标签： Console

标题看起来非常拗口，具体来说描述起来就是下面的问题：

“我想写一个简单的程序，先把某个app的Load进内存，然后在内存里爆搜一个特征字串，搜到之后将该内存第一个字节替换。以下为代码片段，碰到一个问题就是，我搜到特征字串之后，修改其内存的内容一直改不了，请问各位大大，是不是UEFI有相应的保护策略，不能修改LoadImage的内存？我个人觉得是不应该，因为我是LoadImage的宿主，我Load的内存应该是可以被我修改的。请大牛们指教啊！！！

Status=gBS->LoadImage(TRUE, ImageHandle, DstDevicePath, NULL, 0, &DstImageHandle); //LoadImage
if (!EFI_ERROR(Status))
{
Print(L”Load Image success\n”);
}
Status=gBS->HandleProtocol(DstImageHandle, &gEfiLoadedImageProtocolGuid,(void **) &LoadedImage);
if (EFI_ERROR(Status)) {
Print(L”Can not retrieve a LoadedImageProtocol handle for ImageHandle\n”);
gBS->Exit(ImageHandle,EFI_SUCCESS,0,NULL);
}
//Get the loaded image base address
imageBase=LoadedImage->ImageBase;
size=LoadedImage->ImageSize;

temp=(char *)imageBase;

//Search the sig;, replace the first byte
for (; temp<(char *)imageBase+size; temp++) { if (*temp==0x55 && *(temp+1)==0x00 && *(temp+2)==0x45 && *(temp+3)==0x00) { Print(L"Find sig\n"); *temp=0x45; Print(L"addr %x\n",temp); break; } } 上述问题来自【参考1】 这个一个有趣的问题，也不知道那个朋友最后是否成功。根据上面的问题，我做一下实验。 首先，准备一个被修改的 App。当然，根据之前的知识，这个 App 不能使用 CLIB 库，目前为止我还是不知道为什么无法加载调用这个库的 Application.

#include <Uefi.h>
#include <Library/PcdLib.h>
#include <Library/UefiLib.h>
#include <Library/UefiApplicationEntryPoint.h>


/**
  The user Entry Point for Application. The user code starts with this function
  as the real entry point for the application.

  @param[in] ImageHandle    The firmware allocated handle for the EFI image.  
  @param[in] SystemTable    A pointer to the EFI System Table.
  
  @retval EFI_SUCCESS       The entry point is executed successfully.
  @retval other             Some error occurs when executing this entry point.

**/
EFI_STATUS
EFIAPI
UefiMain (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
                                       
  CHAR8  *s1= "This code comes from www.lab-z.com";
  CHAR16 *s2=L"                                  ";
  CHAR16 *Result;
  
  Result=AsciiStrToUnicodeStr(s1,s2);
  Print(L"%s\n",s2);

  return EFI_SUCCESS;
}

 

代码非常简单，将一个 ASCII 字符串转化为 Unicode 的，然后显示出来。使用 ASCII 的原因是为了便于查找。

上面的程序编译之后，使用十六进制工具打开可以直接查看到 ASCII 字符。

然后，继续编写加载和修改的程序如下：

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>

#include  <stdio.h>
#include  <stdlib.h>
#include  <wchar.h>

#include <Protocol/EfiShell.h>
#include <Library/ShellLib.h>

extern EFI_BOOT_SERVICES           	 *gBS;
extern EFI_SYSTEM_TABLE				 *gST;
extern EFI_RUNTIME_SERVICES 		 *gRT;

extern EFI_SHELL_PROTOCOL            *gEfiShellProtocol;
extern EFI_SHELL_ENVIRONMENT2 		 *mEfiShellEnvironment2;

extern EFI_HANDLE					 gImageHandle;
/**
  GET  DEVICEPATH
**/
EFI_DEVICE_PATH_PROTOCOL *
EFIAPI
ShellGetDevicePath (
  IN CHAR16                     * CONST DeviceName OPTIONAL
  )
{
  //
  // Check for UEFI Shell 2.0 protocols
  //
  if (gEfiShellProtocol != NULL) {
    return (gEfiShellProtocol->GetDevicePathFromFilePath(DeviceName));
  }

  //
  // Check for EFI shell
  //
  if (mEfiShellEnvironment2 != NULL) {
    return (mEfiShellEnvironment2->NameToPath(DeviceName));
  }

  return (NULL);
}

int
EFIAPI
main (
  IN int Argc,
  IN char **Argv
  )
{
  EFI_DEVICE_PATH_PROTOCOL 	*DevicePath;
  EFI_HANDLE				NewHandle;
  EFI_STATUS				Status;
  UINTN			ExitDataSizePtr;  
  CHAR16 					*R=L"HelloWorld.efi";
  EFI_LOADED_IMAGE_PROTOCOL	*ImageInfo = NULL;
  CHAR8						*temp;
  
  Print(L"File [%s]\n",R);

  DevicePath=ShellGetDevicePath(R);

  //
  // Load the image with:
  // FALSE - not from boot manager and NULL, 0 being not already in memory
  //
  Status = gBS->LoadImage(
    FALSE,
    gImageHandle,
    DevicePath,
    NULL,
    0,
    &NewHandle);  

  if (EFI_ERROR(Status)) {
    if (NewHandle != NULL) {
      gBS->UnloadImage(NewHandle);
    }
	Print(L"Error during LoadImage [%X]\n",Status);
    return (Status);
  }

  Status = gBS -> HandleProtocol (
						NewHandle,
						&gEfiLoadedImageProtocolGuid,
						&ImageInfo
						);
  Print(L"ImageBase [%lX]\n",ImageInfo->ImageBase);
  Print(L"ImageSize [%lX]\n",ImageInfo->ImageSize);

  temp=(char *)ImageInfo->ImageBase;
  //Search the sig;, replace the first byte
  for (; temp<(char *)ImageInfo->ImageBase+ImageInfo->ImageSize; temp++)
        {
				//"lab" 6C 61 62
                if (*temp==0x6C && *(temp+1)==0x61 && *(temp+2)==0x62)
                {
                        Print(L"Find sig\n");
                        Print(L"addr %x\n",temp);
						*(temp  )=0x2D;
						*(temp+1)=0x2D;
						*(temp+2)=0x2D;
                        break;
                } 
        }  
  
  
  //
  // now start the image, passing up exit data if the caller requested it
  //
  Status = gBS->StartImage(
                     NewHandle,
                     &ExitDataSizePtr,
                     NULL
              );
  if (EFI_ERROR(Status)) {
    if (NewHandle != NULL) {
      gBS->UnloadImage(NewHandle);
    }
	Print(L"Error during StartImage [%X]\n",Status);
    return (Status);
  }
  
  gBS->UnloadImage (NewHandle);  
  return EFI_SUCCESS;
}

 

加载部分的代码使用的是 【参考2】的框架，搜索部分的代码用的是前面问题中给出来的示例。我们在加载后的 Application 的空间中搜索 “lab” 字符串并且替换为 “—”。

运行结果如下，我们先执行了一次 HelloWorld.efi，可以看到他能正常打印字符串，之后再用我们的程序加载一次，可以看到字符串被修改掉了。

看起来并没有什么保护之类的，轻而易举的改掉了 Application 的内容。猜测之前提出问题的朋友有可能是被加载的代码用到了 CLIB， 或者是代码中的字符串是按照 UNICODE 给出来的，所以无法找到。

这样的动态加载可以用在一些特殊的地方，比如，我见过一款 DOS 下的测试软件，有一个主程序 EXE 和 n多个独立的 EXE 构成。主程序可以调用其他的 EXE 进行测试，但是单独的 EXE 无法执行，这样的好处是开发时可以独立开发单独模块，分发之后有主程序进行控制只在需要的环境中运行。

本文提到的代码下载

exec3

HelloWorld

参考：

1. http://biosren.com/thread-4564-1-31.html
2. http://www.lab-z.com/efiloadedimageprotocol/ Step to UEFI (46） —– EFILOADEDIMAGEPROTOCOL的使用

前面介绍过使用 ShellReadFile 读取文件的内容，这里介绍一下 ShellWriteFile 的使用。

例子是使用 ShellOpenFileByName 打开当前的 EFI Application,把内容读取到内存之后，创建一个名为 Test.efi 的文件，使用 ShellWriteFile 函数把内容写进去。

代码如下：

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>
#include  <Library/ShellLib.h>
#include  <Library/MemoryAllocationLib.h>

extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{

  EFI_FILE_HANDLE   FileHandle;
  RETURN_STATUS     Status;
  EFI_FILE_INFO     *FileInfo = NULL;
  EFI_HANDLE        *HandleBuffer=NULL;
  UINTN  			ReadSize;
  
  //Open the file given by the parameter
  Status = ShellOpenFileByName(Argv[0], 
		(SHELL_FILE_HANDLE *)&
                FileHandle,
                EFI_FILE_MODE_READ , 0);

  if(Status != RETURN_SUCCESS) {
        Print(L"OpenFile failed!\n");
		return EFI_SUCCESS;
      }			

  //Get file size	  
  FileInfo = ShellGetFileInfo( (SHELL_FILE_HANDLE)FileHandle);	

  //Allocate a memory buffer
  HandleBuffer = AllocateZeroPool((UINTN) FileInfo-> FileSize);
  if (HandleBuffer == NULL) {
      return (SHELL_OUT_OF_RESOURCES);   }

  ReadSize=(UINTN) FileInfo-> FileSize;
  
  //Load the whole file to the buffer
  Status = ShellReadFile(FileHandle,&ReadSize,HandleBuffer);
  
  //Close the source file
  ShellCloseFile(&FileHandle);

  //Create a new file
  Status = ShellOpenFileByName(L"Test.efi", 
             (SHELL_FILE_HANDLE *)&FileHandle,
                               EFI_FILE_MODE_READ |
			       EFI_FILE_MODE_WRITE|
			       EFI_FILE_MODE_CREATE, 
			    0);  
  if(Status != RETURN_SUCCESS) {
        Print(L"CreatFile failed [%r]!\n",Status);
	    return EFI_SUCCESS;
      }	
  Status = ShellWriteFile(FileHandle,
			&ReadSize,
			HandleBuffer
			);
  //Close the source file
  ShellCloseFile(&FileHandle);
  
  return EFI_SUCCESS;
}

 

运行结果（运行结束之后我比较了一下生成文件和源文件是相同的）：

特别注意：使用 ShellOpenFuleByName 创建一个文件时，要同时使用 EFI_FILE_MODE_READ ,EFI_FILE_MODE_WRITE 和 EFI_FILE_MODE_CREATE ，否则可能出现“Invalid Parameter”的错误【参考1】

完整代码下载
CreateFile

1.http://feishare.com/efimail/messages/20120331-0611-Re__edk2__Problems_creating_file_using_ShellOpenFileByName-_Bekefi__Stephen_C_.html

最近发现一个挺有意思的功能，Print 使用 %r 参数可以直接输出错误信息的含义。这样的话，我们可以直接取得错误信息，省去不少麻烦。例如，下面的代码

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>


extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  Print(L"%r\n",EFI_SUCCESS);
  Print(L"%r\n",RETURN_WARN_WRITE_FAILURE);
  Print(L"%r\n",RETURN_COMPROMISED_DATA);
  
  return EFI_SUCCESS;
}

 

运行结果

我们再仔细研究一下 %r 的具体实现。

查看 PrintR 编译生成的 printf.map ,可以看到 _Print 是链接到 UefiLibPrint.obj 中。用这个文件名，我们确定是在 \MdePkg\Library\UefiLib\UefiLibPrint.c 这个文件中

0001:000000ce _ShellCEntryLib 0000032e f UefiShellCEntryLib:UefiShellCEntryLib.obj
0001:00000140 _InternalPrint 000003a0 f UefiLib:UefiLibPrint.obj
0001:0000018b _Print 000003eb f UefiLib:UefiLibPrint.obj
0001:000001a8 _ShellFindSE2 00000408 f UefiShellLib:UefiShellLib.obj
0001:000002d8 _ShellLibConstructorWorker 00000538 f UefiShellLib:UefiShellLib.obj
0001:0000048d _ShellLibDestructor 000006ed f UefiShellLib:UefiShellLib.obj
0001:00000535 _ShellOpenFileByDevicePath 00000795 f UefiShellLib:UefiShellLib.obj

Print 函数：

/** 
  Prints a formatted Unicode string to the console output device specified by 
  ConOut defined in the EFI_SYSTEM_TABLE.

  This function prints a formatted Unicode string to the console output device 
  specified by ConOut in EFI_SYSTEM_TABLE and returns the number of Unicode 
  characters that printed to ConOut.  If the length of the formatted Unicode 
  string is greater than PcdUefiLibMaxPrintBufferSize, then only the first 
  PcdUefiLibMaxPrintBufferSize characters are sent to ConOut.
  If Format is NULL, then ASSERT().
  If Format is not aligned on a 16-bit boundary, then ASSERT().
  If gST->ConOut is NULL, then ASSERT().

  @param Format   A Null-terminated Unicode format string.
  @param ...      A Variable argument list whose contents are accessed based 
                  on the format string specified by Format.
  
  @return The number of Unicode characters printed to ConOut.

**/
UINTN
EFIAPI
Print (
  IN CONST CHAR16  *Format,
  ...
  )
{
  VA_LIST Marker;
  UINTN   Return;

  VA_START (Marker, Format);

  Return = InternalPrint (Format, gST->ConOut, Marker);

  VA_END (Marker);

  return Return;
}

 

InternalPrint 函数在同一个文件中

/**
  Internal function which prints a formatted Unicode string to the console output device
  specified by Console

  This function prints a formatted Unicode string to the console output device
  specified by Console and returns the number of Unicode characters that printed
  to it.  If the length of the formatted Unicode string is greater than PcdUefiLibMaxPrintBufferSize,
  then only the first PcdUefiLibMaxPrintBufferSize characters are sent to Console.
  If Format is NULL, then ASSERT().
  If Format is not aligned on a 16-bit boundary, then ASSERT().

  @param Format   A Null-terminated Unicode format string.
  @param Console  The output console.
  @param Marker   A VA_LIST marker for the variable argument list.

  @return The number of Unicode characters in the produced
          output buffer, not including the Null-terminator.
**/
UINTN
InternalPrint (
  IN  CONST CHAR16                     *Format,
  IN  EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL  *Console,
  IN  VA_LIST                          Marker
  )
{
  EFI_STATUS  Status;
  UINTN       Return;
  CHAR16      *Buffer;
  UINTN       BufferSize;

  ASSERT (Format != NULL);
  ASSERT (((UINTN) Format & BIT0) == 0);
  ASSERT (Console != NULL);

  BufferSize = (PcdGet32 (PcdUefiLibMaxPrintBufferSize) + 1) * sizeof (CHAR16);

  Buffer = (CHAR16 *) AllocatePool(BufferSize);
  ASSERT (Buffer != NULL);

  Return = UnicodeVSPrint (Buffer, BufferSize, Format, Marker);

  if (Console != NULL && Return > 0) {
    //
    // To be extra safe make sure Console has been initialized
    //
    Status = Console->OutputString (Console, Buffer);
    if (EFI_ERROR (Status)) {
      Return = 0;
    }
  }

  FreePool (Buffer);

  return Return;
}

 

处理输出的核心是 UnicodeVSPrint 函数

/**
  Produces a Null-terminated Unicode string in an output buffer based on 
  a Null-terminated Unicode format string and a VA_LIST argument list
  
  Produces a Null-terminated Unicode string in the output buffer specified by StartOfBuffer
  and BufferSize.  
  The Unicode string is produced by parsing the format string specified by FormatString.  
  Arguments are pulled from the variable argument list specified by Marker based on the 
  contents of the format string.  
  The number of Unicode characters in the produced output buffer is returned not including
  the Null-terminator.
  If BufferSize is 0 or 1, then no output buffer is produced and 0 is returned.

  If BufferSize > 1 and StartOfBuffer is NULL, then ASSERT().
  If BufferSize > 1 and StartOfBuffer is not aligned on a 16-bit boundary, then ASSERT().
  If BufferSize > 1 and FormatString is NULL, then ASSERT().
  If BufferSize > 1 and FormatString is not aligned on a 16-bit boundary, then ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and FormatString contains more than 
  PcdMaximumUnicodeStringLength Unicode characters not including the Null-terminator, then
  ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and produced Null-terminated Unicode string
  contains more than PcdMaximumUnicodeStringLength Unicode characters not including the
  Null-terminator, then ASSERT().

  @param  StartOfBuffer   A pointer to the output buffer for the produced Null-terminated 
                          Unicode string.
  @param  BufferSize      The size, in bytes, of the output buffer specified by StartOfBuffer.
  @param  FormatString    A Null-terminated Unicode format string.
  @param  Marker          VA_LIST marker for the variable argument list.
  
  @return The number of Unicode characters in the produced output buffer not including the
          Null-terminator.

**/
UINTN
EFIAPI
UnicodeVSPrint (
  OUT CHAR16        *StartOfBuffer,
  IN  UINTN         BufferSize,
  IN  CONST CHAR16  *FormatString,
  IN  VA_LIST       Marker
  )
{
  ASSERT_UNICODE_BUFFER (StartOfBuffer);
  ASSERT_UNICODE_BUFFER (FormatString);
  return BasePrintLibSPrintMarker ((CHAR8 *)StartOfBuffer, BufferSize >> 1, FORMAT_UNICODE | OUTPUT_UNICODE, (CHAR8 *)FormatString, Marker, NULL);
}

 

BasePrintLibSPrintMarker 函数在 \MdePkg\Library\BasePrintLib\PrintLib.c

/**
  Worker function that produces a Null-terminated string in an output buffer 
  based on a Null-terminated format string and a VA_LIST argument list.

  VSPrint function to process format and place the results in Buffer. Since a 
  VA_LIST is used this routine allows the nesting of Vararg routines. Thus 
  this is the main print working routine.

  If COUNT_ONLY_NO_PRINT is set in Flags, Buffer will not be modified at all.

  @param[out] Buffer          The character buffer to print the results of the 
                              parsing of Format into.
  @param[in]  BufferSize      The maximum number of characters to put into 
                              buffer.
  @param[in]  Flags           Initial flags value.
                              Can only have FORMAT_UNICODE, OUTPUT_UNICODE, 
                              and COUNT_ONLY_NO_PRINT set.
  @param[in]  Format          A Null-terminated format string.
  @param[in]  VaListMarker    VA_LIST style variable argument list consumed by
                              processing Format.
  @param[in]  BaseListMarker  BASE_LIST style variable argument list consumed
                              by processing Format.

  @return The number of characters printed not including the Null-terminator.
          If COUNT_ONLY_NO_PRINT was set returns the same, but without any
          modification to Buffer.

**/
UINTN
BasePrintLibSPrintMarker (
  OUT CHAR8        *Buffer,
  IN  UINTN        BufferSize,
  IN  UINTN        Flags,
  IN  CONST CHAR8  *Format,
  IN  VA_LIST      VaListMarker,   OPTIONAL
  IN  BASE_LIST    BaseListMarker  OPTIONAL
  )

 

处理 %r 的代码如下

      case 'r':
        if (BaseListMarker == NULL) {
          Status = VA_ARG (VaListMarker, RETURN_STATUS);
        } else {
          Status = BASE_ARG (BaseListMarker, RETURN_STATUS);
        }
        ArgumentString = ValueBuffer;
        if (RETURN_ERROR (Status)) {
          //
          // Clear error bit
          //
          Index = Status & ~MAX_BIT;
          if (Index > 0 && Index <= ERROR_STATUS_NUMBER) {
            ArgumentString = mStatusString [Index + WARNING_STATUS_NUMBER];
          }
        } else {
          Index = Status;
          if (Index <= WARNING_STATUS_NUMBER) {
            ArgumentString = mStatusString [Index];
          }
        }
        if (ArgumentString == ValueBuffer) {
          BasePrintLibSPrint ((CHAR8 *) ValueBuffer, MAXIMUM_VALUE_CHARACTERS, 0, "%08X", Status);
        }
        break;

 

核心就是查 mStatusString 表，在 \MdePkg\Library\BasePrintLib\PrintLibInternal.c 中有定义

GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 *mStatusString[] = {
  "Success",                      //  RETURN_SUCCESS                = 0
  "Warning Unknown Glyph",        //  RETURN_WARN_UNKNOWN_GLYPH     = 1
  "Warning Delete Failure",       //  RETURN_WARN_DELETE_FAILURE    = 2
  "Warning Write Failure",        //  RETURN_WARN_WRITE_FAILURE     = 3
  "Warning Buffer Too Small",     //  RETURN_WARN_BUFFER_TOO_SMALL  = 4
  "Warning Stale Data",           //  RETURN_WARN_STALE_DATA        = 5
  "Load Error",                   //  RETURN_LOAD_ERROR             = 1  | MAX_BIT
  "Invalid Parameter",            //  RETURN_INVALID_PARAMETER      = 2  | MAX_BIT
  "Unsupported",                  //  RETURN_UNSUPPORTED            = 3  | MAX_BIT
  "Bad Buffer Size",              //  RETURN_BAD_BUFFER_SIZE        = 4  | MAX_BIT
  "Buffer Too Small",             //  RETURN_BUFFER_TOO_SMALL,      = 5  | MAX_BIT
  "Not Ready",                    //  RETURN_NOT_READY              = 6  | MAX_BIT
  "Device Error",                 //  RETURN_DEVICE_ERROR           = 7  | MAX_BIT
  "Write Protected",              //  RETURN_WRITE_PROTECTED        = 8  | MAX_BIT
  "Out of Resources",             //  RETURN_OUT_OF_RESOURCES       = 9  | MAX_BIT
  "Volume Corrupt",               //  RETURN_VOLUME_CORRUPTED       = 10 | MAX_BIT
  "Volume Full",                  //  RETURN_VOLUME_FULL            = 11 | MAX_BIT
  "No Media",                     //  RETURN_NO_MEDIA               = 12 | MAX_BIT
  "Media changed",                //  RETURN_MEDIA_CHANGED          = 13 | MAX_BIT
  "Not Found",                    //  RETURN_NOT_FOUND              = 14 | MAX_BIT
  "Access Denied",                //  RETURN_ACCESS_DENIED          = 15 | MAX_BIT
  "No Response",                  //  RETURN_NO_RESPONSE            = 16 | MAX_BIT
  "No mapping",                   //  RETURN_NO_MAPPING             = 17 | MAX_BIT
  "Time out",                     //  RETURN_TIMEOUT                = 18 | MAX_BIT
  "Not started",                  //  RETURN_NOT_STARTED            = 19 | MAX_BIT
  "Already started",              //  RETURN_ALREADY_STARTED        = 20 | MAX_BIT
  "Aborted",                      //  RETURN_ABORTED                = 21 | MAX_BIT
  "ICMP Error",                   //  RETURN_ICMP_ERROR             = 22 | MAX_BIT
  "TFTP Error",                   //  RETURN_TFTP_ERROR             = 23 | MAX_BIT
  "Protocol Error",               //  RETURN_PROTOCOL_ERROR         = 24 | MAX_BIT
  "Incompatible Version",         //  RETURN_INCOMPATIBLE_VERSION   = 25 | MAX_BIT
  "Security Violation",           //  RETURN_SECURITY_VIOLATION     = 26 | MAX_BIT
  "CRC Error",                    //  RETURN_CRC_ERROR              = 27 | MAX_BIT
  "End of Media",                 //  RETURN_END_OF_MEDIA           = 28 | MAX_BIT
  "Reserved (29)",                //  RESERVED                      = 29 | MAX_BIT
  "Reserved (30)",                //  RESERVED                      = 30 | MAX_BIT
  "End of File",                  //  RETURN_END_OF_FILE            = 31 | MAX_BIT
  "Invalid Language",             //  RETURN_INVALID_LANGUAGE       = 32 | MAX_BIT
  "Compromised Data"              //  RETURN_COMPROMISED_DATA       = 33 | MAX_BIT
};

 

具体的实现就是这样。

继续介绍 EFI 下面的常用字符串函数

\MdePkg\Include\Library\BaseLib.h

1.StrStr 函数作用：在字符串中查找另外的字符串

/**
  Returns the first occurrence of a Null-terminated Unicode sub-string
  in a Null-terminated Unicode string.

  This function scans the contents of the Null-terminated Unicode string
  specified by String and returns the first occurrence of SearchString.
  If SearchString is not found in String, then NULL is returned.  If
  the length of SearchString is zero, then String is returned.

  If String is NULL, then ASSERT().
  If String is not aligned on a 16-bit boundary, then ASSERT().
  If SearchString is NULL, then ASSERT().
  If SearchString is not aligned on a 16-bit boundary, then ASSERT().

  If PcdMaximumUnicodeStringLength is not zero, and SearchString
  or String contains more than PcdMaximumUnicodeStringLength Unicode
  characters, not including the Null-terminator, then ASSERT().

  @param  String          The pointer to a Null-terminated Unicode string.
  @param  SearchString    The pointer to a Null-terminated Unicode string to search for.

  @retval NULL            If the SearchString does not appear in String.
  @return others          If there is a match.

**/
CHAR16 *
EFIAPI
StrStr (
  IN      CONST CHAR16              *String,
  IN      CONST CHAR16              *SearchString
  );

 

实例：

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>


extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  CHAR16 *s1=L"WWW.";
  CHAR16 *s2=L"COM";  
  CHAR16 *s3=L"com";    
  CHAR16 s4[40]=L"LAB-Z.COM";
  CHAR16 *Result;
  
  Result=StrStr(s4,s1);
  Print(L"%s\n",Result);

  Result=StrStr(s4,s2);
  Print(L"%s\n",Result);

  Result=StrStr(s4,s3);
  Print(L"%s\n",Result);

  return EFI_SUCCESS;
}

 

运行结果

2.StrDecimalToUintn 作用：把字符串转换为数字

/**
  Convert a Null-terminated Unicode decimal string to a value of
  type UINTN.

  This function returns a value of type UINTN by interpreting the contents
  of the Unicode string specified by String as a decimal number. The format
  of the input Unicode string String is:

                  [spaces] [decimal digits].

  The valid decimal digit character is in the range [0-9]. The
  function will ignore the pad space, which includes spaces or
  tab characters, before [decimal digits]. The running zero in the
  beginning of [decimal digits] will be ignored. Then, the function
  stops at the first character that is a not a valid decimal character
  or a Null-terminator, whichever one comes first.

  If String is NULL, then ASSERT().
  If String is not aligned in a 16-bit boundary, then ASSERT().
  If String has only pad spaces, then 0 is returned.
  If String has no pad spaces or valid decimal digits,
  then 0 is returned.
  If the number represented by String overflows according
  to the range defined by UINTN, then ASSERT().

  If PcdMaximumUnicodeStringLength is not zero, and String contains
  more than PcdMaximumUnicodeStringLength Unicode characters not including
  the Null-terminator, then ASSERT().

  @param  String      The pointer to a Null-terminated Unicode string.

  @retval Value translated from String.

**/
UINTN
EFIAPI
StrDecimalToUintn (
  IN      CONST CHAR16              *String
  );

 

实例代码：

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>


extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  CHAR16 *s1=L"100";
  CHAR16 *s2=L"77F";  
  CHAR16 *s3=L"77f";    
  CHAR16 *s4=L"77z";      
  UINTN Result;
  
  Result=StrDecimalToUintn(s1);
  Print(L"%d\n",Result);

  Result=StrDecimalToUintn(s2);
  Print(L"%d\n",Result);

  Result=StrDecimalToUintn(s3);
  Print(L"%d\n",Result);

  Result=StrDecimalToUintn(s4);
  Print(L"%d\n",Result);
  
  return EFI_SUCCESS;
}

 

运行结果：

具体实现的代码可以在下面找到：

\MdePkg\Library\BaseLib\String.c

 while (InternalIsDecimalDigitCharacter (*String)) {
    //
    // If the number represented by String overflows according 
    // to the range defined by UINTN, then ASSERT().
    //
    ASSERT (Result <= ((((UINTN) ~0) - (*String - L'0')) / 10));

    Result = Result * 10 + (*String - L'0');
    String++;
  }


/**
  Check if a Unicode character is a decimal character.

  This internal function checks if a Unicode character is a 
  decimal character. The valid decimal character is from
  L'0' to L'9'.

  @param  Char  The character to check against.

  @retval TRUE  If the Char is a decmial character.
  @retval FALSE If the Char is not a decmial character.

**/
BOOLEAN
EFIAPI
InternalIsDecimalDigitCharacter (
  IN      CHAR16                    Char
  )
{
  return (BOOLEAN) (Char >= L'0' && Char <= L'9');
}

 

从上面可以看到：最后一个字符会被忽略，所以你写 77f 或者 77z都能得到同样的结果

再测试一下具体取值的大小

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>


extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  CHAR16 *s1=L"100000000";
  CHAR16 *s2=L"987654321Z";  
  CHAR16 *s3=L"2147483647";   // == 7FFFFFFF
  CHAR16 *s4=L"2147483648";   // == 80000000
  CHAR16 *s5=L"-1";    
  UINTN Result;
  
  Result=StrDecimalToUintn(s1);
  Print(L"%d\n",Result);

  Result=StrDecimalToUintn(s2);
  Print(L"%d\n",Result);

  Result=StrDecimalToUintn(s3);
  Print(L"%d\n",Result);

  Result=StrDecimalToUintn(s4);
  Print(L"%d\n",Result);
  Result=StrDecimalToUintn(s5);
  Print(L"%d\n",Result);
  
  return EFI_SUCCESS;
}

 

运行结果

3.StrDecimalToUint64 函数用途：将字符串转换为数值，和前面的函数相比，可用范围更大

/**
  Convert a Null-terminated Unicode decimal string to a value of
  type UINT64.

  This function returns a value of type UINT64 by interpreting the contents
  of the Unicode string specified by String as a decimal number. The format
  of the input Unicode string String is:

                  [spaces] [decimal digits].

  The valid decimal digit character is in the range [0-9]. The
  function will ignore the pad space, which includes spaces or
  tab characters, before [decimal digits]. The running zero in the
  beginning of [decimal digits] will be ignored. Then, the function
  stops at the first character that is a not a valid decimal character
  or a Null-terminator, whichever one comes first.

  If String is NULL, then ASSERT().
  If String is not aligned in a 16-bit boundary, then ASSERT().
  If String has only pad spaces, then 0 is returned.
  If String has no pad spaces or valid decimal digits,
  then 0 is returned.
  If the number represented by String overflows according
  to the range defined by UINT64, then ASSERT().

  If PcdMaximumUnicodeStringLength is not zero, and String contains
  more than PcdMaximumUnicodeStringLength Unicode characters not including
  the Null-terminator, then ASSERT().

  @param  String          The pointer to a Null-terminated Unicode string.

  @retval Value translated from String.

**/
UINT64
EFIAPI
StrDecimalToUint64 (
  IN      CONST CHAR16              *String
  );

 

实例代码：

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>


extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  CHAR16 *s1=L"100000000";
  CHAR16 *s2=L"9876543210000Z";  
  CHAR16 *s3=L"2147483647";   // == 7FFFFFFF
  CHAR16 *s4=L"2147483648";   // == 80000000
  CHAR16 *s5=L"-1";    
  UINT64 Result;
  
  Result=StrDecimalToUint64(s1);
  Print(L"%ld\n",Result);

  Result=StrDecimalToUint64(s2);
  Print(L"\n%Ld\n",Result);
  Result=StrDecimalToUint64(s2);
  Print(L"%LX\n\n",Result);

  
  Result=StrDecimalToUint64(s3);
  Print(L"%Ld\n",Result);

  Result=StrDecimalToUint64(s4);
  Print(L"%Ld\n",Result);
  
  Result=StrDecimalToUint64(s5);
  Print(L"%Ld\n",Result);
  
  return EFI_SUCCESS;
}

 

运行结果：

4.StrHexToUintn 函数作用：将字符串按照十六进制处理转换为数值

/**
  Convert a Null-terminated Unicode hexadecimal string to a value of type UINTN.

  This function returns a value of type UINTN by interpreting the contents
  of the Unicode string specified by String as a hexadecimal number.
  The format of the input Unicode string String is:

                  [spaces][zeros][x][hexadecimal digits].

  The valid hexadecimal digit character is in the range [0-9], [a-f] and [A-F].
  The prefix "0x" is optional. Both "x" and "X" is allowed in "0x" prefix.
  If "x" appears in the input string, it must be prefixed with at least one 0.
  The function will ignore the pad space, which includes spaces or tab characters,
  before [zeros], [x] or [hexadecimal digit]. The running zero before [x] or
  [hexadecimal digit] will be ignored. Then, the decoding starts after [x] or the
  first valid hexadecimal digit. Then, the function stops at the first character 
  that is a not a valid hexadecimal character or NULL, whichever one comes first.

  If String is NULL, then ASSERT().
  If String is not aligned in a 16-bit boundary, then ASSERT().
  If String has only pad spaces, then zero is returned.
  If String has no leading pad spaces, leading zeros or valid hexadecimal digits,
  then zero is returned.
  If the number represented by String overflows according to the range defined by
  UINTN, then ASSERT().

  If PcdMaximumUnicodeStringLength is not zero, and String contains more than
  PcdMaximumUnicodeStringLength Unicode characters not including the Null-terminator,
  then ASSERT().

  @param  String          The pointer to a Null-terminated Unicode string.

  @retval Value translated from String.

**/
UINTN
EFIAPI
StrHexToUintn (
  IN      CONST CHAR16              *String
  );

 

示例代码：

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>


extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  CHAR16 *s1=L"0x234";
  CHAR16 *s2=L"1024";  
  UINTN Result;
  
  Result=StrHexToUintn(s1);
  Print(L"%d\n",Result);

  Result=StrHexToUintn(s2);
  Print(L"%d\n",Result);
  
  return EFI_SUCCESS;
}

 

运行结果

5.StrHexToUint64 函数作用：把字符串按照十六进制处理转化为数值

/**
  Convert a Null-terminated Unicode hexadecimal string to a value of type UINT64.

  This function returns a value of type UINT64 by interpreting the contents
  of the Unicode string specified by String as a hexadecimal number.
  The format of the input Unicode string String is

                  [spaces][zeros][x][hexadecimal digits].

  The valid hexadecimal digit character is in the range [0-9], [a-f] and [A-F].
  The prefix "0x" is optional. Both "x" and "X" is allowed in "0x" prefix.
  If "x" appears in the input string, it must be prefixed with at least one 0.
  The function will ignore the pad space, which includes spaces or tab characters,
  before [zeros], [x] or [hexadecimal digit]. The running zero before [x] or
  [hexadecimal digit] will be ignored. Then, the decoding starts after [x] or the
  first valid hexadecimal digit. Then, the function stops at the first character that is
  a not a valid hexadecimal character or NULL, whichever one comes first.

  If String is NULL, then ASSERT().
  If String is not aligned in a 16-bit boundary, then ASSERT().
  If String has only pad spaces, then zero is returned.
  If String has no leading pad spaces, leading zeros or valid hexadecimal digits,
  then zero is returned.
  If the number represented by String overflows according to the range defined by
  UINT64, then ASSERT().

  If PcdMaximumUnicodeStringLength is not zero, and String contains more than
  PcdMaximumUnicodeStringLength Unicode characters not including the Null-terminator,
  then ASSERT().

  @param  String          The pointer to a Null-terminated Unicode string.

  @retval Value translated from String.

**/
UINT64
EFIAPI
StrHexToUint64 (
  IN      CONST CHAR16             *String
  );

 

示例代码：

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>


extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  CHAR16 *s1=L"0x234";
  CHAR16 *s2=L"0xFFFFFFFFFFFFFFFF";  
  UINT64 Result;
  
  Result=StrHexToUint64(s1);
  Print(L"%ld\n",Result);

  Result=StrHexToUint64(s2);
  Print(L"%ld\n",Result);
  
  return EFI_SUCCESS;
}

 

运行结果：

6.UnicodeStrToAsciiStr 函数作用：将Unicode的字符串转换为 ASCII的字符串

/**
  Convert a Null-terminated Unicode string to a Null-terminated
  ASCII string and returns the ASCII string.

  This function converts the content of the Unicode string Source
  to the ASCII string Destination by copying the lower 8 bits of
  each Unicode character. It returns Destination.

  The caller is responsible to make sure Destination points to a buffer with size
  equal or greater than ((StrLen (Source) + 1) * sizeof (CHAR8)) in bytes.

  If any Unicode characters in Source contain non-zero value in
  the upper 8 bits, then ASSERT().

  If Destination is NULL, then ASSERT().
  If Source is NULL, then ASSERT().
  If Source is not aligned on a 16-bit boundary, then ASSERT().
  If Source and Destination overlap, then ASSERT().

  If PcdMaximumUnicodeStringLength is not zero, and Source contains
  more than PcdMaximumUnicodeStringLength Unicode characters not including
  the Null-terminator, then ASSERT().

  If PcdMaximumAsciiStringLength is not zero, and Source contains more
  than PcdMaximumAsciiStringLength Unicode characters not including the
  Null-terminator, then ASSERT().

  @param  Source        The pointer to a Null-terminated Unicode string.
  @param  Destination   The pointer to a Null-terminated ASCII string.

  @return Destination.

**/
CHAR8 *
EFIAPI
UnicodeStrToAsciiStr (
  IN      CONST CHAR16              *Source,
  OUT     CHAR8                     *Destination
  );

 

示例代码

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>


extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  CHAR16 *s1=L"www.lab-z.com";
  CHAR8  *s2="              ";  
  CHAR8 *Result;
  
  Result=UnicodeStrToAsciiStr(s1,s2);
  Print(L"%a\n",s2);
  Print(L"%a\n",Result);
  
  return EFI_SUCCESS;
}

 

运行结果

7.AsciiStrToUnicodeStr 函数作用：将 ASCII的字符串转换为 Unicode的字符串

/**
  Convert one Null-terminated ASCII string to a Null-terminated
  Unicode string and returns the Unicode string.

  This function converts the contents of the ASCII string Source to the Unicode
  string Destination, and returns Destination.  The function terminates the
  Unicode string Destination by appending a Null-terminator character at the end.
  The caller is responsible to make sure Destination points to a buffer with size
  equal or greater than ((AsciiStrLen (Source) + 1) * sizeof (CHAR16)) in bytes.

  If Destination is NULL, then ASSERT().
  If Destination is not aligned on a 16-bit boundary, then ASSERT().
  If Source is NULL, then ASSERT().
  If Source and Destination overlap, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero, and Source contains more than
  PcdMaximumAsciiStringLength ASCII characters not including the Null-terminator,
  then ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and Source contains more than
  PcdMaximumUnicodeStringLength ASCII characters not including the
  Null-terminator, then ASSERT().

  @param  Source        The pointer to a Null-terminated ASCII string.
  @param  Destination   The pointer to a Null-terminated Unicode string.

  @return Destination.

**/
CHAR16 *
EFIAPI
AsciiStrToUnicodeStr (
  IN      CONST CHAR8               *Source,
  OUT     CHAR16                    *Destination
  );

 

示例代码：

#include  <Uefi.h>
#include  <Library/UefiLib.h>
#include  <Library/ShellCEntryLib.h>


extern EFI_BOOT_SERVICES         *gBS;
extern EFI_SYSTEM_TABLE			 *gST;
extern EFI_RUNTIME_SERVICES 	 *gRT;

int
EFIAPI
main (
  IN int Argc,
  IN CHAR16 **Argv
  )
{
  CHAR8  *s1="www.lab-z.com";
  CHAR16 *s2=L"             ";  
  CHAR16 *Result;
  
  Result=AsciiStrToUnicodeStr (s1,s2);
  Print(L"%s\n",s2);
  Print(L"%s\n",Result);
  
  return EFI_SUCCESS;
}

 

运行结果和前面的相同。