arch/x86/kernel/check.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/init.h>
   3 #include <linux/sched.h>
   4 #include <linux/kthread.h>
   5 #include <linux/workqueue.h>
   6 #include <linux/memblock.h>
   7
   8 #include <asm/proto.h>
   9
  10 /*
  11  * Some BIOSes seem to corrupt the low 64k of memory during events
  12  * like suspend/resume and unplugging an HDMI cable.  Reserve all
  13  * remaining free memory in that area and fill it with a distinct
  14  * pattern.
  15  */
  16 #define MAX_SCAN_AREAS  8
  17
  18 static int __read_mostly memory_corruption_check = -1;
  19
  20 static unsigned __read_mostly corruption_check_size = 64*1024;
  21 static unsigned __read_mostly corruption_check_period = 60; /* seconds */
  22
  23 static struct scan_area {
  24         u64 addr;
  25         u64 size;
  26 } scan_areas[MAX_SCAN_AREAS];
  27 static int num_scan_areas;
  28
  29 static __init int set_corruption_check(char *arg)
  30 {
  31         ssize_t ret;
  32         unsigned long val;
  33
  34         ret = kstrtoul(arg, 10, &val);
  35         if (ret)
  36                 return ret;
  37
  38         memory_corruption_check = val;
  39         return 0;
  40 }
  41 early_param("memory_corruption_check", set_corruption_check);
  42
  43 static __init int set_corruption_check_period(char *arg)
  44 {
  45         ssize_t ret;
  46         unsigned long val;
  47
  48         ret = kstrtoul(arg, 10, &val);
  49         if (ret)
  50                 return ret;
  51
  52         corruption_check_period = val;
  53         return 0;
  54 }
  55 early_param("memory_corruption_check_period", set_corruption_check_period);
  56
  57 static __init int set_corruption_check_size(char *arg)
  58 {
  59         char *end;
  60         unsigned size;
  61
  62         size = memparse(arg, &end);
  63
  64         if (*end == '\0')
  65                 corruption_check_size = size;
  66
  67         return (size == corruption_check_size) ? 0 : -EINVAL;
  68 }
  69 early_param("memory_corruption_check_size", set_corruption_check_size);
  70
  71
  72 void __init setup_bios_corruption_check(void)
  73 {
  74         phys_addr_t start, end;
  75         u64 i;
  76
  77         if (memory_corruption_check == -1) {
  78                 memory_corruption_check =
  79 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
  80                         1
  81 #else
  82                         0
  83 #endif
  84                         ;
  85         }
  86
  87         if (corruption_check_size == 0)
  88                 memory_corruption_check = 0;
  89
  90         if (!memory_corruption_check)
  91                 return;
  92
  93         corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
  94
  95         for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
  96                                 NULL) {
  97                 start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
  98                                 PAGE_SIZE, corruption_check_size);
  99                 end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
 100                               PAGE_SIZE, corruption_check_size);
 101                 if (start >= end)
 102                         continue;
 103
 104                 memblock_reserve(start, end - start);
 105                 scan_areas[num_scan_areas].addr = start;
 106                 scan_areas[num_scan_areas].size = end - start;
 107
 108                 /* Assume we've already mapped this early memory */
 109                 memset(__va(start), 0, end - start);
 110
 111                 if (++num_scan_areas >= MAX_SCAN_AREAS)
 112                         break;
 113         }
 114
 115         if (num_scan_areas)
 116                 printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas);
 117 }
 118
 119
 120 void check_for_bios_corruption(void)
 121 {
 122         int i;
 123         int corruption = 0;
 124
 125         if (!memory_corruption_check)
 126                 return;
 127
 128         for (i = 0; i < num_scan_areas; i++) {
 129                 unsigned long *addr = __va(scan_areas[i].addr);
 130                 unsigned long size = scan_areas[i].size;
 131
 132                 for (; size; addr++, size -= sizeof(unsigned long)) {
 133                         if (!*addr)
 134                                 continue;
 135                         printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
 136                                addr, __pa(addr), *addr);
 137                         corruption = 1;
 138                         *addr = 0;
 139                 }
 140         }
 141
 142         WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
 143 }
 144
 145 static void check_corruption(struct work_struct *dummy);
 146 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
 147
 148 static void check_corruption(struct work_struct *dummy)
 149 {
 150         check_for_bios_corruption();
 151         schedule_delayed_work(&bios_check_work,
 152                 round_jiffies_relative(corruption_check_period*HZ));
 153 }
 154
 155 static int start_periodic_check_for_corruption(void)
 156 {
 157         if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
 158                 return 0;
 159
 160         printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
 161                corruption_check_period);
 162
 163         /* First time we run the checks right away */
 164         schedule_delayed_work(&bios_check_work, 0);
 165         return 0;
 166 }
 167 device_initcall(start_periodic_check_for_corruption);
 168