[OpenBIOS] r638 - in trunk/openbios-devel/forth: bootstrap device

[Nick Couchman]

>>> On 2009/12/04 at 14:43, Igor Kovalenko <igor.v.kovalenko at gmail.com> wrote: 
> On Fri, Dec 4, 2009 at 10:28 PM, Blue Swirl <blauwirbel at gmail.com> wrote:
>> On Fri, Dec 4, 2009 at 7:40 PM, Mark Cave-Ayland
>> <mark.cave-ayland at siriusit.co.uk> wrote:
>>> Blue Swirl wrote:
>>>
>>>>> Yup, that's a bug :-)
>>>>
>>>> Enabling DEBUG_MMU (and fixing the bugs...) confirms the MMU problem:
>>>> DMMU dump:
>>>> [46] VA: 8000000, PA: 0,   8k, user, RW, unlocked, ctx 0
>>>> [53] VA: 8002000, PA: 0,   8k, user, RW, unlocked, ctx 0
>>>> [54] VA: 8004000, PA: 0,   8k, user, RW, unlocked, ctx 0
>>>>
>>>> The physical address is the same (0) for all three VA entries. Why?
>>>
>>> Thanks for the independent confirmation (I'll look out for related MMU fixes
>>> in Qemu too).
>>>
>>> I emailed Igor off-list for some pointers, and he suggested enabling
>>> debugging in OpenBIOS by setting CONFIG_DEBUG_OFMEM and re-compiling, which
>>> gives the following output for the 3 memory claims for 0x8000000, 0x8002000
>>> and 0x8004000:
>>>
>>>
>>> OFMEM: ofmem_claim phys=ffffffffffffffff size=0000000000002000
>>> align=0000000000000001
>>> OFMEM: ofmem_map_page_range 0000000000000000 -> 0000000000000000
>>> 0000000000002000 mode 0000000000000032
>>> OFMEM: mapping mode altered virt=0000000000000000 old mode=0000000000000036
>>> new mode=0000000000000032
>>> OFMEM: ofmem_claim_virt virt=ffffffffffffffff size=0000000000002000
>>> align=0000000000000001
>>> OFMEM: ofmem_map_page_range 0000000010000000 -> 0000000000000000
>>> 0000000000002000 mode 0000000000000032
>>>
>>> OFMEM: ofmem_claim phys=ffffffffffffffff size=0000000000002000
>>> align=0000000000000001
>>> OFMEM: ofmem_map_page_range 0000000000002000 -> 0000000000002000
>>> 0000000000002000 mode 0000000000000032
>>> OFMEM: mapping mode altered virt=0000000000002000 old mode=0000000000000036
>>> new mode=0000000000000032
>>> OFMEM: ofmem_claim_virt virt=ffffffffffffffff size=0000000000002000
>>> align=0000000000000001
>>> OFMEM: ofmem_map_page_range 0000000008002000 -> 0000200000000000
>>> 0000000000002000 mode 0000000000000032
>>> OFMEM: ofmem_claim phys=ffffffffffffffff size=0000000000002000
>>> align=0000000000000001
>>>
>>> OFMEM: ofmem_claim phys=ffffffffffffffff size=0000000000002000
>>> align=0000000000000001
>>> OFMEM: ofmem_map_page_range 0000000000004000 -> 0000000000004000
>>> 0000000000002000 mode 0000000000000032
>>> OFMEM: mapping mode altered virt=0000000000004000 old mode=0000000000000036
>>> new mode=0000000000000032
>>> OFMEM: ofmem_claim_virt virt=ffffffffffffffff size=0000000000002000
>>> align=0000000000000001
>>> OFMEM: ofmem_map_page_range 0000000008004000 -> 0000400000000000
>>> 0000000000002000 mode 0000000000000032
>>> OFMEM: ofmem_claim phys=ffffffffffffffff size=0000000000002000
>>> align=0000000000000001
>>>
>>>
>>> With no memory option specified for Qemu, the default setting is 128Mb RAM
>>> (which spans addresses 0 - 0x8000000). So looking at the above we can see
>>> the following effects:
>>>
>>>
>>> i) The base address for the virtual memory allocator is the top of physical
>>> RAM. This doesn't seem too unreasonable.
>>>
>>> ii) The first request allocated at 0x8000000 is mapped to physical RAM
>>> location 0x0. This looks wrong, as normally low pages contain special
>>> registers for various things - perhaps we need some kind of base offset
>>> here?
>>>
>>> iii) The second request allocated at 0x8002000 is mapped to physical RAM
>>> location 0x200000000000. This is definitely wrong since the maximum physical
>>> RAM location is 0x8000000.
>>>
>>> iv) The third request allocated at 0x8004000 is mapped to physical RAM
>>> location 0x400000000000. Again, this is definitely wrong since the maximum
>>> physical RAM location is 0x8000000.
>>>
>>>
>>> So this looks to me like an OpenBIOS issue related to finding physical
>>> memory slots. I wonder if anything which is attempting to access memory over
>>> the physical RAM limit is simply being forced to zero?
>>
>> With this patch, I get a bit further:
>> entry point is 0x4000
>> Evaluating FCode...
>> invalid access of +vd
>>
>> Can't mount root
>>
>> byte-load: exception caught!
>>
>> 0 >
>>
> 
> It actually stops earlier, before mmapping is performed.
> You should not drop high part of phys addr (because it is passed as 2 cells)
> but instead reverse the order in which we assemble address from hi/lo pair.
> 
> This makes it out of loop, but still no real progress further than that:
> 
> Index: openbios-devel/arch/sparc64/lib.c
> ===================================================================
> --- openbios-devel.orig/arch/sparc64/lib.c
> +++ openbios-devel/arch/sparc64/lib.c
> @@ -260,9 +260,8 @@ mmu_map(void)
>      mode = POP();
>      size = POP();
>      virt = POP();
> -    phys = POP();
> -    phys <<= 32;
> -    phys |= POP();
> +    phys = (POP() & 0xffffffff);
> +    phys |= (POP() & 0xffffffff) << 32;
> 
>      ofmem_map(phys, virt, size, mode);
>  }

This still yields the following unhandled exception:

entry point is 0x4000
Evaluating FCode...
Unhandled Exception 0x0000000008000000
PC = 0x00000000ffd10e4c NPC = 0x00000000ffd10e50
Stopping execution

(gdb) l *0x00000000ffd10e4c
0xffd10e4c is in cfetch (../include/openbios/stack.h:34).
29	typedef ucell phandle_t;
30	
31	
32	
33	
34	static inline void PUSH(ucell value) {
35		dstack[++dstackcnt] = (value);
36	}
37	static inline void PUSH_xt( xt_t xt ) { PUSH( (ucell)xt ); }
38	static inline void PUSH_ih( ihandle_t ih ) { PUSH( (ucell)ih ); }

-Nick



--------
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