--- /dev/null
+/*
+ * 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);
+ }
+}
+
git.openpandora.org / pandora-kernel.git / commitdiff