linux-kernel - Re: [PATCH] ARM: fix alignement of __bug

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Date:	Tue, 08 Sep 2015 22:46:30 +0200
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Dave Martin <Dave.Martin@....com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: fix alignement of __bug_table section entries

Russell King - ARM Linux <linux@....linux.org.uk> writes:

> What should happen is:
Thanks very much for the explanation, hopefully I have enough material to fly on
my own now.

> Now, when you get the fault inside arm_copy_from_user(), you can
> print the DACR value saved at the time the fault was generated by
> printing the word above struct pt_regs on the stack - add to
> arch/arm/mm/fault.c:do_DataAbort():
>
> if (addr == 0xbf00202c) printk("DACR=0x%08x\n", *(u32 *)(regs + 1));
>
> before the "if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))" line.
> That'll tell us what the DACR register was when we saved it.
>
> If it isn't 0x75, then the next part of the puzzle is going to be
> working out why it isn't.
It's 0x55. I'll track down how this happens, there are not that many places
where DACR is touched, and I'm in a very controlled environement, so I can
cunningly place JTAG breakpoints and watch DACR.

I'll report once I have a better idea what is happening, that might take me a
couple of days given that most of my workforce is available on weekends only.

Thanks again for the free lesson.

-- 
Robert
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