讓你的 Android init 可以掛載 UBIFS 檔案系統
在 Android 的 init.rc 中,可以看到掛載檔案系統使用的 mount 命令,而 這命令和我們一般在 Linux 下使用的 mount 命令不同,是個提供給 init 運作的描 述句,你可以在 system/core/init/builtins.c 找到他的實現。
在大多數的 Android 設備中,常常可以看到掛載 yaffs2 的描述,卻很少看到 ubifs 的掛載描述
mount yaffs2 mtd@system /system
為什麼理應效能比較好的 ubifs 卻未被 Android 系統廣泛使用?個人推測有以下原 因
- 1. Android 採用 yaffs2 作為 MTD NAND Flash 檔案系統
- 2. 大多數的 Android 設備 (ex:手機) 都內建有 emmc 作為儲存空間
實際上在我下載到的 AOSP 原始碼中,init 也看不到有支援 ubifs 的影子,那 我們想讓 Android 的 init 掛載 ubifs 要怎麼辦? 這時候只好自己動手了~
讓 init 可以掛載 ubifs 所進行的修改
Android 的 init 原始碼位於 system/core/init 裡面,為了增加 ubifs 的功 能,我們將針對以下檔案進行修改
- 1. init/builtins.c
- 2. init/util.h
- 3. init/util.c
- 4. init/ubi-user.h
修改 init/builtins.c
我們所希望的是可以在 init.rc 增加下面這樣的描述,讓 init 可以掛載 ubifs
mount ubifs ubi@system /system
要辦到這項功能,我們必須在 system/core/init/builtins.c 裡面加入一 些程式,讓 init 遇到了 ubi@ 這樣的語句時,會去使用 ubiattach 來去掛載 mtd 設備。
diff --git a/init/builtins.c b/init/builtins.c
index b0a97ae..d8066a2 100644
--- a/init/builtins.c
+++ b/init/builtins.c
@@ -325,6 +325,22 @@ int do_mount(int nargs, char **args)
}
goto exit_success;
+ } else if (!strncmp(source, "ubi@", 4)) {
+ n = ubi_attach_mtd(source + 4);
+ if (n < 0) {
+ return -1;
+ }
+
+ sprintf(tmp, "/dev/ubi%d_0", n);
+
+ if (wait)
+ wait_for_file(tmp, COMMAND_RETRY_TIMEOUT);
+ if (mount(tmp, target, system, flags, options) < 0) {
+ ubi_detach_dev(n);
+ return -1;
+ }
+
+ goto exit_success;
} else if (!strncmp(source, "loop@", 5)) {
int mode, loop, fd;
struct loop_info info;
修改 init/util.h
我們在 system/core/init/builtins.c 使用到一些和 ubifs 相關的函式,這 些函式並未被宣告以及定義,因此我們宣告在 util.h 裡面。
diff --git a/init/util.h b/init/util.h
index 45905b6..09aa574 100644
--- a/init/util.h
+++ b/init/util.h
@@ -41,4 +41,7 @@ void get_hardware_name(char *hardware, unsigned int *revision);
void import_kernel_cmdline(int in_qemu, void (*import_kernel_nv)(char *name, int in_qemu));
int make_dir(const char *path, mode_t mode);
int restorecon(const char *pathname);
+
+int ubi_attach_mtd(const char *name);
+int ubi_detach_dev(int dev);
#endif
增加 init/ubi-user.h 檔案
由於我們進行一些 ubifs 相關函式的定義時,需要用到 ubifs 的結構,因此 需要增加相關結構的資訊。 ubi-user.h 這個檔案取自於 Linux Kernel 的 include/mtd/ubi-user.h
請將 Linux Kernel 的 include/mtd/ubi-user.h 複製到 init 目錄裡面,注意到最好 選用你用於 Android 平台的 Linux Kernel 裡面的檔案,因為這個檔案的一些 structure 宣 告可能會因為 Linux Kernel 版本不同而改變。
以下為本文使用的範例:
/*
* Copyright © International Business Machines Corp., 2006
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
* the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Author: Artem Bityutskiy (Битюцкий Артём)
*/
#ifndef __UBI_USER_H__
#define __UBI_USER_H__
#include <linux/types.h>
/*
* UBI device creation (the same as MTD device attachment)
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* MTD devices may be attached using %UBI_IOCATT ioctl command of the UBI
* control device. The caller has to properly fill and pass
* &struct ubi_attach_req object - UBI will attach the MTD device specified in
* the request and return the newly created UBI device number as the ioctl
* return value.
*
* UBI device deletion (the same as MTD device detachment)
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* An UBI device maybe deleted with %UBI_IOCDET ioctl command of the UBI
* control device.
*
* UBI volume creation
* ~~~~~~~~~~~~~~~~~~~
*
* UBI volumes are created via the %UBI_IOCMKVOL ioctl command of UBI character
* device. A &struct ubi_mkvol_req object has to be properly filled and a
* pointer to it has to be passed to the ioctl.
*
* UBI volume deletion
* ~~~~~~~~~~~~~~~~~~~
*
* To delete a volume, the %UBI_IOCRMVOL ioctl command of the UBI character
* device should be used. A pointer to the 32-bit volume ID hast to be passed
* to the ioctl.
*
* UBI volume re-size
* ~~~~~~~~~~~~~~~~~~
*
* To re-size a volume, the %UBI_IOCRSVOL ioctl command of the UBI character
* device should be used. A &struct ubi_rsvol_req object has to be properly
* filled and a pointer to it has to be passed to the ioctl.
*
* UBI volumes re-name
* ~~~~~~~~~~~~~~~~~~~
*
* To re-name several volumes atomically at one go, the %UBI_IOCRNVOL command
* of the UBI character device should be used. A &struct ubi_rnvol_req object
* has to be properly filled and a pointer to it has to be passed to the ioctl.
*
* UBI volume update
* ~~~~~~~~~~~~~~~~~
*
* Volume update should be done via the %UBI_IOCVOLUP ioctl command of the
* corresponding UBI volume character device. A pointer to a 64-bit update
* size should be passed to the ioctl. After this, UBI expects user to write
* this number of bytes to the volume character device. The update is finished
* when the claimed number of bytes is passed. So, the volume update sequence
* is something like:
*
* fd = open("/dev/my_volume");
* ioctl(fd, UBI_IOCVOLUP, &image_size);
* write(fd, buf, image_size);
* close(fd);
*
* Logical eraseblock erase
* ~~~~~~~~~~~~~~~~~~~~~~~~
*
* To erase a logical eraseblock, the %UBI_IOCEBER ioctl command of the
* corresponding UBI volume character device should be used. This command
* unmaps the requested logical eraseblock, makes sure the corresponding
* physical eraseblock is successfully erased, and returns.
*
* Atomic logical eraseblock change
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Atomic logical eraseblock change operation is called using the %UBI_IOCEBCH
* ioctl command of the corresponding UBI volume character device. A pointer to
* a &struct ubi_leb_change_req object has to be passed to the ioctl. Then the
* user is expected to write the requested amount of bytes (similarly to what
* should be done in case of the "volume update" ioctl).
*
* Logical eraseblock map
* ~~~~~~~~~~~~~~~~~~~~~
*
* To map a logical eraseblock to a physical eraseblock, the %UBI_IOCEBMAP
* ioctl command should be used. A pointer to a &struct ubi_map_req object is
* expected to be passed. The ioctl maps the requested logical eraseblock to
* a physical eraseblock and returns. Only non-mapped logical eraseblocks can
* be mapped. If the logical eraseblock specified in the request is already
* mapped to a physical eraseblock, the ioctl fails and returns error.
*
* Logical eraseblock unmap
* ~~~~~~~~~~~~~~~~~~~~~~~~
*
* To unmap a logical eraseblock to a physical eraseblock, the %UBI_IOCEBUNMAP
* ioctl command should be used. The ioctl unmaps the logical eraseblocks,
* schedules corresponding physical eraseblock for erasure, and returns. Unlike
* the "LEB erase" command, it does not wait for the physical eraseblock being
* erased. Note, the side effect of this is that if an unclean reboot happens
* after the unmap ioctl returns, you may find the LEB mapped again to the same
* physical eraseblock after the UBI is run again.
*
* Check if logical eraseblock is mapped
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* To check if a logical eraseblock is mapped to a physical eraseblock, the
* %UBI_IOCEBISMAP ioctl command should be used. It returns %0 if the LEB is
* not mapped, and %1 if it is mapped.
*
* Set an UBI volume property
* ~~~~~~~~~~~~~~~~~~~~~~~~~
*
* To set an UBI volume property the %UBI_IOCSETPROP ioctl command should be
* used. A pointer to a &struct ubi_set_vol_prop_req object is expected to be
* passed. The object describes which property should be set, and to which value
* it should be set.
*/
/*
* When a new UBI volume or UBI device is created, users may either specify the
* volume/device number they want to create or to let UBI automatically assign
* the number using these constants.
*/
#define UBI_VOL_NUM_AUTO (-1)
#define UBI_DEV_NUM_AUTO (-1)
/* Maximum volume name length */
#define UBI_MAX_VOLUME_NAME 127
/* ioctl commands of UBI character devices */
#define UBI_IOC_MAGIC 'o'
/* Create an UBI volume */
#define UBI_IOCMKVOL _IOW(UBI_IOC_MAGIC, 0, struct ubi_mkvol_req)
/* Remove an UBI volume */
#define UBI_IOCRMVOL _IOW(UBI_IOC_MAGIC, 1, __s32)
/* Re-size an UBI volume */
#define UBI_IOCRSVOL _IOW(UBI_IOC_MAGIC, 2, struct ubi_rsvol_req)
/* Re-name volumes */
#define UBI_IOCRNVOL _IOW(UBI_IOC_MAGIC, 3, struct ubi_rnvol_req)
/* ioctl commands of the UBI control character device */
#define UBI_CTRL_IOC_MAGIC 'o'
/* Attach an MTD device */
#define UBI_IOCATT _IOW(UBI_CTRL_IOC_MAGIC, 64, struct ubi_attach_req)
/* Detach an MTD device */
#define UBI_IOCDET _IOW(UBI_CTRL_IOC_MAGIC, 65, __s32)
/* ioctl commands of UBI volume character devices */
#define UBI_VOL_IOC_MAGIC 'O'
/* Start UBI volume update */
#define UBI_IOCVOLUP _IOW(UBI_VOL_IOC_MAGIC, 0, __s64)
/* LEB erasure command, used for debugging, disabled by default */
#define UBI_IOCEBER _IOW(UBI_VOL_IOC_MAGIC, 1, __s32)
/* Atomic LEB change command */
#define UBI_IOCEBCH _IOW(UBI_VOL_IOC_MAGIC, 2, __s32)
/* Map LEB command */
#define UBI_IOCEBMAP _IOW(UBI_VOL_IOC_MAGIC, 3, struct ubi_map_req)
/* Unmap LEB command */
#define UBI_IOCEBUNMAP _IOW(UBI_VOL_IOC_MAGIC, 4, __s32)
/* Check if LEB is mapped command */
#define UBI_IOCEBISMAP _IOR(UBI_VOL_IOC_MAGIC, 5, __s32)
/* Set an UBI volume property */
#define UBI_IOCSETVOLPROP _IOW(UBI_VOL_IOC_MAGIC, 6, \
struct ubi_set_vol_prop_req)
/* Maximum MTD device name length supported by UBI */
#define MAX_UBI_MTD_NAME_LEN 127
/* Maximum amount of UBI volumes that can be re-named at one go */
#define UBI_MAX_RNVOL 32
/*
* UBI data type hint constants.
*
* UBI_LONGTERM: long-term data
* UBI_SHORTTERM: short-term data
* UBI_UNKNOWN: data persistence is unknown
*
* These constants are used when data is written to UBI volumes in order to
* help the UBI wear-leveling unit to find more appropriate physical
* eraseblocks.
*/
enum {
UBI_LONGTERM = 1,
UBI_SHORTTERM = 2,
UBI_UNKNOWN = 3,
};
/*
* UBI volume type constants.
*
* @UBI_DYNAMIC_VOLUME: dynamic volume
* @UBI_STATIC_VOLUME: static volume
*/
enum {
UBI_DYNAMIC_VOLUME = 3,
UBI_STATIC_VOLUME = 4,
};
/*
* UBI set volume property ioctl constants.
*
* @UBI_VOL_PROP_DIRECT_WRITE: allow (any non-zero value) or disallow (value 0)
* user to directly write and erase individual
* eraseblocks on dynamic volumes
*/
enum {
UBI_VOL_PROP_DIRECT_WRITE = 1,
};
/**
* struct ubi_attach_req - attach MTD device request.
* @ubi_num: UBI device number to create
* @mtd_num: MTD device number to attach
* @vid_hdr_offset: VID header offset (use defaults if %0)
* @padding: reserved for future, not used, has to be zeroed
*
* This data structure is used to specify MTD device UBI has to attach and the
* parameters it has to use. The number which should be assigned to the new UBI
* device is passed in @ubi_num. UBI may automatically assign the number if
* @UBI_DEV_NUM_AUTO is passed. In this case, the device number is returned in
* @ubi_num.
*
* Most applications should pass %0 in @vid_hdr_offset to make UBI use default
* offset of the VID header within physical eraseblocks. The default offset is
* the next min. I/O unit after the EC header. For example, it will be offset
* 512 in case of a 512 bytes page NAND flash with no sub-page support. Or
* it will be 512 in case of a 2KiB page NAND flash with 4 512-byte sub-pages.
*
* But in rare cases, if this optimizes things, the VID header may be placed to
* a different offset. For example, the boot-loader might do things faster if
* the VID header sits at the end of the first 2KiB NAND page with 4 sub-pages.
* As the boot-loader would not normally need to read EC headers (unless it
* needs UBI in RW mode), it might be faster to calculate ECC. This is weird
* example, but it real-life example. So, in this example, @vid_hdr_offer would
* be 2KiB-64 bytes = 1984. Note, that this position is not even 512-bytes
* aligned, which is OK, as UBI is clever enough to realize this is 4th
* sub-page of the first page and add needed padding.
*/
struct ubi_attach_req {
__s32 ubi_num;
__s32 mtd_num;
__s32 vid_hdr_offset;
__s8 padding[12];
};
/**
* struct ubi_mkvol_req - volume description data structure used in
* volume creation requests.
* @vol_id: volume number
* @alignment: volume alignment
* @bytes: volume size in bytes
* @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
* @padding1: reserved for future, not used, has to be zeroed
* @name_len: volume name length
* @padding2: reserved for future, not used, has to be zeroed
* @name: volume name
*
* This structure is used by user-space programs when creating new volumes. The
* @used_bytes field is only necessary when creating static volumes.
*
* The @alignment field specifies the required alignment of the volume logical
* eraseblock. This means, that the size of logical eraseblocks will be aligned
* to this number, i.e.,
* (UBI device logical eraseblock size) mod (@alignment) = 0.
*
* To put it differently, the logical eraseblock of this volume may be slightly
* shortened in order to make it properly aligned. The alignment has to be
* multiple of the flash minimal input/output unit, or %1 to utilize the entire
* available space of logical eraseblocks.
*
* The @alignment field may be useful, for example, when one wants to maintain
* a block device on top of an UBI volume. In this case, it is desirable to fit
* an integer number of blocks in logical eraseblocks of this UBI volume. With
* alignment it is possible to update this volume using plane UBI volume image
* BLOBs, without caring about how to properly align them.
*/
struct ubi_mkvol_req {
__s32 vol_id;
__s32 alignment;
__s64 bytes;
__s8 vol_type;
__s8 padding1;
__s16 name_len;
__s8 padding2[4];
char name[UBI_MAX_VOLUME_NAME + 1];
} __packed;
/**
* struct ubi_rsvol_req - a data structure used in volume re-size requests.
* @vol_id: ID of the volume to re-size
* @bytes: new size of the volume in bytes
*
* Re-sizing is possible for both dynamic and static volumes. But while dynamic
* volumes may be re-sized arbitrarily, static volumes cannot be made to be
* smaller than the number of bytes they bear. To arbitrarily shrink a static
* volume, it must be wiped out first (by means of volume update operation with
* zero number of bytes).
*/
struct ubi_rsvol_req {
__s64 bytes;
__s32 vol_id;
} __packed;
/**
* struct ubi_rnvol_req - volumes re-name request.
* @count: count of volumes to re-name
* @padding1: reserved for future, not used, has to be zeroed
* @vol_id: ID of the volume to re-name
* @name_len: name length
* @padding2: reserved for future, not used, has to be zeroed
* @name: new volume name
*
* UBI allows to re-name up to %32 volumes at one go. The count of volumes to
* re-name is specified in the @count field. The ID of the volumes to re-name
* and the new names are specified in the @vol_id and @name fields.
*
* The UBI volume re-name operation is atomic, which means that should power cut
* happen, the volumes will have either old name or new name. So the possible
* use-cases of this command is atomic upgrade. Indeed, to upgrade, say, volumes
* A and B one may create temporary volumes %A1 and %B1 with the new contents,
* then atomically re-name A1->A and B1->B, in which case old %A and %B will
* be removed.
*
* If it is not desirable to remove old A and B, the re-name request has to
* contain 4 entries: A1->A, A->A1, B1->B, B->B1, in which case old A1 and B1
* become A and B, and old A and B will become A1 and B1.
*
* It is also OK to request: A1->A, A1->X, B1->B, B->Y, in which case old A1
* and B1 become A and B, and old A and B become X and Y.
*
* In other words, in case of re-naming into an existing volume name, the
* existing volume is removed, unless it is re-named as well at the same
* re-name request.
*/
struct ubi_rnvol_req {
__s32 count;
__s8 padding1[12];
struct {
__s32 vol_id;
__s16 name_len;
__s8 padding2[2];
char name[UBI_MAX_VOLUME_NAME + 1];
} ents[UBI_MAX_RNVOL];
} __packed;
/**
* struct ubi_leb_change_req - a data structure used in atomic LEB change
* requests.
* @lnum: logical eraseblock number to change
* @bytes: how many bytes will be written to the logical eraseblock
* @dtype: data type (%UBI_LONGTERM, %UBI_SHORTTERM, %UBI_UNKNOWN)
* @padding: reserved for future, not used, has to be zeroed
*/
struct ubi_leb_change_req {
__s32 lnum;
__s32 bytes;
__s8 dtype;
__s8 padding[7];
} __packed;
/**
* struct ubi_map_req - a data structure used in map LEB requests.
* @lnum: logical eraseblock number to unmap
* @dtype: data type (%UBI_LONGTERM, %UBI_SHORTTERM, %UBI_UNKNOWN)
* @padding: reserved for future, not used, has to be zeroed
*/
struct ubi_map_req {
__s32 lnum;
__s8 dtype;
__s8 padding[3];
} __packed;
/**
* struct ubi_set_vol_prop_req - a data structure used to set an UBI volume
* property.
* @property: property to set (%UBI_VOL_PROP_DIRECT_WRITE)
* @padding: reserved for future, not used, has to be zeroed
* @value: value to set
*/
struct ubi_set_vol_prop_req {
__u8 property;
__u8 padding[7];
__u64 value;
} __packed;
#endif /* __UBI_USER_H__ */
修改 init/util.c
由於我們增加了一些 ubifs 相關的函式,因此必須自己在 init/util.c 裡面加入相對應的實現。
diff --git a/init/util.c b/init/util.c
index 743748b..aa9ca87 100755
--- a/init/util.c
+++ b/init/util.c
@@ -31,6 +31,8 @@
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
+#include <sys/ioctl.h>
+
/* for ANDROID_SOCKET_* */
#include <cutils/sockets.h>
@@ -40,3 +42,4 @@
#include "init.h"
#include "log.h"
#include "util.h"
+#include "ubi-user.h"
/*
* android_name_to_id - returns the integer uid/gid associated with the given
@@ -512,3 +515,99 @@ int restorecon(const char *pathname)
#endif
return 0;
}
+
+#define UBI_CTRL_DEV "/dev/ubi_ctrl"
+#define UBI_SYS_PATH "/sys/class/ubi"
+
+static int ubi_dev_read_int(int dev, const char *file, int def)
+{
+ int fd, val = def;
+ char path[128], buf[64];
+
+ sprintf(path, UBI_SYS_PATH "/ubi%d/%s", dev, file);
+ wait_for_file(path, 5);
+ fd = open(path, O_RDONLY);
+ if (fd == -1) {
+ return val;
+ }
+
+ if (read(fd, buf, 64) > 0) {
+ val = atoi(buf);
+ }
+
+ close(fd);
+ return val;
+}
+
+int ubi_attach_mtd(const char *name)
+{
+ int ret;
+ int mtd_num, ubi_num;
+ int ubi_ctrl, ubi_dev;
+ int vols, avail_lebs, leb_size;
+ char path[128];
+ struct ubi_attach_req attach_req;
+ struct ubi_mkvol_req mkvol_req;
+
+ mtd_num = mtd_name_to_number(name);
+ if (mtd_num == -1) {
+ return -1;
+ }
+
+ ubi_ctrl = open(UBI_CTRL_DEV, O_RDONLY);
+ if (ubi_ctrl == -1) {
+ return -1;
+ }
+
+ memset(&attach_req, 0, sizeof(struct ubi_attach_req));
+ attach_req.ubi_num = UBI_DEV_NUM_AUTO;
+ attach_req.mtd_num = mtd_num;
+
+ ret = ioctl(ubi_ctrl, UBI_IOCATT, &attach_req);
+ if (ret == -1) {
+ close(ubi_ctrl);
+ return -1;
+ }
+
+ ubi_num = attach_req.ubi_num;
+
+ vols = ubi_dev_read_int(ubi_num, "volumes_count", -1);
+ if (vols == 0) {
+ sprintf(path, "/dev/ubi%d", ubi_num);
+ ubi_dev = open(path, O_RDONLY);
+ if (ubi_dev == -1) {
+ close(ubi_ctrl);
+ return ubi_num;
+ }
+
+ avail_lebs = ubi_dev_read_int(ubi_num, "avail_eraseblocks", 0);
+ leb_size = ubi_dev_read_int(ubi_num, "eraseblock_size", 0);
+
+ memset(&mkvol_req, 0, sizeof(struct ubi_mkvol_req));
+ mkvol_req.vol_id = UBI_VOL_NUM_AUTO;
+ mkvol_req.alignment = 1;
+ mkvol_req.bytes = (long long)avail_lebs * leb_size;
+ mkvol_req.vol_type = UBI_DYNAMIC_VOLUME;
+ ret = snprintf(mkvol_req.name, UBI_MAX_VOLUME_NAME + 1, "%s", name);
+ mkvol_req.name_len = ret;
+ ioctl(ubi_dev, UBI_IOCMKVOL, &mkvol_req);
+ close(ubi_dev);
+ }
+
+ close(ubi_ctrl);
+ return ubi_num;
+}
+
+int ubi_detach_dev(int dev)
+{
+ int ret, ubi_ctrl;
+
+ ubi_ctrl = open(UBI_CTRL_DEV, O_RDONLY);
+ if (ubi_ctrl == -1) {
+ return -1;
+ }
+
+ ret = ioctl(ubi_ctrl, UBI_IOCDET, &dev);
+ close(ubi_ctrl);
+ return ret;
+}
ramdisk 修改
將上面的修正加入並重新編譯 Android 後,你就可以在 ramdisk 下使用以下方式去掛載你 的 ubifs 檔案系統,修改 init.*.rc 並添加以下資訊:
mount ubifs ubi@system /system
參考連結
[2] android 和 ubifs