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Date: Tue, 22 Feb 2022 17:58:47 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Aaron Tomlin <atomlin@...hat.com>,
"mcgrof@...nel.org" <mcgrof@...nel.org>
CC: "cl@...ux.com" <cl@...ux.com>,
"pmladek@...e.com" <pmladek@...e.com>,
"mbenes@...e.cz" <mbenes@...e.cz>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"jeyu@...nel.org" <jeyu@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
"void@...ifault.com" <void@...ifault.com>,
"atomlin@...mlin.com" <atomlin@...mlin.com>,
"allen.lkml@...il.com" <allen.lkml@...il.com>,
"joe@...ches.com" <joe@...ches.com>,
"msuchanek@...e.de" <msuchanek@...e.de>,
"oleksandr@...alenko.name" <oleksandr@...alenko.name>
Subject: Re: [PATCH v8 04/13] module: Move livepatch support to a separate
file
Le 22/02/2022 à 15:12, Aaron Tomlin a écrit :
> No functional change.
>
> This patch migrates livepatch support (i.e. used during module
> add/or load and remove/or deletion) from core module code into
> kernel/module/livepatch.c. At the moment it contains code to
> persist Elf information about a given livepatch module, only.
>
> Signed-off-by: Aaron Tomlin <atomlin@...hat.com>
Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
> include/linux/module.h | 9 ++--
> kernel/module/Makefile | 1 +
> kernel/module/internal.h | 22 ++++++++
> kernel/module/livepatch.c | 74 +++++++++++++++++++++++++++
> kernel/module/main.c | 102 ++++----------------------------------
> 5 files changed, 110 insertions(+), 98 deletions(-)
> create mode 100644 kernel/module/livepatch.c
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 1e135fd5c076..7ec9715de7dc 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -663,17 +663,14 @@ static inline bool module_requested_async_probing(struct module *module)
> return module && module->async_probe_requested;
> }
>
> -#ifdef CONFIG_LIVEPATCH
> static inline bool is_livepatch_module(struct module *mod)
> {
> +#ifdef CONFIG_LIVEPATCH
> return mod->klp;
> -}
> -#else /* !CONFIG_LIVEPATCH */
> -static inline bool is_livepatch_module(struct module *mod)
> -{
> +#else
> return false;
> +#endif
> }
> -#endif /* CONFIG_LIVEPATCH */
>
> bool is_module_sig_enforced(void);
> void set_module_sig_enforced(void);
> diff --git a/kernel/module/Makefile b/kernel/module/Makefile
> index cdd5c61b8c7f..ed3aacb04f17 100644
> --- a/kernel/module/Makefile
> +++ b/kernel/module/Makefile
> @@ -10,3 +10,4 @@ KCOV_INSTRUMENT_module.o := n
> obj-y += main.o
> obj-$(CONFIG_MODULE_DECOMPRESS) += decompress.o
> obj-$(CONFIG_MODULE_SIG) += signing.o
> +obj-$(CONFIG_LIVEPATCH) += livepatch.o
> diff --git a/kernel/module/internal.h b/kernel/module/internal.h
> index e0775e66bcf7..ad7a444253ed 100644
> --- a/kernel/module/internal.h
> +++ b/kernel/module/internal.h
> @@ -57,6 +57,28 @@ struct load_info {
>
> int mod_verify_sig(const void *mod, struct load_info *info);
>
> +#ifdef CONFIG_LIVEPATCH
> +int copy_module_elf(struct module *mod, struct load_info *info);
> +void free_module_elf(struct module *mod);
> +#else /* !CONFIG_LIVEPATCH */
> +static inline int copy_module_elf(struct module *mod, struct load_info *info)
> +{
> + return 0;
> +}
> +
> +static inline void free_module_elf(struct module *mod) { }
> +#endif /* CONFIG_LIVEPATCH */
> +
> +static inline bool set_livepatch_module(struct module *mod)
> +{
> +#ifdef CONFIG_LIVEPATCH
> + mod->klp = true;
> + return true;
> +#else
> + return false;
> +#endif
> +}
> +
> #ifdef CONFIG_MODULE_DECOMPRESS
> int module_decompress(struct load_info *info, const void *buf, size_t size);
> void module_decompress_cleanup(struct load_info *info);
> diff --git a/kernel/module/livepatch.c b/kernel/module/livepatch.c
> new file mode 100644
> index 000000000000..486d4ff92719
> --- /dev/null
> +++ b/kernel/module/livepatch.c
> @@ -0,0 +1,74 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Module livepatch support
> + *
> + * Copyright (C) 2016 Jessica Yu <jeyu@...hat.com>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/string.h>
> +#include <linux/slab.h>
> +#include "internal.h"
> +
> +/*
> + * Persist Elf information about a module. Copy the Elf header,
> + * section header table, section string table, and symtab section
> + * index from info to mod->klp_info.
> + */
> +int copy_module_elf(struct module *mod, struct load_info *info)
> +{
> + unsigned int size, symndx;
> + int ret;
> +
> + size = sizeof(*mod->klp_info);
> + mod->klp_info = kmalloc(size, GFP_KERNEL);
> + if (!mod->klp_info)
> + return -ENOMEM;
> +
> + /* Elf header */
> + size = sizeof(mod->klp_info->hdr);
> + memcpy(&mod->klp_info->hdr, info->hdr, size);
> +
> + /* Elf section header table */
> + size = sizeof(*info->sechdrs) * info->hdr->e_shnum;
> + mod->klp_info->sechdrs = kmemdup(info->sechdrs, size, GFP_KERNEL);
> + if (!mod->klp_info->sechdrs) {
> + ret = -ENOMEM;
> + goto free_info;
> + }
> +
> + /* Elf section name string table */
> + size = info->sechdrs[info->hdr->e_shstrndx].sh_size;
> + mod->klp_info->secstrings = kmemdup(info->secstrings, size, GFP_KERNEL);
> + if (!mod->klp_info->secstrings) {
> + ret = -ENOMEM;
> + goto free_sechdrs;
> + }
> +
> + /* Elf symbol section index */
> + symndx = info->index.sym;
> + mod->klp_info->symndx = symndx;
> +
> + /*
> + * For livepatch modules, core_kallsyms.symtab is a complete
> + * copy of the original symbol table. Adjust sh_addr to point
> + * to core_kallsyms.symtab since the copy of the symtab in module
> + * init memory is freed at the end of do_init_module().
> + */
> + mod->klp_info->sechdrs[symndx].sh_addr = (unsigned long)mod->core_kallsyms.symtab;
> +
> + return 0;
> +
> +free_sechdrs:
> + kfree(mod->klp_info->sechdrs);
> +free_info:
> + kfree(mod->klp_info);
> + return ret;
> +}
> +
> +void free_module_elf(struct module *mod)
> +{
> + kfree(mod->klp_info->sechdrs);
> + kfree(mod->klp_info->secstrings);
> + kfree(mod->klp_info);
> +}
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 5f5e21f972dd..3596ebf3a6c3 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -2043,81 +2043,6 @@ static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
> }
> #endif /* CONFIG_STRICT_MODULE_RWX */
>
> -#ifdef CONFIG_LIVEPATCH
> -/*
> - * Persist Elf information about a module. Copy the Elf header,
> - * section header table, section string table, and symtab section
> - * index from info to mod->klp_info.
> - */
> -static int copy_module_elf(struct module *mod, struct load_info *info)
> -{
> - unsigned int size, symndx;
> - int ret;
> -
> - size = sizeof(*mod->klp_info);
> - mod->klp_info = kmalloc(size, GFP_KERNEL);
> - if (mod->klp_info == NULL)
> - return -ENOMEM;
> -
> - /* Elf header */
> - size = sizeof(mod->klp_info->hdr);
> - memcpy(&mod->klp_info->hdr, info->hdr, size);
> -
> - /* Elf section header table */
> - size = sizeof(*info->sechdrs) * info->hdr->e_shnum;
> - mod->klp_info->sechdrs = kmemdup(info->sechdrs, size, GFP_KERNEL);
> - if (mod->klp_info->sechdrs == NULL) {
> - ret = -ENOMEM;
> - goto free_info;
> - }
> -
> - /* Elf section name string table */
> - size = info->sechdrs[info->hdr->e_shstrndx].sh_size;
> - mod->klp_info->secstrings = kmemdup(info->secstrings, size, GFP_KERNEL);
> - if (mod->klp_info->secstrings == NULL) {
> - ret = -ENOMEM;
> - goto free_sechdrs;
> - }
> -
> - /* Elf symbol section index */
> - symndx = info->index.sym;
> - mod->klp_info->symndx = symndx;
> -
> - /*
> - * For livepatch modules, core_kallsyms.symtab is a complete
> - * copy of the original symbol table. Adjust sh_addr to point
> - * to core_kallsyms.symtab since the copy of the symtab in module
> - * init memory is freed at the end of do_init_module().
> - */
> - mod->klp_info->sechdrs[symndx].sh_addr = \
> - (unsigned long) mod->core_kallsyms.symtab;
> -
> - return 0;
> -
> -free_sechdrs:
> - kfree(mod->klp_info->sechdrs);
> -free_info:
> - kfree(mod->klp_info);
> - return ret;
> -}
> -
> -static void free_module_elf(struct module *mod)
> -{
> - kfree(mod->klp_info->sechdrs);
> - kfree(mod->klp_info->secstrings);
> - kfree(mod->klp_info);
> -}
> -#else /* !CONFIG_LIVEPATCH */
> -static int copy_module_elf(struct module *mod, struct load_info *info)
> -{
> - return 0;
> -}
> -
> -static void free_module_elf(struct module *mod)
> -{
> -}
> -#endif /* CONFIG_LIVEPATCH */
> -
> void __weak module_memfree(void *module_region)
> {
> /*
> @@ -3092,30 +3017,23 @@ static int copy_chunked_from_user(void *dst, const void __user *usrc, unsigned l
> return 0;
> }
>
> -#ifdef CONFIG_LIVEPATCH
> static int check_modinfo_livepatch(struct module *mod, struct load_info *info)
> {
> - if (get_modinfo(info, "livepatch")) {
> - mod->klp = true;
> + if (!get_modinfo(info, "livepatch"))
> + /* Nothing more to do */
> + return 0;
> +
> + if (set_livepatch_module(mod)) {
> add_taint_module(mod, TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
> pr_notice_once("%s: tainting kernel with TAINT_LIVEPATCH\n",
> - mod->name);
> - }
> -
> - return 0;
> -}
> -#else /* !CONFIG_LIVEPATCH */
> -static int check_modinfo_livepatch(struct module *mod, struct load_info *info)
> -{
> - if (get_modinfo(info, "livepatch")) {
> - pr_err("%s: module is marked as livepatch module, but livepatch support is disabled",
> - mod->name);
> - return -ENOEXEC;
> + mod->name);
> + return 0;
> }
>
> - return 0;
> + pr_err("%s: module is marked as livepatch module, but livepatch support is disabled",
> + mod->name);
> + return -ENOEXEC;
> }
> -#endif /* CONFIG_LIVEPATCH */
>
> static void check_modinfo_retpoline(struct module *mod, struct load_info *info)
> {
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