The linker script scripts/module.lds.S specifies that all input __klp_objects sections should be consolidated into an output section of the same name, and start/stop symbols should be created to enable scripts/livepatch/init.c to locate this data.
This start/stop pattern is not ideal for modules because the symbols are created even if no __klp_objects input sections are present. Consequently, a dummy __klp_objects section also appears in the resulting module. This unnecessarily pollutes non-livepatch modules. Instead, since modules are relocatable files, the usual method for locating consolidated data in a module is to read its section table. This approach avoids the aforementioned problem. The klp_modinfo already stores a copy of the entire section table with the final addresses. Introduce a helper function that scripts/livepatch/init.c can call to obtain the location of the __klp_objects section from this data. Signed-off-by: Petr Pavlu <[email protected]> --- include/linux/livepatch.h | 3 +++ kernel/livepatch/core.c | 20 ++++++++++++++++++++ scripts/livepatch/init.c | 17 ++++++----------- scripts/module.lds.S | 7 +------ 4 files changed, 30 insertions(+), 17 deletions(-) diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 772919e8096a..ca90adbe89ed 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -175,6 +175,9 @@ int klp_enable_patch(struct klp_patch *); int klp_module_coming(struct module *mod); void klp_module_going(struct module *mod); +struct klp_object_ext *klp_build_locate_init_objects(const struct module *mod, + unsigned int *nr_objs); + void klp_copy_process(struct task_struct *child); void klp_update_patch_state(struct task_struct *task); diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 9917756dae46..4e0ac47b3623 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -1356,6 +1356,26 @@ void klp_module_going(struct module *mod) mutex_unlock(&klp_mutex); } +struct klp_object_ext *klp_build_locate_init_objects(const struct module *mod, + unsigned int *nr_objs) +{ + struct klp_modinfo *info = mod->klp_info; + + for (int i = 1; i < info->hdr.e_shnum; i++) { + Elf_Shdr *shdr = &info->sechdrs[i]; + + if (strcmp(info->secstrings + shdr->sh_name, "__klp_objects")) + continue; + + *nr_objs = shdr->sh_size / sizeof(struct klp_object_ext); + return (struct klp_object_ext *)shdr->sh_addr; + } + + *nr_objs = 0; + return NULL; +} +EXPORT_SYMBOL_GPL(klp_build_locate_init_objects); + static int __init klp_init(void) { klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj); diff --git a/scripts/livepatch/init.c b/scripts/livepatch/init.c index 2274d8f5a482..23e037d6de19 100644 --- a/scripts/livepatch/init.c +++ b/scripts/livepatch/init.c @@ -9,19 +9,16 @@ #include <linux/slab.h> #include <linux/livepatch.h> -extern struct klp_object_ext __start_klp_objects[]; -extern struct klp_object_ext __stop_klp_objects[]; - static struct klp_patch *patch; static int __init livepatch_mod_init(void) { + struct klp_object_ext *obj_exts; struct klp_object *objs; unsigned int nr_objs; int ret; - nr_objs = __stop_klp_objects - __start_klp_objects; - + obj_exts = klp_build_locate_init_objects(THIS_MODULE, &nr_objs); if (!nr_objs) { pr_err("nothing to patch!\n"); ret = -EINVAL; @@ -41,7 +38,7 @@ static int __init livepatch_mod_init(void) } for (int i = 0; i < nr_objs; i++) { - struct klp_object_ext *obj_ext = __start_klp_objects + i; + struct klp_object_ext *obj_ext = obj_exts + i; struct klp_func_ext *funcs_ext = obj_ext->funcs; unsigned int nr_funcs = obj_ext->nr_funcs; struct klp_func *funcs = objs[i].funcs; @@ -90,12 +87,10 @@ static int __init livepatch_mod_init(void) static void __exit livepatch_mod_exit(void) { - unsigned int nr_objs; - - nr_objs = __stop_klp_objects - __start_klp_objects; + struct klp_object *obj; - for (int i = 0; i < nr_objs; i++) - kfree(patch->objs[i].funcs); + klp_for_each_object_static(patch, obj) + kfree(obj->funcs); kfree(patch->objs); kfree(patch); diff --git a/scripts/module.lds.S b/scripts/module.lds.S index 3037d5e5527c..383d19beffb4 100644 --- a/scripts/module.lds.S +++ b/scripts/module.lds.S @@ -35,12 +35,7 @@ SECTIONS { __patchable_function_entries : { *(__patchable_function_entries) } __klp_funcs 0: ALIGN(8) { KEEP(*(__klp_funcs)) } - - __klp_objects 0: ALIGN(8) { - __start_klp_objects = .; - KEEP(*(__klp_objects)) - __stop_klp_objects = .; - } + __klp_objects 0: ALIGN(8) { KEEP(*(__klp_objects)) } #ifdef CONFIG_ARCH_USES_CFI_TRAPS __kcfi_traps : { KEEP(*(.kcfi_traps)) } -- 2.52.0
