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

arch/metag/Kconfig

@@ -25,6 +25,7 @@ config METAG
 	select HAVE_MEMBLOCK
 	select HAVE_MEMBLOCK_NODE_MAP
 	select HAVE_MOD_ARCH_SPECIFIC
+	select HAVE_OPROFILE
 	select HAVE_PERF_EVENTS
 	select HAVE_SYSCALL_TRACEPOINTS
 	select IRQ_DOMAIN
@@ -209,6 +210,9 @@ config METAG_PERFCOUNTER_IRQS
 	  When disabled, Performance Counters information will be collected
 	  based on Timer Interrupt.
 
+config HW_PERF_EVENTS
+	def_bool METAG_PERFCOUNTER_IRQS && PERF_EVENTS
+
 config METAG_DA
 	bool "DA support"
 	help

arch/metag/Makefile

@@ -49,6 +49,8 @@ core-y					+= arch/metag/mm/
 libs-y					+= arch/metag/lib/
 libs-y					+= arch/metag/tbx/
 
+drivers-$(CONFIG_OPROFILE)		+= arch/metag/oprofile/
+
 boot					:= arch/metag/boot
 
 boot_targets				+= uImage

arch/metag/oprofile/Makefile

+obj-$(CONFIG_OPROFILE)	+= oprofile.o
+
+oprofile-core-y	+= buffer_sync.o
+oprofile-core-y	+= cpu_buffer.o
+oprofile-core-y	+= event_buffer.o
+oprofile-core-y	+= oprof.o
+oprofile-core-y	+= oprofile_files.o
+oprofile-core-y	+= oprofile_stats.o
+oprofile-core-y	+= oprofilefs.o
+oprofile-core-y	+= timer_int.o
+oprofile-core-$(CONFIG_HW_PERF_EVENTS)	+= oprofile_perf.o
+
+oprofile-y	+= backtrace.o
+oprofile-y	+= common.o
+oprofile-y	+= $(addprefix ../../../drivers/oprofile/,$(oprofile-core-y))
+
+ccflags-y	+= -Werror

arch/metag/oprofile/backtrace.c

+/*
+ * 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);
+	}
+}

arch/metag/oprofile/backtrace.h

+#ifndef _METAG_OPROFILE_BACKTRACE_H
+#define _METAG_OPROFILE_BACKTRACE_H
+
+void metag_backtrace(struct pt_regs * const regs, unsigned int depth);
+
+#endif

arch/metag/oprofile/common.c

+/*
+ * arch/metag/oprofile/common.c
+ *
+ * Copyright (C) 2013 Imagination Technologies Ltd.
+ *
+ * Based on arch/sh/oprofile/common.c:
+ *
+ * Copyright (C) 2003 - 2010  Paul Mundt
+ *
+ * Based on arch/mips/oprofile/common.c:
+ *
+ *	Copyright (C) 2004, 2005 Ralf Baechle
+ *	Copyright (C) 2005 MIPS Technologies, Inc.
+ *
+ * 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/errno.h>
+#include <linux/init.h>
+#include <linux/oprofile.h>
+#include <linux/perf_event.h>
+#include <linux/slab.h>
+
+#include "backtrace.h"
+
+#ifdef CONFIG_HW_PERF_EVENTS
+/*
+ * This will need to be reworked when multiple PMUs are supported.
+ */
+static char *metag_pmu_op_name;
+
+char *op_name_from_perf_id(void)
+{
+	return metag_pmu_op_name;
+}
+
+int __init oprofile_arch_init(struct oprofile_operations *ops)
+{
+	ops->backtrace = metag_backtrace;
+
+	if (perf_num_counters() == 0)
+		return -ENODEV;
+
+	metag_pmu_op_name = kasprintf(GFP_KERNEL, "metag/%s",
+				      perf_pmu_name());
+	if (unlikely(!metag_pmu_op_name))
+		return -ENOMEM;
+
+	return oprofile_perf_init(ops);
+}
+
+void oprofile_arch_exit(void)
+{
+	oprofile_perf_exit();
+	kfree(metag_pmu_op_name);
+}
+#else
+int __init oprofile_arch_init(struct oprofile_operations *ops)
+{
+	ops->backtrace = metag_backtrace;
+	/* fall back to timer interrupt PC sampling */
+	return -ENODEV;
+}
+void oprofile_arch_exit(void) {}
+#endif /* CONFIG_HW_PERF_EVENTS */