xref: /openbmc/linux/drivers/firmware/efi/efi-bgrt.c (revision a977d045)
1 /*
2  * Copyright 2012 Intel Corporation
3  * Author: Josh Triplett <josh@joshtriplett.org>
4  *
5  * Based on the bgrt driver:
6  * Copyright 2012 Red Hat, Inc <mjg@redhat.com>
7  * Author: Matthew Garrett
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License version 2 as
11  * published by the Free Software Foundation.
12  */
13 
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15 
16 #include <linux/kernel.h>
17 #include <linux/init.h>
18 #include <linux/acpi.h>
19 #include <linux/efi.h>
20 #include <linux/efi-bgrt.h>
21 
22 struct acpi_table_bgrt bgrt_tab;
23 size_t __initdata bgrt_image_size;
24 
25 struct bmp_header {
26 	u16 id;
27 	u32 size;
28 } __packed;
29 
30 static bool efi_bgrt_addr_valid(u64 addr)
31 {
32 	efi_memory_desc_t *md;
33 
34 	for_each_efi_memory_desc(md) {
35 		u64 size;
36 		u64 end;
37 
38 		if (md->type != EFI_BOOT_SERVICES_DATA)
39 			continue;
40 
41 		size = md->num_pages << EFI_PAGE_SHIFT;
42 		end = md->phys_addr + size;
43 		if (addr >= md->phys_addr && addr < end)
44 			return true;
45 	}
46 
47 	return false;
48 }
49 
50 void __init efi_bgrt_init(struct acpi_table_header *table)
51 {
52 	void *image;
53 	struct bmp_header bmp_header;
54 	struct acpi_table_bgrt *bgrt = &bgrt_tab;
55 
56 	if (acpi_disabled)
57 		return;
58 
59 	if (!efi_enabled(EFI_MEMMAP))
60 		return;
61 
62 	if (table->length < sizeof(bgrt_tab)) {
63 		pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
64 		       table->length, sizeof(bgrt_tab));
65 		return;
66 	}
67 	*bgrt = *(struct acpi_table_bgrt *)table;
68 	if (bgrt->version != 1) {
69 		pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",
70 		       bgrt->version);
71 		goto out;
72 	}
73 	if (bgrt->status & 0xfe) {
74 		pr_notice("Ignoring BGRT: reserved status bits are non-zero %u\n",
75 		       bgrt->status);
76 		goto out;
77 	}
78 	if (bgrt->image_type != 0) {
79 		pr_notice("Ignoring BGRT: invalid image type %u (expected 0)\n",
80 		       bgrt->image_type);
81 		goto out;
82 	}
83 	if (!bgrt->image_address) {
84 		pr_notice("Ignoring BGRT: null image address\n");
85 		goto out;
86 	}
87 
88 	if (!efi_bgrt_addr_valid(bgrt->image_address)) {
89 		pr_notice("Ignoring BGRT: invalid image address\n");
90 		goto out;
91 	}
92 	image = early_memremap(bgrt->image_address, sizeof(bmp_header));
93 	if (!image) {
94 		pr_notice("Ignoring BGRT: failed to map image header memory\n");
95 		goto out;
96 	}
97 
98 	memcpy(&bmp_header, image, sizeof(bmp_header));
99 	early_memunmap(image, sizeof(bmp_header));
100 	if (bmp_header.id != 0x4d42) {
101 		pr_notice("Ignoring BGRT: Incorrect BMP magic number 0x%x (expected 0x4d42)\n",
102 			bmp_header.id);
103 		goto out;
104 	}
105 	bgrt_image_size = bmp_header.size;
106 	efi_mem_reserve(bgrt->image_address, bgrt_image_size);
107 
108 	return;
109 out:
110 	memset(bgrt, 0, sizeof(bgrt_tab));
111 }
112