tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c:33:1: warning: no previous prototype for 'bpf_testmod_test_btf_type_tag_user_1'

[kernel test robot <lkp@intel.com>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   148341f0a2f53b5e8808d093333d85170586a15d
commit: 696c39011538fe0124fcc0e81ebc44ff7f8623b4 selftests/bpf: add a selftest with __user tag
date:   1 year, 2 months ago
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=696c39011538fe0124fcc0e81ebc44ff7f8623b4
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 696c39011538fe0124fcc0e81ebc44ff7f8623b4
        make O=/tmp/kselftest headers
        make O=/tmp/kselftest -C tools/testing/selftests

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304040710.NAEyrWKF-lkp@intel.com/

All warnings (new ones prefixed by >>):

   tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c:19:1: warning: no previous prototype for 'bpf_testmod_test_mod_kfunc' [-Wmissing-prototypes]
      19 | bpf_testmod_test_mod_kfunc(int i)
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~
>> tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c:33:1: warning: no previous prototype for 'bpf_testmod_test_btf_type_tag_user_1' [-Wmissing-prototypes]
      33 | bpf_testmod_test_btf_type_tag_user_1(struct bpf_testmod_btf_type_tag_1 __user *arg) {
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c:38:1: warning: no previous prototype for 'bpf_testmod_test_btf_type_tag_user_2' [-Wmissing-prototypes]
      38 | bpf_testmod_test_btf_type_tag_user_2(struct bpf_testmod_btf_type_tag_2 *arg) {
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c:42:14: warning: no previous prototype for 'bpf_testmod_loop_test' [-Wmissing-prototypes]
      42 | noinline int bpf_testmod_loop_test(int n)
         |              ^~~~~~~~~~~~~~~~~~~~~
   tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c:54:30: warning: no previous prototype for 'bpf_testmod_return_ptr' [-Wmissing-prototypes]
      54 | __weak noinline struct file *bpf_testmod_return_ptr(int arg)
         |                              ^~~~~~~~~~~~~~~~~~~~~~
   tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c:71:1: warning: no previous prototype for 'bpf_testmod_test_read' [-Wmissing-prototypes]
      71 | bpf_testmod_test_read(struct file *file, struct kobject *kobj,
         | ^~~~~~~~~~~~~~~~~~~~~
   tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c:107:1: warning: no previous prototype for 'bpf_testmod_test_write' [-Wmissing-prototypes]
     107 | bpf_testmod_test_write(struct file *file, struct kobject *kobj,
         | ^~~~~~~~~~~~~~~~~~~~~~
   tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.o: warning: objtool: bpf_testmod_return_ptr()+0x15: unreachable instruction


vim +/bpf_testmod_test_btf_type_tag_user_1 +33 tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c

    17	
    18	noinline void
  > 19	bpf_testmod_test_mod_kfunc(int i)
    20	{
    21		*(int *)this_cpu_ptr(&bpf_testmod_ksym_percpu) = i;
    22	}
    23	
    24	struct bpf_testmod_btf_type_tag_1 {
    25		int a;
    26	};
    27	
    28	struct bpf_testmod_btf_type_tag_2 {
    29		struct bpf_testmod_btf_type_tag_1 __user *p;
    30	};
    31	
    32	noinline int
  > 33	bpf_testmod_test_btf_type_tag_user_1(struct bpf_testmod_btf_type_tag_1 __user *arg) {
    34		return arg->a;
    35	}
    36	
    37	noinline int
  > 38	bpf_testmod_test_btf_type_tag_user_2(struct bpf_testmod_btf_type_tag_2 *arg) {
    39		return arg->p->a;
    40	}
    41	

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