On Wed, 1 May 2019, Atish Patra wrote: > Currently, last stage boot loaders such as U-Boot can accept only > uImage which is an unnecessary additional step in automating boot flows. > > Add a PE/COFF compliant image header that boot loaders can parse and > directly load kernel flat Image. The existing booting methods will continue > to work as it is. > > Another goal of this header is to support EFI stub for RISC-V in future. > EFI specification needs PE/COFF image header in the beginning of the kernel > image in order to load it as an EFI application. In order to support > EFI stub, code0 should be replaced with "MZ" magic string and res5(at > offset 0x3c) should point to the rest of the PE/COFF header (which will > be added during EFI support). > > Tested on both QEMU and HiFive Unleashed using OpenSBI + U-Boot + Linux. > > Signed-off-by: Atish Patra <[email protected]>
Seems like we're stuck with this basic format for EFI, etc. Even though we may be stuck with it, I think we should take the opportunity to add the possibility to extending this header format by adding fields after the basic PE/COFF header ends. In particular, at the very least, I'd suggest adding a u32 after the PE/COFF header ends, to represent a "RISC-V header format version number". Then if we add more fields that follow the PE/COFF header -- for example, to represent the RISC-V instruction set extensions that are required to run this binary -- we can just bump that RISC-V-specific version number field to indicate to bootloaders that there's more there. One other observation - if what's here was copied from some other architecture, like ARM, please acknowledge the source in the patch description. thanks - Paul
