Re: [PATCH v6 23/30] arm64: kpkeys: Ensure the linear map can be modified

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

Hi Kevin,

kernel test robot noticed the following build errors:

[auto build test ERROR on 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f]

url:    https://github.com/intel-lab-lkp/linux/commits/Kevin-Brodsky/mm-Introduce-kpkeys/20260228-020115
base:   6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
patch link:    https://lore.kernel.org/r/20260227175518.3728055-24-kevin.brodsky%40arm.com
patch subject: [PATCH v6 23/30] arm64: kpkeys: Ensure the linear map can be modified
config: arm64-randconfig-001-20260228 (https://download.01.org/0day-ci/archive/20260228/202602280610.KQRFmbR3-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 9a109fbb6e184ec9bcce10615949f598f4c974a9)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260228/202602280610.KQRFmbR3-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/202602280610.KQRFmbR3-lkp@intel.com/

All errors (new ones prefixed by >>):

>> arch/arm64/mm/pageattr.c:100:3: error: call to undeclared function 'arm64_supports_kpkeys_hardened_pgtables'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     100 |                 arm64_supports_kpkeys_hardened_pgtables();
         |                 ^
   1 error generated.
--
>> arch/arm64/mm/mmu.c:768:3: error: call to undeclared function 'arm64_supports_kpkeys_hardened_pgtables'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     768 |                 arm64_supports_kpkeys_hardened_pgtables();
         |                 ^
   1 error generated.


vim +/arm64_supports_kpkeys_hardened_pgtables +100 arch/arm64/mm/pageattr.c

    86	
    87	bool can_set_direct_map(void)
    88	{
    89		/*
    90		 * rodata_full, DEBUG_PAGEALLOC and a Realm guest all require linear
    91		 * map to be mapped at page granularity, so that it is possible to
    92		 * protect/unprotect single pages.
    93		 *
    94		 * KFENCE pool requires page-granular mapping if initialized late.
    95		 *
    96		 * Realms need to make pages shared/protected at page granularity.
    97		 */
    98		return rodata_full || debug_pagealloc_enabled() ||
    99			arm64_kfence_can_set_direct_map() || is_realm_world() ||
 > 100			arm64_supports_kpkeys_hardened_pgtables();
   101	}
   102	

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