// SPDX-License-Identifier: GPL-2.0 // error-inject.c: Function-level error injection table #include <linux/error-injection.h> #include <linux/debugfs.h> #include <linux/kallsyms.h> #include <linux/kprobes.h> #include <linux/module.h> #include <linux/mutex.h> #include <linux/list.h> #include <linux/slab.h> /* Whitelist of symbols that can be overridden for error injection. */ static LIST_HEAD(error_injection_list); static DEFINE_MUTEX(ei_mutex); struct ei_entry { struct list_head list; unsigned long start_addr; unsigned long end_addr; int etype; void *priv; }; bool within_error_injection_list(unsigned long addr) { struct ei_entry *ent; bool ret = false; mutex_lock(&ei_mutex); list_for_each_entry(ent, &error_injection_list, list) { if (addr >= ent->start_addr && addr < ent->end_addr) { ret = true; break; } } mutex_unlock(&ei_mutex); return ret; } int get_injectable_error_type(unsigned long addr) { struct ei_entry *ent; list_for_each_entry(ent, &error_injection_list, list) { if (addr >= ent->start_addr && addr < ent->end_addr) return ent->etype; } return EI_ETYPE_NONE; } /* * Lookup and populate the error_injection_list. * * For safety reasons we only allow certain functions to be overridden with * bpf_error_injection, so we need to populate the list of the symbols that have * been marked as safe for overriding. */ static void populate_error_injection_list(struct error_injection_entry *start, struct error_injection_entry *end, void *priv) { struct error_injection_entry *iter; struct ei_entry *ent; unsigned long entry, offset = 0, size = 0; mutex_lock(&ei_mutex); for (iter = start; iter < end; iter++) { entry = arch_deref_entry_point((void *)iter->addr); if (!kernel_text_address(entry) || !kallsyms_lookup_size_offset(entry, &size, &offset)) { pr_err("Failed to find error inject entry at %p\n", (void *)entry); continue; } ent = kmalloc(sizeof(*ent), GFP_KERNEL); if (!ent) break; ent->start_addr = entry; ent->end_addr = entry + size; ent->etype = iter->etype; ent->priv = priv; INIT_LIST_HEAD(&ent->list); list_add_tail(&ent->list, &error_injection_list); } mutex_unlock(&ei_mutex); } /* Markers of the _error_inject_whitelist section */ extern struct error_injection_entry __start_error_injection_whitelist[]; extern struct error_injection_entry __stop_error_injection_whitelist[]; static void __init populate_kernel_ei_list(void) { populate_error_injection_list(__start_error_injection_whitelist, __stop_error_injection_whitelist, NULL); } #ifdef CONFIG_MODULES static void module_load_ei_list(struct module *mod) { if (!mod->num_ei_funcs) return; populate_error_injection_list(mod->ei_funcs, mod->ei_funcs + mod->num_ei_funcs, mod); } static void module_unload_ei_list(struct module *mod) { struct ei_entry *ent, *n; if (!mod->num_ei_funcs) return; mutex_lock(&ei_mutex); list_for_each_entry_safe(ent, n, &error_injection_list, list) { if (ent->priv == mod) { list_del_init(&ent->list); kfree(ent); } } mutex_unlock(&ei_mutex); } /* Module notifier call back, checking error injection table on the module */ static int ei_module_callback(struct notifier_block *nb, unsigned long val, void *data) { struct module *mod = data; if (val == MODULE_STATE_COMING) module_load_ei_list(mod); else if (val == MODULE_STATE_GOING) module_unload_ei_list(mod); return NOTIFY_DONE; } static struct notifier_block ei_module_nb = { .notifier_call = ei_module_callback, .priority = 0 }; static __init int module_ei_init(void) { return register_module_notifier(&ei_module_nb); } #else /* !CONFIG_MODULES */ #define module_ei_init() (0) #endif /* * error_injection/whitelist -- shows which functions can be overridden for * error injection. */ static void *ei_seq_start(struct seq_file *m, loff_t *pos) { mutex_lock(&ei_mutex); return seq_list_start(&error_injection_list, *pos); } static void ei_seq_stop(struct seq_file *m, void *v) { mutex_unlock(&ei_mutex); } static void *ei_seq_next(struct seq_file *m, void *v, loff_t *pos) { return seq_list_next(v, &error_injection_list, pos); } static const char *error_type_string(int etype) { switch (etype) { case EI_ETYPE_NULL: return "NULL"; case EI_ETYPE_ERRNO: return "ERRNO"; case EI_ETYPE_ERRNO_NULL: return "ERRNO_NULL"; default: return "(unknown)"; } } static int ei_seq_show(struct seq_file *m, void *v) { struct ei_entry *ent = list_entry(v, struct ei_entry, list); seq_printf(m, "%ps\t%s\n", (void *)ent->start_addr, error_type_string(ent->etype)); return 0; } static const struct seq_operations ei_seq_ops = { .start = ei_seq_start, .next = ei_seq_next, .stop = ei_seq_stop, .show = ei_seq_show, }; static int ei_open(struct inode *inode, struct file *filp) { return seq_open(filp, &ei_seq_ops); } static const struct file_operations debugfs_ei_ops = { .open = ei_open, .read = seq_read, .llseek = seq_lseek, .release = seq_release, }; static int __init ei_debugfs_init(void) { struct dentry *dir, *file; dir = debugfs_create_dir("error_injection", NULL); if (!dir) return -ENOMEM; file = debugfs_create_file("list", 0444, dir, NULL, &debugfs_ei_ops); if (!file) { debugfs_remove(dir); return -ENOMEM; } return 0; } static int __init init_error_injection(void) { populate_kernel_ei_list(); if (!module_ei_init()) ei_debugfs_init(); return 0; } late_initcall(init_error_injection);