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
17static int __read_mostly memory_corruption_check = -1;
18
19static unsigned __read_mostly corruption_check_size = 64*1024;
20static unsigned __read_mostly corruption_check_period = 60; /* seconds */
21
22static struct scan_area {
23	u64 addr;
24	u64 size;
25} scan_areas[MAX_SCAN_AREAS];
26static int num_scan_areas;
27
28static __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}
40early_param("memory_corruption_check", set_corruption_check);
41
42static __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}
54early_param("memory_corruption_check_period", set_corruption_check_period);
55
56static __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}
68early_param("memory_corruption_check_size", set_corruption_check_size);
69
70
71void __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
118void 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
143static void check_corruption(struct work_struct *dummy);
144static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
145
146static 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
153static 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
166module_init(start_periodic_check_for_corruption);
167
168