linux-kernel - Re: [patch V4 part 1 21/36] kprobes: Prevent probes in .noinstr.text section

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Message-Id: <20200508153005.1e53f54a85d19f007a950b44@kernel.org>
Date:   Fri, 8 May 2020 15:30:05 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [patch V4 part 1 21/36] kprobes: Prevent probes in
 .noinstr.text section

On Tue, 05 May 2020 15:16:23 +0200
Thomas Gleixner <tglx@...utronix.de> wrote:

> Instrumentation is forbidden in the .noinstr.text section. Make kprobes
> respect this.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

This looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thank you!


> ---
>  include/linux/module.h |    2 ++
>  kernel/kprobes.c       |   18 ++++++++++++++++++
>  kernel/module.c        |    3 +++
>  3 files changed, 23 insertions(+)
> 
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -458,6 +458,8 @@ struct module {
>  	void __percpu *percpu;
>  	unsigned int percpu_size;
>  #endif
> +	void *noinstr_text_start;
> +	unsigned int noinstr_text_size;
>  
>  #ifdef CONFIG_TRACEPOINTS
>  	unsigned int num_tracepoints;
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2229,6 +2229,12 @@ static int __init populate_kprobe_blackl
>  	/* Symbols in __kprobes_text are blacklisted */
>  	ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start,
>  					(unsigned long)__kprobes_text_end);
> +	if (ret)
> +		return ret;
> +
> +	/* Symbols in noinstr section are blacklisted */
> +	ret = kprobe_add_area_blacklist((unsigned long)__noinstr_text_start,
> +					(unsigned long)__noinstr_text_end);
>  
>  	return ret ? : arch_populate_kprobe_blacklist();
>  }
> @@ -2248,6 +2254,12 @@ static void add_module_kprobe_blacklist(
>  		end = start + mod->kprobes_text_size;
>  		kprobe_add_area_blacklist(start, end);
>  	}
> +
> +	start = (unsigned long)mod->noinstr_text_start;
> +	if (start) {
> +		end = start + mod->noinstr_text_size;
> +		kprobe_add_area_blacklist(start, end);
> +	}
>  }
>  
>  static void remove_module_kprobe_blacklist(struct module *mod)
> @@ -2265,6 +2277,12 @@ static void remove_module_kprobe_blackli
>  		end = start + mod->kprobes_text_size;
>  		kprobe_remove_area_blacklist(start, end);
>  	}
> +
> +	start = (unsigned long)mod->noinstr_text_start;
> +	if (start) {
> +		end = start + mod->noinstr_text_size;
> +		kprobe_remove_area_blacklist(start, end);
> +	}
>  }
>  
>  /* Module notifier call back, checking kprobes on the module */
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3150,6 +3150,9 @@ static int find_module_sections(struct m
>  	}
>  #endif
>  
> +	mod->noinstr_text_start = section_objs(info, ".noinstr.text", 1,
> +						&mod->noinstr_text_size);
> +
>  #ifdef CONFIG_TRACEPOINTS
>  	mod->tracepoints_ptrs = section_objs(info, "__tracepoints_ptrs",
>  					     sizeof(*mod->tracepoints_ptrs),
> 


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