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- .. SPDX-License-Identifier: GPL-2.0+
- Boot Count Limit
- ================
- This is enabled by CONFIG_BOOTCOUNT_LIMIT.
- This allows to detect multiple failed attempts to boot Linux.
- After a power-on reset, the "bootcount" variable will be initialized to 1, and
- each reboot will increment the value by 1.
- If, after a reboot, the new value of "bootcount" exceeds the value of
- "bootlimit", then instead of the standard boot action (executing the contents of
- "bootcmd"), an alternate boot action will be performed, and the contents of
- "altbootcmd" will be executed.
- If the variable "bootlimit" is not defined in the environment, the Boot Count
- Limit feature is disabled. If it is enabled, but "altbootcmd" is not defined,
- then U-Boot will drop into interactive mode and remain there.
- It is the responsibility of some application code (typically a Linux
- application) to reset the variable "bootcount" to 0 when the system booted
- successfully, thus allowing for more boot cycles.
- CONFIG_BOOTCOUNT_EXT
- --------------------
- This adds support for maintaining boot count in a file on an EXT filesystem.
- The file to use is defined by:
- CONFIG_SYS_BOOTCOUNT_EXT_INTERFACE
- CONFIG_SYS_BOOTCOUNT_EXT_DEVPART
- CONFIG_SYS_BOOTCOUNT_EXT_NAME
- The format of the file is:
- ==== =================
- type entry
- ==== =================
- u8 magic
- u8 version
- u8 bootcount
- u8 upgrade_available
- ==== =================
- To prevent unattended usage of "altbootcmd", the "upgrade_available" variable is
- used.
- If "upgrade_available" is 0, "bootcount" is not saved.
- If "upgrade_available" is 1, "bootcount" is saved.
- So a userspace application should take care of setting the "upgrade_available"
- and "bootcount" variables to 0, if the system boots successfully.
- This also avoids writing the "bootcount" information on all reboots.
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