Hi Alan,

[FYI, it's a private test report for your RFC patch.]
[auto build test WARNING on bpf-next/master]

url:    https://github.com/0day-ci/linux/commits/Alan-Maguire/bpf-libbpf-share-BTF-data-show-functionality/20210112-013917
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: arm-randconfig-r014-20210111 (attached as .config)
compiler: arm-linux-gnueabi-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
        # https://github.com/0day-ci/linux/commit/04cba32126a479b2b87ff64eaf1e266574221cad
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Alan-Maguire/bpf-libbpf-share-BTF-data-show-functionality/20210112-013917
        git checkout 04cba32126a479b2b87ff64eaf1e266574221cad
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arm 

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_show_common.c: In function 'btf_seq_show':
>> kernel/bpf/btf_show_common.c:1136:22: warning: function 'btf_seq_show' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    1136 |  seq_vprintf((struct seq_file *)show->target, fmt, args);
         |                      ^~~~~~~~
   kernel/bpf/btf_show_common.c: In function 'btf_snprintf_show':
>> kernel/bpf/btf_show_common.c:1175:2: warning: function 'btf_snprintf_show' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    1175 |  len = vsnprintf(show->target, ssnprintf->len_left, fmt, args);
         |  ^~~


vim +1136 kernel/bpf/btf_show_common.c

  1130	
  1131	/* seq_file show is for kernel only. */
  1132	#ifdef __KERNEL__
  1133	static void btf_seq_show(struct btf_show *show, const char *fmt,
  1134				 va_list args)
  1135	{
> 1136		seq_vprintf((struct seq_file *)show->target, fmt, args);
  1137	}
  1138	
  1139	int btf_type_seq_show_flags(const struct btf *btf, u32 type_id,
  1140				    void *obj, struct seq_file *m, u64 flags)
  1141	{
  1142		struct btf_show sseq;
  1143	
  1144		sseq.target = m;
  1145		sseq.showfn = btf_seq_show;
  1146		sseq.flags = flags;
  1147	
  1148		btf_type_show(btf, type_id, obj, &sseq);
  1149	
  1150		return sseq.state.status;
  1151	}
  1152	
  1153	void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
  1154			       struct seq_file *m)
  1155	{
  1156		(void) btf_type_seq_show_flags(btf, type_id, obj, m,
  1157					       BTF_SHOW_NONAME | BTF_SHOW_COMPACT |
  1158					       BTF_SHOW_ZERO | BTF_SHOW_UNSAFE);
  1159	}
  1160	
  1161	#endif /* __KERNEL__ */
  1162	
  1163	struct btf_show_snprintf {
  1164		struct btf_show show;
  1165		int len_left;		/* space left in string */
  1166		int len;		/* length we would have written */
  1167	};
  1168	
  1169	static void btf_snprintf_show(struct btf_show *show, const char *fmt,
  1170				      va_list args)
  1171	{
  1172		struct btf_show_snprintf *ssnprintf = (struct btf_show_snprintf *)show;
  1173		int len;
  1174	
> 1175		len = vsnprintf(show->target, ssnprintf->len_left, fmt, args);
  1176	
  1177		if (len < 0) {
  1178			ssnprintf->len_left = 0;
  1179			ssnprintf->len = len;
  1180		} else if (len > ssnprintf->len_left) {
  1181			/* no space, drive on to get length we would have written */
  1182			ssnprintf->len_left = 0;
  1183			ssnprintf->len += len;
  1184		} else {
  1185			ssnprintf->len_left -= len;
  1186			ssnprintf->len += len;
  1187			show->target += len;
  1188		}
  1189	}
  1190	

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