Re: [RFC PATCH 1/9] livepatch: simplify disable error path

[Petr Mladek <pmladek@suse.cz>]

On Fri 2015-02-13 13:25:35, Miroslav Benes wrote:
> On Mon, 9 Feb 2015, Josh Poimboeuf wrote:
> 
> > If registering the function with ftrace has previously succeeded,
> > unregistering will almost never fail.  Even if it does, it's not a fatal
> > error.  We can still carry on and disable the klp_func from being used
> > by removing it from the klp_ops func stack.
> > 
> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> 
> This makes sense, so
> 
> Reviewed-by: Miroslav Benes <mbenes@suse.cz>
> 
> I think this patch could be taken independently of the consistency model. 
> If no one else has any objection...

Yup, it looks good to me.

Reviewed-by: Petr Mladek <pmladek@suse.cz>
 
> Miroslav
> 
> > ---
> >  kernel/livepatch/core.c | 67 +++++++++++++------------------------------------
> >  1 file changed, 17 insertions(+), 50 deletions(-)
> > 
> > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > index 9adf86b..081df77 100644
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> > @@ -322,32 +322,20 @@ static void notrace klp_ftrace_handler(unsigned long ip,
> >  	klp_arch_set_pc(regs, (unsigned long)func->new_func);
> >  }
> >  
> > -static int klp_disable_func(struct klp_func *func)
> > +static void klp_disable_func(struct klp_func *func)
> >  {
> >  	struct klp_ops *ops;
> > -	int ret;
> > -
> > -	if (WARN_ON(func->state != KLP_ENABLED))
> > -		return -EINVAL;
> >  
> > -	if (WARN_ON(!func->old_addr))
> > -		return -EINVAL;
> > +	WARN_ON(func->state != KLP_ENABLED);
> > +	WARN_ON(!func->old_addr);
> >  
> >  	ops = klp_find_ops(func->old_addr);
> >  	if (WARN_ON(!ops))
> > -		return -EINVAL;
> > +		return;
> >  
> >  	if (list_is_singular(&ops->func_stack)) {
> > -		ret = unregister_ftrace_function(&ops->fops);
> > -		if (ret) {
> > -			pr_err("failed to unregister ftrace handler for function '%s' (%d)\n",
> > -			       func->old_name, ret);
> > -			return ret;
> > -		}
> > -
> > -		ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
> > -		if (ret)
> > -			pr_warn("function unregister succeeded but failed to clear the filter\n");
> > +		WARN_ON(unregister_ftrace_function(&ops->fops));
> > +		WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0));
> >  
> >  		list_del_rcu(&func->stack_node);
> >  		list_del(&ops->node);
> > @@ -357,8 +345,6 @@ static int klp_disable_func(struct klp_func *func)
> >  	}
> >  
> >  	func->state = KLP_DISABLED;
> > -
> > -	return 0;
> >  }
> >  
> >  static int klp_enable_func(struct klp_func *func)
> > @@ -419,23 +405,15 @@ err:
> >  	return ret;
> >  }
> >  
> > -static int klp_disable_object(struct klp_object *obj)
> > +static void klp_disable_object(struct klp_object *obj)
> >  {
> >  	struct klp_func *func;
> > -	int ret;
> >  
> > -	for (func = obj->funcs; func->old_name; func++) {
> > -		if (func->state != KLP_ENABLED)
> > -			continue;
> > -
> > -		ret = klp_disable_func(func);
> > -		if (ret)
> > -			return ret;
> > -	}
> > +	for (func = obj->funcs; func->old_name; func++)
> > +		if (func->state == KLP_ENABLED)
> > +			klp_disable_func(func);
> >  
> >  	obj->state = KLP_DISABLED;
> > -
> > -	return 0;
> >  }
> >  
> >  static int klp_enable_object(struct klp_object *obj)
> > @@ -451,22 +429,19 @@ static int klp_enable_object(struct klp_object *obj)
> >  
> >  	for (func = obj->funcs; func->old_name; func++) {
> >  		ret = klp_enable_func(func);
> > -		if (ret)
> > -			goto unregister;
> > +		if (ret) {
> > +			klp_disable_object(obj);
> > +			return ret;
> > +		}
> >  	}
> >  	obj->state = KLP_ENABLED;
> >  
> >  	return 0;
> > -
> > -unregister:
> > -	WARN_ON(klp_disable_object(obj));
> > -	return ret;
> >  }
> >  
> >  static int __klp_disable_patch(struct klp_patch *patch)
> >  {
> >  	struct klp_object *obj;
> > -	int ret;
> >  
> >  	/* enforce stacking: only the last enabled patch can be disabled */
> >  	if (!list_is_last(&patch->list, &klp_patches) &&
> > @@ -476,12 +451,8 @@ static int __klp_disable_patch(struct klp_patch *patch)
> >  	pr_notice("disabling patch '%s'\n", patch->mod->name);
> >  
> >  	for (obj = patch->objs; obj->funcs; obj++) {
> > -		if (obj->state != KLP_ENABLED)
> > -			continue;
> > -
> > -		ret = klp_disable_object(obj);
> > -		if (ret)
> > -			return ret;
> > +		if (obj->state == KLP_ENABLED)
> > +			klp_disable_object(obj);
> >  	}
> >  
> >  	patch->state = KLP_DISABLED;
> > @@ -931,7 +902,6 @@ static void klp_module_notify_going(struct klp_patch *patch,
> >  {
> >  	struct module *pmod = patch->mod;
> >  	struct module *mod = obj->mod;
> > -	int ret;
> >  
> >  	if (patch->state == KLP_DISABLED)
> >  		goto disabled;
> > @@ -939,10 +909,7 @@ static void klp_module_notify_going(struct klp_patch *patch,
> >  	pr_notice("reverting patch '%s' on unloading module '%s'\n",
> >  		  pmod->name, mod->name);
> >  
> > -	ret = klp_disable_object(obj);
> > -	if (ret)
> > -		pr_warn("failed to revert patch '%s' on module '%s' (%d)\n",
> > -			pmod->name, mod->name, ret);
> > +	klp_disable_object(obj);
> >  
> >  disabled:
> >  	klp_free_object_loaded(obj);
> > -- 
> > 2.1.0
> > 
> > --
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