1#include <linux/init.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, MEMBLOCK_NONE, &start, &end,
95				NULL) {
96		start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
97				PAGE_SIZE, corruption_check_size);
98		end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
99			      PAGE_SIZE, corruption_check_size);
100		if (start >= end)
101			continue;
102
103		memblock_reserve(start, end - start);
104		scan_areas[num_scan_areas].addr = start;
105		scan_areas[num_scan_areas].size = end - start;
106
107		/* Assume we've already mapped this early memory */
108		memset(__va(start), 0, end - start);
109
110		if (++num_scan_areas >= MAX_SCAN_AREAS)
111			break;
112	}
113
114	if (num_scan_areas)
115		printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas);
116}
117
118
119void check_for_bios_corruption(void)
120{
121	int i;
122	int corruption = 0;
123
124	if (!memory_corruption_check)
125		return;
126
127	for (i = 0; i < num_scan_areas; i++) {
128		unsigned long *addr = __va(scan_areas[i].addr);
129		unsigned long size = scan_areas[i].size;
130
131		for (; size; addr++, size -= sizeof(unsigned long)) {
132			if (!*addr)
133				continue;
134			printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
135			       addr, __pa(addr), *addr);
136			corruption = 1;
137			*addr = 0;
138		}
139	}
140
141	WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
142}
143
144static void check_corruption(struct work_struct *dummy);
145static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
146
147static void check_corruption(struct work_struct *dummy)
148{
149	check_for_bios_corruption();
150	schedule_delayed_work(&bios_check_work,
151		round_jiffies_relative(corruption_check_period*HZ));
152}
153
154static int start_periodic_check_for_corruption(void)
155{
156	if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
157		return 0;
158
159	printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
160	       corruption_check_period);
161
162	/* First time we run the checks right away */
163	schedule_delayed_work(&bios_check_work, 0);
164	return 0;
165}
166device_initcall(start_periodic_check_for_corruption);
167
168