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 phys_addr_t start, end; 66 u64 i; 67 68 if (memory_corruption_check == -1) { 69 memory_corruption_check = 70 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK 71 1 72 #else 73 0 74 #endif 75 ; 76 } 77 78 if (corruption_check_size == 0) 79 memory_corruption_check = 0; 80 81 if (!memory_corruption_check) 82 return; 83 84 corruption_check_size = round_up(corruption_check_size, PAGE_SIZE); 85 86 for_each_free_mem_range(i, MAX_NUMNODES, &start, &end, NULL) { 87 start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE), 88 PAGE_SIZE, corruption_check_size); 89 end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE), 90 PAGE_SIZE, corruption_check_size); 91 if (start >= end) 92 continue; 93 94 memblock_reserve(start, end - start); 95 scan_areas[num_scan_areas].addr = start; 96 scan_areas[num_scan_areas].size = end - start; 97 98 /* Assume we've already mapped this early memory */ 99 memset(__va(start), 0, end - start); 100 101 if (++num_scan_areas >= MAX_SCAN_AREAS) 102 break; 103 } 104 105 if (num_scan_areas) 106 printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas); 107 } 108 109 110 void check_for_bios_corruption(void) 111 { 112 int i; 113 int corruption = 0; 114 115 if (!memory_corruption_check) 116 return; 117 118 for (i = 0; i < num_scan_areas; i++) { 119 unsigned long *addr = __va(scan_areas[i].addr); 120 unsigned long size = scan_areas[i].size; 121 122 for (; size; addr++, size -= sizeof(unsigned long)) { 123 if (!*addr) 124 continue; 125 printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n", 126 addr, __pa(addr), *addr); 127 corruption = 1; 128 *addr = 0; 129 } 130 } 131 132 WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n"); 133 } 134 135 static void check_corruption(struct work_struct *dummy); 136 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption); 137 138 static void check_corruption(struct work_struct *dummy) 139 { 140 check_for_bios_corruption(); 141 schedule_delayed_work(&bios_check_work, 142 round_jiffies_relative(corruption_check_period*HZ)); 143 } 144 145 static int start_periodic_check_for_corruption(void) 146 { 147 if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0) 148 return 0; 149 150 printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n", 151 corruption_check_period); 152 153 /* First time we run the checks right away */ 154 schedule_delayed_work(&bios_check_work, 0); 155 return 0; 156 } 157 158 module_init(start_periodic_check_for_corruption); 159 160