linux-kernel - Re: [patch V4 part 1 16/36] kprobes: Support _

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Date:   Wed, 6 May 2020 17:47:36 +0200
From:   Alexandre Chartre <alexandre.chartre@...cle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        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 16/36] kprobes: Support __kprobes blacklist in
 modules


On 5/5/20 3:16 PM, Thomas Gleixner wrote:
> From: Masami Hiramatsu <mhiramat@...nel.org>
> 
> Support __kprobes attribute for blacklist functions in modules.  The
> __kprobes attribute functions are stored in .kprobes.text section.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Link: https://lkml.kernel.org/r/158523418821.24735.15379873028352411526.stgit@devnote2
> 
> ---
>   include/linux/module.h |    4 ++++
>   kernel/kprobes.c       |   42 ++++++++++++++++++++++++++++++++++++++++++
>   kernel/module.c        |    4 ++++
>   3 files changed, 50 insertions(+)

Reviewed-by: Alexandre Chartre <alexandre.chartre@...cle.com>

alex.

> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -489,6 +489,10 @@ struct module {
>   	unsigned int num_ftrace_callsites;
>   	unsigned long *ftrace_callsites;
>   #endif
> +#ifdef CONFIG_KPROBES
> +	void *kprobes_text_start;
> +	unsigned int kprobes_text_size;
> +#endif
>   
>   #ifdef CONFIG_LIVEPATCH
>   	bool klp; /* Is this a livepatch module? */
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2179,6 +2179,19 @@ int kprobe_add_area_blacklist(unsigned l
>   	return 0;
>   }
>   
> +/* Remove all symbols in given area from kprobe blacklist */
> +static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end)
> +{
> +	struct kprobe_blacklist_entry *ent, *n;
> +
> +	list_for_each_entry_safe(ent, n, &kprobe_blacklist, list) {
> +		if (ent->start_addr < start || ent->start_addr >= end)
> +			continue;
> +		list_del(&ent->list);
> +		kfree(ent);
> +	}
> +}
> +
>   int __init __weak arch_populate_kprobe_blacklist(void)
>   {
>   	return 0;
> @@ -2215,6 +2228,28 @@ static int __init populate_kprobe_blackl
>   	return ret ? : arch_populate_kprobe_blacklist();
>   }
>   
> +static void add_module_kprobe_blacklist(struct module *mod)
> +{
> +	unsigned long start, end;
> +
> +	start = (unsigned long)mod->kprobes_text_start;
> +	if (start) {
> +		end = start + mod->kprobes_text_size;
> +		kprobe_add_area_blacklist(start, end);
> +	}
> +}
> +
> +static void remove_module_kprobe_blacklist(struct module *mod)
> +{
> +	unsigned long start, end;
> +
> +	start = (unsigned long)mod->kprobes_text_start;
> +	if (start) {
> +		end = start + mod->kprobes_text_size;
> +		kprobe_remove_area_blacklist(start, end);
> +	}
> +}
> +
>   /* Module notifier call back, checking kprobes on the module */
>   static int kprobes_module_callback(struct notifier_block *nb,
>   				   unsigned long val, void *data)
> @@ -2225,6 +2260,11 @@ static int kprobes_module_callback(struc
>   	unsigned int i;
>   	int checkcore = (val == MODULE_STATE_GOING);
>   
> +	if (val == MODULE_STATE_COMING) {
> +		mutex_lock(&kprobe_mutex);
> +		add_module_kprobe_blacklist(mod);
> +		mutex_unlock(&kprobe_mutex);
> +	}
>   	if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
>   		return NOTIFY_DONE;
>   
> @@ -2255,6 +2295,8 @@ static int kprobes_module_callback(struc
>   				kill_kprobe(p);
>   			}
>   	}
> +	if (val == MODULE_STATE_GOING)
> +		remove_module_kprobe_blacklist(mod);
>   	mutex_unlock(&kprobe_mutex);
>   	return NOTIFY_DONE;
>   }
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3194,6 +3194,10 @@ static int find_module_sections(struct m
>   					    sizeof(*mod->ei_funcs),
>   					    &mod->num_ei_funcs);
>   #endif
> +#ifdef CONFIG_KPROBES
> +	mod->kprobes_text_start = section_objs(info, ".kprobes.text", 1,
> +						&mod->kprobes_text_size);
> +#endif
>   	mod->extable = section_objs(info, "__ex_table",
>   				    sizeof(*mod->extable), &mod->num_exentries);
>   
>