sh: Don't continue unwinding across interrupts

[deliverable/linux.git] / arch / sh / kernel / dwarf.c

diff --git a/arch/sh/kernel/dwarf.c b/arch/sh/kernel/dwarf.c
index 88d28ec3780a621ecfcb4dba2ea9f670fda86f3a..e51168064e5669b114d903f6917979e3f2786d4e 100644 (file)
--- a/arch/sh/kernel/dwarf.c
+++ b/arch/sh/kernel/dwarf.c
@@ -540,6 +540,8 @@ void dwarf_free_frame(struct dwarf_frame *frame)
        mempool_free(frame, dwarf_frame_pool);
 }
 
+extern void ret_from_irq(void);
+
 /**
  *     dwarf_unwind_stack - unwind the stack
  *
@@ -678,6 +680,24 @@ struct dwarf_frame * dwarf_unwind_stack(unsigned long pc,
        addr = frame->cfa + reg->addr;
        frame->return_addr = __raw_readl(addr);
 
+       /*
+        * Ah, the joys of unwinding through interrupts.
+        *
+        * Interrupts are tricky - the DWARF info needs to be _really_
+        * accurate and unfortunately I'm seeing a lot of bogus DWARF
+        * info. For example, I've seen interrupts occur in epilogues
+        * just after the frame pointer (r14) had been restored. The
+        * problem was that the DWARF info claimed that the CFA could be
+        * reached by using the value of the frame pointer before it was
+        * restored.
+        *
+        * So until the compiler can be trusted to produce reliable
+        * DWARF info when it really matters, let's stop unwinding once
+        * we've calculated the function that was interrupted.
+        */
+       if (prev && prev->pc == (unsigned long)ret_from_irq)
+               frame->return_addr = 0;
+
        return frame;
 
 bail: