1 files changed, 140 insertions, 0 deletions
diff --git a/src/boot/efi/initrd.c b/src/boot/efi/initrd.c
new file mode 100644
index 0000000..d994ef8
--- /dev/null
+++ b/src/boot/efi/initrd.c
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <efi.h>
+#include <efilib.h>
+
+#include "initrd.h"
+#include "macro-fundamental.h"
+#include "missing_efi.h"
+#include "util.h"
+
+/* extend LoadFileProtocol */
+struct initrd_loader {
+        EFI_LOAD_FILE_PROTOCOL load_file;
+        const void *address;
+        UINTN length;
+};
+
+/* static structure for LINUX_INITRD_MEDIA device path
+   see https://github.com/torvalds/linux/blob/v5.13/drivers/firmware/efi/libstub/efi-stub-helper.c
+ */
+static const struct {
+        VENDOR_DEVICE_PATH vendor;
+        EFI_DEVICE_PATH end;
+} _packed_ efi_initrd_device_path = {
+        .vendor = {
+                .Header = {
+                        .Type = MEDIA_DEVICE_PATH,
+                        .SubType = MEDIA_VENDOR_DP,
+                        .Length = { sizeof(efi_initrd_device_path.vendor), 0 }
+                },
+                .Guid = LINUX_INITRD_MEDIA_GUID
+        },
+        .end = {
+                .Type = END_DEVICE_PATH_TYPE,
+                .SubType = END_ENTIRE_DEVICE_PATH_SUBTYPE,
+                .Length = { sizeof(efi_initrd_device_path.end), 0 }
+        }
+};
+
+static EFIAPI EFI_STATUS initrd_load_file(
+                EFI_LOAD_FILE_PROTOCOL *this,
+                EFI_DEVICE_PATH *file_path,
+                BOOLEAN boot_policy,
+                UINTN *buffer_size,
+                void *buffer) {
+
+        struct initrd_loader *loader;
+
+        if (!this || !buffer_size || !file_path)
+                return EFI_INVALID_PARAMETER;
+        if (boot_policy)
+                return EFI_UNSUPPORTED;
+
+        loader = (struct initrd_loader *) this;
+
+        if (loader->length == 0 || !loader->address)
+                return EFI_NOT_FOUND;
+
+        if (!buffer || *buffer_size < loader->length) {
+                *buffer_size = loader->length;
+                return EFI_BUFFER_TOO_SMALL;
+        }
+
+        memcpy(buffer, loader->address, loader->length);
+        *buffer_size = loader->length;
+        return EFI_SUCCESS;
+}
+
+EFI_STATUS initrd_register(
+                const void *initrd_address,
+                UINTN initrd_length,
+                EFI_HANDLE *ret_initrd_handle) {
+
+        EFI_STATUS err;
+        EFI_DEVICE_PATH *dp = (EFI_DEVICE_PATH *) &efi_initrd_device_path;
+        EFI_HANDLE handle;
+        struct initrd_loader *loader;
+
+        assert(ret_initrd_handle);
+
+        if (!initrd_address || initrd_length == 0)
+                return EFI_SUCCESS;
+
+        /* check if a LINUX_INITRD_MEDIA_GUID DevicePath is already registered.
+           LocateDevicePath checks for the "closest DevicePath" and returns its handle,
+           where as InstallMultipleProtocolInterfaces only matches identical DevicePaths.
+         */
+        err = BS->LocateDevicePath(&EfiLoadFile2Protocol, &dp, &handle);
+        if (err != EFI_NOT_FOUND) /* InitrdMedia is already registered */
+                return EFI_ALREADY_STARTED;
+
+        loader = xnew(struct initrd_loader, 1);
+        *loader = (struct initrd_loader) {
+                .load_file.LoadFile = initrd_load_file,
+                .address = initrd_address,
+                .length = initrd_length
+        };
+
+        /* create a new handle and register the LoadFile2 protocol with the InitrdMediaPath on it */
+        err = BS->InstallMultipleProtocolInterfaces(
+                        ret_initrd_handle,
+                        &DevicePathProtocol, &efi_initrd_device_path,
+                        &EfiLoadFile2Protocol, loader,
+                        NULL);
+        if (err != EFI_SUCCESS)
+                free(loader);
+
+        return err;
+}
+
+EFI_STATUS initrd_unregister(EFI_HANDLE initrd_handle) {
+        EFI_STATUS err;
+        struct initrd_loader *loader;
+
+        if (!initrd_handle)
+                return EFI_SUCCESS;
+
+        /* get the LoadFile2 protocol that we allocated earlier */
+        err = BS->OpenProtocol(
+                        initrd_handle, &EfiLoadFile2Protocol, (void **) &loader,
+                        NULL, NULL, EFI_OPEN_PROTOCOL_GET_PROTOCOL);
+        if (err != EFI_SUCCESS)
+                return err;
+
+        /* close the handle */
+        (void) BS->CloseProtocol(initrd_handle, &EfiLoadFile2Protocol, NULL, NULL);
+
+        /* uninstall all protocols thus destroying the handle */
+        err = BS->UninstallMultipleProtocolInterfaces(
+                        initrd_handle,
+                        &DevicePathProtocol, &efi_initrd_device_path,
+                        &EfiLoadFile2Protocol, loader,
+                        NULL);
+        if (err != EFI_SUCCESS)
+                return err;
+
+        initrd_handle = NULL;
+        free(loader);
+        return EFI_SUCCESS;
+}