Re: [PATCH 1/2] qnx4: Extract dir entry filename processing into helper

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

Hi Kees,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.7-rc1 next-20231117]
[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/Kees-Cook/qnx4-Extract-dir-entry-filename-processing-into-helper/20231118-114223
base:   linus/master
patch link:    https://lore.kernel.org/r/20231118033225.2181299-1-keescook%40chromium.org
patch subject: [PATCH 1/2] qnx4: Extract dir entry filename processing into helper
config: hexagon-allmodconfig (https://download.01.org/0day-ci/archive/20231119/202311190108.LDeSe9Lj-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project.git 4a5ac14ee968ff0ad5d2cc1ffa0299048db4c88a)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231119/202311190108.LDeSe9Lj-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/202311190108.LDeSe9Lj-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from fs/qnx4/inode.c:20:
   In file included from include/linux/pagemap.h:11:
   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:337:
   include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     547 |         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]
     560 |         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'
      37 | #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
         |                                                   ^
   In file included from fs/qnx4/inode.c:20:
   In file included from include/linux/pagemap.h:11:
   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:337:
   include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     573 |         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'
      35 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
         |                                                   ^
   In file included from fs/qnx4/inode.c:20:
   In file included from include/linux/pagemap.h:11:
   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:337:
   include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     584 |         __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]
     594 |         __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]
     604 |         __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
         |                                                       ~~~~~~~~~~ ^
   In file included from fs/qnx4/inode.c:24:
>> fs/qnx4/qnx4.h:86:51: warning: '_Static_assert' with no message is a C2x extension [-Wc2x-extensions]
      86 |                offsetof(struct qnx4_link_info, dl_status));
         |                                                          ^
         |                                                          , ""
   fs/qnx4/qnx4.h:88:56: warning: '_Static_assert' with no message is a C2x extension [-Wc2x-extensions]
      88 |                offsetof(union qnx4_directory_entry, de_status));
         |                                                               ^
         |                                                               , ""
   8 warnings generated.


vim +/_Static_assert +86 fs/qnx4/qnx4.h

    47	
    48	/*
    49	 * A qnx4 directory entry is an inode entry or link info
    50	 * depending on the status field in the last byte. The
    51	 * first byte is where the name start either way, and a
    52	 * zero means it's empty.
    53	 *
    54	 * Also, due to a bug in gcc, we don't want to use the
    55	 * real (differently sized) name arrays in the inode and
    56	 * link entries, but always the 'de_name[]' one in the
    57	 * fake struct entry.
    58	 *
    59	 * See
    60	 *
    61	 *   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
    62	 *
    63	 * for details, but basically gcc will take the size of the
    64	 * 'name' array from one of the used union entries randomly.
    65	 *
    66	 * This use of 'de_name[]' (48 bytes) avoids the false positive
    67	 * warnings that would happen if gcc decides to use 'inode.di_name'
    68	 * (16 bytes) even when the pointer and size were to come from
    69	 * 'link.dl_name' (48 bytes).
    70	 *
    71	 * In all cases the actual name pointer itself is the same, it's
    72	 * only the gcc internal 'what is the size of this field' logic
    73	 * that can get confused.
    74	 */
    75	union qnx4_directory_entry {
    76		struct {
    77			const char de_name[48];
    78			u8 de_pad[15];
    79			u8 de_status;
    80		};
    81		struct qnx4_inode_entry inode;
    82		struct qnx4_link_info link;
    83	};
    84	/* Make sure the status byte is in the same place for all structs. */
    85	_Static_assert(offsetof(struct qnx4_inode_entry, di_status) ==
  > 86		       offsetof(struct qnx4_link_info, dl_status));
    87	_Static_assert(offsetof(struct qnx4_inode_entry, di_status) ==
    88		       offsetof(union qnx4_directory_entry, de_status));
    89	

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