【UEFI实战】网络启动

柔情只为你懂 2023-10-06 11:05 6阅读 0赞

## 简述 ##

UEFI下实现了若干中网络启动的方式，比如HTTP启动，PXE启动等。对应的默认如下：

!if $(PXE_ENABLE) == TRUE
      NetworkPkg/UefiPxeBcDxe/UefiPxeBcDxe.inf
    !endif
    !if $(HTTP_BOOT_ENABLE) == TRUE
      NetworkPkg/DnsDxe/DnsDxe.inf
      NetworkPkg/HttpUtilitiesDxe/HttpUtilitiesDxe.inf
      NetworkPkg/HttpDxe/HttpDxe.inf
      NetworkPkg/HttpBootDxe/HttpBootDxe.inf
    !endif

从它们的宏定义就可以看出来具体HTTP启动和PXE启动对应哪些代码。下面分别介绍这两种网络启动方式。

## PXE启动 ##

PXE网路启动是一种比较老的网路启动方式，在[PXE简介及使用说明][PXE]有介绍具体的使用方式，而这里主要介绍它的实现。首先查看NetworkPkg\\UefiPxeBcDxe\\UefiPxeBcDxe.inf文件，从这里可以看到它实际上实现了两个Protocol用于包装整个PXE的动作：

[Protocols]
      ## TO_START
      ## SOMETIMES_CONSUMES
      gEfiDevicePathProtocolGuid                           
      gEfiNetworkInterfaceIdentifierProtocolGuid_31        ## SOMETIMES_CONSUMES
      gEfiArpServiceBindingProtocolGuid                    ## TO_START
      gEfiArpProtocolGuid                                  ## TO_START
      gEfiIp4ServiceBindingProtocolGuid                    ## TO_START
      gEfiIp4ProtocolGuid                                  ## TO_START
      gEfiIp4Config2ProtocolGuid                           ## TO_START
      gEfiIp6ServiceBindingProtocolGuid                    ## TO_START
      gEfiIp6ProtocolGuid                                  ## TO_START
      gEfiIp6ConfigProtocolGuid                            ## TO_START
      gEfiUdp4ServiceBindingProtocolGuid                   ## TO_START
      gEfiUdp4ProtocolGuid                                 ## TO_START
      gEfiMtftp4ServiceBindingProtocolGuid                 ## TO_START
      gEfiMtftp4ProtocolGuid                               ## TO_START
      gEfiDhcp4ServiceBindingProtocolGuid                  ## TO_START
      gEfiDhcp4ProtocolGuid                                ## TO_START
      gEfiUdp6ServiceBindingProtocolGuid                   ## TO_START
      gEfiUdp6ProtocolGuid                                 ## TO_START
      gEfiMtftp6ServiceBindingProtocolGuid                 ## TO_START
      gEfiMtftp6ProtocolGuid                               ## TO_START
      gEfiDhcp6ServiceBindingProtocolGuid                  ## TO_START
      gEfiDhcp6ProtocolGuid                                ## TO_START
      gEfiDns6ServiceBindingProtocolGuid                   ## SOMETIMES_CONSUMES
      gEfiDns6ProtocolGuid                                 ## SOMETIMES_CONSUMES
      gEfiPxeBaseCodeCallbackProtocolGuid                  ## SOMETIMES_PRODUCES
      gEfiPxeBaseCodeProtocolGuid                          ## BY_START
      gEfiLoadFileProtocolGuid                             ## BY_START
      gEfiAdapterInformationProtocolGuid                   ## SOMETIMES_CONSUMES

这里的BY\_START表示的是生成Protocol，可以直接在NetworkPkg\\UefiPxeBcDxe\\PxeBcDriver.c中找到它们的安装代码：

//
      // Create a new handle for IPv4 virtual nic,
      // and install PxeBaseCode, LoadFile and DevicePath protocols.
      //
      Status = gBS->InstallMultipleProtocolInterfaces (
                      &Private->Ip4Nic->Controller,
                      &gEfiDevicePathProtocolGuid,
                      Private->Ip4Nic->DevicePath,
                      &gEfiLoadFileProtocolGuid,
                      &Private->Ip4Nic->LoadFile,
                      &gEfiPxeBaseCodeProtocolGuid,
                      &Private->PxeBc,
                      NULL
                      );

实际上会安装两次，对应IPv4和IPv6，我们还是以IPv4为例，可以看到这里除了安装上文提到的两个Protocol，还安装了Device Path Protocol，它是作为通用需求安装的，这里不做特别说明。

///
    /// The EFI_LOAD_FILE_PROTOCOL is a simple protocol used to obtain files from arbitrary devices.
    ///
    struct _EFI_LOAD_FILE_PROTOCOL {
      EFI_LOAD_FILE LoadFile;
    };

它就是一个获取文件的接口。事实上PXE说到底也只是一个通过网络获取BootLoader的过程，所以这里的接口也很符合。还需要说明，事实上HTTP启动也是实现了这个接口，因为它也只是通过网络获取BootLoader而已。

LoadFile的实现如下（NetworkPkg\\UefiPxeBcDxe\\PxeBcImpl.c）：

EFI_LOAD_FILE_PROTOCOL  gLoadFileProtocolTemplate = { EfiPxeLoadFile };

它的具体实现是以来于的PxeBc。

gEfiPxeBaseCodeProtocolGuid对应的Protocol稍微复杂些（MdePkg\\Include\\Protocol\\PxeBaseCode.h）：

///
    /// The EFI_PXE_BASE_CODE_PROTOCOL is used to control PXE-compatible devices.
    /// An EFI_PXE_BASE_CODE_PROTOCOL will be layered on top of an
    /// EFI_MANAGED_NETWORK_PROTOCOL protocol in order to perform packet level transactions.
    /// The EFI_PXE_BASE_CODE_PROTOCOL handle also supports the
    /// EFI_LOAD_FILE_PROTOCOL protocol. This provides a clean way to obtain control from the
    /// boot manager if the boot path is from the remote device.
    ///
    struct _EFI_PXE_BASE_CODE_PROTOCOL {
      ///
      ///  The revision of the EFI_PXE_BASE_CODE_PROTOCOL. All future revisions must 
      ///  be backwards compatible. If a future version is not backwards compatible 
      ///  it is not the same GUID.
      ///
      UINT64                            Revision;
      EFI_PXE_BASE_CODE_START           Start;
      EFI_PXE_BASE_CODE_STOP            Stop;
      EFI_PXE_BASE_CODE_DHCP            Dhcp;
      EFI_PXE_BASE_CODE_DISCOVER        Discover;
      EFI_PXE_BASE_CODE_MTFTP           Mtftp;
      EFI_PXE_BASE_CODE_UDP_WRITE       UdpWrite;
      EFI_PXE_BASE_CODE_UDP_READ        UdpRead;
      EFI_PXE_BASE_CODE_SET_IP_FILTER   SetIpFilter;
      EFI_PXE_BASE_CODE_ARP             Arp;
      EFI_PXE_BASE_CODE_SET_PARAMETERS  SetParameters;
      EFI_PXE_BASE_CODE_SET_STATION_IP  SetStationIp;
      EFI_PXE_BASE_CODE_SET_PACKETS     SetPackets;
      ///
      /// The pointer to the EFI_PXE_BASE_CODE_MODE data for this device.
      ///
      EFI_PXE_BASE_CODE_MODE            *Mode;
    };

它实际上需要完成网络通信相关的动作，比如DHCP/TFPT等。PxeBc的实现如下（NetworkPkg\\UefiPxeBcDxe\\PxeBcImpl.c）:

EFI_PXE_BASE_CODE_PROTOCOL  gPxeBcProtocolTemplate = {
      EFI_PXE_BASE_CODE_PROTOCOL_REVISION,
      EfiPxeBcStart,
      EfiPxeBcStop,
      EfiPxeBcDhcp,
      EfiPxeBcDiscover,
      EfiPxeBcMtftp,
      EfiPxeBcUdpWrite,
      EfiPxeBcUdpRead,
      EfiPxeBcSetIpFilter,
      EfiPxeBcArp,
      EfiPxeBcSetParameters,
      EfiPxeBcSetStationIP,
      EfiPxeBcSetPackets,
      NULL
    };

而PxeBc和LoadFile之间的关系是通过如下的结构体连接在一起的（NetworkPkg\\UefiPxeBcDxe\\PxeBcImpl.h）：

struct _PXEBC_VIRTUAL_NIC {
      UINT32                                    Signature;
      EFI_HANDLE                                Controller;
      EFI_LOAD_FILE_PROTOCOL                    LoadFile;
      EFI_DEVICE_PATH_PROTOCOL                  *DevicePath;
      PXEBC_PRIVATE_DATA                        *Private;
    };

## HTTP启动 ##

HTTP虽然本身也不是什么新东西，但是用作网络启动还是比PXE要新。相比PXE使用TFTP下载BootLoader，HTTP启动当然就是使用HTTP来下载Boot Loader。两者虽没有本质的区别，但是HTTP具有更广泛的适用性。下面是HTTP启动的环境框图：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppYW5nd2VpMDUxMg_size_16_color_FFFFFF_t_70][]

BootLoader位于HTTP服务器上，而不是PXE启动的TFTP服务器上。且HTTP使用URI来访问服务器设备，而PXE使用IP来访问服务器设备。

HTTP启动的实现相比PXE启动要稍微复杂些，涉及到DNS/DHCP/URL的等内容。不过关键还是NetworkPkg\\HttpBootDxe\\HttpBootDxe.inf模块，它实现了EFI\_LOAD\_FILE\_PROTOCOL（NetworkPkg\\HttpBootDxe\\HttpBootDxe.c）：

//
      // Create a child handle for the HTTP boot and install DevPath and Load file protocol on it.
      //
      CopyMem (&Private->Ip4Nic->LoadFile, &gHttpBootDxeLoadFile, sizeof (EFI_LOAD_FILE_PROTOCOL));
      Status = gBS->InstallMultipleProtocolInterfaces (
                      &Private->Ip4Nic->Controller,
                      &gEfiLoadFileProtocolGuid,
                      &Private->Ip4Nic->LoadFile,
                      &gEfiDevicePathProtocolGuid,
                      Private->Ip4Nic->DevicePath,
                      NULL
                      );
      if (EFI_ERROR (Status)) {
        goto ON_ERROR;
      }

它也分为IPv4和IPv6两种类型。对应的LoadFile实现（NetworkPkg\\HttpBootDxe\\HttpBootImpl.c）：

///
    /// Load File Protocol instance
    ///
    GLOBAL_REMOVE_IF_UNREFERENCED 
    EFI_LOAD_FILE_PROTOCOL  gHttpBootDxeLoadFile = {
      HttpBootDxeLoadFile
    };

另外还有一些Protocol用来处理HTTP通信的内容，比如：

///
    /// EFI_HTTP_UTILITIES_PROTOCOL
    /// designed to be used by EFI drivers and applications to parse HTTP
    /// headers from a byte stream. This driver is neither dependent on
    /// network connectivity, nor the existence of an underlying network
    /// infrastructure.
    ///
    struct _EFI_HTTP_UTILITIES_PROTOCOL {
      EFI_HTTP_UTILS_BUILD          Build;
      EFI_HTTP_UTILS_PARSE          Parse;
    };
    ///
    /// The EFI_DNS4_Protocol provides the function to get the host name and address
    /// mapping, also provides pass through interface to retrieve arbitrary information
    /// from DNS.
    ///
    struct _EFI_DNS4_PROTOCOL {
      EFI_DNS4_GET_MODE_DATA        GetModeData;
      EFI_DNS4_CONFIGURE            Configure;
      EFI_DNS4_HOST_NAME_TO_IP      HostNameToIp;
      EFI_DNS4_IP_TO_HOST_NAME      IpToHostName;
      EFI_DNS4_GENERAL_LOOKUP       GeneralLookUp;
      EFI_DNS4_UPDATE_DNS_CACHE     UpdateDnsCache;
      EFI_DNS4_POLL                 Poll;
      EFI_DNS4_CANCEL               Cancel;
    };

关于HTTP启动，还可以参考：[https://github.com/tianocore/tianocore.github.io/wiki/HTTP-Boot][https_github.com_tianocore_tianocore.github.io_wiki_HTTP-Boot]。

## 网路启动项 ##

简单介绍完HTTP启动和PXE启动，后续需要关注的是如何使用这些启动实现。其实前面已经介绍过，这主要通过EFI\_LOAD\_FILE\_PROTOCOL 来完成。对于网路启动，大致的代码如下：

Status = gBS->LocateHandleBuffer (ByProtocol, &gEfiLoadFileProtocolGuid, NULL, &HandleCount, &Handles);
      if (EFI_ERROR (Status)) {
        HandleCount = 0;
        Handles = NULL;
      }
      NextFullPath = NULL;
      GetNext = (BOOLEAN)(FullPath == NULL);
      for (Index = 0; Index < HandleCount; Index++) {
        NextFullPath = BmExpandLoadFile (Handles[Index], FilePath);

这里获取到所有实现了的EFI\_LOAD\_FILE\_PROTOCOL ，针对每一个Protocol，调用其LoadFile来获取文件。但是需要注意，因为HTTP启动和PXE启动使用的地址是不同的，所以对应到Device Path也是不同的：

/**
      Causes the driver to load a specified file.
      @param  This       Protocol instance pointer.
      @param  FilePath   The device specific path of the file to load.
      @param  BootPolicy If TRUE, indicates that the request originates from the
                         boot manager is attempting to load FilePath as a boot
                         selection. If FALSE, then FilePath must match as exact file
                         to be loaded.
      @param  BufferSize On input the size of Buffer in bytes. On output with a return
                         code of EFI_SUCCESS, the amount of data transferred to
                         Buffer. On output with a return code of EFI_BUFFER_TOO_SMALL,
                         the size of Buffer required to retrieve the requested file.
      @param  Buffer     The memory buffer to transfer the file to. IF Buffer is NULL,
                         then the size of the requested file is returned in
                         BufferSize.
    
      @retval EFI_SUCCESS           The file was loaded.
      @retval EFI_UNSUPPORTED       The device does not support the provided BootPolicy
      @retval EFI_INVALID_PARAMETER FilePath is not a valid device path, or
                                    BufferSize is NULL.
      @retval EFI_NO_MEDIA          No medium was present to load the file.
      @retval EFI_DEVICE_ERROR      The file was not loaded due to a device error.
      @retval EFI_NO_RESPONSE       The remote system did not respond.
      @retval EFI_NOT_FOUND         The file was not found.
      @retval EFI_ABORTED           The file load process was manually cancelled.
      @retval EFI_WARN_FILE_SYSTEM  The resulting Buffer contains UEFI-compliant file system.
    **/
    
    typedef
    EFI_STATUS
    (EFIAPI *EFI_LOAD_FILE)(
      IN EFI_LOAD_FILE_PROTOCOL           *This,
      IN EFI_DEVICE_PATH_PROTOCOL         *FilePath,
      IN BOOLEAN                          BootPolicy,
      IN OUT UINTN                        *BufferSize,
      IN VOID                             *Buffer OPTIONAL
      );

即这里的FilePath有不同的取值。HTTP对应的Device Path结构体：

///
    /// Uniform Resource Identifiers (URI) Device Path SubType
    ///
    #define MSG_URI_DP                0x18
    typedef struct {
      EFI_DEVICE_PATH_PROTOCOL        Header;
      ///
      /// Instance of the URI pursuant to RFC 3986.
      ///
      CHAR8                           Uri[];
    } URI_DEVICE_PATH;

在HttpBootDxeLoadFile实现中会需要使用到Device Path：

EFI_STATUS
    EFIAPI
    HttpBootDxeLoadFile (
      IN EFI_LOAD_FILE_PROTOCOL           *This,
      IN EFI_DEVICE_PATH_PROTOCOL         *FilePath,
      IN BOOLEAN                          BootPolicy,
      IN OUT UINTN                        *BufferSize,
      IN VOID                             *Buffer OPTIONAL
      )
    {
    
      HTTP_BOOT_PRIVATE_DATA        *Private;
      HTTP_BOOT_VIRTUAL_NIC         *VirtualNic;
      BOOLEAN                       MediaPresent;
      BOOLEAN                       UsingIpv6;
      EFI_STATUS                    Status;
      HTTP_BOOT_IMAGE_TYPE          ImageType;
    
      if (This == NULL || BufferSize == NULL || FilePath == NULL) {
        return EFI_INVALID_PARAMETER;
      }
    
      //
      // Only support BootPolicy
      //
      if (!BootPolicy) {
        return EFI_UNSUPPORTED;
      }
    
      VirtualNic = HTTP_BOOT_VIRTUAL_NIC_FROM_LOADFILE (This);
      Private = VirtualNic->Private;
     
      //
      // Check media status before HTTP boot start
      //
      MediaPresent = TRUE;
      NetLibDetectMedia (Private->Controller, &MediaPresent);
      if (!MediaPresent) {
        return EFI_NO_MEDIA;
      }
      
    
      //
      // Check whether the virtual nic is using IPv6 or not.
      //
      UsingIpv6 = FALSE;
      if (VirtualNic == Private->Ip6Nic) {
        UsingIpv6 = TRUE;
      }
    
      //
      // Initialize HTTP boot.
      //
      Status = HttpBootStart (Private, UsingIpv6, FilePath);
      if (Status != EFI_SUCCESS && Status != EFI_ALREADY_STARTED) {
        return Status;
      }

而PXE启动并不需要特别的Device Path：

EFI_STATUS
    EFIAPI
    EfiPxeLoadFile (
      IN     EFI_LOAD_FILE_PROTOCOL           *This,
      IN     EFI_DEVICE_PATH_PROTOCOL         *FilePath,
      IN     BOOLEAN                          BootPolicy,
      IN OUT UINTN                            *BufferSize,
      IN     VOID                             *Buffer       OPTIONAL
      )
    {
      PXEBC_PRIVATE_DATA          *Private;
      PXEBC_VIRTUAL_NIC           *VirtualNic;
      EFI_PXE_BASE_CODE_PROTOCOL  *PxeBc;
      BOOLEAN                     UsingIpv6;
      EFI_STATUS                  Status;
      BOOLEAN                     MediaPresent;
    
      if (FilePath == NULL || !IsDevicePathEnd (FilePath)) {
        return EFI_INVALID_PARAMETER;
      }

这里只做了判断，但是没有真正使用。除了Device Path，两者调用LoadFile没有大的差别。

[PXE]: https://blog.csdn.net/jiangwei0512/article/details/99993949?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522159214413719195239855909%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=159214413719195239855909&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~baidu_landing_v2~default-5-99993949.pc_search_back_js3&utm_term=PXE
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppYW5nd2VpMDUxMg_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200614233148771.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ppYW5nd2VpMDUxMg==,size_16,color_FFFFFF,t_70
[https_github.com_tianocore_tianocore.github.io_wiki_HTTP-Boot]: https://github.com/tianocore/tianocore.github.io/wiki/HTTP-Boot