linux-kernel - Re: kernel/gcov/fs.c:103: warning: Excess struct member 'buffer' description in 'gcov

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Date: Fri, 15 Dec 2023 09:10:21 +0800
From: Philip Li <philip.li@...el.com>
To: Kees Cook <keescook@...omium.org>
CC: kernel test robot <lkp@...el.com>, <oe-kbuild-all@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.org>, "Gustavo A. R. Silva"
	<gustavoars@...nel.org>, Peter Oberparleiter <oberpar@...ux.ibm.com>,
	<linux-doc@...r.kernel.org>, <linux-hardening@...r.kernel.org>
Subject: Re: kernel/gcov/fs.c:103: warning: Excess struct member 'buffer'
 description in 'gcov_iterator'

On Thu, Dec 14, 2023 at 01:50:05PM -0800, Kees Cook wrote:
> On Fri, Dec 15, 2023 at 04:53:19AM +0800, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   5bd7ef53ffe5ca580e93e74eb8c81ed191ddc4bd
> > commit: fbd126f5a658b92c7f6af986a6d89cf5e5693268 gcov: annotate struct gcov_iterator with __counted_by
> > date:   8 weeks ago
> > config: i386-buildonly-randconfig-001-20231214 (https://download.01.org/0day-ci/archive/20231215/202312150432.oBngC94A-lkp@intel.com/config)
> > compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231215/202312150432.oBngC94A-lkp@intel.com/reproduce)
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@...el.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202312150432.oBngC94A-lkp@intel.com/
> > 
> > All warnings (new ones prefixed by >>):
> > 
> > >> kernel/gcov/fs.c:103: warning: Excess struct member 'buffer' description in 'gcov_iterator'
> > 
> > 
> > vim +103 kernel/gcov/fs.c
> > 
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   90  
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   91  /**
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   92   * struct gcov_iterator - specifies current file position in logical records
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   93   * @info: associated profiling data
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   94   * @buffer: buffer containing file data
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   95   * @size: size of buffer
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   96   * @pos: current position in file
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   97   */
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   98  struct gcov_iterator {
> > 7a1d55b987dfcb Johannes Berg 2021-05-06   99  	struct gcov_info *info;
> > 7a1d55b987dfcb Johannes Berg 2021-05-06  100  	size_t size;
> > 7a1d55b987dfcb Johannes Berg 2021-05-06  101  	loff_t pos;
> > fbd126f5a658b9 Kees Cook     2023-09-22  102  	char buffer[] __counted_by(size);
> > 7a1d55b987dfcb Johannes Berg 2021-05-06 @103  };
> > 7a1d55b987dfcb Johannes Berg 2021-05-06  104  
> 
> It looks like whatever produces that error is not parsing attributes
> correctly. I suspect this is the "htmldocs" target and "__counted_by" is
> missing from Documentation/conf.py. I'll investigate...

This is triggered by W=1 build

        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash kernel/gcov/

The detail step is at [1], hope it can help reproduce the issue

[1] https://download.01.org/0day-ci/archive/20231215/202312150432.oBngC94A-lkp@intel.com/reproduce

> 
> -- 
> Kees Cook
>