x86/kernel/check.c

0001 // SPDX-License-Identifier: GPL-2.0
0002
0003 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0004
0005 #include <linux/init.h>
0006 #include <linux/sched.h>
0007 #include <linux/kthread.h>
0008 #include <linux/workqueue.h>
0009 #include <linux/memblock.h>
0010
0011 #include <asm/proto.h>
0012 #include <asm/setup.h>
0013
0014 /*
0015  * Some BIOSes seem to corrupt the low 64k of memory during events
0016  * like suspend/resume and unplugging an HDMI cable.  Reserve all
0017  * remaining free memory in that area and fill it with a distinct
0018  * pattern.
0019  */
0020 #define MAX_SCAN_AREAS  8
0021
0022 static int __read_mostly memory_corruption_check = -1;
0023
0024 static unsigned __read_mostly corruption_check_size = 64*1024;
0025 static unsigned __read_mostly corruption_check_period = 60; /* seconds */
0026
0027 static struct scan_area {
0028     u64 addr;
0029     u64 size;
0030 } scan_areas[MAX_SCAN_AREAS];
0031 static int num_scan_areas;
0032
0033 static __init int set_corruption_check(char *arg)
0034 {
0035     ssize_t ret;
0036     unsigned long val;
0037
0038     if (!arg) {
0039         pr_err("memory_corruption_check config string not provided\n");
0040         return -EINVAL;
0041     }
0042
0043     ret = kstrtoul(arg, 10, &val);
0044     if (ret)
0045         return ret;
0046
0047     memory_corruption_check = val;
0048
0049     return 0;
0050 }
0051 early_param("memory_corruption_check", set_corruption_check);
0052
0053 static __init int set_corruption_check_period(char *arg)
0054 {
0055     ssize_t ret;
0056     unsigned long val;
0057
0058     if (!arg) {
0059         pr_err("memory_corruption_check_period config string not provided\n");
0060         return -EINVAL;
0061     }
0062
0063     ret = kstrtoul(arg, 10, &val);
0064     if (ret)
0065         return ret;
0066
0067     corruption_check_period = val;
0068     return 0;
0069 }
0070 early_param("memory_corruption_check_period", set_corruption_check_period);
0071
0072 static __init int set_corruption_check_size(char *arg)
0073 {
0074     char *end;
0075     unsigned size;
0076
0077     if (!arg) {
0078         pr_err("memory_corruption_check_size config string not provided\n");
0079         return -EINVAL;
0080     }
0081
0082     size = memparse(arg, &end);
0083
0084     if (*end == '\0')
0085         corruption_check_size = size;
0086
0087     return (size == corruption_check_size) ? 0 : -EINVAL;
0088 }
0089 early_param("memory_corruption_check_size", set_corruption_check_size);
0090
0091
0092 void __init setup_bios_corruption_check(void)
0093 {
0094     phys_addr_t start, end;
0095     u64 i;
0096
0097     if (memory_corruption_check == -1) {
0098         memory_corruption_check =
0099 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
0100             1
0101 #else
0102             0
0103 #endif
0104             ;
0105     }
0106
0107     if (corruption_check_size == 0)
0108         memory_corruption_check = 0;
0109
0110     if (!memory_corruption_check)
0111         return;
0112
0113     corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
0114
0115     for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
0116                 NULL) {
0117         start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
0118                 PAGE_SIZE, corruption_check_size);
0119         end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
0120                   PAGE_SIZE, corruption_check_size);
0121         if (start >= end)
0122             continue;
0123
0124         memblock_reserve(start, end - start);
0125         scan_areas[num_scan_areas].addr = start;
0126         scan_areas[num_scan_areas].size = end - start;
0127
0128         /* Assume we've already mapped this early memory */
0129         memset(__va(start), 0, end - start);
0130
0131         if (++num_scan_areas >= MAX_SCAN_AREAS)
0132             break;
0133     }
0134
0135     if (num_scan_areas)
0136         pr_info("Scanning %d areas for low memory corruption\n", num_scan_areas);
0137 }
0138
0139
0140 static void check_for_bios_corruption(void)
0141 {
0142     int i;
0143     int corruption = 0;
0144
0145     if (!memory_corruption_check)
0146         return;
0147
0148     for (i = 0; i < num_scan_areas; i++) {
0149         unsigned long *addr = __va(scan_areas[i].addr);
0150         unsigned long size = scan_areas[i].size;
0151
0152         for (; size; addr++, size -= sizeof(unsigned long)) {
0153             if (!*addr)
0154                 continue;
0155             pr_err("Corrupted low memory at %p (%lx phys) = %08lx\n", addr, __pa(addr), *addr);
0156             corruption = 1;
0157             *addr = 0;
0158         }
0159     }
0160
0161     WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
0162 }
0163
0164 static void check_corruption(struct work_struct *dummy);
0165 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
0166
0167 static void check_corruption(struct work_struct *dummy)
0168 {
0169     check_for_bios_corruption();
0170     schedule_delayed_work(&bios_check_work,
0171         round_jiffies_relative(corruption_check_period*HZ));
0172 }
0173
0174 static int start_periodic_check_for_corruption(void)
0175 {
0176     if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
0177         return 0;
0178
0179     pr_info("Scanning for low memory corruption every %d seconds\n", corruption_check_period);
0180
0181     /* First time we run the checks right away */
0182     schedule_delayed_work(&bios_check_work, 0);
0183
0184     return 0;
0185 }
0186 device_initcall(start_periodic_check_for_corruption);
0187