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Date:   Wed, 27 Jan 2021 11:02:26 +0900
From:   Masami Hiramatsu <mhiramat@kernel.org>
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Jianlin Lv <Jianlin.Lv@arm.com>, mingo@redhat.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] tracing: precise log info for kretprobe addr err
Message-Id: <20210127110226.a65b3e8c66eeab6ee63f8aee@kernel.org>
In-Reply-To: <20210126202058.GC12469@redhat.com>
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        <20210125181926.GA10248@redhat.com>
        <20210125133840.511b1496@gandalf.local.home>
        <20210126131536.f6e3a737a7b948799084fa7a@kernel.org>
        <20210126202058.GC12469@redhat.com>
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On Tue, 26 Jan 2021 21:20:59 +0100
Oleg Nesterov <oleg@redhat.com> wrote:

> On 01/26, Masami Hiramatsu wrote:
> >
> > > >
> > > > IOW, the "offset != 0" check removed by this patch is obviously wrong, right?
> > > >
> >
> > No, not wrong. Even offset != 0, if the symbol exists in the kernel,
> > kprobe_on_func_entry() will check it.
> 
> Yes, but unless I am totally confused... if kprobe_on_func_entry() returns false,
> then trace_kprobe_create() should fail with BAD_RETPROBE even if offset == 0 ?

Yes, if kprobe_on_func_entry() returns false, register_kretprobe() also returns
an error.

-----
int register_kretprobe(struct kretprobe *rp)
{
        int ret = 0;
        struct kretprobe_instance *inst;
        int i;
        void *addr;

        if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset))
                return -EINVAL;

-----

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>