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--- doc:appunti:hardware:android_partitions [2020/01/17 10:24] – [sgdisk] niccolo
+++ doc:appunti:hardware:android_partitions [2020/01/17 12:41] (current) – removed niccolo
@@ Line 1: / Line 1: @@
-====== Android Partitions on MTK Devices ======
-===== NAND Flash vs eMMC Flash =====
-**NAND flash** can only be read in pages, some bits in a page may be wrong and need to be corrected by an error correction mechanism.
-With NAND flash the OS and device drivers are responsible to handle these issues.
-**eMMC Flash** combines NAND memory with a built-in controller, that handles most of the things you have to take care of when dealing with NAND flash.
-===== The Scatter File =====
-===== EMMC Regions =====
-**Embedded Multi-Media Controller** (eMMC) refers to a package consisting of both flash memory and a flash memory controller integrated into a single on-board chip. Device supports several hardware partitions, it is on-board and thus non removable.
-  * **BOOT** - one or more small partitions intended for boot firmware; eMMC 4.3 spec requires 2 boot partitions.
-  * **RPMB** - Replay Protected Memory Block - intended to store secure data (ie DRM content protection keys); eMMC 4.4 spec adds the requirement of an RPMB partition.
-  * **USER** - a large partition intended for general storage; eMMC 4.3 spec requires 1 user partition.
-Into a **scatter file** you can see references to **region** labeled **EMMC_BOOT_1** and **EMMC_USER**, because partition images can live in that different //partitions// or //regions//. NOTICE: the USER partition or region is normally partitioned in turn into other partitions, so - when referring to eMMC partition - it is advisable to use the //region// term, to avoid confusion.
-===== Inspecting partitions on the command line =====
-The following commands were executed on a **ZTE Blade A610**, running **Android 6.0**, via the **adb shell** command line. The phone was rooted so that the **su** command was available.
-==== cat /proc/partitions ====
-<code>
-cat /proc/partitions
-major minor  #blocks  name
-        0      12910 loop0
-        0     986264 zram0
-        0   15388672 mmcblk0
-        1       3072 mmcblk0p1
-        2       5120 mmcblk0p2
-        3      10240 mmcblk0p3
-        4      10240 mmcblk0p4
-        5        512 mmcblk0p5
-        6        512 mmcblk0p6
-        7      16384 mmcblk0p7
-        8      16384 mmcblk0p8
-        9       8192 mmcblk0p9
-       10      10240 mmcblk0p10
-       11        512 mmcblk0p11
-       12       2048 mmcblk0p12
-       13       6144 mmcblk0p13
-       14       8192 mmcblk0p14
-       15       5120 mmcblk0p15
-       16       5120 mmcblk0p16
-       17       1024 mmcblk0p17
-       18      32768 mmcblk0p18
-       19      37888 mmcblk0p19
-       20    3022848 mmcblk0p20
-       21     409600 mmcblk0p21
-       22   11759104 mmcblk0p22
-       23      16384 mmcblk0p23
-       96       4096 mmcblk0rpmb
-       64       4096 mmcblk0boot1
-       32       4096 mmcblk0boot0
-        0   11759104 dm-0
-</code>
-The **mmcblk0** partition is actually the eMMC **USER** region, sized 15388672 blocks (15028 Mb). It is in turn partitioned in 23 partitions. The **boot0**, **boot1** and **rpmb** partitions have a size of 4096 blocks each, i.e. **4194304 (0x400000) bytes**.
-==== sgdisk ====
-The **/system/bin/sgdisk** command is accessible only with root privileges.
-<code>
-sgdisk --print /dev/block/mmcblk0
-Disk /dev/block/mmcblk0: 30777344 sectors, 14.7 GiB
-Logical sector size: 512 bytes
-Disk identifier (GUID): 00000000-0000-0000-0000-000000000000
-Partition table holds up to 23 entries
-First usable sector is 1024, last usable sector is 30776319
-Partitions will be aligned on 1024-sector boundaries
-Total free space is 0 sectors (0 bytes)
-Number  Start (sector)    End (sector)  Size       Code  Name
-            1024            7167   3.0 MiB     0700  proinfo
-            7168           17407   5.0 MiB     0700  nvram
-           17408           37887   10.0 MiB    0700  protect1
-           37888           58367   10.0 MiB    0700  protect2
-           58368           59391   512.0 KiB   0700  lk
-           59392           60415   512.0 KiB   0700  para
-           60416           93183   16.0 MiB    0700  boot
-           93184          125951   16.0 MiB    0700  recovery
-          125952          142335   8.0 MiB     0700  logo
-          142336          162815   10.0 MiB    0700  expdb
-          162816          163839   512.0 KiB   0700  seccfg
-          163840          167935   2.0 MiB     0700  oemkeystore
-          167936          180223   6.0 MiB     0700  secro
-          180224          196607   8.0 MiB     0700  keystore
-          196608          206847   5.0 MiB     0700  tee1
-          206848          217087   5.0 MiB     0700  tee2
-          217088          219135   1024.0 KiB  0700  frp
-          219136          284671   32.0 MiB    0700  nvdata
-          284672          360447   37.0 MiB    0700  metadata
-          360448         6406143   2.9 GiB     0700  system
-         6406144         7225343   400.0 MiB   0700  cache
-         7225344        30743551   11.2 GiB    0700  userdata
-        30743552        30776319   16.0 MiB    0700  flashinfo
-</code>
-Doing the math, you can see that the 23 partitions existing in **mmcblk0** leave some space: One is at the begin, sized 1024 sectors or **524288 (0x80000) bytes**. The other unpartitioned space is at the end, the size can be calculated by the difference of size shown by ''cat /proc/partitions'', it is again **524288 (0x80000) bytes**. Theese two spaces are referred into the scatter file as **pgpt** and **sgpt** respectively (primary and secondary GPT parition tables?).
-==== /dev/block/mmcblk0boot0 ====
-The partition **/dev/block/mmcblk0boot0** is the one referred as region **EMMC_BOOT_1** in the scatter file, and it is dedicated to the **preloader**.
-The actual Linux device content starts with the characters **EMMC_BOOT**. It seems that it is an header of **2048 (0x800) bytes** and the actual preloader follows that header. FIXME Some stock ROMs include the preloader image, without that header. But if you readback the preloader partition using **SP Flash Tool**, you get an image with that heder included.
-===== Web References =====
-  * **[[http://www.lieberbiber.de/2015/07/02/mediatek-details-soc-startup/|MediaTek details: SoC startup]]**
-  * **[[http://www.lieberbiber.de/2015/07/04/mediatek-details-partitions-and-preloader/|MediaTek details: Partitions and Preloader]]**
-  * **[[http://trac.gateworks.com/wiki/MMC|MultiMediaCard (MMC)]]**