Re: [PATCH v2] x86/mm/pat: use pr_warn() for early W^X warnings

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

Hi Mike,

kernel test robot noticed the following build errors:

[auto build test ERROR on ebaf7c9bbb1e16523d7036e7e1225ad2dfcc6482]

url:    https://github.com/intel-lab-lkp/linux/commits/Mike-Rapoport-Microsoft/x86-mm-pat-use-pr_warn-for-early-W-X-warnings/20260911-142843
base:   ebaf7c9bbb1e16523d7036e7e1225ad2dfcc6482
patch link:    https://lore.kernel.org/r/20260911-fixes-verify-rwx-v2-1-e2cde39b6693%40kernel.org
patch subject: [PATCH v2] x86/mm/pat: use pr_warn() for early W^X warnings
config: x86_64-allnoconfig (https://download.01.org/0day-ci/archive/20260912/202609120952.vcYnJp5p-lkp@intel.com/config)
compiler: clang version 22.1.3 (https://github.com/llvm/llvm-project e9846648fd6183ee6d8cbdb4502213fcf902a211)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260912/202609120952.vcYnJp5p-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/202609120952.vcYnJp5p-lkp@intel.com/

All errors (new ones prefixed by >>):

>> arch/x86/mm/pat/set_memory.c:708:16: error: expected ')'
     708 |                 pr_warn_once(1, "CPA detected W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n",
         |                              ^
   arch/x86/mm/pat/set_memory.c:708:3: note: to match this '('
     708 |                 pr_warn_once(1, "CPA detected W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n",
         |                 ^
   include/linux/printk.h:669:2: note: expanded from macro 'pr_warn_once'
     669 |         printk_once(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
         |         ^
   include/linux/printk.h:650:15: note: expanded from macro 'printk_once'
     650 |         DO_ONCE_LITE(printk, fmt, ##__VA_ARGS__)
         |                      ^
   1 error generated.


vim +708 arch/x86/mm/pat/set_memory.c

   667	
   668	/*
   669	 * Validate strict W^X semantics.
   670	 */
   671	static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long start,
   672					  unsigned long pfn, unsigned long npg,
   673					  bool nx, bool rw)
   674	{
   675		unsigned long end;
   676	
   677		/*
   678		 * 32-bit has some unfixable W+X issues, like EFI code
   679		 * and writeable data being in the same page.  Disable
   680		 * detection and enforcement there.
   681		 */
   682		if (IS_ENABLED(CONFIG_X86_32))
   683			return new;
   684	
   685		/* Only verify when NX is supported: */
   686		if (!(__supported_pte_mask & _PAGE_NX))
   687			return new;
   688	
   689		if (!((pgprot_val(old) ^ pgprot_val(new)) & (_PAGE_RW | _PAGE_NX)))
   690			return new;
   691	
   692		if ((pgprot_val(new) & (_PAGE_RW | _PAGE_NX)) != _PAGE_RW)
   693			return new;
   694	
   695		/* Non-leaf translation entries can disable writing or execution. */
   696		if (!rw || nx)
   697			return new;
   698	
   699		end = start + npg * PAGE_SIZE - 1;
   700	
   701		/*
   702		 * If the kernel text is still RWX, gently complain, this could be a
   703		 * false positive.
   704		 * Once debug_checkwx() becomes mandatory for CONFIG_STRICT_KERNEL_RWX,
   705		 * the warning can be removed completely.
   706		 */
   707		if (!kernel_set_to_readonly) {
 > 708			pr_warn_once(1, "CPA detected W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n",
   709			  (unsigned long long)pgprot_val(old),
   710			  (unsigned long long)pgprot_val(new),
   711			  start, end, pfn);
   712			return new;
   713		}
   714	
   715		WARN_ONCE(1, "CPA detected W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n",
   716			  (unsigned long long)pgprot_val(old),
   717			  (unsigned long long)pgprot_val(new),
   718			  start, end, pfn);
   719	
   720		/*
   721		 * For now, allow all permission change attempts by returning the
   722		 * attempted permissions.  This can 'return old' to actively
   723		 * refuse the permission change at a later time.
   724		 */
   725		return new;
   726	}
   727	

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