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>
#include <asm/sections.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;
int etype;
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;
}
int get_injectable_error_type(unsigned long addr)
{
struct ei_entry *ent;
int ei_type = -EINVAL;
mutex_lock(&ei_mutex);
list_for_each_entry(ent, &error_injection_list, list) {
if (addr >= ent->start_addr && addr < ent->end_addr) {
ei_type = ent->etype;
break;
}
}
mutex_unlock(&ei_mutex);
return ei_type;
}
/*
* 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(struct error_injection_entry *start,
struct error_injection_entry *end,
void *priv)
{
struct error_injection_entry *iter;
struct ei_entry *ent;
unsigned long entry, offset = 0, size = 0;
mutex_lock(&ei_mutex);
for (iter = start; iter < end; iter++) {
entry = (unsigned long)dereference_symbol_descriptor((void *)iter->addr);
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->etype = iter->etype;
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 struct error_injection_entry __start_error_injection_whitelist[];
extern struct error_injection_entry __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 const char *error_type_string(int etype)
{
switch (etype) {
case EI_ETYPE_NULL:
return "NULL";
case EI_ETYPE_ERRNO:
return "ERRNO";
case EI_ETYPE_ERRNO_NULL:
return "ERRNO_NULL";
case EI_ETYPE_TRUE:
return "TRUE";
default:
return "(unknown)";
}
}
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, "%ps\t%s\n", (void *)ent->start_addr,
error_type_string(ent->etype));
return 0;
}
static const struct seq_operations ei_sops = {
.start = ei_seq_start,
.next = ei_seq_next,
.stop = ei_seq_stop,
.show = ei_seq_show,
};
DEFINE_SEQ_ATTRIBUTE(ei);
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, &ei_fops);
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);