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 <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
  17 static int __read_mostly memory_corruption_check = -1;
  18
  19 static unsigned __read_mostly corruption_check_size = 64*1024;
  20 static unsigned __read_mostly corruption_check_period = 60; /* seconds */
  21
  22 static struct scan_area {
  23         u64 addr;
  24         u64 size;
  25 } scan_areas[MAX_SCAN_AREAS];
  26 static int num_scan_areas;
  27
  28 static __init int set_corruption_check(char *arg)
  29 {
  30         char *end;
  31
  32         memory_corruption_check = simple_strtol(arg, &end, 10);
  33
  34         return (*end == 0) ? 0 : -EINVAL;
  35 }
  36 early_param("memory_corruption_check", set_corruption_check);
  37
  38 static __init int set_corruption_check_period(char *arg)
  39 {
  40         char *end;
  41
  42         corruption_check_period = simple_strtoul(arg, &end, 10);
  43
  44         return (*end == 0) ? 0 : -EINVAL;
  45 }
  46 early_param("memory_corruption_check_period", set_corruption_check_period);
  47
  48 static __init int set_corruption_check_size(char *arg)
  49 {
  50         char *end;
  51         unsigned size;
  52
  53         size = memparse(arg, &end);
  54
  55         if (*end == '\0')
  56                 corruption_check_size = size;
  57
  58         return (size == corruption_check_size) ? 0 : -EINVAL;
  59 }
  60 early_param("memory_corruption_check_size", set_corruption_check_size);
  61
  62
  63 void __init setup_bios_corruption_check(void)
  64 {
  65         u64 addr = PAGE_SIZE;   /* assume first page is reserved anyway */
  66
  67         if (memory_corruption_check == -1) {
  68                 memory_corruption_check =
  69 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
  70                         1
  71 #else
  72                         0
  73 #endif
  74                         ;
  75         }
  76
  77         if (corruption_check_size == 0)
  78                 memory_corruption_check = 0;
  79
  80         if (!memory_corruption_check)
  81                 return;
  82
  83         corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
  84
  85         while (addr < corruption_check_size && num_scan_areas < MAX_SCAN_AREAS) {
  86                 u64 size;
  87                 addr = memblock_x86_find_in_range_size(addr, &size, PAGE_SIZE);
  88
  89                 if (addr == MEMBLOCK_ERROR)
  90                         break;
  91
  92                 if (addr >= corruption_check_size)
  93                         break;
  94
  95                 if ((addr + size) > corruption_check_size)
  96                         size = corruption_check_size - addr;
  97
  98                 memblock_x86_reserve_range(addr, addr + size, "SCAN RAM");
  99                 scan_areas[num_scan_areas].addr = addr;
 100                 scan_areas[num_scan_areas].size = size;
 101                 num_scan_areas++;
 102
 103                 /* Assume we've already mapped this early memory */
 104                 memset(__va(addr), 0, size);
 105
 106                 addr += size;
 107         }
 108
 109         if (num_scan_areas)
 110                 printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas);
 111 }
 112
 113
 114 void check_for_bios_corruption(void)
 115 {
 116         int i;
 117         int corruption = 0;
 118
 119         if (!memory_corruption_check)
 120                 return;
 121
 122         for (i = 0; i < num_scan_areas; i++) {
 123                 unsigned long *addr = __va(scan_areas[i].addr);
 124                 unsigned long size = scan_areas[i].size;
 125
 126                 for (; size; addr++, size -= sizeof(unsigned long)) {
 127                         if (!*addr)
 128                                 continue;
 129                         printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
 130                                addr, __pa(addr), *addr);
 131                         corruption = 1;
 132                         *addr = 0;
 133                 }
 134         }
 135
 136         WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
 137 }
 138
 139 static void check_corruption(struct work_struct *dummy);
 140 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
 141
 142 static void check_corruption(struct work_struct *dummy)
 143 {
 144         check_for_bios_corruption();
 145         schedule_delayed_work(&bios_check_work,
 146                 round_jiffies_relative(corruption_check_period*HZ));
 147 }
 148
 149 static int start_periodic_check_for_corruption(void)
 150 {
 151         if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
 152                 return 0;
 153
 154         printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
 155                corruption_check_period);
 156
 157         /* First time we run the checks right away */
 158         schedule_delayed_work(&bios_check_work, 0);
 159         return 0;
 160 }
 161
 162 module_init(start_periodic_check_for_corruption);
 163