[U-Boot] FW: U-boot & x86 & coreboot

[Rossier Daniel]

Hi Simon,

> -----Original Message-----
> From: sjg at google.com [mailto:sjg at google.com] On Behalf Of Simon Glass
> Sent: mercredi 17 juillet 2013 17:43
> To: Rossier Daniel
> Cc: u-boot at lists.denx.de
> Subject: Re: [U-Boot] U-boot & x86 & coreboot
> 
> Hi Rossier,
> 
> On Wed, Jul 17, 2013 at 2:29 AM, Rossier Daniel <Daniel.Rossier at heig-vd.ch>
> wrote:
> Hi,
> 
> I would like to run U-boot on x86 emulated QEMU-based environment. I
> found some info regarding coreboot + U-boot integration, using U-boot as
> payload, etc. but I was unable to start U-boot.
> I'm using the 32-bits i686-pc-linux-gnu toolchain and I successfully cross-
> compiled coreboot and started it on qemu-system-i386.
> I also configured coreboot to use u-boot (ELF) as payload, but coreboot
> performs a reset when U-boot should show up after loading.
> Where could I have some information regarding that?
> 
> There are post codes generated in x86 U-Boot which might help with
> diagnosing this. I have not tried this on QEMU. But I suppose in that
> environment it might be possible to watch execution and see where it is
> going wrong.

Actually, I was able to dig into further details during the execution.
U-boot is starting its execution, but in early execution in setup_gdt,
the execution of instruction at 0x1111491 leads to a traps (loading 0x18 to %ds).
(see below for details)
I don't really see an issue to execute this instruction.

(gdb) si
0x01111491 in load_ds (segment=3) at cpu.c:61
61              asm volatile("movl %0, %%ds" : : "r" (segment * X86_GDT_ENTRY_SIZE));
(gdb) info reg
eax            0x18     24
ecx            0x19203f20       421543712
edx            0x20     32
ebx            0x19cf9320       433034016
esp            0x19203f10       0x19203f10
ebp            0x11dff0 0x11dff0
esi            0x7ebdc50        132897872
edi            0x1223b0 1188784
eip            0x1111491        0x1111491 <setup_gdt+135>
eflags         0x2      [ ]
cs             0x10     16
ss             0x18     24
ds             0x18     24
es             0x18     24
fs             0x18     24
gs             0x18     24
(gdb) info reg pc
pc: 0x1111491
(gdb) x/10i 0x1111491
=> 0x1111491 <setup_gdt+135>:   mov    %eax,%ds
   0x1111493 <setup_gdt+137>:   mov    %eax,%es
   0x1111495 <setup_gdt+139>:   mov    %eax,%gs
   0x1111497 <setup_gdt+141>:   mov    %eax,%ss
   0x1111499 <setup_gdt+143>:   mov    $0x20,%al
   0x111149b <setup_gdt+145>:   mov    %eax,%fs
   0x111149d <setup_gdt+147>:   add    $0x8,%esp
   0x11114a0 <setup_gdt+150>:   pop    %ebx
   0x11114a1 <setup_gdt+151>:   ret    
   0x11114a2 <x86_cpu_init_r>:  call   0x11109d3 <cpu_init_interrupts>
(gdb) si
0x0000fcb0 in ?? ()
(gdb)

Do you have an idea?

By the way, I'm passing the file u-boot in ELF format directly to coreboot as ELF payload.
Is it better to wrap the file u-boot.bin to get an ELF?

Thanks for your help

Daniel

> 
> Furthermore, I'm unable to debug anything remotely with gdb; gdb cannot
> disassemble once connected via "target remote localhost:1234".
> 
> Do you mean it cannot find the source files?
> 
> Regards,
> Simon
> 
> 
> Any hints welcome.
> Thanks so much.
> 
> Cheers
> Daniel
> 
> 
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