linux-kernel - Re: [PATCH v2 1/2] livepatch: use arch_klp_init_object

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Date:	Tue, 2 Aug 2016 10:25:00 +0200 (CEST)
From:	Miroslav Benes <mbenes@...e.cz>
To:	Jessica Yu <jeyu@...hat.com>
cc:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Petr Mladek <pmladek@...e.com>, Jiri Kosina <jikos@...nel.org>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Eugene Shatokhin <eugene.shatokhin@...alab.ru>,
	live-patching@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] livepatch: use arch_klp_init_object_loaded() to
 finish arch-specific tasks

On Thu, 21 Jul 2016, Jessica Yu wrote:

> Introduce arch_klp_init_object_loaded() to complete any additional
> arch-specific tasks during patching. Architecture code may override this
> function.
> 
> Signed-off-by: Jessica Yu <jeyu@...hat.com>
> ---
>  include/linux/livepatch.h |  3 +++
>  kernel/livepatch/core.c   | 12 ++++++++++--
>  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
> index a93a0b2..9072f04 100644
> --- a/include/linux/livepatch.h
> +++ b/include/linux/livepatch.h
> @@ -116,6 +116,9 @@ int klp_unregister_patch(struct klp_patch *);
>  int klp_enable_patch(struct klp_patch *);
>  int klp_disable_patch(struct klp_patch *);
>  
> +void arch_klp_init_object_loaded(struct klp_patch *patch,
> +				 struct klp_object *obj);
> +
>  /* Called from the module loader during module coming/going states */
>  int klp_module_coming(struct module *mod);
>  void klp_module_going(struct module *mod);
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 5c2bc10..164eff6 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -274,7 +274,6 @@ static int klp_write_object_relocations(struct module *pmod,
>  
>  	objname = klp_is_module(obj) ? obj->name : "vmlinux";
>  
> -	module_disable_ro(pmod);
>  	/* For each klp relocation section */
>  	for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
>  		sec = pmod->klp_info->sechdrs + i;
> @@ -309,7 +308,6 @@ static int klp_write_object_relocations(struct module *pmod,
>  			break;
>  	}
>  
> -	module_enable_ro(pmod);
>  	return ret;
>  }
>  
> @@ -763,6 +761,12 @@ 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)
> +{
> +}
> +
>  /* parts of the initialization that is done only when the object is loaded */
>  static int klp_init_object_loaded(struct klp_patch *patch,
>  				  struct klp_object *obj)
> @@ -770,10 +774,14 @@ static int klp_init_object_loaded(struct klp_patch *patch,
>  	struct klp_func *func;
>  	int ret;
>  
> +	module_disable_ro(patch->mod);
>  	ret = klp_write_object_relocations(patch->mod, obj);
>  	if (ret)
>  		return ret;

We need to call module_enable_ro(patch->mod) here before returning back.

Miroslav

>  
> +	arch_klp_init_object_loaded(patch, obj);
> +	module_enable_ro(patch->mod);
> +
>  	klp_for_each_func(obj, func) {
>  		ret = klp_find_object_symbol(obj->name, func->old_name,
>  					     func->old_sympos,
> -- 
> 2.5.5
>