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 /* 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 /* Used for MEMORY_HOTPLUG */
  95 #define __meminit        __section(.meminit.text) __cold notrace
  96 #define __meminitdata    __section(.meminit.data)
  97 #define __meminitconst   __constsection(.meminit.rodata)
  98 #define __memexit        __section(.memexit.text) __exitused __cold notrace
  99 #define __memexitdata    __section(.memexit.data)
 100 #define __memexitconst   __constsection(.memexit.rodata)
 101
 102 /* For assembly routines */
 103 #define __HEAD          .section        ".head.text","ax"
 104 #define __INIT          .section        ".init.text","ax"
 105 #define __FINIT         .previous
 106
 107 #define __INITDATA      .section        ".init.data","aw",%progbits
 108 #define __INITRODATA    .section        ".init.rodata","a",%progbits
 109 #define __FINITDATA     .previous
 110
 111 #define __MEMINIT        .section       ".meminit.text", "ax"
 112 #define __MEMINITDATA    .section       ".meminit.data", "aw"
 113 #define __MEMINITRODATA  .section       ".meminit.rodata", "a"
 114
 115 /* silence warnings when references are OK */
 116 #define __REF            .section       ".ref.text", "ax"
 117 #define __REFDATA        .section       ".ref.data", "aw"
 118 #define __REFCONST       .section       ".ref.rodata", "a"
 119
 120 #ifndef __ASSEMBLY__
 121 /*
 122  * Used for initialization calls..
 123  */
 124 typedef int (*initcall_t)(void);
 125 typedef void (*exitcall_t)(void);
 126
 127 extern initcall_t __con_initcall_start[], __con_initcall_end[];
 128 extern initcall_t __security_initcall_start[], __security_initcall_end[];
 129
 130 /* Used for contructor calls. */
 131 typedef void (*ctor_fn_t)(void);
 132
 133 /* Defined in init/main.c */
 134 extern int do_one_initcall(initcall_t fn);
 135 extern char __initdata boot_command_line[];
 136 extern char *saved_command_line;
 137 extern unsigned int reset_devices;
 138
 139 /* used by init/main.c */
 140 void setup_arch(char **);
 141 void prepare_namespace(void);
 142 void __init load_default_modules(void);
 143 int __init init_rootfs(void);
 144
 145 #ifdef CONFIG_DEBUG_RODATA
 146 void mark_rodata_ro(void);
 147 #endif
 148
 149 extern void (*late_time_init)(void);
 150
 151 extern bool initcall_debug;
 152
 153 #endif
 154
 155 #ifndef MODULE
 156
 157 #ifndef __ASSEMBLY__
 158
 159 #ifdef CONFIG_LTO
 160 /* Work around a LTO gcc problem: when there is no reference to a variable
 161  * in a module it will be moved to the end of the program. This causes
 162  * reordering of initcalls which the kernel does not like.
 163  * Add a dummy reference function to avoid this. The function is
 164  * deleted by the linker.
 165  */
 166 #define LTO_REFERENCE_INITCALL(x) \
 167         ; /* yes this is needed */                      \
 168         static __used __exit void *reference_##x(void)  \
 169         {                                               \
 170                 return &x;                              \
 171         }
 172 #else
 173 #define LTO_REFERENCE_INITCALL(x)
 174 #endif
 175
 176 /* initcalls are now grouped by functionality into separate
 177  * subsections. Ordering inside the subsections is determined
 178  * by link order.
 179  * For backwards compatibility, initcall() puts the call in
 180  * the device init subsection.
 181  *
 182  * The `id' arg to __define_initcall() is needed so that multiple initcalls
 183  * can point at the same handler without causing duplicate-symbol build errors.
 184  */
 185
 186 #define __define_initcall(fn, id) \
 187         static initcall_t __initcall_##fn##id __used \
 188         __attribute__((__section__(".initcall" #id ".init"))) = fn; \
 189         LTO_REFERENCE_INITCALL(__initcall_##fn##id)
 190
 191 /*
 192  * Early initcalls run before initializing SMP.
 193  *
 194  * Only for built-in code, not modules.
 195  */
 196 #define early_initcall(fn)              __define_initcall(fn, early)
 197
 198 /*
 199  * A "pure" initcall has no dependencies on anything else, and purely
 200  * initializes variables that couldn't be statically initialized.
 201  *
 202  * This only exists for built-in code, not for modules.
 203  * Keep main.c:initcall_level_names[] in sync.
 204  */
 205 #define pure_initcall(fn)               __define_initcall(fn, 0)
 206
 207 #define core_initcall(fn)               __define_initcall(fn, 1)
 208 #define core_initcall_sync(fn)          __define_initcall(fn, 1s)
 209 #define postcore_initcall(fn)           __define_initcall(fn, 2)
 210 #define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
 211 #define arch_initcall(fn)               __define_initcall(fn, 3)
 212 #define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
 213 #define subsys_initcall(fn)             __define_initcall(fn, 4)
 214 #define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
 215 #define fs_initcall(fn)                 __define_initcall(fn, 5)
 216 #define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
 217 #define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
 218 #define device_initcall(fn)             __define_initcall(fn, 6)
 219 #define device_initcall_sync(fn)        __define_initcall(fn, 6s)
 220 #define late_initcall(fn)               __define_initcall(fn, 7)
 221 #define late_initcall_sync(fn)          __define_initcall(fn, 7s)
 222
 223 #define __initcall(fn) device_initcall(fn)
 224
 225 #define __exitcall(fn) \
 226         static exitcall_t __exitcall_##fn __exit_call = fn
 227
 228 #define console_initcall(fn) \
 229         static initcall_t __initcall_##fn \
 230         __used __section(.con_initcall.init) = fn
 231
 232 #define security_initcall(fn) \
 233         static initcall_t __initcall_##fn \
 234         __used __section(.security_initcall.init) = fn
 235
 236 struct obs_kernel_param {
 237         const char *str;
 238         int (*setup_func)(char *);
 239         int early;
 240 };
 241
 242 /*
 243  * Only for really core code.  See moduleparam.h for the normal way.
 244  *
 245  * Force the alignment so the compiler doesn't space elements of the
 246  * obs_kernel_param "array" too far apart in .init.setup.
 247  */
 248 #define __setup_param(str, unique_id, fn, early)                        \
 249         static const char __setup_str_##unique_id[] __initconst         \
 250                 __aligned(1) = str;                                     \
 251         static struct obs_kernel_param __setup_##unique_id              \
 252                 __used __section(.init.setup)                           \
 253                 __attribute__((aligned((sizeof(long)))))                \
 254                 = { __setup_str_##unique_id, fn, early }
 255
 256 #define __setup(str, fn)                                                \
 257         __setup_param(str, fn, fn, 0)
 258
 259 /*
 260  * NOTE: fn is as per module_param, not __setup!
 261  * Emits warning if fn returns non-zero.
 262  */
 263 #define early_param(str, fn)                                            \
 264         __setup_param(str, fn, fn, 1)
 265
 266 #define early_param_on_off(str_on, str_off, var, config)                \
 267                                                                         \
 268         int var = IS_ENABLED(config);                                   \
 269                                                                         \
 270         static int __init parse_##var##_on(char *arg)                   \
 271         {                                                               \
 272                 var = 1;                                                \
 273                 return 0;                                               \
 274         }                                                               \
 275         __setup_param(str_on, parse_##var##_on, parse_##var##_on, 1);   \
 276                                                                         \
 277         static int __init parse_##var##_off(char *arg)                  \
 278         {                                                               \
 279                 var = 0;                                                \
 280                 return 0;                                               \
 281         }                                                               \
 282         __setup_param(str_off, parse_##var##_off, parse_##var##_off, 1)
 283
 284 /* Relies on boot_command_line being set */
 285 void __init parse_early_param(void);
 286 void __init parse_early_options(char *cmdline);
 287 #endif /* __ASSEMBLY__ */
 288
 289 #else /* MODULE */
 290
 291 #define __setup_param(str, unique_id, fn)       /* nothing */
 292 #define __setup(str, func)                      /* nothing */
 293 #endif
 294
 295 /* Data marked not to be saved by software suspend */
 296 #define __nosavedata __section(.data..nosave)
 297
 298 #ifdef MODULE
 299 #define __exit_p(x) x
 300 #else
 301 #define __exit_p(x) NULL
 302 #endif
 303
 304 #endif /* _LINUX_INIT_H */