// SPDX-License-Identifier: GPL-2.0 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/init.h>#include <linux/sched.h>#include <linux/kthread.h>#include <linux/workqueue.h>#include <linux/memblock.h> #include <asm/proto.h>#include <asm/setup.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)		pr_info("Scanning %d areas for low memory corruption\n", num_scan_areas);}  static 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;			pr_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; 	pr_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);