Re: [RFC PATCH 2/5] module: save load_info for livepatch modules
From: Miroslav Benes <mbenes@suse.cz>
Date: 2015-11-11 14:17:17
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On Mon, 9 Nov 2015, Jessica Yu wrote:
quoted hunk ↗ jump to hunk
diff --git a/include/linux/module.h b/include/linux/module.h index 3a19c79..c8680b1 100644 --- a/include/linux/module.h +++ b/include/linux/module.h
[...]
+#ifdef CONFIG_LIVEPATCH +extern void klp_prepare_patch_module(struct module *mod, + struct load_info *info); +extern int +apply_relocate_add(Elf64_Shdr *sechdrs, const char *strtab, + unsigned int symindex, unsigned int relsec, + struct module *me); +#endif + #else /* !CONFIG_MODULES... */
apply_relocate_add() is already in include/linux/moduleloader.h (guarded by CONFIG_MODULES_USE_ELF_RELA), so maybe we can just include that where we need it. As for the klp_prepare_patch_module() wouldn't it be better to have it in our livepatch.h and include that in kernel/module.c?
quoted hunk ↗ jump to hunk
/* Given an address, look for it in the exception tables. */diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 6e53441..087a8c7 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c@@ -1001,6 +1001,23 @@ static struct notifier_block klp_module_nb = { .priority = INT_MIN+1, /* called late but before ftrace notifier */ }; +/* + * Save necessary information from info in order to be able to + * patch modules that might be loaded later + */ +void klp_prepare_patch_module(struct module *mod, struct load_info *info) +{ + Elf_Shdr *symsect; + + symsect = info->sechdrs + info->index.sym; + /* update sh_addr to point to symtab */ + symsect->sh_addr = (unsigned long)info->hdr + symsect->sh_offset; + + mod->info = kzalloc(sizeof(*info), GFP_KERNEL); + memcpy(mod->info, info, sizeof(*info)); + +}
What about arch-specific 'struct mod_arch_specific'? We need to preserve it somewhere as well for s390x and other non-x86 architectures.
+#ifdef CONFIG_LIVEPATCH + /* + * Save sechdrs, indices, and other data from info + * in order to patch to-be-loaded modules. + * Do not call free_copy() for livepatch modules. + */ + if (get_modinfo((struct load_info *)info, "livepatch")) + klp_prepare_patch_module(mod, info); + else + free_copy(info); +#else /* Get rid of temporary copy. */ free_copy(info); +#endif
Maybe I am missing something but isn't it necessary to call vfree() on info somewhere in the end? Regards, Miroslav