We sometimes need to compare whole structures in an assert. It is
possible to use the existing macros on each field, but when the whole
structure has to be checked, it is more convenient to simply compare the
whole structure memory

Add a dedicated assert macro, ASSERT_MEMEQ, to allow bare memory
comparision
The output generated by this new macro looks like the following:
[...]
run_tests_skb_less:FAIL:returned flow keys unexpected memory mismatch
actual:
	00 00 00 00 00 00 00 00 	00 00 00 00 00 00 00 00
	00 00 00 00 00 00 00 00 	00 00 00 00 00 00 00 00
	00 00 00 00 00 00 00 00 	00 00 00 00 00 00 00 00
	00 00 00 00 00 00 00 00
expected:
	0E 00 3E 00 DD 86 01 01 	00 06 86 DD 50 00 90 1F
	00 00 00 00 00 00 00 00 	00 00 00 00 00 00 00 00
	00 00 00 00 00 00 00 00 	00 00 00 00 00 00 00 00
	01 00 00 00 00 00 00 00
[...]

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
---
Changes in v3:
- none

Changes in v2:
- replace DUMP_BUFFER with a real function
- make this function take a prefix
- add formatting example in the commit message
---
 tools/testing/selftests/bpf/test_progs.c | 15 +++++++++++++++
 tools/testing/selftests/bpf/test_progs.h | 15 +++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index 6088d8222d5905c3df6e6ebfb095c6bc5bf22399..c9e745d49493e594b55d79ac26061b0466f9a039 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -1282,6 +1282,21 @@ void crash_handler(int signum)
 	backtrace_symbols_fd(bt, sz, STDERR_FILENO);
 }
 
+void hexdump(const char *prefix, const void *buf, size_t len)
+{
+	for (int i = 0; i < len; i++) {
+		if (!(i % 16)) {
+			if (i)
+				fprintf(stdout, "\n");
+			fprintf(stdout, "%s", prefix);
+		}
+		if (i && !(i % 8) && (i % 16))
+			fprintf(stdout, "\t");
+		fprintf(stdout, "%02X ", ((uint8_t *)(buf))[i]);
+	}
+	fprintf(stdout, "\n");
+}
+
 static void sigint_handler(int signum)
 {
 	int i;
diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
index 74de33ae37e56c90646cd1e0bb58ed7e3f345ec0..404d0d4915d54fe15f6c33dbabdb58cccc3b2781 100644
--- a/tools/testing/selftests/bpf/test_progs.h
+++ b/tools/testing/selftests/bpf/test_progs.h
@@ -185,6 +185,7 @@ void test__end_subtest(void);
 void test__skip(void);
 void test__fail(void);
 int test__join_cgroup(const char *path);
+void hexdump(const char *prefix, const void *buf, size_t len);
 
 #define PRINT_FAIL(format...)                                                  \
 	({                                                                     \
@@ -344,6 +345,20 @@ int test__join_cgroup(const char *path);
 	___ok;								\
 })
 
+#define ASSERT_MEMEQ(actual, expected, len, name) ({			\
+	static int duration = 0;					\
+	const void *__act = actual;					\
+	const void *__exp = expected;					\
+	int __len = len;						\
+	bool ___ok = memcmp(__act, __exp, __len) == 0;			\
+	CHECK(!___ok, (name), "unexpected memory mismatch\n");		\
+	fprintf(stdout, "actual:\n");					\
+	hexdump("\t", __act, __len);					\
+	fprintf(stdout, "expected:\n");					\
+	hexdump("\t", __exp, __len);					\
+	___ok;								\
+})
+
 #define ASSERT_OK(res, name) ({						\
 	static int duration = 0;					\
 	long long ___res = (res);					\

-- 
2.47.0