1 files changed, 88 insertions, 0 deletions
diff --git a/drivers/firmware/efi/efi-bgrt.c b/drivers/firmware/efi/efi-bgrt.c
new file mode 100644
index 000000000..6aafdb67d
--- /dev/null
+++ b/drivers/firmware/efi/efi-bgrt.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2012 Intel Corporation
+ * Author: Josh Triplett <josh@joshtriplett.org>
+ *
+ * Based on the bgrt driver:
+ * Copyright 2012 Red Hat, Inc <mjg@redhat.com>
+ * Author: Matthew Garrett
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/acpi.h>
+#include <linux/efi.h>
+#include <linux/efi-bgrt.h>
+
+struct acpi_table_bgrt bgrt_tab;
+size_t bgrt_image_size;
+
+struct bmp_header {
+	u16 id;
+	u32 size;
+} __packed;
+
+void __init efi_bgrt_init(struct acpi_table_header *table)
+{
+	void *image;
+	struct bmp_header bmp_header;
+	struct acpi_table_bgrt *bgrt = &bgrt_tab;
+
+	if (acpi_disabled)
+		return;
+
+	if (!efi_enabled(EFI_MEMMAP))
+		return;
+
+	if (table->length < sizeof(bgrt_tab)) {
+		pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
+		       table->length, sizeof(bgrt_tab));
+		return;
+	}
+	*bgrt = *(struct acpi_table_bgrt *)table;
+	/*
+	 * Only version 1 is defined but some older laptops (seen on Lenovo
+	 * Ivy Bridge models) have a correct version 1 BGRT table with the
+	 * version set to 0, so we accept version 0 and 1.
+	 */
+	if (bgrt->version > 1) {
+		pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",
+		       bgrt->version);
+		goto out;
+	}
+	if (bgrt->image_type != 0) {
+		pr_notice("Ignoring BGRT: invalid image type %u (expected 0)\n",
+		       bgrt->image_type);
+		goto out;
+	}
+	if (!bgrt->image_address) {
+		pr_notice("Ignoring BGRT: null image address\n");
+		goto out;
+	}
+
+	if (efi_mem_type(bgrt->image_address) != EFI_BOOT_SERVICES_DATA) {
+		pr_notice("Ignoring BGRT: invalid image address\n");
+		goto out;
+	}
+	image = early_memremap(bgrt->image_address, sizeof(bmp_header));
+	if (!image) {
+		pr_notice("Ignoring BGRT: failed to map image header memory\n");
+		goto out;
+	}
+
+	memcpy(&bmp_header, image, sizeof(bmp_header));
+	early_memunmap(image, sizeof(bmp_header));
+	if (bmp_header.id != 0x4d42) {
+		pr_notice("Ignoring BGRT: Incorrect BMP magic number 0x%x (expected 0x4d42)\n",
+			bmp_header.id);
+		goto out;
+	}
+	bgrt_image_size = bmp_header.size;
+	efi_mem_reserve(bgrt->image_address, bgrt_image_size);
+
+	return;
+out:
+	memset(bgrt, 0, sizeof(bgrt_tab));
+}