1 #include <linux/module.h> 2 #include <linux/sched.h> 3 4 #include <asm/e820.h> 5 #include <asm/proto.h> 6 7 /* 8 * Some BIOSes seem to corrupt the low 64k of memory during events 9 * like suspend/resume and unplugging an HDMI cable. Reserve all 10 * remaining free memory in that area and fill it with a distinct 11 * pattern. 12 */ 13 #ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION 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 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 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 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 == 0) 87 break; 88 89 if ((addr + size) > corruption_check_size) 90 size = corruption_check_size - addr; 91 92 if (size == 0) 93 break; 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 static struct timer_list periodic_check_timer; 112 113 void check_for_bios_corruption(void) 114 { 115 int i; 116 int corruption = 0; 117 118 if (!memory_corruption_check) 119 return; 120 121 for (i = 0; i < num_scan_areas; i++) { 122 unsigned long *addr = __va(scan_areas[i].addr); 123 unsigned long size = scan_areas[i].size; 124 125 for (; size; addr++, size -= sizeof(unsigned long)) { 126 if (!*addr) 127 continue; 128 printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n", 129 addr, __pa(addr), *addr); 130 corruption = 1; 131 *addr = 0; 132 } 133 } 134 135 WARN(corruption, KERN_ERR "Memory corruption detected in low memory\n"); 136 } 137 138 static void periodic_check_for_corruption(unsigned long data) 139 { 140 check_for_bios_corruption(); 141 mod_timer(&periodic_check_timer, 142 round_jiffies(jiffies + corruption_check_period*HZ)); 143 } 144 145 void start_periodic_check_for_corruption(void) 146 { 147 if (!memory_corruption_check || corruption_check_period == 0) 148 return; 149 150 printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n", 151 corruption_check_period); 152 153 init_timer(&periodic_check_timer); 154 periodic_check_timer.function = &periodic_check_for_corruption; 155 periodic_check_for_corruption(0); 156 } 157 #endif 158 159