[Qemu-devel] vexpress-a9: coreboot is unable to push any data on stack

[Piotr Król]

Hi all,
I'm trying to boot latest coreboot on qemu-system-arm (-M vexpress-a9).
I compiled qemu arm-softmmu from source (latest code) and trying to boot
with:

qemu-system-arm -M vexpress-a9 -m 1024M -nographic -bios build/coreboot.rom

First of all mtree looks strange because there are two aliases to one
memory region:

0000000000000000-0000000003ffffff (prio 0, RW): alias  vexpress.flashalias 
@vexpress.flash0 0000000000000000-0000000003ffffff
0000000000000000-0000000003ffffff (prio 0, RW): alias  vexpress.lowmem 
@vexpress.highmem 0000000000000000-0000000003ffffff

Is this ok ?

Second, because VE_NORFLASHALIAS was change to 0 here:
http://git.qemu.org/?p=qemu.git;a=commit;h=6ec1588e09770ac7e9c60194faff6101111fc7f0

I was unable to boot coreboot using:
qemu-system-arm -M vexpress-a9 -m 1024M -nographic -kernel build/coreboot.rom

If I change VE_NORFLASHALIAS to -1 like it was before coreboot boots using
'-kernel' parameter, but '-bios' flag even then doesn't work.

Third, (for '-bios' case) thing is that coreboot is unable to push any value on
stack. Instructions related to stack change stack pointer but stack address
memory dump show only 0xffffffff. Coreboot perform stack initialization on its
own.

Disassembled coreboot bootblock with stack initialization is here:
https://gist.github.com/pietrushnic/f83d5d0e5d8d1b75d4c2

The code flow is:
_rom
|-> reset
    |-> init_stack_loop
        |-> call_bootblock
            |-> main
                |-> armv7_invalidate_caches
                    |-> icache_invalidate_all
                    |-> dcache_invalidate_all
                      |-> dcache_foreach

At the begging of dcache_foreach we execute:
stmdb  sp!, {r0, r1, r4, r5, r6, r7, r9, sl, fp, lr}

And at the end there is:
ldmia.w sp!, {r2, r3, r4, r5, r6, r7, r9, r10, r11, pc}

Unfortunately, as I wrote, on stack we have all 0xffffffff that's why
dcache_foreach finish emulation with:

qemu: fatal: Trying to execute code outside RAM or ROM at 0xfffffffe

Any idea how to debug this issue or why it happens in that way ?
What could be the reason of unusable stack memory ?

P.S. Before I started thread here there was a discussion on coreboot mailing 
list:
http://www.coreboot.org/pipermail/coreboot/2014-August/078378.html

Thanks,
Piotr