Not all compilers have __builtin_bswap16() and __builtin_bswap32(),
thus not all compilers are able to compile the following code:
(__builtin_constant_p(x) ? \
___constant_swab16(x) : __builtin_bswap16(x))
That's the reason why bpf_ntohl() doesn't work on GCC < 4.8, for
instance:
error: implicit declaration of function '__builtin_bswap16'
We can use __builtin_bswap16() only if compiler has this built-in,
that is, only if __HAVE_BUILTIN_BSWAP16__ is defined. Standard UAPI
__swab16()/__swab32() take care of that, and, additionally, handle
__builtin_constant_p() cases as well:
#ifdef __HAVE_BUILTIN_BSWAP16__
#define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
#else
#define __swab16(x) \
(__builtin_constant_p((__u16)(x)) ? \
___constant_swab16(x) : \
__fswab16(x))
#endif
So we can tweak selftests/bpf/bpf_endian.h and use UAPI
__swab16()/__swab32().
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
v2: fixed build error, reshuffled patches (Stanislav Fomichev)
tools/testing/selftests/bpf/bpf_endian.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/bpf/bpf_endian.h b/tools/testing/selftests/bpf/bpf_endian.h
index b25595ea4a78..1ed268b2002b 100644
--- a/tools/testing/selftests/bpf/bpf_endian.h
+++ b/tools/testing/selftests/bpf/bpf_endian.h
@@ -20,12 +20,12 @@
* use different targets.
*/
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-# define __bpf_ntohs(x) __builtin_bswap16(x)
-# define __bpf_htons(x) __builtin_bswap16(x)
+# define __bpf_ntohs(x) __swab16(x)
+# define __bpf_htons(x) __swab16(x)
# define __bpf_constant_ntohs(x) ___constant_swab16(x)
# define __bpf_constant_htons(x) ___constant_swab16(x)
-# define __bpf_ntohl(x) __builtin_bswap32(x)
-# define __bpf_htonl(x) __builtin_bswap32(x)
+# define __bpf_ntohl(x) __swab32(x)
+# define __bpf_htonl(x) __swab32(x)
# define __bpf_constant_ntohl(x) ___constant_swab32(x)
# define __bpf_constant_htonl(x) ___constant_swab32(x)
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
--
2.21.0
