Do not run Legacy16DispatchOprom for VGA OpROM if one isn't present

Author: mintsuki

src/csmwrap.c

@@ -260,15 +260,17 @@ EFI_STATUS efi_main(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
                         NULL,
                         0);
 
-    memset(&Regs, 0, sizeof(EFI_IA32_REGISTER_SET));
-    Regs.X.AX = Legacy16DispatchOprom;
-    Regs.X.ES = EFI_SEGMENT(&priv.low_stub->vga_oprom_table);
-    Regs.X.BX = EFI_OFFSET(&priv.low_stub->vga_oprom_table);
-    LegacyBiosFarCall86(priv.csm_efi_table->Compatibility16CallSegment,
-                        priv.csm_efi_table->Compatibility16CallOffset,
-                        &Regs,
-                        NULL,
-                        0);
+    if (priv.video_type == CSMWRAP_VIDEO_OPROM) {
+        memset(&Regs, 0, sizeof(EFI_IA32_REGISTER_SET));
+        Regs.X.AX = Legacy16DispatchOprom;
+        Regs.X.ES = EFI_SEGMENT(&priv.low_stub->vga_oprom_table);
+        Regs.X.BX = EFI_OFFSET(&priv.low_stub->vga_oprom_table);
+        LegacyBiosFarCall86(priv.csm_efi_table->Compatibility16CallSegment,
+                            priv.csm_efi_table->Compatibility16CallOffset,
+                            &Regs,
+                            NULL,
+                            0);
+    }
 
     memset(&Regs, 0, sizeof(EFI_IA32_REGISTER_SET));
     Regs.X.AX = Legacy16PrepareToBoot;