Re: [RFC][PATCH -tip 8/9] kprobes: support respawn probes formodule probing
From: Frederic Weisbecker
Date: Thu Mar 19 2009 - 21:19:50 EST
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@xxxxxxxxxx>
> Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
> ---
> 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 *);
>
> 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)
> +{
> +}
> #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;
> + };
> +};
> +
> +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)) {
I don't see a place where you check if pc->handler != NULL
May be you could attach a stub in such cases.
Frederic.
> + 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@xxxxxxxxxx
>
>
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