selftests/bpf: Add a test for using a cpumap from an freplace-to-XDP program

This adds a simple test for inserting an XDP program into a cpumap that is
"owned" by an XDP program that was loaded as PROG_TYPE_EXT (as libxdp
does). Prior to the kernel fix this would fail because the map type
ownership would be set to PROG_TYPE_EXT instead of being resolved to
PROG_TYPE_XDP.

v5:
- Fix a few nits from Andrii, add his ACK
v4:
- Use skeletons for selftest
v3:
- Update comment to better explain the cause
- Add Yonghong's ACK

Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20221214230254.790066-2-toke@redhat.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c b/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
index d1e32e792536c0deb4481d231766a5ab43f39c73..20f5fa0fcec99f3b81a90d4f8d59cda838212121 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
+++ b/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
@@ -4,6 +4,8 @@
 #include <network_helpers.h>
 #include <bpf/btf.h>
 #include "bind4_prog.skel.h"
+#include "freplace_progmap.skel.h"
+#include "xdp_dummy.skel.h"
 
 typedef int (*test_cb)(struct bpf_object *obj);
 
@@ -500,6 +502,50 @@ cleanup:
        bind4_prog__destroy(skel);
 }
 
+static void test_func_replace_progmap(void)
+{
+       struct bpf_cpumap_val value = { .qsize = 1 };
+       struct freplace_progmap *skel = NULL;
+       struct xdp_dummy *tgt_skel = NULL;
+       __u32 key = 0;
+       int err;
+
+       skel = freplace_progmap__open();
+       if (!ASSERT_OK_PTR(skel, "prog_open"))
+               return;
+
+       tgt_skel = xdp_dummy__open_and_load();
+       if (!ASSERT_OK_PTR(tgt_skel, "tgt_prog_load"))
+               goto out;
+
+       err = bpf_program__set_attach_target(skel->progs.xdp_cpumap_prog,
+                                            bpf_program__fd(tgt_skel->progs.xdp_dummy_prog),
+                                            "xdp_dummy_prog");
+       if (!ASSERT_OK(err, "set_attach_target"))
+               goto out;
+
+       err = freplace_progmap__load(skel);
+       if (!ASSERT_OK(err, "obj_load"))
+               goto out;
+
+       /* Prior to fixing the kernel, loading the PROG_TYPE_EXT 'redirect'
+        * program above will cause the map owner type of 'cpumap' to be set to
+        * PROG_TYPE_EXT. This in turn will cause the bpf_map_update_elem()
+        * below to fail, because the program we are inserting into the map is
+        * of PROG_TYPE_XDP. After fixing the kernel, the initial ownership will
+        * be correctly resolved to the *target* of the PROG_TYPE_EXT program
+        * (i.e., PROG_TYPE_XDP) and the map update will succeed.
+        */
+       value.bpf_prog.fd = bpf_program__fd(skel->progs.xdp_drop_prog);
+       err = bpf_map_update_elem(bpf_map__fd(skel->maps.cpu_map),
+                                 &key, &value, 0);
+       ASSERT_OK(err, "map_update");
+
+out:
+       xdp_dummy__destroy(tgt_skel);
+       freplace_progmap__destroy(skel);
+}
+
 /* NOTE: affect other tests, must run in serial mode */
 void serial_test_fexit_bpf2bpf(void)
 {
@@ -525,4 +571,6 @@ void serial_test_fexit_bpf2bpf(void)
                test_func_replace_global_func();
        if (test__start_subtest("fentry_to_cgroup_bpf"))
                test_fentry_to_cgroup_bpf();
+       if (test__start_subtest("func_replace_progmap"))
+               test_func_replace_progmap();
 }

diff --git a/tools/testing/selftests/bpf/progs/freplace_progmap.c b/tools/testing/selftests/bpf/progs/freplace_progmap.c
new file mode 100644 (file)
index 0000000..81b56b9
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/freplace_progmap.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+struct {
+       __uint(type, BPF_MAP_TYPE_CPUMAP);
+       __type(key, __u32);
+       __type(value, struct bpf_cpumap_val);
+       __uint(max_entries, 1);
+} cpu_map SEC(".maps");
+
+SEC("xdp/cpumap")
+int xdp_drop_prog(struct xdp_md *ctx)
+{
+       return XDP_DROP;
+}
+
+SEC("freplace")
+int xdp_cpumap_prog(struct xdp_md *ctx)
+{
+       return bpf_redirect_map(&cpu_map, 0, XDP_PASS);
+}
+
+char _license[] SEC("license") = "GPL";