Date:   Wed, 15 Jul 2020 17:39:39 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, x86@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jessica Yu <jeyu@...nel.org>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        live-patching@...r.kernel.org (open list:LIVE PATCHING)
Subject: Re: [PATCH v3 2/3] module: Add lock_modules() and unlock_modules()

On Wed, 15 Jul 2020 01:32:28 +0300
Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> wrote:

> Add wrappers to take the modules "big lock" in order to encapsulate
> conditional compilation (CONFIG_MODULES) inside the wrapper.
> 
> Cc: Andi Kleen <ak@...ux.intel.com>
> Suggested-by: Masami Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
>  include/linux/module.h      | 15 ++++++++++
>  kernel/kprobes.c            |  4 +--
>  kernel/livepatch/core.c     |  8 ++---
>  kernel/module.c             | 60 ++++++++++++++++++-------------------
>  kernel/trace/trace_kprobe.c |  4 +--
>  5 files changed, 53 insertions(+), 38 deletions(-)
> 
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 2e6670860d27..857b84bf9e90 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -902,4 +902,19 @@ static inline bool module_sig_ok(struct module *module)
>  }
>  #endif	/* CONFIG_MODULE_SIG */
>  
> +#ifdef CONFIG_MODULES
> +static inline void lock_modules(void)
> +{
> +	mutex_lock(&module_mutex);
> +}
> +
> +static inline void unlock_modules(void)
> +{
> +	mutex_unlock(&module_mutex);
> +}
> +#else
> +static inline void lock_modules(void) { }
> +static inline void unlock_modules(void) { }
> +#endif

You don't need to add new #ifdefs. There is a room for dummy prototypes
for !CONFIG_MODULES already in modules.h.

-----
struct notifier_block;

#ifdef CONFIG_MODULES

extern int modules_disabled; /* for sysctl */

...
#else /* !CONFIG_MODULES... */

static inline struct module *__module_address(unsigned long addr)
{
-----

So you can just put those inlines in the appropriate places ;)

Thank you,

> +
>  #endif /* _LINUX_MODULE_H */
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index fa7687eb0c0e..b4f3c24cd2ef 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -573,7 +573,7 @@ static void kprobe_optimizer(struct work_struct *work)
>  	cpus_read_lock();
>  	mutex_lock(&text_mutex);
>  	/* Lock modules while optimizing kprobes */
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  
>  	/*
>  	 * Step 1: Unoptimize kprobes and collect cleaned (unused and disarmed)
> @@ -598,7 +598,7 @@ static void kprobe_optimizer(struct work_struct *work)
>  	/* Step 4: Free cleaned kprobes after quiesence period */
>  	do_free_cleaned_kprobes();
>  
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  	mutex_unlock(&text_mutex);
>  	cpus_read_unlock();
>  
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index f76fdb925532..d9d9d4973e6b 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -57,7 +57,7 @@ static void klp_find_object_module(struct klp_object *obj)
>  	if (!klp_is_module(obj))
>  		return;
>  
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	/*
>  	 * We do not want to block removal of patched modules and therefore
>  	 * we do not take a reference here. The patches are removed by
> @@ -74,7 +74,7 @@ static void klp_find_object_module(struct klp_object *obj)
>  	if (mod && mod->klp_alive)
>  		obj->mod = mod;
>  
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  }
>  
>  static bool klp_initialized(void)
> @@ -163,12 +163,12 @@ static int klp_find_object_symbol(const char *objname, const char *name,
>  		.pos = sympos,
>  	};
>  
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	if (objname)
>  		module_kallsyms_on_each_symbol(klp_find_callback, &args);
>  	else
>  		kallsyms_on_each_symbol(klp_find_callback, &args);
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  
>  	/*
>  	 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
> diff --git a/kernel/module.c b/kernel/module.c
> index 8adeb126b02c..3fd8686b1637 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -896,7 +896,7 @@ static void module_unload_free(struct module *mod)
>  {
>  	struct module_use *use, *tmp;
>  
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	list_for_each_entry_safe(use, tmp, &mod->target_list, target_list) {
>  		struct module *i = use->target;
>  		pr_debug("%s unusing %s\n", mod->name, i->name);
> @@ -905,7 +905,7 @@ static void module_unload_free(struct module *mod)
>  		list_del(&use->target_list);
>  		kfree(use);
>  	}
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  }
>  
>  #ifdef CONFIG_MODULE_FORCE_UNLOAD
> @@ -1025,7 +1025,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
>  	if (ret != 0)
>  		goto out;
>  
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  	/* Final destruction now no one is using it. */
>  	if (mod->exit != NULL)
>  		mod->exit();
> @@ -1044,7 +1044,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
>  	wake_up_all(&module_wq);
>  	return 0;
>  out:
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  	return ret;
>  }
>  
> @@ -1449,7 +1449,7 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
>  	 * in the wait_event_interruptible(), which is harmless.
>  	 */
>  	sched_annotate_sleep();
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	sym = find_symbol(name, &owner, &crc,
>  			  !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
>  	if (!sym)
> @@ -1476,7 +1476,7 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
>  	/* We must make copy under the lock if we failed to get ref. */
>  	strncpy(ownername, module_name(owner), MODULE_NAME_LEN);
>  unlock:
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  	return sym;
>  }
>  
> @@ -1731,10 +1731,10 @@ static void del_usage_links(struct module *mod)
>  #ifdef CONFIG_MODULE_UNLOAD
>  	struct module_use *use;
>  
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	list_for_each_entry(use, &mod->target_list, target_list)
>  		sysfs_remove_link(use->target->holders_dir, mod->name);
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  #endif
>  }
>  
> @@ -1744,14 +1744,14 @@ static int add_usage_links(struct module *mod)
>  #ifdef CONFIG_MODULE_UNLOAD
>  	struct module_use *use;
>  
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	list_for_each_entry(use, &mod->target_list, target_list) {
>  		ret = sysfs_create_link(use->target->holders_dir,
>  					&mod->mkobj.kobj, mod->name);
>  		if (ret)
>  			break;
>  	}
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  	if (ret)
>  		del_usage_links(mod);
>  #endif
> @@ -2177,9 +2177,9 @@ static void free_module(struct module *mod)
>  
>  	/* We leave it in list to prevent duplicate loads, but make sure
>  	 * that noone uses it while it's being deconstructed. */
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	mod->state = MODULE_STATE_UNFORMED;
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  
>  	/* Remove dynamic debug info */
>  	ddebug_remove_module(mod->name);
> @@ -2197,7 +2197,7 @@ static void free_module(struct module *mod)
>  		free_module_elf(mod);
>  
>  	/* Now we can delete it from the lists */
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	/* Unlink carefully: kallsyms could be walking list. */
>  	list_del_rcu(&mod->list);
>  	mod_tree_remove(mod);
> @@ -2205,7 +2205,7 @@ static void free_module(struct module *mod)
>  	module_bug_cleanup(mod);
>  	/* Wait for RCU-sched synchronizing before releasing mod->list and buglist. */
>  	synchronize_rcu();
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  
>  	/* This may be empty, but that's OK */
>  	module_arch_freeing_init(mod);
> @@ -3504,10 +3504,10 @@ static bool finished_loading(const char *name)
>  	 * in the wait_event_interruptible(), which is harmless.
>  	 */
>  	sched_annotate_sleep();
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	mod = find_module_all(name, strlen(name), true);
>  	ret = !mod || mod->state == MODULE_STATE_LIVE;
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  
>  	return ret;
>  }
> @@ -3619,7 +3619,7 @@ static noinline int do_init_module(struct module *mod)
>  
>  	ftrace_free_mem(mod, mod->init_layout.base, mod->init_layout.base +
>  			mod->init_layout.size);
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	/* Drop initial reference. */
>  	module_put(mod);
>  	trim_init_extable(mod);
> @@ -3651,7 +3651,7 @@ static noinline int do_init_module(struct module *mod)
>  	if (llist_add(&freeinit->node, &init_free_list))
>  		schedule_work(&init_free_wq);
>  
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  	wake_up_all(&module_wq);
>  
>  	return 0;
> @@ -3693,12 +3693,12 @@ static int add_unformed_module(struct module *mod)
>  	mod->state = MODULE_STATE_UNFORMED;
>  
>  again:
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	old = find_module_all(mod->name, strlen(mod->name), true);
>  	if (old != NULL) {
>  		if (old->state != MODULE_STATE_LIVE) {
>  			/* Wait in case it fails to load. */
> -			mutex_unlock(&module_mutex);
> +			unlock_modules();
>  			err = wait_event_interruptible(module_wq,
>  					       finished_loading(mod->name));
>  			if (err)
> @@ -3714,7 +3714,7 @@ static int add_unformed_module(struct module *mod)
>  	err = 0;
>  
>  out:
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  out_unlocked:
>  	return err;
>  }
> @@ -3723,7 +3723,7 @@ static int complete_formation(struct module *mod, struct load_info *info)
>  {
>  	int err;
>  
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  
>  	/* Find duplicate symbols (must be called under lock). */
>  	err = verify_exported_symbols(mod);
> @@ -3740,12 +3740,12 @@ static int complete_formation(struct module *mod, struct load_info *info)
>  	/* Mark state as coming so strong_try_module_get() ignores us,
>  	 * but kallsyms etc. can see us. */
>  	mod->state = MODULE_STATE_COMING;
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  
>  	return 0;
>  
>  out:
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  	return err;
>  }
>  
> @@ -3943,9 +3943,9 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  	klp_module_going(mod);
>   bug_cleanup:
>  	/* module_bug_cleanup needs module_mutex protection */
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	module_bug_cleanup(mod);
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  
>   ddebug_cleanup:
>  	ftrace_release_mod(mod);
> @@ -3959,14 +3959,14 @@ static int load_module(struct load_info *info, const char __user *uargs,
>   free_unload:
>  	module_unload_free(mod);
>   unlink_mod:
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	/* Unlink carefully: kallsyms could be walking list. */
>  	list_del_rcu(&mod->list);
>  	mod_tree_remove(mod);
>  	wake_up_all(&module_wq);
>  	/* Wait for RCU-sched synchronizing before releasing mod->list. */
>  	synchronize_rcu();
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>   free_module:
>  	/* Free lock-classes; relies on the preceding sync_rcu() */
>  	lockdep_free_key_range(mod->core_layout.base, mod->core_layout.size);
> @@ -4322,7 +4322,7 @@ static char *module_flags(struct module *mod, char *buf)
>  /* Called by the /proc file system to return a list of modules. */
>  static void *m_start(struct seq_file *m, loff_t *pos)
>  {
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	return seq_list_start(&modules, *pos);
>  }
>  
> @@ -4333,7 +4333,7 @@ static void *m_next(struct seq_file *m, void *p, loff_t *pos)
>  
>  static void m_stop(struct seq_file *m, void *p)
>  {
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  }
>  
>  static int m_show(struct seq_file *m, void *p)
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index aefb6065b508..710ec6a6aa8f 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -122,9 +122,9 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
>  	if (!p)
>  		return true;
>  	*p = '\0';
> -	mutex_lock(&module_mutex);
> +	lock_modules();
>  	ret = !!find_module(tk->symbol);
> -	mutex_unlock(&module_mutex);
> +	unlock_modules();
>  	*p = ':';
>  
>  	return ret;
> -- 
> 2.25.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>

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