Re: [PATCH bpf-next v2 2/2] selftests/bpf: Add testcase for updating attached freplace prog to prog_array map

[Yonghong Song <yonghong.song@linux.dev>]

On 7/26/24 8:39 AM, Leon Hwang wrote:
> Add a selftest to confirm the issue, which gets -EINVAL when update
> attached freplace prog to prog_array map, has been fixed.
>
> cd tools/testing/selftests/bpf; ./test_progs -t tailcalls
> 327/25  tailcalls/tailcall_freplace:OK
> 327     tailcalls:OK
> Summary: 1/25 PASSED, 0 SKIPPED, 0 FAILED
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>

LGTM with some comments below.

Acked-by: Yonghong Song <yonghong.song@linux.dev>

> ---
>   .../selftests/bpf/prog_tests/tailcalls.c      | 65 ++++++++++++++++++-
>   .../selftests/bpf/progs/tailcall_freplace.c   | 25 +++++++
>   .../testing/selftests/bpf/progs/tc_bpf2bpf.c  | 21 ++++++
>   3 files changed, 110 insertions(+), 1 deletion(-)
>   create mode 100644 tools/testing/selftests/bpf/progs/tailcall_freplace.c
>   create mode 100644 tools/testing/selftests/bpf/progs/tc_bpf2bpf.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> index e01fabb8cc415..21c5a37846ade 100644
> --- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> +++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> @@ -5,7 +5,8 @@
>   #include "tailcall_poke.skel.h"
>   #include "tailcall_bpf2bpf_hierarchy2.skel.h"
>   #include "tailcall_bpf2bpf_hierarchy3.skel.h"
> -
> +#include "tailcall_freplace.skel.h"
> +#include "tc_bpf2bpf.skel.h"
>   
>   /* test_tailcall_1 checks basic functionality by patching multiple locations
>    * in a single program for a single tail call slot with nop->jmp, jmp->nop
> @@ -1495,6 +1496,66 @@ static void test_tailcall_bpf2bpf_hierarchy_3(void)
>   	RUN_TESTS(tailcall_bpf2bpf_hierarchy3);
>   }
>   
> +/* test_tailcall_freplace checks that the attached freplace prog is OK to
> + * update the prog_array map.
> + */
> +static void test_tailcall_freplace(void)
> +{
> +	struct tailcall_freplace *freplace_skel = NULL;
> +	struct bpf_link *freplace_link = NULL;
> +	struct bpf_program *freplace_prog;
> +	struct tc_bpf2bpf *tc_skel = NULL;
> +	int prog_fd, map_fd;
> +	char buff[128] = {};
> +	int err, key;
> +
> +	LIBBPF_OPTS(bpf_test_run_opts, topts,
> +		    .data_in = buff,
> +		    .data_size_in = sizeof(buff),
> +		    .repeat = 1,
> +	);
> +
> +	freplace_skel = tailcall_freplace__open();
> +	if (!ASSERT_OK_PTR(freplace_skel, "tailcall_freplace__open"))
> +		return;
> +
> +	tc_skel = tc_bpf2bpf__open_and_load();
> +	if (!ASSERT_OK_PTR(tc_skel, "tc_bpf2bpf__open_and_load"))
> +		goto out;
> +
> +	prog_fd = bpf_program__fd(tc_skel->progs.entry_tc);
> +	freplace_prog = freplace_skel->progs.entry_freplace;
> +	err = bpf_program__set_attach_target(freplace_prog, prog_fd, "subprog");
> +	if (!ASSERT_OK(err, "set_attach_target"))
> +		goto out;
> +
> +	err = tailcall_freplace__load(freplace_skel);
> +	if (!ASSERT_OK(err, "tailcall_freplace__load"))
> +		goto out;
> +
> +	freplace_link = bpf_program__attach_freplace(freplace_prog, prog_fd,
> +						     "subprog");
> +	if (!ASSERT_OK_PTR(freplace_link, "attach_freplace"))
> +		goto out;
> +
> +	map_fd = bpf_map__fd(freplace_skel->maps.jmp_table);
> +	prog_fd = bpf_program__fd(freplace_prog);
> +	key = 0;
> +	err = bpf_map_update_elem(map_fd, &key, &prog_fd, BPF_ANY);
> +	if (!ASSERT_OK(err, "update jmp_table"))
> +		goto out;
> +
> +	prog_fd = bpf_program__fd(tc_skel->progs.entry_tc);
> +	err = bpf_prog_test_run_opts(prog_fd, &topts);
> +	ASSERT_OK(err, "test_run");
> +	ASSERT_EQ(topts.retval, 34, "test_run retval");
> +
> +out:
> +	bpf_link__destroy(freplace_link);
> +	tc_bpf2bpf__destroy(tc_skel);
> +	tailcall_freplace__destroy(freplace_skel);
> +}
> +
>   void test_tailcalls(void)
>   {
>   	if (test__start_subtest("tailcall_1"))
> @@ -1543,4 +1604,6 @@ void test_tailcalls(void)
>   		test_tailcall_bpf2bpf_hierarchy_fentry_entry();
>   	test_tailcall_bpf2bpf_hierarchy_2();
>   	test_tailcall_bpf2bpf_hierarchy_3();
> +	if (test__start_subtest("tailcall_freplace"))
> +		test_tailcall_freplace();
>   }
> diff --git a/tools/testing/selftests/bpf/progs/tailcall_freplace.c b/tools/testing/selftests/bpf/progs/tailcall_freplace.c
> new file mode 100644
> index 0000000000000..2966efc06ae8f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/tailcall_freplace.c
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
> +	__uint(max_entries, 1);
> +	__uint(key_size, sizeof(__u32));
> +	__uint(value_size, sizeof(__u32));
> +} jmp_table SEC(".maps");
> +
> +int count = 0;
> +
> +SEC("freplace")
> +int entry_freplace(struct __sk_buff *skb)
> +{
> +	count++;
> +
remove empty line here.
> +	bpf_tail_call_static(skb, &jmp_table, 0);
> +
remove empty line here.
> +	return count;
> +}
> +
> +char __license[] SEC("license") = "GPL";
> diff --git a/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c b/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c
> new file mode 100644
> index 0000000000000..980bb810b481c
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c
> @@ -0,0 +1,21 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +__noinline
> +int subprog(struct __sk_buff *skb)
> +{
> +	volatile int ret = 1;
> +
remove empty line here.
> +	asm volatile (""::"r+"(ret));
remove above 'volatile' key word and replace asm volatile with __sink(ret).
> +	return ret;
> +}
> +
> +SEC("tc")
> +int entry_tc(struct __sk_buff *skb)
> +{
> +	return subprog(skb);
> +}
> +
> +char __license[] SEC("license") = "GPL";