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

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Date:   Fri, 24 Jul 2020 11:13:19 +0200
From:   Ingo Molnar <mingo@...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


* 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.
> 
> 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)
> +{
> +}

Minor namespace nit: when introducing new locking wrappers please 
standardize on the XYZ_lock()/XYZ_unlock() nomenclature, i.e.:

	modules_lock()
	...
	modules_unlock()

Similarly to the mutex_lock/unlock(&module_mutex) API that it is 
wrapping.

Also, JFYI, the overwhelming majority of the modules related APIs use 
module_*(), i.e. singular - not plural, so 
module_lock()/module_unlock() would be the more canonical choice. 
(But both sound fine to me)

Thanks,

	Ingo