metag: OProfile support

Add OProfile support for metag, using the perf backend, and falling back
to generic timer based sampling if perf counter interrupt support is
disabled.

The oprofile code prepends "metag/" to the perf pmu name to give
"metag/meta2" which is more consistent with other oprofile arch names.

The backtrace code makes use of <asm/stacktrace.h> for kernel
backtracing, and a simple frame pointer walk for userland backtracing.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Robert Richter <rric@kernel.org>
Cc: oprofile-list@lists.sf.net

1 files changed, 63 insertions, 0 deletions

diff --git a/arch/metag/oprofile/backtrace.c b/arch/metag/oprofile/backtrace.c
new file mode 100644
index 0000000..7cc3f37
--- /dev/null
+++ b/arch/metag/oprofile/backtrace.c
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2010-2013 Imagination Technologies Ltd.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/oprofile.h>
+#include <linux/uaccess.h>
+#include <asm/processor.h>
+#include <asm/stacktrace.h>
+
+#include "backtrace.h"
+
+static void user_backtrace_fp(unsigned long __user *fp, unsigned int depth)
+{
+	while (depth-- && access_ok(VERIFY_READ, fp, 8)) {
+		unsigned long addr;
+		unsigned long __user *fpnew;
+		if (__copy_from_user_inatomic(&addr, fp + 1, sizeof(addr)))
+			break;
+		addr -= 4;
+
+		oprofile_add_trace(addr);
+
+		/* stack grows up, so frame pointers must decrease */
+		if (__copy_from_user_inatomic(&fpnew, fp + 0, sizeof(fpnew)))
+			break;
+		if (fpnew >= fp)
+			break;
+		fp = fpnew;
+	}
+}
+
+static int kernel_backtrace_frame(struct stackframe *frame, void *data)
+{
+	unsigned int *depth = data;
+
+	oprofile_add_trace(frame->pc);
+
+	/* decrement depth and stop if we reach 0 */
+	if ((*depth)-- == 0)
+		return 1;
+
+	/* otherwise onto the next frame */
+	return 0;
+}
+
+void metag_backtrace(struct pt_regs * const regs, unsigned int depth)
+{
+	if (user_mode(regs)) {
+		unsigned long *fp = (unsigned long *)regs->ctx.AX[1].U0;
+		user_backtrace_fp((unsigned long __user __force *)fp, depth);
+	} else {
+		struct stackframe frame;
+		frame.fp = regs->ctx.AX[1].U0;		/* A0FrP */
+		frame.sp = user_stack_pointer(regs);	/* A0StP */
+		frame.lr = 0;				/* from stack */
+		frame.pc = regs->ctx.CurrPC;		/* PC */
+		walk_stackframe(&frame, &kernel_backtrace_frame, &depth);
+	}
+}