)
 200
 201#define core_initcall(fn)               __define_initcall(fn, 1)
 202#define core_initcall_sync(fn)          __define_initcall(fn, 1s)
 203#define postcore_initcall(fn)           __define_initcall(fn, 2)
 204#define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
 205#define arch_initcall(fn)               __define_initcall(fn, 3)
 206#define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
 207#define subsys_initcall(fn)             __define_initcall(fn, 4)
 208#define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
 209#define fs_initcall(fn)                 __define_initcall(fn, 5)
 210#define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
 211#define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
 212#define device_initcall(fn)             __define_initcall(fn, 6)
 213#define device_initcall_sync(fn)        __define_initcall(fn, 6s)
 214#define late_initcall(fn)               __define_initcall(fn, 7)
 215#define late_initcall_sync(fn)          __define_initcall(fn, 7s)
 216
 217#define __initcall(fn) device_initcall(fn)
 218
 219#define __exitcall(fn) \
 220        static exitcall_t __exitcall_##fn __exit_call = fn
 221
 222#define console_initcall(fn) \
 223        static initcall_t __initcall_##fn \
 224        __used __section(.con_initcall.init) = fn
 225
 226#define security_initcall(fn) \
 227        static initcall_t __initcall_##fn \
 228        __used __section(.security_initcall.init) = fn
 229
 230struct obs_kernel_param {
 231        const char *str;
 232        int (*setup_func)(char *);
 233        int early;
 234};
 235
 236/*
 237 * Only for really core code.  See moduleparam.h for the normal way.
 238 *
 239 * Force the alignment so the compiler doesn't space elements of the
 240 * obs_kernel_param "array" too far apart in .init.setup.
 241 */
 242#define __setup_param(str, unique_id, fn, early)                        \
 243        static const char __setup_str_##unique_id[] __initconst         \
 244                __aligned(1) = str;                                     \
 245        static struct obs_kernel_param __setup_##unique_id              \
 246                __used __section(.init.setup)                           \
 247                __attribute__((aligned((sizeof(long)))))                \
 248                = { __setup_str_##unique_id, fn, early }
 249
 250#define __setup(str, fn)                                                \
 251        __setup_param(str, fn, fn, 0)
 252
 253/*
 254 * NOTE: fn is as per module_param, not __setup!
 255 * Emits warning if fn returns non-zero.
 256 */
 257#define early_param(str, fn)                                            \
 258        __setup_param(str, fn, fn, 1)
 259
 260#define early_param_on_off(str_on, str_off, var, config)                \
 261                                                                        \
 262        int var = IS_ENABLED(config);                                   \
 263                                                                        \
 264        static int __init parse_##var##_on(char *arg)                   \
 265        {                                                               \
 266                var = 1;                                                \
 267                return 0;                                               \
 268        }                                                               \
 269        __setup_param(str_on, parse_##var##_on, parse_##var##_on, 1);   \
 270                                                                        \
 271        static int __init parse_##var##_off(char *arg)                  \
 272        {                                                               \
 273                var = 0;                                                \
 274                return 0;                                               \
 275        }                                                               \
 276        __setup_param(str_off, parse_##var##_off, parse_##var##_off, 1)
 277
 278/* Relies on boot_command_line being set */
 279void __init parse_early_param(void);
 280void __init parse_early_options(char *cmdline);
 281#endif /* __ASSEMBLY__ */
 282
 283#else /* MODULE */
 284
 285#define __setup_param(str, unique_id, fn)       /* nothing */
 286#define __setup(str, func)                      /* nothing */
 287#endif
 288
 289/* Data marked not to be saved by software suspend */
 290#define __nosavedata __section(.data..nosave)
 291
 292#ifdef MODULE
 293#define __exit_p(x) x
 294#else
 295#define __exit_p(x) NULL
 296#endif
 297
 298#endif /* _LINUX_INIT_H */
 299