selftests: xsk: Add test UNALIGNED_INV_DESC_4K1_FRAME_SIZE

Add unaligned descriptor test for frame size of 4001. Using an odd frame
size ensures that the end of the UMEM is not near a page boundary. This
allows testing descriptors that staddle the end of the UMEM but not a
page.

This test used to fail without the previous commit ("xsk: Fix unaligned
descriptor validation").

Signed-off-by: Kal Conley <kal.conley@dectris.com>
Link: https://lore.kernel.org/r/20230405235920.7305-3-kal.conley@dectris.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

tools/testing/selftests/bpf/xskxceiver.c

@@ -69,6 +69,7 @@
  */
 
 #define _GNU_SOURCE
+#include <assert.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <getopt.h>
@@ -1876,6 +1877,29 @@ static void run_pkt_test(struct test_spec *test, enum test_mode mode, enum test_
 		test->ifobj_rx->umem->unaligned_mode = true;
 		testapp_invalid_desc(test);
 		break;
+	case TEST_TYPE_UNALIGNED_INV_DESC_4K1_FRAME: {
+		u64 page_size, umem_size;
+
+		if (!hugepages_present(test->ifobj_tx)) {
+			ksft_test_result_skip("No 2M huge pages present.\n");
+			return;
+		}
+		test_spec_set_name(test, "UNALIGNED_INV_DESC_4K1_FRAME_SIZE");
+		/* Odd frame size so the UMEM doesn't end near a page boundary. */
+		test->ifobj_tx->umem->frame_size = 4001;
+		test->ifobj_rx->umem->frame_size = 4001;
+		test->ifobj_tx->umem->unaligned_mode = true;
+		test->ifobj_rx->umem->unaligned_mode = true;
+		/* This test exists to test descriptors that staddle the end of
+		 * the UMEM but not a page.
+		 */
+		page_size = sysconf(_SC_PAGESIZE);
+		umem_size = test->ifobj_tx->umem->num_frames * test->ifobj_tx->umem->frame_size;
+		assert(umem_size % page_size > PKT_SIZE);
+		assert(umem_size % page_size < page_size - PKT_SIZE);
+		testapp_invalid_desc(test);
+		break;
+	}
 	case TEST_TYPE_UNALIGNED:
 		if (!testapp_unaligned(test))
 			return;

tools/testing/selftests/bpf/xskxceiver.h

@@ -78,6 +78,7 @@ enum test_type {
 	TEST_TYPE_ALIGNED_INV_DESC,
 	TEST_TYPE_ALIGNED_INV_DESC_2K_FRAME,
 	TEST_TYPE_UNALIGNED_INV_DESC,
+	TEST_TYPE_UNALIGNED_INV_DESC_4K1_FRAME,
 	TEST_TYPE_HEADROOM,
 	TEST_TYPE_TEARDOWN,
 	TEST_TYPE_BIDI,