[PATCH 3/4] selftests/bpf: Add test for dmabuf_iter

["T.J. Mercier" <tjmercier@google.com>]

This test creates a udmabuf and uses a BPF program that prints dmabuf
metadata with the new dmabuf_iter to verify it can be found.

Signed-off-by: T.J. Mercier <tjmercier@google.com>
---
 tools/testing/selftests/bpf/config            |   1 +
 .../selftests/bpf/prog_tests/dmabuf_iter.c    | 116 ++++++++++++++++++
 .../testing/selftests/bpf/progs/dmabuf_iter.c |  31 +++++
 3 files changed, 148 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c
 create mode 100644 tools/testing/selftests/bpf/progs/dmabuf_iter.c

diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index c378d5d07e02..a791c60813df 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -106,6 +106,7 @@ CONFIG_SECURITY=y
 CONFIG_SECURITYFS=y
 CONFIG_SYN_COOKIES=y
 CONFIG_TEST_BPF=m
+CONFIG_UDMABUF=y
 CONFIG_USERFAULTFD=y
 CONFIG_VSOCKETS=y
 CONFIG_VXLAN=y
diff --git a/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c b/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c
new file mode 100644
index 000000000000..af215a4e0520
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Google */
+
+#include <test_progs.h>
+#include <bpf/libbpf.h>
+#include <bpf/btf.h>
+#include "dmabuf_iter.skel.h"
+
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <linux/dma-buf.h>
+#include <linux/udmabuf.h>
+
+
+static void subtest_dmabuf_iter_check_udmabuf(struct dmabuf_iter *skel)
+{
+	static const char test_buffer_name[] = "udmabuf_test_buffer_for_iter";
+	const size_t test_buffer_size = 10 * getpagesize();
+
+	ASSERT_LE(sizeof(test_buffer_name), DMA_BUF_NAME_LEN, "NAMETOOLONG");
+
+	int memfd = memfd_create("memfd_test", MFD_ALLOW_SEALING);
+	ASSERT_OK_FD(memfd, "memfd_create");
+
+	ASSERT_OK(ftruncate(memfd, test_buffer_size), "ftruncate");
+
+	ASSERT_OK(fcntl(memfd, F_ADD_SEALS, F_SEAL_SHRINK), "seal");
+
+	int dev_udmabuf = open("/dev/udmabuf", O_RDONLY);
+	ASSERT_OK_FD(dev_udmabuf, "open udmabuf");
+
+	struct udmabuf_create create;
+	create.memfd = memfd;
+	create.flags = UDMABUF_FLAGS_CLOEXEC;
+	create.offset = 0;
+	create.size = test_buffer_size;
+
+	int udmabuf = ioctl(dev_udmabuf, UDMABUF_CREATE, &create);
+	close(dev_udmabuf);
+	ASSERT_OK_FD(udmabuf, "udmabuf_create");
+
+	ASSERT_OK(ioctl(udmabuf, DMA_BUF_SET_NAME_B, test_buffer_name), "name");
+
+	int iter_fd = bpf_iter_create(bpf_link__fd(skel->links.dmabuf_collector));
+	ASSERT_OK_FD(iter_fd, "iter_create");
+
+	FILE *iter_file = fdopen(iter_fd, "r");
+	ASSERT_OK_PTR(iter_file, "fdopen");
+
+	char *line = NULL;
+	size_t linesize = 0;
+	bool found_test_udmabuf = false;
+	while (getline(&line, &linesize, iter_file) != -1) {
+		long inode, size;
+		char name[DMA_BUF_NAME_LEN], exporter[32];
+
+		int nelements = sscanf(line, "ino:%ld size:%ld name:%s exp_name:%s",
+				       &inode, &size, name, exporter);
+
+		if (nelements == 4 && size == test_buffer_size &&
+				!strcmp(name, test_buffer_name) &&
+				!strcmp(exporter, "udmabuf")) {
+			found_test_udmabuf = true;
+			break;
+		}
+	}
+
+	ASSERT_TRUE(found_test_udmabuf, "found_test_buffer");
+
+	free(line);
+	fclose(iter_file);
+	close(iter_fd);
+	close(udmabuf);
+	close(memfd);
+}
+
+void test_dmabuf_iter(void)
+{
+	struct dmabuf_iter *skel = NULL;
+	char buf[256];
+	int iter_fd;
+
+	skel = dmabuf_iter__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "dmabuf_iter__open_and_load"))
+		return;
+
+	if (!ASSERT_OK(dmabuf_iter__attach(skel), "skel_attach"))
+		goto destroy;
+
+	iter_fd = bpf_iter_create(bpf_link__fd(skel->links.dmabuf_collector));
+	if (!ASSERT_GE(iter_fd, 0, "iter_create"))
+		goto destroy;
+
+	memset(buf, 0, sizeof(buf));
+	while (read(iter_fd, buf, sizeof(buf) > 0)) {
+		/* Read out all contents */
+	}
+
+	/* Next reads should return 0 */
+	ASSERT_EQ(read(iter_fd, buf, sizeof(buf)), 0, "read");
+
+	if (test__start_subtest("check_udmabuf"))
+		subtest_dmabuf_iter_check_udmabuf(skel);
+
+	close(iter_fd);
+
+destroy:
+	dmabuf_iter__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/dmabuf_iter.c b/tools/testing/selftests/bpf/progs/dmabuf_iter.c
new file mode 100644
index 000000000000..b2af14ceb609
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/dmabuf_iter.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Google LLC */
+#include <vmlinux.h>
+#include <bpf/bpf_core_read.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("iter/dmabuf")
+int dmabuf_collector(struct bpf_iter__dmabuf *ctx)
+{
+	struct seq_file *seq = ctx->meta->seq;
+	const struct dma_buf *dmabuf = ctx->dmabuf;
+
+	if (dmabuf) {
+		size_t size;
+		unsigned long inode;
+		const char *name, *exp_name;
+
+		if (bpf_core_read(&size, sizeof(size), &dmabuf->size) ||
+		    BPF_CORE_READ_INTO(&inode, dmabuf, file, f_inode, i_ino) ||
+		    bpf_core_read(&name, sizeof(name), &dmabuf->name) ||
+		    bpf_core_read(&exp_name, sizeof(exp_name), &dmabuf->exp_name))
+			return 1;
+
+		BPF_SEQ_PRINTF(seq, "ino:%lu size:%llu name:%s exp_name:%s\n",
+			inode, size, name ? name : "", exp_name ? exp_name : "");
+	}
+
+	return 0;
+}
-- 
2.49.0.604.gff1f9ca942-goog