3rd-party/linux-kernel-module-cheat
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build: -c to enable a single linux kernel config

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Disable CONFIG_FORTIFY_SOURCE=y by default as it might incur overhead,
enable CONFIG_FRAMEBUFFER_CONSOLE_ROTATION=y as it should not.
This commit is contained in:
Ciro Santilli
2018-05-05 11:50:22 +01:00
parent 149ab9302b
commit c735790099
4 changed files with 39 additions and 19 deletions
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28
README.adoc
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@@ -2134,6 +2134,14 @@ If you want to just use your own exact `.config` instead, do:
Beware that Buildroot can `sed` override some of the configurations we make no matter what, e.g. it forces `CONFIG_BLK_DEV_INITRD=y` when `BR2_TARGET_ROOTFS_CPIO` is on, so you might want to double check as explained at <<find-the-kernel-config>>. TODO check if there is a way to prevent that patching and maybe patch Buildroot for it, it is too fuzzy. People should be able to just build with whatever `.config` they want.
==== Modify a config option
Only effective for the current build:
....
./build -c 'CONFIG_FORTIFY_SOURCE=y' -l
....
==== Find the kernel config
Ge the build config in guest:
@@ -2887,15 +2895,15 @@ Stop the cursor from blinking:
echo 0 > /sys/class/graphics/fbcon/cursor_blink
....
Rotate the console 90 degrees!
Rotate the console 90 degrees! https://askubuntu.com/questions/237963/how-do-i-rotate-my-display-when-not-using-an-x-server
....
echo 1 > /sys/class/graphics/fbcon/rotate
....
Requires `CONFIG_FRAMEBUFFER_CONSOLE_ROTATION=y`.
Relies on: `CONFIG_FRAMEBUFFER_CONSOLE_ROTATION=y`.
Documented under: `fb/`.
Documented under: `Documentation/fb/`.
TODO: font and keymap. Mentioned at: https://cmcenroe.me/2017/05/05/linux-console.html and I think can be done with Busybox `loadkmap` and `loadfont`, we just have to understand their formats, related:
@@ -2995,17 +3003,25 @@ Looks like a recompile is needed to modify the image...
* https://superuser.com/questions/736423/changing-kernel-bootsplash-image
* https://unix.stackexchange.com/questions/153975/how-to-change-boot-logo-in-linux-mint
=== Hardening
=== LInux kernel hardening
Make it harder to get hacked and easier to notice that you were, at the cost of some (small?) runtime overhead.
==== CONFIG_FORTIFY_SOURCE
Enable:
....
insmod /strlen_overflow.ko
./build -c 'CONFIG_FORTIFY_SOURCE=y'
....
detects the overflow:
Test it out:
....
./run -F 'insmod /strlen_overflow.ko'
....
Detects the overflow:
....
<4>[ 3.136382] strlen_overflow: loading out-of-tree module taints kernel.