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Message-ID: <49C31206.3060806@redhat.com>
Date: Thu, 19 Mar 2009 23:48:22 -0400
From: Masami Hiramatsu <mhiramat@...hat.com>
To: Frederic Weisbecker <fweisbec@...il.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
Frederic Weisbecker wrote:
>> 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.
Please see add_module_probe(), handler == NULL case returns -EINVAL,
and module_probe_list is internal list. So, pc->handler never be NULL.
Thank you,
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: mhiramat@...hat.com
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