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-randconfig-062-20250227 (https://download.01.org/0day-ci/archive/20250228/202502280123.BNaCYT2A-lkp@xxxxxxxxx/config)
compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250228/202502280123.BNaCYT2A-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/202502280123.BNaCYT2A-lkp@xxxxxxxxx/

sparse warnings: (new ones prefixed by >>)
   kernel/trace/kfunc_md.c:12:23: sparse: sparse: symbol 'kfunc_mds' redeclared with different type (different address spaces):
   kernel/trace/kfunc_md.c:12:23: sparse:    struct kfunc_md [noderef] __rcu *[addressable] [toplevel] kfunc_mds
   kernel/trace/kfunc_md.c: note: in included file:
   include/linux/kfunc_md.h:16:24: sparse: note: previously declared as:
   include/linux/kfunc_md.h:16:24: sparse:    struct kfunc_md *extern [addressable] [toplevel] kfunc_mds
   kernel/trace/kfunc_md.c:186:20: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected struct kfunc_md *md @@     got struct kfunc_md [noderef] __rcu * @@
   kernel/trace/kfunc_md.c:186:20: sparse:     expected struct kfunc_md *md
   kernel/trace/kfunc_md.c:186:20: sparse:     got struct kfunc_md [noderef] __rcu *
>> kernel/trace/kfunc_md.c:98:25: sparse: sparse: non size-preserving pointer to integer cast

vim +98 kernel/trace/kfunc_md.c

    10	
    11	static u32 kfunc_md_count = ENTRIES_PER_PAGE, kfunc_md_used;
  > 12	struct kfunc_md __rcu *kfunc_mds;
    13	EXPORT_SYMBOL_GPL(kfunc_mds);
    14	
    15	static DEFINE_MUTEX(kfunc_md_mutex);
    16	
    17	
    18	void kfunc_md_unlock(void)
    19	{
    20		mutex_unlock(&kfunc_md_mutex);
    21	}
    22	EXPORT_SYMBOL_GPL(kfunc_md_unlock);
    23	
    24	void kfunc_md_lock(void)
    25	{
    26		mutex_lock(&kfunc_md_mutex);
    27	}
    28	EXPORT_SYMBOL_GPL(kfunc_md_lock);
    29	
    30	static u32 kfunc_md_get_index(void *ip)
    31	{
    32		return *(u32 *)(ip - KFUNC_MD_DATA_OFFSET);
    33	}
    34	
    35	static void kfunc_md_init(struct kfunc_md *mds, u32 start, u32 end)
    36	{
    37		u32 i;
    38	
    39		for (i = start; i < end; i++)
    40			mds[i].users = 0;
    41	}
    42	
    43	static int kfunc_md_page_order(void)
    44	{
    45		return fls(DIV_ROUND_UP(kfunc_md_count, ENTRIES_PER_PAGE)) - 1;
    46	}
    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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