Xx_initcall initialization label in LINUX kernel __linux

xx_initcall initialization label in Linux kernel

Tian Hai li @csdn 2011-07-02

There are a number of initialization indicators in the Linux kernel Postcore_initcall (), Arch_initcall (), Subsys_initcall (), Device_initcall (), etc. What's the effect? Review the source code (Android goldfish-2.6.29) and search for relevant articles on the Web. Initialization Label

First look at the definitions of these macros (defined in file include/linux/init.h)[CPP] View Plain copy #define  pure_initcall (FN)                 __define_initcall ("0", fn,0)    #define  core_initcall (FN)                 __define_initcall ("1", fn,1)    #define  CORE_INITCALL_SYNC (FN)           __ Define_initcall ("1s", fn,1s)    #define  postcore_initcall (FN)             __define_initcall ("2", fn,2)    #define  POSTCORE_INITCALL_SYNC (FN)       __define_initcall ("2s", fn,2s)    #define  arch_initcall (FN)                __define_initcall ("3 ", fn,3)    #define  ARCH_INITCALL_SYNC (FN)            __define_initcAll ("3s", fn,3s)    #define  subsys_initcall (FN)               __define_initcall ("4", fn,4)    #define  SUBSYS_INITCALL_SYNC (FN)         __define_initcall ("4s", fn,4s)    #define  fs_ Initcall (FN)                   __define_initcall ("5", fn,5)    #define  FS_INITCALL_SYNC (FN)              __define_initcall ("5s", fn,5s)    #define  rootfs_ Initcall (FN)              __define_initcall (" Rootfs ", Fn,rootfs)    #define  device_initcall (FN)               __define_initcall ("6", fn,6)    #define  DEVICE_INITCALL_SYNC (FN)      &Nbsp;  __define_initcall ("6s", fn,6s)    #define  late_initcall (FN)                 __define_initcall ("7", fn,7)     #define  LATE_INITCALL_SYNC (FN)           __define_ Initcall ("7s", fn,7s)   

__define_initcall

These macros all use __define_initcall (), and then look at its definition (also defined in file include/linux/init.h) [CPP] view plain copy #define __define_ Initcall (level,fn,id) \ static initcall_t __initcall_# #fn # #id __used \ __attribute__ (__section__ (". In Itcall "level". Init ")) = fn

Here initcall_t is the function pointer, the prototype is as follows, [CPP] view plain copy typedef int (*initcall_t) (void);

The attribute __attribute__ ((__section__ ()) means that the object is placed in a section of the name in parentheses.

So the meaning of __define_initcall is:

1) Declare a name called __initcall_# #fn的函数指针;

2 Initialize the function pointer to FN;

3 The function pointer variable needs to be placed in a section named ". Initcall" Level ". Init".

3. Place. Initcall.init Section

By clarifying the meaning of __define_initcall, we know that these initialization label-decorated function pointers are placed in their section.

Section '. Initcall ' level '. Init ' was put into initcalls (include/asm-generic/vmlinux.lds.h)[CPP] View Plain copy #define  INITCALLS                                                      \               * (. Initcallearly.init)                                     \               vmlinux_symbol (__ Early_initcall_end)  = .;                \                * (. Initcall0.init)                                        \                * (. Initcall0s.init)                                        \                * (. Initcall1.init)                                          \               * (. Initcall1s.init)                                       \               * (. Initcall2.init)                                         \                * (. Initcall2s.init)                                        \                * (. Initcall3.init)                                         \                * (. Initcall3s.init)                                        \                * (. Initcall4.init)                                         \                * (. Initcall4s.init)                                        \                * (. Initcall5.init)                                         \                * (. Initcall5s.init)                                        \                * (. Initcallrootfs.init)                                    \                * (. Initcall6.init)                                         \                * (. Initcall6s.init)                                        \                * (. Initcall7.init)                                         \                * (. Initcall7s.init)   

The sections defined in __initcall_start and __initcall_end and Initcalls are placed in the. Init segment in ARCH/XXX/KERNEL/VMLINUX.LDS.S.                           [plain] view plain copy SECTIONS {. init: {__initcall_start =.;           Initcalls __initcall_end =.; }   }

4. Initialize the function in Initcallxx.init.

The functions in these section are executed sequentially during initialization (init kernel thread->do_basic_setup () [Main.c#778]->do_initcalls ()).

The program (INIT/MAIN.C file Do_initcalls () function) is as follows, Do_initcalls () performs the functions in the. Initcallxx.init sequentially. [CPP] view plain copy for (call = __early_initcall_end, call < __initcall_end call++) DO_ONE_INITCA ll (*call);

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