Rust调用WMI的ExecMethod操作xeniface驱动遇问题求助

背景 #

wmi-rs 0.13.1尚未封装ExecMethod，需直接依赖windows-rs 0.48调用WMI方法以操作Xeniface驱动，当前遇到三个核心问题，以下是针对性解决思路及代码参考：

问题1：调用GetMethod返回WBEM_E_ILLEGAL_OPERATION错误 #

该错误源于目标WMI方法的Provider未暴露元数据，不支持通过GetMethod进行参数自省。无需纠结该方法，直接手动构造输入参数对象即可。

问题2：向ExecMethod传递in_params传入会话名称 #

跳过GetMethod，手动构造输入参数实例：

1. 通过IWbemServices::GetObject获取目标WMI类的IWbemClassObject实例；
2. 调用IWbemClassObject::SpawnInstance(0)创建输入参数的空实例；
3. 使用IWbemClassObject::Put方法设置会话名称对应的参数（需确认参数名，比如Python实现中的SessionName）；
4. 将构造好的in_params传入IWbemServices::ExecMethod。

问题3：从out_params提取ReturnValue返回WBEM_E_NOT_FOUND及自省IWbemClassObject #

• WBEM_E_NOT_FOUND解决：先确认方法的实际输出参数名，部分WMI方法的返回值可能不是ReturnValue，需先枚举属性确认存在性；
• 自省IWbemClassObject：调用IWbemClassObject::GetNames枚举所有属性名称，再逐个调用Get方法获取对应值，示例见下方代码。

代码参考 #

Python等效实现 #

import wmi

c = wmi.WMI(namespace="root\\virtualization\\v2")
service = c.Msvm_VirtualSystemManagementService()[0]
params = service.Methods('GetSessionId').InParameters
params.SessionName = "MySession"
result = service.ExecMethod_('GetSessionId', params)
print(result.ReturnValue)

当前Rust代码 #

use windows::{
    core::*,
    Win32::{
        System::Wmi::*,
        Foundation::*,
    },
};

fn main() -> Result<()> {
    let locator = CoCreateInstance::<IWbemLocator>(&WBEM_LOCATOR_CLSID, None, CLSCTX_INPROC_SERVER)?;
    let services = locator.ConnectServer(
        &BSTR::from("root\\virtualization\\v2"),
        None, None, None, 0, None, None,
    )?;

    CoSetProxyBlanket(
        &services,
        RPC_C_AUTHN_WINNT,
        RPC_C_AUTHZ_NONE,
        None,
        RPC_C_AUTHN_LEVEL_CALL,
        RPC_C_IMP_LEVEL_IMPERSONATE,
        None,
        EOAC_NONE,
    )?;

    // 问题1：调用GetMethod失败
    let mut method_def = None;
    let mut in_params_def = None;
    let hr = services.GetObject(
        &BSTR::from("Msvm_VirtualSystemManagementService"),
        0,
        None,
        &mut method_def,
        None,
    )?;
    if let Some(method_def) = method_def {
        let hr = method_def.GetMethod(&BSTR::from("GetSessionId"), 0, &mut in_params_def, None);
        println!("GetMethod hr: {:?}", hr); // 返回WBEM_E_ILLEGAL_OPERATION
    }

    // 手动构造in_params
    let mut class_obj = None;
    services.GetObject(&BSTR::from("Msvm_VirtualSystemManagementService"), 0, None, &mut class_obj, None)?;
    let mut in_params = None;
    class_obj.as_ref().unwrap().SpawnInstance(0, &mut in_params)?;
    let session_name = BSTR::from("MySession");
    in_params.as_ref().unwrap().Put(
        &BSTR::from("SessionName"),
        0,
        &VARIANT::from(&session_name),
        0,
    )?;

    // 调用ExecMethod
    let mut out_params = None;
    let hr = services.ExecMethod(
        &BSTR::from("Msvm_VirtualSystemManagementService"),
        &BSTR::from("GetSessionId"),
        0,
        None,
        in_params.as_ref(),
        &mut out_params,
        None,
    )?;
    println!("ExecMethod hr: {:?}", hr);

    // 问题3：提取ReturnValue失败及自省属性
    if let Some(out_params) = out_params {
        let mut value = VARIANT::default();
        let hr = out_params.Get(&BSTR::from("ReturnValue"), 0, &mut value, None, None);
        println!("Get ReturnValue hr: {:?}", hr); // 返回WBEM_E_NOT_FOUND

        // 枚举所有输出属性
        let mut names = Vec::new();
        let mut name_ptr = std::ptr::null_mut();
        let hr = out_params.GetNames(None, WBEM_FLAG_ALWAYS | WBEM_FLAG_NONSYSTEM_ONLY, None, &mut name_ptr);
        if hr.is_ok() {
            let mut i = 0;
            loop {
                let name = unsafe { *name_ptr.add(i) };
                if name.is_null() {
                    break;
                }
                names.push(BSTR::from_raw(name).to_string());
                i += 1;
            }
            unsafe { CoTaskMemFree(name_ptr as _) };
            println!("Out params names: {:?}", names);
        }
    }

    Ok(())
}

运行输出 #

GetMethod hr: Error { code: 0x80041016, message: "非法操作。" }
ExecMethod hr: Ok(())
Get ReturnValue hr: Error { code: 0x80041002, message: "找不到指定的对象。" }
Out params names: ["SessionId"]

内容的提问来源于stack exchange，提问作者Yann Dirson