On Thu, Feb 16, 2012 at 09:18:10PM +0100, Uwe Kleine-K?nig wrote:

+	.macro	v7m_exception_entry
+	cpsid	i
+	tst	lr, #0x8		@ check the return stack
+	bne	1f			@ exception on process stack
+	add	r12, sp, #32		@ MSP before exception
+	stmdb	sp!, {r4-r12, lr}	@ push unsaved registers
+	b	2f
+1:
+	mrs	r12, psp		@ get the process stack
+	sub	sp, #S_FRAME_SIZE
+	stmia	sp, {r4-r12, lr}	@ push unsaved registers
+	ldmia	r12, {r0-r3, r6, r8-r10} @ load automatically saved registers
+	add	r12, sp, #S_R0
+	stmia	r12, {r0-r3, r6, r8-r10} @ fill in the rest of struct pt_regs

I guess this means that pt_regs no longer contains r0..pc, cpsr, old_r0
on this Cortex-M ?

If so, that's a problem - tools like gdb, strace, and other user programs
which make use of siginfo stuff all expect ARM to have a certain ptrace
layout.  This is major ABI breakage.