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 /* Built-in __init functions needn't be compiled with retpoline */
   9 #if defined(__noretpoline) && !defined(MODULE)
  10 #define __noinitretpoline __noretpoline
  11 #else
  12 #define __noinitretpoline
  13 #endif
  14
  15 /* These macros are used to mark some functions or
  16  * initialized data (doesn't apply to uninitialized data)
  17  * as `initialization' functions. The kernel can take this
  18  * as hint that the function is used only during the initialization
  19  * phase and free up used memory resources after
  20  *
  21  * Usage:
  22  * For functions:
  23  *
  24  * You should add __init immediately before the function name, like:
  25  *
  26  * static void __init initme(int x, int y)
  27  * {
  28  *    extern int z; z = x * y;
  29  * }
  30  *
  31  * If the function has a prototype somewhere, you can also add
  32  * __init between closing brace of the prototype and semicolon:
  33  *
  34  * extern int initialize_foobar_device(int, int, int) __init;
  35  *
  36  * For initialized data:
  37  * You should insert __initdata or __initconst between the variable name
  38  * and equal sign followed by value, e.g.:
  39  *
  40  * static int init_variable __initdata = 0;
  41  * static const char linux_logo[] __initconst = { 0x32, 0x36, ... };
  42  *
  43  * Don't forget to initialize data not at file scope, i.e. within a function,
  44  * as gcc otherwise puts the data into the bss section and not into the init
  45  * section.
  46  */
  47
  48 /* These are for everybody (although not all archs will actually
  49    discard it in modules) */
  50 #define __init          __section(.init.text) __cold  __latent_entropy __noinitretpoline
  51 #define __initdata      __section(.init.data)
  52 #define __initconst     __section(.init.rodata)
  53 #define __exitdata      __section(.exit.data)
  54 #define __exit_call     __used __section(.exitcall.exit)
  55
  56 /*
  57  * modpost check for section mismatches during the kernel build.
  58  * A section mismatch happens when there are references from a
  59  * code or data section to an init section (both code or data).
  60  * The init sections are (for most archs) discarded by the kernel
  61  * when early init has completed so all such references are potential bugs.
  62  * For exit sections the same issue exists.
  63  *
  64  * The following markers are used for the cases where the reference to
  65  * the *init / *exit section (code or data) is valid and will teach
  66  * modpost not to issue a warning.  Intended semantics is that a code or
  67  * data tagged __ref* can reference code or data from init section without
  68  * producing a warning (of course, no warning does not mean code is
  69  * correct, so optimally document why the __ref is needed and why it's OK).
  70  *
  71  * The markers follow same syntax rules as __init / __initdata.
  72  */
  73 #define __ref            __section(.ref.text) noinline
  74 #define __refdata        __section(.ref.data)
  75 #define __refconst       __section(.ref.rodata)
  76
  77 #ifdef MODULE
  78 #define __exitused
  79 #else
  80 #define __exitused  __used
  81 #endif
  82
  83 #define __exit          __section(.exit.text) __exitused __cold notrace
  84
  85 /* Used for MEMORY_HOTPLUG */
  86 #define __meminit        __section(.meminit.text) __cold notrace \
  87                                                   __latent_entropy
  88 #define __meminitdata    __section(.meminit.data)
  89 #define __meminitconst   __section(.meminit.rodata)
  90 #define __memexit        __section(.memexit.text) __exitused __cold notrace
  91 #define __memexitdata    __section(.memexit.data)
  92 #define __memexitconst   __section(.memexit.rodata)
  93
  94 /* For assembly routines */
  95 #define __HEAD          .section        ".head.text","ax"
  96 #define __INIT          .section        ".init.text","ax"
  97 #define __FINIT         .previous
  98
  99 #define __INITDATA      .section        ".init.data","aw",%progbits
 100 #define __INITRODATA    .section        ".init.rodata","a",%progbits
 101 #define __FINITDATA     .previous
 102
 103 #define __MEMINIT        .section       ".meminit.text", "ax"
 104 #define __MEMINITDATA    .section       ".meminit.data", "aw"
 105 #define __MEMINITRODATA  .section       ".meminit.rodata", "a"
 106
 107 /* silence warnings when references are OK */
 108 #define __REF            .section       ".ref.text", "ax"
 109 #define __REFDATA        .section       ".ref.data", "aw"
 110 #define __REFCONST       .section       ".ref.rodata", "a"
 111
 112 #ifndef __ASSEMBLY__
 113 /*
 114  * Used for initialization calls..
 115  */
 116 typedef int (*initcall_t)(void);
 117 typedef void (*exitcall_t)(void);
 118
 119 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
 120 typedef int initcall_entry_t;
 121
 122 static inline initcall_t initcall_from_entry(initcall_entry_t *entry)
 123 {
 124         return offset_to_ptr(entry);
 125 }
 126 #else
 127 typedef initcall_t initcall_entry_t;
 128
 129 static inline initcall_t initcall_from_entry(initcall_entry_t *entry)
 130 {
 131         return *entry;
 132 }
 133 #endif
 134
 135 extern initcall_entry_t __con_initcall_start[], __con_initcall_end[];
 136
 137 /* Used for contructor calls. */
 138 typedef void (*ctor_fn_t)(void);
 139
 140 /* Defined in init/main.c */
 141 extern int do_one_initcall(initcall_t fn);
 142 extern char __initdata boot_command_line[];
 143 extern char *saved_command_line;
 144 extern unsigned int reset_devices;
 145
 146 /* used by init/main.c */
 147 void setup_arch(char **);
 148 void prepare_namespace(void);
 149 void __init load_default_modules(void);
 150 int __init init_rootfs(void);
 151
 152 #if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX)
 153 extern bool rodata_enabled;
 154 #endif
 155 #ifdef CONFIG_STRICT_KERNEL_RWX
 156 void mark_rodata_ro(void);
 157 #endif
 158
 159 extern void (*late_time_init)(void);
 160
 161 extern bool initcall_debug;
 162
 163 #endif
 164
 165 #ifndef MODULE
 166
 167 #ifndef __ASSEMBLY__
 168
 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  * Initcalls are run by placing pointers in initcall sections that the
 180  * kernel iterates at runtime. The linker can do dead code / data elimination
 181  * and remove that completely, so the initcall sections have to be marked
 182  * as KEEP() in the linker script.
 183  */
 184
 185 #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
 186 #define ___define_initcall(fn, id, __sec)                       \
 187         __ADDRESSABLE(fn)                                       \
 188         asm(".section   \"" #__sec ".init\", \"a\"      \n"     \
 189         "__initcall_" #fn #id ":                        \n"     \
 190             ".long      " #fn " - .                     \n"     \
 191             ".previous                                  \n");
 192 #else
 193 #define ___define_initcall(fn, id, __sec) \
 194         static initcall_t __initcall_##fn##id __used \
 195                 __attribute__((__section__(#__sec ".init"))) = fn;
 196 #endif
 197
 198 #define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
 199
 200 /*
 201  * Early initcalls run before initializing SMP.
 202  *
 203  * Only for built-in code, not modules.
 204  */
 205 #define early_initcall(fn)              __define_initcall(fn, early)
 206
 207 /*
 208  * A "pure" initcall has no dependencies on anything else, and purely
 209  * initializes variables that couldn't be statically initialized.
 210  *
 211  * This only exists for built-in code, not for modules.
 212  * Keep main.c:initcall_level_names[] in sync.
 213  */
 214 #define pure_initcall(fn)               __define_initcall(fn, 0)
 215
 216 #define core_initcall(fn)               __define_initcall(fn, 1)
 217 #define core_initcall_sync(fn)          __define_initcall(fn, 1s)
 218 #define postcore_initcall(fn)           __define_initcall(fn, 2)
 219 #define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
 220 #define arch_initcall(fn)               __define_initcall(fn, 3)
 221 #define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
 222 #define subsys_initcall(fn)             __define_initcall(fn, 4)
 223 #define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
 224 #define fs_initcall(fn)                 __define_initcall(fn, 5)
 225 #define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
 226 #define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
 227 #define device_initcall(fn)             __define_initcall(fn, 6)
 228 #define device_initcall_sync(fn)        __define_initcall(fn, 6s)
 229 #define late_initcall(fn)               __define_initcall(fn, 7)
 230 #define late_initcall_sync(fn)          __define_initcall(fn, 7s)
 231
 232 #define __initcall(fn) device_initcall(fn)
 233
 234 #define __exitcall(fn)                                          \
 235         static exitcall_t __exitcall_##fn __exit_call = fn
 236
 237 #define console_initcall(fn)    ___define_initcall(fn,, .con_initcall)
 238
 239 struct obs_kernel_param {
 240         const char *str;
 241         int (*setup_func)(char *);
 242         int early;
 243 };
 244
 245 /*
 246  * Only for really core code.  See moduleparam.h for the normal way.
 247  *
 248  * Force the alignment so the compiler doesn't space elements of the
 249  * obs_kernel_param "array" too far apart in .init.setup.
 250  */
 251 #define __setup_param(str, unique_id, fn, early)                        \
 252         static const char __setup_str_##unique_id[] __initconst         \
 253                 __aligned(1) = str;                                     \
 254         static struct obs_kernel_param __setup_##unique_id              \
 255                 __used __section(.init.setup)                           \
 256                 __attribute__((aligned((sizeof(long)))))                \
 257                 = { __setup_str_##unique_id, fn, early }
 258
 259 #define __setup(str, fn)                                                \
 260         __setup_param(str, fn, fn, 0)
 261
 262 /*
 263  * NOTE: fn is as per module_param, not __setup!
 264  * Emits warning if fn returns non-zero.
 265  */
 266 #define early_param(str, fn)                                            \
 267         __setup_param(str, fn, fn, 1)
 268
 269 #define early_param_on_off(str_on, str_off, var, config)                \
 270                                                                         \
 271         int var = IS_ENABLED(config);                                   \
 272                                                                         \
 273         static int __init parse_##var##_on(char *arg)                   \
 274         {                                                               \
 275                 var = 1;                                                \
 276                 return 0;                                               \
 277         }                                                               \
 278         __setup_param(str_on, parse_##var##_on, parse_##var##_on, 1);   \
 279                                                                         \
 280         static int __init parse_##var##_off(char *arg)                  \
 281         {                                                               \
 282                 var = 0;                                                \
 283                 return 0;                                               \
 284         }                                                               \
 285         __setup_param(str_off, parse_##var##_off, parse_##var##_off, 1)
 286
 287 /* Relies on boot_command_line being set */
 288 void __init parse_early_param(void);
 289 void __init parse_early_options(char *cmdline);
 290 #endif /* __ASSEMBLY__ */
 291
 292 #else /* MODULE */
 293
 294 #define __setup_param(str, unique_id, fn)       /* nothing */
 295 #define __setup(str, func)                      /* nothing */
 296 #endif
 297
 298 /* Data marked not to be saved by software suspend */
 299 #define __nosavedata __section(.data..nosave)
 300
 301 #ifdef MODULE
 302 #define __exit_p(x) x
 303 #else
 304 #define __exit_p(x) NULL
 305 #endif
 306
 307 #endif /* _LINUX_INIT_H */