arch/mips/mm/tlbex.c:2599 check_pabits() warn: always true condition '(fillbits >= ((__builtin_constant_p(0)) ?(((0) < 2) ?0:63 - __builtin_clzll(0)):((4 <= 4)) ?__ilog2_u32(0):__ilog2_u64(0))) => (0-u32max >= 0)'

From: kernel test robot
Date: Sat Nov 27 2021 - 23:50:24 EST

tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 3498e7f2bb415e447354a3debef6738d9655768c
commit: 2f78788b55baa3410b1ec91a576286abe1ad4d6a ilog2: improve ilog2 for constant arguments
date: 12 months ago
config: mips-randconfig-m031-20211123 (https://download.01.org/0day-ci/archive/20211128/202111281203.l0V4WbS0-lkp@xxxxxxxxx/config)
compiler: mips-linux-gcc (GCC) 11.2.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

New smatch warnings:
arch/mips/mm/tlbex.c:2599 check_pabits() warn: always true condition '(fillbits >= ((__builtin_constant_p(0)) ?(((0) < 2) ?0:63 - __builtin_clzll(0)):((4 <= 4)) ?__ilog2_u32(0):__ilog2_u64(0))) => (0-u32max >= 0)'

Old smatch warnings:
arch/mips/mm/tlbex.c:1681 iPTE_LW() warn: curly braces intended?
arch/mips/mm/tlbex.c:1713 iPTE_SW() warn: inconsistent indenting

vim +2599 arch/mips/mm/tlbex.c

c5b367835cfc7a Steven J. Hill 2015-02-26 2569
00bf1c691d082c Paul Burton 2015-09-22 2570 static void check_pabits(void)
00bf1c691d082c Paul Burton 2015-09-22 2571 {
00bf1c691d082c Paul Burton 2015-09-22 2572 unsigned long entry;
00bf1c691d082c Paul Burton 2015-09-22 2573 unsigned pabits, fillbits;
00bf1c691d082c Paul Burton 2015-09-22 2574
00bf1c691d082c Paul Burton 2015-09-22 2575 if (!cpu_has_rixi || !_PAGE_NO_EXEC) {
00bf1c691d082c Paul Burton 2015-09-22 2576 /*
00bf1c691d082c Paul Burton 2015-09-22 2577 * We'll only be making use of the fact that we can rotate bits
00bf1c691d082c Paul Burton 2015-09-22 2578 * into the fill if the CPU supports RIXI, so don't bother
00bf1c691d082c Paul Burton 2015-09-22 2579 * probing this for CPUs which don't.
00bf1c691d082c Paul Burton 2015-09-22 2580 */
00bf1c691d082c Paul Burton 2015-09-22 2581 return;
00bf1c691d082c Paul Burton 2015-09-22 2582 }
00bf1c691d082c Paul Burton 2015-09-22 2583
00bf1c691d082c Paul Burton 2015-09-22 2584 write_c0_entrylo0(~0ul);
00bf1c691d082c Paul Burton 2015-09-22 2585 back_to_back_c0_hazard();
00bf1c691d082c Paul Burton 2015-09-22 2586 entry = read_c0_entrylo0();
00bf1c691d082c Paul Burton 2015-09-22 2587
00bf1c691d082c Paul Burton 2015-09-22 2588 /* clear all non-PFN bits */
00bf1c691d082c Paul Burton 2015-09-22 2589 entry &= ~((1 << MIPS_ENTRYLO_PFN_SHIFT) - 1);
00bf1c691d082c Paul Burton 2015-09-22 2590 entry &= ~(MIPS_ENTRYLO_RI | MIPS_ENTRYLO_XI);
00bf1c691d082c Paul Burton 2015-09-22 2591
00bf1c691d082c Paul Burton 2015-09-22 2592 /* find a lower bound on PABITS, and upper bound on fill bits */
00bf1c691d082c Paul Burton 2015-09-22 2593 pabits = fls_long(entry) + 6;
00bf1c691d082c Paul Burton 2015-09-22 2594 fillbits = max_t(int, (int)BITS_PER_LONG - pabits, 0);
00bf1c691d082c Paul Burton 2015-09-22 2595
00bf1c691d082c Paul Burton 2015-09-22 2596 /* minus the RI & XI bits */
00bf1c691d082c Paul Burton 2015-09-22 2597 fillbits -= min_t(unsigned, fillbits, 2);
00bf1c691d082c Paul Burton 2015-09-22 2598
00bf1c691d082c Paul Burton 2015-09-22 @2599 if (fillbits >= ilog2(_PAGE_NO_EXEC))
00bf1c691d082c Paul Burton 2015-09-22 2600 fill_includes_sw_bits = true;
00bf1c691d082c Paul Burton 2015-09-22 2601
00bf1c691d082c Paul Burton 2015-09-22 2602 pr_debug("Entry* registers contain %u fill bits\n", fillbits);
00bf1c691d082c Paul Burton 2015-09-22 2603 }
00bf1c691d082c Paul Burton 2015-09-22 2604

:::::: The code at line 2599 was first introduced by commit
:::::: 00bf1c691d082c1945fdba032c03a9a82e9e7e61 MIPS: tlbex: Avoid placing software PTE bits in Entry* PFN fields

:::::: TO: Paul Burton <paul.burton@xxxxxxxxxx>
:::::: CC: Ralf Baechle <ralf@xxxxxxxxxxxxxx>

---
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