Make peeking back into the stack work for back traces

GCC 10 doesn't like peeking back before the end of an arrary (which
is used to peek into the stack).  Fix this.

https://github.com/vmware/open-vm-tools/issues/429

diff --git a/open-vm-tools/lib/user/utilBacktrace.c b/open-vm-tools/lib/user/utilBacktrace.c
index dca33d2675b0e3064715bdbaf3533cd2b7a588f2..d3acd2dd0bc74ff56f54c8f17895c877a0f79e87 100644 (file)
--- a/open-vm-tools/lib/user/utilBacktrace.c
+++ b/open-vm-tools/lib/user/utilBacktrace.c
@@ -1,5 +1,5 @@
 /*********************************************************
- * Copyright (C) 2013-2019 VMware, Inc. All rights reserved.
+ * Copyright (C) 2013-2020 VMware, Inc. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU Lesser General Public License as published
@@ -343,7 +343,8 @@ UtilBacktraceFromPointerWithFunc(uintptr_t *basePtr,       // IN:
                                i, x[0], x[1], dli.dli_sname, dli.dli_fname,
                                 dli.dli_fbase);
       } else {
-         outFunc(outFuncData, "SymBacktrace[%d] %#08x eip %#08x \n", i, x[0], x[1]);
+         outFunc(outFuncData, "SymBacktrace[%d] %#08x eip %#08x \n", i, x[0],
+                 x[1]);
       }
       x = (uintptr_t *) x[0];
    }
@@ -394,6 +395,7 @@ Util_Backtrace(int bugNr) // IN
  *-----------------------------------------------------------------------------
  */
 
+
 void
 Util_BacktraceWithFunc(int bugNr,                // IN:
                        Util_OutputFunc outFunc,  // IN:
@@ -413,7 +415,7 @@ Util_BacktraceWithFunc(int bugNr,                // IN:
    if (bugNr == 0) {
       outFunc(outFuncData, "Backtrace:\n");
    } else {
-      outFunc(outFuncData, "Backtrace for bugNr=%d\n",bugNr);
+      outFunc(outFuncData, "Backtrace for bugNr=%d\n", bugNr);
    }
    frames = backtrace(callstack, ARRAYSIZE(callstack));
    for (i = 0; i < frames; i++) {
@@ -431,13 +433,14 @@ Util_BacktraceWithFunc(int bugNr,                // IN:
       }
    }
 #else
-   uintptr_t *x = (uintptr_t *) &bugNr;
-
    if (bugNr == 0) {
       outFunc(outFuncData, "Backtrace:\n");
    } else {
-      outFunc(outFuncData, "Backtrace for bugNr=%d\n",bugNr);
+      outFunc(outFuncData, "Backtrace for bugNr=%d\n", bugNr);
    }
-   UtilBacktraceFromPointerWithFunc(&x[-2], outFunc, outFuncData);
+
+   UtilBacktraceFromPointerWithFunc(__builtin_frame_address(0), outFunc,
+                                    outFuncData);
 #endif
 }
+