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 ret = kstrtoul(arg, 10, &val);
35 if (ret)
36 return ret;
37
38 memory_corruption_check = val;
39 return 0;
40 }
41 early_param("memory_corruption_check", set_corruption_check);
42
set_corruption_check_period(char * arg)43 static __init int set_corruption_check_period(char *arg)
44 {
45 ssize_t ret;
46 unsigned long val;
47
48 ret = kstrtoul(arg, 10, &val);
49 if (ret)
50 return ret;
51
52 corruption_check_period = val;
53 return 0;
54 }
55 early_param("memory_corruption_check_period", set_corruption_check_period);
56
set_corruption_check_size(char * arg)57 static __init int set_corruption_check_size(char *arg)
58 {
59 char *end;
60 unsigned size;
61
62 size = memparse(arg, &end);
63
64 if (*end == '\0')
65 corruption_check_size = size;
66
67 return (size == corruption_check_size) ? 0 : -EINVAL;
68 }
69 early_param("memory_corruption_check_size", set_corruption_check_size);
70
71
setup_bios_corruption_check(void)72 void __init setup_bios_corruption_check(void)
73 {
74 phys_addr_t start, end;
75 u64 i;
76
77 if (memory_corruption_check == -1) {
78 memory_corruption_check =
79 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
80 1
81 #else
82 0
83 #endif
84 ;
85 }
86
87 if (corruption_check_size == 0)
88 memory_corruption_check = 0;
89
90 if (!memory_corruption_check)
91 return;
92
93 corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
94
95 for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
96 NULL) {
97 start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
98 PAGE_SIZE, corruption_check_size);
99 end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
100 PAGE_SIZE, corruption_check_size);
101 if (start >= end)
102 continue;
103
104 memblock_reserve(start, end - start);
105 scan_areas[num_scan_areas].addr = start;
106 scan_areas[num_scan_areas].size = end - start;
107
108 /* Assume we've already mapped this early memory */
109 memset(__va(start), 0, end - start);
110
111 if (++num_scan_areas >= MAX_SCAN_AREAS)
112 break;
113 }
114
115 if (num_scan_areas)
116 printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas);
117 }
118
119
check_for_bios_corruption(void)120 void check_for_bios_corruption(void)
121 {
122 int i;
123 int corruption = 0;
124
125 if (!memory_corruption_check)
126 return;
127
128 for (i = 0; i < num_scan_areas; i++) {
129 unsigned long *addr = __va(scan_areas[i].addr);
130 unsigned long size = scan_areas[i].size;
131
132 for (; size; addr++, size -= sizeof(unsigned long)) {
133 if (!*addr)
134 continue;
135 printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
136 addr, __pa(addr), *addr);
137 corruption = 1;
138 *addr = 0;
139 }
140 }
141
142 WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
143 }
144
145 static void check_corruption(struct work_struct *dummy);
146 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
147
check_corruption(struct work_struct * dummy)148 static void check_corruption(struct work_struct *dummy)
149 {
150 check_for_bios_corruption();
151 schedule_delayed_work(&bios_check_work,
152 round_jiffies_relative(corruption_check_period*HZ));
153 }
154
start_periodic_check_for_corruption(void)155 static int start_periodic_check_for_corruption(void)
156 {
157 if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
158 return 0;
159
160 printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
161 corruption_check_period);
162
163 /* First time we run the checks right away */
164 schedule_delayed_work(&bios_check_work, 0);
165 return 0;
166 }
167 device_initcall(start_periodic_check_for_corruption);
168
169
