4 files changed, 149 insertions, 1 deletions
diff --git a/arch/arm/oprofile/Makefile b/arch/arm/oprofile/Makefile
index ba1a6e9f2b2..8ffb523e6c7 100644
--- a/arch/arm/oprofile/Makefile
+++ b/arch/arm/oprofile/Makefile
@@ -6,6 +6,6 @@ DRIVER_OBJS = $(addprefix ../../../drivers/oprofile/, \
 		oprofilefs.o oprofile_stats.o \
 		timer_int.o )
 
-oprofile-y				:= $(DRIVER_OBJS) init.o
+oprofile-y				:= $(DRIVER_OBJS) init.o backtrace.o
 oprofile-$(CONFIG_CPU_XSCALE)		+= common.o op_model_xscale.o
 
diff --git a/arch/arm/oprofile/backtrace.c b/arch/arm/oprofile/backtrace.c
new file mode 100644
index 00000000000..ec58d3e2eb8
--- /dev/null
+++ b/arch/arm/oprofile/backtrace.c
@@ -0,0 +1,144 @@
+/*
+ * Arm specific backtracing code for oprofile
+ *
+ * Copyright 2005 Openedhand Ltd.
+ *
+ * Author: Richard Purdie <rpurdie@openedhand.com>
+ *
+ * Based on i386 oprofile backtrace code by John Levon, David Smith
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/oprofile.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <asm/ptrace.h>
+#include <asm/uaccess.h>
+
+
+/*
+ * The registers we're interested in are at the end of the variable
+ * length saved register structure. The fp points at the end of this
+ * structure so the address of this struct is:
+ * (struct frame_tail *)(xxx->fp)-1
+ */
+struct frame_tail {
+	struct frame_tail *fp;
+	unsigned long sp;
+	unsigned long lr;
+} __attribute__((packed));
+
+
+#ifdef CONFIG_FRAME_POINTER
+static struct frame_tail* kernel_backtrace(struct frame_tail *tail)
+{
+	oprofile_add_trace(tail->lr);
+
+	/* frame pointers should strictly progress back up the stack
+	 * (towards higher addresses) */
+	if (tail >= tail->fp)
+		return NULL;
+
+	return tail->fp-1;
+}
+#endif
+
+static struct frame_tail* user_backtrace(struct frame_tail *tail)
+{
+	struct frame_tail buftail;
+
+	/* hardware pte might not be valid due to dirty/accessed bit emulation
+	 * so we use copy_from_user and benefit from exception fixups */
+	if (copy_from_user(&buftail, tail, sizeof(struct frame_tail)))
+		return NULL;
+
+	oprofile_add_trace(buftail.lr);
+
+	/* frame pointers should strictly progress back up the stack
+	 * (towards higher addresses) */
+	if (tail >= buftail.fp)
+		return NULL;
+
+	return buftail.fp-1;
+}
+
+/* Compare two addresses and see if they're on the same page */
+#define CMP_ADDR_EQUAL(x,y,offset) ((((unsigned long) x) >> PAGE_SHIFT) \
+	== ((((unsigned long) y) + offset) >> PAGE_SHIFT))
+
+/* check that the page(s) containing the frame tail are present */
+static int pages_present(struct frame_tail *tail)
+{
+	struct mm_struct * mm = current->mm;
+
+	if (!check_user_page_readable(mm, (unsigned long)tail))
+		return 0;
+
+	if (CMP_ADDR_EQUAL(tail, tail, 8))
+		return 1;
+
+	if (!check_user_page_readable(mm, ((unsigned long)tail) + 8))
+		return 0;
+
+	return 1;
+}
+
+/*
+ * |             | /\ Higher addresses
+ * |             |
+ * --------------- stack base (address of current_thread_info)
+ * | thread info |
+ * .             .
+ * |    stack    |
+ * --------------- saved regs->ARM_fp value if valid (frame_tail address)
+ * .             .
+ * --------------- struct pt_regs stored on stack (struct pt_regs *)
+ * |             |
+ * .             .
+ * |             |
+ * --------------- %esp
+ * |             |
+ * |             | \/ Lower addresses
+ *
+ * Thus, &pt_regs <-> stack base restricts the valid(ish) fp values
+ */
+static int valid_kernel_stack(struct frame_tail *tail, struct pt_regs *regs)
+{
+	unsigned long tailaddr = (unsigned long)tail;
+	unsigned long stack = (unsigned long)regs;
+	unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
+
+	return (tailaddr > stack) && (tailaddr < stack_base);
+}
+
+void arm_backtrace(struct pt_regs const *regs, unsigned int depth)
+{
+	struct frame_tail *tail;
+	unsigned long last_address = 0;
+
+	tail = ((struct frame_tail *) regs->ARM_fp) - 1;
+
+	if (!user_mode(regs)) {
+
+#ifdef CONFIG_FRAME_POINTER
+		while (depth-- && tail && valid_kernel_stack(tail, regs)) {
+			tail = kernel_backtrace(tail);
+		}
+#endif
+		return;
+	}
+
+	while (depth-- && tail && !((unsigned long) tail & 3)) {
+		if ((!CMP_ADDR_EQUAL(last_address, tail, 0)
+			|| !CMP_ADDR_EQUAL(last_address, tail, 8))
+				&& !pages_present(tail))
+			return;
+		last_address = (unsigned long) tail;
+		tail = user_backtrace(tail);
+	}
+}
+
diff --git a/arch/arm/oprofile/init.c b/arch/arm/oprofile/init.c
index cce3d3015eb..d315a3a86c8 100644
--- a/arch/arm/oprofile/init.c
+++ b/arch/arm/oprofile/init.c
@@ -20,6 +20,8 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
 	ret = pmu_init(ops, &op_xscale_spec);
 #endif
 
+	ops->backtrace = arm_backtrace;
+
 	return ret;
 }
 
diff --git a/arch/arm/oprofile/op_arm_model.h b/arch/arm/oprofile/op_arm_model.h
index 2d4caf4781a..2148d07484b 100644
--- a/arch/arm/oprofile/op_arm_model.h
+++ b/arch/arm/oprofile/op_arm_model.h
@@ -24,6 +24,8 @@ struct op_arm_model_spec {
 extern struct op_arm_model_spec op_xscale_spec;
 #endif
 
+extern void arm_backtrace(struct pt_regs * const regs, unsigned int depth);
+
 extern int __init pmu_init(struct oprofile_operations *ops, struct op_arm_model_spec *spec);
 extern void pmu_exit(void);
 #endif /* OP_ARM_MODEL_H */