From 844af6811571a5677f5d2da0abc229d3a75fc2dd Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 13 Jun 2014 11:27:38 -0500 Subject: [PATCH] kmod/core: support for patching of future loaded modules This allows a patch module to contain patched functions for modules which haven't been loaded yet. If/when the module is loaded later, it will be patched from the module notifier function. --- kmod/core/core.c | 175 ++++++++++++++++++++++++------ kmod/core/kpatch.h | 1 + kpatch-build/create-diff-object.c | 6 +- 3 files changed, 149 insertions(+), 33 deletions(-) diff --git a/kmod/core/core.c b/kmod/core/core.c index cbaf0ec..905e49d 100644 --- a/kmod/core/core.c +++ b/kmod/core/core.c @@ -201,6 +201,11 @@ static void kpatch_backtrace_address_verify(void *data, unsigned long address, struct kpatch_func *active_func; func = &kpmod->funcs[i]; + + /* check if patch depends on a future module load */ + if (!func->old_addr) + continue; + active_func = kpatch_get_func(func->old_addr); if (!active_func) { /* patching an unpatched func */ @@ -289,8 +294,9 @@ static int kpatch_apply_patch(void *data) /* tentatively add the new funcs to the global func hash */ for (i = 0; i < num_funcs; i++) - hash_add_rcu(kpatch_func_hash, &funcs[i].node, - funcs[i].old_addr); + if (funcs[i].old_addr) + hash_add_rcu(kpatch_func_hash, &funcs[i].node, + funcs[i].old_addr); /* memory barrier between func hash add and state change */ smp_wmb(); @@ -305,7 +311,8 @@ static int kpatch_apply_patch(void *data) /* Failed, we have to rollback patching process */ for (i = 0; i < num_funcs; i++) - hash_del_rcu(&funcs[i].node); + if (funcs[i].old_addr) + hash_del_rcu(&funcs[i].node); return -EBUSY; } @@ -334,7 +341,8 @@ static int kpatch_remove_patch(void *data) /* Succeeded, remove all updating funcs from hash table */ for (i = 0; i < num_funcs; i++) - hash_del_rcu(&funcs[i].node); + if (funcs[i].old_addr) + hash_del_rcu(&funcs[i].node); return 0; } @@ -522,7 +530,7 @@ static int kpatch_write_relocations(struct kpatch_module *kpmod) unsigned long core = (unsigned long)kpmod->mod->module_core; unsigned long core_ro_size = kpmod->mod->core_ro_size; unsigned long core_size = kpmod->mod->core_size; - unsigned long src_addr; + unsigned long src; struct module *mod; for (i = 0; i < kpmod->dynrelas_nr; i++) { @@ -530,49 +538,60 @@ static int kpatch_write_relocations(struct kpatch_module *kpmod) if (!strcmp(dynrela->objname, "vmlinux")) { /* vmlinux */ - ret = kpatch_verify_symbol_match(dynrela->name, dynrela->src); + + /* check if reloc has already been written */ + if (kpmod->enabled) + continue; + + ret = kpatch_verify_symbol_match(dynrela->name, + dynrela->src); if (ret) return ret; - src_addr = dynrela->src; } else { - /* module, dynrela->src is not right */ + /* module, dynrela->src needs to be discovered */ + + /* check if reloc has already been written */ + if (dynrela->src) + continue; + + /* check if dynrela depends on a future loaded module */ mutex_lock(&module_mutex); mod = find_module(dynrela->objname); mutex_unlock(&module_mutex); - if (!mod) { - pr_err("unable to find module '%s'\n", - dynrela->objname); - return -EINVAL; - } - src_addr = kpatch_find_module_symbol(mod, dynrela->name); - if (!src_addr) { + if (!mod) + continue; + + src = kpatch_find_module_symbol(mod, dynrela->name); + if (!src) { pr_err("unable to find symbol '%s' in module '%s'\n", dynrela->name, mod->name); return -EINVAL; } + + dynrela->src = src; } switch (dynrela->type) { case R_X86_64_PC32: loc = dynrela->dest; - val = (u32)(src_addr + dynrela->addend - + val = (u32)(dynrela->src + dynrela->addend - dynrela->dest); size = 4; break; case R_X86_64_32S: loc = dynrela->dest; - val = (s32)src_addr + dynrela->addend; + val = (s32)dynrela->src + dynrela->addend; size = 4; break; case R_X86_64_64: loc = dynrela->dest; - val = src_addr; + val = dynrela->src; size = 8; break; default: printk("unsupported rela type %ld for source %s (0x%lx <- 0x%lx) at index %d\n", dynrela->type, dynrela->name, - dynrela->dest, src_addr, i); + dynrela->dest, dynrela->src, i); return -EINVAL; } @@ -604,21 +623,24 @@ static int kpatch_write_relocations(struct kpatch_module *kpmod) return 0; } -static int kpatch_calculate_old_addr(struct kpatch_func *func) +static void kpatch_calculate_old_addr(struct kpatch_func *func) { struct module *module; if (!strcmp(func->patch->objname, "vmlinux")) { func->old_addr = func->patch->old_offset; - return 0; + return; } + /* + * If the module hasn't been loaded yet, we'll patch it later in + * kpatch_module_notify(). + */ mutex_lock(&module_mutex); module = find_module(func->patch->objname); if (!module) { mutex_unlock(&module_mutex); - pr_err("patch contains code for a module that is not loaded\n"); - return -EINVAL; + return; } /* should never fail because we have the mutex */ @@ -628,6 +650,69 @@ static int kpatch_calculate_old_addr(struct kpatch_func *func) func->mod = module; func->old_addr = (unsigned long)module->module_core + func->patch->old_offset; +} + +static int kpatch_module_notify(struct notifier_block *nb, unsigned long action, + void *data) +{ + struct module *mod = data; + struct kpatch_module *kpmod; + int printed = 0, ret = 0, i; + + if (action != MODULE_STATE_COMING) + return ret; + + down(&kpatch_mutex); + + list_for_each_entry(kpmod, &kpmod_list, list) { + if (!kpmod->pending) + continue; + + /* temporarily clear pending, can be set again below */ + kpmod->pending = 0; + + for (i = 0; i < kpmod->patches_nr; i++) { + struct kpatch_func *func = &kpmod->funcs[i]; + + /* check if it has already been patched */ + if (func->old_addr) + continue; + + /* calculate actual old location (refs if module) */ + kpatch_calculate_old_addr(func); + + if (!func->old_addr) { + kpmod->pending = 1; + continue; + } + + if (!printed) { + pr_notice("patching newly loaded module '%s'\n", + mod->name); + printed = 1; + } + + ret = kpatch_ftrace_add_func(func->old_addr); + if (ret) + goto out; + + /* add to the global func hash */ + hash_add_rcu(kpatch_func_hash, &func->node, + func->old_addr); + } + + /* write any newly valid relocations */ + ret = kpatch_write_relocations(kpmod); + if (ret) + goto out; + } + +out: + up(&kpatch_mutex); + + /* no way to stop the module load on error */ + WARN(ret, "error (%d) patching newly loaded module '%s'\n", ret, + mod->name); return 0; } @@ -640,16 +725,15 @@ int kpatch_register(struct kpatch_module *kpmod, bool replace) if (!kpmod->mod || !kpmod->patches || !num_funcs) return -EINVAL; - kpmod->enabled = false; - funcs = kzalloc(sizeof(*funcs) * num_funcs, GFP_KERNEL); if (!funcs) return -ENOMEM; - kpmod->funcs = funcs; - down(&kpatch_mutex); + kpmod->enabled = false; + kpmod->pending = 0; + kpmod->funcs = funcs; list_add_tail(&kpmod->list, &kpmod_list); if (!try_module_get(kpmod->mod)) { @@ -665,9 +749,13 @@ int kpatch_register(struct kpatch_module *kpmod, bool replace) func->patch = &kpmod->patches[i]; /* calculate actual old location (refs if module) */ - ret = kpatch_calculate_old_addr(func); - if (ret) - goto err_rollback; + kpatch_calculate_old_addr(func); + + /* check if patch depends on a future loaded module */ + if (!func->old_addr) { + kpmod->pending = 1; + continue; + } ret = kpatch_verify_symbol_match(func->patch->name, func->old_addr); @@ -819,6 +907,8 @@ int kpatch_unregister(struct kpatch_module *kpmod) } for (i = 0; i < num_funcs; i++) { + if (!funcs[i].old_addr) + continue; ret = kpatch_ftrace_remove_func(funcs[i].old_addr); if (ret) { WARN(1, "can't unregister ftrace for address 0x%lx\n", @@ -843,23 +933,44 @@ out: } EXPORT_SYMBOL(kpatch_unregister); + +static struct notifier_block kpatch_module_nb = { + .notifier_call = kpatch_module_notify, + .priority = INT_MIN, /* called last */ +}; + static int kpatch_init(void) { + int ret; + kpatch_root_kobj = kobject_create_and_add("kpatch", kernel_kobj); if (!kpatch_root_kobj) return -ENOMEM; kpatch_patches_kobj = kobject_create_and_add("patches", kpatch_root_kobj); - if (!kpatch_patches_kobj) - return -ENOMEM; + if (!kpatch_patches_kobj) { + ret = -ENOMEM; + goto err_root_kobj; + } + + ret = register_module_notifier(&kpatch_module_nb); + if (ret) + goto err_patches_kobj; return 0; + +err_patches_kobj: + kobject_put(kpatch_patches_kobj); +err_root_kobj: + kobject_put(kpatch_root_kobj); + return ret; } static void kpatch_exit(void) { WARN_ON(kpatch_num_patched != 0); + WARN_ON(unregister_module_notifier(&kpatch_module_nb)); kobject_put(kpatch_patches_kobj); kobject_put(kpatch_root_kobj); } diff --git a/kmod/core/kpatch.h b/kmod/core/kpatch.h index 7035470..90d3aca 100644 --- a/kmod/core/kpatch.h +++ b/kmod/core/kpatch.h @@ -58,6 +58,7 @@ struct kpatch_module { /* private */ struct list_head list; struct kpatch_func *funcs; + bool pending; }; extern struct kobject *kpatch_patches_kobj; diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c index aeba1c9..743b3be 100644 --- a/kpatch-build/create-diff-object.c +++ b/kpatch-build/create-diff-object.c @@ -1734,7 +1734,11 @@ void kpatch_create_dynamic_rela_sections(struct kpatch_elf *kelf, rela->sym->name, result.value, result.size); /* dest filed in by rela entry below */ - dynrelas[index].src = result.value; + if (!strcmp(objname, "vmlinux")) + dynrelas[index].src = result.value; + else + /* for modules, src is discovered at runtime */ + dynrelas[index].src = 0; dynrelas[index].addend = rela->addend; dynrelas[index].type = rela->type;