Android系统分区

Android系统开发时，经常会遇到添加或者调整系统分区大小的问题，下面以mstar的一款产品为例进行分析：

（1）mount指令可以查看到板子中挂在的分区，主要关注ext4类型分区，例如tvservice，tvconfig，tvconfig，tvcustomer

|shell@arbutus:/ # mount
rootfs / rootfs ro,relatime
tmpfs /dev tmpfs rw,nosuid,relatime,mode=
devpts /dev/pts devpts rw,relatime,mode=
proc /proc proc rw,relatime
sysfs /sys sysfs rw,relatime
debugfs /sys/kernel/debug debugfs rw,relatime
none /acct cgroup rw,relatime,cpuacct
none /sys/fs/cgroup tmpfs rw,relatime,mode=,gid=
tmpfs /mnt/asec tmpfs rw,relatime,mode=,gid=
tmpfs /mnt/obb tmpfs rw,relatime,mode=,gid=
none /dev/cpuctl cgroup rw,relatime,cpu
tmpfs /mnt/usb tmpfs rw,relatime,mode=,gid=
tmpfs /mnt/iso tmpfs rw,relatime,mode=,gid=
tmpfs /mnt/samba tmpfs rw,relatime,mode=,gid=
tmpfs /var tmpfs rw,relatime,mode=,gid=
/dev/block/platform/mstar_mci./by-name/system /system ext4 ro,relatime,data=ordered
/dev/block/platform/mstar_mci./by-name/cache /cache ext4 rw,nosuid,nodev,noatime,data=ordered
/dev/block/platform/mstar_mci./by-name/userdata /data ext4 rw,nosuid,nodev,noatime,data=ordered
/dev/block/platform/mstar_mci./by-name/tvservice /tvservice ext4 ro,relatime,data=ordered
/dev/block/platform/mstar_mci./by-name/tvconfig /tvconfig ext4 ro,relatime,data=ordered
/dev/block/platform/mstar_mci./by-name/tvdatabase /tvdatabase ext4 rw,nosuid,nodev,noatime,data=ordered
/dev/block/platform/mstar_mci./by-name/tvcustomer /tvcustomer ext4 rw,nosuid,nodev,noatime,data=ordered
/dev/fuse /mnt/sdcard fuse rw,nosuid,nodev,noexec,relatime,user_id=,group_id=,default_permissions,allow_other  

　　（2）查看分区文件fstab.monet (device/mstar/arbutus/目录下)，截取部分信息如下：

/dev/block/platform/mstar_mci./by-name/system          /system             ext4      ro                                                    wait
/dev/block/platform/mstar_mci./by-name/cache           /cache              ext4      noatime,nosuid,nodev                                  wait,block_validity,nodiscard,data=ordered,journal_checksum
/dev/block/platform/mstar_mci./by-name/userdata        /data               ext4      noatime,nosuid,nodev                                  wait,block_validity,nodiscard,data=ordered,journal_checksum
/dev/block/platform/mstar_mci./by-name/tvservice       /tvservice          ext4      ro                                                    wait
/dev/block/platform/mstar_mci./by-name/tvconfig        /tvconfig           ext4      ro                                                    wait
/dev/block/platform/mstar_mci./by-name/tvdatabase      /tvdatabase         ext4      noatime,nosuid,nodev                                  wait,block_validity,nodiscard,data=ordered,journal_checksum
/dev/block/platform/mstar_mci./by-name/tvcustomer      /tvcustomer         ext4      noatime,nosuid,nodev   

android平台不同厂商可能名称不一样，但是都是fstab.xxx的形式

（3）指定各个分区的大小，BoardConfig.mk (device/mstar/arbutus)文件指定各自大小可以根据需要进行修改

# mmc part
# :  type name      (size)
#.  misc           (512K)
#.  recovery       (19M)
#.  boot           (15M)
#.  tee            (6M)
#.  rtpm           (256K)
#.  dtb            (1M)
#.  system         (800M)
#.  userdata       (900M)
#.  cache          (1G)
#. tvservice      (160M)
#. tvconfig       (10M)
#. tvdatabase     (8M)
#. tvcustomer     (16M)
BOARD_RECOVERYIMAGE_PARTITION_SIZE   := 0x01300000
BOARD_BOOTIMAGE_PARTITION_SIZE       := 0x00F00000
BOARD_TEEIMAGE_PARTITION_SIZE        := 0x00600000
BOARD_RTPMIMAGE_PARTITION_SIZE       := 0x00040000
BOARD_DTBIMAGE_PARTITION_SIZE        := 0x00100000
BOARD_SYSTEMIMAGE_PARTITION_SIZE     := 0x33C00000
BOARD_USERDATAIMAGE_PARTITION_SIZE   := 0x38000000
BOARD_CACHEIMAGE_PARTITION_SIZE      := 0x40000000
BOARD_TVSERVICEIMAGE_PARTITION_SIZE  := 0x0A000000
BOARD_TVCONFIGIMAGE_PARTITION_SIZE   := 0x00A00000
BOARD_TVDATABASEIMAGE_PARTITION_SIZE := 0x00800000
BOARD_TVCUSTOMERIMAGE_PARTITION_SIZE := 0x01000000

BOARD_FLASH_BLOCK_SIZE := 

　　（4）启动脚本加载，init.monet.rc脚本中on fs 模块中启动

on fs
    mkdir /tvservice
    mkdir /tvconfig
    mkdir /tvdatabase
    mkdir /tvcustomer
    mount_all /fstab.monet

　　

（5）init进程解析fstab.monet文件

keywords.h文件中注册mount_all操作方法

enum {
    K_UNKNOWN,
#endif
    KEYWORD(capability,  OPTION,  , )
    KEYWORD(chdir,       COMMAND, , do_chdir)
    KEYWORD(chroot,      COMMAND, , do_chroot)
    KEYWORD(class,       OPTION,  , )
    KEYWORD(class_start, COMMAND, , do_class_start)
    KEYWORD(class_stop,  COMMAND, , do_class_stop)
    KEYWORD(class_reset, COMMAND, , do_class_reset)
    KEYWORD(console,     OPTION,  , )
    KEYWORD(critical,    OPTION,  , )
    KEYWORD(disabled,    OPTION,  , )
    KEYWORD(domainname,  COMMAND, , do_domainname)
    KEYWORD(enable,      COMMAND, , do_enable)
    KEYWORD(exec,        COMMAND, , do_exec)
    KEYWORD(export,      COMMAND, , do_export)
    KEYWORD(group,       OPTION,  , )
    KEYWORD(hostname,    COMMAND, , do_hostname)
    KEYWORD(ifup,        COMMAND, , do_ifup)
    KEYWORD(insmod,      COMMAND, , do_insmod)
    KEYWORD(import,      SECTION, , )
    KEYWORD(keycodes,    OPTION,  , )
    KEYWORD(mkdir,       COMMAND, , do_mkdir)
    KEYWORD(mount_all,   COMMAND, , do_mount_all)
    KEYWORD(mount,       COMMAND, , do_mount)
    KEYWORD(on,          SECTION, , )
    KEYWORD(oneshot,     OPTION,  , )
    KEYWORD(onrestart,   OPTION,  , )
    KEYWORD(powerctl,    COMMAND, , do_powerctl)
    KEYWORD(restart,     COMMAND, , do_restart)
    KEYWORD(restorecon,  COMMAND, , do_restorecon)
    KEYWORD(restorecon_recursive,  COMMAND, , do_restorecon_recursive)
    KEYWORD(rm,          COMMAND, , do_rm)
    KEYWORD(rmdir,       COMMAND, , do_rmdir)
    KEYWORD(seclabel,    OPTION,  , )
    KEYWORD(service,     SECTION, , )
    KEYWORD(setcon,      COMMAND, , do_setcon)
    KEYWORD(setenforce,  COMMAND, , do_setenforce)
    KEYWORD(setenv,      OPTION,  , )
    KEYWORD(setkey,      COMMAND, , do_setkey)
    KEYWORD(setprop,     COMMAND, , do_setprop)
    KEYWORD(setrlimit,   COMMAND, , do_setrlimit)
    KEYWORD(setsebool,   COMMAND, , do_setsebool)
    KEYWORD(socket,      OPTION,  , )
    KEYWORD(start,       COMMAND, , do_start)
    KEYWORD(stop,        COMMAND, , do_stop)
    KEYWORD(swapon_all,  COMMAND, , do_swapon_all)
    KEYWORD(trigger,     COMMAND, , do_trigger)
    KEYWORD(symlink,     COMMAND, , do_symlink)
    KEYWORD(sysclktz,    COMMAND, , do_sysclktz)
    KEYWORD(user,        OPTION,  , )
    KEYWORD(wait,        COMMAND, , do_wait)
    KEYWORD(write,       COMMAND, , do_write)
    KEYWORD(copy,        COMMAND, , do_copy)
    KEYWORD(chown,       COMMAND, , do_chown)
    KEYWORD(chmod,       COMMAND, , do_chmod)
    KEYWORD(loglevel,    COMMAND, , do_loglevel)
    KEYWORD(load_persist_props,    COMMAND, , do_load_persist_props)
    KEYWORD(load_all_props,        COMMAND, , do_load_all_props)
    KEYWORD(ioprio,      OPTION,  , )
#ifdef __MAKE_KEYWORD_ENUM__
    KEYWORD_COUNT,
}

builtins.c文件中do_mount_all，启动一个进程调用fs_mgr_read_fstab，fs_mgr_mount_all启动解析，其中system\core\fs_mgr有被vold，adb等模块用来解析

fstab.xxx等分区文件。

（6）根据第三步中指定的分区大小，进行打包对应分区的img文件

releaseimage.sh, mkimage.sh, build_image.sh, make_usb_upgrade.sh等脚本中，会根据第三步设置的大小来制作img文件

如mkimage.sh

function make-images()
{
    mkdir -p $RELEASE_OUT
    mkdir -p $RELEASE_OUT/scripts

    gernerate-script-start

    # Raw partition must be first.
    make-raw-partition
    make-split-fs-partition system $BOARD_SYSTEMIMAGE_PARTITION_SIZE true
    make-fs-partition userdata $BOARD_USERDATAIMAGE_PARTITION_SIZE true
    make-fs-partition cache $BOARD_CACHEIMAGE_PARTITION_SIZE true
    make-fs-partition tvservice $BOARD_TVSERVICEIMAGE_PARTITION_SIZE false
    make-fs-partition tvconfig $BOARD_TVCONFIGIMAGE_PARTITION_SIZE false
    make-fs-partition tvdatabase $BOARD_TVDATABASEIMAGE_PARTITION_SIZE false
    make-fs-partition tvcustomer $BOARD_TVCUSTOMERIMAGE_PARTITION_SIZE false
    ......
    ......

}

buiild_image.sh文件

#make-fs-partition $PARTITION_NAME $PARTITION_SIZE $PARTITION_LZO
function make-fs-partition()
{
    echo -e "\033[31mMake fs $1 partition...\033[0m"
    local PARTITION_NAME=$
    local PARTITION_SIZE=$
    local PARTITION_LZO=$

    # Generate image
    gernerate-fs-image $PARTITION_NAME $PARTITION_SIZE $PARTITION_LZO

    release-fs-partition $PARTITION_NAME $PARTITION_SIZE $PARTITION_LZO
}

function gernerate-fs-image()
{
    local PARTITION_NAME=$
    local PARTITION_SIZE=$
    local PARTITION_LZO=$

    if [ "$PARTITION_NAME" == "userdata" ]; then
        local MOUNT_POINT=data
    else
        local MOUNT_POINT=$PARTITION_NAME
    fi

    local TARGET_OUT=$PRODUCT_OUT/$MOUNT_POINT
    if [ ! -d "$TARGET_OUT" ]; then
        echo "No $TARGET_OUT directory to gernerate image."
        return
    fi

    if [ "$PARTITION_NAME" == "system" -o "$PARTITION_NAME" == "userdata" -o "$PARTITION_NAME" == "cache" -o "$PARTITION_NAME" == "systembackup" ]; then
        if [  $PARTITION_NAME == "system" ]; then
            local IMAGE_INFO=$PRODUCT_OUT/obj/PACKAGING/systemimage_intermediates/system_image_info.txt
        else
            local IMAGE_INFO=$PRODUCT_OUT/obj/PACKAGING/"$PARTITION_NAME"_intermediates/"$PARTITION_NAME"_image_info.txt
        fi

        generate-userimage-prop-dictionary $IMAGE_INFO
        ./build/tools/releasetools/build_image.py $TARGET_OUT $IMAGE_INFO $PRODUCT_OUT/$PARTITION_NAME.img
    else
        <span style="background-color: rgb(0, 102, 0);">make_ext4fs -S $PRODUCT_OUT/root/file_contexts -l $PARTITION_SIZE -a $MOUNT_POINT $PRODUCT_OUT/$PARTITION_NAME.img $TARGET_OUT</span>
    fi
}