Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 18 Jul 2023 10:02:46 +0900
From:   Masami Hiramatsu (Google) <mhiramat@kernel.org>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Martin KaFai Lau <martin.lau@linux.dev>, bpf@vger.kernel.org,
        Sven Schnelle <svens@linux.ibm.com>,
        Alexei Starovoitov <ast@kernel.org>
Subject: Re: [PATCH v2 2/9] bpf/btf: tracing: Move finding func-proto API
 and getting func-param API to BTF
Message-Id: <20230718100246.87e2ad49bfd8fa056b3db2ef@kernel.org>
In-Reply-To: <20230717195129.14759151@gandalf.local.home>
References: <168960739768.34107.15145201749042174448.stgit@devnote2>
        <168960741686.34107.6330273416064011062.stgit@devnote2>
        <20230717143914.5399a8e4@gandalf.local.home>
        <20230718084634.7746b16b470f5fa1b0d99521@kernel.org>
        <20230717195129.14759151@gandalf.local.home>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Mon, 17 Jul 2023 19:51:29 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue, 18 Jul 2023 08:46:34 +0900
> Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> 
> > > > + * Get function parameter with the number of parameters.
> > > > + * This can return NULL if the function has no parameters.  
> > > 
> > >   " It can return EINVAL if this function's parameters are NULL."  
> > 
> > No, as you can see the code, if btf_type_vlen(func_proto) returns 0 (means
> > the function proto type has no parameters), btf_get_func_param() returns
> > NULL. This is important point because user needs to use IS_ERR_OR_NULL(ret)
> > instead of IS_ERR(ret).
> 
> I didn't mean to replace what you had, I meant you left that part out. In
> other words, you have to check for IS_ERR_OR_NULL(ret), not just "!ret".

Ah, got it! Let me update it.

Thank you!

> 
> -- Steve
> 
> > >   
> > > > + */
> > > > +const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s32 *nr)
> > > > +{
> > > > +	if (!func_proto || !nr)
> > > > +		return ERR_PTR(-EINVAL);
> > > > +


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>