Re: [Qemu-devel] vexpress-a9 aborts when booting decompress code from a modified Linux kernel

[Peter Maydell]

On 16 October 2015 at 18:57, Ilya Lipnitskiy <address@hidden> wrote:
> On Fri, Oct 16, 2015 at 10:37 AM, Peter Maydell
> <address@hidden> wrote:
>> It would be helpful if you said what the abort actually was
>> (ie what instruction do we abort on, what are the fault status/
>> fault address registers if applicable, etc).
> I should have been more specific. Running trunk qemu on the patched
> zImage with qemu-system-arm -M vexpress-a9 -kernel
> linux/arch/arm/boot/zImage -serial stdio -dtb
> linux/arch/arm/boot/dts/vexpress-v2p-ca9.dtb -s -S then attaching gdb
> generates the following information. I haven't nailed the actual
> instruction causing the abort yet. Is it obvious from the registers?
>
> (gdb) target remote :1234
> Remote debugging using :1234
> 0x60000000 in ?? ()
> (gdb) c
> Continuing.
> ^C
> Program received signal SIGINT, Interrupt.
> __vectors_start () at arch/arm/kernel/entry-armv.S:1240
> 1240        W(b)    vector_pabt

This doesn't really provide enough information to say,
because what will happen is that we take a fault for
some reason, and then because the vectors start at 0
and are empty we will typically take another fault trying
to execute at the vector for the first fault, and then
sit in a loop faulting indefinitely.

You might find it helpful to turn on QEMU's debug logging
(see the -d and -D options). Chances are that some insn
in your new code is faulting (probably UNDEFing).

thanks
-- PMM