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