powerpc: PTRACE_PEEKUSR always returns FPR0

There is a bug in using ptrace to access FPRs via PTRACE_PEEKUSR /
PTRACE_POKEUSR. In effect, trying to access any of the FPRs always
really accesses FPR0, which does seriously break debugging :-)

The problem seems to have been introduced by commit 3ad26e5c
(Merge branch 'for-kvm' into next).

[ It is indeed a merge conflict between Paul's FPU/VSX state rework
and my LE patches - Anton ]
Signed-off-by: Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/ptrace.c

@@ -1555,7 +1555,7 @@ long arch_ptrace(struct task_struct *child, long request,
 
 			flush_fp_to_thread(child);
 			if (fpidx < (PT_FPSCR - PT_FPR0))
-				memcpy(&tmp, &child->thread.fp_state.fpr,
+				memcpy(&tmp, &child->thread.TS_FPR(fpidx),
 				       sizeof(long));
 			else
 				tmp = child->thread.fp_state.fpscr;
@@ -1588,7 +1588,7 @@ long arch_ptrace(struct task_struct *child, long request,
 
 			flush_fp_to_thread(child);
 			if (fpidx < (PT_FPSCR - PT_FPR0))
-				memcpy(&child->thread.fp_state.fpr, &data,
+				memcpy(&child->thread.TS_FPR(fpidx), &data,
 				       sizeof(long));
 			else
 				child->thread.fp_state.fpscr = data;