On Tue, May 28, 2019 at 6:14 PM Andrii Nakryiko <andriin@xxxxxx> wrote:
>
> Rewrite endianness check to use "more canonical" way, using
> compiler-defined macros, similar to few other places in libbpf. It also
> is more obvious and shorter.
>
> Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 37 ++++++++++++-------------------------
> 1 file changed, 12 insertions(+), 25 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 7b80b9ae8a1f..c98f9942fba4 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -607,31 +607,18 @@ static int bpf_object__elf_init(struct bpf_object *obj)
> return err;
> }
>
> -static int
> -bpf_object__check_endianness(struct bpf_object *obj)
> -{
> - static unsigned int const endian = 1;
> -
> - switch (obj->efile.ehdr.e_ident[EI_DATA]) {
> - case ELFDATA2LSB:
> - /* We are big endian, BPF obj is little endian. */
> - if (*(unsigned char const *)&endian != 1)
> - goto mismatch;
> - break;
> -
> - case ELFDATA2MSB:
> - /* We are little endian, BPF obj is big endian. */
> - if (*(unsigned char const *)&endian != 0)
> - goto mismatch;
> - break;
> - default:
> - return -LIBBPF_ERRNO__ENDIAN;
> - }
> -
> - return 0;
> -
> -mismatch:
> - pr_warning("Error: endianness mismatch.\n");
> +static int bpf_object__check_endianness(struct bpf_object *obj)
> +{
> +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
> + if (obj->efile.ehdr.e_ident[EI_DATA] == ELFDATA2LSB)
> + return 0;
> +#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
> + if (obj->efile.ehdr.e_ident[EI_DATA] == ELFDATA2MSB)
> + return 0;
> +#else
> +# error "Unrecognized __BYTE_ORDER__"
> +#endif
> + pr_warning("endianness mismatch.\n");
> return -LIBBPF_ERRNO__ENDIAN;
> }
>
> --
> 2.17.1
>
