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Message-ID: <202505240038.q8Dcx2LG-lkp@intel.com>
Date: Sat, 24 May 2025 00:37:55 +0800
From: kernel test robot <lkp@...el.com>
To: Benjamin Berg <benjamin.berg@...el.com>
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
linux-kernel@...r.kernel.org,
Johannes Berg <johannes.berg@...el.com>
Subject: arch/um/kernel/um_arch.c:336:16: warning: result of comparison of
constant 4294967296 with expression of type 'typeof (task_size)' (aka
'unsigned long') is always false
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 3d0ebc36b0b3e8486ceb6e08e8ae173aaa6d1221
commit: 830003c73d190259e45d0a99a0e3d14cb73e0af0 um: Limit TASK_SIZE to the addressable range
date: 8 months ago
config: um-randconfig-2006-20250515 (https://download.01.org/0day-ci/archive/20250524/202505240038.q8Dcx2LG-lkp@intel.com/config)
compiler: clang version 21.0.0git (https://github.com/llvm/llvm-project f819f46284f2a79790038e1f6649172789734ae8)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250524/202505240038.q8Dcx2LG-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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505240038.q8Dcx2LG-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from arch/um/kernel/um_arch.c:9:
In file included from include/linux/mm.h:2213:
include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
518 | return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
| ~~~~~~~~~~~ ^ ~~~
In file included from arch/um/kernel/um_arch.c:19:
In file included from include/linux/suspend.h:5:
In file included from include/linux/swap.h:9:
In file included from include/linux/memcontrol.h:13:
In file included from include/linux/cgroup.h:26:
In file included from include/linux/kernel_stat.h:8:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from arch/um/include/asm/hardirq.h:5:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:14:
In file included from arch/um/include/asm/io.h:24:
include/asm-generic/io.h:548:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
548 | val = __raw_readb(PCI_IOBASE + addr);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:561:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
561 | val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
| ~~~~~~~~~~ ^
include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
37 | #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
| ^
In file included from arch/um/kernel/um_arch.c:19:
In file included from include/linux/suspend.h:5:
In file included from include/linux/swap.h:9:
In file included from include/linux/memcontrol.h:13:
In file included from include/linux/cgroup.h:26:
In file included from include/linux/kernel_stat.h:8:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from arch/um/include/asm/hardirq.h:5:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:14:
In file included from arch/um/include/asm/io.h:24:
include/asm-generic/io.h:574:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
574 | val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
| ~~~~~~~~~~ ^
include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
35 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
| ^
In file included from arch/um/kernel/um_arch.c:19:
In file included from include/linux/suspend.h:5:
In file included from include/linux/swap.h:9:
In file included from include/linux/memcontrol.h:13:
In file included from include/linux/cgroup.h:26:
In file included from include/linux/kernel_stat.h:8:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from arch/um/include/asm/hardirq.h:5:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:14:
In file included from arch/um/include/asm/io.h:24:
include/asm-generic/io.h:585:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
585 | __raw_writeb(value, PCI_IOBASE + addr);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:595:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
595 | __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:605:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
605 | __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:693:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
693 | readsb(PCI_IOBASE + addr, buffer, count);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:701:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
701 | readsw(PCI_IOBASE + addr, buffer, count);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:709:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
709 | readsl(PCI_IOBASE + addr, buffer, count);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:718:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
718 | writesb(PCI_IOBASE + addr, buffer, count);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:727:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
727 | writesw(PCI_IOBASE + addr, buffer, count);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:736:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
736 | writesl(PCI_IOBASE + addr, buffer, count);
| ~~~~~~~~~~ ^
>> arch/um/kernel/um_arch.c:336:16: warning: result of comparison of constant 4294967296 with expression of type 'typeof (task_size)' (aka 'unsigned long') is always false [-Wtautological-constant-out-of-range-compare]
336 | if (task_size > (unsigned long long) PTRS_PER_PGD * PGDIR_SIZE)
| ~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
14 warnings generated.
vim +336 arch/um/kernel/um_arch.c
304
305 int __init linux_main(int argc, char **argv)
306 {
307 unsigned long avail, diff;
308 unsigned long virtmem_size, max_physmem;
309 unsigned long stack;
310 unsigned int i;
311 int add;
312
313 for (i = 1; i < argc; i++) {
314 if ((i == 1) && (argv[i][0] == ' '))
315 continue;
316 add = 1;
317 uml_checksetup(argv[i], &add);
318 if (add)
319 add_arg(argv[i]);
320 }
321 if (have_root == 0)
322 add_arg(DEFAULT_COMMAND_LINE_ROOT);
323
324 if (have_console == 0)
325 add_arg(DEFAULT_COMMAND_LINE_CONSOLE);
326
327 host_task_size = os_get_top_address();
328 /* reserve a few pages for the stubs */
329 stub_start = host_task_size - STUB_DATA_PAGES * PAGE_SIZE;
330 /* another page for the code portion */
331 stub_start -= PAGE_SIZE;
332 host_task_size = stub_start;
333
334 /* Limit TASK_SIZE to what is addressable by the page table */
335 task_size = host_task_size;
> 336 if (task_size > (unsigned long long) PTRS_PER_PGD * PGDIR_SIZE)
337 task_size = PTRS_PER_PGD * PGDIR_SIZE;
338
339 /*
340 * TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps
341 * out
342 */
343 task_size = task_size & PGDIR_MASK;
344
345 /* OS sanity checks that need to happen before the kernel runs */
346 os_early_checks();
347
348 get_host_cpu_features(parse_host_cpu_flags, parse_cache_line);
349
350 brk_start = (unsigned long) sbrk(0);
351
352 /*
353 * Increase physical memory size for exec-shield users
354 * so they actually get what they asked for. This should
355 * add zero for non-exec shield users
356 */
357
358 diff = UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
359 if (diff > 1024 * 1024) {
360 os_info("Adding %ld bytes to physical memory to account for "
361 "exec-shield gap\n", diff);
362 physmem_size += UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
363 }
364
365 uml_physmem = (unsigned long) __binary_start & PAGE_MASK;
366
367 /* Reserve up to 4M after the current brk */
368 uml_reserved = ROUND_4M(brk_start) + (1 << 22);
369
370 setup_machinename(init_utsname()->machine);
371
372 physmem_size = (physmem_size + PAGE_SIZE - 1) & PAGE_MASK;
373 iomem_size = (iomem_size + PAGE_SIZE - 1) & PAGE_MASK;
374
375 max_physmem = TASK_SIZE - uml_physmem - iomem_size - MIN_VMALLOC;
376
377 if (physmem_size + iomem_size > max_physmem) {
378 physmem_size = max_physmem - iomem_size;
379 os_info("Physical memory size shrunk to %llu bytes\n",
380 physmem_size);
381 }
382
383 high_physmem = uml_physmem + physmem_size;
384 end_iomem = high_physmem + iomem_size;
385 high_memory = (void *) end_iomem;
386
387 start_vm = VMALLOC_START;
388
389 virtmem_size = physmem_size;
390 stack = (unsigned long) argv;
391 stack &= ~(1024 * 1024 - 1);
392 avail = stack - start_vm;
393 if (physmem_size > avail)
394 virtmem_size = avail;
395 end_vm = start_vm + virtmem_size;
396
397 if (virtmem_size < physmem_size)
398 os_info("Kernel virtual memory size shrunk to %lu bytes\n",
399 virtmem_size);
400
401 os_flush_stdout();
402
403 return start_uml();
404 }
405
--
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https://github.com/intel/lkp-tests/wiki
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