v4.19.13 snapshot.
diff --git a/arch/x86/kernel/check.c b/arch/x86/kernel/check.c
new file mode 100644
index 0000000..cc8258a
--- /dev/null
+++ b/arch/x86/kernel/check.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/kthread.h>
+#include <linux/workqueue.h>
+#include <linux/memblock.h>
+
+#include <asm/proto.h>
+
+/*
+ * Some BIOSes seem to corrupt the low 64k of memory during events
+ * like suspend/resume and unplugging an HDMI cable. Reserve all
+ * remaining free memory in that area and fill it with a distinct
+ * pattern.
+ */
+#define MAX_SCAN_AREAS 8
+
+static int __read_mostly memory_corruption_check = -1;
+
+static unsigned __read_mostly corruption_check_size = 64*1024;
+static unsigned __read_mostly corruption_check_period = 60; /* seconds */
+
+static struct scan_area {
+ u64 addr;
+ u64 size;
+} scan_areas[MAX_SCAN_AREAS];
+static int num_scan_areas;
+
+static __init int set_corruption_check(char *arg)
+{
+ ssize_t ret;
+ unsigned long val;
+
+ if (!arg) {
+ pr_err("memory_corruption_check config string not provided\n");
+ return -EINVAL;
+ }
+
+ ret = kstrtoul(arg, 10, &val);
+ if (ret)
+ return ret;
+
+ memory_corruption_check = val;
+ return 0;
+}
+early_param("memory_corruption_check", set_corruption_check);
+
+static __init int set_corruption_check_period(char *arg)
+{
+ ssize_t ret;
+ unsigned long val;
+
+ if (!arg) {
+ pr_err("memory_corruption_check_period config string not provided\n");
+ return -EINVAL;
+ }
+
+ ret = kstrtoul(arg, 10, &val);
+ if (ret)
+ return ret;
+
+ corruption_check_period = val;
+ return 0;
+}
+early_param("memory_corruption_check_period", set_corruption_check_period);
+
+static __init int set_corruption_check_size(char *arg)
+{
+ char *end;
+ unsigned size;
+
+ if (!arg) {
+ pr_err("memory_corruption_check_size config string not provided\n");
+ return -EINVAL;
+ }
+
+ size = memparse(arg, &end);
+
+ if (*end == '\0')
+ corruption_check_size = size;
+
+ return (size == corruption_check_size) ? 0 : -EINVAL;
+}
+early_param("memory_corruption_check_size", set_corruption_check_size);
+
+
+void __init setup_bios_corruption_check(void)
+{
+ phys_addr_t start, end;
+ u64 i;
+
+ if (memory_corruption_check == -1) {
+ memory_corruption_check =
+#ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
+ 1
+#else
+ 0
+#endif
+ ;
+ }
+
+ if (corruption_check_size == 0)
+ memory_corruption_check = 0;
+
+ if (!memory_corruption_check)
+ return;
+
+ corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
+
+ for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
+ NULL) {
+ start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE),
+ PAGE_SIZE, corruption_check_size);
+ end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE),
+ PAGE_SIZE, corruption_check_size);
+ if (start >= end)
+ continue;
+
+ memblock_reserve(start, end - start);
+ scan_areas[num_scan_areas].addr = start;
+ scan_areas[num_scan_areas].size = end - start;
+
+ /* Assume we've already mapped this early memory */
+ memset(__va(start), 0, end - start);
+
+ if (++num_scan_areas >= MAX_SCAN_AREAS)
+ break;
+ }
+
+ if (num_scan_areas)
+ printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas);
+}
+
+
+void check_for_bios_corruption(void)
+{
+ int i;
+ int corruption = 0;
+
+ if (!memory_corruption_check)
+ return;
+
+ for (i = 0; i < num_scan_areas; i++) {
+ unsigned long *addr = __va(scan_areas[i].addr);
+ unsigned long size = scan_areas[i].size;
+
+ for (; size; addr++, size -= sizeof(unsigned long)) {
+ if (!*addr)
+ continue;
+ printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
+ addr, __pa(addr), *addr);
+ corruption = 1;
+ *addr = 0;
+ }
+ }
+
+ WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
+}
+
+static void check_corruption(struct work_struct *dummy);
+static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
+
+static void check_corruption(struct work_struct *dummy)
+{
+ check_for_bios_corruption();
+ schedule_delayed_work(&bios_check_work,
+ round_jiffies_relative(corruption_check_period*HZ));
+}
+
+static int start_periodic_check_for_corruption(void)
+{
+ if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0)
+ return 0;
+
+ printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
+ corruption_check_period);
+
+ /* First time we run the checks right away */
+ schedule_delayed_work(&bios_check_work, 0);
+ return 0;
+}
+device_initcall(start_periodic_check_for_corruption);
+