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); 163 164