On 6/6/21 1:08 PM, Hyeonggon Yoo wrote:
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/commi...
> 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(a)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.
But what exactly is the gcc problem here?
Did you have to reproduce it with specific gcc version and/or architecture?
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)
I wonder how this extra guard can possibly matter?
bpf_map_kmalloc_node()
kmalloc_node()
if (__builtin_constant_p(size) ...)
unsigned int i = kmalloc_index(size);
We shouldn't be even reaching kmalloc_index() unless __builtin_constant_p(size)
is already 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.
If bpf_map_kmalloc_node() is not being compiled as inline, how can it possibly
evaluate __builtin_constant_p(size) as true when processing the inlined
kmalloc_node()?
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)
{