Hi Pingfan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/net]
[also build test WARNING on bpf-next/master bpf/master akpm-mm/mm-nonmm-unstable linus/master v6.19-rc6 next-20260116]
[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/Pingfan-Liu/bpf-Introduce-kfuncs-to-parser-buffer-content/20260119-112939
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git net
patch link:    https://lore.kernel.org/r/20260119032424.10781-12-piliu%40redhat.com
patch subject: [PATCHv6 11/13] arm64/kexec: Select KEXEC_BPF to support UEFI-style kernel image
config: arm64-randconfig-004-20260119 (https://download.01.org/0day-ci/archive/20260119/202601191626.CUD61tIS-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/20260119/202601191626.CUD61tIS-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/202601191626.CUD61tIS-lkp@intel.com/ (local)

All warnings (new ones prefixed by >>):

quoted

kernel/kexec_bpf_loader.c:103:22: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes]

     103 | __attribute__((used, optimize("O0"))) void kexec_image_parser_anchor(
         |                      ^~~~~~~~~~~~~~
   1 warning generated.

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for KEXEC_BPF
   Depends on [n]: KEXEC_FILE [=y] && DEBUG_INFO_BTF [=y] && BPF_SYSCALL [=y] && KEEP_DECOMPRESSOR [=n]
   Selected by [y]:
   - ARCH_SELECTS_KEXEC_FILE [=y] && KEXEC_FILE [=y] && DEBUG_INFO_BTF [=y] && BPF_SYSCALL [=y]


vim +/optimize +103 kernel/kexec_bpf_loader.c

e683ae405ea0458 Pingfan Liu 2026-01-19   93  
e683ae405ea0458 Pingfan Liu 2026-01-19   94  void kexec_image_parser_anchor(struct kexec_context *context,
e683ae405ea0458 Pingfan Liu 2026-01-19   95  		unsigned long parser_id);
e683ae405ea0458 Pingfan Liu 2026-01-19   96  
e683ae405ea0458 Pingfan Liu 2026-01-19   97  /*
e683ae405ea0458 Pingfan Liu 2026-01-19   98   * optimize("O0") prevents inline, compiler constant propagation
e683ae405ea0458 Pingfan Liu 2026-01-19   99   *
e683ae405ea0458 Pingfan Liu 2026-01-19  100   * Let bpf be the program context pointer so that it will not be spilled into
e683ae405ea0458 Pingfan Liu 2026-01-19  101   * stack.
e683ae405ea0458 Pingfan Liu 2026-01-19  102   */
e683ae405ea0458 Pingfan Liu 2026-01-19 @103  __attribute__((used, optimize("O0"))) void kexec_image_parser_anchor(
e683ae405ea0458 Pingfan Liu 2026-01-19  104  		struct kexec_context *context,
e683ae405ea0458 Pingfan Liu 2026-01-19  105  		unsigned long parser_id)
e683ae405ea0458 Pingfan Liu 2026-01-19  106  {
e683ae405ea0458 Pingfan Liu 2026-01-19  107  	/*
e683ae405ea0458 Pingfan Liu 2026-01-19  108  	 * To prevent linker from Identical Code Folding (ICF) with kexec_image_parser_anchor,
e683ae405ea0458 Pingfan Liu 2026-01-19  109  	 * making them have different code.
e683ae405ea0458 Pingfan Liu 2026-01-19  110  	 */
e683ae405ea0458 Pingfan Liu 2026-01-19  111  	volatile int dummy = 0;
e683ae405ea0458 Pingfan Liu 2026-01-19  112  
e683ae405ea0458 Pingfan Liu 2026-01-19  113  	dummy += 1;
e683ae405ea0458 Pingfan Liu 2026-01-19  114  }
e683ae405ea0458 Pingfan Liu 2026-01-19  115  

-- 
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https://github.com/intel/lkp-tests/wiki