include/linux/kern_levels.h:5:25: warning: '%s' directive argument is null

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

Hi Hans,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   1e15510b71c99c6e49134d756df91069f7d18141
commit: 59833696442c674acbbd297772ba89e7ad8c753d iommu/vt-d: dmar: replace WARN_TAINT with pr_warn + add_taint
date:   5 years ago
config: x86_64-randconfig-161-20230920 (https://download.01.org/0day-ci/archive/20250228/202502281256.H66NjDMW-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250228/202502281256.H66NjDMW-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/202502281256.H66NjDMW-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from include/linux/printk.h:7,
                    from include/linux/kernel.h:15,
                    from include/asm-generic/bug.h:19,
                    from arch/x86/include/asm/bug.h:83,
                    from include/linux/bug.h:5,
                    from include/linux/jump_label.h:250,
                    from arch/x86/include/asm/string_64.h:6,
                    from arch/x86/include/asm/string.h:5,
                    from include/linux/string.h:20,
                    from include/linux/uuid.h:12,
                    from include/linux/mod_devicetable.h:13,
                    from include/linux/pci.h:27,
                    from drivers/iommu/dmar.c:19:
   drivers/iommu/dmar.c: In function 'dmar_parse_one_andd':
>> include/linux/kern_levels.h:5:25: warning: '%s' directive argument is null [-Wformat-overflow=]
       5 | #define KERN_SOH        "\001"          /* ASCII Start Of Header */
         |                         ^~~~~~
   include/linux/kern_levels.h:12:25: note: in expansion of macro 'KERN_SOH'
      12 | #define KERN_WARNING    KERN_SOH "4"    /* warning conditions */
         |                         ^~~~~~~~
   include/linux/printk.h:306:16: note: in expansion of macro 'KERN_WARNING'
     306 |         printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
         |                ^~~~~~~~~~~~
   drivers/iommu/dmar.c:444:17: note: in expansion of macro 'pr_warn'
     444 |                 pr_warn(FW_BUG
         |                 ^~~~~~~
   drivers/iommu/dmar.c: In function 'warn_invalid_dmar':
>> include/linux/kern_levels.h:5:25: warning: '%s' directive argument is null [-Wformat-overflow=]
       5 | #define KERN_SOH        "\001"          /* ASCII Start Of Header */
         |                         ^~~~~~
   include/linux/printk.h:356:24: note: in definition of macro 'printk_once'
     356 |                 printk(fmt, ##__VA_ARGS__);                     \
         |                        ^~~
   include/linux/kern_levels.h:12:25: note: in expansion of macro 'KERN_SOH'
      12 | #define KERN_WARNING    KERN_SOH "4"    /* warning conditions */
         |                         ^~~~~~~~
   include/linux/printk.h:387:21: note: in expansion of macro 'KERN_WARNING'
     387 |         printk_once(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
         |                     ^~~~~~~~~~~~
   drivers/iommu/dmar.c:832:9: note: in expansion of macro 'pr_warn_once'
     832 |         pr_warn_once(FW_BUG
         |         ^~~~~~~~~~~~


vim +5 include/linux/kern_levels.h

314ba3520e513a Joe Perches 2012-07-30  4  
04d2c8c83d0e3a Joe Perches 2012-07-30 @5  #define KERN_SOH	"\001"		/* ASCII Start Of Header */
04d2c8c83d0e3a Joe Perches 2012-07-30  6  #define KERN_SOH_ASCII	'\001'
04d2c8c83d0e3a Joe Perches 2012-07-30  7  

:::::: The code at line 5 was first introduced by commit
:::::: 04d2c8c83d0e3ac5f78aeede51babb3236200112 printk: convert the format for KERN_<LEVEL> to a 2 byte pattern

:::::: TO: Joe Perches <joe@perches.com>
:::::: CC: Linus Torvalds <torvalds@linux-foundation.org>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki