linux/include/linux/init.h
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   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 */
 116typedef int (*initcall_t)(void);
 117typedef void (*exitcall_t)(void);
 118
 119#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
 120typedef int initcall_entry_t;
 121
 122static inline initcall_t initcall_from_entry(initcall_entry_t *entry)
 123{
 124        return offset_to_ptr(entry);
 125}
 126#else
 127typedef initcall_t initcall_entry_t;
 128
 129static inline initcall_t initcall_from_entry(initcall_entry_t *entry)
 130{
 131        return *entry;
 132}
 133#endif
 134
 135extern initcall_entry_t __con_initcall_start[], __con_initcall_end[];
 136
 137/* Used for contructor calls. */
 138typedef void (*ctor_fn_t)(void);
 139
 140struct file_system_type;
 141
 142/* Defined in init/main.c */
 143extern int do_one_initcall(initcall_t fn);
 144extern char __initdata boot_command_line[];
 145extern char *saved_command_line;
 146extern unsigned int reset_devices;
 147
 148/* used by init/main.c */
 149void setup_arch(char **);
 150void prepare_namespace(void);
 151void __init init_rootfs(void);
 152extern struct file_system_type rootfs_fs_type;
 153
 154#if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX)
 155extern bool rodata_enabled;
 156#endif
 157#ifdef CONFIG_STRICT_KERNEL_RWX
 158void mark_rodata_ro(void);
 159#endif
 160
 161extern void (*late_time_init)(void);
 162
 163extern bool initcall_debug;
 164
 165#endif
 166  
 167#ifndef MODULE
 168
 169#ifndef __ASSEMBLY__
 170
 171/*
 172 * initcalls are now grouped by functionality into separate
 173 * subsections. Ordering inside the subsections is determined
 174 * by link order. 
 175 * For backwards compatibility, initcall() puts the call in 
 176 * the device init subsection.
 177 *
 178 * The `id' arg to __define_initcall() is needed so that multiple initcalls
 179 * can point at the same handler without causing duplicate-symbol build errors.
 180 *
 181 * Initcalls are run by placing pointers in initcall sections that the
 182 * kernel iterates at runtime. The linker can do dead code / data elimination
 183 * and remove that completely, so the initcall sections have to be marked
 184 * as KEEP() in the linker script.
 185 */
 186
 187#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
 188#define ___define_initcall(fn, id, __sec)                       \
 189        __ADDRESSABLE(fn)                                       \
 190        asm(".section   \"" #__sec ".init\", \"a\"      \n"     \
 191        "__initcall_" #fn #id ":                        \n"     \
 192            ".long      " #fn " - .                     \n"     \
 193            ".previous                                  \n");
 194#else
 195#define ___define_initcall(fn, id, __sec) \
 196        static initcall_t __initcall_##fn##id __used \
 197                __attribute__((__section__(#__sec ".init"))) = fn;
 198#endif
 199
 200#define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
 201
 202/*
 203 * Early initcalls run before initializing SMP.
 204 *
 205 * Only for built-in code, not modules.
 206 */
 207#define early_initcall(fn)              __define_initcall(fn, early)
 208
 209/*
 210 * A "pure" initcall has no dependencies on anything else, and purely
 211 * initializes variables that couldn't be statically initialized.
 212 *
 213 * This only exists for built-in code, not for modules.
 214 * Keep main.c:initcall_level_names[] in sync.
 215 */
 216#define pure_initcall(fn)               __define_initcall(fn, 0)
 217
 218#define core_initcall(fn)               __define_initcall(fn, 1)
 219#define core_initcall_sync(fn)          __define_initcall(fn, 1s)
 220#define postcore_initcall(fn)           __define_initcall(fn, 2)
 221#define postcore_initcall_sync(fn)      __define_initcall(fn, 2s)
 222#define arch_initcall(fn)               __define_initcall(fn, 3)
 223#define arch_initcall_sync(fn)          __define_initcall(fn, 3s)
 224#define subsys_initcall(fn)             __define_initcall(fn, 4)
 225#define subsys_initcall_sync(fn)        __define_initcall(fn, 4s)
 226#define fs_initcall(fn)                 __define_initcall(fn, 5)
 227#define fs_initcall_sync(fn)            __define_initcall(fn, 5s)
 228#define rootfs_initcall(fn)             __define_initcall(fn, rootfs)
 229#define device_initcall(fn)             __define_initcall(fn, 6)
 230#define device_initcall_sync(fn)        __define_initcall(fn, 6s)
 231#define late_initcall(fn)               __define_initcall(fn, 7)
 232#define late_initcall_sync(fn)          __define_initcall(fn, 7s)
 233
 234#define __initcall(fn) device_initcall(fn)
 235
 236#define __exitcall(fn)                                          \
 237        static exitcall_t __exitcall_##fn __exit_call = fn
 238
 239#define console_initcall(fn)    ___define_initcall(fn,, .con_initcall)
 240
 241struct obs_kernel_param {
 242        const char *str;
 243        int (*setup_func)(char *);
 244        int early;
 245};
 246
 247/*
 248 * Only for really core code.  See moduleparam.h for the normal way.
 249 *
 250 * Force the alignment so the compiler doesn't space elements of the
 251 * obs_kernel_param "array" too far apart in .init.setup.
 252 */
 253#define __setup_param(str, unique_id, fn, early)                        \
 254        static const char __setup_str_##unique_id[] __initconst         \
 255                __aligned(1) = str;                                     \
 256        static struct obs_kernel_param __setup_##unique_id              \
 257                __used __section(".init.setup")                         \
 258                __attribute__((aligned((sizeof(long)))))                \
 259                = { __setup_str_##unique_id, fn, early }
 260
 261#define __setup(str, fn)                                                \
 262        __setup_param(str, fn, fn, 0)
 263
 264/*
 265 * NOTE: fn is as per module_param, not __setup!
 266 * Emits warning if fn returns non-zero.
 267 */
 268#define early_param(str, fn)                                            \
 269        __setup_param(str, fn, fn, 1)
 270
 271#define early_param_on_off(str_on, str_off, var, config)                \
 272                                                                        \
 273        int var = IS_ENABLED(config);                                   \
 274                                                                        \
 275        static int __init parse_##var##_on(char *arg)                   \
 276        {                                                               \
 277                var = 1;                                                \
 278                return 0;                                               \
 279        }                                                               \
 280        __setup_param(str_on, parse_##var##_on, parse_##var##_on, 1);   \
 281                                                                        \
 282        static int __init parse_##var##_off(char *arg)                  \
 283        {                                                               \
 284                var = 0;                                                \
 285                return 0;                                               \
 286        }                                                               \
 287        __setup_param(str_off, parse_##var##_off, parse_##var##_off, 1)
 288
 289/* Relies on boot_command_line being set */
 290void __init parse_early_param(void);
 291void __init parse_early_options(char *cmdline);
 292#endif /* __ASSEMBLY__ */
 293
 294#else /* MODULE */
 295
 296#define __setup_param(str, unique_id, fn)       /* nothing */
 297#define __setup(str, func)                      /* nothing */
 298#endif
 299
 300/* Data marked not to be saved by software suspend */
 301#define __nosavedata __section(".data..nosave")
 302
 303#ifdef MODULE
 304#define __exit_p(x) x
 305#else
 306#define __exit_p(x) NULL
 307#endif
 308
 309#endif /* _LINUX_INIT_H */
 310