Re: [PATCH v5 04/13] module: Move livepatch support to a separate file

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 09/02/2022 à 18:03, 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.

   LD      .tmp_vmlinux.kallsyms1
powerpc64-linux-ld: kernel/livepatch/core.o: in function `klp_enable_patch':
(.text+0x1a0c): undefined reference to `is_livepatch_module'
powerpc64-linux-ld: kernel/module/main.o: in function `free_module':
main.c:(.text+0x50f4): undefined reference to `is_livepatch_module'
powerpc64-linux-ld: kernel/module/main.o: in function `load_module':
main.c:(.text+0x6f20): undefined reference to `is_livepatch_module'
powerpc64-linux-ld: main.c:(.text+0x8390): undefined reference to 
`is_livepatch_module'
powerpc64-linux-ld: main.c:(.text+0x8d6c): undefined reference to 
`is_livepatch_module'
make: *** [Makefile:1155 : vmlinux] Erreur 1


I don't understand why you are uninlining that so simple function.
Such a function is likely a single instruction in assembly, it is 
definitely not worth inlining.

Christophe

> 
> Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
> ---
>   include/linux/module.h    |   5 +-
>   kernel/module/Makefile    |   3 ++
>   kernel/module/internal.h  |  18 +++++++
>   kernel/module/livepatch.c |  80 ++++++++++++++++++++++++++++++
>   kernel/module/main.c      | 102 ++++----------------------------------
>   5 files changed, 112 insertions(+), 96 deletions(-)
>   create mode 100644 kernel/module/livepatch.c
> 
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 1e135fd5c076..680b31ff57fa 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -664,10 +664,7 @@ static inline bool module_requested_async_probing(struct module *module)
>   }
>   
>   #ifdef CONFIG_LIVEPATCH
> -static inline bool is_livepatch_module(struct module *mod)
> -{
> -	return mod->klp;
> -}
> +bool is_livepatch_module(struct module *mod);
>   #else /* !CONFIG_LIVEPATCH */
>   static inline bool is_livepatch_module(struct module *mod)
>   {
> diff --git a/kernel/module/Makefile b/kernel/module/Makefile
> index 2902fc7d0ef1..ee20d864ad19 100644
> --- a/kernel/module/Makefile
> +++ b/kernel/module/Makefile
> @@ -7,3 +7,6 @@ obj-$(CONFIG_MODULES) += main.o
>   obj-$(CONFIG_MODULE_DECOMPRESS) += decompress.o
>   obj-$(CONFIG_MODULE_SIG) += signing.o
>   obj-$(CONFIG_MODULE_SIG_FORMAT) += signature.o
> +ifdef CONFIG_MODULES
> +obj-$(CONFIG_LIVEPATCH) += livepatch.o
> +endif
> diff --git a/kernel/module/internal.h b/kernel/module/internal.h
> index 1cf5d6dabc97..d252e0af1c54 100644
> --- a/kernel/module/internal.h
> +++ b/kernel/module/internal.h
> @@ -58,6 +58,24 @@ 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);
> +bool set_livepatch_module(struct module *mod);
> +#else /* !CONFIG_LIVEPATCH */
> +static inline int copy_module_elf(struct module *mod, struct load_info *info)
> +{
> +	return 0;
> +}
> +
> +static inline bool set_livepatch_module(struct module *mod)
> +{
> +	return false;
> +}
> +
> +static inline void free_module_elf(struct module *mod) { }
> +#endif /* CONFIG_LIVEPATCH */
> +
>   #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..7e9cf530c3f0
> --- /dev/null
> +++ b/kernel/module/livepatch.c
> @@ -0,0 +1,80 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Module livepatch support
> + *
> + * Copyright (C) 2016 Jessica Yu <jeyu@redhat.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 == 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;
> +}
> +
> +void free_module_elf(struct module *mod)
> +{
> +	kfree(mod->klp_info->sechdrs);
> +	kfree(mod->klp_info->secstrings);
> +	kfree(mod->klp_info);
> +}
> +
> +inline bool set_livepatch_module(struct module *mod)
> +{
> +	mod->klp = true;
> +	return true;
> +}
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 750e3ad28679..5f5bd7152b55 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -2042,81 +2042,6 @@ 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)
>   {
>   	/*
> @@ -3091,30 +3016,23 @@ 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)
>   {