Re: [net-next:main 13/66] include/linux/compiler_types.h:460:45: error: call to '__compiletime_assert_654' declared with attribute error: BUILD_BUG_ON failed: !IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed), sizeof(u32))

[Alexander Lobakin <aleksander.lobakin@intel.com>]

From: Kernel Test Robot <lkp@intel.com>
Date: Tue, 14 May 2024 15:53:43 +0800

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git main
> head:   5c1672705a1a2389f5ad78e0fea6f08ed32d6f18
> commit: 4b0ebbca3e1679765c06d5c466ee7f3228d4b156 [13/66] net: gro: move L3 flush checks to tcp_gro_receive and udp_gro_receive_segment
> config: m68k-mvme16x_defconfig (https://download.01.org/0day-ci/archive/20240514/202405141504.J6WdljEp-lkp@intel.com/config)
> compiler: m68k-linux-gcc (GCC) 13.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240514/202405141504.J6WdljEp-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@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202405141504.J6WdljEp-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from <command-line>:
>    net/core/gro.c: In function 'dev_gro_receive':
>>> include/linux/compiler_types.h:460:45: error: call to '__compiletime_assert_654' declared with attribute error: BUILD_BUG_ON failed: !IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed), sizeof(u32))

Hi Richard,

In the mentioned commit, you moved some fields placed before
napi_gro_cb::zeroed and seems like on some architectures this misplaced
napi_gro_cb::zeroed and it's not aligned to 4 bytes there anymore.
Since ::zeroed is used as one u32 to quickly zero the hot fields,
it must be aligned to 4 to avoid slow unaligned accesses.
Which means you need to move some more fields around a bit, so that its
offset would again be aligned to 4.

>      460 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>          |                                             ^
>    include/linux/compiler_types.h:441:25: note: in definition of macro '__compiletime_assert'
>      441 |                         prefix ## suffix();                             \
>          |                         ^~~~~~
>    include/linux/compiler_types.h:460:9: note: in expansion of macro '_compiletime_assert'
>      460 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>          |         ^~~~~~~~~~~~~~~~~~~
>    include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
>       39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>          |                                     ^~~~~~~~~~~~~~~~~~
>    include/linux/build_bug.h:50:9: note: in expansion of macro 'BUILD_BUG_ON_MSG'
>       50 |         BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
>          |         ^~~~~~~~~~~~~~~~
>    net/core/gro.c:496:9: note: in expansion of macro 'BUILD_BUG_ON'
>      496 |         BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed),
>          |         ^~~~~~~~~~~~
> 
> 
> vim +/__compiletime_assert_654 +460 include/linux/compiler_types.h
> 
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  446  
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  447  #define _compiletime_assert(condition, msg, prefix, suffix) \
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  448  	__compiletime_assert(condition, msg, prefix, suffix)
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  449  
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  450  /**
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  451   * compiletime_assert - break build and emit msg if condition is false
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  452   * @condition: a compile-time constant condition to check
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  453   * @msg:       a message to emit if condition is false
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  454   *
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  455   * In tradition of POSIX assert, this macro will break the build if the
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  456   * supplied condition is *false*, emitting the supplied error message if the
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  457   * compiler has support to do so.
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  458   */
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  459  #define compiletime_assert(condition, msg) \
> eb5c2d4b45e3d2 Will Deacon 2020-07-21 @460  	_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> eb5c2d4b45e3d2 Will Deacon 2020-07-21  461  
> 
> :::::: The code at line 460 was first introduced by commit
> :::::: eb5c2d4b45e3d2d5d052ea6b8f1463976b1020d5 compiler.h: Move compiletime_assert() macros into compiler_types.h
> 
> :::::: TO: Will Deacon <will@kernel.org>
> :::::: CC: Will Deacon <will@kernel.org>

Thanks,
Olek