Commit b191b0fd authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add tailcall epilogue test 



This patch adds a gen_epilogue test to test a main prog
using a bpf_tail_call.

A non test_loader test is used. The tailcall target program,
"test_epilogue_subprog", needs to be used in a struct_ops map
before it can be loaded. Another struct_ops map is also needed
to host the actual "test_epilogue_tailcall" struct_ops program
that does the bpf_tail_call. The earlier test_loader patch
will attach all struct_ops maps but the bpf_testmod.c does
not support >1 attached struct_ops.

The earlier patch used the test_loader which has already covered
checking for the patched pro/epilogue instructions. This is done
by the __xlated tag.

This patch goes for the regular skel load and syscall test to do
the tailcall test that can also allow to directly pass the
the "struct st_ops_args *args" as ctx_in to the
SEC("syscall") program.

Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20240829210833.388152-8-martin.lau@linux.dev


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 47e69431

tools/testing/selftests/bpf/prog_tests/pro_epilogue.c

+46 −0
Original line number Diff line number Diff line
@@ -3,8 +3,54 @@ 


#include <test_progs.h>

#include "pro_epilogue.skel.h"

#include "epilogue_tailcall.skel.h"



struct st_ops_args {

	__u64 a;

};



static void test_tailcall(void)

{

	LIBBPF_OPTS(bpf_test_run_opts, topts);

	struct epilogue_tailcall *skel;

	struct st_ops_args args;

	int err, prog_fd;



	skel = epilogue_tailcall__open_and_load();

	if (!ASSERT_OK_PTR(skel, "epilogue_tailcall__open_and_load"))

		return;



	topts.ctx_in = &args;

	topts.ctx_size_in = sizeof(args);



	skel->links.epilogue_tailcall =

		bpf_map__attach_struct_ops(skel->maps.epilogue_tailcall);

	if (!ASSERT_OK_PTR(skel->links.epilogue_tailcall, "attach_struct_ops"))

		goto done;



	/* Both test_epilogue_tailcall and test_epilogue_subprog are

	 * patched with epilogue. When syscall_epilogue_tailcall()

	 * is run, test_epilogue_tailcall() is triggered.

	 * It executes a tail call and control is transferred to

	 * test_epilogue_subprog(). Only test_epilogue_subprog()

	 * does args->a += 1, thus final args.a value of 10001

	 * guarantees that only the epilogue of the

	 * test_epilogue_subprog is executed.

	 */

	memset(&args, 0, sizeof(args));

	prog_fd = bpf_program__fd(skel->progs.syscall_epilogue_tailcall);

	err = bpf_prog_test_run_opts(prog_fd, &topts);

	ASSERT_OK(err, "bpf_prog_test_run_opts");

	ASSERT_EQ(args.a, 10001, "args.a");

	ASSERT_EQ(topts.retval, 10001 * 2, "topts.retval");



done:

	epilogue_tailcall__destroy(skel);

}



void test_pro_epilogue(void)

{

	RUN_TESTS(pro_epilogue);

	if (test__start_subtest("tailcall"))

		test_tailcall();

}

tools/testing/selftests/bpf/progs/epilogue_tailcall.c

0 → 100644
+58 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */



#include <vmlinux.h>

#include <bpf/bpf_tracing.h>

#include "bpf_misc.h"

#include "../bpf_testmod/bpf_testmod.h"

#include "../bpf_testmod/bpf_testmod_kfunc.h"



char _license[] SEC("license") = "GPL";



static __noinline __used int subprog(struct st_ops_args *args)

{

	args->a += 1;

	return args->a;

}



SEC("struct_ops/test_epilogue_subprog")

int BPF_PROG(test_epilogue_subprog, struct st_ops_args *args)

{

	subprog(args);

	return args->a;

}



struct {

	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);

	__uint(max_entries, 1);

	__uint(key_size, sizeof(__u32));

	__uint(value_size, sizeof(__u32));

	__array(values, void (void));

} epilogue_map SEC(".maps") = {

	.values = {

		[0] = (void *)&test_epilogue_subprog,

	}

};



SEC("struct_ops/test_epilogue_tailcall")

int test_epilogue_tailcall(unsigned long long *ctx)

{

	bpf_tail_call(ctx, &epilogue_map, 0);

	return 0;

}



SEC(".struct_ops.link")

struct bpf_testmod_st_ops epilogue_tailcall = {

	.test_epilogue = (void *)test_epilogue_tailcall,

};



SEC(".struct_ops.link")

struct bpf_testmod_st_ops epilogue_subprog = {

	.test_epilogue = (void *)test_epilogue_subprog,

};



SEC("syscall")

int syscall_epilogue_tailcall(struct st_ops_args *args)

{

	return bpf_kfunc_st_ops_test_epilogue(args);

}