arch/x86/kernel/check.c

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