Hi Jiri,

kernel test robot noticed the following build errors:

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

url:    https://github.com/intel-lab-lkp/linux/commits/Jiri-Olsa/ftrace-Add-ftrace_hash_count-function/20260316-160117
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20260316075138.465430-9-jolsa%40kernel.org
patch subject: [PATCHv3 bpf-next 08/24] bpf: Add bpf_trampoline_multi_attach/detach functions
config: x86_64-randconfig-075-20260320 (https://download.01.org/0day-ci/archive/20260320/202603201820.zsM5FRDS-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260320/202603201820.zsM5FRDS-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 [off-list ref]
| Closes: https://lore.kernel.org/oe-kbuild-all/202603201820.zsM5FRDS-lkp@intel.com/ (local)

All errors (new ones prefixed by >>):

quoted

kernel/bpf/trampoline.c:1520:8: error: call to undeclared function 'btf_distill_func_proto'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]

    1520 |         err = btf_distill_func_proto(NULL, btf, t, tname, &tgt_info->fmodel);
         |               ^
   1 error generated.


vim +/btf_distill_func_proto +1520 kernel/bpf/trampoline.c

  1498	
  1499	static int bpf_get_btf_id_target(struct btf *btf, struct bpf_prog *prog, u32 btf_id,
  1500					 struct bpf_attach_target_info *tgt_info)
  1501	{
  1502		const struct btf_type *t;
  1503		unsigned long addr;
  1504		const char *tname;
  1505		int err;
  1506	
  1507		if (!btf_id || !btf)
  1508			return -EINVAL;
  1509		t = btf_type_by_id(btf, btf_id);
  1510		if (!t)
  1511			return -EINVAL;
  1512		tname = btf_name_by_offset(btf, t->name_off);
  1513		if (!tname)
  1514			return -EINVAL;
  1515		if (!btf_type_is_func(t))
  1516			return -EINVAL;
  1517		t = btf_type_by_id(btf, t->type);
  1518		if (!btf_type_is_func_proto(t))
  1519			return -EINVAL;

1520		err = btf_distill_func_proto(NULL, btf, t, tname, &tgt_info->fmodel);

  1521		if (err < 0)
  1522			return err;
  1523		if (btf_is_module(btf)) {
  1524			/* The bpf program already holds refference to module. */
  1525			if (WARN_ON_ONCE(!prog->aux->mod))
  1526				return -EINVAL;
  1527			addr = find_kallsyms_symbol_value(prog->aux->mod, tname);
  1528		} else {
  1529			addr = kallsyms_lookup_name(tname);
  1530		}
  1531		if (!addr || !ftrace_location(addr))
  1532			return -ENOENT;
  1533		tgt_info->tgt_addr = addr;
  1534		return 0;
  1535	}
  1536	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki