1 files changed, 33 insertions, 5 deletions

diff --git a/arch/i386/oprofile/backtrace.c b/arch/i386/oprofile/backtrace.c
index 21654be3f73..c049ce414f0 100644
--- a/arch/i386/oprofile/backtrace.c
+++ b/arch/i386/oprofile/backtrace.c
@@ -20,7 +20,20 @@ struct frame_head {
 } __attribute__((packed));
 
 static struct frame_head *
-dump_backtrace(struct frame_head * head)
+dump_kernel_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;
+}
+
+static struct frame_head *
+dump_user_backtrace(struct frame_head * head)
 {
 	struct frame_head bufhead[2];
 
@@ -49,7 +62,9 @@ dump_backtrace(struct frame_head * head)
  * |    stack    |
  * --------------- saved regs->ebp value if valid (frame_head address)
  * .             .
- * --------------- struct pt_regs stored on stack (struct pt_regs *)
+ * --------------- saved regs->rsp value if x86_64
+ * |             |
+ * --------------- struct pt_regs * stored on stack if 32-bit
  * |             |
  * .             .
  * |             |
@@ -57,13 +72,26 @@ dump_backtrace(struct frame_head * head)
  * |             |
  * |             | \/ Lower addresses
  *
- * Thus, &pt_regs <-> stack base restricts the valid(ish) ebp values
+ * Thus, regs (or regs->rsp for x86_64) <-> stack base restricts the
+ * valid(ish) ebp values. Note: (1) for x86_64, NMI and several other
+ * exceptions use special stacks, maintained by the interrupt stack table
+ * (IST). These stacks are set up in trap_init() in
+ * arch/x86_64/kernel/traps.c. Thus, for x86_64, regs now does not point
+ * to the kernel stack; instead, it points to some location on the NMI
+ * stack. On the other hand, regs->rsp is the stack pointer saved when the
+ * NMI occurred. (2) For 32-bit, regs->esp is not valid because the
+ * processor does not save %esp on the kernel stack when interrupts occur
+ * in the kernel mode.
  */
 #ifdef CONFIG_FRAME_POINTER
 static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
 {
 	unsigned long headaddr = (unsigned long)head;
+#ifdef CONFIG_X86_64
+	unsigned long stack = (unsigned long)regs->rsp;
+#else
 	unsigned long stack = (unsigned long)regs;
+#endif
 	unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
 
 	return headaddr > stack && headaddr < stack_base;
@@ -90,10 +118,10 @@ x86_backtrace(struct pt_regs * const regs, unsigned int depth)
 
 	if (!user_mode_vm(regs)) {
 		while (depth-- && valid_kernel_stack(head, regs))
-			head = dump_backtrace(head);
+			head = dump_kernel_backtrace(head);
 		return;
 	}
 
 	while (depth-- && head)
-		head = dump_backtrace(head);
+		head = dump_user_backtrace(head);
 }