selftests/bpf: Add byte swapping selftest

Add simple selftest validating byte swap built-ins and compile-time macros.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200630152125.3631920-3-andriin@fb.com

tools/testing/selftests/bpf/prog_tests/endian.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include <test_progs.h>
+#include "test_endian.skel.h"
+
+static int duration;
+
+#define IN16 0x1234
+#define IN32 0x12345678U
+#define IN64 0x123456789abcdef0ULL
+
+#define OUT16 0x3412
+#define OUT32 0x78563412U
+#define OUT64 0xf0debc9a78563412ULL
+
+void test_endian(void)
+{
+	struct test_endian* skel;
+	struct test_endian__bss *bss;
+	int err;
+
+	skel = test_endian__open_and_load();
+	if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
+		return;
+	bss = skel->bss;
+
+	bss->in16 = IN16;
+	bss->in32 = IN32;
+	bss->in64 = IN64;
+
+	err = test_endian__attach(skel);
+	if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
+		goto cleanup;
+
+	usleep(1);
+
+	CHECK(bss->out16 != OUT16, "out16", "got 0x%llx != exp 0x%llx\n",
+	      (__u64)bss->out16, (__u64)OUT16);
+	CHECK(bss->out32 != OUT32, "out32", "got 0x%llx != exp 0x%llx\n",
+	      (__u64)bss->out32, (__u64)OUT32);
+	CHECK(bss->out64 != OUT64, "out16", "got 0x%llx != exp 0x%llx\n",
+	      (__u64)bss->out64, (__u64)OUT64);
+
+	CHECK(bss->const16 != OUT16, "const16", "got 0x%llx != exp 0x%llx\n",
+	      (__u64)bss->const16, (__u64)OUT16);
+	CHECK(bss->const32 != OUT32, "const32", "got 0x%llx != exp 0x%llx\n",
+	      (__u64)bss->const32, (__u64)OUT32);
+	CHECK(bss->const64 != OUT64, "const64", "got 0x%llx != exp 0x%llx\n",
+	      (__u64)bss->const64, (__u64)OUT64);
+cleanup:
+	test_endian__destroy(skel);
+}

tools/testing/selftests/bpf/progs/test_endian.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+#define IN16 0x1234
+#define IN32 0x12345678U
+#define IN64 0x123456789abcdef0ULL
+
+__u16 in16 = 0;
+__u32 in32 = 0;
+__u64 in64 = 0;
+
+__u16 out16 = 0;
+__u32 out32 = 0;
+__u64 out64 = 0;
+
+__u16 const16 = 0;
+__u32 const32 = 0;
+__u64 const64 = 0;
+
+SEC("raw_tp/sys_enter")
+int sys_enter(const void *ctx)
+{
+	out16 = __builtin_bswap16(in16);
+	out32 = __builtin_bswap32(in32);
+	out64 = __builtin_bswap64(in64);
+	const16 = ___bpf_swab16(IN16);
+	const32 = ___bpf_swab32(IN32);
+	const64 = ___bpf_swab64(IN64);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";