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

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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