powerpc/perf: Use perf_instruction_pointer in callchains

We use SIAR or regs->nip for the instruction pointer depending on
the PMU configuration, but we always use regs->nip in the callchain.

Use perf_instruction_pointer so the backtrace is consistent.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
index e8a18d1..74d1e78 100644
--- a/arch/powerpc/perf/callchain.c
+++ b/arch/powerpc/perf/callchain.c
@@ -57,7 +57,7 @@
 
 	lr = regs->link;
 	sp = regs->gpr[1];
-	perf_callchain_store(entry, regs->nip);
+	perf_callchain_store(entry, perf_instruction_pointer(regs));
 
 	if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
 		return;
@@ -238,7 +238,7 @@
 	struct signal_frame_64 __user *sigframe;
 	unsigned long __user *fp, *uregs;
 
-	next_ip = regs->nip;
+	next_ip = perf_instruction_pointer(regs);
 	lr = regs->link;
 	sp = regs->gpr[1];
 	perf_callchain_store(entry, next_ip);
@@ -444,7 +444,7 @@
 	long level = 0;
 	unsigned int __user *fp, *uregs;
 
-	next_ip = regs->nip;
+	next_ip = perf_instruction_pointer(regs);
 	lr = regs->link;
 	sp = regs->gpr[1];
 	perf_callchain_store(entry, next_ip);