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  1. JDK
  2. JDK-8024364

Win/x64: os::current_frame() and os::fetch_frame_from_context() returns wrong frame pointer.

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Details

    • Bug
    • Resolution: Won't Fix
    • P4
    • 11
    • 9
    • hotspot
    • x86
    • windows

    Description

      See http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2013-September/009131.html

      src/os_cpu/windows_x86/vm/os_windows_x86.cpp:

           frame os::current_frame() {

           #ifdef AMD64
             // apparently _asm not supported on windows amd64
             typedef intptr_t* get_fp_func ();
             get_fp_func* func = CAST_TO_FN_PTR(get_fp_func*, StubRoutines::x86::get_previous_fp_entry());
             if (func == NULL) return frame();
             intptr_t* fp = (*func)();
           #else
           ...

      The code in get_previous_fp_entry() assumes the we have a frame pointer register (which is not always true), and RBP is that register (which is not always true). In some cases, especially when the C stack is shallow (e.g., when using -XX:ErrorHandlerTest=9), RBP can actually be NULL, because is has never been used by any of the C functions.

      It turns out we also have the same problem in here:

          ExtendedPC os::fetch_frame_from_context(void* ucVoid,
                              intptr_t** ret_sp, intptr_t** ret_fp) {

            ExtendedPC epc;
            CONTEXT* uc = (CONTEXT*)ucVoid;

            if (uc != NULL) {
              epc = ExtendedPC((address)uc->REG_PC);
              if (ret_sp) *ret_sp = (intptr_t*)uc->REG_SP;
              if (ret_fp) *ret_fp = (intptr_t*)uc->REG_FP;
            } else {
              // construct empty ExtendedPC for return value checking
              epc = ExtendedPC(NULL);
              if (ret_sp) *ret_sp = (intptr_t *)NULL;
              if (ret_fp) *ret_fp = (intptr_t *)NULL;
            }

            return epc;
          }

          frame os::fetch_frame_from_context(void* ucVoid) {
            intptr_t* sp;
            intptr_t* fp;
            ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
            return frame(sp, fp, epc.pc());
          }

      There is no guarantee that "fp" would be related to "sp" in any way. It could be NULL, or could be just garbage.

      So the use of os::current_frame() and os::fetch_frame_from_context(_context) is simply wrong on Win/x64. We haven't got much problem because most of the use is in debug code:

          ps() in debug.cpp
          oop::register_oop()

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              Unassigned Unassigned
              iklam Ioi Lam
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                Created:
                Updated:
                Resolved: