On 02/07/20 10:09, Laszlo Ersek wrote: > On 02/06/20 15:03, Ard Biesheuvel wrote: >> This series introduces an arch agnostic way of loading the initrd into >> memory from the EFI stub. This addresses a number of shortcomings that >> affect the current implementations that exist across architectures: >> >> - The initrd=<file> command line option can only load files that reside >> on the same file system that the kernel itself was loaded from, which >> requires the bootloader or firmware to expose that file system via the >> appropriate EFI protocol, which is not always feasible. From the kernel >> side, this protocol is problematic since it is incompatible with mixed >> mode on x86 (this is due to the fact that some of its methods have >> prototypes that are difficult to marshall) >> >> - The approach that is ordinarily taken by GRUB is to load the initrd into >> memory, and pass it to the kernel proper via the bootparams structure or >> via the device tree. This requires the boot loader to have an understanding >> of those structures, which are not always set in stone, and of the policies >> around where the initrd may be loaded into memory. In the ARM case, it >> requires GRUB to modify the hardware description provided by the firmware, >> given that the initrd base and offset in memory are passed via the same >> data structure. It also creates a time window where the initrd data sits >> in memory, and can potentially be corrupted before the kernel is booted. >> >> Considering that we will soon have new users of these interfaces (EFI for >> kvmtool on ARM, RISC-V in u-boot, etc), it makes sense to add a generic >> interface now, before having another wave of bespoke arch specific code >> coming in. >> >> Another aspect to take into account is that support for UEFI secure boot >> and measured boot is being taken into the upstream, and being able to >> rely on the PE entry point for booting any architecture makes the GRUB >> vs shim story much cleaner, as we should be able to rely on LoadImage >> and StartImage on all architectures, while retaining the ability to >> load initrds from anywhere. >> >> Note that these patches depend on a fair amount of cleanup work that I >> am targetting for v5.7. Branch can be found at: >> https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=efistub-unification2 >> >> An implementation for ArmVirtQemu (OVMF for ARM aka AAVMF) can be found >> at https://github.com/ardbiesheuvel/edk2/commits/linux-efi-generic. >> The change is for ARM only, but the exact same code could be used on x86. > > I like this ArmVirtQemu feature, but I think it should be implemented as > an addition, rather than a replacement. Older kernels (older EFI stubs) > will try to fetch the initrd from the same fs where grub loaded the > kernel from (exactly as you describe in the blurb). > > For example, virt-install's "--location" option "can recognize certain > distribution trees and fetches a bootable kernel/initrd pair to launch > the install". It would be nice to keep that working for older distros. > > I think LoadFile[2] can co-exist with SimpleFs. > > I also think that the "try SimpleFs first, fall back to LoadFile[2] > second" requirement applies only to the UEFI boot manager, and not to > the kernel's EFI stub. IOW in the new approach the kernel is free to > ignore (abandon) the old approach for good. ... But that might not be good for compatibility with grub and/or the platform firmware, from the kernel's own perspective, perhaps?... Who is supposed to produce LoadFile2 with the new VenMedia devpath? Thanks Laszlo >> >> Cc: lersek@xxxxxxxxxx >> Cc: leif@xxxxxxxxxxxx >> Cc: pjones@xxxxxxxxxx >> Cc: mjg59@xxxxxxxxxx >> Cc: agraf@xxxxxxxxx >> Cc: ilias.apalodimas@xxxxxxxxxx >> Cc: xypron.glpk@xxxxxx >> Cc: daniel.kiper@xxxxxxxxxx >> >> Ard Biesheuvel (2): >> efi/libstub: add support for loading the initrd from a device path >> efi/libstub: take noinitrd cmdline argument into account for devpath >> initrd >> >> drivers/firmware/efi/libstub/arm-stub.c | 21 ++++-- >> .../firmware/efi/libstub/efi-stub-helper.c | 74 +++++++++++++++++++ >> drivers/firmware/efi/libstub/efistub.h | 13 ++++ >> drivers/firmware/efi/libstub/x86-stub.c | 51 ++++++++++--- >> include/linux/efi.h | 1 + >> 5 files changed, 146 insertions(+), 14 deletions(-) >> >
