linux-kernel - Re: [PATCH v5 1/6] kprobes: Remove dependency to the module

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Message-Id: <20200724234631.40f4ffec6adae57ac3df8ea3@kernel.org>
Date:   Fri, 24 Jul 2020 23:46:31 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        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>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v5 1/6] kprobes: Remove dependency to the module_mutex

On Fri, 24 Jul 2020 08:05:48 +0300
Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> wrote:

> Add lock_modules() and unlock_modules() wrappers for acquiring module_mutex
> in order to remove the compile time dependency to it.

This subject is a bit confusing. This is just wrapping modules_mutex in
kpprobes. We still have compile time dependency, e.g. module_state, right?

Thank you,

> 
> Cc: linux-mm@...ck.org
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Suggested-by: Masami Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
>  include/linux/module.h      | 18 ++++++++++++++++++
>  kernel/kprobes.c            |  4 ++--
>  kernel/trace/trace_kprobe.c |  4 ++--
>  3 files changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 2e6670860d27..8850b9692b8f 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -705,6 +705,16 @@ static inline bool is_livepatch_module(struct module *mod)
>  bool is_module_sig_enforced(void);
>  void set_module_sig_enforced(void);
>  
> +static inline void lock_modules(void)
> +{
> +	mutex_lock(&module_mutex);
> +}
> +
> +static inline void unlock_modules(void)
> +{
> +	mutex_unlock(&module_mutex);
> +}
> +
>  #else /* !CONFIG_MODULES... */
>  
>  static inline struct module *__module_address(unsigned long addr)
> @@ -852,6 +862,14 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr)
>  	return ptr;
>  }
>  
> +static inline void lock_modules(void)
> +{
> +}
> +
> +static inline void unlock_modules(void)
> +{
> +}
> +
>  #endif /* CONFIG_MODULES */
>  
>  #ifdef CONFIG_SYSFS
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 2e97febeef77..4e46d96d4e16 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -564,7 +564,7 @@ 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)
> @@ -589,7 +589,7 @@ 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/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>