Commit cff75e0b authored May 08, 2017 by Daniel Thompson Committed by Linus Torvalds May 08, 2017

initramfs: provide a way to ignore image provided by bootloader

Many "embedded" architectures provide CMDLINE_FORCE to allow the kernel
to override the command line provided by an inflexible bootloader.
However there is currrently no way for the kernel to override the
initramfs image provided by the bootloader meaning there are still ways
for bootloaders to make things difficult for us.

Fix this by introducing INITRAMFS_FORCE which can prevent the kernel
from loading the bootloader supplied image.

We use CMDLINE_FORCE (and its friend CMDLINE_EXTEND) to imply that the
system has an inflexible bootloader.  This allow us to avoid presenting
this config option to users of systems where inflexible bootloaders
aren't usually a problem.

Link: http://lkml.kernel.org/r/20170217121940.30126-1-daniel.thompson@linaro.org


Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent da5e108b

init/initramfs.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -613,7 +613,7 @@ static int __init populate_rootfs(void)
		if (err)
		panic("%s", err); /* Failed to decompress INTERNAL initramfs */
		/* If available load the bootloader supplied initrd */
		if (initrd_start) {
		if (initrd_start && !IS_ENABLED(CONFIG_INITRAMFS_FORCE)) {
		#ifdef CONFIG_BLK_DEV_RAM
		int fd;
		printk(KERN_INFO "Trying to unpack rootfs image as initramfs...\n");

usr/Kconfig

+10 −0

Original line number	Diff line number	Diff line
		@@ -21,6 +21,16 @@ config INITRAMFS_SOURCE

		If you are not sure, leave it blank.

		config INITRAMFS_FORCE
		bool "Ignore the initramfs passed by the bootloader"
		depends on CMDLINE_EXTEND \|\| CMDLINE_FORCE
		help
		This option causes the kernel to ignore the initramfs image
		(or initrd image) passed to it by the bootloader. This is
		analogous to CMDLINE_FORCE, which is found on some architectures,
		and is useful if you cannot or don't want to change the image
		your bootloader passes to the kernel.

		config INITRAMFS_ROOT_UID
		int "User ID to map to 0 (user root)"
		depends on INITRAMFS_SOURCE!=""

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