Hi Tetsuo, FYI, the error/warning still remains. tree: https://android.googlesource.com/kernel/common android-3.18 head: a406f39320f095aa4628bb50aba12da25d5d0943 commit: d8d7791979c3d6045b0904ddf8e17970401a5a80 [12862/16064] /dev/mem: Bail out upon SIGKILL. config: x86_64-randconfig-a016-20200824 (attached as .config) compiler: gcc-5 (Ubuntu 5.5.0-12ubuntu1) 5.5.0 20171010 reproduce (this is a W=1 build): git checkout d8d7791979c3d6045b0904ddf8e17970401a5a80 # 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(a)intel.com&gt; All errors (new ones prefixed by >>): drivers/char/mem.c: In function 'read_kmem': if (should_stop_iteration()) { ^ cc1: some warnings being treated as errors git remote add android-common https://android.googlesource.com/kernel/common git fetch --no-tags android-common android-3.18 git checkout d8d7791979c3d6045b0904ddf8e17970401a5a80 vim +/should_stop_iteration +457 drivers/char/mem.c 408 409 #ifdef CONFIG_DEVKMEM 410 /* 411 * This function reads the *virtual* memory as seen by the kernel. 412 */ 413 static ssize_t read_kmem(struct file *file, char __user *buf, 414 size_t count, loff_t *ppos) 415 { 416 unsigned long p = *ppos; 417 ssize_t low_count, read, sz; 418 char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */ 419 int err = 0; 420 421 read = 0; 422 if (p < (unsigned long) high_memory) { 423 low_count = count; 424 if (count > (unsigned long)high_memory - p) 425 low_count = (unsigned long)high_memory - p; 426 427 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED 428 /* we don't have page 0 mapped on sparc and m68k.. */ 429 if (p < PAGE_SIZE && low_count > 0) { 430 sz = size_inside_page(p, low_count); 431 if (clear_user(buf, sz)) 432 return -EFAULT; 433 buf += sz; 434 p += sz; 435 read += sz; 436 low_count -= sz; 437 count -= sz; 438 } 439 #endif 440 while (low_count > 0) { 441 sz = size_inside_page(p, low_count); 442 443 /* 444 * On ia64 if a page has been mapped somewhere as 445 * uncached, then it must also be accessed uncached 446 * by the kernel or data corruption may occur 447 */ 448 kbuf = xlate_dev_kmem_ptr((char *)p); 449 450 if (copy_to_user(buf, kbuf, sz)) 451 return -EFAULT; 452 buf += sz; 453 p += sz; 454 read += sz; 455 low_count -= sz; 456 count -= sz; 458 count = 0; 459 break; 460 } 461 } 462 } 463 464 if (count > 0) { 465 kbuf = (char *)__get_free_page(GFP_KERNEL); 466 if (!kbuf) 467 return -ENOMEM; 468 while (count > 0) { 469 sz = size_inside_page(p, count); 470 if (!is_vmalloc_or_module_addr((void *)p)) { 471 err = -ENXIO; 472 break; 473 } 474 sz = vread(kbuf, (char *)p, sz); 475 if (!sz) 476 break; 477 if (copy_to_user(buf, kbuf, sz)) { 478 err = -EFAULT; 479 break; 480 } 481 count -= sz; 482 buf += sz; 483 read += sz; 484 p += sz; 485 if (should_stop_iteration()) 486 break; 487 } 488 free_page((unsigned long)kbuf); 489 } 490 *ppos = p; 491 return read ? read : err; 492 } 493 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org