[linux-block.git] / kernel / fail_function.c

// SPDX-License-Identifier: GPL-2.0
/*
 * fail_function.c: Function-based error injection
 */
#include <linux/error-injection.h>
#include <linux/debugfs.h>
#include <linux/fault-inject.h>
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/uaccess.h>

static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);

struct fei_attr {
	struct list_head list;
	struct kprobe kp;
	unsigned long retval;
};
static DEFINE_MUTEX(fei_lock);
static LIST_HEAD(fei_attr_list);
static DECLARE_FAULT_ATTR(fei_fault_attr);
static struct dentry *fei_debugfs_dir;

static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv)
{
	switch (get_injectable_error_type(addr)) {
	case EI_ETYPE_NULL:
		if (retv != 0)
			return 0;
		break;
	case EI_ETYPE_ERRNO:
		if (retv < (unsigned long)-MAX_ERRNO)
			return (unsigned long)-EINVAL;
		break;
	case EI_ETYPE_ERRNO_NULL:
		if (retv != 0 && retv < (unsigned long)-MAX_ERRNO)
			return (unsigned long)-EINVAL;
		break;
	}

	return retv;
}

static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr)
{
	struct fei_attr *attr;

	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
	if (attr) {
		attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL);
		if (!attr->kp.symbol_name) {
			kfree(attr);
			return NULL;
		}
		attr->kp.pre_handler = fei_kprobe_handler;
		attr->retval = adjust_error_retval(addr, 0);
		INIT_LIST_HEAD(&attr->list);
	}
	return attr;
}

static void fei_attr_free(struct fei_attr *attr)
{
	if (attr) {
		kfree(attr->kp.symbol_name);
		kfree(attr);
	}
}

static struct fei_attr *fei_attr_lookup(const char *sym)
{
	struct fei_attr *attr;

	list_for_each_entry(attr, &fei_attr_list, list) {
		if (!strcmp(attr->kp.symbol_name, sym))
			return attr;
	}

	return NULL;
}

static bool fei_attr_is_valid(struct fei_attr *_attr)
{
	struct fei_attr *attr;

	list_for_each_entry(attr, &fei_attr_list, list) {
		if (attr == _attr)
			return true;
	}

	return false;
}

static int fei_retval_set(void *data, u64 val)
{
	struct fei_attr *attr = data;
	unsigned long retv = (unsigned long)val;
	int err = 0;

	mutex_lock(&fei_lock);
	/*
	 * Since this operation can be done after retval file is removed,
	 * It is safer to check the attr is still valid before accessing
	 * its member.
	 */
	if (!fei_attr_is_valid(attr)) {
		err = -ENOENT;
		goto out;
	}

	if (attr->kp.addr) {
		if (adjust_error_retval((unsigned long)attr->kp.addr,
					val) != retv)
			err = -EINVAL;
	}
	if (!err)
		attr->retval = val;
out:
	mutex_unlock(&fei_lock);

	return err;
}

static int fei_retval_get(void *data, u64 *val)
{
	struct fei_attr *attr = data;
	int err = 0;

	mutex_lock(&fei_lock);
	/* Here we also validate @attr to ensure it still exists. */
	if (!fei_attr_is_valid(attr))
		err = -ENOENT;
	else
		*val = attr->retval;
	mutex_unlock(&fei_lock);

	return err;
}
DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set,
			 "%llx\n");

static int fei_debugfs_add_attr(struct fei_attr *attr)
{
	struct dentry *dir;

	dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir);
	if (!dir)
		return -ENOMEM;

	if (!debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops)) {
		debugfs_remove_recursive(dir);
		return -ENOMEM;
	}

	return 0;
}

static void fei_debugfs_remove_attr(struct fei_attr *attr)
{
	struct dentry *dir;

	dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir);
	if (dir)
		debugfs_remove_recursive(dir);
}

static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
{
	struct fei_attr *attr = container_of(kp, struct fei_attr, kp);

	if (should_fail(&fei_fault_attr, 1)) {
		regs_set_return_value(regs, attr->retval);
		override_function_with_return(regs);
		/* Kprobe specific fixup */
		reset_current_kprobe();
		preempt_enable_no_resched();
		return 1;
	}

	return 0;
}
NOKPROBE_SYMBOL(fei_kprobe_handler)

static void *fei_seq_start(struct seq_file *m, loff_t *pos)
{
	mutex_lock(&fei_lock);
	return seq_list_start(&fei_attr_list, *pos);
}

static void fei_seq_stop(struct seq_file *m, void *v)
{
	mutex_unlock(&fei_lock);
}

static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
	return seq_list_next(v, &fei_attr_list, pos);
}

static int fei_seq_show(struct seq_file *m, void *v)
{
	struct fei_attr *attr = list_entry(v, struct fei_attr, list);

	seq_printf(m, "%pf\n", attr->kp.addr);
	return 0;
}

static const struct seq_operations fei_seq_ops = {
	.start	= fei_seq_start,
	.next	= fei_seq_next,
	.stop	= fei_seq_stop,
	.show	= fei_seq_show,
};

static int fei_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &fei_seq_ops);
}

static void fei_attr_remove(struct fei_attr *attr)
{
	fei_debugfs_remove_attr(attr);
	unregister_kprobe(&attr->kp);
	list_del(&attr->list);
	fei_attr_free(attr);
}

static void fei_attr_remove_all(void)
{
	struct fei_attr *attr, *n;

	list_for_each_entry_safe(attr, n, &fei_attr_list, list) {
		fei_attr_remove(attr);
	}
}

static ssize_t fei_write(struct file *file, const char __user *buffer,
			 size_t count, loff_t *ppos)
{
	struct fei_attr *attr;
	unsigned long addr;
	char *buf, *sym;
	int ret;

	/* cut off if it is too long */
	if (count > KSYM_NAME_LEN)
		count = KSYM_NAME_LEN;
	buf = kmalloc(sizeof(char) * (count + 1), GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	if (copy_from_user(buf, buffer, count)) {
		ret = -EFAULT;
		goto out;
	}
	buf[count] = '\0';
	sym = strstrip(buf);

	mutex_lock(&fei_lock);

	/* Writing just spaces will remove all injection points */
	if (sym[0] == '\0') {
		fei_attr_remove_all();
		ret = count;
		goto out;
	}
	/* Writing !function will remove one injection point */
	if (sym[0] == '!') {
		attr = fei_attr_lookup(sym + 1);
		if (!attr) {
			ret = -ENOENT;
			goto out;
		}
		fei_attr_remove(attr);
		ret = count;
		goto out;
	}

	addr = kallsyms_lookup_name(sym);
	if (!addr) {
		ret = -EINVAL;
		goto out;
	}
	if (!within_error_injection_list(addr)) {
		ret = -ERANGE;
		goto out;
	}
	if (fei_attr_lookup(sym)) {
		ret = -EBUSY;
		goto out;
	}
	attr = fei_attr_new(sym, addr);
	if (!attr) {
		ret = -ENOMEM;
		goto out;
	}

	ret = register_kprobe(&attr->kp);
	if (!ret)
		ret = fei_debugfs_add_attr(attr);
	if (ret < 0)
		fei_attr_remove(attr);
	else {
		list_add_tail(&attr->list, &fei_attr_list);
		ret = count;
	}
out:
	kfree(buf);
	mutex_unlock(&fei_lock);
	return ret;
}

static const struct file_operations fei_ops = {
	.open =		fei_open,
	.read =		seq_read,
	.write =	fei_write,
	.llseek =	seq_lseek,
	.release =	seq_release,
};

static int __init fei_debugfs_init(void)
{
	struct dentry *dir;

	dir = fault_create_debugfs_attr("fail_function", NULL,
					&fei_fault_attr);
	if (IS_ERR(dir))
		return PTR_ERR(dir);

	/* injectable attribute is just a symlink of error_inject/list */
	if (!debugfs_create_symlink("injectable", dir,
				    "../error_injection/list"))
		goto error;

	if (!debugfs_create_file("inject", 0600, dir, NULL, &fei_ops))
		goto error;

	fei_debugfs_dir = dir;

	return 0;
error:
	debugfs_remove_recursive(dir);
	return -ENOMEM;
}

late_initcall(fei_debugfs_init);
Commit	Line	Data
4b1a29a7 MH	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* fail_function.c: Function-based error injection
	4	*/
	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>
	14
	15	static int fei_kprobe_handler(struct kprobe kp, struct pt_regs regs);
	16
	17	struct fei_attr {
	18	struct list_head list;
	19	struct kprobe kp;
	20	unsigned long retval;
	21	};
	22	static DEFINE_MUTEX(fei_lock);
	23	static LIST_HEAD(fei_attr_list);
	24	static DECLARE_FAULT_ATTR(fei_fault_attr);
	25	static struct dentry *fei_debugfs_dir;
	26
	27	static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv)
	28	{
	29	switch (get_injectable_error_type(addr)) {
	30	case EI_ETYPE_NULL:
	31	if (retv != 0)
	32	return 0;
	33	break;
	34	case EI_ETYPE_ERRNO:
	35	if (retv < (unsigned long)-MAX_ERRNO)
	36	return (unsigned long)-EINVAL;
	37	break;
	38	case EI_ETYPE_ERRNO_NULL:
	39	if (retv != 0 && retv < (unsigned long)-MAX_ERRNO)
	40	return (unsigned long)-EINVAL;
	41	break;
	42	}
	43
	44	return retv;
	45	}
	46
	47	static struct fei_attr fei_attr_new(const char sym, unsigned long addr)
	48	{
	49	struct fei_attr *attr;
	50
	51	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
	52	if (attr) {
	53	attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL);
	54	if (!attr->kp.symbol_name) {
	55	kfree(attr);
	56	return NULL;
	57	}
	58	attr->kp.pre_handler = fei_kprobe_handler;
	59	attr->retval = adjust_error_retval(addr, 0);
	60	INIT_LIST_HEAD(&attr->list);
	61	}
	62	return attr;
	63	}
	64
65	static void fei_attr_free(struct fei_attr *attr)
66	{
67	if (attr) {
68	kfree(attr->kp.symbol_name);
69	kfree(attr);
70	}
71	}
72
73	static struct fei_attr fei_attr_lookup(const char sym)
74	{
75	struct fei_attr *attr;
76
77	list_for_each_entry(attr, &fei_attr_list, list) {
78	if (!strcmp(attr->kp.symbol_name, sym))
79	return attr;
80	}
81
82	return NULL;
83	}
84
85	static bool fei_attr_is_valid(struct fei_attr *_attr)
86	{
87	struct fei_attr *attr;
88
89	list_for_each_entry(attr, &fei_attr_list, list) {
90	if (attr == _attr)
91	return true;
92	}
93
94	return false;
95	}
96
97	static int fei_retval_set(void *data, u64 val)
98	{
99	struct fei_attr *attr = data;
100	unsigned long retv = (unsigned long)val;
101	int err = 0;
102
103	mutex_lock(&fei_lock);
104	/*
105	* Since this operation can be done after retval file is removed,
106	* It is safer to check the attr is still valid before accessing
107	* its member.
108	*/
109	if (!fei_attr_is_valid(attr)) {
110	err = -ENOENT;
111	goto out;
112	}
113
114	if (attr->kp.addr) {
115	if (adjust_error_retval((unsigned long)attr->kp.addr,
116	val) != retv)
117	err = -EINVAL;
118	}
119	if (!err)
120	attr->retval = val;
121	out:
122	mutex_unlock(&fei_lock);
123
124	return err;
125	}
126
127	static int fei_retval_get(void data, u64 val)
128	{
129	struct fei_attr *attr = data;
130	int err = 0;
131
132	mutex_lock(&fei_lock);
133	/* Here we also validate @attr to ensure it still exists. */
134	if (!fei_attr_is_valid(attr))
135	err = -ENOENT;
136	else
137	*val = attr->retval;
138	mutex_unlock(&fei_lock);
139
140	return err;
141	}
142	DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set,
143	"%llx\n");
144
145	static int fei_debugfs_add_attr(struct fei_attr *attr)
146	{
147	struct dentry *dir;
148
149	dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir);
150	if (!dir)
151	return -ENOMEM;
152
153	if (!debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops)) {
154	debugfs_remove_recursive(dir);
155	return -ENOMEM;
156	}
157
158	return 0;
159	}
160
161	static void fei_debugfs_remove_attr(struct fei_attr *attr)
162	{
163	struct dentry *dir;
164
165	dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir);
166	if (dir)
167	debugfs_remove_recursive(dir);
168	}
169
170	static int fei_kprobe_handler(struct kprobe kp, struct pt_regs regs)
171	{
172	struct fei_attr *attr = container_of(kp, struct fei_attr, kp);
173
174	if (should_fail(&fei_fault_attr, 1)) {
175	regs_set_return_value(regs, attr->retval);
176	override_function_with_return(regs);
177	/* Kprobe specific fixup */
178	reset_current_kprobe();
179	preempt_enable_no_resched();
180	return 1;
181	}
182
183	return 0;
184	}
185	NOKPROBE_SYMBOL(fei_kprobe_handler)
186
187	static void fei_seq_start(struct seq_file m, loff_t *pos)
188	{
189	mutex_lock(&fei_lock);
190	return seq_list_start(&fei_attr_list, *pos);
191	}
192
193	static void fei_seq_stop(struct seq_file m, void v)
194	{
195	mutex_unlock(&fei_lock);
196	}
197
198	static void fei_seq_next(struct seq_file m, void v, loff_t pos)
199	{
200	return seq_list_next(v, &fei_attr_list, pos);
201	}
202
203	static int fei_seq_show(struct seq_file m, void v)
204	{
205	struct fei_attr *attr = list_entry(v, struct fei_attr, list);
206
207	seq_printf(m, "%pf\n", attr->kp.addr);
208	return 0;
209	}
210
211	static const struct seq_operations fei_seq_ops = {
212	.start = fei_seq_start,
213	.next = fei_seq_next,
214	.stop = fei_seq_stop,
215	.show = fei_seq_show,
216	};
217
218	static int fei_open(struct inode inode, struct file file)
219	{
220	return seq_open(file, &fei_seq_ops);
221	}
222
223	static void fei_attr_remove(struct fei_attr *attr)
224	{
225	fei_debugfs_remove_attr(attr);
226	unregister_kprobe(&attr->kp);
227	list_del(&attr->list);
228	fei_attr_free(attr);
229	}
230
231	static void fei_attr_remove_all(void)
232	{
233	struct fei_attr attr, n;
234
235	list_for_each_entry_safe(attr, n, &fei_attr_list, list) {
236	fei_attr_remove(attr);
237	}
238	}
239
240	static ssize_t fei_write(struct file file, const char __user buffer,
241	size_t count, loff_t *ppos)
242	{
243	struct fei_attr *attr;
244	unsigned long addr;
245	char buf, sym;
246	int ret;
247
248	/* cut off if it is too long */
249	if (count > KSYM_NAME_LEN)
250	count = KSYM_NAME_LEN;
251	buf = kmalloc(sizeof(char) * (count + 1), GFP_KERNEL);
252	if (!buf)
253	return -ENOMEM;
254
255	if (copy_from_user(buf, buffer, count)) {
256	ret = -EFAULT;
257	goto out;
258	}
259	buf[count] = '\0';
260	sym = strstrip(buf);
261
262	mutex_lock(&fei_lock);
263
264	/* Writing just spaces will remove all injection points */
265	if (sym[0] == '\0') {
266	fei_attr_remove_all();
267	ret = count;
268	goto out;
269	}
270	/* Writing !function will remove one injection point */
271	if (sym[0] == '!') {
272	attr = fei_attr_lookup(sym + 1);
273	if (!attr) {
274	ret = -ENOENT;
275	goto out;
276	}
277	fei_attr_remove(attr);
278	ret = count;
279	goto out;
280	}
281
282	addr = kallsyms_lookup_name(sym);
283	if (!addr) {
284	ret = -EINVAL;
285	goto out;
286	}
287	if (!within_error_injection_list(addr)) {
288	ret = -ERANGE;
289	goto out;
290	}
291	if (fei_attr_lookup(sym)) {
292	ret = -EBUSY;
293	goto out;
294	}
295	attr = fei_attr_new(sym, addr);
296	if (!attr) {
297	ret = -ENOMEM;
298	goto out;
299	}
300
301	ret = register_kprobe(&attr->kp);
302	if (!ret)
303	ret = fei_debugfs_add_attr(attr);
304	if (ret < 0)
305	fei_attr_remove(attr);
306	else {
307	list_add_tail(&attr->list, &fei_attr_list);
308	ret = count;
309	}
310	out:
311	kfree(buf);
312	mutex_unlock(&fei_lock);
313	return ret;
314	}
315
316	static const struct file_operations fei_ops = {
317	.open = fei_open,
318	.read = seq_read,
319	.write = fei_write,
320	.llseek = seq_lseek,
321	.release = seq_release,
322	};
323
324	static int __init fei_debugfs_init(void)
325	{
326	struct dentry *dir;
327
328	dir = fault_create_debugfs_attr("fail_function", NULL,
329	&fei_fault_attr);
330	if (IS_ERR(dir))
331	return PTR_ERR(dir);
332
333	/* injectable attribute is just a symlink of error_inject/list */
334	if (!debugfs_create_symlink("injectable", dir,
335	"../error_injection/list"))
336	goto error;
337
338	if (!debugfs_create_file("inject", 0600, dir, NULL, &fei_ops))
339	goto error;
340
341	fei_debugfs_dir = dir;
342
343	return 0;
344	error:
345	debugfs_remove_recursive(dir);
346	return -ENOMEM;
347	}
348
349	late_initcall(fei_debugfs_init);