include/linux/init.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_INIT_H
   3 #define _LINUX_INIT_H
   4
   5 #include <linux/compiler.h>
   6 #include <linux/types.h>
   7
   8 /* These macros are used to mark some functions or
   9  * initialized data (doesn't apply to uninitialized data)
  10  * as `initialization' functions. The kernel can take this
  11  * as hint that the function is used only during the initialization
  12  * phase and free up used memory resources after
  13  *
  14  * Usage:
  15  * For functions:
  16  *
  17  * You should add __init immediately before the function name, like:
  18  *
  19  * static void __init initme(int x, int y)
  20  * {
  21  *    extern int z; z = x * y;
  22  * }
  23  *
  24  * If the function has a prototype somewhere, you can also add
  25  * __init between closing brace of the prototype and semicolon:
  26  *
  27  * extern int initialize_foobar_device(int, int, int) __init;
  28  *
  29  * For initialized data:
  30  * You should insert __initdata or __initconst between the variable name
  31  * and equal sign followed by value, e.g.:
  32  *
  33  * static int init_variable __initdata = 0;
  34  * static const char linux_logo[] __initconst = { 0x32, 0x36, ... };
  35  *
  36  * Don't forget to initialize data not at file scope, i.e. within a function,
  37  * as gcc otherwise puts the data into the bss section and not into the init
  38  * section.
  39  */
  40
  41 /* These are for everybody (although not all archs will actually
  42    discard it in modules) */
  43 #define __init          __section(.init.text) __cold __inittrace __latent_entropy
  44 #define __initdata      __section(.init.data)
  45 #define __initconst     __section(.init.rodata)
  46 #define __exitdata      __section(.exit.data)
  47 #define __exit_call     __used __section(.exitcall.exit)
  48
  49 /*
  50  * modpost check for section mismatches during the kernel build.
  51  * A section mismatch happens when there are references from a
  52  * code or data section to an init section (both code or data).
  53  * The init sections are (for most archs) discarded by the kernel
  54  * when early init has completed so all such references are potential bugs.
  55  * For exit sections the same issue exists.
  56  *
  57  * The following markers are used for the cases where the reference to
  58  * the *init / *exit section (code or data) is valid and will teach
  59  * modpost not to issue a warning.  Intended semantics is that a code or
  60  * data tagged __ref* can reference code or data from init section without
  61  * producing a warning (of course, no warning does not mean code is
  62  * correct, so optimally document why the __ref is needed and why it's OK).
  63  *
  64  * The markers follow same syntax rules as __init / __initdata.
  65  */
  66 #define __ref            __section(.ref.text) noinline
  67 #define __refdata        __section(.ref.data)
  68 #define __refconst       __section(.ref.rodata)
  69
  70 #ifdef MODULE
  71 #define __exitused
  72 #define __inittrace notrace
  73 #else
  74 #define __exitused  __used
  75 #define __inittrace
  76 #endif
  77
  78 #define __exit          __section(.exit.text) __exitused __cold notrace
  79
  80 /* Used for MEMORY_HOTPLUG */
  81 #define __meminit        __section(.meminit.text) __cold notrace \
  82                                                   __latent_entropy
  83 #define __meminitdata    __section(.meminit.data)
  84 #define __meminitconst   __section(.meminit.rodata)
  85 #define __memexit        __section(.memexit.text) __exitused __cold notrace
  86 #define __memexitdata    __section(.memexit.data)
  87 #define __memexitconst   __section(.memexit.rodata)
  88
  89 /* For assembly routines */
  90 #define __HEAD          .section        ".head.text","ax"
  91 #define __INIT          .section        ".init.text","ax"
  92 #define __FINIT         .previous
  93
  94 #define __INITDATA      .section        ".init.data","aw",%progbits
  95 #define __INITRODATA    .section        ".init.rodata","a",%progbits
  96 #define __FINITDATA     .previous
  97
  98 #define __MEMINIT        .section       ".meminit.text", "ax"
  99 #define __MEMINITDATA    .section       ".meminit.data", "aw"
 100 #define __MEMINITRODATA  .section       ".meminit.rodata", "a"
 101
 102 /* silence warnings when references are OK */
 103 #define __REF            .section       ".ref.text", "ax"
 104 #define __REFDATA        .section       ".ref.data", "aw"
 105 #define __REFCONST       .section       ".ref.rodata", "a"
 106
 107 #ifndef __ASSEMBLY__
 108 /*
 109  * Used for initialization calls..
 110  */
 111 typedef int (*initcall_t)(void);
 112 typedef void (*exitcall_t)(void);
 113
 114 extern initcall_t __con_initcall_start[], __con_initcall_end[];
 115 extern initcall_t __security_initcall_start[], __security_initcall_end[];
 116
 117 /* Used for contructor calls. */
 118 typedef void (*ctor_fn_t)(void);
 119
 120 /* Defined in init/main.c */
 121 extern int do_one_initcall(initcall_t fn);
 122 extern char __initdata boot_command_line[];
 123 extern char *saved_command_line;
 124 extern unsigned int reset_devices;
 125
 126 /* used by init/main.c */
 127 void setup_arch(char **);
 128 void prepare_namespace(void);
 129 void __init load_default_modules(void);
 130 int __init init_rootfs(void);
 131
 132 #if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX)
 133 extern bool rodata_enabled;
 134 #endif
 135 #ifdef CONFIG_STRICT_KERNEL_RWX
 136 void mark_rodata_ro(void);
 137 #endif
 138
 139 extern void (*late_time_init)(void);
 140
 141 extern bool initcall_debug;
 142
 143 #endif
 144
 145 #ifndef MODULE
 146
 147 #ifndef __ASSEMBLY__
 148
 149 /*
 150  * initcalls are now grouped by functionality into separate
 151  * subsections. Ordering inside the subsections is determined
 152  * by link order.
 153  * For backwards compatibility, initcall() puts the call in
 154  * the device init subsection.
 155  *
 156  * The `id' arg to __define_initcall() is needed so that multiple initcalls
 157  * can point at the same handler without causing duplicate-symbol build errors.
 158  *
 159  * Initcalls are run by placing pointers in initcall sections that the
 160  * kernel iterates at runtime. The linker can do dead code / data elimination
 161  * and remove that completely, so the initcall sections have to be marked
 162  * as KEEP() in the linker script.
 163  */
 164
 165 #define __define_initcall(fn, id) \
 166         static initcall_t __initcall_##fn##id __used \
 167         __attribute__((__section__(".initcall" #id ".init"))) = fn;
 168
 169 /*
 170  * Early initcalls run before initializing SMP.
 171  *
 172  * Only for built-in code, not modules.
 173  */
 174 #define early_initcall(fn)              __define_initcall(fn, early)
 175
 176 /*
 177  * A "pure" initcall has no dependencies on anything else, and purely
 178  * initializes variables that couldn't be statically initialized.
 179  *
 180  * This only exists for built-in code, not for modules.
 181  * Keep main.c:initcall_level_names[] in sync.
 182  */
 183 #define pure_initcall(fn)               __define_initcall(fn, 0)
 184
 185 #define core_initcall(fn)               __define_initcall(fn, 1)
 186 #define core_initcall_sync(fn)          __define_initcall(fn, 1s)
 187 #define postcore_initcall(fn)           __define_initcall(fn, 2)
 188 #define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
 189 #define arch_initcall(fn)               __define_initcall(fn, 3)
 190 #define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
 191 #define subsys_initcall(fn)             __define_initcall(fn, 4)
 192 #define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
 193 #define fs_initcall(fn)                 __define_initcall(fn, 5)
 194 #define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
 195 #define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
 196 #define device_initcall(fn)             __define_initcall(fn, 6)
 197 #define device_initcall_sync(fn)        __define_initcall(fn, 6s)
 198 #define late_initcall(fn)               __define_initcall(fn, 7)
 199 #define late_initcall_sync(fn)          __define_initcall(fn, 7s)
 200
 201 #define __initcall(fn) device_initcall(fn)
 202
 203 #define __exitcall(fn)                                          \
 204         static exitcall_t __exitcall_##fn __exit_call = fn
 205
 206 #define console_initcall(fn)                                    \
 207         static initcall_t __initcall_##fn                       \
 208         __used __section(.con_initcall.init) = fn
 209
 210 #define security_initcall(fn)                                   \
 211         static initcall_t __initcall_##fn                       \
 212         __used __section(.security_initcall.init) = fn
 213
 214 struct obs_kernel_param {
 215         const char *str;
 216         int (*setup_func)(char *);
 217         int early;
 218 };
 219
 220 /*
 221  * Only for really core code.  See moduleparam.h for the normal way.
 222  *
 223  * Force the alignment so the compiler doesn't space elements of the
 224  * obs_kernel_param "array" too far apart in .init.setup.
 225  */
 226 #define __setup_param(str, unique_id, fn, early)                        \
 227         static const char __setup_str_##unique_id[] __initconst         \
 228                 __aligned(1) = str;                                     \
 229         static struct obs_kernel_param __setup_##unique_id              \
 230                 __used __section(.init.setup)                           \
 231                 __attribute__((aligned((sizeof(long)))))                \
 232                 = { __setup_str_##unique_id, fn, early }
 233
 234 #define __setup(str, fn)                                                \
 235         __setup_param(str, fn, fn, 0)
 236
 237 /*
 238  * NOTE: fn is as per module_param, not __setup!
 239  * Emits warning if fn returns non-zero.
 240  */
 241 #define early_param(str, fn)                                            \
 242         __setup_param(str, fn, fn, 1)
 243
 244 #define early_param_on_off(str_on, str_off, var, config)                \
 245                                                                         \
 246         int var = IS_ENABLED(config);                                   \
 247                                                                         \
 248         static int __init parse_##var##_on(char *arg)                   \
 249         {                                                               \
 250                 var = 1;                                                \
 251                 return 0;                                               \
 252         }                                                               \
 253         __setup_param(str_on, parse_##var##_on, parse_##var##_on, 1);   \
 254                                                                         \
 255         static int __init parse_##var##_off(char *arg)                  \
 256         {                                                               \
 257                 var = 0;                                                \
 258                 return 0;                                               \
 259         }                                                               \
 260         __setup_param(str_off, parse_##var##_off, parse_##var##_off, 1)
 261
 262 /* Relies on boot_command_line being set */
 263 void __init parse_early_param(void);
 264 void __init parse_early_options(char *cmdline);
 265 #endif /* __ASSEMBLY__ */
 266
 267 #else /* MODULE */
 268
 269 #define __setup_param(str, unique_id, fn)       /* nothing */
 270 #define __setup(str, func)                      /* nothing */
 271 #endif
 272
 273 /* Data marked not to be saved by software suspend */
 274 #define __nosavedata __section(.data..nosave)
 275
 276 #ifdef MODULE
 277 #define __exit_p(x) x
 278 #else
 279 #define __exit_p(x) NULL
 280 #endif
 281
 282 #endif /* _LINUX_INIT_H */