[linux-lvm] [PATCH v12] dm: add support to directly boot to a mapped device
keescook at chromium.org
Thu Feb 21 22:42:47 UTC 2019
On Thu, Feb 21, 2019 at 12:33 PM Helen Koike <helen.koike at collabora.com> wrote:
> Add a "create" module parameter, which allows device-mapper targets to be
> configured at boot time. This enables early use of dm targets in the boot
> process (as the root device or otherwise) without the need of an initramfs.
> The syntax used in the boot param is based on the concise format from the
> dmsetup tool to follow the rule of least surprise:
> sudo dmsetup table --concise /dev/mapper/lroot
> Which is:
> <name> ::= The device name.
> <uuid> ::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | ""
> <minor> ::= The device minor number | ""
> <flags> ::= "ro" | "rw"
> <table> ::= <start_sector> <num_sectors> <target_type> <target_args>
> <target_type> ::= "verity" | "linear" | ...
> For example, the following could be added in the boot parameters:
> dm-mod.create="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0
> Only the targets that were tested are allowed and the ones that doesn't
> change any block device when the dm is create as read-only. For example,
> mirror and cache targets are not allowed. The rationale behind this is
> that if the user makes a mistake, choosing the wrong device to be the
> mirror or the cache can corrupt data.
> The only targets allowed are:
> * crypt
> * delay
> * linear
> * snapshot-origin
> * striped
> * verity
> Co-developed-by: Will Drewry <wad at chromium.org>
> Co-developed-by: Kees Cook <keescook at chromium.org>
> Co-developed-by: Enric Balletbo i Serra <enric.balletbo at collabora.com>
> Signed-off-by: Helen Koike <helen.koike at collabora.com>
Thanks! This appears to have everything Chrome OS needs. I've asked a
few other folks to look at it too.
Reviewed-by: Kees Cook <keescook at chromium.org>
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