On Mon, Feb 22 2016 at 1:55pm -0500, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > On Sun, Feb 21, 2016 at 2:08 PM, Alasdair G Kergon <agk@xxxxxxxxxx> wrote: > > On Sat, Feb 20, 2016 at 10:13:49AM -0800, Kees Cook wrote: > >> This is a resurrection of a patch series from a few years back, first > >> brought to the dm maintainers in 2010. It creates a way to define dm > >> devices on the kernel command line for systems that do not use an > >> initramfs, or otherwise need a dm running before init starts. > >> > >> This has been used by Chrome OS for several years, and now by Brillo > >> (and likely Android soon). > >> > >> The last version was v4: > >> https://patchwork.kernel.org/patch/104860/ > >> https://patchwork.kernel.org/patch/104861/ > > > > Inconsistencies in the terminology here can be sorted out during review, > > and I see that you've taken on board some of my review comments from > > 2010, but what are your responses to the rest of them? > > Ah, sorry, the threads I could find were incomplete, so I wasn't able > to find those comments that were made to Will's 2010 submission. In > some of the cleanups I did I was very confused about "target" vs > "table", and tried to fix that. Regardless, I'm open to fixing > whatever is needed. :) > > Thanks for looking at this again! This work isn't going to fly as is. I appreciate the effort and the goal (without understanding _why_) but: you're open-coding, duplicating and/or reinventing way too much in do_mounts_dm.c 1) You first need to answer: _why_ is using a proper initramfs not viable? A very simple initramfs that issues dmsetup commands, etc, isn't so daunting is it? Why is it so important for the kernel to natively provide a dmsetup interface? Chrome, Android, etc cannot use initramfs? 2) If you are able to adequately justify the need for dm=: I'd much rather the dm= kernel commandline be a simple series of comma-delimited dmsetup-like commands. You'd handle each command with extremely basic parsing: <dm_ioctl_cmd> <args> [, <dm_ioctl_cmd> <args>] (inventing a special token to denote <newline>, to support tables with multiple entries, rather than relying on commas and counts, etc) and you'd then have do_mounts_dm.c open /dev/mapper/control directly and issue proper DM ioctls rather than adding all your shim code. This last bit of opening /dev/mapper/control from init needs more research -- not sure if doing such a thing from kernel is viable/safe/acceptable. Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
