Re: [PATCH v2 3/3] bpf: eliminate the allocation of an intermediate struct bpf_key

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

Hi James,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/master]
[also build test WARNING on bpf/master linus/master v6.16 next-20250731]
[cannot apply to bpf-next/net]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/James-Bottomley/bpf-make-bpf_key-an-opaque-type/20250731-013040
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20250730172745.8480-4-James.Bottomley%40HansenPartnership.com
patch subject: [PATCH v2 3/3] bpf: eliminate the allocation of an intermediate struct bpf_key
config: i386-randconfig-r133-20250801 (https://download.01.org/0day-ci/archive/20250801/202508010906.eulQ24IN-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250801/202508010906.eulQ24IN-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 <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508010906.eulQ24IN-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   kernel/trace/bpf_trace.c:834:41: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected void [noderef] __user *[addressable] [assigned] [usertype] sival_ptr @@     got void * @@
   kernel/trace/bpf_trace.c:834:41: sparse:     expected void [noderef] __user *[addressable] [assigned] [usertype] sival_ptr
   kernel/trace/bpf_trace.c:834:41: sparse:     got void *
>> kernel/trace/bpf_trace.c:1249:11: sparse: sparse: symbol 'BUILTIN_KEY' was not declared. Should it be static?
   kernel/trace/bpf_trace.c:3684:52: sparse: sparse: cast removes address space '__user' of expression
   kernel/trace/bpf_trace.c:3698:56: sparse: sparse: cast removes address space '__user' of expression
   kernel/trace/bpf_trace.c:3712:52: sparse: sparse: cast removes address space '__user' of expression
   kernel/trace/bpf_trace.c:3719:56: sparse: sparse: cast removes address space '__user' of expression
   kernel/trace/bpf_trace.c:3727:52: sparse: sparse: cast removes address space '__user' of expression
   kernel/trace/bpf_trace.c:3735:56: sparse: sparse: cast removes address space '__user' of expression
   kernel/trace/bpf_trace.c: note: in included file (through include/linux/rbtree.h, include/linux/mm_types.h, include/linux/mmzone.h, ...):
   include/linux/rcupdate.h:871:25: sparse: sparse: context imbalance in 'uprobe_prog_run' - unexpected unlock

vim +/BUILTIN_KEY +1249 kernel/trace/bpf_trace.c

  1243	
  1244	#ifdef CONFIG_KEYS
  1245	/* BTF requires this even if it serves no purpose */
  1246	struct bpf_key {
  1247	};
  1248	/* conventional value to replace zero return which would become NULL */
> 1249	const u64 BUILTIN_KEY = -1LL;
  1250	

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