linux-kernel - Re: [atishp04:ox_v5.14_working 4/13] arch/riscv/mm/init.c:714:83: warning: suggest braces around empty body in an 'if' statement

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Date:   Fri, 5 Nov 2021 09:30:39 +0100
From:   Alexandre Ghiti <alexandre.ghiti@...onical.com>
To:     kernel test robot <lkp@...el.com>
Cc:     kbuild-all@...ts.01.org, Atish Patra <atish.patra@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [atishp04:ox_v5.14_working 4/13] arch/riscv/mm/init.c:714:83:
 warning: suggest braces around empty body in an 'if' statement

On Fri, Nov 5, 2021 at 9:20 AM kernel test robot <lkp@...el.com> wrote:
>
> tree:   https://github.com/atishp04/linux ox_v5.14_working
> head:   9d2e326476c44eade0d6b7ee54c4eb8918d6aa94
> commit: 7c0cb480378b7fc7ccc693fc867c4d62c420732d [4/13] riscv: Implement sv48 support
> config: riscv-rv32_defconfig (attached as .config)
> compiler: riscv32-linux-gcc (GCC) 11.2.0
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://github.com/atishp04/linux/commit/7c0cb480378b7fc7ccc693fc867c4d62c420732d
>         git remote add atishp04 https://github.com/atishp04/linux
>         git fetch --no-tags atishp04 ox_v5.14_working
>         git checkout 7c0cb480378b7fc7ccc693fc867c4d62c420732d
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=riscv
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
>    arch/riscv/mm/init.c: In function 'create_fdt_early_page_table':
> >> arch/riscv/mm/init.c:714:83: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]
>      714 |                                    (uintptr_t)early_dtb_pmd, PUD_SIZE, PAGE_TABLE);
>          |                                                                                   ^
>

Indeed, create_pud_mapping is an empty macro in 32-bit, I'll fix that
in the next version.

Thanks,

Alex

>
> vim +/if +714 arch/riscv/mm/init.c
>
>    696
>    697  /*
>    698   * Setup a 4MB mapping that encompasses the device tree: for 64-bit kernel,
>    699   * this means 2 PMD entries whereas for 32-bit kernel, this is only 1 PGDIR
>    700   * entry.
>    701   */
>    702  static void __init create_fdt_early_page_table(pgd_t *pgdir, uintptr_t dtb_pa)
>    703  {
>    704  #ifndef CONFIG_BUILTIN_DTB
>    705          uintptr_t pa = dtb_pa & ~(PMD_SIZE - 1);
>    706
>    707          create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA,
>    708                             IS_ENABLED(CONFIG_64BIT) ? early_dtb_pgd_next : pa,
>    709                             PGDIR_SIZE,
>    710                             IS_ENABLED(CONFIG_64BIT) ? PAGE_TABLE : PAGE_KERNEL);
>    711
>    712          if (pgtable_l4_enabled)
>    713                  create_pud_mapping(early_dtb_pud, DTB_EARLY_BASE_VA,
>  > 714                                     (uintptr_t)early_dtb_pmd, PUD_SIZE, PAGE_TABLE);
>    715
>    716          if (IS_ENABLED(CONFIG_64BIT)) {
>    717                  create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA,
>    718                                     pa, PMD_SIZE, PAGE_KERNEL);
>    719                  create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA + PMD_SIZE,
>    720                                     pa + PMD_SIZE, PMD_SIZE, PAGE_KERNEL);
>    721          }
>    722
>    723          dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PMD_SIZE - 1));
>    724  #else
>    725          /*
>    726           * For 64-bit kernel, __va can't be used since it would return a linear
>    727           * mapping address whereas dtb_early_va will be used before
>    728           * setup_vm_final installs the linear mapping. For 32-bit kernel, as the
>    729           * kernel is mapped in the linear mapping, that makes no difference.
>    730           */
>    731          dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
>    732  #endif
>    733
>    734          dtb_early_pa = dtb_pa;
>    735  }
>    736
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org