linux-kernel - Re: [PATCH 11/12] [v4] kallsyms: rework symbol lookup return codes

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Date: Tue, 26 Mar 2024 13:06:47 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: linux-kbuild@...r.kernel.org, Masahiro Yamada <masahiroy@...nel.org>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
 <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Masami
 Hiramatsu <mhiramat@...nel.org>, Luis Chamberlain <mcgrof@...nel.org>,
 Nicolas Schier <nicolas@...sle.eu>, Nathan Chancellor <nathan@...nel.org>,
 Arnd Bergmann <arnd@...db.de>, Eduard Zingerman <eddyz87@...il.com>, Song
 Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, Kees Cook
 <keescook@...omium.org>, bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, linux-modules@...r.kernel.org
Subject: Re: [PATCH 11/12] [v4] kallsyms: rework symbol lookup return codes

On Tue, 26 Mar 2024 15:53:38 +0100
Arnd Bergmann <arnd@...nel.org> wrote:

> -const char *
> +int
>  ftrace_mod_address_lookup(unsigned long addr, unsigned long *size,
>  		   unsigned long *off, char **modname, char *sym)
>  {
>  	struct ftrace_mod_map *mod_map;
> -	const char *ret = NULL;
> +	int ret;

This needs to be ret = 0;

>  
>  	/* mod_map is freed via call_rcu() */
>  	preempt_disable();

As here we have:

	list_for_each_entry_rcu(mod_map, &ftrace_mod_maps, list) {
		ret = ftrace_func_address_lookup(mod_map, addr, size, off, sym);
		if (ret) {
			if (modname)
				*modname = mod_map->mod->name;
			break;
		}
	}
	preempt_enable();

	return ret;
}

Where it is possible for the loop never to be executed.

-- Steve