error-injection: Separate error-injection from kprobe

Since error-injection framework is not limited to be used
by kprobes, nor bpf. Other kernel subsystems can use it
freely for checking safeness of error-injection, e.g.
livepatch, ftrace etc.
So this separate error-injection framework from kprobes.

Some differences has been made:

- "kprobe" word is removed from any APIs/structures.
- BPF_ALLOW_ERROR_INJECTION() is renamed to
  ALLOW_ERROR_INJECTION() since it is not limited for BPF too.
- CONFIG_FUNCTION_ERROR_INJECTION is the config item of this
  feature. It is automatically enabled if the arch supports
  error injection feature for kprobe or ftrace etc.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

arch/Kconfig

@@ -196,7 +196,7 @@ config HAVE_OPTPROBES
 config HAVE_KPROBES_ON_FTRACE
 	bool
 
-config HAVE_KPROBE_OVERRIDE
+config HAVE_FUNCTION_ERROR_INJECTION
 	bool
 
 config HAVE_NMI

arch/x86/Kconfig

@@ -154,7 +154,7 @@ config X86
 	select HAVE_KERNEL_XZ
 	select HAVE_KPROBES
 	select HAVE_KPROBES_ON_FTRACE
-	select HAVE_KPROBE_OVERRIDE
+	select HAVE_FUNCTION_ERROR_INJECTION
 	select HAVE_KRETPROBES
 	select HAVE_KVM
 	select HAVE_LIVEPATCH			if X86_64

arch/x86/include/asm/error-injection.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ERROR_INJECTION_H
+#define _ASM_ERROR_INJECTION_H
+
+#include <linux/compiler.h>
+#include <linux/linkage.h>
+#include <asm/ptrace.h>
+#include <asm-generic/error-injection.h>
+
+asmlinkage void just_return_func(void);
+void override_function_with_return(struct pt_regs *regs);
+
+#endif /* _ASM_ERROR_INJECTION_H */

arch/x86/kernel/kprobes/core.c

@@ -1183,17 +1183,3 @@ int arch_trampoline_kprobe(struct kprobe *p)
 {
 	return 0;
 }
-
-asmlinkage void override_func(void);
-asm(
-	".type override_func, @function\n"
-	"override_func:\n"
-	"	ret\n"
-	".size override_func, .-override_func\n"
-);
-
-void arch_kprobe_override_function(struct pt_regs *regs)
-{
-	regs->ip = (unsigned long)&override_func;
-}
-NOKPROBE_SYMBOL(arch_kprobe_override_function);

arch/x86/lib/Makefile

@@ -26,6 +26,7 @@ lib-y += memcpy_$(BITS).o
 lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
 lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o insn-eval.o
 lib-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
+lib-$(CONFIG_FUNCTION_ERROR_INJECTION)	+= error-inject.o
 
 obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o
 

arch/x86/lib/error-inject.c

+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/error-injection.h>
+#include <linux/kprobes.h>
+
+asmlinkage void just_return_func(void);
+
+asm(
+	".type just_return_func, @function\n"
+	"just_return_func:\n"
+	"	ret\n"
+	".size just_return_func, .-just_return_func\n"
+);
+
+void override_function_with_return(struct pt_regs *regs)
+{
+	regs->ip = (unsigned long)&just_return_func;
+}
+NOKPROBE_SYMBOL(override_function_with_return);

fs/btrfs/disk-io.c

@@ -30,7 +30,7 @@
 #include <linux/ratelimit.h>
 #include <linux/uuid.h>
 #include <linux/semaphore.h>
-#include <linux/bpf.h>
+#include <linux/error-injection.h>
 #include <asm/unaligned.h>
 #include "ctree.h"
 #include "disk-io.h"
@@ -3124,7 +3124,7 @@ int open_ctree(struct super_block *sb,
 		goto fail_block_groups;
 	goto retry_root_backup;
 }
-BPF_ALLOW_ERROR_INJECTION(open_ctree);
+ALLOW_ERROR_INJECTION(open_ctree);
 
 static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
 {

fs/btrfs/free-space-cache.c

@@ -22,7 +22,7 @@
 #include <linux/slab.h>
 #include <linux/math64.h>
 #include <linux/ratelimit.h>
-#include <linux/bpf.h>
+#include <linux/error-injection.h>
 #include "ctree.h"
 #include "free-space-cache.h"
 #include "transaction.h"
@@ -333,7 +333,7 @@ static int io_ctl_init(struct btrfs_io_ctl *io_ctl, struct inode *inode,
 
 	return 0;
 }
-BPF_ALLOW_ERROR_INJECTION(io_ctl_init);
+ALLOW_ERROR_INJECTION(io_ctl_init);
 
 static void io_ctl_free(struct btrfs_io_ctl *io_ctl)
 {

include/asm-generic/error-injection.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_ERROR_INJECTION_H
+#define _ASM_GENERIC_ERROR_INJECTION_H
+
+#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
+#ifdef CONFIG_FUNCTION_ERROR_INJECTION
+/*
+ * Whitelist ganerating macro. Specify functions which can be
+ * error-injectable using this macro.
+ */
+#define ALLOW_ERROR_INJECTION(fname)					\
+static unsigned long __used						\
+	__attribute__((__section__("_error_injection_whitelist")))	\
+	_eil_addr_##fname = (unsigned long)fname;
+#else
+#define ALLOW_ERROR_INJECTION(fname)
+#endif
+#endif
+
+#endif /* _ASM_GENERIC_ERROR_INJECTION_H */

include/asm-generic/vmlinux.lds.h

@@ -136,13 +136,13 @@
 #define KPROBE_BLACKLIST()
 #endif
 
-#ifdef CONFIG_BPF_KPROBE_OVERRIDE
-#define ERROR_INJECT_LIST()	. = ALIGN(8);						\
-				VMLINUX_SYMBOL(__start_kprobe_error_inject_list) = .;	\
-				KEEP(*(_kprobe_error_inject_list))			\
-				VMLINUX_SYMBOL(__stop_kprobe_error_inject_list) = .;
+#ifdef CONFIG_FUNCTION_ERROR_INJECTION
+#define ERROR_INJECT_WHITELIST()	. = ALIGN(8);			      \
+			VMLINUX_SYMBOL(__start_error_injection_whitelist) = .;\
+			KEEP(*(_error_injection_whitelist))		      \
+			VMLINUX_SYMBOL(__stop_error_injection_whitelist) = .;
 #else
-#define ERROR_INJECT_LIST()
+#define ERROR_INJECT_WHITELIST()
 #endif
 
 #ifdef CONFIG_EVENT_TRACING
@@ -573,7 +573,7 @@
 	FTRACE_EVENTS()							\
 	TRACE_SYSCALLS()						\
 	KPROBE_BLACKLIST()						\
-	ERROR_INJECT_LIST()						\
+	ERROR_INJECT_WHITELIST()					\
 	MEM_DISCARD(init.rodata)					\
 	CLK_OF_TABLES()							\
 	RESERVEDMEM_OF_TABLES()						\

include/linux/bpf.h

@@ -613,15 +613,4 @@ extern const struct bpf_func_proto bpf_sock_map_update_proto;
 void bpf_user_rnd_init_once(void);
 u64 bpf_user_rnd_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 
-#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
-#ifdef CONFIG_BPF_KPROBE_OVERRIDE
-#define BPF_ALLOW_ERROR_INJECTION(fname)				\
-static unsigned long __used						\
-	__attribute__((__section__("_kprobe_error_inject_list")))	\
-	_eil_addr_##fname = (unsigned long)fname;
-#else
-#define BPF_ALLOW_ERROR_INJECTION(fname)
-#endif
-#endif
-
 #endif /* _LINUX_BPF_H */

include/linux/error-injection.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_ERROR_INJECTION_H
+#define _LINUX_ERROR_INJECTION_H
+
+#ifdef CONFIG_FUNCTION_ERROR_INJECTION
+
+#include <asm/error-injection.h>
+
+extern bool within_error_injection_list(unsigned long addr);
+
+#else /* !CONFIG_FUNCTION_ERROR_INJECTION */
+
+#include <asm-generic/error-injection.h>
+static inline bool within_error_injection_list(unsigned long addr)
+{
+	return false;
+}
+
+#endif
+
+#endif /* _LINUX_ERROR_INJECTION_H */

include/linux/kprobes.h

@@ -271,7 +271,6 @@ extern bool arch_kprobe_on_func_entry(unsigned long offset);
 extern bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset);
 
 extern bool within_kprobe_blacklist(unsigned long addr);
-extern bool within_kprobe_error_injection_list(unsigned long addr);
 
 struct kprobe_insn_cache {
 	struct mutex mutex;

include/linux/module.h

@@ -476,9 +476,9 @@ struct module {
 	unsigned int num_ctors;
 #endif
 
-#ifdef CONFIG_BPF_KPROBE_OVERRIDE
-	unsigned int num_kprobe_ei_funcs;
-	unsigned long *kprobe_ei_funcs;
+#ifdef CONFIG_FUNCTION_ERROR_INJECTION
+	unsigned int num_ei_funcs;
+	unsigned long *ei_funcs;
 #endif
 } ____cacheline_aligned __randomize_layout;
 #ifndef MODULE_ARCH_INIT

kernel/kprobes.c

@@ -83,16 +83,6 @@ static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
 	return &(kretprobe_table_locks[hash].lock);
 }
 
-/* List of symbols that can be overriden for error injection. */
-static LIST_HEAD(kprobe_error_injection_list);
-static DEFINE_MUTEX(kprobe_ei_mutex);
-struct kprobe_ei_entry {
-	struct list_head list;
-	unsigned long start_addr;
-	unsigned long end_addr;
-	void *priv;
-};
-
 /* Blacklist -- list of struct kprobe_blacklist_entry */
 static LIST_HEAD(kprobe_blacklist);
 
@@ -1404,17 +1394,6 @@ bool within_kprobe_blacklist(unsigned long addr)
 	return false;
 }
 
-bool within_kprobe_error_injection_list(unsigned long addr)
-{
-	struct kprobe_ei_entry *ent;
-
-	list_for_each_entry(ent, &kprobe_error_injection_list, list) {
-		if (addr >= ent->start_addr && addr < ent->end_addr)
-			return true;
-	}
-	return false;
-}
-
 /*
  * If we have a symbol_name argument, look it up and add the offset field
  * to it. This way, we can specify a relative address to a symbol.
@@ -2189,86 +2168,6 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
 	return 0;
 }
 
-#ifdef CONFIG_BPF_KPROBE_OVERRIDE
-/* Markers of the _kprobe_error_inject_list section */
-extern unsigned long __start_kprobe_error_inject_list[];
-extern unsigned long __stop_kprobe_error_inject_list[];
-
-/*
- * Lookup and populate the kprobe_error_injection_list.
- *
- * For safety reasons we only allow certain functions to be overriden with
- * bpf_error_injection, so we need to populate the list of the symbols that have
- * been marked as safe for overriding.
- */
-static void populate_kprobe_error_injection_list(unsigned long *start,
-						 unsigned long *end,
-						 void *priv)
-{
-	unsigned long *iter;
-	struct kprobe_ei_entry *ent;
-	unsigned long entry, offset = 0, size = 0;
-
-	mutex_lock(&kprobe_ei_mutex);
-	for (iter = start; iter < end; iter++) {
-		entry = arch_deref_entry_point((void *)*iter);
-
-		if (!kernel_text_address(entry) ||
-		    !kallsyms_lookup_size_offset(entry, &size, &offset)) {
-			pr_err("Failed to find error inject entry at %p\n",
-				(void *)entry);
-			continue;
-		}
-
-		ent = kmalloc(sizeof(*ent), GFP_KERNEL);
-		if (!ent)
-			break;
-		ent->start_addr = entry;
-		ent->end_addr = entry + size;
-		ent->priv = priv;
-		INIT_LIST_HEAD(&ent->list);
-		list_add_tail(&ent->list, &kprobe_error_injection_list);
-	}
-	mutex_unlock(&kprobe_ei_mutex);
-}
-
-static void __init populate_kernel_kprobe_ei_list(void)
-{
-	populate_kprobe_error_injection_list(__start_kprobe_error_inject_list,
-					     __stop_kprobe_error_inject_list,
-					     NULL);
-}
-
-static void module_load_kprobe_ei_list(struct module *mod)
-{
-	if (!mod->num_kprobe_ei_funcs)
-		return;
-	populate_kprobe_error_injection_list(mod->kprobe_ei_funcs,
-					     mod->kprobe_ei_funcs +
-					     mod->num_kprobe_ei_funcs, mod);
-}
-
-static void module_unload_kprobe_ei_list(struct module *mod)
-{
-	struct kprobe_ei_entry *ent, *n;
-	if (!mod->num_kprobe_ei_funcs)
-		return;
-
-	mutex_lock(&kprobe_ei_mutex);
-	list_for_each_entry_safe(ent, n, &kprobe_error_injection_list, list) {
-		if (ent->priv == mod) {
-			list_del_init(&ent->list);
-			kfree(ent);
-		}
-	}
-	mutex_unlock(&kprobe_ei_mutex);
-}
-#else
-static inline void __init populate_kernel_kprobe_ei_list(void) {}
-static inline void module_load_kprobe_ei_list(struct module *m) {}
-static inline void module_unload_kprobe_ei_list(struct module *m) {}
-#endif
-
 /* Module notifier call back, checking kprobes on the module */
 static int kprobes_module_callback(struct notifier_block *nb,
 				   unsigned long val, void *data)
@@ -2279,11 +2178,6 @@ static int kprobes_module_callback(struct notifier_block *nb,
 	unsigned int i;
 	int checkcore = (val == MODULE_STATE_GOING);
 
-	if (val == MODULE_STATE_COMING)
-		module_load_kprobe_ei_list(mod);
-	else if (val == MODULE_STATE_GOING)
-		module_unload_kprobe_ei_list(mod);
-
 	if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
 		return NOTIFY_DONE;
 
@@ -2346,8 +2240,6 @@ static int __init init_kprobes(void)
 		pr_err("Please take care of using kprobes.\n");
 	}
 
-	populate_kernel_kprobe_ei_list();
-
 	if (kretprobe_blacklist_size) {
 		/* lookup the function address from its name */
 		for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
@@ -2515,56 +2407,6 @@ static const struct file_operations debugfs_kprobe_blacklist_ops = {
 	.release        = seq_release,
 };
 
-/*
- * kprobes/error_injection_list -- shows which functions can be overriden for
- * error injection.
- * */
-static void *kprobe_ei_seq_start(struct seq_file *m, loff_t *pos)
-{
-	mutex_lock(&kprobe_ei_mutex);
-	return seq_list_start(&kprobe_error_injection_list, *pos);
-}
-
-static void kprobe_ei_seq_stop(struct seq_file *m, void *v)
-{
-	mutex_unlock(&kprobe_ei_mutex);
-}
-
-static void *kprobe_ei_seq_next(struct seq_file *m, void *v, loff_t *pos)
-{
-	return seq_list_next(v, &kprobe_error_injection_list, pos);
-}
-
-static int kprobe_ei_seq_show(struct seq_file *m, void *v)
-{
-	char buffer[KSYM_SYMBOL_LEN];
-	struct kprobe_ei_entry *ent =
-		list_entry(v, struct kprobe_ei_entry, list);
-
-	sprint_symbol(buffer, ent->start_addr);
-	seq_printf(m, "%s\n", buffer);
-	return 0;
-}
-
-static const struct seq_operations kprobe_ei_seq_ops = {
-	.start = kprobe_ei_seq_start,
-	.next  = kprobe_ei_seq_next,
-	.stop  = kprobe_ei_seq_stop,
-	.show  = kprobe_ei_seq_show,
-};
-
-static int kprobe_ei_open(struct inode *inode, struct file *filp)
-{
-	return seq_open(filp, &kprobe_ei_seq_ops);
-}
-
-static const struct file_operations debugfs_kprobe_ei_ops = {
-	.open           = kprobe_ei_open,
-	.read           = seq_read,
-	.llseek         = seq_lseek,
-	.release        = seq_release,
-};
-
 static void arm_all_kprobes(void)
 {
 	struct hlist_head *head;
@@ -2706,11 +2548,6 @@ static int __init debugfs_kprobe_init(void)
 	if (!file)
 		goto error;
 
-	file = debugfs_create_file("error_injection_list", 0444, dir, NULL,
-				  &debugfs_kprobe_ei_ops);
-	if (!file)
-		goto error;
-
 	return 0;
 
 error:

kernel/module.c

@@ -3118,10 +3118,10 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 					     sizeof(*mod->ftrace_callsites),
 					     &mod->num_ftrace_callsites);
 #endif
-#ifdef CONFIG_BPF_KPROBE_OVERRIDE
-	mod->kprobe_ei_funcs = section_objs(info, "_kprobe_error_inject_list",
-					    sizeof(*mod->kprobe_ei_funcs),
-					    &mod->num_kprobe_ei_funcs);
+#ifdef CONFIG_FUNCTION_ERROR_INJECTION
+	mod->ei_funcs = section_objs(info, "_error_injection_whitelist",
+					    sizeof(*mod->ei_funcs),
+					    &mod->num_ei_funcs);
 #endif
 	mod->extable = section_objs(info, "__ex_table",
 				    sizeof(*mod->extable), &mod->num_exentries);

kernel/trace/Kconfig

@@ -533,7 +533,7 @@ config FUNCTION_PROFILER
 config BPF_KPROBE_OVERRIDE
 	bool "Enable BPF programs to override a kprobed function"
 	depends on BPF_EVENTS
-	depends on HAVE_KPROBE_OVERRIDE
+	depends on FUNCTION_ERROR_INJECTION
 	default n
 	help
 	 Allows BPF to override the execution of a probed function and

kernel/trace/bpf_trace.c

@@ -14,7 +14,7 @@
 #include <linux/uaccess.h>
 #include <linux/ctype.h>
 #include <linux/kprobes.h>
-#include <asm/kprobes.h>
+#include <linux/error-injection.h>
 
 #include "trace_probe.h"
 #include "trace.h"
@@ -84,7 +84,7 @@ EXPORT_SYMBOL_GPL(trace_call_bpf);
 BPF_CALL_2(bpf_override_return, struct pt_regs *, regs, unsigned long, rc)
 {
 	regs_set_return_value(regs, rc);
-	arch_kprobe_override_function(regs);
+	override_function_with_return(regs);
 	return 0;
 }
 

kernel/trace/trace_kprobe.c

@@ -21,6 +21,7 @@
 #include <linux/module.h>
 #include <linux/uaccess.h>
 #include <linux/rculist.h>
+#include <linux/error-injection.h>
 
 #include "trace_probe.h"
 
@@ -107,7 +108,7 @@ bool trace_kprobe_error_injectable(struct trace_event_call *call)
 	} else {
 		addr = (unsigned long)tk->rp.kp.addr;
 	}
-	return within_kprobe_error_injection_list(addr);
+	return within_error_injection_list(addr);
 }
 
 static int register_kprobe_event(struct trace_kprobe *tk);

lib/Kconfig.debug

@@ -1500,6 +1500,10 @@ config FAULT_INJECTION
 	  Provide fault-injection framework.
 	  For more details, see Documentation/fault-injection/.
 
+config FUNCTION_ERROR_INJECTION
+	def_bool y
+	depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
+
 config FAILSLAB
 	bool "Fault-injection capability for kmalloc"
 	depends on FAULT_INJECTION

lib/Makefile

@@ -149,6 +149,7 @@ obj-$(CONFIG_NETDEV_NOTIFIER_ERROR_INJECT) += netdev-notifier-error-inject.o
 obj-$(CONFIG_MEMORY_NOTIFIER_ERROR_INJECT) += memory-notifier-error-inject.o
 obj-$(CONFIG_OF_RECONFIG_NOTIFIER_ERROR_INJECT) += \
 	of-reconfig-notifier-error-inject.o
+obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
 
 lib-$(CONFIG_GENERIC_BUG) += bug.o
 

lib/error-inject.c

+// SPDX-License-Identifier: GPL-2.0
+// error-inject.c: Function-level error injection table
+#include <linux/error-injection.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/kprobes.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+
+/* Whitelist of symbols that can be overridden for error injection. */
+static LIST_HEAD(error_injection_list);
+static DEFINE_MUTEX(ei_mutex);
+struct ei_entry {
+	struct list_head list;
+	unsigned long start_addr;
+	unsigned long end_addr;
+	void *priv;
+};
+
+bool within_error_injection_list(unsigned long addr)
+{
+	struct ei_entry *ent;
+	bool ret = false;
+
+	mutex_lock(&ei_mutex);
+	list_for_each_entry(ent, &error_injection_list, list) {
+		if (addr >= ent->start_addr && addr < ent->end_addr) {
+			ret = true;
+			break;
+		}
+	}
+	mutex_unlock(&ei_mutex);
+	return ret;
+}
+
+/*
+ * Lookup and populate the error_injection_list.
+ *
+ * For safety reasons we only allow certain functions to be overridden with
+ * bpf_error_injection, so we need to populate the list of the symbols that have
+ * been marked as safe for overriding.
+ */
+static void populate_error_injection_list(unsigned long *start,
+					  unsigned long *end, void *priv)
+{
+	unsigned long *iter;
+	struct ei_entry *ent;
+	unsigned long entry, offset = 0, size = 0;
+
+	mutex_lock(&ei_mutex);
+	for (iter = start; iter < end; iter++) {
+		entry = arch_deref_entry_point((void *)*iter);
+
+		if (!kernel_text_address(entry) ||
+		    !kallsyms_lookup_size_offset(entry, &size, &offset)) {
+			pr_err("Failed to find error inject entry at %p\n",
+				(void *)entry);
+			continue;
+		}
+
+		ent = kmalloc(sizeof(*ent), GFP_KERNEL);
+		if (!ent)
+			break;
+		ent->start_addr = entry;
+		ent->end_addr = entry + size;
+		ent->priv = priv;
+		INIT_LIST_HEAD(&ent->list);
+		list_add_tail(&ent->list, &error_injection_list);
+	}
+	mutex_unlock(&ei_mutex);
+}
+
+/* Markers of the _error_inject_whitelist section */
+extern unsigned long __start_error_injection_whitelist[];
+extern unsigned long __stop_error_injection_whitelist[];
+
+static void __init populate_kernel_ei_list(void)
+{
+	populate_error_injection_list(__start_error_injection_whitelist,
+				      __stop_error_injection_whitelist,
+				      NULL);
+}
+
+#ifdef CONFIG_MODULES
+static void module_load_ei_list(struct module *mod)
+{
+	if (!mod->num_ei_funcs)
+		return;
+
+	populate_error_injection_list(mod->ei_funcs,
+				      mod->ei_funcs + mod->num_ei_funcs, mod);
+}
+
+static void module_unload_ei_list(struct module *mod)
+{
+	struct ei_entry *ent, *n;
+
+	if (!mod->num_ei_funcs)
+		return;
+
+	mutex_lock(&ei_mutex);
+	list_for_each_entry_safe(ent, n, &error_injection_list, list) {
+		if (ent->priv == mod) {
+			list_del_init(&ent->list);
+			kfree(ent);
+		}
+	}
+	mutex_unlock(&ei_mutex);
+}
+
+/* Module notifier call back, checking error injection table on the module */
+static int ei_module_callback(struct notifier_block *nb,
+			      unsigned long val, void *data)
+{
+	struct module *mod = data;
+
+	if (val == MODULE_STATE_COMING)
+		module_load_ei_list(mod);
+	else if (val == MODULE_STATE_GOING)
+		module_unload_ei_list(mod);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block ei_module_nb = {
+	.notifier_call = ei_module_callback,
+	.priority = 0
+};
+
+static __init int module_ei_init(void)
+{
+	return register_module_notifier(&ei_module_nb);
+}
+#else /* !CONFIG_MODULES */
+#define module_ei_init()	(0)
+#endif
+
+/*
+ * error_injection/whitelist -- shows which functions can be overridden for
+ * error injection.
+ */
+static void *ei_seq_start(struct seq_file *m, loff_t *pos)
+{
+	mutex_lock(&ei_mutex);
+	return seq_list_start(&error_injection_list, *pos);
+}
+
+static void ei_seq_stop(struct seq_file *m, void *v)
+{
+	mutex_unlock(&ei_mutex);
+}
+
+static void *ei_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	return seq_list_next(v, &error_injection_list, pos);
+}
+
+static int ei_seq_show(struct seq_file *m, void *v)
+{
+	struct ei_entry *ent = list_entry(v, struct ei_entry, list);
+
+	seq_printf(m, "%pf\n", (void *)ent->start_addr);
+	return 0;
+}
+
+static const struct seq_operations ei_seq_ops = {
+	.start = ei_seq_start,
+	.next  = ei_seq_next,
+	.stop  = ei_seq_stop,
+	.show  = ei_seq_show,
+};
+
+static int ei_open(struct inode *inode, struct file *filp)
+{
+	return seq_open(filp, &ei_seq_ops);
+}
+
+static const struct file_operations debugfs_ei_ops = {
+	.open           = ei_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = seq_release,
+};
+
+static int __init ei_debugfs_init(void)
+{
+	struct dentry *dir, *file;
+
+	dir = debugfs_create_dir("error_injection", NULL);
+	if (!dir)
+		return -ENOMEM;
+
+	file = debugfs_create_file("list", 0444, dir, NULL, &debugfs_ei_ops);
+	if (!file) {
+		debugfs_remove(dir);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+static int __init init_error_injection(void)
+{
+	populate_kernel_ei_list();
+
+	if (!module_ei_init())
+		ei_debugfs_init();
+
+	return 0;
+}
+late_initcall(init_error_injection);