On Sat, Jan 19, 2019 at 11:36:06AM +0100, Greg KH wrote: > On Sat, Jan 19, 2019 at 02:28:00AM -0800, Christoph Hellwig wrote: > > This seems like a pretty horrible idea and waste of kernel memory. > > It's only a waste if you want it to be a waste, i.e. if you load the > kernel module. > > This really isn't any different from how /proc/config.gz works. Yes, that's right, it can be built as a module and loaded and unloaded on demand to free the kernel memory. Also such a module can be made a part of the initrd image itself (like other kernel modules that are built into an initrd), so this solution is already initrd-ready if anyone really wants it that way. > > Just add support to kbuild to store a compressed archive in initramfs > > and unpack it in the right place. > > I think the issue is that some devices do not use initramfs, or switch > away from it after init happens or something like that. Joel has all of > the looney details that he can provide. Initially I had written this as an image embedded into an init section, similar to the initramfs. On boot if a boot argument was passed, then the archive embedded was allocated additional non-init kernel memory to store it for retrieval through /proc. After that, the image that's embedded would be dropped entirely as its init memory. If no boot argument was passed, then no additional memory is used at all. Even though I got that working, I decided not to go with it because it was clunky because: 1. It required modification of the linker scripts in the kernel to embed the image into the init section, and also required a boot argument to be passed which makes the decision on whether to have headers as a boot-time decision than a post-boot decision. For these reasons, it is much cleaner to just have a loadable module and make it on-demand, as I am doing in this patch similar to what /proc/config.gz does. thanks! - Joel
