From 1d05334d2899bd3ecdf01beb53f0a70884a7f471 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 29 Apr 2020 10:24:45 -0500 Subject: livepatch: Remove .klp.arch After the previous patch, vmlinux-specific KLP relocations are now applied early during KLP module load. This means that .klp.arch sections are no longer needed for *vmlinux-specific* KLP relocations. One might think they're still needed for *module-specific* KLP relocations. If a to-be-patched module is loaded *after* its corresponding KLP module is loaded, any corresponding KLP relocations will be delayed until the to-be-patched module is loaded. If any special sections (.parainstructions, for example) rely on those relocations, their initializations (apply_paravirt) need to be done afterwards. Thus the apparent need for arch_klp_init_object_loaded() and its corresponding .klp.arch sections -- it allows some of the special section initializations to be done at a later time. But... if you look closer, that dependency between the special sections and the module-specific KLP relocations doesn't actually exist in reality. Looking at the contents of the .altinstructions and .parainstructions sections, there's not a realistic scenario in which a KLP module's .altinstructions or .parainstructions section needs to access a symbol in a to-be-patched module. It might need to access a local symbol or even a vmlinux symbol; but not another module's symbol. When a special section needs to reference a local or vmlinux symbol, a normal rela can be used instead of a KLP rela. Since the special section initializations don't actually have any real dependency on module-specific KLP relocations, .klp.arch and arch_klp_init_object_loaded() no longer have a reason to exist. So remove them. As Peter said much more succinctly: So the reason for .klp.arch was that .klp.rela.* stuff would overwrite paravirt instructions. If that happens you're doing it wrong. Those RELAs are core kernel, not module, and thus should've happened in .rela.* sections at patch-module loading time. Reverting this removes the two apply_{paravirt,alternatives}() calls from the late patching path, and means we don't have to worry about them when removing module_disable_ro(). [ jpoimboe: Rewrote patch description. Tweaked klp_init_object_loaded() error path. ] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Josh Poimboeuf Acked-by: Peter Zijlstra (Intel) Acked-by: Joe Lawrence Acked-by: Miroslav Benes Signed-off-by: Jiri Kosina --- kernel/livepatch/core.c | 27 +++++++++------------------ 1 file changed, 9 insertions(+), 18 deletions(-) (limited to 'kernel/livepatch') diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index c02791e5c75b..16632e75112a 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -729,12 +729,6 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func) func->old_sympos ? func->old_sympos : 1); } -/* Arches may override this to finish any remaining arch-specific tasks */ -void __weak arch_klp_init_object_loaded(struct klp_patch *patch, - struct klp_object *obj) -{ -} - int klp_apply_object_relocs(struct klp_patch *patch, struct klp_object *obj) { int i, ret; @@ -764,10 +758,11 @@ static int klp_init_object_loaded(struct klp_patch *patch, struct klp_func *func; int ret; - mutex_lock(&text_mutex); - module_disable_ro(patch->mod); - if (klp_is_module(obj)) { + + mutex_lock(&text_mutex); + module_disable_ro(patch->mod); + /* * Only write module-specific relocations here * (.klp.rela.{module}.*). vmlinux-specific relocations were @@ -775,17 +770,13 @@ static int klp_init_object_loaded(struct klp_patch *patch, * itself. */ ret = klp_apply_object_relocs(patch, obj); - if (ret) { - module_enable_ro(patch->mod, true); - mutex_unlock(&text_mutex); - return ret; - } - } - arch_klp_init_object_loaded(patch, obj); + module_enable_ro(patch->mod, true); + mutex_unlock(&text_mutex); - module_enable_ro(patch->mod, true); - mutex_unlock(&text_mutex); + if (ret) + return ret; + } klp_for_each_func(obj, func) { ret = klp_find_object_symbol(obj->name, func->old_name, -- cgit v1.2.3