From a795c96752c5d217144bc634a760a74aa0eb54ad Mon Sep 17 00:00:00 2001
From: Shao Miller <sha0.miller@gmail.com>
Date: Wed, 12 Dec 2012 22:47:04 -0500
Subject: [PATCH] [safehook] Note the previous INT 0x13 handler

Cache a record of a safe hook's ancestor in the chain.
---
 src/include/safehook.h         | 3 +++
 src/winvblock/safehook/probe.c | 1 +
 2 files changed, 4 insertions(+)

diff --git a/src/include/safehook.h b/src/include/safehook.h
index abe335e..ff7cfd9 100644
--- a/src/include/safehook.h
+++ b/src/include/safehook.h
@@ -127,6 +127,9 @@ struct S_WV_SAFE_HOOK_BUS {
 
     /** PnP bus relations.  A safe hook can only have one child, at most */
     DEVICE_RELATIONS BusRelations[1];
+
+    /** A record of the previous INT 0x13 handler in the chain */
+    S_X86_SEG16OFF16 PreviousInt13hHandler[1];
   };
 
 #endif  /* WV_M_PROBE_H_ */
diff --git a/src/winvblock/safehook/probe.c b/src/winvblock/safehook/probe.c
index 856d5ce..51a21f0 100644
--- a/src/winvblock/safehook/probe.c
+++ b/src/winvblock/safehook/probe.c
@@ -238,6 +238,7 @@ static NTSTATUS STDCALL WvSafeHookDriveDevice(
     bus->PhysicalDeviceObject = pdo;
     bus->BusRelations->Count = 0;
     bus->BusRelations->Objects[0] = NULL;
+    bus->PreviousInt13hHandler[0] = hook->PrevHook;
 
     /* Attach the FDO to the PDO */
     if (!WvlAttachDeviceToDeviceStack(fdo, pdo)) {