On Tue, Apr 10, 2018 at 11:09:33PM +0200, Daniel Kiper wrote: > On Fri, Apr 06, 2018 at 03:08:23PM +0200, Kristian Amlie wrote: > > On 06/04/18 14:35, Daniel Kiper wrote: > > > On Fri, Apr 06, 2018 at 11:25:22AM +0200, Kristian Amlie wrote: > > >> Hey, I work for Northern.tech, developing update software for embedded > > >> Linux devices. > > >> > > >> I have a question about GRUB's environment block: This block is not > > > > > > I am not sure what exactly you mean by "GRUB's environment block". > > > Could you send me some references to the code? > > > > Of course, sorry if the context wasn't clear. I'm talking about the > > environment block mentioned here: > > https://www.gnu.org/software/grub/manual/grub/grub.html#Environment-block, > > which is used to store information from one boot to the next, using > > save_env and load_env. > > > > >> checksummed, and hence I reckon it can become corrupt if power is lost > > >> in the middle of a write. > > > > > > What about the other blocks? > > > > In theory, there is only one block, because it is written in-place, > > directly on disk, without changing any other filesystem blocks. Is that > > what you meant by "other blocks"? > > > > >> This is an important safety criterion for us, so we've been thinking of > > >> developing environment block checksumming as an extension to the > > >> existing save_env and load_env commands. The most likely approach will > > >> be to grab X amount of bytes at the end of the block and use these for > > >> the checksum. > > > > > > Could you tell us more about that? > > > > The idea comes from U-Boot [1], which uses a dedicated block on a > > storage device to store data, and uses a CRC32 checksum to make sure it > > is consistent. The motivation is to be able to detect that the block is > > corrupt, rather than accepting a block of data that may have incorrect > > data in if a write was interrupted midway by a powerloss. You can read > > more about it in the link. > > > > [2] https://www.denx.de/wiki/DULG/UBootEnvVariables > > I am OK with the idea. However, I think that the feature should have > a kind of switch to turn it off/on. At first sight it looks that new > environment variable is sufficient for it.
And/Or an argument for save_env/load_env... Daniel _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
