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Date:	Fri, 20 Mar 2009 02:11:15 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Jim Keniston <jkenisto@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	systemtap-ml <systemtap@...rces.redhat.com>
Subject: Re: [RFC][PATCH -tip 8/9] kprobes: support respawn probes for
	module probing

On Thu, Mar 19, 2009 at 05:10:44PM -0400, Masami Hiramatsu wrote:
> Add module_*probe API's to respawn probes on kernel modules.
> kprobes which have been registered through register_module_*probe are
> activated when the target module is loaded, and deactivated when unloading.
> register_module_*probe require an activate_handler which is called right
> before activating the probe, and if it returns !0, kprobes will be activated.
> 
> Thus, users can check whether the target module is true target or not
> (e.g. checking build-id) in activate_handler.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
> ---
>  include/linux/kprobes.h |   39 ++++++++
>  kernel/kprobes.c        |  250 +++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 289 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> index 2ec6cc1..9d47d08 100644
> --- a/include/linux/kprobes.h
> +++ b/include/linux/kprobes.h
> @@ -37,6 +37,7 @@
>  #include <linux/spinlock.h>
>  #include <linux/rcupdate.h>
>  #include <linux/mutex.h>
> +#include <linux/module.h>
> 
>  #ifdef CONFIG_KPROBES
>  #include <asm/kprobes.h>
> @@ -69,6 +70,7 @@ typedef int (*kprobe_fault_handler_t) (struct kprobe *, struct pt_regs *,
>  				       int trapnr);
>  typedef int (*kretprobe_handler_t) (struct kretprobe_instance *,
>  				    struct pt_regs *);
> +typedef int (*probe_activate_handler_t)(void *, struct module *);


I guess it could also be useful to call the handler when the module
is unloaded. Be using another parameter with a LOAD/UNLOAD enum value.


> 
>  struct kprobe {
>  	struct hlist_node hlist;
> @@ -279,6 +281,16 @@ void unregister_kretprobes(struct kretprobe **rps, int num);
>  void kprobe_flush_task(struct task_struct *tk);
>  void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);
> 
> +int register_module_kprobe(struct kprobe *kp,
> +			   probe_activate_handler_t handler, void *data);
> +int register_module_kretprobe(struct kretprobe *rp,
> +			      probe_activate_handler_t handler, void *data);
> +int register_module_jprobe(struct jprobe *jp,
> +			   probe_activate_handler_t handler, void *data);
> +void unregister_module_kprobe(struct kprobe *kp);
> +void unregister_module_kretprobe(struct kretprobe *rp);
> +void unregister_module_jprobe(struct jprobe *jp);
> +
>  #else /* !CONFIG_KPROBES: */
> 
>  static inline int kprobes_built_in(void)
> @@ -345,5 +357,32 @@ static inline void unregister_kretprobes(struct kretprobe **rps, int num)
>  static inline void kprobe_flush_task(struct task_struct *tk)
>  {
>  }
> +static inline int register_module_kprobe(struct kprobe *kp,
> +					 probe_activate_handler_t handler,
> +					 void *data)
> +{
> +	return -ENOSYS;
> +}
> +static inline int register_module_kretprobe(struct kretprobe *rp,
> +					    probe_activate_handler_t handler,
> +					    void *data)
> +{
> +	return -ENOSYS;
> +}
> +static inline int register_module_jprobe(struct jprobe *jp,
> +					 probe_activate_handler_t handler,
> +					 void *data)
> +{
> +	return -ENOSYS;
> +}
> +void unregister_module_kprobe(struct kprobe *kp)
> +{
> +}
> +void unregister_module_kretprobe(struct kretprobe *rp)
> +{
> +}
> +void unregister_module_jprobe(struct jprobe *jp)
> +{
> +}


Shouldn't the unregister_* be inlined too?
I think they all could be static inlined too in case of !CONFIG_MODULE


>  #endif /* CONFIG_KPROBES */
>  #endif /* _LINUX_KPROBES_H */
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 5016bfb..f16a54e 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1416,6 +1416,256 @@ static int __kprobes debugfs_kprobe_init(void)
>  late_initcall(debugfs_kprobe_init);
>  #endif /* CONFIG_DEBUG_FS */
> 
> +/* Kprobes module respawn support */
> +enum probe_type {
> +	PROBE_TYPE_KPROBE,
> +	PROBE_TYPE_KRETPROBE,
> +	PROBE_TYPE_JPROBE,
> +};
> +
> +struct module_probe_client {
> +	struct list_head list;
> +	const char *module;	/* including symbol name */
> +	int active;
> +	void *data;
> +	probe_activate_handler_t handler;
> +	enum probe_type type;
> +	union {
> +		struct kprobe *kp;
> +		struct kretprobe *rp;
> +		struct jprobe *jp;
> +	};
> +};


#ifdef CONFIG_MODULE ?

Frederic.

> +static DEFINE_MUTEX(module_probe_mutex);
> +static LIST_HEAD(module_probe_list);
> +
> +static int activate_module_probe(struct module_probe_client *pc)
> +{
> +	int ret = 0;
> +	if (pc->active)
> +		return 0;
> +	switch (pc->type) {
> +	case PROBE_TYPE_KPROBE:
> +		ret = register_kprobe(pc->kp);
> +		break;
> +	case PROBE_TYPE_KRETPROBE:
> +		ret = register_kretprobe(pc->rp);
> +		break;
> +	case PROBE_TYPE_JPROBE:
> +		ret = register_jprobe(pc->jp);
> +		break;
> +	default:
> +		WARN_ON(1);
> +		break;
> +	}
> +	if (!ret)
> +		pc->active = 1;
> +	return ret;
> +}
> +
> +static void deactivate_module_probe(struct module_probe_client *pc)
> +{
> +	if (!pc->active)
> +		return;
> +	switch (pc->type) {
> +	case PROBE_TYPE_KPROBE:
> +		unregister_kprobe(pc->kp);
> +		break;
> +	case PROBE_TYPE_KRETPROBE:
> +		unregister_kretprobe(pc->rp);
> +		break;
> +	case PROBE_TYPE_JPROBE:
> +		unregister_jprobe(pc->jp);
> +		break;
> +	default:
> +		WARN_ON(1);
> +		break;
> +	}
> +	pc->active = 0;
> +}
> +
> +static const char *probed_module_name(struct kprobe *kp)
> +{
> +	if ((kp->symbol_name) && strchr(kp->symbol_name, ':'))
> +		return kp->symbol_name;
> +	return NULL;
> +}
> +
> +static int module_is_exist(const char *module)
> +{
> +	char buf[MODULE_NAME_LEN + 8];
> +	snprintf(buf, MODULE_NAME_LEN + 8, "%s:__stext", module);
> +	return module_kallsyms_lookup_name(buf) ? 1 : 0;
> +}
> +
> +static int add_module_probe(const char *module, void *p, enum probe_type type,
> +			    probe_activate_handler_t handler, void *data)
> +{
> +	struct module_probe_client *pc;
> +	int ret = 0;
> +
> +	if (!handler)
> +		return -EINVAL;
> +
> +	pc = kzalloc(sizeof(struct module_probe_client), GFP_KERNEL);
> +	pc->kp = p;
> +	pc->type = type;
> +	pc->module = module;
> +	pc->handler = handler;
> +	pc->data = data;
> +	INIT_LIST_HEAD(&pc->list);
> +
> +	mutex_lock(&module_probe_mutex);
> +	if (module_is_exist(module))
> +		ret = activate_module_probe(pc);
> +	if (ret)
> +		kfree(pc);
> +	else
> +		list_add_tail(&pc->list, &module_probe_list);
> +	mutex_unlock(&module_probe_mutex);
> +	return ret;
> +}
> +
> +static void __del_module_probe(struct module_probe_client *pc)
> +{
> +	list_del(&pc->list);
> +	deactivate_module_probe(pc);
> +	kfree(pc);
> +}
> +
> +static int del_module_probe(void *p)
> +{
> +	struct module_probe_client *pc;
> +	int ret;
> +
> +	mutex_lock(&module_probe_mutex);
> +	list_for_each_entry(pc, &module_probe_list, list)
> +		if (pc->kp == p) {
> +			/* don't need safe loop, we exit soon */
> +			__del_module_probe(pc);
> +			goto found;
> +		}
> +	ret = -ENOENT;
> +found:
> +	mutex_unlock(&module_probe_mutex);
> +	return ret;
> +}
> +
> +int __kprobes
> +register_module_kprobe(struct kprobe *kp,
> +		       probe_activate_handler_t handler, void *data)
> +{
> +	const char *module;
> +	module = probed_module_name(kp);
> +	if (!module)
> +		return register_kprobe(kp);
> +	return add_module_probe(module, kp, PROBE_TYPE_KPROBE,
> +				handler, data);
> +}
> +EXPORT_SYMBOL_GPL(register_module_kprobe);
> +
> +int __kprobes
> +register_module_kretprobe(struct kretprobe *rp,
> +			  probe_activate_handler_t handler, void *data)
> +{
> +	const char *module;
> +	module = probed_module_name(&rp->kp);
> +	if (!module)
> +		return register_kretprobe(rp);
> +	return add_module_probe(module, rp, PROBE_TYPE_KRETPROBE,
> +				handler, data);
> +}
> +EXPORT_SYMBOL_GPL(register_module_kretprobe);
> +
> +int __kprobes
> +register_module_jprobe(struct jprobe *jp,
> +		       probe_activate_handler_t handler, void *data)
> +{
> +	const char *module;
> +	module = probed_module_name(&jp->kp);
> +	if (!module)
> +		return register_jprobe(jp);
> +	return add_module_probe(module, jp, PROBE_TYPE_JPROBE,
> +				handler, data);
> +}
> +EXPORT_SYMBOL_GPL(register_module_jprobe);
> +
> +void __kprobes unregister_module_kprobe(struct kprobe *kp)
> +{
> +	const char *module;
> +	module = probed_module_name(kp);
> +	if (!module)
> +		unregister_kprobe(kp);
> +	else
> +		del_module_probe(kp);
> +}
> +EXPORT_SYMBOL_GPL(unregister_module_kprobe);
> +
> +void __kprobes unregister_module_kretprobe(struct kretprobe *rp)
> +{
> +	const char *module;
> +	module = probed_module_name(&rp->kp);
> +	if (!module)
> +		unregister_kretprobe(rp);
> +	else
> +		del_module_probe(rp);
> +}
> +EXPORT_SYMBOL_GPL(unregister_module_kretprobe);
> +
> +void __kprobes unregister_module_jprobe(struct jprobe *jp)
> +{
> +	const char *module;
> +	module = probed_module_name(&jp->kp);
> +	if (!module)
> +		unregister_jprobe(jp);
> +	else
> +		del_module_probe(jp);
> +}
> +EXPORT_SYMBOL_GPL(unregister_module_jprobe);
> +
> +static int module_is_probed(const char *mod, const char *sym)
> +{
> +	int len = strlen(mod);
> +	return strncmp(mod, sym, len) == 0 && sym[len] == ':';
> +}
> +
> +static int module_probe_callback(struct notifier_block *nb,
> +				 unsigned long state, void *module)
> +{
> +	struct module_probe_client *pc;
> +	struct module *mod = module;
> +	if (state == MODULE_STATE_LIVE)
> +		return NOTIFY_DONE;
> +
> +	mutex_lock(&module_probe_mutex);
> +	list_for_each_entry(pc, &module_probe_list, list) {
> +		if (!module_is_probed(mod->name, pc->module))
> +			continue;
> +		if (state == MODULE_STATE_COMING &&
> +		    pc->handler(pc->data, module)) {
> +			activate_module_probe(pc);
> +		} else if (state == MODULE_STATE_GOING)
> +			deactivate_module_probe(pc);
> +	}
> +	mutex_unlock(&module_probe_mutex);
> +	return NOTIFY_DONE;
> +}
> +
> +struct notifier_block module_probe_nb = {
> +	.notifier_call = module_probe_callback
> +};
> +
> +static int __init init_module_probes(void)
> +{
> +	int ret;
> +	ret = register_module_notifier(&module_probe_nb);
> +	if (ret)
> +		pr_warning("Failed to register module notifier\n");
> +	return ret;
> +}
> +module_init(init_module_probes);
> +
>  module_init(init_kprobes);
> 
>  EXPORT_SYMBOL_GPL(register_kprobe);
> -- 
> Masami Hiramatsu
> 
> Software Engineer
> Hitachi Computer Products (America) Inc.
> Software Solutions Division
> 
> e-mail: mhiramat@...hat.com
> 
> 
> --
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