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 char *end;
31
32 memory_corruption_check = simple_strtol(arg, &end, 10);
33
34 return (*end == 0) ? 0 : -EINVAL;
35 }
36 early_param("memory_corruption_check", set_corruption_check);
37
set_corruption_check_period(char * arg)38 static __init int set_corruption_check_period(char *arg)
39 {
40 char *end;
41
42 corruption_check_period = simple_strtoul(arg, &end, 10);
43
44 return (*end == 0) ? 0 : -EINVAL;
45 }
46 early_param("memory_corruption_check_period", set_corruption_check_period);
47
set_corruption_check_size(char * arg)48 static __init int set_corruption_check_size(char *arg)
49 {
50 char *end;
51 unsigned size;
52
53 size = memparse(arg, &end);
54
55 if (*end == '\0')
56 corruption_check_size = size;
57
58 return (size == corruption_check_size) ? 0 : -EINVAL;
59 }
60 early_param("memory_corruption_check_size", set_corruption_check_size);
61
62
setup_bios_corruption_check(void)63 void __init setup_bios_corruption_check(void)
64 {
65 phys_addr_t start, end;
66 u64 i;
67
68 if (memory_corruption_check == -1) {
69 memory_corruption_check =
70 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
71 1
72 #else
73 0
74 #endif
75 ;
76 }
77
78 if (corruption_check_size == 0)
79 memory_corruption_check = 0;
80
81 if (!memory_corruption_check)
82 return;
83
84 corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
85
86 for_each_free_mem_range(i, MAX_NUMNODES, &start, &end, NULL) {
87 start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
88 PAGE_SIZE, corruption_check_size);
89 end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
90 PAGE_SIZE, corruption_check_size);
91 if (start >= end)
92 continue;
93
94 memblock_reserve(start, end - start);
95 scan_areas[num_scan_areas].addr = start;
96 scan_areas[num_scan_areas].size = end - start;
97
98 /* Assume we've already mapped this early memory */
99 memset(__va(start), 0, end - start);
100
101 if (++num_scan_areas >= MAX_SCAN_AREAS)
102 break;
103 }
104
105 if (num_scan_areas)
106 printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas);
107 }
108
109
check_for_bios_corruption(void)110 void check_for_bios_corruption(void)
111 {
112 int i;
113 int corruption = 0;
114
115 if (!memory_corruption_check)
116 return;
117
118 for (i = 0; i < num_scan_areas; i++) {
119 unsigned long *addr = __va(scan_areas[i].addr);
120 unsigned long size = scan_areas[i].size;
121
122 for (; size; addr++, size -= sizeof(unsigned long)) {
123 if (!*addr)
124 continue;
125 printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
126 addr, __pa(addr), *addr);
127 corruption = 1;
128 *addr = 0;
129 }
130 }
131
132 WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
133 }
134
135 static void check_corruption(struct work_struct *dummy);
136 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
137
check_corruption(struct work_struct * dummy)138 static void check_corruption(struct work_struct *dummy)
139 {
140 check_for_bios_corruption();
141 schedule_delayed_work(&bios_check_work,
142 round_jiffies_relative(corruption_check_period*HZ));
143 }
144
start_periodic_check_for_corruption(void)145 static int start_periodic_check_for_corruption(void)
146 {
147 if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
148 return 0;
149
150 printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
151 corruption_check_period);
152
153 /* First time we run the checks right away */
154 schedule_delayed_work(&bios_check_work, 0);
155 return 0;
156 }
157
158 module_init(start_periodic_check_for_corruption);
159
160