Hi Stanislav,

I love your patch! Yet something to improve:

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

url:    https://github.com/intel-lab-lkp/linux/commits/Stanislav-Fomichev/xdp-hints-via-kfuncs/20221115-110547
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20221115030210.3159213-7-sdf%40google.com
patch subject: [PATCH bpf-next 06/11] xdp: Carry over xdp metadata into skb context
config: hexagon-randconfig-r041-20221115
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 463da45892e2d2a262277b91b96f5f8c05dc25d0)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/5c7e4e60d13af8491563dd4d2ad5fc684420e540
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Stanislav-Fomichev/xdp-hints-via-kfuncs/20221115-110547
        git checkout 5c7e4e60d13af8491563dd4d2ad5fc684420e540
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash net/core/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from net/core/dev_addr_lists_test.c:4:
   In file included from include/linux/etherdevice.h:20:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:17:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __raw_readb(PCI_IOBASE + addr);
                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
                                                     ^
   In file included from net/core/dev_addr_lists_test.c:4:
   In file included from include/linux/etherdevice.h:20:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:17:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
                                                     ^
   In file included from net/core/dev_addr_lists_test.c:4:
   In file included from include/linux/etherdevice.h:20:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:17:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   In file included from net/core/dev_addr_lists_test.c:4:
   In file included from include/linux/etherdevice.h:21:
   In file included from include/linux/netdevice.h:43:
>> include/net/xdp.h:449:2: error: void function 'xdp_metadata_export_to_skb' should not return a value [-Wreturn-type]
           return 0;
           ^      ~
   6 warnings and 1 error generated.
--
   In file included from net/core/xdp.c:9:
   In file included from include/linux/filter.h:12:
   In file included from include/linux/skbuff.h:17:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __raw_readb(PCI_IOBASE + addr);
                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
                                                     ^
   In file included from net/core/xdp.c:9:
   In file included from include/linux/filter.h:12:
   In file included from include/linux/skbuff.h:17:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
                                                     ^
   In file included from net/core/xdp.c:9:
   In file included from include/linux/filter.h:12:
   In file included from include/linux/skbuff.h:17:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   In file included from net/core/xdp.c:9:
   In file included from include/linux/filter.h:20:
   In file included from include/linux/if_vlan.h:10:
   In file included from include/linux/netdevice.h:43:
>> include/net/xdp.h:449:2: error: void function 'xdp_metadata_export_to_skb' should not return a value [-Wreturn-type]
           return 0;
           ^      ~
   net/core/xdp.c:734:14: warning: no previous prototype for function 'bpf_xdp_metadata_export_to_skb' [-Wmissing-prototypes]
   noinline int bpf_xdp_metadata_export_to_skb(const struct xdp_md *ctx)
                ^
   net/core/xdp.c:734:10: note: declare 'static' if the function is not intended to be used outside of this translation unit
   noinline int bpf_xdp_metadata_export_to_skb(const struct xdp_md *ctx)
            ^
            static 
   net/core/xdp.c:743:14: warning: no previous prototype for function 'bpf_xdp_metadata_rx_timestamp_supported' [-Wmissing-prototypes]
   noinline int bpf_xdp_metadata_rx_timestamp_supported(const struct xdp_md *ctx)
                ^
   net/core/xdp.c:743:10: note: declare 'static' if the function is not intended to be used outside of this translation unit
   noinline int bpf_xdp_metadata_rx_timestamp_supported(const struct xdp_md *ctx)
            ^
            static 
   net/core/xdp.c:751:10: warning: 'const' type qualifier on return type has no effect [-Wignored-qualifiers]
   noinline const __u64 bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx)
            ^~~~~~
   net/core/xdp.c:751:22: warning: no previous prototype for function 'bpf_xdp_metadata_rx_timestamp' [-Wmissing-prototypes]
   noinline const __u64 bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx)
                        ^
   net/core/xdp.c:751:16: note: declare 'static' if the function is not intended to be used outside of this translation unit
   noinline const __u64 bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx)
                  ^
                  static 
   net/core/xdp.c:881:6: error: redefinition of 'xdp_metadata_export_to_skb'
   void xdp_metadata_export_to_skb(const struct bpf_prog *prog, struct bpf_patch *patch)
        ^
   include/net/xdp.h:447:13: note: previous definition is here
   static void xdp_metadata_export_to_skb(const struct bpf_prog *prog, struct bpf_patch *patch)
               ^
   10 warnings and 2 errors generated.
--
   In file included from net/core/net-traces.c:8:
   In file included from include/linux/netdevice.h:38:
   In file included from include/net/net_namespace.h:43:
   In file included from include/linux/skbuff.h:17:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __raw_readb(PCI_IOBASE + addr);
                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
                                                     ^
   In file included from net/core/net-traces.c:8:
   In file included from include/linux/netdevice.h:38:
   In file included from include/net/net_namespace.h:43:
   In file included from include/linux/skbuff.h:17:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
                                                     ^
   In file included from net/core/net-traces.c:8:
   In file included from include/linux/netdevice.h:38:
   In file included from include/net/net_namespace.h:43:
   In file included from include/linux/skbuff.h:17:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   In file included from net/core/net-traces.c:8:
   In file included from include/linux/netdevice.h:43:
>> include/net/xdp.h:449:2: error: void function 'xdp_metadata_export_to_skb' should not return a value [-Wreturn-type]
           return 0;
           ^      ~
   In file included from net/core/net-traces.c:50:
   In file included from include/trace/events/neigh.h:255:
   In file included from include/trace/define_trace.h:102:
   In file included from include/trace/trace_events.h:419:
   include/trace/events/neigh.h:42:20: warning: variable 'pin6' set but not used [-Wunused-but-set-variable]
                   struct in6_addr *pin6;
                                    ^
   In file included from net/core/net-traces.c:50:
   In file included from include/trace/events/neigh.h:255:
   In file included from include/trace/define_trace.h:103:
   In file included from include/trace/perf.h:113:
   include/trace/events/neigh.h:42:20: warning: variable 'pin6' set but not used [-Wunused-but-set-variable]
                   struct in6_addr *pin6;
                                    ^
   8 warnings and 1 error generated.


vim +/xdp_metadata_export_to_skb +449 include/net/xdp.h

   437	
   438	#ifdef CONFIG_DEBUG_INFO_BTF
   439	extern struct btf_id_set8 xdp_metadata_kfunc_ids;
   440	static inline u32 xdp_metadata_kfunc_id(int id)
   441	{
   442		return xdp_metadata_kfunc_ids.pairs[id].id;
   443	}
   444	void xdp_metadata_export_to_skb(const struct bpf_prog *prog, struct bpf_patch *patch);
   445	#else
   446	static inline u32 xdp_metadata_kfunc_id(int id) { return 0; }
   447	static void xdp_metadata_export_to_skb(const struct bpf_prog *prog, struct bpf_patch *patch)
   448	{
 > 449		return 0;
   450	}
   451	#endif
   452	

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