Re: [PATCH v5 bpf-next 2/6] bpf: move to generic BTF show support, apply it to seq files/strings

From: kernel test robot <lkp@intel.com>
To: kbuild-all@lists.01.org
Subject: Re: [PATCH v5 bpf-next 2/6] bpf: move to generic BTF show support, apply it to seq files/strings
Date: Sat, 19 Sep 2020 02:20:34 +0800	[thread overview]
Message-ID: <202009190248.GLnmik01%lkp@intel.com> (raw)
In-Reply-To: <1600436075-2961-3-git-send-email-alan.maguire@oracle.com>

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Hi Alan,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/0day-ci/linux/commits/Alan-Maguire/bpf-add-helpers-to-support-BTF-based-kernel-data-display/20200918-213932
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: sparc-randconfig-p002-20200917 (attached as .config)
compiler: sparc-linux-gcc (GCC) 9.3.0
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
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=sparc 

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 >>):

>> kernel/bpf/btf.c:5310:6: warning: no previous prototype for 'btf_type_show' [-Wmissing-prototypes]
    5310 | void btf_type_show(const struct btf *btf, u32 type_id, void *obj,
         |      ^~~~~~~~~~~~~
   kernel/bpf/btf.c: In function 'btf_seq_show':
>> kernel/bpf/btf.c:5327:22: warning: function 'btf_seq_show' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    5327 |  seq_vprintf((struct seq_file *)show->target, fmt, args);
         |                      ^~~~~~~~
   kernel/bpf/btf.c: In function 'btf_snprintf_show':
>> kernel/bpf/btf.c:5357:2: warning: function 'btf_snprintf_show' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    5357 |  len = vsnprintf(show->target, ssnprintf->len_left, fmt, args);
         |  ^~~

# https://github.com/0day-ci/linux/commit/a85186d405b24251bfd7179ae1949f3458e9702d
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Alan-Maguire/bpf-add-helpers-to-support-BTF-based-kernel-data-display/20200918-213932
git checkout a85186d405b24251bfd7179ae1949f3458e9702d
vim +/btf_type_show +5310 kernel/bpf/btf.c

  5309	
> 5310	void btf_type_show(const struct btf *btf, u32 type_id, void *obj,
  5311			   struct btf_show *show)
  5312	{
  5313		const struct btf_type *t = btf_type_by_id(btf, type_id);
  5314	
  5315		show->btf = btf;
  5316		memset(&show->state, 0, sizeof(show->state));
  5317		memset(&show->obj, 0, sizeof(show->obj));
  5318	
  5319		btf_type_ops(t)->show(btf, t, type_id, obj, 0, show);
  5320	}
  5321	
  5322	static void btf_seq_show(struct btf_show *show, const char *fmt, ...)
  5323	{
  5324		va_list args;
  5325	
  5326		va_start(args, fmt);
> 5327		seq_vprintf((struct seq_file *)show->target, fmt, args);
  5328		va_end(args);
  5329	}
  5330	
  5331	void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
  5332				struct seq_file *m)
  5333	{
  5334		struct btf_show sseq;
  5335	
  5336		sseq.target = m;
  5337		sseq.showfn = btf_seq_show;
  5338		sseq.flags = BTF_SHOW_NONAME | BTF_SHOW_COMPACT | BTF_SHOW_ZERO |
  5339			     BTF_SHOW_UNSAFE;
  5340	
  5341		btf_type_show(btf, type_id, obj, &sseq);
  5342	}
  5343	
  5344	struct btf_show_snprintf {
  5345		struct btf_show show;
  5346		int len_left;		/* space left in string */
  5347		int len;		/* length we would have written */
  5348	};
  5349	
  5350	static void btf_snprintf_show(struct btf_show *show, const char *fmt, ...)
  5351	{
  5352		struct btf_show_snprintf *ssnprintf = (struct btf_show_snprintf *)show;
  5353		va_list args;
  5354		int len;
  5355	
  5356		va_start(args, fmt);
> 5357		len = vsnprintf(show->target, ssnprintf->len_left, fmt, args);
  5358		va_end(args);
  5359	
  5360		if (len < 0) {
  5361			ssnprintf->len_left = 0;
  5362			ssnprintf->len = len;
  5363		} else if (len > ssnprintf->len_left) {
  5364			/* no space, drive on to get length we would have written */
  5365			ssnprintf->len_left = 0;
  5366			ssnprintf->len += len;
  5367		} else {
  5368			ssnprintf->len_left -= len;
  5369			ssnprintf->len += len;
  5370			show->target += len;
  5371		}
  5372	}
  5373	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

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