HWPOISON: Add simple debugfs interface to inject hwpoison on arbitary PFNs

Useful for some testing scenarios, although specific testing is often
done better through MADV_POISON

This can be done with the x86 level MCE injector too, but this interface
allows it to do independently from low level x86 changes.

v2: Add module license (Haicheng Li)
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

mm/Kconfig

@@ -243,6 +243,10 @@ config MEMORY_FAILURE
 	  even when some of its memory has uncorrected errors. This requires
 	  special hardware support and typically ECC memory.
 
+config HWPOISON_INJECT
+	tristate "Poison pages injector"
+	depends on MEMORY_FAILURE && DEBUG_KERNEL
+
 config NOMMU_INITIAL_TRIM_EXCESS
 	int "Turn on mmap() excess space trimming before booting"
 	depends on !MMU

mm/Makefile

@@ -41,5 +41,6 @@ endif
 obj-$(CONFIG_QUICKLIST) += quicklist.o
 obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
 obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
+obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o
 obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
 obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o

mm/hwpoison-inject.c

+/* Inject a hwpoison memory failure on a arbitary pfn */
+#include <linux/module.h>
+#include <linux/debugfs.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+
+static struct dentry *hwpoison_dir, *corrupt_pfn;
+
+static int hwpoison_inject(void *data, u64 val)
+{
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	printk(KERN_INFO "Injecting memory failure at pfn %Lx\n", val);
+	return __memory_failure(val, 18, 0);
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(hwpoison_fops, NULL, hwpoison_inject, "%lli\n");
+
+static void pfn_inject_exit(void)
+{
+	if (hwpoison_dir)
+		debugfs_remove_recursive(hwpoison_dir);
+}
+
+static int pfn_inject_init(void)
+{
+	hwpoison_dir = debugfs_create_dir("hwpoison", NULL);
+	if (hwpoison_dir == NULL)
+		return -ENOMEM;
+	corrupt_pfn = debugfs_create_file("corrupt-pfn", 0600, hwpoison_dir,
+					  NULL, &hwpoison_fops);
+	if (corrupt_pfn == NULL) {
+		pfn_inject_exit();
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+module_init(pfn_inject_init);
+module_exit(pfn_inject_exit);
+MODULE_LICENSE("GPL");