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Linux/arch/x86/kernel/check.c

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  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         ssize_t ret;
 31         unsigned long val;
 32 
 33         ret = kstrtoul(arg, 10, &val);
 34         if (ret)
 35                 return ret;
 36 
 37         memory_corruption_check = val;
 38         return 0;
 39 }
 40 early_param("memory_corruption_check", set_corruption_check);
 41 
 42 static __init int set_corruption_check_period(char *arg)
 43 {
 44         ssize_t ret;
 45         unsigned long val;
 46 
 47         ret = kstrtoul(arg, 10, &val);
 48         if (ret)
 49                 return ret;
 50 
 51         corruption_check_period = val;
 52         return 0;
 53 }
 54 early_param("memory_corruption_check_period", set_corruption_check_period);
 55 
 56 static __init int set_corruption_check_size(char *arg)
 57 {
 58         char *end;
 59         unsigned size;
 60 
 61         size = memparse(arg, &end);
 62 
 63         if (*end == '\0')
 64                 corruption_check_size = size;
 65 
 66         return (size == corruption_check_size) ? 0 : -EINVAL;
 67 }
 68 early_param("memory_corruption_check_size", set_corruption_check_size);
 69 
 70 
 71 void __init setup_bios_corruption_check(void)
 72 {
 73         phys_addr_t start, end;
 74         u64 i;
 75 
 76         if (memory_corruption_check == -1) {
 77                 memory_corruption_check =
 78 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
 79                         1
 80 #else
 81                         0
 82 #endif
 83                         ;
 84         }
 85 
 86         if (corruption_check_size == 0)
 87                 memory_corruption_check = 0;
 88 
 89         if (!memory_corruption_check)
 90                 return;
 91 
 92         corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
 93 
 94         for_each_free_mem_range(i, NUMA_NO_NODE, &start, &end, NULL) {
 95                 start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
 96                                 PAGE_SIZE, corruption_check_size);
 97                 end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
 98                               PAGE_SIZE, corruption_check_size);
 99                 if (start >= end)
100                         continue;
101 
102                 memblock_reserve(start, end - start);
103                 scan_areas[num_scan_areas].addr = start;
104                 scan_areas[num_scan_areas].size = end - start;
105 
106                 /* Assume we've already mapped this early memory */
107                 memset(__va(start), 0, end - start);
108 
109                 if (++num_scan_areas >= MAX_SCAN_AREAS)
110                         break;
111         }
112 
113         if (num_scan_areas)
114                 printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas);
115 }
116 
117 
118 void check_for_bios_corruption(void)
119 {
120         int i;
121         int corruption = 0;
122 
123         if (!memory_corruption_check)
124                 return;
125 
126         for (i = 0; i < num_scan_areas; i++) {
127                 unsigned long *addr = __va(scan_areas[i].addr);
128                 unsigned long size = scan_areas[i].size;
129 
130                 for (; size; addr++, size -= sizeof(unsigned long)) {
131                         if (!*addr)
132                                 continue;
133                         printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
134                                addr, __pa(addr), *addr);
135                         corruption = 1;
136                         *addr = 0;
137                 }
138         }
139 
140         WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
141 }
142 
143 static void check_corruption(struct work_struct *dummy);
144 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
145 
146 static void check_corruption(struct work_struct *dummy)
147 {
148         check_for_bios_corruption();
149         schedule_delayed_work(&bios_check_work,
150                 round_jiffies_relative(corruption_check_period*HZ));
151 }
152 
153 static int start_periodic_check_for_corruption(void)
154 {
155         if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
156                 return 0;
157 
158         printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
159                corruption_check_period);
160 
161         /* First time we run the checks right away */
162         schedule_delayed_work(&bios_check_work, 0);
163         return 0;
164 }
165 
166 module_init(start_periodic_check_for_corruption);
167 
168 

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