Hi "Christopher, Thank you for the patch! Yet something to improve: [auto build test ERROR on powerpc/next] [also build test ERROR on char-misc/char-misc-testing tip/x86/core v5.9-rc2 next-20200827] [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] url: https://github.com/0day-ci/linux/commits/Christopher-M-Riedl/Use-per-CPU-temporary-mappings-for-patching/20200827-161532 base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next config: x86_64-allmodconfig (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 reproduce (this is a W=1 build): # save the attached .config to linux build tree make W=1 ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp@xxxxxxxxx> All errors (new ones prefixed by >>): drivers/misc/lkdtm/perms.c: In function 'lkdtm_HIJACK_PATCH': >> drivers/misc/lkdtm/perms.c:318:38: error: implicit declaration of function 'read_cpu_patching_addr' [-Werror=implicit-function-declaration] 318 | addr = offset_in_page(patch_site) | read_cpu_patching_addr(patching_cpu); | ^~~~~~~~~~~~~~~~~~~~~~ cc1: some warnings being treated as errors # https://github.com/0day-ci/linux/commit/36a98d779ee4620e6e091cbe3b438b52faa108ad git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Christopher-M-Riedl/Use-per-CPU-temporary-mappings-for-patching/20200827-161532 git checkout 36a98d779ee4620e6e091cbe3b438b52faa108ad vim +/read_cpu_patching_addr +318 drivers/misc/lkdtm/perms.c 289 290 void lkdtm_HIJACK_PATCH(void) 291 { 292 #ifdef CONFIG_PPC 293 struct ppc_inst original_insn = ppc_inst_read(READ_ONCE(patch_site)); 294 #endif 295 #ifdef CONFIG_X86_64 296 int original_insn = READ_ONCE(*patch_site); 297 #endif 298 struct task_struct *patching_kthrd; 299 int patching_cpu, hijacker_cpu, attempts; 300 unsigned long addr; 301 bool hijacked; 302 const int bad_data = 0xbad00bad; 303 304 if (num_online_cpus() < 2) { 305 pr_warn("need at least two cpus\n"); 306 return; 307 } 308 309 hijacker_cpu = smp_processor_id(); 310 patching_cpu = cpumask_any_but(cpu_online_mask, hijacker_cpu); 311 312 patching_kthrd = kthread_create_on_node(&lkdtm_patching_cpu, NULL, 313 cpu_to_node(patching_cpu), 314 "lkdtm_patching_cpu"); 315 kthread_bind(patching_kthrd, patching_cpu); 316 wake_up_process(patching_kthrd); 317 > 318 addr = offset_in_page(patch_site) | read_cpu_patching_addr(patching_cpu); 319 320 pr_info("starting hijacker_cpu=%d\n", hijacker_cpu); 321 for (attempts = 0; attempts < 100000; ++attempts) { 322 /* Use __put_user to catch faults without an Oops */ 323 hijacked = !__put_user(bad_data, (int *)addr); 324 325 if (hijacked) { 326 if (kthread_stop(patching_kthrd)) 327 pr_err("error trying to stop patching thread\n"); 328 break; 329 } 330 } 331 pr_info("hijack attempts: %d\n", attempts); 332 333 if (hijacked) { 334 if (lkdtm_verify_patch(bad_data)) 335 pr_err("overwrote kernel text\n"); 336 /* 337 * There are window conditions where the hijacker cpu manages to 338 * write to the patch site but the site gets overwritten again by 339 * the patching cpu. We still consider that a "successful" hijack 340 * since the hijacker cpu did not fault on the write. 341 */ 342 pr_err("FAIL: wrote to another cpu's patching area\n"); 343 } else { 344 kthread_stop(patching_kthrd); 345 } 346 347 /* Restore the original insn for any future lkdtm tests */ 348 #ifdef CONFIG_PPC 349 patch_instruction(patch_site, original_insn); 350 #endif 351 #ifdef CONFIG_X86_64 352 lkdtm_do_patch(original_insn); 353 #endif 354 } 355 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx
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