Add lesson 20

1 files changed, 93 insertions, 0 deletions

diff --git a/Lesson_20/UefiLessonsPkg/ShowBootVariables/ShowBootVariables.c b/Lesson_20/UefiLessonsPkg/ShowBootVariables/ShowBootVariables.c
new file mode 100644
index 0000000..7f6b58c
--- /dev/null
+++ b/Lesson_20/UefiLessonsPkg/ShowBootVariables/ShowBootVariables.c
@@ -0,0 +1,93 @@
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/UefiLib.h>
+
+#include <Library/MemoryAllocationLib.h>
+#include <Library/UefiRuntimeServicesTableLib.h>
+
+#include <Library/DevicePathLib.h>
+#include <Library/PrintLib.h>
+
+
+EFI_STATUS
+GetNvramVariable( CHAR16   *VariableName,
+                  EFI_GUID *VariableOwnerGuid, 
+                  VOID     **Buffer,
+                  UINTN    *BufferSize)
+{
+    UINTN Size = 0;
+    *BufferSize = 0;
+
+    EFI_STATUS Status = gRT->GetVariable(VariableName, VariableOwnerGuid, NULL, &Size, NULL);
+    if (Status != EFI_BUFFER_TOO_SMALL) {
+        Print(L"Error! 'gRT->GetVariable' call returned %r\n", Status);
+        return Status;
+    }
+
+    *Buffer = AllocateZeroPool(Size);
+    if (!Buffer) {
+        Print(L"Error! 'AllocateZeroPool' call returned %r\n", Status);
+        return EFI_OUT_OF_RESOURCES;
+    }
+
+    Status = gRT->GetVariable(VariableName, VariableOwnerGuid, NULL, &Size, *Buffer);
+    if (Status == EFI_SUCCESS) {
+        *BufferSize = Size;
+    } else {
+        FreePool( *Buffer );
+        *Buffer = NULL;
+    }
+
+    return Status;
+}
+
+
+VOID PrintBootOption(CHAR16* BootOptionName)
+{
+  UINTN OptionSize;
+  UINT8* Buffer;
+ 
+  EFI_STATUS Status = GetNvramVariable(BootOptionName, &gEfiGlobalVariableGuid, (VOID**)&Buffer, &OptionSize);
+  if (Status == EFI_SUCCESS) {
+      EFI_LOAD_OPTION* LoadOption = (EFI_LOAD_OPTION*) Buffer;
+      CHAR16* Description = (CHAR16*)(Buffer + sizeof (EFI_LOAD_OPTION));
+      UINTN DescriptionSize = StrSize(Description);
+
+      Print(L"%s\n", Description);
+      if (LoadOption->FilePathListLength != 0) {
+        VOID* FilePathList = (UINT8 *)Description + DescriptionSize;
+        CHAR16* DevPathString = ConvertDevicePathToText(FilePathList, TRUE, FALSE);
+        Print(L"%s\n", DevPathString);
+      }
+  } else {
+    Print(L"Can't get %s variable\n", BootOptionName);
+  }
+}
+
+
+INTN EFIAPI ShellAppMain(IN UINTN Argc, IN CHAR16 **Argv)
+{
+  UINTN OptionSize;
+  EFI_STATUS Status;
+
+  UINT16* BootCurrent;
+  Status = GetNvramVariable(L"BootCurrent", &gEfiGlobalVariableGuid, (VOID**)&BootCurrent, &OptionSize);
+  if (Status != EFI_SUCCESS) {
+    Print(L"Can't get BootCurrent variable\n");
+  }
+
+  UINT16* BootOrderArray;
+  Status = GetNvramVariable(L"BootOrder", &gEfiGlobalVariableGuid, (VOID**)&BootOrderArray, &OptionSize);
+  if (Status == EFI_SUCCESS) {
+    for (UINTN i=0; i<(OptionSize/sizeof(UINT16)); i++) {
+      CHAR16 BootOptionStr[sizeof("Boot####")+1];
+      UnicodeSPrint(BootOptionStr, (sizeof("Boot####")+1)*sizeof(CHAR16), L"Boot%04x", BootOrderArray[i]);
+      Print(L"%s%s\n", BootOptionStr, (BootOrderArray[i] == *BootCurrent)? L"*" : L"" );
+      PrintBootOption(BootOptionStr);
+      Print(L"\n");
+    }
+  } else {
+    Print(L"Can't get BootOrder variable\n");
+  }
+
+  return EFI_SUCCESS;
+}