1// SPDX-License-Identifier: GPL-2.0
2
3#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
4
5#include <linux/init.h>
6#include <linux/sched.h>
7#include <linux/kthread.h>
8#include <linux/workqueue.h>
9#include <linux/memblock.h>
10
11#include <asm/proto.h>
12#include <asm/setup.h>
13
14/*
15 * Some BIOSes seem to corrupt the low 64k of memory during events
16 * like suspend/resume and unplugging an HDMI cable. Reserve all
17 * remaining free memory in that area and fill it with a distinct
18 * pattern.
19 */
20#define MAX_SCAN_AREAS 8
21
22static int __read_mostly memory_corruption_check = -1;
23
24static unsigned __read_mostly corruption_check_size = 64*1024;
25static unsigned __read_mostly corruption_check_period = 60; /* seconds */
26
27static struct scan_area {
28 u64 addr;
29 u64 size;
30} scan_areas[MAX_SCAN_AREAS];
31static int num_scan_areas;
32
33static __init int set_corruption_check(char *arg)
34{
35 ssize_t ret;
36 unsigned long val;
37
38 if (!arg) {
39 pr_err("memory_corruption_check config string not provided\n");
40 return -EINVAL;
41 }
42
43 ret = kstrtoul(s: arg, base: 10, res: &val);
44 if (ret)
45 return ret;
46
47 memory_corruption_check = val;
48
49 return 0;
50}
51early_param("memory_corruption_check", set_corruption_check);
52
53static __init int set_corruption_check_period(char *arg)
54{
55 ssize_t ret;
56 unsigned long val;
57
58 if (!arg) {
59 pr_err("memory_corruption_check_period config string not provided\n");
60 return -EINVAL;
61 }
62
63 ret = kstrtoul(s: arg, base: 10, res: &val);
64 if (ret)
65 return ret;
66
67 corruption_check_period = val;
68 return 0;
69}
70early_param("memory_corruption_check_period", set_corruption_check_period);
71
72static __init int set_corruption_check_size(char *arg)
73{
74 char *end;
75 unsigned size;
76
77 if (!arg) {
78 pr_err("memory_corruption_check_size config string not provided\n");
79 return -EINVAL;
80 }
81
82 size = memparse(ptr: arg, retptr: &end);
83
84 if (*end == '\0')
85 corruption_check_size = size;
86
87 return (size == corruption_check_size) ? 0 : -EINVAL;
88}
89early_param("memory_corruption_check_size", set_corruption_check_size);
90
91
92void __init setup_bios_corruption_check(void)
93{
94 phys_addr_t start, end;
95 u64 i;
96
97 if (memory_corruption_check == -1) {
98 memory_corruption_check =
99#ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
100 1
101#else
102 0
103#endif
104 ;
105 }
106
107 if (corruption_check_size == 0)
108 memory_corruption_check = 0;
109
110 if (!memory_corruption_check)
111 return;
112
113 corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
114
115 for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
116 NULL) {
117 start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
118 PAGE_SIZE, corruption_check_size);
119 end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
120 PAGE_SIZE, corruption_check_size);
121 if (start >= end)
122 continue;
123
124 memblock_reserve(base: start, size: end - start);
125 scan_areas[num_scan_areas].addr = start;
126 scan_areas[num_scan_areas].size = end - start;
127
128 /* Assume we've already mapped this early memory */
129 memset(__va(start), c: 0, n: end - start);
130
131 if (++num_scan_areas >= MAX_SCAN_AREAS)
132 break;
133 }
134
135 if (num_scan_areas)
136 pr_info("Scanning %d areas for low memory corruption\n", num_scan_areas);
137}
138
139
140static void check_for_bios_corruption(void)
141{
142 int i;
143 int corruption = 0;
144
145 if (!memory_corruption_check)
146 return;
147
148 for (i = 0; i < num_scan_areas; i++) {
149 unsigned long *addr = __va(scan_areas[i].addr);
150 unsigned long size = scan_areas[i].size;
151
152 for (; size; addr++, size -= sizeof(unsigned long)) {
153 if (!*addr)
154 continue;
155 pr_err("Corrupted low memory at %p (%lx phys) = %08lx\n", addr, __pa(addr), *addr);
156 corruption = 1;
157 *addr = 0;
158 }
159 }
160
161 WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
162}
163
164static void check_corruption(struct work_struct *dummy);
165static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
166
167static void check_corruption(struct work_struct *dummy)
168{
169 check_for_bios_corruption();
170 schedule_delayed_work(dwork: &bios_check_work,
171 delay: round_jiffies_relative(j: corruption_check_period*HZ));
172}
173
174static int start_periodic_check_for_corruption(void)
175{
176 if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
177 return 0;
178
179 pr_info("Scanning for low memory corruption every %d seconds\n", corruption_check_period);
180
181 /* First time we run the checks right away */
182 schedule_delayed_work(dwork: &bios_check_work, delay: 0);
183
184 return 0;
185}
186device_initcall(start_periodic_check_for_corruption);
187
188