[linux.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);

static void fei_post_handler(struct kprobe *kp, struct pt_regs *regs,
			     unsigned long flags)
{
	/*
	 * A dummy post handler is required to prohibit optimizing, because
	 * jump optimization does not support execution path overriding.
	 */
}

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->kp.post_handler = fei_post_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);
		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(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
b6b76dd6 MH	17	static void fei_post_handler(struct kprobe kp, struct pt_regs regs,
	18	unsigned long flags)
	19	{
	20	/*
	21	* A dummy post handler is required to prohibit optimizing, because
	22	* jump optimization does not support execution path overriding.
	23	*/
	24	}
	25
4b1a29a7 MH	26	struct fei_attr {
	27	struct list_head list;
	28	struct kprobe kp;
	29	unsigned long retval;
	30	};
	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;
	35
	36	static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv)
	37	{
	38	switch (get_injectable_error_type(addr)) {
	39	case EI_ETYPE_NULL:
	40	if (retv != 0)
	41	return 0;
	42	break;
	43	case EI_ETYPE_ERRNO:
	44	if (retv < (unsigned long)-MAX_ERRNO)
	45	return (unsigned long)-EINVAL;
	46	break;
	47	case EI_ETYPE_ERRNO_NULL:
	48	if (retv != 0 && retv < (unsigned long)-MAX_ERRNO)
	49	return (unsigned long)-EINVAL;
	50	break;
	51	}
	52
	53	return retv;
	54	}
	55
	56	static struct fei_attr fei_attr_new(const char sym, unsigned long addr)
	57	{
	58	struct fei_attr *attr;
	59
	60	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
	61	if (attr) {
	62	attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL);
	63	if (!attr->kp.symbol_name) {
	64	kfree(attr);
	65	return NULL;
	66	}
	67	attr->kp.pre_handler = fei_kprobe_handler;
b6b76dd6	68	attr->kp.post_handler = fei_post_handler;
4b1a29a7 MH	69	attr->retval = adjust_error_retval(addr, 0);
	70	INIT_LIST_HEAD(&attr->list);
	71	}
	72	return attr;
	73	}
	74
	75	static void fei_attr_free(struct fei_attr *attr)
	76	{
	77	if (attr) {
	78	kfree(attr->kp.symbol_name);
	79	kfree(attr);
	80	}
	81	}
	82
	83	static struct fei_attr fei_attr_lookup(const char sym)
	84	{
	85	struct fei_attr *attr;
	86
	87	list_for_each_entry(attr, &fei_attr_list, list) {
	88	if (!strcmp(attr->kp.symbol_name, sym))
	89	return attr;
	90	}
	91
	92	return NULL;
	93	}
	94
	95	static bool fei_attr_is_valid(struct fei_attr *_attr)
	96	{
	97	struct fei_attr *attr;
	98
	99	list_for_each_entry(attr, &fei_attr_list, list) {
	100	if (attr == _attr)
	101	return true;
	102	}
	103
	104	return false;
	105	}
	106
	107	static int fei_retval_set(void *data, u64 val)
	108	{
	109	struct fei_attr *attr = data;
	110	unsigned long retv = (unsigned long)val;
	111	int err = 0;
	112
	113	mutex_lock(&fei_lock);
	114	/*
	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
	117	* its member.
	118	*/
	119	if (!fei_attr_is_valid(attr)) {
	120	err = -ENOENT;
	121	goto out;
	122	}
	123
	124	if (attr->kp.addr) {
	125	if (adjust_error_retval((unsigned long)attr->kp.addr,
	126	val) != retv)
	127	err = -EINVAL;
	128	}
	129	if (!err)
	130	attr->retval = val;
	131	out:
	132	mutex_unlock(&fei_lock);
133
134	return err;
135	}
136
137	static int fei_retval_get(void data, u64 val)
138	{
139	struct fei_attr *attr = data;
140	int err = 0;
141
142	mutex_lock(&fei_lock);
143	/* Here we also validate @attr to ensure it still exists. */
144	if (!fei_attr_is_valid(attr))
145	err = -ENOENT;
146	else
147	*val = attr->retval;
148	mutex_unlock(&fei_lock);
149
150	return err;
151	}
152	DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set,
153	"%llx\n");
154
155	static int fei_debugfs_add_attr(struct fei_attr *attr)
156	{
157	struct dentry *dir;
158
159	dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir);
160	if (!dir)
161	return -ENOMEM;
162
163	if (!debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops)) {
164	debugfs_remove_recursive(dir);
165	return -ENOMEM;
166	}
167
168	return 0;
169	}
170
171	static void fei_debugfs_remove_attr(struct fei_attr *attr)
172	{
173	struct dentry *dir;
174
175	dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir);
176	if (dir)
177	debugfs_remove_recursive(dir);
178	}
179
180	static int fei_kprobe_handler(struct kprobe kp, struct pt_regs regs)
181	{
182	struct fei_attr *attr = container_of(kp, struct fei_attr, kp);
183
184	if (should_fail(&fei_fault_attr, 1)) {
185	regs_set_return_value(regs, attr->retval);
186	override_function_with_return(regs);
4b1a29a7 MH	187	return 1;
	188	}
	189
	190	return 0;
	191	}
	192	NOKPROBE_SYMBOL(fei_kprobe_handler)
	193
	194	static void fei_seq_start(struct seq_file m, loff_t *pos)
	195	{
	196	mutex_lock(&fei_lock);
	197	return seq_list_start(&fei_attr_list, *pos);
	198	}
	199
	200	static void fei_seq_stop(struct seq_file m, void v)
	201	{
	202	mutex_unlock(&fei_lock);
	203	}
	204
	205	static void fei_seq_next(struct seq_file m, void v, loff_t pos)
	206	{
	207	return seq_list_next(v, &fei_attr_list, pos);
	208	}
	209
	210	static int fei_seq_show(struct seq_file m, void v)
	211	{
	212	struct fei_attr *attr = list_entry(v, struct fei_attr, list);
	213
	214	seq_printf(m, "%pf\n", attr->kp.addr);
	215	return 0;
	216	}
	217
	218	static const struct seq_operations fei_seq_ops = {
	219	.start = fei_seq_start,
	220	.next = fei_seq_next,
	221	.stop = fei_seq_stop,
	222	.show = fei_seq_show,
	223	};
	224
	225	static int fei_open(struct inode inode, struct file file)
	226	{
	227	return seq_open(file, &fei_seq_ops);
	228	}
	229
	230	static void fei_attr_remove(struct fei_attr *attr)
	231	{
	232	fei_debugfs_remove_attr(attr);
	233	unregister_kprobe(&attr->kp);
	234	list_del(&attr->list);
	235	fei_attr_free(attr);
	236	}
	237
	238	static void fei_attr_remove_all(void)
	239	{
	240	struct fei_attr attr, n;
	241
	242	list_for_each_entry_safe(attr, n, &fei_attr_list, list) {
	243	fei_attr_remove(attr);
	244	}
	245	}
	246
	247	static ssize_t fei_write(struct file file, const char __user buffer,
	248	size_t count, loff_t *ppos)
	249	{
	250	struct fei_attr *attr;
251	unsigned long addr;
252	char buf, sym;
253	int ret;
254
255	/* cut off if it is too long */
256	if (count > KSYM_NAME_LEN)
257	count = KSYM_NAME_LEN;
6da2ec56	258	buf = kmalloc(count + 1, GFP_KERNEL);
4b1a29a7 MH	259	if (!buf)
	260	return -ENOMEM;
	261
	262	if (copy_from_user(buf, buffer, count)) {
	263	ret = -EFAULT;
	264	goto out;
	265	}
	266	buf[count] = '\0';
	267	sym = strstrip(buf);
	268
	269	mutex_lock(&fei_lock);
	270
	271	/* Writing just spaces will remove all injection points */
	272	if (sym[0] == '\0') {
	273	fei_attr_remove_all();
	274	ret = count;
	275	goto out;
	276	}
	277	/* Writing !function will remove one injection point */
	278	if (sym[0] == '!') {
	279	attr = fei_attr_lookup(sym + 1);
	280	if (!attr) {
	281	ret = -ENOENT;
	282	goto out;
	283	}
	284	fei_attr_remove(attr);
	285	ret = count;
	286	goto out;
	287	}
	288
	289	addr = kallsyms_lookup_name(sym);
	290	if (!addr) {
	291	ret = -EINVAL;
	292	goto out;
	293	}
	294	if (!within_error_injection_list(addr)) {
	295	ret = -ERANGE;
	296	goto out;
	297	}
	298	if (fei_attr_lookup(sym)) {
	299	ret = -EBUSY;
	300	goto out;
	301	}
	302	attr = fei_attr_new(sym, addr);
	303	if (!attr) {
	304	ret = -ENOMEM;
	305	goto out;
	306	}
	307
	308	ret = register_kprobe(&attr->kp);
	309	if (!ret)
	310	ret = fei_debugfs_add_attr(attr);
	311	if (ret < 0)
	312	fei_attr_remove(attr);
	313	else {
	314	list_add_tail(&attr->list, &fei_attr_list);
	315	ret = count;
	316	}
	317	out:
	318	kfree(buf);
	319	mutex_unlock(&fei_lock);
	320	return ret;
	321	}
	322
323	static const struct file_operations fei_ops = {
324	.open = fei_open,
325	.read = seq_read,
326	.write = fei_write,
327	.llseek = seq_lseek,
328	.release = seq_release,
329	};
330
331	static int __init fei_debugfs_init(void)
332	{
333	struct dentry *dir;
334
335	dir = fault_create_debugfs_attr("fail_function", NULL,
336	&fei_fault_attr);
337	if (IS_ERR(dir))
338	return PTR_ERR(dir);
339
340	/* injectable attribute is just a symlink of error_inject/list */
341	if (!debugfs_create_symlink("injectable", dir,
342	"../error_injection/list"))
343	goto error;
344
345	if (!debugfs_create_file("inject", 0600, dir, NULL, &fei_ops))
346	goto error;
347
348	fei_debugfs_dir = dir;
349
350	return 0;
351	error:
352	debugfs_remove_recursive(dir);
353	return -ENOMEM;
354	}
355
356	late_initcall(fei_debugfs_init);