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SubjectRe: [RFC PATCH v4 2/9] tools headers: Add a macro to get HUGETLB page sizes for mmap
On Tue, Mar 02, 2021 at 08:57:44PM +0800, Yanan Wang wrote:
> We know that if a system supports multiple hugetlb page sizes,
> the desired hugetlb page size can be specified in bits [26:31]
> of the flag arguments. The value in these 6 bits will be the
> shift of each hugetlb page size.
>
> So add a macro to get the page size shift and then calculate the
> corresponding hugetlb page size, using flag x.
>
> Cc: Ben Gardon <bgardon@google.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Jiri Olsa <jolsa@redhat.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Michael Kerrisk <mtk.manpages@gmail.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Suggested-by: Ben Gardon <bgardon@google.com>
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> Reviewed-by: Ben Gardon <bgardon@google.com>
> ---
> include/uapi/linux/mman.h | 2 ++
> tools/include/uapi/linux/mman.h | 2 ++
> 2 files changed, 4 insertions(+)
>
> diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h
> index f55bc680b5b0..8bd41128a0ee 100644
> --- a/include/uapi/linux/mman.h
> +++ b/include/uapi/linux/mman.h
> @@ -41,4 +41,6 @@
> #define MAP_HUGE_2GB HUGETLB_FLAG_ENCODE_2GB
> #define MAP_HUGE_16GB HUGETLB_FLAG_ENCODE_16GB
>
> +#define MAP_HUGE_PAGE_SIZE(x) (1 << ((x >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK))

Needs to be '1ULL' to avoid shift overflow when given MAP_HUGE_16GB.

Thanks,
drew

> +
> #endif /* _UAPI_LINUX_MMAN_H */
> diff --git a/tools/include/uapi/linux/mman.h b/tools/include/uapi/linux/mman.h
> index f55bc680b5b0..8bd41128a0ee 100644
> --- a/tools/include/uapi/linux/mman.h
> +++ b/tools/include/uapi/linux/mman.h
> @@ -41,4 +41,6 @@
> #define MAP_HUGE_2GB HUGETLB_FLAG_ENCODE_2GB
> #define MAP_HUGE_16GB HUGETLB_FLAG_ENCODE_16GB
>
> +#define MAP_HUGE_PAGE_SIZE(x) (1 << ((x >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK))
> +
> #endif /* _UAPI_LINUX_MMAN_H */
> --
> 2.23.0
>

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