[tkreuzer] 76019: [RTL/x64] Support frames to skip in flags to RtlWalkFrameChain

Author: tkreuzer
Date: Sun Oct  1 14:34:26 2017
New Revision: 76019

URL: http://svn.reactos.org/svn/reactos?rev=76019&view=rev
Log:
[RTL/x64] Support frames to skip in flags to RtlWalkFrameChain

Modified:
    trunk/reactos/sdk/lib/rtl/amd64/unwind.c

Modified: trunk/reactos/sdk/lib/rtl/amd64/unwind.c
URL: http://svn.reactos.org/svn/reactos/trunk/reactos/sdk/lib/rtl/amd64/unwind.c?...
==============================================================================
--- trunk/reactos/sdk/lib/rtl/amd64/unwind.c	[iso-8859-1] (original)
+++ trunk/reactos/sdk/lib/rtl/amd64/unwind.c	[iso-8859-1] Sun Oct  1 14:34:26 2017
@@ -524,10 +524,13 @@
     ULONG64 ControlPc, ImageBase, EstablisherFrame;
     ULONG64 StackLow, StackHigh;
     PVOID HandlerData;
-    ULONG i;
+    ULONG i, FramesToSkip;
     PRUNTIME_FUNCTION FunctionEntry;

DPRINT("Enter RtlWalkFrameChain\n");
+
+    /* The upper bits in Flags define how many frames to skip */
+    FramesToSkip = Flags >> 8;

/* Capture the current Context */
     RtlCaptureContext(&Context);
@@ -537,12 +540,12 @@
     RtlpGetStackLimits(&StackLow, &StackHigh);

/* Check if we want the user-mode stack frame */
-    if (Flags == 1)
+    if (Flags & 1)
     {
     }

/* Loop the frames */
-    for (i = 0; i < Count; i++)
+    for (i = 0; i < FramesToSkip + Count; i++)
     {
         /* Lookup the FunctionEntry for the current ControlPc */
         FunctionEntry = RtlLookupFunctionEntry(ControlPc, &ImageBase, NULL);
@@ -579,9 +582,14 @@
             break;
         }

-        /* Save this frame and continue with new Rip */
+        /* Continue with new Rip */
         ControlPc = Context.Rip;
-        Callers[i] = (PVOID)ControlPc;
+
+        /* Save value, if we are past the frames to skip */
+        if (i >= FramesToSkip)
+        {
+            Callers[i - FramesToSkip] = (PVOID)ControlPc;
+        }
     }

DPRINT("RtlWalkFrameChain returns %ld\n", i);
@@ -605,14 +613,8 @@
      * RtlWalkFrameChain -> RtlGetCallersAddress -> x -> y */
     Number = RtlWalkFrameChain(Callers, 4, 0);

-    if (CallersAddress)
-    {
-        *CallersAddress = (Number >= 3) ? Callers[2] : NULL;
-    }
-    if (CallersCaller)
-    {
-        *CallersCaller = (Number == 4) ? Callers[3] : NULL;
-    }
+    *CallersAddress = (Number >= 3) ? Callers[2] : NULL;
+    *CallersCaller = (Number == 4) ? Callers[3] : NULL;

return;
 }