// 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円') {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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