[PATCH] i386: Get ebp from unwinder state when continuing fallback backtrace

Cc: jbeulich@novell.com
Signed-off-by: Andi Kleen <ak@suse.de>

2 files changed, 17 insertions, 8 deletions

diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 86fa7e47f301..bdf949c30c7c 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -171,7 +171,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                 unsigned long *stack,
                 struct stacktrace_ops *ops, void *data)
 {
-        unsigned long ebp;
+        unsigned long ebp = 0;
 
         if (!task)
                 task = current;
@@ -199,6 +199,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                                         stack = (void *)UNW_SP(&info);
                                         if (!stack)
                                                 return;
+                                        ebp = UNW_FP(&info);
                                 } else
                                         ops->warning(data, "Full inexact backtrace again:\n");
                         } else if (call_trace >= 1)
@@ -207,20 +208,25 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                                 ops->warning(data, "Full inexact backtrace again:\n");
                 } else
                         ops->warning(data, "Inexact backtrace:\n");
-        } else  if (!stack) {
+        }
+        if (!stack) {
                 unsigned long dummy;
                 stack = &dummy;
                 if (task && task != current)
                         stack = (unsigned long *)task->thread.esp;
         }
 
-        if (task == current) {
-                /* Grab ebp right from our regs */
-                asm ("movl %%ebp, %0" : "=r" (ebp) : );
-        } else {
-                /* ebp is the last reg pushed by switch_to */
-                ebp = *(unsigned long *) task->thread.esp;
+#ifdef CONFIG_FRAME_POINTER
+        if (!ebp) {
+                if (task == current) {
+                        /* Grab ebp right from our regs */
+                        asm ("movl %%ebp, %0" : "=r" (ebp) : );
+                } else {
+                        /* ebp is the last reg pushed by switch_to */
+                        ebp = *(unsigned long *) task->thread.esp;
+                }
         }
+#endif
 
         while (1) {
                 struct thread_info *context;
diff --git a/include/asm-i386/unwind.h b/include/asm-i386/unwind.h
index 4c1a0b968569..f0ac399bae3c 100644
--- a/include/asm-i386/unwind.h
+++ b/include/asm-i386/unwind.h
@@ -28,6 +28,8 @@ struct unwind_frame_info
 #define FRAME_LINK_OFFSET    0
 #define STACK_BOTTOM(tsk)    STACK_LIMIT((tsk)->thread.esp0)
 #define STACK_TOP(tsk)       ((tsk)->thread.esp0)
+#else
+#define UNW_FP(frame) ((void)(frame), 0)
 #endif
 #define STACK_LIMIT(ptr)     (((ptr) - 1) & ~(THREAD_SIZE - 1))
 
@@ -88,6 +90,7 @@ static inline int arch_unw_user_mode(const struct unwind_frame_info *info)
 
 #define UNW_PC(frame) ((void)(frame), 0)
 #define UNW_SP(frame) ((void)(frame), 0)
+#define UNW_FP(frame) ((void)(frame), 0)
 
 static inline int arch_unw_user_mode(const void *info)
 {