[PATCH v2] ntoskrnl.exe: Add emulation of rdmsr for MSR_LSTAR control register.

[Derek Lesho]

v2: Added definition for MSR_LSTAR instead of hard-coding it in.

Signed-off-by: Derek Lesho <dereklesho52 at Gmail.com>
---
 dlls/ntoskrnl.exe/instr.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/dlls/ntoskrnl.exe/instr.c b/dlls/ntoskrnl.exe/instr.c
index 67cdd327ee..2e5b95cbe6 100644
--- a/dlls/ntoskrnl.exe/instr.c
+++ b/dlls/ntoskrnl.exe/instr.c
@@ -473,6 +473,8 @@ WINE_DEFAULT_DEBUG_CHANNEL(int);
 #define REX_R   4
 #define REX_W   8
 
+#define MSR_LSTAR   0xc0000082
+
 #define REGMODRM_MOD( regmodrm, rex )   ((regmodrm) >> 6)
 #define REGMODRM_REG( regmodrm, rex )   (((regmodrm) >> 3) & 7) | (((rex) & REX_R) ? 8 : 0)
 #define REGMODRM_RM( regmodrm, rex )    (((regmodrm) & 7) | (((rex) & REX_B) ? 8 : 0))
@@ -586,6 +588,12 @@ static BYTE *INSTR_GetOperandAddr( CONTEXT *context, BYTE *instr,
 }
 
 
+static void fake_syscall_function(void)
+{
+    TRACE("() stub\n");
+}
+
+
 /***********************************************************************
  *           emulate_instruction
  *
@@ -757,6 +765,25 @@ static DWORD emulate_instruction( EXCEPTION_RECORD *rec, CONTEXT *context )
             context->Rip += prefixlen + 3;
             return ExceptionContinueExecution;
         }
+        case 0x32: /* rdmsr */
+        {
+            int reg = context->Rcx & 0xffffffff;
+            TRACE("rdmsr CR 0x%08x\n", reg);
+            switch (reg)
+            {
+            case MSR_LSTAR:
+            {
+                ULONGLONG syscall_address = (ULONGLONG) fake_syscall_function;
+
+                context->Rdx = (syscall_address >> 32) & 0xffffffff;
+                context->Rax = syscall_address & 0xffffffff;
+            }
+            break;
+            default: return ExceptionContinueSearch;
+            }
+            context->Rip += prefixlen + 2;
+            return ExceptionContinueExecution;
+        }
         case 0xb6: /* movzx Eb, Gv */
         case 0xb7: /* movzx Ew, Gv */
         {
-- 
2.20.1