356 lines
7.1 KiB
C
356 lines
7.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* fail_function.c: Function-based error injection
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*/
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#include <linux/error-injection.h>
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#include <linux/debugfs.h>
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#include <linux/fault-inject.h>
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#include <linux/kallsyms.h>
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#include <linux/kprobes.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/uaccess.h>
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static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);
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static void fei_post_handler(struct kprobe *kp, struct pt_regs *regs,
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unsigned long flags)
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{
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/*
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* A dummy post handler is required to prohibit optimizing, because
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* jump optimization does not support execution path overriding.
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*/
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}
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struct fei_attr {
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struct list_head list;
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struct kprobe kp;
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unsigned long retval;
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};
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static DEFINE_MUTEX(fei_lock);
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static LIST_HEAD(fei_attr_list);
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static DECLARE_FAULT_ATTR(fei_fault_attr);
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static struct dentry *fei_debugfs_dir;
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static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv)
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{
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switch (get_injectable_error_type(addr)) {
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case EI_ETYPE_NULL:
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if (retv != 0)
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return 0;
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break;
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case EI_ETYPE_ERRNO:
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if (retv < (unsigned long)-MAX_ERRNO)
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return (unsigned long)-EINVAL;
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break;
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case EI_ETYPE_ERRNO_NULL:
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if (retv != 0 && retv < (unsigned long)-MAX_ERRNO)
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return (unsigned long)-EINVAL;
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break;
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}
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return retv;
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}
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static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr)
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{
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struct fei_attr *attr;
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attr = kzalloc(sizeof(*attr), GFP_KERNEL);
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if (attr) {
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attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL);
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if (!attr->kp.symbol_name) {
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kfree(attr);
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return NULL;
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}
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attr->kp.pre_handler = fei_kprobe_handler;
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attr->kp.post_handler = fei_post_handler;
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attr->retval = adjust_error_retval(addr, 0);
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INIT_LIST_HEAD(&attr->list);
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}
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return attr;
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}
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static void fei_attr_free(struct fei_attr *attr)
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{
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if (attr) {
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kfree(attr->kp.symbol_name);
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kfree(attr);
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}
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}
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static struct fei_attr *fei_attr_lookup(const char *sym)
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{
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struct fei_attr *attr;
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list_for_each_entry(attr, &fei_attr_list, list) {
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if (!strcmp(attr->kp.symbol_name, sym))
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return attr;
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}
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return NULL;
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}
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static bool fei_attr_is_valid(struct fei_attr *_attr)
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{
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struct fei_attr *attr;
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list_for_each_entry(attr, &fei_attr_list, list) {
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if (attr == _attr)
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return true;
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}
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return false;
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}
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static int fei_retval_set(void *data, u64 val)
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{
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struct fei_attr *attr = data;
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unsigned long retv = (unsigned long)val;
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int err = 0;
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mutex_lock(&fei_lock);
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/*
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* Since this operation can be done after retval file is removed,
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* It is safer to check the attr is still valid before accessing
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* its member.
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*/
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if (!fei_attr_is_valid(attr)) {
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err = -ENOENT;
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goto out;
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}
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if (attr->kp.addr) {
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if (adjust_error_retval((unsigned long)attr->kp.addr,
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val) != retv)
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err = -EINVAL;
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}
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if (!err)
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attr->retval = val;
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out:
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mutex_unlock(&fei_lock);
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return err;
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}
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static int fei_retval_get(void *data, u64 *val)
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{
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struct fei_attr *attr = data;
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int err = 0;
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mutex_lock(&fei_lock);
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/* Here we also validate @attr to ensure it still exists. */
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if (!fei_attr_is_valid(attr))
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err = -ENOENT;
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else
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*val = attr->retval;
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mutex_unlock(&fei_lock);
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return err;
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}
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DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set,
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"%llx\n");
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static int fei_debugfs_add_attr(struct fei_attr *attr)
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{
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struct dentry *dir;
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dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir);
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if (!dir)
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return -ENOMEM;
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if (!debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops)) {
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debugfs_remove_recursive(dir);
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return -ENOMEM;
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}
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return 0;
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}
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static void fei_debugfs_remove_attr(struct fei_attr *attr)
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{
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struct dentry *dir;
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dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir);
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debugfs_remove_recursive(dir);
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}
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static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
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{
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struct fei_attr *attr = container_of(kp, struct fei_attr, kp);
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if (should_fail(&fei_fault_attr, 1)) {
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regs_set_return_value(regs, attr->retval);
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override_function_with_return(regs);
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return 1;
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}
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return 0;
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}
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NOKPROBE_SYMBOL(fei_kprobe_handler)
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static void *fei_seq_start(struct seq_file *m, loff_t *pos)
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{
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mutex_lock(&fei_lock);
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return seq_list_start(&fei_attr_list, *pos);
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}
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static void fei_seq_stop(struct seq_file *m, void *v)
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{
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mutex_unlock(&fei_lock);
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}
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static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos)
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{
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return seq_list_next(v, &fei_attr_list, pos);
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}
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static int fei_seq_show(struct seq_file *m, void *v)
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{
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struct fei_attr *attr = list_entry(v, struct fei_attr, list);
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seq_printf(m, "%ps\n", attr->kp.addr);
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return 0;
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}
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static const struct seq_operations fei_seq_ops = {
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.start = fei_seq_start,
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.next = fei_seq_next,
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.stop = fei_seq_stop,
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.show = fei_seq_show,
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};
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static int fei_open(struct inode *inode, struct file *file)
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{
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return seq_open(file, &fei_seq_ops);
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}
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static void fei_attr_remove(struct fei_attr *attr)
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{
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fei_debugfs_remove_attr(attr);
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unregister_kprobe(&attr->kp);
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list_del(&attr->list);
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fei_attr_free(attr);
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}
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static void fei_attr_remove_all(void)
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{
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struct fei_attr *attr, *n;
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list_for_each_entry_safe(attr, n, &fei_attr_list, list) {
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fei_attr_remove(attr);
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}
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}
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static ssize_t fei_write(struct file *file, const char __user *buffer,
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size_t count, loff_t *ppos)
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{
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struct fei_attr *attr;
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unsigned long addr;
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char *buf, *sym;
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int ret;
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/* cut off if it is too long */
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if (count > KSYM_NAME_LEN)
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count = KSYM_NAME_LEN;
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buf = kmalloc(count + 1, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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if (copy_from_user(buf, buffer, count)) {
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ret = -EFAULT;
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goto out;
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}
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buf[count] = '\0';
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sym = strstrip(buf);
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mutex_lock(&fei_lock);
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/* Writing just spaces will remove all injection points */
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if (sym[0] == '\0') {
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fei_attr_remove_all();
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ret = count;
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goto out;
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}
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/* Writing !function will remove one injection point */
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if (sym[0] == '!') {
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attr = fei_attr_lookup(sym + 1);
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if (!attr) {
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ret = -ENOENT;
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goto out;
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}
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fei_attr_remove(attr);
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ret = count;
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goto out;
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}
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addr = kallsyms_lookup_name(sym);
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if (!addr) {
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ret = -EINVAL;
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goto out;
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}
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if (!within_error_injection_list(addr)) {
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ret = -ERANGE;
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goto out;
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}
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if (fei_attr_lookup(sym)) {
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ret = -EBUSY;
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goto out;
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}
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attr = fei_attr_new(sym, addr);
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if (!attr) {
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ret = -ENOMEM;
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goto out;
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}
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ret = register_kprobe(&attr->kp);
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if (!ret)
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ret = fei_debugfs_add_attr(attr);
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if (ret < 0)
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fei_attr_remove(attr);
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else {
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list_add_tail(&attr->list, &fei_attr_list);
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ret = count;
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}
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out:
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kfree(buf);
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mutex_unlock(&fei_lock);
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return ret;
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}
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static const struct file_operations fei_ops = {
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.open = fei_open,
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.read = seq_read,
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.write = fei_write,
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.llseek = seq_lseek,
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.release = seq_release,
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};
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static int __init fei_debugfs_init(void)
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{
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struct dentry *dir;
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dir = fault_create_debugfs_attr("fail_function", NULL,
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&fei_fault_attr);
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if (IS_ERR(dir))
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return PTR_ERR(dir);
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/* injectable attribute is just a symlink of error_inject/list */
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if (!debugfs_create_symlink("injectable", dir,
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"../error_injection/list"))
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goto error;
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if (!debugfs_create_file("inject", 0600, dir, NULL, &fei_ops))
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goto error;
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fei_debugfs_dir = dir;
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return 0;
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error:
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debugfs_remove_recursive(dir);
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return -ENOMEM;
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}
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late_initcall(fei_debugfs_init);
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