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Date: Mon, 23 Jan 2023 16:23:21 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Dan Carpenter <error27@gmail.com>
Cc: oe-kbuild@lists.linux.dev, lkp@intel.com, oe-kbuild-all@lists.linux.dev
Subject: Re: [peterz-queue:x86/core 3/3] arch/x86/kernel/static_call.c:98
 __static_call_transform() error: uninitialized symbol 'op'.
Message-ID: <Y86maRy5ILlUBo/9@hirez.programming.kicks-ass.net>
References: <Y853bqEhA5NDC3Ar@kadam>
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In-Reply-To: <Y853bqEhA5NDC3Ar@kadam>

On Mon, Jan 23, 2023 at 03:02:54PM +0300, Dan Carpenter wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/core
> head:   700f4c6d925823018a2d09f92de5405065d2ffec
> commit: 700f4c6d925823018a2d09f92de5405065d2ffec [3/3] x86/static_call: Add support for Jcc tail-calls
> config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20230121/202301211834.noGVyk06-lkp@intel.com/config)
> compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <error27@gmail.com>
> 
> smatch warnings:
> arch/x86/kernel/static_call.c:98 __static_call_transform() error: uninitialized symbol 'op'.
> 
> vim +/op +98 arch/x86/kernel/static_call.c
> 
> c27c753ea6fd12 Thomas Gleixner 2022-07-12   53  static void __ref __static_call_transform(void *insn, enum insn_type type,
> c27c753ea6fd12 Thomas Gleixner 2022-07-12   54  					  void *func, bool modinit)
> e6d6c071f22de2 Josh Poimboeuf  2020-08-18   55  {
> 3f2a8fc4b15de1 Peter Zijlstra  2021-01-18   56  	const void *emulate = NULL;
> 452cddbff74b6a Peter Zijlstra  2020-08-18   57  	int size = CALL_INSN_SIZE;
> 452cddbff74b6a Peter Zijlstra  2020-08-18   58  	const void *code;
> 700f4c6d925823 Peter Zijlstra  2023-01-20   59  	u8 op, buf[6];
> 700f4c6d925823 Peter Zijlstra  2023-01-20   60  
> 700f4c6d925823 Peter Zijlstra  2023-01-20   61  	if ((type == JMP || type == RET) && (op = __is_Jcc(insn)))
> 700f4c6d925823 Peter Zijlstra  2023-01-20   62  		type = JCC;
> 
> Smatch is concerned that type can start as "JCC".

It can't. What's the normal way to shut this kind of warnings up?

Something like BUG_ON(type==JCC); should squash that value I suppose,
but it does seems a bit crude.