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- // 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:
- return 0;
- 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;
- case EI_ETYPE_TRUE:
- return 1;
- }
- 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 void fei_debugfs_add_attr(struct fei_attr *attr)
- {
- struct dentry *dir;
- dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir);
- debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops);
- }
- static void fei_debugfs_remove_attr(struct fei_attr *attr)
- {
- debugfs_lookup_and_remove(attr->kp.symbol_name, fei_debugfs_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, "%ps\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 = memdup_user_nul(buffer, count);
- if (IS_ERR(buf))
- return PTR_ERR(buf);
- 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) {
- fei_attr_free(attr);
- goto out;
- }
- fei_debugfs_add_attr(attr);
- list_add_tail(&attr->list, &fei_attr_list);
- ret = count;
- out:
- mutex_unlock(&fei_lock);
- kfree(buf);
- 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 */
- debugfs_create_symlink("injectable", dir, "../error_injection/list");
- debugfs_create_file("inject", 0600, dir, NULL, &fei_ops);
- fei_debugfs_dir = dir;
- return 0;
- }
- late_initcall(fei_debugfs_init);
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