Use compressed relocation records instead of raw Elf_Rela records.
This saves around 15% of the total binary size for the all-drivers
image bin-riscv64/ipxe.sbi.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add code to construct a 32-bit page table to map the whole of the
32-bit address space with a fixed offset selected to map iPXE itself
at its link-time address, and to return with paging enabled and the
program counter updated to a virtual address.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Paging provides an alternative to using relocations: instead of
applying relocation fixups to the runtime addresses, we can set up
virtual addressing so that the runtime addresses match the link-time
addresses.
This opens up the possibility of running portions of iPXE directly
from read-only memory (such as a memory-mapped flash device), subject
to the caveats that .data is not yet writable and .bss is not yet
zeroed. This should allow us to run enough code to parse the memory
map from the FDT, identify a suitable RAM block, and physically
relocate ourselves there.
Add code to construct a 64-bit page table (in a single 4kB buffer) to
identity-map as much of the physical address space as possible, to map
iPXE itself at its link-time address, and to return with paging
enabled and the program counter updated to a virtual address. We use
the highest paging level supported by the CPU, to maximise the amount
of the physical address space covered by the identity map.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Split out the runtime relocation logic from sbiprefix.S to a new
library libprefix.S.
Since this logically decouples the process of runtime relocation from
the _sbi_start symbol (currently used to determine the base address
for applying relocations), provide an alternative mechanism for the
relocator to determine the base address.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
