| .. SPDX-License-Identifier: GPL-2.0+ |
| |
| Boot Count Limit |
| ================ |
| |
| This allows to detect multiple failed attempts to boot Linux. |
| |
| After a power-on reset, "bootcount" variable will be initialized with 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", thus allowing for more boot |
| cycles. |
| |
| BOOTCOUNT_EXT |
| ------------- |
| |
| This adds support for maintaining boot count in a file on an EXT filesystem. |
| The file to use is define by: |
| |
| SYS_BOOTCOUNT_EXT_INTERFACE |
| SYS_BOOTCOUNT_EXT_DEVPART |
| 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 save. |
| So the Userspace Application must set the "upgrade_available" and "bootcount" |
| variables to 0, if a boot was successfully. |
| This also prevents writes on all reboots. |