1 #include <linux/module.h>
2 #include <linux/sched.h>
3 #include <linux/kthread.h>
4 #include <linux/workqueue.h>
5 #include <linux/memblock.h>
6
7 #include <asm/proto.h>
8
9 /*
10 * Some BIOSes seem to corrupt the low 64k of memory during events
11 * like suspend/resume and unplugging an HDMI cable. Reserve all
12 * remaining free memory in that area and fill it with a distinct
13 * pattern.
14 */
15 #define MAX_SCAN_AREAS 8
16
17 static int __read_mostly memory_corruption_check = -1;
18
19 static unsigned __read_mostly corruption_check_size = 64*1024;
20 static unsigned __read_mostly corruption_check_period = 60; /* seconds */
21
22 static struct scan_area {
23 u64 addr;
24 u64 size;
25 } scan_areas[MAX_SCAN_AREAS];
26 static int num_scan_areas;
27
set_corruption_check(char * arg)28 static __init int set_corruption_check(char *arg)
29 {
30 ssize_t ret;
31 unsigned long val;
32
33 ret = kstrtoul(arg, 10, &val);
34 if (ret)
35 return ret;
36
37 memory_corruption_check = val;
38 return 0;
39 }
40 early_param("memory_corruption_check", set_corruption_check);
41
set_corruption_check_period(char * arg)42 static __init int set_corruption_check_period(char *arg)
43 {
44 ssize_t ret;
45 unsigned long val;
46
47 ret = kstrtoul(arg, 10, &val);
48 if (ret)
49 return ret;
50
51 corruption_check_period = val;
52 return 0;
53 }
54 early_param("memory_corruption_check_period", set_corruption_check_period);
55
set_corruption_check_size(char * arg)56 static __init int set_corruption_check_size(char *arg)
57 {
58 char *end;
59 unsigned size;
60
61 size = memparse(arg, &end);
62
63 if (*end == '\0')
64 corruption_check_size = size;
65
66 return (size == corruption_check_size) ? 0 : -EINVAL;
67 }
68 early_param("memory_corruption_check_size", set_corruption_check_size);
69
70
setup_bios_corruption_check(void)71 void __init setup_bios_corruption_check(void)
72 {
73 phys_addr_t start, end;
74 u64 i;
75
76 if (memory_corruption_check == -1) {
77 memory_corruption_check =
78 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
79 1
80 #else
81 0
82 #endif
83 ;
84 }
85
86 if (corruption_check_size == 0)
87 memory_corruption_check = 0;
88
89 if (!memory_corruption_check)
90 return;
91
92 corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
93
94 for_each_free_mem_range(i, NUMA_NO_NODE, &start, &end, NULL) {
95 start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
96 PAGE_SIZE, corruption_check_size);
97 end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
98 PAGE_SIZE, corruption_check_size);
99 if (start >= end)
100 continue;
101
102 memblock_reserve(start, end - start);
103 scan_areas[num_scan_areas].addr = start;
104 scan_areas[num_scan_areas].size = end - start;
105
106 /* Assume we've already mapped this early memory */
107 memset(__va(start), 0, end - start);
108
109 if (++num_scan_areas >= MAX_SCAN_AREAS)
110 break;
111 }
112
113 if (num_scan_areas)
114 printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas);
115 }
116
117
check_for_bios_corruption(void)118 void check_for_bios_corruption(void)
119 {
120 int i;
121 int corruption = 0;
122
123 if (!memory_corruption_check)
124 return;
125
126 for (i = 0; i < num_scan_areas; i++) {
127 unsigned long *addr = __va(scan_areas[i].addr);
128 unsigned long size = scan_areas[i].size;
129
130 for (; size; addr++, size -= sizeof(unsigned long)) {
131 if (!*addr)
132 continue;
133 printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
134 addr, __pa(addr), *addr);
135 corruption = 1;
136 *addr = 0;
137 }
138 }
139
140 WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
141 }
142
143 static void check_corruption(struct work_struct *dummy);
144 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
145
check_corruption(struct work_struct * dummy)146 static void check_corruption(struct work_struct *dummy)
147 {
148 check_for_bios_corruption();
149 schedule_delayed_work(&bios_check_work,
150 round_jiffies_relative(corruption_check_period*HZ));
151 }
152
start_periodic_check_for_corruption(void)153 static int start_periodic_check_for_corruption(void)
154 {
155 if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
156 return 0;
157
158 printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
159 corruption_check_period);
160
161 /* First time we run the checks right away */
162 schedule_delayed_work(&bios_check_work, 0);
163 return 0;
164 }
165
166 module_init(start_periodic_check_for_corruption);
167
168