Re: [linux-next:master 7012/7430] include/linux/compiler_types.h:328:38: error: call to '__compiletime_assert_183' declared with attribute error: unexpected size in kmalloc_index()

[Hyeonggon Yoo <42.hyeyoo@gmail.com>]

On Sat, Jun 05, 2021 at 02:10:46PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head:   ccc252d2e818f6a479441119ad453c3ce7c7c461
> commit: a7ba988ff9de37f0961b4bf96d17aca73d0d2e25 [7012/7430] mm, slub: change run-time assertion in kmalloc_index() to compile-time
> config: parisc-randconfig-r014-20210604 (attached as .config)
> compiler: hppa-linux-gcc (GCC) 9.3.0
> 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://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=a7ba988ff9de37f0961b4bf96d17aca73d0d2e25
>         git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
>         git fetch --no-tags linux-next master
>         git checkout a7ba988ff9de37f0961b4bf96d17aca73d0d2e25
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=parisc 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
>    In file included from <command-line>:
>    In function 'kmalloc_index',
>        inlined from 'kmalloc_node' at include/linux/slab.h:572:20,
>        inlined from 'bpf_map_kmalloc_node.isra.0.part.0' at include/linux/bpf.h:1319:9:
> >> include/linux/compiler_types.h:328:38: error: call to '__compiletime_assert_183' declared with attribute error: unexpected size in kmalloc_index()
>      328 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>          |                                      ^
>    include/linux/compiler_types.h:309:4: note: in definition of macro '__compiletime_assert'
>      309 |    prefix ## suffix();    \
>          |    ^~~~~~
>    include/linux/compiler_types.h:328:2: note: in expansion of macro '_compiletime_assert'
>      328 |  _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/slab.h:389:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
>      389 |  BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");
>          |  ^~~~~~~~~~~~~~~~

Reproduce with attached config, and read the code.
It has no problem in clang (clang-10/clang-11). it is problem with gcc.

I found two ways to solve the error (maybe there would be better
solution)  Any thoughts or opinions?


First ways is to change condition of kmalloc_index macro.

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 70e46db766ca..be2c900cba4b 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -397,7 +397,7 @@ static __always_inline unsigned int __kmalloc_index(size_t size,
        /* Will never be reached. Needed because the compiler may complain */
        return -1;
 }
-#define kmalloc_index(s) __kmalloc_index(s, true)
+#define kmalloc_index(s) __kmalloc_index(s, __builtin_constant_p(s) && true)
 #endif /* !CONFIG_SLOB */
 
 void *__kmalloc(size_t size, gfp_t flags) __assume_kmalloc_alignment __malloc;


Second way is making bpf_map_kmalloc_node always inline.

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 02b02cb29ce2..09379d705349 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1312,7 +1312,7 @@ void *bpf_map_kzalloc(const struct bpf_map *map, size_t size, gfp_t flags);
 void __percpu *bpf_map_alloc_percpu(const struct bpf_map *map, size_t size,
                                    size_t align, gfp_t flags);
 #else
-static inline void *
+static __always_inline void *
 bpf_map_kmalloc_node(const struct bpf_map *map, size_t size, gfp_t flags,
                     int node)
 {