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     __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  */
 118 typedef int (*initcall_t)(void);
 119 typedef void (*exitcall_t)(void);
 120
 121 extern initcall_t __con_initcall_start[], __con_initcall_end[];
 122 extern initcall_t __security_initcall_start[], __security_initcall_end[];
 123
 124 /* Used for contructor calls. */
 125 typedef void (*ctor_fn_t)(void);
 126
 127 /* Defined in init/main.c */
 128 extern int do_one_initcall(initcall_t fn);
 129 extern char __initdata boot_command_line[];
 130 extern char *saved_command_line;
 131 extern unsigned int reset_devices;
 132
 133 /* used by init/main.c */
 134 void setup_arch(char **);
 135 void prepare_namespace(void);
 136 void __init load_default_modules(void);
 137 int __init init_rootfs(void);
 138
 139 #ifdef CONFIG_DEBUG_RODATA
 140 void mark_rodata_ro(void);
 141 #endif
 142
 143 extern void (*late_time_init)(void);
 144
 145 extern 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
 230 struct 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 */
 279 void __init parse_early_param(void);
 280 void __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 */