winedbg: Correctly read LDT entries for wow64 debuggee.

programs/winedbg/be_i386.c

@@ -40,7 +40,12 @@ static ADDRESS_MODE get_selector_type(HANDLE hThread, const WOW64_CONTEXT *ctx,
     /* null or system selector */
     if (!(sel & 4) || ((sel >> 3) < first_ldt_entry)) return AddrModeFlat;
     if (dbg_curr_process->process_io->get_selector(hThread, sel, &le))
-        return le.HighWord.Bits.Default_Big ? AddrMode1632 : AddrMode1616;
+    {
+        ULONG base = (le.HighWord.Bits.BaseHi << 24) + (le.HighWord.Bits.BaseMid << 16) + le.BaseLow;
+        if (le.HighWord.Bits.Default_Big)
+            return base == 0 ? AddrModeFlat : AddrMode1632;
+        return AddrMode1616;
+    }
     /* selector doesn't exist */
     return -1;
 }

programs/winedbg/tgt_active.c

@@ -1067,7 +1067,17 @@ static BOOL tgt_process_active_write(HANDLE hProcess, void* addr,
 
 static BOOL tgt_process_active_get_selector(HANDLE hThread, DWORD sel, LDT_ENTRY* le)
 {
+#ifdef _WIN64
+    THREAD_DESCRIPTOR_INFORMATION desc = { .Selector = sel };
+    ULONG retlen;
+
+    if (RtlWow64GetThreadSelectorEntry( hThread, &desc, sizeof(desc), &retlen ))
+        return FALSE;
+    *le = desc.Entry;
+    return TRUE;
+#else
     return GetThreadSelectorEntry( hThread, sel, le );
+#endif
 }
 
 static struct be_process_io be_process_active_io =