Re: [PATCH v13 3/9] open: O_EMPTYPATH: procfs-less file descriptor re-opening

[Aleksa Sarai <cyphar@cyphar.com>]

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On 2019-10-01, kbuild test robot <lkp@intel.com> wrote:
> Hi Aleksa,
> 
> Thank you for the patch! Yet something to improve:
> 
> [auto build test ERROR on linus/master]
> [cannot apply to v5.4-rc1 next-20190930]
> [if your patch is applied to the wrong git tree, please drop us a note to help
> improve the system. BTW, we also suggest to use '--base' option to specify the
> base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
> 
> url:    https://github.com/0day-ci/linux/commits/Aleksa-Sarai/namei-openat2-2-path-resolution-restrictions/20191001-025628
> config: sparc-allyesconfig (attached as .config)
> compiler: sparc64-linux-gcc (GCC) 7.4.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.4.0 make.cross ARCH=sparc 
> 
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@intel.com>
> 
> All error/warnings (new ones prefixed by >>):
> 
>    In file included from include/linux/kernel.h:11:0,
>                     from include/linux/list.h:9,
>                     from include/linux/wait.h:7,
>                     from include/linux/wait_bit.h:8,
>                     from include/linux/fs.h:6,
>                     from include/uapi/linux/aio_abi.h:31,
>                     from include/linux/syscalls.h:74,
>                     from fs/fcntl.c:8:
>    fs/fcntl.c: In function 'fcntl_init':
> >> include/linux/compiler.h:350:38: error: call to '__compiletime_assert_1037' declared with attribute error: BUILD_BUG_ON failed: 22 - 1 != HWEIGHT32( (VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) | __FMODE_EXEC | __FMODE_NONOTIFY)
>      _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
>                                          ^
>    include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert'
>        prefix ## suffix();    \
>        ^~~~~~
>    include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert'
>      _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
>      ^~~~~~~~~~~~~~~~~~~
>    include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
>     #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>                                         ^~~~~~~~~~~~~~~~~~
>    include/linux/build_bug.h:50:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
>      BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
>      ^~~~~~~~~~~~~~~~
> >> fs/fcntl.c:1034:2: note: in expansion of macro 'BUILD_BUG_ON'
>      BUILD_BUG_ON(22 - 1 /* for O_RDONLY being 0 */ !=
>      ^~~~~~~~~~~~

This is because 0x4000000 is used by FMODE_NONOTIFY. The fix is simple,
and I'll include it in the next version.

> vim +/__compiletime_assert_1037 +350 include/linux/compiler.h
> 
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  336  
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  337  #define _compiletime_assert(condition, msg, prefix, suffix) \
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  338  	__compiletime_assert(condition, msg, prefix, suffix)
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  339  
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  340  /**
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  341   * compiletime_assert - break build and emit msg if condition is false
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  342   * @condition: a compile-time constant condition to check
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  343   * @msg:       a message to emit if condition is false
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  344   *
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  345   * In tradition of POSIX assert, this macro will break the build if the
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  346   * supplied condition is *false*, emitting the supplied error message if the
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  347   * compiler has support to do so.
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  348   */
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  349  #define compiletime_assert(condition, msg) \
> 9a8ab1c39970a4 Daniel Santos 2013-02-21 @350  	_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
> 9a8ab1c39970a4 Daniel Santos 2013-02-21  351  
> 
> :::::: The code at line 350 was first introduced by commit
> :::::: 9a8ab1c39970a4938a72d94e6fd13be88a797590 bug.h, compiler.h: introduce compiletime_assert & BUILD_BUG_ON_MSG
> 
> :::::: TO: Daniel Santos <daniel.santos@pobox.com>
> :::::: CC: Linus Torvalds <torvalds@linux-foundation.org>
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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