diff --git a/include/efi_api.h b/include/efi_api.h
index f5bb6ec..396f45e 100644
--- a/include/efi_api.h
+++ b/include/efi_api.h
@@ -858,17 +858,19 @@ struct efi_file_handle {
 	efi_status_t (EFIAPI *close)(struct efi_file_handle *file);
 	efi_status_t (EFIAPI *delete)(struct efi_file_handle *file);
 	efi_status_t (EFIAPI *read)(struct efi_file_handle *file,
-			u64 *buffer_size, void *buffer);
+			efi_uintn_t *buffer_size, void *buffer);
 	efi_status_t (EFIAPI *write)(struct efi_file_handle *file,
-			u64 *buffer_size, void *buffer);
+			efi_uintn_t *buffer_size, void *buffer);
 	efi_status_t (EFIAPI *getpos)(struct efi_file_handle *file,
-			u64 *pos);
+			efi_uintn_t *pos);
 	efi_status_t (EFIAPI *setpos)(struct efi_file_handle *file,
-			u64 pos);
+			efi_uintn_t pos);
 	efi_status_t (EFIAPI *getinfo)(struct efi_file_handle *file,
-			efi_guid_t *info_type, u64 *buffer_size, void *buffer);
+			efi_guid_t *info_type, efi_uintn_t *buffer_size,
+			void *buffer);
 	efi_status_t (EFIAPI *setinfo)(struct efi_file_handle *file,
-			efi_guid_t *info_type, u64 buffer_size, void *buffer);
+			efi_guid_t *info_type, efi_uintn_t buffer_size,
+			void *buffer);
 	efi_status_t (EFIAPI *flush)(struct efi_file_handle *file);
 };
 
diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index d15a131..7a9449f 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -1513,7 +1513,7 @@ efi_status_t efi_load_image_from_path(struct efi_device_path *file_path,
 	struct efi_file_info *info = NULL;
 	struct efi_file_handle *f;
 	static efi_status_t ret;
-	uint64_t bs;
+	efi_uintn_t bs;
 
 	f = efi_file_from_path(file_path);
 	if (!f)
@@ -1534,7 +1534,8 @@ efi_status_t efi_load_image_from_path(struct efi_device_path *file_path,
 	if (ret)
 		goto error;
 
-	EFI_CALL(ret = f->read(f, &info->file_size, *buffer));
+	bs = info->file_size;
+	EFI_CALL(ret = f->read(f, &bs, *buffer));
 
 error:
 	free(info);
diff --git a/lib/efi_loader/efi_file.c b/lib/efi_loader/efi_file.c
index 52a4e74..0be0f8b 100644
--- a/lib/efi_loader/efi_file.c
+++ b/lib/efi_loader/efi_file.c
@@ -314,29 +314,41 @@ static efi_status_t dir_read(struct file_handle *fh, u64 *buffer_size,
 }
 
 static efi_status_t EFIAPI efi_file_read(struct efi_file_handle *file,
-		u64 *buffer_size, void *buffer)
+					 efi_uintn_t *buffer_size, void *buffer)
 {
 	struct file_handle *fh = to_fh(file);
 	efi_status_t ret = EFI_SUCCESS;
+	u64 bs;
 
 	EFI_ENTRY("%p, %p, %p", file, buffer_size, buffer);
 
+	if (!buffer_size || !buffer) {
+		ret = EFI_INVALID_PARAMETER;
+		goto error;
+	}
+
 	if (set_blk_dev(fh)) {
 		ret = EFI_DEVICE_ERROR;
 		goto error;
 	}
 
+	bs = *buffer_size;
 	if (fh->isdir)
-		ret = dir_read(fh, buffer_size, buffer);
+		ret = dir_read(fh, &bs, buffer);
 	else
-		ret = file_read(fh, buffer_size, buffer);
+		ret = file_read(fh, &bs, buffer);
+	if (bs <= SIZE_MAX)
+		*buffer_size = bs;
+	else
+		*buffer_size = SIZE_MAX;
 
 error:
 	return EFI_EXIT(ret);
 }
 
 static efi_status_t EFIAPI efi_file_write(struct efi_file_handle *file,
-		u64 *buffer_size, void *buffer)
+					  efi_uintn_t *buffer_size,
+					  void *buffer)
 {
 	struct file_handle *fh = to_fh(file);
 	efi_status_t ret = EFI_SUCCESS;
@@ -363,21 +375,27 @@ error:
 }
 
 static efi_status_t EFIAPI efi_file_getpos(struct efi_file_handle *file,
-		u64 *pos)
+					   efi_uintn_t *pos)
 {
 	struct file_handle *fh = to_fh(file);
+
 	EFI_ENTRY("%p, %p", file, pos);
-	*pos = fh->offset;
-	return EFI_EXIT(EFI_SUCCESS);
+
+	if (fh->offset <= SIZE_MAX) {
+		*pos = fh->offset;
+		return EFI_EXIT(EFI_SUCCESS);
+	} else {
+		return EFI_EXIT(EFI_DEVICE_ERROR);
+	}
 }
 
 static efi_status_t EFIAPI efi_file_setpos(struct efi_file_handle *file,
-		u64 pos)
+		efi_uintn_t pos)
 {
 	struct file_handle *fh = to_fh(file);
 	efi_status_t ret = EFI_SUCCESS;
 
-	EFI_ENTRY("%p, %llu", file, pos);
+	EFI_ENTRY("%p, %zu", file, pos);
 
 	if (fh->isdir) {
 		if (pos != 0) {
@@ -411,7 +429,9 @@ error:
 }
 
 static efi_status_t EFIAPI efi_file_getinfo(struct efi_file_handle *file,
-		efi_guid_t *info_type, u64 *buffer_size, void *buffer)
+					    efi_guid_t *info_type,
+					    efi_uintn_t *buffer_size,
+					    void *buffer)
 {
 	struct file_handle *fh = to_fh(file);
 	efi_status_t ret = EFI_SUCCESS;
@@ -461,9 +481,12 @@ error:
 }
 
 static efi_status_t EFIAPI efi_file_setinfo(struct efi_file_handle *file,
-		efi_guid_t *info_type, u64 buffer_size, void *buffer)
+					    efi_guid_t *info_type,
+					    efi_uintn_t buffer_size,
+					    void *buffer)
 {
-	EFI_ENTRY("%p, %p, %llu, %p", file, info_type, buffer_size, buffer);
+	EFI_ENTRY("%p, %p, %zu, %p", file, info_type, buffer_size, buffer);
+
 	return EFI_EXIT(EFI_UNSUPPORTED);
 }
 
diff --git a/lib/efi_selftest/efi_selftest_block_device.c b/lib/efi_selftest/efi_selftest_block_device.c
index 9e4b93d..b07b224 100644
--- a/lib/efi_selftest/efi_selftest_block_device.c
+++ b/lib/efi_selftest/efi_selftest_block_device.c
@@ -302,7 +302,7 @@ static int execute(void)
 	struct efi_device_path *dp_partition;
 	struct efi_simple_file_system_protocol *file_system;
 	struct efi_file_handle *root, *file;
-	u64 buf_size;
+	efi_uintn_t buf_size;
 	char buf[16] __aligned(ARCH_DMA_MINALIGN);
 
 	ret = boottime->connect_controller(disk_handle, NULL, NULL, 1);