[PATCH bpf v4 2/2] selftests/bpf: Add a test for using a cpumap from an freplace-to-XDP program

[PATCH bpf v4 2/2] selftests/bpf: Add a test for using a cpumap from an freplace-to-XDP program

[Toke Høiland-Jørgensen]

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.

v4:
- Use skeletons for selftest
v3:
- Update comment to better explain the cause
- Add Yonghong's ACK

Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 .../selftests/bpf/prog_tests/fexit_bpf2bpf.c  | 54 +++++++++++++++++++
 .../selftests/bpf/progs/freplace_progmap.c    | 24 +++++++++
 2 files changed, 78 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/freplace_progmap.c

diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c b/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
index d1e32e792536..efa1fc65840d 100644
--- 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 +502,56 @@ static void test_fentry_to_cgroup_bpf(void)
 	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;
+	int err, tgt_fd;
+	__u32 key = 0;
+
+	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;
+
+	tgt_fd = bpf_program__fd(tgt_skel->progs.xdp_dummy_prog);
+
+	/* Change the 'redirect' program type to be a PROG_TYPE_EXT
+	 * with an XDP target
+	 */
+	bpf_program__set_type(skel->progs.xdp_cpumap_prog, BPF_PROG_TYPE_EXT);
+	bpf_program__set_expected_attach_type(skel->progs.xdp_cpumap_prog, 0);
+	err = bpf_program__set_attach_target(skel->progs.xdp_cpumap_prog,
+					     tgt_fd, "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 +577,6 @@ 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
index 000000000000..68174c3d7b37
--- /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);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(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("xdp")
+int xdp_cpumap_prog(struct xdp_md *ctx)
+{
+	return bpf_redirect_map(&cpu_map, 0, XDP_PASS);
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.38.1

Re: [PATCH bpf v4 2/2] selftests/bpf: Add a test for using a cpumap from an freplace-to-XDP program

[Andrii Nakryiko]

On Tue, Dec 13, 2022 at 5:05 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> 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.
>
> v4:
> - Use skeletons for selftest
> v3:
> - Update comment to better explain the cause
> - Add Yonghong's ACK
>
> Acked-by: Yonghong Song <yhs@fb.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---
>  .../selftests/bpf/prog_tests/fexit_bpf2bpf.c  | 54 +++++++++++++++++++
>  .../selftests/bpf/progs/freplace_progmap.c    | 24 +++++++++
>  2 files changed, 78 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/progs/freplace_progmap.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c b/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
> index d1e32e792536..efa1fc65840d 100644
> --- 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 +502,56 @@ static void test_fentry_to_cgroup_bpf(void)
>         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;
> +       int err, tgt_fd;
> +       __u32 key = 0;
> +
> +       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;
> +
> +       tgt_fd = bpf_program__fd(tgt_skel->progs.xdp_dummy_prog);
> +
> +       /* Change the 'redirect' program type to be a PROG_TYPE_EXT
> +        * with an XDP target
> +        */
> +       bpf_program__set_type(skel->progs.xdp_cpumap_prog, BPF_PROG_TYPE_EXT);
> +       bpf_program__set_expected_attach_type(skel->progs.xdp_cpumap_prog, 0);

you shouldn't need this manual override if you mark xdp_cpumap_prog as
SEC("freplace"), or am I missing something?

but other than this minor thing looks good to me, thanks

Acked-by: Andrii Nakryiko <andrii@kernel.org>



> +       err = bpf_program__set_attach_target(skel->progs.xdp_cpumap_prog,
> +                                            tgt_fd, "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 +577,6 @@ 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
> index 000000000000..68174c3d7b37
> --- /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);
> +       __uint(key_size, sizeof(__u32));
> +       __uint(value_size, sizeof(struct bpf_cpumap_val));

ok, another minor nit which you ignored, libbpf should be smart enough to accept

__type(key, __u32);
__type(value, struct bpf_cpumap_val);

And if it's not it would be good to know that it's not (and trivially fix it).

> +       __uint(max_entries, 1);
> +} cpu_map SEC(".maps");
> +
> +SEC("xdp/cpumap")
> +int xdp_drop_prog(struct xdp_md *ctx)
> +{
> +       return XDP_DROP;
> +}
> +
> +SEC("xdp")
> +int xdp_cpumap_prog(struct xdp_md *ctx)
> +{
> +       return bpf_redirect_map(&cpu_map, 0, XDP_PASS);
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.38.1
>

Re: [PATCH bpf v4 2/2] selftests/bpf: Add a test for using a cpumap from an freplace-to-XDP program

[Toke Høiland-Jørgensen]

Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:

> On Tue, Dec 13, 2022 at 5:05 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>>
>> 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.
>>
>> v4:
>> - Use skeletons for selftest
>> v3:
>> - Update comment to better explain the cause
>> - Add Yonghong's ACK
>>
>> Acked-by: Yonghong Song <yhs@fb.com>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
>> ---
>>  .../selftests/bpf/prog_tests/fexit_bpf2bpf.c  | 54 +++++++++++++++++++
>>  .../selftests/bpf/progs/freplace_progmap.c    | 24 +++++++++
>>  2 files changed, 78 insertions(+)
>>  create mode 100644 tools/testing/selftests/bpf/progs/freplace_progmap.c
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c b/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
>> index d1e32e792536..efa1fc65840d 100644
>> --- 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 +502,56 @@ static void test_fentry_to_cgroup_bpf(void)
>>         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;
>> +       int err, tgt_fd;
>> +       __u32 key = 0;
>> +
>> +       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;
>> +
>> +       tgt_fd = bpf_program__fd(tgt_skel->progs.xdp_dummy_prog);
>> +
>> +       /* Change the 'redirect' program type to be a PROG_TYPE_EXT
>> +        * with an XDP target
>> +        */
>> +       bpf_program__set_type(skel->progs.xdp_cpumap_prog, BPF_PROG_TYPE_EXT);
>> +       bpf_program__set_expected_attach_type(skel->progs.xdp_cpumap_prog, 0);
>
> you shouldn't need this manual override if you mark xdp_cpumap_prog as
> SEC("freplace"), or am I missing something?

No, you're right; I guess I was just too focused on recreating the flow
we use in libxdp. Will fix!

>> +       err = bpf_program__set_attach_target(skel->progs.xdp_cpumap_prog,
>> +                                            tgt_fd, "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 +577,6 @@ 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
>> index 000000000000..68174c3d7b37
>> --- /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);
>> +       __uint(key_size, sizeof(__u32));
>> +       __uint(value_size, sizeof(struct bpf_cpumap_val));
>
> ok, another minor nit which you ignored, libbpf should be smart enough to accept
>
> __type(key, __u32);
> __type(value, struct bpf_cpumap_val);
>
> And if it's not it would be good to know that it's not (and trivially
> fix it).

Ah, actually saw that comment on the previous version, and then
completely forgot about it when I was fixing things up. Sorry about
that; will change!

-Toke