1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright 2012 Intel Corporation
4  * Author: Josh Triplett <josh@joshtriplett.org>
5  *
6  * Based on the bgrt driver:
7  * Copyright 2012 Red Hat, Inc <mjg@redhat.com>
8  * Author: Matthew Garrett
9  */
10 
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 
13 #include <linux/kernel.h>
14 #include <linux/init.h>
15 #include <linux/acpi.h>
16 #include <linux/efi.h>
17 #include <linux/efi-bgrt.h>
18 
19 struct acpi_table_bgrt bgrt_tab;
20 size_t bgrt_image_size;
21 
22 struct bmp_header {
23 	u16 id;
24 	u32 size;
25 } __packed;
26 
efi_bgrt_init(struct acpi_table_header * table)27 void __init efi_bgrt_init(struct acpi_table_header *table)
28 {
29 	void *image;
30 	struct bmp_header bmp_header;
31 	struct acpi_table_bgrt *bgrt = &bgrt_tab;
32 
33 	if (acpi_disabled)
34 		return;
35 
36 	if (!efi_enabled(EFI_MEMMAP))
37 		return;
38 
39 	if (table->length < sizeof(bgrt_tab)) {
40 		pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
41 		       table->length, sizeof(bgrt_tab));
42 		return;
43 	}
44 	*bgrt = *(struct acpi_table_bgrt *)table;
45 	/*
46 	 * Only version 1 is defined but some older laptops (seen on Lenovo
47 	 * Ivy Bridge models) have a correct version 1 BGRT table with the
48 	 * version set to 0, so we accept version 0 and 1.
49 	 */
50 	if (bgrt->version > 1) {
51 		pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",
52 		       bgrt->version);
53 		goto out;
54 	}
55 	if (bgrt->image_type != 0) {
56 		pr_notice("Ignoring BGRT: invalid image type %u (expected 0)\n",
57 		       bgrt->image_type);
58 		goto out;
59 	}
60 	if (!bgrt->image_address) {
61 		pr_notice("Ignoring BGRT: null image address\n");
62 		goto out;
63 	}
64 
65 	if (efi_mem_type(bgrt->image_address) != EFI_BOOT_SERVICES_DATA) {
66 		pr_notice("Ignoring BGRT: invalid image address\n");
67 		goto out;
68 	}
69 	image = early_memremap(bgrt->image_address, sizeof(bmp_header));
70 	if (!image) {
71 		pr_notice("Ignoring BGRT: failed to map image header memory\n");
72 		goto out;
73 	}
74 
75 	memcpy(&bmp_header, image, sizeof(bmp_header));
76 	early_memunmap(image, sizeof(bmp_header));
77 	if (bmp_header.id != 0x4d42) {
78 		pr_notice("Ignoring BGRT: Incorrect BMP magic number 0x%x (expected 0x4d42)\n",
79 			bmp_header.id);
80 		goto out;
81 	}
82 	bgrt_image_size = bmp_header.size;
83 	efi_mem_reserve(bgrt->image_address, bgrt_image_size);
84 
85 	return;
86 out:
87 	memset(bgrt, 0, sizeof(bgrt_tab));
88 }
89