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---
edit_link: ''
title: Consoles
origin_url: >-
https://raw.githubusercontent.com/automotive-grade-linux/docs-sources/master/docs/security-blueprint/part-2/3-Consoles.md
---
<!-- WARNING: This file is generated by fetch_docs.js using /home/boron/Documents/AGL/docs-webtemplate/site/_data/tocs/architecture/master/security_blueprint-security-blueprint-book.yml -->
# Consoles
## Disable serial console
Serial console output shall be disabled. To disable console output in U-Boot,
set the following macros:
<!-- section-config -->
Domain | `Config` name | `Value`
---------------------- | --------------------------------------- | ---------
Boot-Consoles-Serial-1 | `CONFIG_SILENT_CONSOLE` | `Disable`
Boot-Consoles-Serial-2 | `CONFIG_SYS_DEVICE_NULLDEV` | `Disable`
Boot-Consoles-Serial-3 | `CONFIG_SILENT_CONSOLE_UPDATE_ON_RELOC` | `Disable`
<!-- end-section-config --> <!-- section-todo -->
Domain | Improvement
--------------- | ------------------------------------
Boot-Consoles-1 | Secure loader: No reference earlier?
<!-- end-section-todo -->
And set "**silent**" environment variable. For the Secure loader,
disable the traces by not defining the below macro:
<!-- section-config -->
Domain | `Environment variable` name | _State_
---------------------- | --------------------------- | -------------
Boot-Consoles-Serial-1 | `INC_DEBUG_PRINT` | _Not defined_
<!-- end-section-config -->
For sboot proper configuration needs to be done to disable the serial console.
--------------------------------------------------------------------------------
<!-- pagebreak -->
## Immutable environment variables
In U-Boot, ensure Kernel command line, boot commands, boot delay and other
environment variables are immutable. This will prevent side-loading of alternate
images, by restricting the boot selection to only the image in FLASH.
The environment variables shall be part of the text region in U-Boot as default
environment variable and not in non-volatile memory.
Remove configuration options related to non-volatile memory, such as:
<!-- section-config -->
Domain | `Config` name | _State_
-------------------------- | ---------------------------- | ---------
Boot-Consoles-Variables-1 | `CONFIG_ENV_IS_IN_MMC` | `#undef`
Boot-Consoles-Variables-2 | `CONFIG_ENV_IS_IN_EEPROM` | `#undef`
Boot-Consoles-Variables-3 | `CONFIG_ENV_IS_IN_FLASH` | `#undef`
Boot-Consoles-Variables-4 | `CONFIG_ENV_IS_IN_DATAFLASH` | `#undef`
Boot-Consoles-Variables-5 | `CONFIG_ENV_IS_IN_FAT` | `#undef`
Boot-Consoles-Variables-6 | `CONFIG_ENV_IS_IN_NAND` | `#undef`
Boot-Consoles-Variables-7 | `CONFIG_ENV_IS_IN_NVRAM` | `#undef`
Boot-Consoles-Variables-8 | `CONFIG_ENV_IS_IN_ONENAND` | `#undef`
Boot-Consoles-Variables-9 | `CONFIG_ENV_IS_IN_SPI_FLASH` | `#undef`
Boot-Consoles-Variables-10 | `CONFIG_ENV_IS_IN_REMOTE` | `#undef`
Boot-Consoles-Variables-11 | `CONFIG_ENV_IS_IN_UBI` | `#undef`
Boot-Consoles-Variables-12 | `CONFIG_ENV_IS_NOWHERE` | `#define`
<!-- end-section-config -->
--------------------------------------------------------------------------------
<!-- pagebreak -->
## (Recommendation) Removal of memory dump commands
In U-Boot, following commands shall be disabled to avoid memory dumps:
```
md : Memory Display command.
mm : Memory modify command - auto incrementing address.
nm : Memory modify command - constant address.
mw : Memory write.
cp : Memory copy.
mwc : Memory write cyclic.
mdc : Memory display cyclic.
mtest : Simple ram read/write test.
loopw : Infinite write loop on address range.
```
<!-- section-config -->
Domain | `Command` name | _State_
----------------------- | -------------- | ----------
Boot-Consoles-MemDump-1 | `md` | _Disabled_
Boot-Consoles-MemDump-2 | `mm` | _Disabled_
Boot-Consoles-MemDump-3 | `nm` | _Disabled_
Boot-Consoles-MemDump-4 | `mw` | _Disabled_
Boot-Consoles-MemDump-5 | `cp` | _Disabled_
Boot-Consoles-MemDump-6 | `mwc` | _Disabled_
Boot-Consoles-MemDump-7 | `mdc` | _Disabled_
Boot-Consoles-MemDump-8 | `mtest` | _Disabled_
Boot-Consoles-MemDump-9 | `loopw` | _Disabled_
<!-- end-section-config -->
Similarly, memory dump support shall be disabled from sboot.
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