Current RISC-V and AArch64 kernels found in the wild tend not to be in
the documented kernel format, but are instead "EFI zboot" kernels
comprising a small EFI executable that decompresses and executes the
inner payload (which is a kernel in the expected format).
The EFI zboot header includes a recognisable magic value "zimg" along
with two fields describing the offset and length of the compressed
payload. We can therefore treat this as an archive image format,
extracting the payload as-is and then relying on our existing ability
to execute compressed images.
This is sufficient to allow iPXE to execute the Fedora 42 RISC-V
kernel binary as currently published.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The RISC-V and AArch64 bare-metal kernel images share a common header
format, and require essentially the same execution environment: loaded
close to the start of RAM, entered with paging disabled, and passed a
pointer to a flattened device tree that describes the hardware and any
boot arguments.
Implement basic support for executing bare-metal RISC-V and AArch64
kernel images. The (trivial) AArch64-specific code path is untested
since we do not yet have the ability to build for any bare-metal
AArch64 platforms. Constructing and passing an initramfs image is not
yet supported.
Rename the IMAGE_BZIMAGE build configuration option to IMAGE_LKRN,
since "bzImage" is specific to x86. To retain backwards compatibility
with existing local build configurations, we leave IMAGE_BZIMAGE as
the enabled option in config/default/pcbios.h and treat IMAGE_LKRN as
a synonym for IMAGE_BZIMAGE when building for x86 BIOS.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
