[BOOT] Add EFI headers and entry point

BOOT/ENVIRON/APP/BOOTMGR/EFI/efientry.c

@@ -0,0 +1,60 @@
+/*++
+
+Copyright (c) 2024, the LibreXP developers.
+Provided under the BSD 3-Clause license.
+
+Module Name:
+
+   entry.c
+
+Abstract:
+
+   Boot manager entry point on EFI systems.
+
+--*/
+
+#include "bootmgr.h"
+
+EFI_STATUS
+EFIAPI
+EfiEntry (
+    IN EFI_HANDLE ImageHandle,
+    IN EFI_SYSTEM_TABLE *SystemTable
+    )
+
+/*++
+
+Routine Description:
+
+    Boot manager entry point from EFI firmware.
+
+Arguments:
+
+    ImageHandle - Handle for the boot manager image.
+
+    SystemTable - Pointer to the EFI system table.
+
+Return Value:
+
+    EFI_SUCCESS if successful.
+    EFI_INVALID_PARAMEER if input parameter structure creation fails.
+    Any other value defined in efierr.h.
+
+--*/
+
+{
+    PBOOT_APPLICATION_PARAMETERS InputParameters;
+
+    //
+    // Create firmware-independent input structure from EFI parameters.
+    //
+    InputParameters = EfiInitCreateInputParameters(ImageHandle, SystemTable);
+    if (InputParameters == NULL) {
+        return EFI_INVALID_PARAMETER;
+    }
+
+    //
+    // Transfer control to the firmware-independent boot manager.
+    //
+    return EfiGetEfiStatusCode(BmMain(InputParameters));
+}

BOOT/ENVIRON/APP/BOOTMGR/bootmgr.c

@@ -0,0 +1,44 @@
+/*++
+
+Copyright (c) 2024, the LibreXP developers.
+Provided under the BSD 3-Clause license.
+
+Module Name:
+
+   bootmgr.c
+
+Abstract:
+
+   Main functions of the boot manager.
+
+--*/
+
+#include "bootmgr.h"
+
+NTSTATUS
+BmMain (
+    IN PBOOT_APPLICATION_PARAMETERS Parameters
+    )
+
+/*++
+
+Routine Description:
+
+    Firmware-independent boot manager entry point.
+
+Arguments:
+
+    Parameters - Input parameters for the boot manager.
+
+Return Value:
+
+    Error code on failure.
+    Does not return on success, as control is transferred to the OS loader.
+
+--*/
+
+{
+    /* TODO: Implement BmMain() */
+
+    return STATUS_SUCCESS;
+}