From 212091811fabf0ae18c22c29f491da537af713ba Mon Sep 17 00:00:00 2001
From: Rafal Kupiec <belliash@codingworkshop.eu.org>
Date: Fri, 8 Dec 2023 15:57:44 +0100
Subject: [PATCH] Implement BlReadFile() routine

---
 xtldr2/includes/bootman.h |   7 +++
 xtldr2/protocol.c         |   5 +-
 xtldr2/volume.c           | 119 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 129 insertions(+), 2 deletions(-)

diff --git a/xtldr2/includes/bootman.h b/xtldr2/includes/bootman.h
index 2a1647a..cedf062 100644
--- a/xtldr2/includes/bootman.h
+++ b/xtldr2/includes/bootman.h
@@ -57,6 +57,13 @@ BlOpenVolume(IN PEFI_DEVICE_PATH_PROTOCOL DevicePath,
              OUT PEFI_HANDLE DiskHandle,
              OUT PEFI_FILE_HANDLE *FsHandle);
 
+XTCDECL
+EFI_STATUS
+BlReadFile(IN PEFI_FILE_HANDLE DirHandle,
+           IN CONST PWCHAR FileName,
+           OUT PVOID *FileData,
+           OUT PSIZE_T FileSize);
+
 XTCDECL
 VOID
 BlConsoleClearScreen();
diff --git a/xtldr2/protocol.c b/xtldr2/protocol.c
index 2a3d20c..53feebe 100644
--- a/xtldr2/protocol.c
+++ b/xtldr2/protocol.c
@@ -95,6 +95,9 @@ BlpRegisterXtLoaderProtocol()
     LdrProtocol.Console.EnableCursor = BlConsoleEnableCursor;
     LdrProtocol.Console.Print = BlConsolePrint;
     LdrProtocol.Debug.Print = BlDebugPrint;
+    LdrProtocol.Disk.CloseVolume = BlCloseVolume;
+    LdrProtocol.Disk.OpenVolume = BlOpenVolume;
+    LdrProtocol.Disk.ReadFile = BlReadFile;
     LdrProtocol.Memory.AllocatePages = BlMemoryAllocatePages;
     LdrProtocol.Memory.AllocatePool = BlMemoryAllocatePool;
     LdrProtocol.Memory.FreePages = BlMemoryFreePages;
@@ -102,8 +105,6 @@ BlpRegisterXtLoaderProtocol()
     LdrProtocol.Protocol.Open = BlOpenXtProtocol;
     LdrProtocol.Util.ExitBootServices = BlExitBootServices;
     LdrProtocol.Util.SleepExecution = BlSleepExecution;
-    LdrProtocol.Volume.Close = BlCloseVolume;
-    LdrProtocol.Volume.Open = BlOpenVolume;
 
     /* Register XTLDR loader protocol */
     BlDebugPrint(L"Registering XT loader protocol\n");
diff --git a/xtldr2/volume.c b/xtldr2/volume.c
index 8176190..8b11882 100644
--- a/xtldr2/volume.c
+++ b/xtldr2/volume.c
@@ -470,6 +470,125 @@ BlOpenVolume(IN PEFI_DEVICE_PATH_PROTOCOL DevicePath,
     return STATUS_EFI_SUCCESS;
 }
 
+/**
+ * Reads data from the file.
+ *
+ * @param DirHandle
+ *        Supplies a handle of the opened filesystem directory.
+ *
+ * @param FileName
+ *        Supplies the name of the file to read.
+ *
+ * @param FileData
+ *        Provides a buffer to store the data read from the file.
+ *
+ * @param FileSize
+ *        Provides a pointer to the variable to store a size of the buffer.
+ *
+ * @return This routine returns status code.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+EFI_STATUS
+BlReadFile(IN PEFI_FILE_HANDLE DirHandle,
+           IN CONST PWCHAR FileName,
+           OUT PVOID *FileData,
+           OUT PSIZE_T FileSize)
+{
+    EFI_GUID FileInfoGuid = EFI_FILE_INFO_PROTOCOL_GUID;
+    EFI_PHYSICAL_ADDRESS Address;
+    PEFI_FILE_HANDLE FileHandle;
+    PEFI_FILE_INFO FileInfo;
+    EFI_STATUS Status;
+    UINT_PTR ReadSize;
+    SIZE_T Pages;
+
+    Status = DirHandle->Open(DirHandle, &FileHandle, FileName, EFI_FILE_MODE_READ,
+                             EFI_FILE_READ_ONLY | EFI_FILE_HIDDEN | EFI_FILE_SYSTEM);
+    if(Status != STATUS_EFI_SUCCESS)
+    {
+        /* Failed to open file */
+        return Status;
+    }
+
+    /* Set required size for getting file information */
+    ReadSize = sizeof(EFI_FILE_INFO) + 32;
+
+    /* Allocate necessary amount of memory */
+    Status = BlMemoryAllocatePool(ReadSize, (PVOID *)&FileInfo);
+    if(Status != STATUS_EFI_SUCCESS)
+    {
+        /* Memory allocation failure */
+        FileHandle->Close(FileHandle);
+        return Status;
+    }
+
+    /* First attempt to get file information */
+    FileHandle->GetInfo(FileHandle, &FileInfoGuid, &ReadSize, FileInfo);
+    if(Status == STATUS_EFI_BUFFER_TOO_SMALL)
+    {
+        /* Buffer is too small, but EFI tells the required size, so reallocate */
+        BlMemoryFreePool(&FileInfo);
+        Status = BlMemoryAllocatePool(ReadSize, (PVOID *)&FileInfo);
+        if(Status != STATUS_EFI_SUCCESS)
+        {
+            /* Memory allocation failure */
+            FileHandle->Close(FileHandle);
+            return Status;
+        }
+
+        /* Second attempt to get file information */
+        Status = FileHandle->GetInfo(FileHandle, &FileInfoGuid, &ReadSize, FileInfo);
+    }
+
+    /* Check if file information got successfully */
+    if(Status != STATUS_EFI_SUCCESS)
+    {
+        /* Unable to get file information */
+        FileHandle->Close(FileHandle);
+        BlMemoryFreePool(&FileInfo);
+        return Status;
+    }
+
+    /* Store file size and calculate number of pages */
+    *FileSize = FileInfo->FileSize;
+    Pages = EFI_SIZE_TO_PAGES(FileInfo->FileSize);
+
+    /* Allocate pages */
+    Status = BlMemoryAllocatePages(Pages, &Address);
+    if(Status != STATUS_EFI_SUCCESS)
+    {
+        /* Pages allocation failure */
+        FileHandle->Close(FileHandle);
+        BlMemoryFreePool(&FileInfo);
+        return Status;
+    }
+
+    /* Calculate number of bytes to read and zero memory*/
+    ReadSize = Pages * EFI_PAGE_SIZE;
+    *FileData = (PCHAR)(UINT_PTR)Address;
+    RtlZeroMemory(*FileData, ReadSize);
+
+    /* Read data from the file */
+    Status = FileHandle->Read(FileHandle, &ReadSize, *FileData);
+    if(Status != STATUS_EFI_SUCCESS)
+    {
+        /* Failed to read data */
+        FileHandle->Close(FileHandle);
+        BlMemoryFreePool(&FileInfo);
+        BlMemoryFreePages(Pages, (EFI_PHYSICAL_ADDRESS)(UINT_PTR)*FileData);
+        return Status;
+    }
+
+    /* Close handle and free memory */
+    FileHandle->Close(FileHandle);
+    BlMemoryFreePool(&FileInfo);
+
+    /* Return success */
+    return STATUS_EFI_SUCCESS;
+}
+
 /**
  * Gets a list of block devices from an EFI enabled BIOS.
  *