Re: [PATCH bpf-next v1 5/8] selftests/bpf: bad_struct_ops test

[David Vernet <void@manifault.com>]

[-- Attachment #1: Type: text/plain, Size: 5593 bytes --]

On Tue, Feb 27, 2024 at 10:45:53PM +0200, Eduard Zingerman wrote:
> When loading struct_ops programs kernel requires BTF id of the
> struct_ops type and member index for attachment point inside that
> type. This makes it not possible to have same BPF program used in
> struct_ops maps that have different struct_ops type.
> Check if libbpf rejects such BPF objects files.
> 
> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
> ---
>  .../selftests/bpf/bpf_testmod/bpf_testmod.c   | 24 +++++++++++
>  .../selftests/bpf/bpf_testmod/bpf_testmod.h   |  4 ++
>  .../selftests/bpf/prog_tests/bad_struct_ops.c | 42 +++++++++++++++++++
>  .../selftests/bpf/progs/bad_struct_ops.c      | 17 ++++++++
>  4 files changed, 87 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/bad_struct_ops.c
>  create mode 100644 tools/testing/selftests/bpf/progs/bad_struct_ops.c
> 
> diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> index 0d8437e05f64..69f5eb9ad546 100644
> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> @@ -601,6 +601,29 @@ struct bpf_struct_ops bpf_bpf_testmod_ops = {
>  	.owner = THIS_MODULE,
>  };
>  
> +static int bpf_dummy_reg2(void *kdata)
> +{
> +	struct bpf_testmod_ops2 *ops = kdata;
> +
> +	ops->test_1();
> +	return 0;
> +}
> +
> +static struct bpf_testmod_ops2 __bpf_testmod_ops2 = {
> +	.test_1 = bpf_testmod_test_1,
> +};
> +
> +struct bpf_struct_ops bpf_testmod_ops2 = {
> +	.verifier_ops = &bpf_testmod_verifier_ops,
> +	.init = bpf_testmod_ops_init,
> +	.init_member = bpf_testmod_ops_init_member,
> +	.reg = bpf_dummy_reg2,
> +	.unreg = bpf_dummy_unreg,
> +	.cfi_stubs = &__bpf_testmod_ops2,
> +	.name = "bpf_testmod_ops2",
> +	.owner = THIS_MODULE,
> +};
> +
>  extern int bpf_fentry_test1(int a);
>  
>  static int bpf_testmod_init(void)
> @@ -612,6 +635,7 @@ static int bpf_testmod_init(void)
>  	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_testmod_kfunc_set);
>  	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_testmod_kfunc_set);
>  	ret = ret ?: register_bpf_struct_ops(&bpf_bpf_testmod_ops, bpf_testmod_ops);
> +	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops2, bpf_testmod_ops2);
>  	if (ret < 0)
>  		return ret;
>  	if (bpf_fentry_test1(0) < 0)
> diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
> index c3b0cf788f9f..3183fff7f246 100644
> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
> @@ -37,4 +37,8 @@ struct bpf_testmod_ops {
>  	int (*test_maybe_null)(int dummy, struct task_struct *task);
>  };
>  
> +struct bpf_testmod_ops2 {
> +	int (*test_1)(void);
> +};
> +
>  #endif /* _BPF_TESTMOD_H */
> diff --git a/tools/testing/selftests/bpf/prog_tests/bad_struct_ops.c b/tools/testing/selftests/bpf/prog_tests/bad_struct_ops.c
> new file mode 100644
> index 000000000000..9c689db4b05b
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/bad_struct_ops.c
> @@ -0,0 +1,42 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <test_progs.h>
> +#include "bad_struct_ops.skel.h"
> +
> +#define EXPECTED_MSG "libbpf: struct_ops reloc"
> +
> +static libbpf_print_fn_t old_print_cb;
> +static bool msg_found;
> +
> +static int print_cb(enum libbpf_print_level level, const char *fmt, va_list args)
> +{
> +	old_print_cb(level, fmt, args);
> +	if (level == LIBBPF_WARN && strncmp(fmt, EXPECTED_MSG, strlen(EXPECTED_MSG)) == 0)
> +		msg_found = true;
> +
> +	return 0;
> +}

Not necessary at all for this patch set / just an observation, but it would be
nice to have this be something offered by the core prog_tests framework
(meaning, the ability to assert libbpf output for a testcase).

> +
> +static void test_bad_struct_ops(void)
> +{
> +	struct bad_struct_ops *skel;
> +	int err;
> +
> +	old_print_cb = libbpf_set_print(print_cb);
> +	skel = bad_struct_ops__open_and_load();
> +	err = errno;
> +	libbpf_set_print(old_print_cb);
> +	if (!ASSERT_NULL(skel, "bad_struct_ops__open_and_load"))
> +		return;
> +
> +	ASSERT_EQ(err, EINVAL, "errno should be EINVAL");
> +	ASSERT_TRUE(msg_found, "expected message");
> +
> +	bad_struct_ops__destroy(skel);
> +}
> +
> +void serial_test_bad_struct_ops(void)
> +{
> +	if (test__start_subtest("test_bad_struct_ops"))
> +		test_bad_struct_ops();
> +}
> diff --git a/tools/testing/selftests/bpf/progs/bad_struct_ops.c b/tools/testing/selftests/bpf/progs/bad_struct_ops.c
> new file mode 100644
> index 000000000000..9c103afbfdb1
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bad_struct_ops.c
> @@ -0,0 +1,17 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <vmlinux.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include "../bpf_testmod/bpf_testmod.h"
> +
> +char _license[] SEC("license") = "GPL";
> +
> +SEC("struct_ops/test_1")
> +int BPF_PROG(test_1) { return 0; }
> +
> +SEC(".struct_ops.link")
> +struct bpf_testmod_ops testmod_1 = { .test_1 = (void *)test_1 };

Just to make be 100% sure that we're isolating the issue under test, should we
also add a .test_2 prog and add it to the struct bpf_testmod_ops map?

> +
> +SEC(".struct_ops.link")
> +struct bpf_testmod_ops2 testmod_2 = { .test_1 = (void *)test_1 };
> -- 
> 2.43.0
> 

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]