On Sun, May 01, 2022 at 04:46:50PM +0800, Huacai Chen wrote: > Hi, Russell, > > On Sun, May 1, 2022 at 2:35 PM Russell King (Oracle) > <linux@xxxxxxxxxxxxxxx> wrote: > > > > On Sun, May 01, 2022 at 01:22:25PM +0800, Huacai Chen wrote: > > > Hi, Arnd, > > > > > > On Sat, Apr 30, 2022 at 7:02 PM Arnd Bergmann <arnd@xxxxxxxx> wrote: > > > > > > > > On Sat, Apr 30, 2022 at 11:05 AM Huacai Chen <chenhuacai@xxxxxxxxxxx> wrote: > > > > > > > > > > This patch adds zboot (self-extracting compressed kernel) support, all > > > > > existing in-kernel compressing algorithm and efistub are supported. > > > > > > > > > > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx> > > > > > > > > I have no objections to adding a decompressor in principle, and > > > > the implementation seems reasonable. However, I think we should try to > > > > be consistent between architectures. On both arm64 and riscv, the > > > > maintainers decided to not include a decompressor and instead leave > > > > it up to the boot loader to decompress the kernel and enter it from there. > > > X86, ARM32 and MIPS already support self-extracting kernel, and in > > > 5.17 we even support self-extracting modules. So I think a > > > self-extracting kernel is better than a pure compressed kernel. > > > > FYI, kernel modules are not self-extracting. They don't contain the code > > to do the decompression - that is contained within the kernel, and it is > > the kernel that does the decompression. The userspace tooling tells the > > kernel that the module is compressed. > I call "self-extracting" here means we don't need out-of-kernel help: > kernel decompress doesn't need the bootloader, module decompress > doesn't need kmod. As I understand it, it does require out-of-kernel help. The module loading program needs to pass in to the finit_module syscall a flag to tell the kernel to decompress it. See the MODULE_INIT_COMPRESSED_FILE flag. So it's definitely not "self-extracting" by any sense of "self". My definition of "self-extracting" is where a program contains the extractor inside the same image, and when the program is run, it performs the extraction using code contained within the image itself. Your definition would mean a gzipped kernel binary would be able to be called "self-extracting" if the boot loader decompresses it. This is definitely not "self-extracting" in my book. Sorry to be such a pedant. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
