[Qemu-devel] Re: [sparc] Unassigned mem read access on writing?

[Artyom Tarasenko <atar4qemu@gmail.com>]

On Sun, Nov 7, 2010 at 3:56 PM, Blue Swirl <blauwirbel@gmail.com> wrote:
> On Fri, Nov 5, 2010 at 5:48 PM, Artyom Tarasenko <atar4qemu@gmail.com> wrote:
>> Trying to boot Solaris 2.1 I get the following error message:
>>
>> Unassigned mem read access of 1 byte to ffffffffffff0768 from f0014768
>> qemu: fatal: Trap 0x29 while interrupts disabled, Error state
>> pc: f0014768  npc: f001476c
>>
>> Looks like a read access to a non-mapped memory (the NF-bit is 0). But
>> where can it happen?
>>
>> The code:
>>
>>   0xf001475c:  mov  0x200, %o4
>> => 0xf0014760:  lda  [ %o4 ] #ASI_N, %o3
>>   0xf0014764:  sta  %o2, [ %o4 ] #ASI_N
>>   0xf0014768:  sta  %g0, [ %o0 ] (3)
>>   0xf001476c:  cmp  %o2, %o3
>>   0xf0014770:  bne  0xf001477c
>> End of assembler dump.
>> (gdb) stepi
>> 0xf0014764 in ?? ()
>> (gdb) info registers o2
>> o2             0x28a    650
>> (gdb) stepi
>> Remote connection closed
>> (gdb)
>>
>> Any ideas how to debug?
>
> All accesses are 32 bits wide. ASI_N is 4 and the other store access
> is to ASI 3 (MMU flush). I don't see how this is possible.
>
> Perhaps PC and NPC are not updated as they should. If you insert a
> breakpoint at the offending instruction, do you get the same error as
> above with the same PC/NPC value?

The crash is the same but it doesn't break. The option -singlestep
makes no difference either.
The log tail of ran with -d in_asm -singlestep:

IN:
0xf0014760:  lda  [ %o4 ] #ASI_M_MMUREGS, %o3
--------------
IN:
0xf0014764:  sta  %o2, [ %o4 ] #ASI_M_MMUREGS
qemu: fatal: Trap 0x29 while interrupts disabled, Error state
pc: f0014768  npc: f001476c


-- 
Regards,
Artyom Tarasenko

solaris/sparc under qemu blog: http://tyom.blogspot.com/