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Date: Sat, 3 Aug 2013 17:31:35 +0100
From: Andrew Turner <andrew@fubar.geek.nz>
To: Ian Lepore <ian@FreeBSD.org>
Subject: Re: Kernel Panic on DREAMPLUG: Alignment Fault 1
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On Sat, 03 Aug 2013 08:04:41 -0600
Ian Lepore <ian@FreeBSD.org> wrote:
> On Sat, 2013-08-03 at 08:32 +0100, Andrew Turner wrote:
> > Can you try the patch at [1]. It should fix the stack alignment in
> > exceptions. I suspect gcc is working in this case because it doesn't
> > generate any instructions that rely on the stack alignment, where
> > clang does.
> > 
> > Andrew
> > 
> > [1] http://people.freebsd.org/~andrew/trapframe_align2.diff
> 
> It's actually not clang vs gcc, it's EABI vs OABI on armv5te.  EABI
> fails the same with clang and gcc.
> 
> With your patch and gcc EABI I get:
> 
> ...
> da1: 40.000MB/s transfers
> da1: 15193MB (31116288 512 byte sectors: 255H 63S/T 1936C)
> da1: quirks=0x3<NO_SYNC_CACHE,NO_6_BYTE>
> Fatal kernel mode data abort: 'Alignment Fault 1'
> trapframe: Fatal kernel mode data abort: 'Alignment Fault 1'
> trapframe: Fatal kernel mode data abort: 'Alignment Fault 1'
> trapframe: Fatal kernel mode data abort: 'Alignment Fault 1'
> [lots more lines of that]
> trapframe: Fatal kernel mode data abort: 'Alignment Fault 1'
> trapframe: Fatal kernel mode data abort: 'Alignment Fault 1'
> Fatal kernel mode prefetch abort at 0xFatal kernel mode data abort:
> 'Alignment Fault 1' trapframe: Fatal kernel mode data abort:
> 'Alignment Fault 1' trapframe: Fatal kernel mode data abort:
> 'Alignment Fault 1'
> 
> And it just continued like that for quite a while, mostly data abort
> with the occasional prefetch abort thrown in.  Eventually it locked
> hard.

It looks like I missed setting the alignment in one of the ARMv4/5
macros. I have an updated patch at [1].

[1] http://people.freebsd.org/~andrew/trapframe_align3.diff