From mboxrd@z Thu Jan  1 00:00:00 1970
From: linux@arm.linux.org.uk (Russell King - ARM Linux)
Date: Tue, 28 Jun 2011 15:37:59 +0100
Subject: Problem with GDB when debugging IRQ handlers
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Message-ID: <20110628143758.GF21898@n2100.arm.linux.org.uk>
To: linux-arm-kernel@lists.infradead.org
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On Tue, Jun 28, 2011 at 03:30:14PM +0100, Catalin Marinas wrote:
> Actually since the return address is in S_PC (which maybe gdb assumes it
> would be the saved LR), this is probably not be correct. After SVC
> entry, we have he following structure on the stack:
> 
> 	ORIG_r0
> 	CPSR
> 		<--- assuming this is the Call Frame Address (SP+S_PC+4)
> 	PC	<--- CFA - 4
> 	LR	<--- don't care
> 	SP	<--- CFA - 12
> 	...

If I'm reading this correctly, it's not correct.

parent SP -->	parent context stack
		[possible empty word]
		ORIG_r0
		parent context CPSR
		parent context PC
		parent context LR
		parent context SP
		...
new SP -->	R0

That empty word may or may not be present if the parent SP is aligned to
a 64-bit boundary.