[OpenBIOS] Analysis of current Solaris 8 boot failure on SPARC32

[Mark Cave-Ayland]

On 02/01/11 09:53, Blue Swirl wrote:

>> Based upon this, it would seem that the Solaris kernel allocates a stack for
>> saving state when a trap is called with a base of 0xf0240000, but for some
>> reason we are stacking to a point where we go beyond the memory region
>> allocated for it. I suspect that this is a side effect of a property/device
>> not being setup correctly, but I'm not yet sure what it is. Anyhow, I
>> thought I'd post the results of my investigations so far in case anyone else
>> has any ideas as to what could cause this.
>
> The kernel stack is overflown. Perhaps some recursive loop (iterating
> device tree, since this doesn't happen on real hardware?) never exits,
> or maybe OpenBIOS consumes kernel stack much more than OBP.

Yeah, that's the conclusion I came to although I'm not really familiar 
with the overall Solaris boot process to figure out what should happen 
as opposed to what does happen.

Idly adding a few breakpoints in obp_fortheval_v2(), a couple of 
interesting things stand out:

Breakpoint 1, obp_fortheval_v2 (str=0x11a268 "h# f800.0000 rmap@ swap ! 
", arg0=1247220, arg1=0, arg2=0, arg3=0, arg4=0) at 
../arch/sparc32/romvec.c:428

Firstly, we don't do full region/segment mapping in OpenBIOS (we only 
have 1 level PTEs) but I'm not sure this is relevant here.

Secondly, the majority of the calls to obp_devopen() pass an argument 
string like this 
"/iommu at 0,10000000/sbus at 0,10001000/espdma at 5,8400000/esp at 5,8800000/sd at 2,0:d". 
However, towards the end it changes over to this: 
"/iommu at 0,10000000/sbus at 0,10001000/espdma at 5,8400000/esp at 5,8800000/sd at 2,0:b". 
Maybe the kernel can't find something in the d slice and so switches to 
the b slice as a backup, at which point it runs out of stack space as 
this isn't supposed to happen?


ATB,

Mark.

-- 
Mark Cave-Ayland - Senior Technical Architect
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