/**
Get the image file buffer data and buffer size by its device path.
Access the file either from a firmware volume, from a file system interface,
or from the load file interface.
Allocate memory to store the found image. The caller is responsible to free memory.
If FilePath is NULL, then NULL is returned.
If FileSize is NULL, then NULL is returned.
If AuthenticationStatus is NULL, then NULL is returned.
@param[in] BootPolicy Policy for Open Image File.If TRUE, indicates
that the request originates from the boot
manager, and that the boot manager is
attempting to load FilePath as a boot
selection. If FALSE, then FilePath must
match an exact file to be loaded.
@param[in] FilePath The pointer to the device path of the file
that is abstracted to the file buffer.
@param[out] FileSize The pointer to the size of the abstracted
file buffer.
@param[out] AuthenticationStatus Pointer to the authentication status.
@retval NULL FilePath is NULL, or FileSize is NULL, or AuthenticationStatus is NULL, or the file can't be found.
@retval other The abstracted file buffer. The caller is responsible to free memory.
**/
VOID *
EFIAPI
GetFileBufferByFilePath (
IN BOOLEAN BootPolicy,
IN CONST EFI_DEVICE_PATH_PROTOCOL *FilePath,
OUT UINTN *FileSize,
OUT UINT32 *AuthenticationStatus
)
进一步研究，上述函数通过 EFI_FIRMWARE_VOLUME2_PROTOCOL 来完成读取。这个 Protocol 在 PI Spec （并不是 UEFI Spec）中有描述：
/**
Locates the requested section within a file and returns it in a buffer.
ReadSection() is used to retrieve a specific section from a file
within a firmware volume. The section returned is determined
using a depth-first, left-to-right search algorithm through all
sections found in the specified file. The output buffer is specified by a double indirection
of the Buffer parameter. The input value of Buffer is used to
determine if the output buffer is caller allocated or is
dynamically allocated by ReadSection(). If the input value of
Buffer!=NULL, it indicates that the output buffer is caller
allocated. In this case, the input value of *BufferSize
indicates the size of the caller-allocated output buffer. If
the output buffer is not large enough to contain the entire
requested output, it is filled up to the point that the output
buffer is exhausted and EFI_WARN_BUFFER_TOO_SMALL is returned,
and then BufferSize is returned with the size that is required
to successfully complete the read. All other
output parameters are returned with valid values. If the input
value of *Buffer==NULL, it indicates the output buffer is to
be allocated by ReadSection(). In this case, ReadSection()
will allocate an appropriately sized buffer from boot services
pool memory, which will be returned in *Buffer. The size of
the new buffer is returned in *BufferSize and all other output
parameters are returned with valid values. ReadSection() is
callable only from TPL_NOTIFY and below. Behavior of
ReadSection() at any EFI_TPL above TPL_NOTIFY is
undefined.
@param This Indicates the EFI_FIRMWARE_VOLUME2_PROTOCOL instance.
@param NameGuid Pointer to an EFI_GUID, which indicates the
file name from which the requested section
will be read.
@param SectionType Indicates the section type to return.
SectionType in conjunction with
SectionInstance indicates which section to
return.
@param SectionInstance Indicates which instance of sections
with a type of SectionType to return.
SectionType in conjunction with
SectionInstance indicates which
section to return. SectionInstance is
zero based.
@param Buffer Pointer to a pointer to a buffer in which the
section contents are returned, not including
the section header.
@param BufferSize Pointer to a caller-allocated UINTN. It
indicates the size of the memory
represented by Buffer.
@param AuthenticationStatus Pointer to a caller-allocated
UINT32 in which the authentication
status is returned.
@retval EFI_SUCCESS The call completed successfully.
@retval EFI_WARN_BUFFER_TOO_SMALL The caller-allocated
buffer is too small to
contain the requested
output. The buffer is
filled and the output is
truncated.
@retval EFI_OUT_OF_RESOURCES An allocation failure occurred.
@retval EFI_NOT_FOUND The requested file was not found in
the firmware volume. EFI_NOT_FOUND The
requested section was not found in the
specified file.
@retval EFI_DEVICE_ERROR A hardware error occurred when
attempting to access the firmware
volume.
@retval EFI_ACCESS_DENIED The firmware volume is configured to
disallow reads. EFI_PROTOCOL_ERROR
The requested section was not found,
but the file could not be fully
parsed because a required
GUIDED_SECTION_EXTRACTION_PROTOCOL
was not found. It is possible the
requested section exists within the
file and could be successfully
extracted once the required
GUIDED_SECTION_EXTRACTION_PROTOCOL
is published.
**/
typedef
EFI_STATUS
(EFIAPI * EFI_FV_READ_SECTION)(
IN CONST EFI_FIRMWARE_VOLUME2_PROTOCOL *This,
IN CONST EFI_GUID *NameGuid,
IN EFI_SECTION_TYPE SectionType,
IN UINTN SectionInstance,
IN OUT VOID **Buffer,
IN OUT UINTN *BufferSize,
OUT UINT32 *AuthenticationStatus
);
/**
Locates a section in a given FFS File and
copies it to the supplied buffer (not including section header).
@param This Indicates the calling context.
@param NameGuid Pointer to an EFI_GUID, which is the
filename.
@param SectionType Indicates the section type to return.
@param SectionInstance Indicates which instance of sections with a
type of SectionType to return.
@param Buffer Buffer is a pointer to pointer to a buffer
in which the file or section contents or are
returned.
@param BufferSize BufferSize is a pointer to caller allocated
UINTN.
@param AuthenticationStatus AuthenticationStatus is a pointer to a
caller allocated UINT32 in which the
authentication status is returned.
@retval EFI_SUCCESS Successfully read the file section into
buffer.
@retval EFI_WARN_BUFFER_TOO_SMALL Buffer too small.
@retval EFI_NOT_FOUND Section not found.
@retval EFI_DEVICE_ERROR Device error.
@retval EFI_ACCESS_DENIED Could not read.
@retval EFI_INVALID_PARAMETER Invalid parameter.
**/
EFI_STATUS
EFIAPI
FvReadFileSection (
IN CONST EFI_FIRMWARE_VOLUME2_PROTOCOL *This,
IN CONST EFI_GUID *NameGuid,
IN EFI_SECTION_TYPE SectionType,
IN UINTN SectionInstance,
IN OUT VOID **Buffer,
IN OUT UINTN *BufferSize,
OUT UI
ESP32 带有 WIFI 功能，而众所周知要想让一个设备连接WIFI AP 需要告知设备对应 AP 的名称和密码，简单实验的话，可以直接在代码中写死这两个参数，但这种情况下烧写之后设备只能在固定的环境下使用。https://github.com/tzapu/wifimanager 这个项目可以解决上述问题。先说一下这个东西如何使用:
/**
Loads the non-volatile variables from the NvVars file on the
given file system.
@param[in] FsHandle - Handle for a gEfiSimpleFileSystemProtocolGuid instance
@return EFI_STATUS based on the success or failure of load operation
**/
EFI_STATUS
LoadNvVarsFromFs (
EFI_HANDLE FsHandle
)
4.具体读取动作在ReadNvVarsFile() 函数中：
/**
Reads the contents of the NvVars file on the file system
@param[in] FsHandle - Handle for a gEfiSimpleFileSystemProtocolGuid instance
@return EFI_STATUS based on the success or failure of the file read
**/
EFI_STATUS
ReadNvVarsFile (
IN EFI_HANDLE FsHandle
)
/**
Iterates through the variables in the buffer, and calls a callback
function for each variable found.
@param[in] CallbackFunction - Function called for each variable instance
@param[in] Context - Passed to each call of CallbackFunction
@param[in] Buffer - Buffer containing serialized variables
@param[in] MaxSize - Size of Buffer in bytes
@return EFI_STATUS based on the success or failure of the operation
**/
STATIC
EFI_STATUS
IterateVariablesInBuffer (
IN VARIABLE_SERIALIZATION_ITERATION_CALLBACK CallbackFunction,
IN VOID *CallbackContext,
IN VOID *Buffer,
IN UINTN MaxSize
)
The preprocessor directive %error will cause NASM to report an error if it occurs in assembled code. So if other users are going to try to assemble your source files, you can ensure that they define the right macros by means of code like this:
%ifdef F1
; do some setup
%elifdef F2
; do some different setup
%else
%error “Neither F1 nor F2 was defined.”
%endif
Then any user who fails to understand the way your code is supposed to be assembled will be quickly warned of their mistake, rather than having to wait until the program crashes on being run and then not knowing what went wrong.
Similarly, %warning issues a warning, but allows assembly to continue:
%ifdef F1
; do some setup
%elifdef F2
; do some different setup
%else
%warning “Neither F1 nor F2 was defined, assuming F1.”
%define F1
%endif
%error and %warning are issued only on the final assembly pass. This makes them safe to use in conjunction with tests that depend on symbol values.
%fatal terminates assembly immediately, regardless of pass. This is useful when there is no point in continuing the assembly further, and doing so is likely just going to cause a spew of confusing error messages.
It is optional for the message string after %error, %warning or %fatal to be quoted. If it is not, then single-line macros are expanded in it, which can be used to display more information to the user. For example:
之前介绍过的通过WinPE启动，通过软件将安装好的硬盘制作成镜像，然后当有需要时直接恢复的方法。但是更多时候我们出于测试的目的，需要安装最新版本的 Pure OS。 这次介绍的全自动安装也就是无人值守模式安装，就是说只需要启动到安装盘上，Windows会自动完成包括分区格式化在内的全部工作。这是Windows自带的功能，只需要将特定的autounattend.xml 放置在启动盘的根目录下即可。具体做法如下：
