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);
	}