Layout dual-flag (Boot Flag) - mtd3
boot_flag indicates which slot to load.
boot_count counts the number of times one slot is started.
| Slot | Flag | kernel | rootfs | Counter |
|---|---|---|---|---|
| 1 | Sercomm0 | uImage1 (Kernel 1) | rootfs1 (File System 1) | boot_count1 |
| 2 | Sercomm1 | uImage2 (Kernel 2) | rootfs2 (File System 2) | boot_count2 |
When the U-boot of the specified slot is loaded, its counter is incremented (example FF-> 01). When the stock firmware boots successfully, it will write to the FF counter. If the boot_count = 03 when loading the slot, then the flag will be toggled. if boot_count1 = 03 and boot_count2 = 03 then the device will switch to Emergency mode (start sc_dl).
View flag:
# hexdump -Cn 8 /dev/mtd3
00000000 53 65 72 63 6f 6d 6d 31 |Sercomm1|
00000008
Set flag:
- Sercomm0 -
# printf 0 | dd bs=1 seek=7 count=1 of=/dev/mtdblock3 - Sercomm1 -
# printf 1 | dd bs=1 seek=7 count=1 of=/dev/mtdblock3
FW OEM v2.0.xx
~ # bootflag_utility --help
bootflag_utility: invalid option -- -
Usage: ./bootflag_utility [-g] [-s value] [-S]
-g get bootflag
-s set bootflag 0 or 1
-S switch bootflag
View flag:
# bootflag_utility -g
[bootflag_utility.c:get_bootflag:52] bootflag=Sercomm0
get_bootflag=0
Set flag:
- Sercomm0 -
# bootflag_utility -s 0 - Sercomm1 -
# bootflag_utility -s 1
View counter
$((0x20001))=131073
- boot_count1 -
# hexdump -s 131073 -Cn 1 /dev/mtd3 - boot_count2 -
# hexdump -s 131074 -Cn 1 /dev/mtd3
# hexdump -s 131073 -Cn 2 /dev/mtd3
00020001 ff ff |..|
00020003
Reset counter
- boot_count1 -
# printf '\xFF' | dd bs=1 count=1 seek=131073 of=/dev/mtdblock3 - boot_count2 -
# printf '\xFF' | dd bs=1 count=1 seek=131074 of=/dev/mtdblock3
Algorithm from MTK SDK
Reference
APSoC SDK 4.3.0.0 User’s Manual - 209 Page.