[GSoC] coreboot for ARM64 Qemu – Week #6

This week I worked on completing the build and sorting all complications imposed by it. As I talked in the last post, I was facing some issues regarding setting up smp for this port. I solved this issue by adding an assembly file which declared smp_processor_id and then defined it by setting the right registers. I had to do some background reading on arm64 details. This provided me with the information I needed.

Next up, was another hitch. During the build, ‘mmu_enable()’ and ‘arch_secondary_cpu_init()’ function calls are happening for all stages but the definitions for these functions are getting compiled only for ramstage. So this gave recurrent errors since the compiler couldn’t find these definitions. While attempting to sort this, I stumbled across something on the chromium tree. There was a patch which dealt with some of the issues, similar to mine. I had to cherry pick and apply this change.

After debugging and sorting through some more errors, I was finally able to get it to build successfully.

coreboot.rom: 4096 kB, bootblocksize 37008, romsize 4194304, offset 0x90c0 alignment: 64 bytes, architecture: arm64

Name                                       Offset     Type         Size
fallback/romstage               0x90c0     stage        12108
fallback/ramstage               0xc080     stage        17768
config                                    0x10640    raw          2034
revision                                0x10e80    raw          577
(empty)                                 0x11100    null         4124312
      HOSTCC     cbfstool/rmodtool.o
     HOSTCC     cbfstool/rmodule.o
     HOSTCC     cbfstool/rmodtool (link)
The complete build can be found here.
I attempted to boot off on qemu after this,
$qemu-system-aarch64 -machine type=virt -nographic -bios ~/coreboot/build/coreboot.rom
This did not give any output, which meant probably I had to make some changes in the uart set up. I attempted to debug this by adding few printks early in bootblock once the console_init is done. This process ongoing, I hope to get through. Another aspect in question is the bootblock initialisation. The src/arch/arm64/armv8/bootblock_simple.c calls for an appropriate bootblock_cpu_init(). This is another thing I will be working on in the coming days.