arch/x86/kernel/check.c

   1 #include <linux/module.h>
   2 #include <linux/sched.h>
   3 #include <linux/kthread.h>
   4 #include <linux/workqueue.h>
   5 #include <asm/e820.h>
   6 #include <asm/proto.h>
   7
   8 /*
   9  * Some BIOSes seem to corrupt the low 64k of memory during events
  10  * like suspend/resume and unplugging an HDMI cable.  Reserve all
  11  * remaining free memory in that area and fill it with a distinct
  12  * pattern.
  13  */
  14 #define MAX_SCAN_AREAS  8
  15
  16 static int __read_mostly memory_corruption_check = -1;
  17
  18 static unsigned __read_mostly corruption_check_size = 64*1024;
  19 static unsigned __read_mostly corruption_check_period = 60; /* seconds */
  20
  21 static struct e820entry scan_areas[MAX_SCAN_AREAS];
  22 static int num_scan_areas;
  23
  24
  25 static __init int set_corruption_check(char *arg)
  26 {
  27         char *end;
  28
  29         memory_corruption_check = simple_strtol(arg, &end, 10);
  30
  31         return (*end == 0) ? 0 : -EINVAL;
  32 }
  33 early_param("memory_corruption_check", set_corruption_check);
  34
  35 static __init int set_corruption_check_period(char *arg)
  36 {
  37         char *end;
  38
  39         corruption_check_period = simple_strtoul(arg, &end, 10);
  40
  41         return (*end == 0) ? 0 : -EINVAL;
  42 }
  43 early_param("memory_corruption_check_period", set_corruption_check_period);
  44
  45 static __init int set_corruption_check_size(char *arg)
  46 {
  47         char *end;
  48         unsigned size;
  49
  50         size = memparse(arg, &end);
  51
  52         if (*end == '\0')
  53                 corruption_check_size = size;
  54
  55         return (size == corruption_check_size) ? 0 : -EINVAL;
  56 }
  57 early_param("memory_corruption_check_size", set_corruption_check_size);
  58
  59
  60 void __init setup_bios_corruption_check(void)
  61 {
  62         u64 addr = PAGE_SIZE;   /* assume first page is reserved anyway */
  63
  64         if (memory_corruption_check == -1) {
  65                 memory_corruption_check =
  66 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
  67                         1
  68 #else
  69                         0
  70 #endif
  71                         ;
  72         }
  73
  74         if (corruption_check_size == 0)
  75                 memory_corruption_check = 0;
  76
  77         if (!memory_corruption_check)
  78                 return;
  79
  80         corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
  81
  82         while (addr < corruption_check_size && num_scan_areas < MAX_SCAN_AREAS) {
  83                 u64 size;
  84                 addr = find_e820_area_size(addr, &size, PAGE_SIZE);
  85
  86                 if (!(addr + 1))
  87                         break;
  88
  89                 if (addr >= corruption_check_size)
  90                         break;
  91
  92                 if ((addr + size) > corruption_check_size)
  93                         size = corruption_check_size - addr;
  94
  95                 e820_update_range(addr, size, E820_RAM, E820_RESERVED);
  96                 scan_areas[num_scan_areas].addr = addr;
  97                 scan_areas[num_scan_areas].size = size;
  98                 num_scan_areas++;
  99
 100                 /* Assume we've already mapped this early memory */
 101                 memset(__va(addr), 0, size);
 102
 103                 addr += size;
 104         }
 105
 106         printk(KERN_INFO "Scanning %d areas for low memory corruption\n",
 107                num_scan_areas);
 108         update_e820();
 109 }
 110
 111
 112 void check_for_bios_corruption(void)
 113 {
 114         int i;
 115         int corruption = 0;
 116
 117         if (!memory_corruption_check)
 118                 return;
 119
 120         for (i = 0; i < num_scan_areas; i++) {
 121                 unsigned long *addr = __va(scan_areas[i].addr);
 122                 unsigned long size = scan_areas[i].size;
 123
 124                 for (; size; addr++, size -= sizeof(unsigned long)) {
 125                         if (!*addr)
 126                                 continue;
 127                         printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
 128                                addr, __pa(addr), *addr);
 129                         corruption = 1;
 130                         *addr = 0;
 131                 }
 132         }
 133
 134         WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
 135 }
 136
 137 static void check_corruption(struct work_struct *dummy);
 138 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
 139
 140 static void check_corruption(struct work_struct *dummy)
 141 {
 142         check_for_bios_corruption();
 143         schedule_delayed_work(&bios_check_work,
 144                 round_jiffies_relative(corruption_check_period*HZ));
 145 }
 146
 147 static int start_periodic_check_for_corruption(void)
 148 {
 149         if (!memory_corruption_check || corruption_check_period == 0)
 150                 return 0;
 151
 152         printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
 153                corruption_check_period);
 154
 155         /* First time we run the checks right away */
 156         schedule_delayed_work(&bios_check_work, 0);
 157         return 0;
 158 }
 159
 160 module_init(start_periodic_check_for_corruption);
 161