diff mbox series

[bpf-next,2/2] selftests/bpf: Excercise bpf_obj_get_info_by_fd for bpf2bpf

Message ID 20220730000809.312891-2-sdf@google.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series [bpf-next,1/2] bpf: use proper target btf when exporting attach_btf_obj_id | expand

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bpf/vmtest-bpf-next-PR success PR summary
bpf/vmtest-bpf-next-VM_Test-1 success Logs for Kernel LATEST on ubuntu-latest with gcc
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Commit Message

Stanislav Fomichev July 30, 2022, 12:08 a.m. UTC
Apparently, no existing selftest covers it. Add a new one where
we load cgroup/bind4 program and attach fentry to it.
Calling bpf_obj_get_info_by_fd on the fentry program
should return non-zero btf_id/btf_obj_id instead of crashing the kernel.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
 .../selftests/bpf/prog_tests/attach_to_bpf.c  | 109 ++++++++++++++++++
 .../selftests/bpf/progs/attach_to_bpf.c       |  12 ++
 2 files changed, 121 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
 create mode 100644 tools/testing/selftests/bpf/progs/attach_to_bpf.c

Comments

Hao Luo July 30, 2022, 12:56 a.m. UTC | #1
On Fri, Jul 29, 2022 at 5:08 PM Stanislav Fomichev <sdf@google.com> wrote:
>
> Apparently, no existing selftest covers it. Add a new one where
> we load cgroup/bind4 program and attach fentry to it.
> Calling bpf_obj_get_info_by_fd on the fentry program
> should return non-zero btf_id/btf_obj_id instead of crashing the kernel.
>
> Signed-off-by: Stanislav Fomichev <sdf@google.com>
> ---

Looks good to me overall, with a few nits.

>  .../selftests/bpf/prog_tests/attach_to_bpf.c  | 109 ++++++++++++++++++
>  .../selftests/bpf/progs/attach_to_bpf.c       |  12 ++
>  2 files changed, 121 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
>  create mode 100644 tools/testing/selftests/bpf/progs/attach_to_bpf.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> new file mode 100644
> index 000000000000..fcf726c5ff0f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> @@ -0,0 +1,109 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <stdlib.h>
> +#include <bpf/btf.h>
> +#include <test_progs.h>
> +#include <network_helpers.h>
> +#include "attach_to_bpf.skel.h"
> +
> +char bpf_log_buf[BPF_LOG_BUF_SIZE];
> +
> +static int find_prog_btf_id(const char *name, __u32 attach_prog_fd)
> +{
> +       struct bpf_prog_info info = {};
> +       __u32 info_len = sizeof(info);
> +       struct btf *btf;
> +       int err;
> +
> +       err = bpf_obj_get_info_by_fd(attach_prog_fd, &info, &info_len);
> +       if (err)
> +               return err;
> +
> +       if (!info.btf_id)
> +               return -EINVAL;
> +
> +       btf = btf__load_from_kernel_by_id(info.btf_id);
> +       err = libbpf_get_error(btf);
> +       if (err)
> +               return err;
> +
> +       err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);

nit: Prefer use a separate variable like 'btf_id' instead of using 'err'.

> +       btf__free(btf);
> +       if (err <= 0)
> +               return err;
> +
> +       return err;
> +}
> +
> +int load_fentry(int attach_prog_fd, int attach_btf_id)
> +{
> +       LIBBPF_OPTS(bpf_prog_load_opts, opts,
> +                   .expected_attach_type = BPF_TRACE_FENTRY,
> +                   .attach_prog_fd = attach_prog_fd,
> +                   .attach_btf_id = attach_btf_id,
> +                   .log_buf = bpf_log_buf,
> +                   .log_size = sizeof(bpf_log_buf),
> +       );
> +       struct bpf_insn insns[] = {
> +               BPF_MOV64_IMM(BPF_REG_0, 0),
> +               BPF_EXIT_INSN(),
> +       };
> +       int ret;
> +
> +       ret = bpf_prog_load(BPF_PROG_TYPE_TRACING,
> +                           "bind4_fentry",
> +                           "GPL",
> +                           insns,
> +                           ARRAY_SIZE(insns),
> +                           &opts);
> +       if (ret)
> +               printf("verifier log: %s\n", bpf_log_buf);

Do we need to print log? If print logging isn't necessary, we could
directly return bpf_prog_load(). Seems simpler.

> +       return ret;
> +}
> +
> +void test_attach_to_bpf(void)
> +{
> +       struct attach_to_bpf *skel = NULL;
> +       struct bpf_prog_info info = {};
> +       __u32 info_len = sizeof(info);
> +       int cgroup_fd = -1;
> +       int fentry_fd = -1;
> +       int btf_id;
> +
> +       cgroup_fd = test__join_cgroup("/attach_to_bpf");
> +       if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))
> +               return;
> +
> +       skel = attach_to_bpf__open_and_load();
> +       if (!ASSERT_OK_PTR(skel, "skel"))
> +               goto cleanup;
> +
> +       skel->links.bind4 = bpf_program__attach_cgroup(skel->progs.bind4, cgroup_fd);
> +       if (!ASSERT_OK_PTR(skel, "bpf_program__attach_cgroup"))
> +               goto cleanup;
> +
> +       btf_id = find_prog_btf_id("bind4", bpf_program__fd(skel->progs.bind4));
> +       if (!ASSERT_GE(btf_id, 0, "find_prog_btf_id"))
> +               goto cleanup;
> +
> +       fentry_fd = load_fentry(bpf_program__fd(skel->progs.bind4), btf_id);
> +       if (!ASSERT_GE(fentry_fd, 0, "load_fentry"))
> +               goto cleanup;
> +
> +       /* Make sure bpf_obj_get_info_by_fd works correctly when attaching
> +        * to another BPF program.
> +        */
> +
> +       if (!ASSERT_OK(bpf_obj_get_info_by_fd(fentry_fd, &info, &info_len),
> +                      "bpf_obj_get_info_by_fd"))
> +               goto cleanup;
> +

Conditional checking may not be necessary. Just
ASSERT_OK(bpf_obj_get_info_by_fd(...)). Looks more compact.

> +       ASSERT_EQ(info.btf_id, 0, "info.btf_id");
> +       ASSERT_GT(info.attach_btf_id, 0, "info.attach_btf_id");
> +       ASSERT_GT(info.attach_btf_obj_id, 0, "info.attach_btf_obj_id");
> +
> +cleanup:
> +       close(cgroup_fd);
> +       close(fentry_fd);
> +       attach_to_bpf__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/attach_to_bpf.c b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
> new file mode 100644
> index 000000000000..3f111fe96f8f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
> @@ -0,0 +1,12 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +SEC("cgroup/bind4")
> +int bind4(struct bpf_sock_addr *ctx)
> +{
> +       return 1;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.37.1.455.g008518b4e5-goog
>
Stanislav Fomichev July 30, 2022, 2:16 a.m. UTC | #2
On Fri, Jul 29, 2022 at 5:56 PM Hao Luo <haoluo@google.com> wrote:
>
> On Fri, Jul 29, 2022 at 5:08 PM Stanislav Fomichev <sdf@google.com> wrote:
> >
> > Apparently, no existing selftest covers it. Add a new one where
> > we load cgroup/bind4 program and attach fentry to it.
> > Calling bpf_obj_get_info_by_fd on the fentry program
> > should return non-zero btf_id/btf_obj_id instead of crashing the kernel.
> >
> > Signed-off-by: Stanislav Fomichev <sdf@google.com>
> > ---
>
> Looks good to me overall, with a few nits.

Thank you for the review! Will respin on Mon.

> >  .../selftests/bpf/prog_tests/attach_to_bpf.c  | 109 ++++++++++++++++++
> >  .../selftests/bpf/progs/attach_to_bpf.c       |  12 ++
> >  2 files changed, 121 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/attach_to_bpf.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> > new file mode 100644
> > index 000000000000..fcf726c5ff0f
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> > @@ -0,0 +1,109 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#define _GNU_SOURCE
> > +#include <stdlib.h>
> > +#include <bpf/btf.h>
> > +#include <test_progs.h>
> > +#include <network_helpers.h>
> > +#include "attach_to_bpf.skel.h"
> > +
> > +char bpf_log_buf[BPF_LOG_BUF_SIZE];
> > +
> > +static int find_prog_btf_id(const char *name, __u32 attach_prog_fd)
> > +{
> > +       struct bpf_prog_info info = {};
> > +       __u32 info_len = sizeof(info);
> > +       struct btf *btf;
> > +       int err;
> > +
> > +       err = bpf_obj_get_info_by_fd(attach_prog_fd, &info, &info_len);
> > +       if (err)
> > +               return err;
> > +
> > +       if (!info.btf_id)
> > +               return -EINVAL;
> > +
> > +       btf = btf__load_from_kernel_by_id(info.btf_id);
> > +       err = libbpf_get_error(btf);
> > +       if (err)
> > +               return err;
> > +
> > +       err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
>
> nit: Prefer use a separate variable like 'btf_id' instead of using 'err'.

SG!

> > +       btf__free(btf);
> > +       if (err <= 0)
> > +               return err;
> > +
> > +       return err;
> > +}
> > +
> > +int load_fentry(int attach_prog_fd, int attach_btf_id)
> > +{
> > +       LIBBPF_OPTS(bpf_prog_load_opts, opts,
> > +                   .expected_attach_type = BPF_TRACE_FENTRY,
> > +                   .attach_prog_fd = attach_prog_fd,
> > +                   .attach_btf_id = attach_btf_id,
> > +                   .log_buf = bpf_log_buf,
> > +                   .log_size = sizeof(bpf_log_buf),
> > +       );
> > +       struct bpf_insn insns[] = {
> > +               BPF_MOV64_IMM(BPF_REG_0, 0),
> > +               BPF_EXIT_INSN(),
> > +       };
> > +       int ret;
> > +
> > +       ret = bpf_prog_load(BPF_PROG_TYPE_TRACING,
> > +                           "bind4_fentry",
> > +                           "GPL",
> > +                           insns,
> > +                           ARRAY_SIZE(insns),
> > +                           &opts);
> > +       if (ret)
> > +               printf("verifier log: %s\n", bpf_log_buf);
>
> Do we need to print log? If print logging isn't necessary, we could
> directly return bpf_prog_load(). Seems simpler.

We don't really need it. I've been using it during development, but I
guess it should be fine to drop since the test is passing now :-)

> > +       return ret;
> > +}
> > +
> > +void test_attach_to_bpf(void)
> > +{
> > +       struct attach_to_bpf *skel = NULL;
> > +       struct bpf_prog_info info = {};
> > +       __u32 info_len = sizeof(info);
> > +       int cgroup_fd = -1;
> > +       int fentry_fd = -1;
> > +       int btf_id;
> > +
> > +       cgroup_fd = test__join_cgroup("/attach_to_bpf");
> > +       if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))
> > +               return;
> > +
> > +       skel = attach_to_bpf__open_and_load();
> > +       if (!ASSERT_OK_PTR(skel, "skel"))
> > +               goto cleanup;
> > +
> > +       skel->links.bind4 = bpf_program__attach_cgroup(skel->progs.bind4, cgroup_fd);
> > +       if (!ASSERT_OK_PTR(skel, "bpf_program__attach_cgroup"))
> > +               goto cleanup;
> > +
> > +       btf_id = find_prog_btf_id("bind4", bpf_program__fd(skel->progs.bind4));
> > +       if (!ASSERT_GE(btf_id, 0, "find_prog_btf_id"))
> > +               goto cleanup;
> > +
> > +       fentry_fd = load_fentry(bpf_program__fd(skel->progs.bind4), btf_id);
> > +       if (!ASSERT_GE(fentry_fd, 0, "load_fentry"))
> > +               goto cleanup;
> > +
> > +       /* Make sure bpf_obj_get_info_by_fd works correctly when attaching
> > +        * to another BPF program.
> > +        */
> > +
> > +       if (!ASSERT_OK(bpf_obj_get_info_by_fd(fentry_fd, &info, &info_len),
> > +                      "bpf_obj_get_info_by_fd"))
> > +               goto cleanup;
> > +
>
> Conditional checking may not be necessary. Just
> ASSERT_OK(bpf_obj_get_info_by_fd(...)). Looks more compact.

Ack, makes sense.

> > +       ASSERT_EQ(info.btf_id, 0, "info.btf_id");
> > +       ASSERT_GT(info.attach_btf_id, 0, "info.attach_btf_id");
> > +       ASSERT_GT(info.attach_btf_obj_id, 0, "info.attach_btf_obj_id");
> > +
> > +cleanup:
> > +       close(cgroup_fd);
> > +       close(fentry_fd);
> > +       attach_to_bpf__destroy(skel);
> > +}
> > diff --git a/tools/testing/selftests/bpf/progs/attach_to_bpf.c b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
> > new file mode 100644
> > index 000000000000..3f111fe96f8f
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
> > @@ -0,0 +1,12 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <linux/bpf.h>
> > +#include <bpf/bpf_helpers.h>
> > +
> > +SEC("cgroup/bind4")
> > +int bind4(struct bpf_sock_addr *ctx)
> > +{
> > +       return 1;
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
> > --
> > 2.37.1.455.g008518b4e5-goog
> >
Martin KaFai Lau Aug. 1, 2022, 5:45 p.m. UTC | #3
On Fri, Jul 29, 2022 at 05:08:09PM -0700, Stanislav Fomichev wrote:
> Apparently, no existing selftest covers it. Add a new one where
> we load cgroup/bind4 program and attach fentry to it.
> Calling bpf_obj_get_info_by_fd on the fentry program
> should return non-zero btf_id/btf_obj_id instead of crashing the kernel.
> 
> Signed-off-by: Stanislav Fomichev <sdf@google.com>
> ---
>  .../selftests/bpf/prog_tests/attach_to_bpf.c  | 109 ++++++++++++++++++
>  .../selftests/bpf/progs/attach_to_bpf.c       |  12 ++
>  2 files changed, 121 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
>  create mode 100644 tools/testing/selftests/bpf/progs/attach_to_bpf.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> new file mode 100644
> index 000000000000..fcf726c5ff0f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> @@ -0,0 +1,109 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <stdlib.h>
> +#include <bpf/btf.h>
> +#include <test_progs.h>
> +#include <network_helpers.h>
> +#include "attach_to_bpf.skel.h"
> +
> +char bpf_log_buf[BPF_LOG_BUF_SIZE];
static

> +
> +static int find_prog_btf_id(const char *name, __u32 attach_prog_fd)
> +{
> +	struct bpf_prog_info info = {};
> +	__u32 info_len = sizeof(info);
> +	struct btf *btf;
> +	int err;
> +
> +	err = bpf_obj_get_info_by_fd(attach_prog_fd, &info, &info_len);
> +	if (err)
> +		return err;
> +
> +	if (!info.btf_id)
> +		return -EINVAL;
> +
> +	btf = btf__load_from_kernel_by_id(info.btf_id);
> +	err = libbpf_get_error(btf);
> +	if (err)
> +		return err;
> +
> +	err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
> +	btf__free(btf);
> +	if (err <= 0)
> +		return err;
> +
> +	return err;
> +}
> +
> +int load_fentry(int attach_prog_fd, int attach_btf_id)
static

> +{
> +	LIBBPF_OPTS(bpf_prog_load_opts, opts,
> +		    .expected_attach_type = BPF_TRACE_FENTRY,
> +		    .attach_prog_fd = attach_prog_fd,
> +		    .attach_btf_id = attach_btf_id,
> +		    .log_buf = bpf_log_buf,
> +		    .log_size = sizeof(bpf_log_buf),
> +	);
> +	struct bpf_insn insns[] = {
> +		BPF_MOV64_IMM(BPF_REG_0, 0),
> +		BPF_EXIT_INSN(),
> +	};
> +	int ret;
> +
> +	ret = bpf_prog_load(BPF_PROG_TYPE_TRACING,
> +			    "bind4_fentry",
> +			    "GPL",
> +			    insns,
> +			    ARRAY_SIZE(insns),
> +			    &opts);
> +	if (ret)
> +		printf("verifier log: %s\n", bpf_log_buf);
If this fentry prog is in the attach_to_bpf.c and load by skel, this printf
and the bpf_log_buf can go away.  I wonder if it can use the '?' like
SEC("?cgroup/bind4") and SEC("?fentry").  Then opens attach_to_bpf.skel.h
twice and use bpf_program__set_autoload() to load individual program.

Another option could be to reuse the progs/bind4_prog.c and directly
put the fentry program in the attach_to_bpf.c.

btw, this test feels like something that could be a few line
addition to the test_fexit_bpf2bpf_common() in fexit_bpf2bpf.c.
Adding one to test fentry into a cgroup bpf prog is also good.
No strong opinion here also.

> +	return ret;
> +}
> +
> +void test_attach_to_bpf(void)
> +{
> +	struct attach_to_bpf *skel = NULL;
> +	struct bpf_prog_info info = {};
> +	__u32 info_len = sizeof(info);
> +	int cgroup_fd = -1;
> +	int fentry_fd = -1;
> +	int btf_id;
> +
> +	cgroup_fd = test__join_cgroup("/attach_to_bpf");
> +	if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))
> +		return;
> +
> +	skel = attach_to_bpf__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "skel"))
> +		goto cleanup;
> +
> +	skel->links.bind4 = bpf_program__attach_cgroup(skel->progs.bind4, cgroup_fd);
> +	if (!ASSERT_OK_PTR(skel, "bpf_program__attach_cgroup"))
> +		goto cleanup;
> +
> +	btf_id = find_prog_btf_id("bind4", bpf_program__fd(skel->progs.bind4));
> +	if (!ASSERT_GE(btf_id, 0, "find_prog_btf_id"))
> +		goto cleanup;
> +
> +	fentry_fd = load_fentry(bpf_program__fd(skel->progs.bind4), btf_id);
> +	if (!ASSERT_GE(fentry_fd, 0, "load_fentry"))
> +		goto cleanup;
> +
> +	/* Make sure bpf_obj_get_info_by_fd works correctly when attaching
> +	 * to another BPF program.
> +	 */
> +
> +	if (!ASSERT_OK(bpf_obj_get_info_by_fd(fentry_fd, &info, &info_len),
> +		       "bpf_obj_get_info_by_fd"))
> +		goto cleanup;
> +
> +	ASSERT_EQ(info.btf_id, 0, "info.btf_id");
> +	ASSERT_GT(info.attach_btf_id, 0, "info.attach_btf_id");
> +	ASSERT_GT(info.attach_btf_obj_id, 0, "info.attach_btf_obj_id");
> +
> +cleanup:
> +	close(cgroup_fd);
> +	close(fentry_fd);
> +	attach_to_bpf__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/attach_to_bpf.c b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
> new file mode 100644
> index 000000000000..3f111fe96f8f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
nit. attach_to_bpf.c sounds too broad.
May be fentry_to_cgroup_bpf.c ?

> @@ -0,0 +1,12 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +SEC("cgroup/bind4")
> +int bind4(struct bpf_sock_addr *ctx)
> +{
> +	return 1;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> -- 
> 2.37.1.455.g008518b4e5-goog
>
Stanislav Fomichev Aug. 1, 2022, 6:23 p.m. UTC | #4
On Mon, Aug 1, 2022 at 10:45 AM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Fri, Jul 29, 2022 at 05:08:09PM -0700, Stanislav Fomichev wrote:
> > Apparently, no existing selftest covers it. Add a new one where
> > we load cgroup/bind4 program and attach fentry to it.
> > Calling bpf_obj_get_info_by_fd on the fentry program
> > should return non-zero btf_id/btf_obj_id instead of crashing the kernel.
> >
> > Signed-off-by: Stanislav Fomichev <sdf@google.com>
> > ---
> >  .../selftests/bpf/prog_tests/attach_to_bpf.c  | 109 ++++++++++++++++++
> >  .../selftests/bpf/progs/attach_to_bpf.c       |  12 ++
> >  2 files changed, 121 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/attach_to_bpf.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> > new file mode 100644
> > index 000000000000..fcf726c5ff0f
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> > @@ -0,0 +1,109 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#define _GNU_SOURCE
> > +#include <stdlib.h>
> > +#include <bpf/btf.h>
> > +#include <test_progs.h>
> > +#include <network_helpers.h>
> > +#include "attach_to_bpf.skel.h"
> > +
> > +char bpf_log_buf[BPF_LOG_BUF_SIZE];
> static

Will remove bpf_log_buf. Sent v2 too soon :-(

> > +
> > +static int find_prog_btf_id(const char *name, __u32 attach_prog_fd)
> > +{
> > +     struct bpf_prog_info info = {};
> > +     __u32 info_len = sizeof(info);
> > +     struct btf *btf;
> > +     int err;
> > +
> > +     err = bpf_obj_get_info_by_fd(attach_prog_fd, &info, &info_len);
> > +     if (err)
> > +             return err;
> > +
> > +     if (!info.btf_id)
> > +             return -EINVAL;
> > +
> > +     btf = btf__load_from_kernel_by_id(info.btf_id);
> > +     err = libbpf_get_error(btf);
> > +     if (err)
> > +             return err;
> > +
> > +     err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
> > +     btf__free(btf);
> > +     if (err <= 0)
> > +             return err;
> > +
> > +     return err;
> > +}
> > +
> > +int load_fentry(int attach_prog_fd, int attach_btf_id)
> static

Thx!

> > +{
> > +     LIBBPF_OPTS(bpf_prog_load_opts, opts,
> > +                 .expected_attach_type = BPF_TRACE_FENTRY,
> > +                 .attach_prog_fd = attach_prog_fd,
> > +                 .attach_btf_id = attach_btf_id,
> > +                 .log_buf = bpf_log_buf,
> > +                 .log_size = sizeof(bpf_log_buf),
> > +     );
> > +     struct bpf_insn insns[] = {
> > +             BPF_MOV64_IMM(BPF_REG_0, 0),
> > +             BPF_EXIT_INSN(),
> > +     };
> > +     int ret;
> > +
> > +     ret = bpf_prog_load(BPF_PROG_TYPE_TRACING,
> > +                         "bind4_fentry",
> > +                         "GPL",
> > +                         insns,
> > +                         ARRAY_SIZE(insns),
> > +                         &opts);
> > +     if (ret)
> > +             printf("verifier log: %s\n", bpf_log_buf);
> If this fentry prog is in the attach_to_bpf.c and load by skel, this printf
> and the bpf_log_buf can go away.  I wonder if it can use the '?' like
> SEC("?cgroup/bind4") and SEC("?fentry").  Then opens attach_to_bpf.skel.h
> twice and use bpf_program__set_autoload() to load individual program .

Good ideal, let me try to see if doing "?fentry" is easier..
(unless we agree to keep load_fentry, see below)

> Another option could be to reuse the progs/bind4_prog.c and directly
> put the fentry program in the attach_to_bpf.c.
>
> btw, this test feels like something that could be a few line
> addition to the test_fexit_bpf2bpf_common() in fexit_bpf2bpf.c.
> Adding one to test fentry into a cgroup bpf prog is also good.
> No strong opinion here also.

I was trying to reuse fexit_bpf2bpf initially but I sank too much time
into it and decided that it might be easier to write a
simpler/separate reproducer instead :-(
How about we reuse progs/bind4_prog.c and keep load_fentry() ? And put
this new test in fexit_bpf2bpf.c ?
Martin KaFai Lau Aug. 1, 2022, 7:55 p.m. UTC | #5
On Mon, Aug 01, 2022 at 11:23:56AM -0700, Stanislav Fomichev wrote:
> On Mon, Aug 1, 2022 at 10:45 AM Martin KaFai Lau <kafai@fb.com> wrote:
> >
> > On Fri, Jul 29, 2022 at 05:08:09PM -0700, Stanislav Fomichev wrote:
> > > Apparently, no existing selftest covers it. Add a new one where
> > > we load cgroup/bind4 program and attach fentry to it.
> > > Calling bpf_obj_get_info_by_fd on the fentry program
> > > should return non-zero btf_id/btf_obj_id instead of crashing the kernel.
> > >
> > > Signed-off-by: Stanislav Fomichev <sdf@google.com>
> > > ---
> > >  .../selftests/bpf/prog_tests/attach_to_bpf.c  | 109 ++++++++++++++++++
> > >  .../selftests/bpf/progs/attach_to_bpf.c       |  12 ++
> > >  2 files changed, 121 insertions(+)
> > >  create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> > >  create mode 100644 tools/testing/selftests/bpf/progs/attach_to_bpf.c
> > >
> > > diff --git a/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> > > new file mode 100644
> > > index 000000000000..fcf726c5ff0f
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
> > > @@ -0,0 +1,109 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +#define _GNU_SOURCE
> > > +#include <stdlib.h>
> > > +#include <bpf/btf.h>
> > > +#include <test_progs.h>
> > > +#include <network_helpers.h>
> > > +#include "attach_to_bpf.skel.h"
> > > +
> > > +char bpf_log_buf[BPF_LOG_BUF_SIZE];
> > static
> 
> Will remove bpf_log_buf. Sent v2 too soon :-(
> 
> > > +
> > > +static int find_prog_btf_id(const char *name, __u32 attach_prog_fd)
> > > +{
> > > +     struct bpf_prog_info info = {};
> > > +     __u32 info_len = sizeof(info);
> > > +     struct btf *btf;
> > > +     int err;
> > > +
> > > +     err = bpf_obj_get_info_by_fd(attach_prog_fd, &info, &info_len);
> > > +     if (err)
> > > +             return err;
> > > +
> > > +     if (!info.btf_id)
> > > +             return -EINVAL;
> > > +
> > > +     btf = btf__load_from_kernel_by_id(info.btf_id);
> > > +     err = libbpf_get_error(btf);
> > > +     if (err)
> > > +             return err;
> > > +
> > > +     err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
> > > +     btf__free(btf);
> > > +     if (err <= 0)
> > > +             return err;
> > > +
> > > +     return err;
> > > +}
> > > +
> > > +int load_fentry(int attach_prog_fd, int attach_btf_id)
> > static
> 
> Thx!
> 
> > > +{
> > > +     LIBBPF_OPTS(bpf_prog_load_opts, opts,
> > > +                 .expected_attach_type = BPF_TRACE_FENTRY,
> > > +                 .attach_prog_fd = attach_prog_fd,
> > > +                 .attach_btf_id = attach_btf_id,
> > > +                 .log_buf = bpf_log_buf,
> > > +                 .log_size = sizeof(bpf_log_buf),
> > > +     );
> > > +     struct bpf_insn insns[] = {
> > > +             BPF_MOV64_IMM(BPF_REG_0, 0),
> > > +             BPF_EXIT_INSN(),
> > > +     };
> > > +     int ret;
> > > +
> > > +     ret = bpf_prog_load(BPF_PROG_TYPE_TRACING,
> > > +                         "bind4_fentry",
> > > +                         "GPL",
> > > +                         insns,
> > > +                         ARRAY_SIZE(insns),
> > > +                         &opts);
> > > +     if (ret)
> > > +             printf("verifier log: %s\n", bpf_log_buf);
> > If this fentry prog is in the attach_to_bpf.c and load by skel, this printf
> > and the bpf_log_buf can go away.  I wonder if it can use the '?' like
> > SEC("?cgroup/bind4") and SEC("?fentry").  Then opens attach_to_bpf.skel.h
> > twice and use bpf_program__set_autoload() to load individual program .
> 
> Good ideal, let me try to see if doing "?fentry" is easier..
> (unless we agree to keep load_fentry, see below)
> 
> > Another option could be to reuse the progs/bind4_prog.c and directly
> > put the fentry program in the attach_to_bpf.c.
> >
> > btw, this test feels like something that could be a few line
> > addition to the test_fexit_bpf2bpf_common() in fexit_bpf2bpf.c.
> > Adding one to test fentry into a cgroup bpf prog is also good.
> > No strong opinion here also.
> 
> I was trying to reuse fexit_bpf2bpf initially but I sank too much time
> into it and decided that it might be easier to write a
> simpler/separate reproducer instead :-(
> How about we reuse progs/bind4_prog.c and keep load_fentry() ? And put
> this new test in fexit_bpf2bpf.c ?
Reusing bind4_prog.c sounds good.  Either use bind4_prog.c in the
new prog_tests/attach_to_bpf.c (likely need a better name) or the
fexit_bpf2bpf.c is fine.  Whatever makes more sense.
I was mostly thinking to avoid the special verifier log buf handling and
the printf here.  If an empty fentry prog may look weird, may be just
skip the bpf_log_buf and printf since it will never fail and keep the
load_fentry ?
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
new file mode 100644
index 000000000000..fcf726c5ff0f
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/attach_to_bpf.c
@@ -0,0 +1,109 @@ 
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <bpf/btf.h>
+#include <test_progs.h>
+#include <network_helpers.h>
+#include "attach_to_bpf.skel.h"
+
+char bpf_log_buf[BPF_LOG_BUF_SIZE];
+
+static int find_prog_btf_id(const char *name, __u32 attach_prog_fd)
+{
+	struct bpf_prog_info info = {};
+	__u32 info_len = sizeof(info);
+	struct btf *btf;
+	int err;
+
+	err = bpf_obj_get_info_by_fd(attach_prog_fd, &info, &info_len);
+	if (err)
+		return err;
+
+	if (!info.btf_id)
+		return -EINVAL;
+
+	btf = btf__load_from_kernel_by_id(info.btf_id);
+	err = libbpf_get_error(btf);
+	if (err)
+		return err;
+
+	err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
+	btf__free(btf);
+	if (err <= 0)
+		return err;
+
+	return err;
+}
+
+int load_fentry(int attach_prog_fd, int attach_btf_id)
+{
+	LIBBPF_OPTS(bpf_prog_load_opts, opts,
+		    .expected_attach_type = BPF_TRACE_FENTRY,
+		    .attach_prog_fd = attach_prog_fd,
+		    .attach_btf_id = attach_btf_id,
+		    .log_buf = bpf_log_buf,
+		    .log_size = sizeof(bpf_log_buf),
+	);
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	int ret;
+
+	ret = bpf_prog_load(BPF_PROG_TYPE_TRACING,
+			    "bind4_fentry",
+			    "GPL",
+			    insns,
+			    ARRAY_SIZE(insns),
+			    &opts);
+	if (ret)
+		printf("verifier log: %s\n", bpf_log_buf);
+	return ret;
+}
+
+void test_attach_to_bpf(void)
+{
+	struct attach_to_bpf *skel = NULL;
+	struct bpf_prog_info info = {};
+	__u32 info_len = sizeof(info);
+	int cgroup_fd = -1;
+	int fentry_fd = -1;
+	int btf_id;
+
+	cgroup_fd = test__join_cgroup("/attach_to_bpf");
+	if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))
+		return;
+
+	skel = attach_to_bpf__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel"))
+		goto cleanup;
+
+	skel->links.bind4 = bpf_program__attach_cgroup(skel->progs.bind4, cgroup_fd);
+	if (!ASSERT_OK_PTR(skel, "bpf_program__attach_cgroup"))
+		goto cleanup;
+
+	btf_id = find_prog_btf_id("bind4", bpf_program__fd(skel->progs.bind4));
+	if (!ASSERT_GE(btf_id, 0, "find_prog_btf_id"))
+		goto cleanup;
+
+	fentry_fd = load_fentry(bpf_program__fd(skel->progs.bind4), btf_id);
+	if (!ASSERT_GE(fentry_fd, 0, "load_fentry"))
+		goto cleanup;
+
+	/* Make sure bpf_obj_get_info_by_fd works correctly when attaching
+	 * to another BPF program.
+	 */
+
+	if (!ASSERT_OK(bpf_obj_get_info_by_fd(fentry_fd, &info, &info_len),
+		       "bpf_obj_get_info_by_fd"))
+		goto cleanup;
+
+	ASSERT_EQ(info.btf_id, 0, "info.btf_id");
+	ASSERT_GT(info.attach_btf_id, 0, "info.attach_btf_id");
+	ASSERT_GT(info.attach_btf_obj_id, 0, "info.attach_btf_obj_id");
+
+cleanup:
+	close(cgroup_fd);
+	close(fentry_fd);
+	attach_to_bpf__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/attach_to_bpf.c b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
new file mode 100644
index 000000000000..3f111fe96f8f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/attach_to_bpf.c
@@ -0,0 +1,12 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+SEC("cgroup/bind4")
+int bind4(struct bpf_sock_addr *ctx)
+{
+	return 1;
+}
+
+char _license[] SEC("license") = "GPL";