kernel 及 ramdisk 移植

 

合成boot.img:
INTERNAL_BOOTIMAGE_ARGS: --kernel out/target/product/xxx/kernel --ramdisk out/target/product/xxx/ramdisk.img --base 0x80000000 --pagesize 2048 --cmdline console=ttyHSL0,115200,n8 androidboot.console=ttyHSL0 androidboot.hardware=qcom msm_rtb.filter=0x237 ehci-hcd.park=3 androidboot.bootdevice=7824900.sdhci lpm_levels.sleep_disabled=1 earlyprintk buildvariant=userdebug

 

http://blog.csdn.net/liuqingsongmsdn2014/article/details/53694794

 

 

 

内核的逻辑地址：0x90100000

modem\common\build\partition_xxx.xml

kernel\Makefile

all: vmlinux
vmlinux: scripts/link-vmlinux.sh $(vmlinux-deps) FORCE
vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_INIT) $(KBUILD_VMLINUX_MAIN)

export KBUILD_VMLINUX_INIT := $(head-y) $(init-y)
export KBUILD_VMLINUX_MAIN := $(core-y) $(libs-y) $(drivers-y) $(net-y)
export KBUILD_LDS          := arch/$(SRCARCH)/kernel/vmlinux.lds

合成boot.img:
INTERNAL_BOOTIMAGE_ARGS: --kernel out/target/product/xxx/kernel --ramdisk out/target/product/xxx/ramdisk.img --base 0x80000000 --pagesize 2048 --cmdline console=ttyHSL0,115200,n8 androidboot.console=ttyHSL0 androidboot.hardware=qcom msm_rtb.filter=0x237 ehci-hcd.park=3 androidboot.bootdevice=7824900.sdhci lpm_levels.sleep_disabled=1 earlyprintk buildvariant=userdebug

kernel\arch\arm\Makefile
head-y		:= arch/arm/kernel/head$(MMUEXT).o



out\target\product\xxx\obj\KERNEL_OBJ\arch\arm\kernel\vmlinux.lds
.head.text
kernel\arch\arm\kernel\head.S

kernel\include\linux\init.h
#define __HEAD		.section	".head.text","ax"

bootloader传过来的值：（0，0，（PA）tags_phys）
entry(0, machtype, (unsigned*)tags_phys);


head.S
/* r0 = 0,r1 = machine nr, r2 = atags or dtb pointer */
    __HEAD
ENTRY(stext)
#include "head-common.S"

kernel\arch\arm\kernel\head-common.S
b    start_kernel  //启动内核kernel


xxx:/ # mount
rootfs on / type rootfs (ro,seclabel,relatime)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,size=957928k,nr_inodes=149237,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)
proc on /proc type proc (rw,relatime,gid=3009,hidepid=2)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,seclabel,relatime)

kernel\init\main.c
start_kernel
    setup_arch(&command_line);
    setup_command_line(command_line);
    
    mm_init //向内核注册rootfs  //根文件系统初始化
    
    rest_init
        kernel_init
            kernel_init_freeable
              do_basic_setup  //释放Initramfs到rootfs；如果Initramfs中有init，这种情况比较特殊、rootfs就是最后系统使用的根文件系统。
                sys_open((const char __user *) "/dev/console"  //开启控制台
                ramdisk_execute_command = "/init";  //加载ramdisk的init
                load_default_modules  /* rootfs is available now, try loading default modules */
            run_init_process(ramdisk_execute_command) //execute_command  启动init进程
                do_execve
            

ramdisk.img
根文件系统  out\target\product\xxx\root目录
解压 

system\core\init\Android.mk
LOCAL_SRC_FILES:= \
    bootchart.cpp \
    builtins.cpp \
    devices.cpp \
    init.cpp \
    keychords.cpp \
    property_service.cpp \
    signal_handler.cpp \
    ueventd.cpp \
    ueventd_parser.cpp \
    watchdogd.cpp \

LOCAL_MODULE:= init


.rc file
/system/etc/init/
/vendor/etc/init/
/odm/etc/init/


Actions take the form of://执行时机
on  [&& ]*
   
   
   

Services take the form of://执行程序
service   [  ]*
   
   
   ...

Options：They affect how and when init runs the service.
critical
disabled
setenv  
socket    [  [  [  ] ] ]
user 
group  [  ]*
seclabel 
oneshot
class 
onrestart
writepid 

Triggers：Triggers are strings which can be used to match certain kinds of events and used to cause an action to occur.
1、event triggers  ：the form of a simple string 'boot' or 'late-init'
2、property triggers：the form of 'property:=' and 'property:=*'


Commands：
bootchart_init
chmod  
chown   
class_start 
class_stop 
class_reset 
copy  
domainname 
enable 
exec [  [  [  ]* ] ] --  [  ]*
export  
hostname 
ifup 
insmod 
load_all_props
load_persist_props
loglevel 
mkdir  [mode] [owner] [group]
mount_all  [  ]* [--]
mount    [  ]* []
powerctl
restart 
restorecon  [  ]*
restorecon_recursive  [  ]*
rm 
rmdir 
setprop  
setrlimit   
start 
stop 
swapon_all 
symlink  
sysclktz 
trigger 
umount 
verity_load_state
verity_update_state 
wait  [  ]
write   

system\core\init\init.cpp
main
    is_first_stage 
        //mount("tmpfs", "/dev", "tmpfs", MS_NOSUID, "mode=0755");
        //mount("devpts", "/dev/pts", "devpts", 0, NULL);
        //mount("proc", "/proc", "proc", 0, "hidepid=2,gid=" MAKE_STR(AID_READPROC));
        //mount("sysfs", "/sys", "sysfs", 0, NULL);
    //device kmsg and null
    
    parser.AddSectionParser("service",std::make_unique());
        section_parsers_service = ServiceParser
  parser.AddSectionParser("on", std::make_unique());
      section_parsers_on = ActionParser
  parser.AddSectionParser("import", std::make_unique());
      section_parsers_import = ImportParser
    
    parser.ParseConfig("/init.rc");//解析配置文件
        read_file
        ParseData
            section_parser->ParseSection
                ServiceManager::GetInstance().AddService
                ActionManager::GetInstance().AddAction
            section_parser->ParseLineSection
            
    am.QueueEventTrigger
    am.ExecuteOneCommand()
    ....

1.根文件系统初始化

对rootfs有了基本的了解后，需要进一步知道rootfs运行起来的流程。从内核init进程出发开始探索：

asmlinkage void __init start_kernel(void)
    vfs_caches_init_early();
        dcache_init_early();
        inode_init_early();
    --> vfs_caches_init(num_physpages);
        dcache_init();
        inode_init();
        files_init(mempages);
        --> mnt_init();
            --> init_rootfs();
            --> init_mount_tree();
            
            
2.虚拟根文件系统与真实根文件系统

简单的说，一个文件系统对应着一块存储区域，虚拟根文件系统对应的存储区域为内存ram，而直根文件系统对应的存储区域为 硬盘或flash，
根据前面介绍，在系统初始化期间，先挂载的是虚拟根文件系统。那么这里有两个疑问，为什么不直接挂载真实根文件系统？真实根文件系统又是什么时机挂载上去的？

http://blog.csdn.net/liuqingsongmsdn2014/article/details/53694794