Commit 3d08b6f2 authored by KP Singh's avatar KP Singh Committed by Alexei Starovoitov
Browse files

bpf: Add selftests for BPF_MODIFY_RETURN 



Test for two scenarios:

  * When the fmod_ret program returns 0, the original function should
    be called along with fentry and fexit programs.
  * When the fmod_ret program returns a non-zero value, the original
    function should not be called, no side effect should be observed and
    fentry and fexit programs should be called.

The result from the kernel function call and whether a side-effect is
observed is returned via the retval attr of the BPF_PROG_TEST_RUN (bpf)
syscall.

Signed-off-by: default avatarKP Singh <kpsingh@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200304191853.1529-8-kpsingh@chromium.org
parent da00d2f1

net/bpf/test_run.c

+21 −1
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#include <net/bpf_sk_storage.h>

#include <net/sock.h>

#include <net/tcp.h>

#include <linux/error-injection.h>



#define CREATE_TRACE_POINTS

#include <trace/events/bpf_test_run.h>
@@ -143,6 +144,14 @@ int noinline bpf_fentry_test6(u64 a, void *b, short c, int d, void *e, u64 f) 
	return a + (long)b + c + d + (long)e + f;

}



int noinline bpf_modify_return_test(int a, int *b)

{

	*b += 1;

	return a + *b;

}



ALLOW_ERROR_INJECTION(bpf_modify_return_test, ERRNO);



static void *bpf_test_init(const union bpf_attr *kattr, u32 size,

			   u32 headroom, u32 tailroom)

{
@@ -168,7 +177,9 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog, 
			      const union bpf_attr *kattr,

			      union bpf_attr __user *uattr)

{

	int err = -EFAULT;

	u16 side_effect = 0, ret = 0;

	int b = 2, err = -EFAULT;

	u32 retval = 0;



	switch (prog->expected_attach_type) {

	case BPF_TRACE_FENTRY:
@@ -181,10 +192,19 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog, 
		    bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111)

			goto out;

		break;

	case BPF_MODIFY_RETURN:

		ret = bpf_modify_return_test(1, &b);

		if (b != 2)

			side_effect = 1;

		break;

	default:

		goto out;

	}



	retval = ((u32)side_effect << 16) | ret;

	if (copy_to_user(&uattr->test.retval, &retval, sizeof(retval)))

		goto out;



	err = 0;

out:

	trace_bpf_test_finish(&err);

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

0 → 100644
+65 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



/*

 * Copyright 2020 Google LLC.

 */



#include <test_progs.h>

#include "modify_return.skel.h"



#define LOWER(x) ((x) & 0xffff)

#define UPPER(x) ((x) >> 16)





static void run_test(__u32 input_retval, __u16 want_side_effect, __s16 want_ret)

{

	struct modify_return *skel = NULL;

	int err, prog_fd;

	__u32 duration = 0, retval;

	__u16 side_effect;

	__s16 ret;



	skel = modify_return__open_and_load();

	if (CHECK(!skel, "skel_load", "modify_return skeleton failed\n"))

		goto cleanup;



	err = modify_return__attach(skel);

	if (CHECK(err, "modify_return", "attach failed: %d\n", err))

		goto cleanup;



	skel->bss->input_retval = input_retval;

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

	err = bpf_prog_test_run(prog_fd, 1, NULL, 0, NULL, 0,

				&retval, &duration);



	CHECK(err, "test_run", "err %d errno %d\n", err, errno);



	side_effect = UPPER(retval);

	ret  = LOWER(retval);



	CHECK(ret != want_ret, "test_run",

	      "unexpected ret: %d, expected: %d\n", ret, want_ret);

	CHECK(side_effect != want_side_effect, "modify_return",

	      "unexpected side_effect: %d\n", side_effect);



	CHECK(skel->bss->fentry_result != 1, "modify_return",

	      "fentry failed\n");

	CHECK(skel->bss->fexit_result != 1, "modify_return",

	      "fexit failed\n");

	CHECK(skel->bss->fmod_ret_result != 1, "modify_return",

	      "fmod_ret failed\n");



cleanup:

	modify_return__destroy(skel);

}



void test_modify_return(void)

{

	run_test(0 /* input_retval */,

		 1 /* want_side_effect */,

		 4 /* want_ret */);

	run_test(-EINVAL /* input_retval */,

		 0 /* want_side_effect */,

		 -EINVAL /* want_ret */);

}

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

0 → 100644
+49 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



/*

 * Copyright 2020 Google LLC.

 */



#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



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



static int sequence = 0;

__s32 input_retval = 0;



__u64 fentry_result = 0;

SEC("fentry/bpf_modify_return_test")

int BPF_PROG(fentry_test, int a, __u64 b)

{

	sequence++;

	fentry_result = (sequence == 1);

	return 0;

}



__u64 fmod_ret_result = 0;

SEC("fmod_ret/bpf_modify_return_test")

int BPF_PROG(fmod_ret_test, int a, int *b, int ret)

{

	sequence++;

	/* This is the first fmod_ret program, the ret passed should be 0 */

	fmod_ret_result = (sequence == 2 && ret == 0);

	return input_retval;

}



__u64 fexit_result = 0;

SEC("fexit/bpf_modify_return_test")

int BPF_PROG(fexit_test, int a, __u64 b, int ret)

{

	sequence++;

	/* If the input_reval is non-zero a successful modification should have

	 * occurred.

	 */

	if (input_retval)

		fexit_result = (sequence == 3 && ret == input_retval);

	else

		fexit_result = (sequence == 3 && ret == 4);



	return 0;

}

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