Re: [PATCH bpf-next v2] add function metadata support

[kernel test robot <lkp@xxxxxxxxx>]

Hi Menglong,

kernel test robot noticed the following build warnings:

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

url:    https://github.com/intel-lab-lkp/linux/commits/Menglong-Dong/add-function-metadata-support/20250226-202312
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20250226121537.752241-1-dongml2%40chinatelecom.cn
patch subject: [PATCH bpf-next v2] add function metadata support
config: i386-buildonly-randconfig-002-20250227 (https://download.01.org/0day-ci/archive/20250228/202502280842.nI3PwNwz-lkp@xxxxxxxxx/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/20250228/202502280842.nI3PwNwz-lkp@xxxxxxxxx/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@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502280842.nI3PwNwz-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

   kernel/trace/kfunc_md.c: In function 'kfunc_md_get_next':
>> kernel/trace/kfunc_md.c:98:20: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
      98 |         free_pages((u64)mds, order);
         |                    ^

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for CALL_PADDING
   Depends on [n]: CC_HAS_ENTRY_PADDING [=y] && OBJTOOL [=n]
   Selected by [y]:
   - FUNCTION_METADATA [=y]


vim +98 kernel/trace/kfunc_md.c

    47	
    48	/* Get next usable function metadata. On success, return the usable
    49	 * kfunc_md and store the index of it to *index. If no usable kfunc_md is
    50	 * found in kfunc_mds, a larger array will be allocated.
    51	 */
    52	static struct kfunc_md *kfunc_md_get_next(u32 *index)
    53	{
    54		struct kfunc_md *new_mds, *mds;
    55		u32 i, order;
    56	
    57		mds = rcu_dereference(kfunc_mds);
    58		if (mds == NULL) {
    59			order = kfunc_md_page_order();
    60			new_mds = (void *)__get_free_pages(GFP_KERNEL, order);
    61			if (!new_mds)
    62				return NULL;
    63			kfunc_md_init(new_mds, 0, kfunc_md_count);
    64			/* The first time to initialize kfunc_mds, so it is not
    65			 * used anywhere yet, and we can update it directly.
    66			 */
    67			rcu_assign_pointer(kfunc_mds, new_mds);
    68			mds = new_mds;
    69		}
    70	
    71		if (likely(kfunc_md_used < kfunc_md_count)) {
    72			/* maybe we can manage the used function metadata entry
    73			 * with a bit map ?
    74			 */
    75			for (i = 0; i < kfunc_md_count; i++) {
    76				if (!mds[i].users) {
    77					kfunc_md_used++;
    78					*index = i;
    79					mds[i].users++;
    80					return mds + i;
    81				}
    82			}
    83		}
    84	
    85		order = kfunc_md_page_order();
    86		/* no available function metadata, so allocate a bigger function
    87		 * metadata array.
    88		 */
    89		new_mds = (void *)__get_free_pages(GFP_KERNEL, order + 1);
    90		if (!new_mds)
    91			return NULL;
    92	
    93		memcpy(new_mds, mds, kfunc_md_count * sizeof(*new_mds));
    94		kfunc_md_init(new_mds, kfunc_md_count, kfunc_md_count * 2);
    95	
    96		rcu_assign_pointer(kfunc_mds, new_mds);
    97		synchronize_rcu();
  > 98		free_pages((u64)mds, order);
    99	
   100		mds = new_mds + kfunc_md_count;
   101		*index = kfunc_md_count;
   102		kfunc_md_count <<= 1;
   103		kfunc_md_used++;
   104		mds->users++;
   105	
   106		return mds;
   107	}
   108	

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