Re: [kbuild-all] Re: [linux-next:master 4103/11953] arch/arm/kernel/ftrace.c:229:6: warning: no previous prototype for function 'prepare_ftrace_return'

["Chen, Rong A" <rong.a.chen@intel.com>]

On 3/11/2022 10:04 AM, Steven Rostedt wrote:
> On Fri, 11 Mar 2022 09:44:11 +0800
> kernel test robot <lkp@intel.com> wrote:
> 
>> Hi Ard,
>>
>> FYI, the error/warning still remains.
>>
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>> head:   71941773e143369a73c9c4a3b62fbb60736a1182
>> commit: 41918ec82eb6f80c8b401422f27ca76c85aa0cb7 [4103/11953] ARM: ftrace: enable the graph tracer with the EABI unwinder
>> config: arm-aspeed_g4_defconfig (https://download.01.org/0day-ci/archive/20220311/202203110903.3xDyTUVl-lkp@intel.com/config)
>> compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project 276ca87382b8f16a65bddac700202924228982f6)
>> reproduce (this is a W=1 build):
>>          wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>>          chmod +x ~/bin/make.cross
>>          # install arm cross compiling tool for clang build
>>          # apt-get install binutils-arm-linux-gnueabi
>>          # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=41918ec82eb6f80c8b401422f27ca76c85aa0cb7
>>          git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
>>          git fetch --no-tags linux-next master
>>          git checkout 41918ec82eb6f80c8b401422f27ca76c85aa0cb7
>>          # save the config file to linux build tree
>>          mkdir build_dir
>>          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash arch/arm/kernel/
>>
>> If you fix the issue, kindly add following tag as appropriate
>> Reported-by: kernel test robot <lkp@intel.com>
>>
>> All warnings (new ones prefixed by >>):
>>
>>>> arch/arm/kernel/ftrace.c:229:6: warning: no previous prototype for function 'prepare_ftrace_return' [-Wmissing-prototypes]
>>     void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
>>          ^
>>     arch/arm/kernel/ftrace.c:229:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
>>     void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
>>     ^
>>     static
>>     1 warning generated.
>>
> 
> Hmm, this is only called from assembly code, which doesn't care about
> prototypes. Is there a way to quiet this warning to say "this is called
> only by assembly"?
> 
> Or do we just add a useless prototype to shut it up?
> 
> -- Steve

Hi Steve,

Sorry for the inconvenience, it's a duplicate false positive:
 
https://lore.kernel.org/linux-mm/2db6ea89-846a-8d4e-a5c3-954411332029@intel.com/

please ignore the report, we are still working on it.

Best Regards,
Rong Chen

> 
> 
>>
>> vim +/prepare_ftrace_return +229 arch/arm/kernel/ftrace.c
>>
>> 376cfa8730c08c Tim Bird                2010-10-09  226
>> 376cfa8730c08c Tim Bird                2010-10-09  227  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  228  asmlinkage
>> 376cfa8730c08c Tim Bird                2010-10-09 @229  void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  230  			   unsigned long frame_pointer,
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  231  			   unsigned long stack_pointer)
>> 376cfa8730c08c Tim Bird                2010-10-09  232  {
>> 376cfa8730c08c Tim Bird                2010-10-09  233  	unsigned long return_hooker = (unsigned long) &return_to_handler;
>> 376cfa8730c08c Tim Bird                2010-10-09  234  	unsigned long old;
>> 376cfa8730c08c Tim Bird                2010-10-09  235
>> 376cfa8730c08c Tim Bird                2010-10-09  236  	if (unlikely(atomic_read(&current->tracing_graph_pause)))
>> 376cfa8730c08c Tim Bird                2010-10-09  237  		return;
>> 376cfa8730c08c Tim Bird                2010-10-09  238
>> 953f534a7ed6b7 Ard Biesheuvel          2022-01-25  239  	if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER)) {
>> 953f534a7ed6b7 Ard Biesheuvel          2022-01-25  240  		/* FP points one word below parent's top of stack */
>> 953f534a7ed6b7 Ard Biesheuvel          2022-01-25  241  		frame_pointer += 4;
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  242  	} else {
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  243  		struct stackframe frame = {
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  244  			.fp = frame_pointer,
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  245  			.sp = stack_pointer,
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  246  			.lr = self_addr,
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  247  			.pc = self_addr,
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  248  		};
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  249  		if (unwind_frame(&frame) < 0)
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  250  			return;
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  251  		if (frame.lr != self_addr)
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  252  			parent = frame.lr_addr;
>> 41918ec82eb6f8 Ard Biesheuvel          2022-01-25  253  		frame_pointer = frame.sp;
>> 953f534a7ed6b7 Ard Biesheuvel          2022-01-25  254  	}
>> 953f534a7ed6b7 Ard Biesheuvel          2022-01-25  255
>> 376cfa8730c08c Tim Bird                2010-10-09  256  	old = *parent;
>> 376cfa8730c08c Tim Bird                2010-10-09  257  	*parent = return_hooker;
>> 376cfa8730c08c Tim Bird                2010-10-09  258
>> f1f5b14afd7cce Steven Rostedt (VMware  2018-11-18  259) 	if (function_graph_enter(old, self_addr, frame_pointer, NULL))
>> 376cfa8730c08c Tim Bird                2010-10-09  260  		*parent = old;
>> 376cfa8730c08c Tim Bird                2010-10-09  261  }
>> dd686eb13959e4 Rabin Vincent           2010-11-06  262
>>
>> :::::: The code at line 229 was first introduced by commit
>> :::::: 376cfa8730c08c0394d0aa1d4a80fd8c9971f323 ARM: ftrace: function graph tracer support
>>
>> :::::: TO: Tim Bird <tim.bird@am.sony.com>
>> :::::: CC: Rabin Vincent <rabin@rab.in>
>>
>> ---
>> 0-DAY CI Kernel Test Service
>> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
> _______________________________________________
> kbuild-all mailing list -- kbuild-all@lists.01.org
> To unsubscribe send an email to kbuild-all-leave@lists.01.org
>