libbpf: simplify endianness check

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.

Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 40690b7e500eea657aef1214775bb598fa3890a4..fb296eadc3f2871fd2966da7805ed521dccae640 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -607,31 +607,18 @@ errout:
        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;
 }