Re: [PATCH] Return proper error code from register_kprobe()

Re: [PATCH] Return proper error code from register_kprobe()

[Masami Hiramatsu]

(2012/02/14 19:53), Prashanth Nageshappa wrote:
> register_kprobe() aborts if the address of the new request falls in a prohibited
> area (such as ftrace pouch, __kprobes annotated functions, non-kernel text
> addresses, jump label text). We however don't return the right error on this
> abort, resulting in incorrect adding/reporting of kprobes (Ex: 'perf probe
> do_fork+18' or 'perf probe mcount')

OK, I see.

> 
> This patch fixes it by returning -EINVAL upon failure.
> 
> Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
> Signed-off-by: Prashanth K Nageshappa<prashanth@linux.vnet.ibm.com>

However, I can't agree with this change :(, because this
ignores possibilities of -ENOENT error code in other error
paths.

What I'm expecting is, setup an error code where the error
occurs, as below;

        jump_label_lock();
        preempt_disable();
        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))
+           jump_label_text_reserved(p->addr, p->addr)) {
+		ret = -EINVAL;
                goto fail_with_jump_label;
+	}

IMHO, we should change the label name too...

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com