1// SPDX-License-Identifier: GPL-2.0
2
3#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
4
5#include <linux/init.h>
6#include <linux/sched.h>
7#include <linux/kthread.h>
8#include <linux/workqueue.h>
9#include <linux/memblock.h>
10
11#include <asm/proto.h>
12#include <asm/setup.h>
13
14/*
15 * Some BIOSes seem to corrupt the low 64k of memory during events
16 * like suspend/resume and unplugging an HDMI cable.  Reserve all
17 * remaining free memory in that area and fill it with a distinct
18 * pattern.
19 */
20#define MAX_SCAN_AREAS	8
21
22static int __read_mostly memory_corruption_check = -1;
23
24static unsigned __read_mostly corruption_check_size = 64*1024;
25static unsigned __read_mostly corruption_check_period = 60; /* seconds */
26
27static struct scan_area {
28	u64 addr;
29	u64 size;
30} scan_areas[MAX_SCAN_AREAS];
31static int num_scan_areas;
32
33static __init int set_corruption_check(char *arg)
34{
35	ssize_t ret;
36	unsigned long val;
37
38	if (!arg) {
39		pr_err("memory_corruption_check config string not provided\n");
40		return -EINVAL;
41	}
42
43	ret = kstrtoul(arg, 10, &val);
44	if (ret)
45		return ret;
46
47	memory_corruption_check = val;
48
49	return 0;
50}
51early_param("memory_corruption_check", set_corruption_check);
52
53static __init int set_corruption_check_period(char *arg)
54{
55	ssize_t ret;
56	unsigned long val;
57
58	if (!arg) {
59		pr_err("memory_corruption_check_period config string not provided\n");
60		return -EINVAL;
61	}
62
63	ret = kstrtoul(arg, 10, &val);
64	if (ret)
65		return ret;
66
67	corruption_check_period = val;
68	return 0;
69}
70early_param("memory_corruption_check_period", set_corruption_check_period);
71
72static __init int set_corruption_check_size(char *arg)
73{
74	char *end;
75	unsigned size;
76
77	if (!arg) {
78		pr_err("memory_corruption_check_size config string not provided\n");
79		return -EINVAL;
80	}
81
82	size = memparse(arg, &end);
83
84	if (*end == '\0')
85		corruption_check_size = size;
86
87	return (size == corruption_check_size) ? 0 : -EINVAL;
88}
89early_param("memory_corruption_check_size", set_corruption_check_size);
90
91
92void __init setup_bios_corruption_check(void)
93{
94	phys_addr_t start, end;
95	u64 i;
96
97	if (memory_corruption_check == -1) {
98		memory_corruption_check =
99#ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
100			1
101#else
102			0
103#endif
104			;
105	}
106
107	if (corruption_check_size == 0)
108		memory_corruption_check = 0;
109
110	if (!memory_corruption_check)
111		return;
112
113	corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
114
115	for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
116				NULL) {
117		start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
118				PAGE_SIZE, corruption_check_size);
119		end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
120			      PAGE_SIZE, corruption_check_size);
121		if (start >= end)
122			continue;
123
124		memblock_reserve(start, end - start);
125		scan_areas[num_scan_areas].addr = start;
126		scan_areas[num_scan_areas].size = end - start;
127
128		/* Assume we've already mapped this early memory */
129		memset(__va(start), 0, end - start);
130
131		if (++num_scan_areas >= MAX_SCAN_AREAS)
132			break;
133	}
134
135	if (num_scan_areas)
136		pr_info("Scanning %d areas for low memory corruption\n", num_scan_areas);
137}
138
139
140static void check_for_bios_corruption(void)
141{
142	int i;
143	int corruption = 0;
144
145	if (!memory_corruption_check)
146		return;
147
148	for (i = 0; i < num_scan_areas; i++) {
149		unsigned long *addr = __va(scan_areas[i].addr);
150		unsigned long size = scan_areas[i].size;
151
152		for (; size; addr++, size -= sizeof(unsigned long)) {
153			if (!*addr)
154				continue;
155			pr_err("Corrupted low memory at %p (%lx phys) = %08lx\n", addr, __pa(addr), *addr);
156			corruption = 1;
157			*addr = 0;
158		}
159	}
160
161	WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
162}
163
164static void check_corruption(struct work_struct *dummy);
165static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
166
167static void check_corruption(struct work_struct *dummy)
168{
169	check_for_bios_corruption();
170	schedule_delayed_work(&bios_check_work,
171		round_jiffies_relative(corruption_check_period*HZ));
172}
173
174static int start_periodic_check_for_corruption(void)
175{
176	if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
177		return 0;
178
179	pr_info("Scanning for low memory corruption every %d seconds\n", corruption_check_period);
180
181	/* First time we run the checks right away */
182	schedule_delayed_work(&bios_check_work, 0);
183
184	return 0;
185}
186device_initcall(start_periodic_check_for_corruption);
187
188