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;
Message-ID: <e6cd1909-2776-28d2-ccc0-4b3d2d09e9ce@intel.com>
Date:   Fri, 26 May 2023 14:17:20 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.11.0
Subject: Re: [PATCH v2] x86/lib: Do not use local symbols with
 SYM_CODE_START_LOCAL()
Content-Language: en-US
To:     Nadav Amit <nadav.amit@gmail.com>, Borislav Petkov <bp@alien8.de>
Cc:     Jiri Slaby <jirislaby@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
References: <20230525184244.2311-1-namit@vmware.com>
 <38e24fd4-9213-229d-9919-7ae3bfb113bb@intel.com>
 <24E47178-C177-425F-A8EF-CFFAE22597D4@gmail.com>
 <20230526155336.GAZHDWAFi1FRqq83TP@nazgul.local>
 <0F07EEDB-8A3F-4224-9FF1-43A5300B1B8B@gmail.com>
 <20230526204559.GAZHEahxxnQaHhSUul@nazgul.local>
 <D63AB9E6-BA52-4E24-B8EF-C7B9DB1595CC@gmail.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <D63AB9E6-BA52-4E24-B8EF-C7B9DB1595CC@gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 5/26/23 14:10, Nadav Amit wrote:
>>> I did not ask to make them global. Just to keep them as local after
>>> linkage in the executable, like all other functions in the kernel.
>> Ok, not global. But local and present in the symbol table:
>>
>> 105185: ffffffff81b89330    17 NOTYPE  LOCAL  DEFAULT    1 bad_get_user_clac
>>
>> And again, this helps how exactly?
> Allowing debuggers, tracers, disassemblers and instrumentation tools to
> work the same way they work as they work with any other piece of code in
> the kernel.
> 
> I personally work on code instrumentation and this makes my life hard for
> no good reason.
> 
> [ Perhaps the question should go the other way around: why addresses of
> code in these functions should not be mapped to any symbol? ]

Nadav, is there a chance you could give us a real-life example of how
this affects you as an end user?  What's a specific tool that you were
using or a specific problem that you were trying to solve where these
local symbols caused a problem?  How would the global symbol have helped?

I can certainly _imagine_ some, but I'm curious what you saw that
prompted you to send this patch.