1 // SPDX-License-Identifier: GPL-2.0
3 * fail_function.c: Function-based error injection
5 #include <linux/error-injection.h>
6 #include <linux/debugfs.h>
7 #include <linux/fault-inject.h>
8 #include <linux/kallsyms.h>
9 #include <linux/kprobes.h>
10 #include <linux/module.h>
11 #include <linux/mutex.h>
12 #include <linux/slab.h>
13 #include <linux/uaccess.h>
15 static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);
17 static void fei_post_handler(struct kprobe *kp, struct pt_regs *regs,
21 * A dummy post handler is required to prohibit optimizing, because
22 * jump optimization does not support execution path overriding.
27 struct list_head list;
31 static DEFINE_MUTEX(fei_lock);
32 static LIST_HEAD(fei_attr_list);
33 static DECLARE_FAULT_ATTR(fei_fault_attr);
34 static struct dentry *fei_debugfs_dir;
36 static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv)
38 switch (get_injectable_error_type(addr)) {
44 if (retv < (unsigned long)-MAX_ERRNO)
45 return (unsigned long)-EINVAL;
47 case EI_ETYPE_ERRNO_NULL:
48 if (retv != 0 && retv < (unsigned long)-MAX_ERRNO)
49 return (unsigned long)-EINVAL;
56 static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr)
58 struct fei_attr *attr;
60 attr = kzalloc(sizeof(*attr), GFP_KERNEL);
62 attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL);
63 if (!attr->kp.symbol_name) {
67 attr->kp.pre_handler = fei_kprobe_handler;
68 attr->kp.post_handler = fei_post_handler;
69 attr->retval = adjust_error_retval(addr, 0);
70 INIT_LIST_HEAD(&attr->list);
75 static void fei_attr_free(struct fei_attr *attr)
78 kfree(attr->kp.symbol_name);
83 static struct fei_attr *fei_attr_lookup(const char *sym)
85 struct fei_attr *attr;
87 list_for_each_entry(attr, &fei_attr_list, list) {
88 if (!strcmp(attr->kp.symbol_name, sym))
95 static bool fei_attr_is_valid(struct fei_attr *_attr)
97 struct fei_attr *attr;
99 list_for_each_entry(attr, &fei_attr_list, list) {
107 static int fei_retval_set(void *data, u64 val)
109 struct fei_attr *attr = data;
110 unsigned long retv = (unsigned long)val;
113 mutex_lock(&fei_lock);
115 * Since this operation can be done after retval file is removed,
116 * It is safer to check the attr is still valid before accessing
119 if (!fei_attr_is_valid(attr)) {
125 if (adjust_error_retval((unsigned long)attr->kp.addr,
132 mutex_unlock(&fei_lock);
137 static int fei_retval_get(void *data, u64 *val)
139 struct fei_attr *attr = data;
142 mutex_lock(&fei_lock);
143 /* Here we also validate @attr to ensure it still exists. */
144 if (!fei_attr_is_valid(attr))
148 mutex_unlock(&fei_lock);
152 DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set,
155 static void fei_debugfs_add_attr(struct fei_attr *attr)
159 dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir);
161 debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops);
164 static void fei_debugfs_remove_attr(struct fei_attr *attr)
168 dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir);
169 debugfs_remove_recursive(dir);
172 static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
174 struct fei_attr *attr = container_of(kp, struct fei_attr, kp);
176 if (should_fail(&fei_fault_attr, 1)) {
177 regs_set_return_value(regs, attr->retval);
178 override_function_with_return(regs);
184 NOKPROBE_SYMBOL(fei_kprobe_handler)
186 static void *fei_seq_start(struct seq_file *m, loff_t *pos)
188 mutex_lock(&fei_lock);
189 return seq_list_start(&fei_attr_list, *pos);
192 static void fei_seq_stop(struct seq_file *m, void *v)
194 mutex_unlock(&fei_lock);
197 static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos)
199 return seq_list_next(v, &fei_attr_list, pos);
202 static int fei_seq_show(struct seq_file *m, void *v)
204 struct fei_attr *attr = list_entry(v, struct fei_attr, list);
206 seq_printf(m, "%ps\n", attr->kp.addr);
210 static const struct seq_operations fei_seq_ops = {
211 .start = fei_seq_start,
212 .next = fei_seq_next,
213 .stop = fei_seq_stop,
214 .show = fei_seq_show,
217 static int fei_open(struct inode *inode, struct file *file)
219 return seq_open(file, &fei_seq_ops);
222 static void fei_attr_remove(struct fei_attr *attr)
224 fei_debugfs_remove_attr(attr);
225 unregister_kprobe(&attr->kp);
226 list_del(&attr->list);
230 static void fei_attr_remove_all(void)
232 struct fei_attr *attr, *n;
234 list_for_each_entry_safe(attr, n, &fei_attr_list, list) {
235 fei_attr_remove(attr);
239 static ssize_t fei_write(struct file *file, const char __user *buffer,
240 size_t count, loff_t *ppos)
242 struct fei_attr *attr;
247 /* cut off if it is too long */
248 if (count > KSYM_NAME_LEN)
249 count = KSYM_NAME_LEN;
250 buf = kmalloc(count + 1, GFP_KERNEL);
254 if (copy_from_user(buf, buffer, count)) {
261 mutex_lock(&fei_lock);
263 /* Writing just spaces will remove all injection points */
264 if (sym[0] == '\0') {
265 fei_attr_remove_all();
269 /* Writing !function will remove one injection point */
271 attr = fei_attr_lookup(sym + 1);
276 fei_attr_remove(attr);
281 addr = kallsyms_lookup_name(sym);
286 if (!within_error_injection_list(addr)) {
290 if (fei_attr_lookup(sym)) {
294 attr = fei_attr_new(sym, addr);
300 ret = register_kprobe(&attr->kp);
302 fei_debugfs_add_attr(attr);
304 fei_attr_remove(attr);
306 list_add_tail(&attr->list, &fei_attr_list);
311 mutex_unlock(&fei_lock);
315 static const struct file_operations fei_ops = {
320 .release = seq_release,
323 static int __init fei_debugfs_init(void)
327 dir = fault_create_debugfs_attr("fail_function", NULL,
332 /* injectable attribute is just a symlink of error_inject/list */
333 debugfs_create_symlink("injectable", dir, "../error_injection/list");
335 debugfs_create_file("inject", 0600, dir, NULL, &fei_ops);
337 fei_debugfs_dir = dir;
342 late_initcall(fei_debugfs_init);