1 files changed, 111 insertions, 0 deletions
diff --git a/arch/i386/oprofile/backtrace.c b/arch/i386/oprofile/backtrace.c
new file mode 100644
index 000000000000..52d72e074f7f
--- /dev/null
+++ b/arch/i386/oprofile/backtrace.c
@@ -0,0 +1,111 @@
+/**
+ * @file backtrace.c
+ *
+ * @remark Copyright 2002 OProfile authors
+ * @remark Read the file COPYING
+ *
+ * @author John Levon
+ * @author David Smith
+ */
+
+#include <linux/oprofile.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <asm/ptrace.h>
+
+struct frame_head {
+	struct frame_head * ebp;
+	unsigned long ret;
+} __attribute__((packed));
+
+static struct frame_head *
+dump_backtrace(struct frame_head * head)
+{
+	oprofile_add_trace(head->ret);
+
+	/* frame pointers should strictly progress back up the stack
+	 * (towards higher addresses) */
+	if (head >= head->ebp)
+		return NULL;
+
+	return head->ebp;
+}
+
+/* check that the page(s) containing the frame head are present */
+static int pages_present(struct frame_head * head)
+{
+	struct mm_struct * mm = current->mm;
+
+	/* FIXME: only necessary once per page */
+	if (!check_user_page_readable(mm, (unsigned long)head))
+		return 0;
+
+	return check_user_page_readable(mm, (unsigned long)(head + 1));
+}
+
+/*
+ * |             | /\ Higher addresses
+ * |             |
+ * --------------- stack base (address of current_thread_info)
+ * | thread info |
+ * .             .
+ * |    stack    |
+ * --------------- saved regs->ebp value if valid (frame_head address)
+ * .             .
+ * --------------- struct pt_regs stored on stack (struct pt_regs *)
+ * |             |
+ * .             .
+ * |             |
+ * --------------- %esp
+ * |             |
+ * |             | \/ Lower addresses
+ *
+ * Thus, &pt_regs <-> stack base restricts the valid(ish) ebp values
+ */
+#ifdef CONFIG_FRAME_POINTER
+static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
+{
+	unsigned long headaddr = (unsigned long)head;
+	unsigned long stack = (unsigned long)regs;
+	unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
+
+	return headaddr > stack && headaddr < stack_base;
+}
+#else
+/* without fp, it's just junk */
+static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
+{
+	return 0;
+}
+#endif
+
+
+void
+x86_backtrace(struct pt_regs * const regs, unsigned int depth)
+{
+	struct frame_head *head;
+
+#ifdef CONFIG_X86_64
+	head = (struct frame_head *)regs->rbp;
+#else
+	head = (struct frame_head *)regs->ebp;
+#endif
+
+	if (!user_mode(regs)) {
+		while (depth-- && valid_kernel_stack(head, regs))
+			head = dump_backtrace(head);
+		return;
+	}
+
+#ifdef CONFIG_SMP
+	if (!spin_trylock(&current->mm->page_table_lock))
+		return;
+#endif
+
+	while (depth-- && head && pages_present(head))
+		head = dump_backtrace(head);
+
+#ifdef CONFIG_SMP
+	spin_unlock(&current->mm->page_table_lock);
+#endif
+}