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    Subject[RFC PATCH -tip 6/9] kprobes: cleanup to separate probe-able check
    Date
    Separate probe-able address checking code from
    register_kprobe().

    Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    ---

    kernel/kprobes.c | 82 ++++++++++++++++++++++++++++++------------------------
    1 files changed, 45 insertions(+), 37 deletions(-)

    diff --git a/kernel/kprobes.c b/kernel/kprobes.c
    index 7a8a122..6137fe3 100644
    --- a/kernel/kprobes.c
    +++ b/kernel/kprobes.c
    @@ -1313,67 +1313,80 @@ static inline int check_kprobe_rereg(struct kprobe *p)
    return ret;
    }

    -int __kprobes register_kprobe(struct kprobe *p)
    +static __kprobes int check_kprobe_address_safe(struct kprobe *p,
    + struct module **probed_mod)
    {
    int ret = 0;
    - struct kprobe *old_p;
    - struct module *probed_mod;
    - kprobe_opcode_t *addr;
    -
    - addr = kprobe_addr(p);
    - if (IS_ERR(addr))
    - return PTR_ERR(addr);
    - p->addr = addr;
    -
    - ret = check_kprobe_rereg(p);
    - if (ret)
    - return ret;

    jump_label_lock();
    preempt_disable();
    +
    + /* Ensure it is not in reserved area nor out of text */
    if (!kernel_text_address((unsigned long) p->addr) ||
    in_kprobes_functions((unsigned long) p->addr) ||
    ftrace_text_reserved(p->addr, p->addr) ||
    jump_label_text_reserved(p->addr, p->addr)) {
    ret = -EINVAL;
    - goto cannot_probe;
    + goto out;
    }

    - /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
    - p->flags &= KPROBE_FLAG_DISABLED;
    -
    - /*
    - * Check if are we probing a module.
    - */
    - probed_mod = __module_text_address((unsigned long) p->addr);
    - if (probed_mod) {
    - /* Return -ENOENT if fail. */
    - ret = -ENOENT;
    + /* Check if are we probing a module */
    + *probed_mod = __module_text_address((unsigned long) p->addr);
    + if (*probed_mod) {
    /*
    * We must hold a refcount of the probed module while updating
    * its code to prohibit unexpected unloading.
    */
    - if (unlikely(!try_module_get(probed_mod)))
    - goto cannot_probe;
    + if (unlikely(!try_module_get(*probed_mod))) {
    + ret = -ENOENT;
    + goto out;
    + }

    /*
    * If the module freed .init.text, we couldn't insert
    * kprobes in there.
    */
    - if (within_module_init((unsigned long)p->addr, probed_mod) &&
    - probed_mod->state != MODULE_STATE_COMING) {
    - module_put(probed_mod);
    - goto cannot_probe;
    + if (within_module_init((unsigned long)p->addr, *probed_mod) &&
    + (*probed_mod)->state != MODULE_STATE_COMING) {
    + module_put(*probed_mod);
    + *probed_mod = NULL;
    + ret = -ENOENT;
    }
    - /* ret will be updated by following code */
    }
    +out:
    preempt_enable();
    jump_label_unlock();

    + return ret;
    +}
    +
    +int __kprobes register_kprobe(struct kprobe *p)
    +{
    + int ret;
    + struct kprobe *old_p;
    + struct module *probed_mod;
    + kprobe_opcode_t *addr;
    +
    + /* Adjust probe address from symbol */
    + addr = kprobe_addr(p);
    + if (IS_ERR(addr))
    + return PTR_ERR(addr);
    + p->addr = addr;
    +
    + ret = check_kprobe_rereg(p);
    + if (ret)
    + return ret;
    +
    + /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
    + p->flags &= KPROBE_FLAG_DISABLED;
    p->nmissed = 0;
    INIT_LIST_HEAD(&p->list);
    - mutex_lock(&kprobe_mutex);

    + ret = check_kprobe_address_safe(p, &probed_mod);
    + if (ret)
    + return ret;
    +
    + mutex_lock(&kprobe_mutex);
    jump_label_lock(); /* needed to call jump_label_text_reserved() */

    get_online_cpus(); /* For avoiding text_mutex deadlock. */
    @@ -1410,11 +1423,6 @@ out:
    module_put(probed_mod);

    return ret;
    -
    -cannot_probe:
    - preempt_enable();
    - jump_label_unlock();
    - return ret;
    }
    EXPORT_SYMBOL_GPL(register_kprobe);



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