1 files changed, 29 insertions, 23 deletions

diff --git a/arch/avr32/kernel/traps.c b/arch/avr32/kernel/traps.c
index 7e803f4d7a12..adc01a12d154 100644
--- a/arch/avr32/kernel/traps.c
+++ b/arch/avr32/kernel/traps.c
@@ -49,39 +49,45 @@ out:
         return;
 }
 
+static inline int valid_stack_ptr(struct thread_info *tinfo, unsigned long p)
+{
+        return (p > (unsigned long)tinfo)
+                && (p < (unsigned long)tinfo + THREAD_SIZE - 3);
+}
+
 #ifdef CONFIG_FRAME_POINTER
 static inline void __show_trace(struct task_struct *tsk, unsigned long *sp,
                                 struct pt_regs *regs)
 {
-        unsigned long __user *fp;
-        unsigned long __user *last_fp = NULL;
-
-        if (regs) {
-                fp = (unsigned long __user *)regs->r7;
-        } else if (tsk == current) {
-                register unsigned long __user *real_fp __asm__("r7");
-                fp = real_fp;
-        } else {
-                fp = (unsigned long __user *)tsk->thread.cpu_context.r7;
-        }
+        unsigned long lr, fp;
+        struct thread_info *tinfo;
+
+        tinfo = (struct thread_info *)
+                ((unsigned long)sp & ~(THREAD_SIZE - 1));
+
+        if (regs)
+                fp = regs->r7;
+        else if (tsk == current)
+                asm("mov %0, r7" : "=r"(fp));
+        else
+                fp = tsk->thread.cpu_context.r7;
 
         /*
-         * Walk the stack until (a) we get an exception, (b) the frame
-         * pointer becomes zero, or (c) the frame pointer gets stuck
-         * at the same value.
+         * Walk the stack as long as the frame pointer (a) is within
+         * the kernel stack of the task, and (b) it doesn't move
+         * downwards.
          */
-        while (fp && fp != last_fp) {
-                unsigned long lr, new_fp = 0;
-
-                last_fp = fp;
-                if (__get_user(lr, fp))
-                        break;
-                if (fp && __get_user(new_fp, fp + 1))
-                        break;
-                fp = (unsigned long __user *)new_fp;
+        while (valid_stack_ptr(tinfo, fp)) {
+                unsigned long new_fp;
 
+                lr = *(unsigned long *)fp;
                 printk(" [<%08lx>] ", lr);
                 print_symbol("%s\n", lr);
+
+                new_fp = *(unsigned long *)(fp + 4);
+                if (new_fp <= fp)
+                        break;
+                fp = new_fp;
         }
         printk("\n");
 }