Re: [PATCH v1 2/2] selftests/mm: Guard defines from shm

Carlos Llamas
2024-06-05T22:52:29Z

On Wed, Jun 05, 2024 at 10:36:35PM +0000, Edward Liaw wrote:
> thuge-gen.c defines SHM_HUGE_* macros that are provided by the uapi
> since 4.14. These macros get redefined when compiling with Android's
> bionic because its sys/shm.h will import the uapi definitions.
>
> However if linux/shm.h is included, with glibc, sys/shm.h will clash on
> some struct definitions:
>
> /usr/include/linux/shm.h:26:8: error: redefinition of ‘struct shmid_ds’
> 26 | struct shmid_ds {
> | ^~~~~~~~
> In file included from /usr/include/x86_64-linux-gnu/bits/shm.h:45,
> from /usr/include/x86_64-linux-gnu/sys/shm.h:30:
> /usr/include/x86_64-linux-gnu/bits/types/struct_shmid_ds.h:24:8: note: originally defined here
> 24 | struct shmid_ds
> | ^~~~~~~~

I also hit this issue while using bionic. I have a thread reporting this
issue here: https://lore.kernel.org/all/Zl4LC9lTNptB2xTJ@google.com/

According to Andi Kleen, glibc and others should add these defines in
their headers. So it make sense to me that we would need indefs to
prevent a redefine macro issue.

>
> For now, guard the SHM_HUGE_* defines with ifndef to prevent
> redefinition warnings on Android bionic.
>
> Signed-off-by: Edward Liaw <edliaw@google.com>
> ---
> tools/testing/selftests/mm/thuge-gen.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/thuge-gen.c b/tools/testing/selftests/mm/thuge-gen.c
> index 034635317935..d50dc71cac32 100644
> --- a/tools/testing/selftests/mm/thuge-gen.c
> +++ b/tools/testing/selftests/mm/thuge-gen.c
> @@ -34,10 +34,18 @@
> #endif
>
> #define SHM_HUGETLB 04000 /* segment will use huge TLB pages */
> +#ifndef SHM_HUGE_SHIFT

nit: I see this file uses the form "#if !defined()" above for
MAP_HUGETLB. Perhaps it makes sense to use that and keep things
consistent? I'm fine either way.

Reviewed-by: Carlos Llamas <cmllamas@google.com>

> #define SHM_HUGE_SHIFT 26
> +#endif
> +#ifndef SHM_HUGE_MASK
> #define SHM_HUGE_MASK 0x3f
> +#endif
> +#ifndef SHM_HUGE_2MB
> #define SHM_HUGE_2MB (21 << SHM_HUGE_SHIFT)
> +#endif
> +#ifndef SHM_HUGE_1GB
> #define SHM_HUGE_1GB (30 << SHM_HUGE_SHIFT)
> +#endif
>
> #define NUM_PAGESIZES 5
> #define NUM_PAGES 4
> --
> 2.45.1.467.gbab1589fc0-goog
>