linux-kernel - Re: [PATCH v3 4/4] tracing: move tracing declarations from kernel.h to a dedicated header

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <40a8e17e-4ec3-4123-8d7d-565afd9701b9@infradead.org>
Date: Wed, 17 Dec 2025 21:59:40 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Yury Norov <yury.norov@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Christophe Leroy <chleroy@...nel.org>, Ingo Molnar <mingo@...nel.org>,
 Jani Nikula <jani.nikula@...ux.intel.com>,
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
 David Laight <david.laight@...box.com>, Petr Pavlu <petr.pavlu@...e.com>,
 Andi Shyti <andi.shyti@...nel.org>, Rodrigo Vivi <rodrigo.vivi@...el.com>,
 Tvrtko Ursulin <tursulin@...ulin.net>, Daniel Gomez <da.gomez@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>,
 linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-modules@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v3 4/4] tracing: move tracing declarations from kernel.h
 to a dedicated header

On 12/17/25 7:59 PM, Yury Norov wrote:
> On Tue, Dec 16, 2025 at 09:24:55PM -0800, Randy Dunlap wrote:
>> [adding Kees]
>>
>> On 12/16/25 4:13 PM, Andrew Morton wrote:
>>> On Fri,  5 Dec 2025 12:52:35 -0500 "Yury Norov (NVIDIA)" <yury.norov@...il.com> wrote:
>>>
>>>> Tracing is a half of the kernel.h in terms of LOCs, although it's
>>>> a self-consistent part. It is intended for quick debugging purposes
>>>> and isn't used by the normal tracing utilities.
>>>>
>>>> Move it to a separate header. If someone needs to just throw a
>>>> trace_printk() in their driver, they will not have to pull all
>>>> the heavy tracing machinery.
>>>>
>>>> This is a pure move, except for removing a few 'extern's.
>>>>
>>
>> Hm, for a pure move, this shouldn't be necessary. Anyway, not using
>> FORTIFY in purgatory.o fixes this build error.
>> Or maybe there's a better answer.
>>
>> ---
>>  arch/x86/purgatory/Makefile |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> --- a/arch/x86/purgatory/Makefile
>> +++ b/arch/x86/purgatory/Makefile
>> @@ -62,7 +62,7 @@ PURGATORY_CFLAGS_REMOVE		+= $(CC_FLAGS_C
>>  endif
>>  
>>  CFLAGS_REMOVE_purgatory.o	+= $(PURGATORY_CFLAGS_REMOVE)
>> -CFLAGS_purgatory.o		+= $(PURGATORY_CFLAGS)
>> +CFLAGS_purgatory.o		+= $(PURGATORY_CFLAGS) -D__NO_FORTIFY
>>  
>>  CFLAGS_REMOVE_sha256.o		+= $(PURGATORY_CFLAGS_REMOVE)
>>  CFLAGS_sha256.o			+= $(PURGATORY_CFLAGS)
> 
> That happened because the new trace_printk.h includes string.h for
> strlen(), so all kernel.h users now indirectly include it, and it
> causes, seemingly, a circular dependency if FORTIFY is enabled.
> 
> A fix would be dropping trace_printk.h from kernel.h, or switching the
> only user of string.h, trace_puts(), to __builtin_strlen().
> 
> Notice, Andy has concerned about this on the previous round, and also
> suggested __builtin_strlen():
> 
>         https://lkml.org/lkml/2025/12/3/910
> 
> I deem to drop trace_printk.h from kernel.h - it is more aligned with
> the idea of unloading the header. The original motivation to keep
> trace_printk.h in kernel.h was just because a similar printk.h is living
> there. But after all, this is a purely debugging header, so no need for
> almost every C file to bear debugging stuff.
> 
> I can actually do both - switch to an intrinsic and drop the header.
> 
> Guys, please let me know what do you thing.

There are some problems with using __builtin_mem{cpy,set} -- don't
know about __builtin_str{whatever}. See

commit 4ce97317f41d
Author: Nick Desaulniers <nick.desaulniers+lkml@...il.com>
Date:   Wed Aug 7 15:15:32 2019 -0700
    x86/purgatory: Do not use __builtin_memcpy and __builtin_memset

We should drop the header from kernel.h soon anyway, whether now or
in a few weeks/months. IMHO.

-- 
~Randy