Re: [PATCH bpf-next 3/3] selftests/bpf: Add tests for get_func_[arg|ret|arg_cnt] helpers

[Jiri Olsa <jolsa@redhat.com>]

On Mon, Dec 06, 2021 at 02:03:54PM -0800, Andrii Nakryiko wrote:
> 
> On 12/4/21 6:07 AM, Jiri Olsa wrote:
> > Adding tests for get_func_[arg|ret|arg_cnt] helpers.
> > Using these helpers in fentry/fexit/fmod_ret programs.
> > 
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >   .../bpf/prog_tests/get_func_args_test.c       |  38 ++++++
> >   .../selftests/bpf/progs/get_func_args_test.c  | 112 ++++++++++++++++++
> >   2 files changed, 150 insertions(+)
> >   create mode 100644 tools/testing/selftests/bpf/prog_tests/get_func_args_test.c
> >   create mode 100644 tools/testing/selftests/bpf/progs/get_func_args_test.c
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/get_func_args_test.c b/tools/testing/selftests/bpf/prog_tests/get_func_args_test.c
> > new file mode 100644
> > index 000000000000..c24807ae4361
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/get_func_args_test.c
> > @@ -0,0 +1,38 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <test_progs.h>
> > +#include "get_func_args_test.skel.h"
> > +
> > +void test_get_func_args_test(void)
> > +{
> > +	struct get_func_args_test *skel = NULL;
> > +	__u32 duration = 0, retval;
> > +	int err, prog_fd;
> > +
> > +	skel = get_func_args_test__open_and_load();
> > +	if (!ASSERT_OK_PTR(skel, "get_func_args_test__open_and_load"))
> > +		return;
> > +
> > +	err = get_func_args_test__attach(skel);
> > +	if (!ASSERT_OK(err, "get_func_args_test__attach"))
> > +		goto cleanup;
> > +
> > +	prog_fd = bpf_program__fd(skel->progs.test1);
> > +	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
> > +				NULL, NULL, &retval, &duration);
> > +	ASSERT_OK(err, "test_run");
> > +	ASSERT_EQ(retval, 0, "test_run");
> > +
> > +	prog_fd = bpf_program__fd(skel->progs.fmod_ret_test);
> > +	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
> > +				NULL, NULL, &retval, &duration);
> > +	ASSERT_OK(err, "test_run");
> > +	ASSERT_EQ(retval, 1234, "test_run");
> 
> 
> are the other two programs executed implicitly during one of those test
> runs? Can you please leave a small comment somewhere here if that's true?

test1 triggers all the bpf_fentry_test* fentry/fexits
fmod_ret_test triggers the rest, I'll put it in comment

> 
> 
> > +
> > +	ASSERT_EQ(skel->bss->test1_result, 1, "test1_result");
> > +	ASSERT_EQ(skel->bss->test2_result, 1, "test2_result");
> > +	ASSERT_EQ(skel->bss->test3_result, 1, "test3_result");
> > +	ASSERT_EQ(skel->bss->test4_result, 1, "test4_result");
> > +
> > +cleanup:
> > +	get_func_args_test__destroy(skel);
> > +}
> > diff --git a/tools/testing/selftests/bpf/progs/get_func_args_test.c b/tools/testing/selftests/bpf/progs/get_func_args_test.c
> > new file mode 100644
> > index 000000000000..0d0a67c849ae
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/get_func_args_test.c
> > @@ -0,0 +1,112 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <linux/bpf.h>
> > +#include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_tracing.h>
> > +#include <errno.h>
> > +
> > +char _license[] SEC("license") = "GPL";
> > +
> > +__u64 test1_result = 0;
> > +SEC("fentry/bpf_fentry_test1")
> > +int BPF_PROG(test1)
> > +{
> > +	__u64 cnt = bpf_get_func_arg_cnt(ctx);
> > +	__u64 a = 0, z = 0, ret = 0;
> > +	__s64 err;
> > +
> > +	test1_result = cnt == 1;
> > +
> > +	/* valid arguments */
> > +	err = bpf_get_func_arg(ctx, 0, &a);
> > +	test1_result &= err == 0 && (int) a == 1;
> 
> 
> int cast unnecessary? but some ()'s wouldn't hurt...

it is, 'a' is int and trampoline saves it with 32-bit register like:

  mov    %edi,-0x8(%rbp)

so the upper 4 bytes are not zeroed

> 
> 
> > +
> > +	/* not valid argument */
> > +	err = bpf_get_func_arg(ctx, 1, &z);
> > +	test1_result &= err == -EINVAL;
> > +
> > +	/* return value fails in fentry */
> > +	err = bpf_get_func_ret(ctx, &ret);
> > +	test1_result &= err == -EINVAL;
> > +	return 0;
> > +}
> > +
> > +__u64 test2_result = 0;
> > +SEC("fexit/bpf_fentry_test2")
> > +int BPF_PROG(test2)
> > +{
> > +	__u64 cnt = bpf_get_func_arg_cnt(ctx);
> > +	__u64 a = 0, b = 0, z = 0, ret = 0;
> > +	__s64 err;
> > +
> > +	test2_result = cnt == 2;
> > +
> > +	/* valid arguments */
> > +	err = bpf_get_func_arg(ctx, 0, &a);
> > +	test2_result &= err == 0 && (int) a == 2;
> > +
> > +	err = bpf_get_func_arg(ctx, 1, &b);
> > +	test2_result &= err == 0 && b == 3;
> > +
> > +	/* not valid argument */
> > +	err = bpf_get_func_arg(ctx, 2, &z);
> > +	test2_result &= err == -EINVAL;
> > +
> > +	/* return value */
> > +	err = bpf_get_func_ret(ctx, &ret);
> > +	test2_result &= err == 0 && ret == 5;
> > +	return 0;
> > +}
> > +
> > +__u64 test3_result = 0;
> > +SEC("fmod_ret/bpf_modify_return_test")
> > +int BPF_PROG(fmod_ret_test, int _a, int *_b, int _ret)
> > +{
> > +	__u64 cnt = bpf_get_func_arg_cnt(ctx);
> > +	__u64 a = 0, b = 0, z = 0, ret = 0;
> > +	__s64 err;
> > +
> > +	test3_result = cnt == 2;
> > +
> > +	/* valid arguments */
> > +	err = bpf_get_func_arg(ctx, 0, &a);
> > +	test3_result &= err == 0 && (int) a == 1;
> > +
> > +	err = bpf_get_func_arg(ctx, 1, &b);
> > +	test3_result &= err == 0;
> 
> 
> why no checking of b value here?

right, ok

> 
> > +
> > +	/* not valid argument */
> > +	err = bpf_get_func_arg(ctx, 2, &z);
> > +	test3_result &= err == -EINVAL;
> > +
> > +	/* return value */
> > +	err = bpf_get_func_ret(ctx, &ret);
> > +	test3_result &= err == 0 && ret == 0;
> > +	return 1234;
> > +}
> > +
> > +__u64 test4_result = 0;
> > +SEC("fexit/bpf_modify_return_test")
> > +int BPF_PROG(fexit_test, int _a, __u64 _b, int _ret)
> > +{
> > +	__u64 cnt = bpf_get_func_arg_cnt(ctx);
> > +	__u64 a = 0, b = 0, z = 0, ret = 0;
> > +	__s64 err;
> > +
> > +	test4_result = cnt == 2;
> > +
> > +	/* valid arguments */
> > +	err = bpf_get_func_arg(ctx, 0, &a);
> > +	test4_result &= err == 0 && (int) a == 1;
> > +
> > +	err = bpf_get_func_arg(ctx, 1, &b);
> > +	test4_result &= err == 0;
> 
> 
> same, for consistency, b should have been checked, no?

ok

thanks,
jirka