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bpf: Add selftests for BPF_MODIFY_RETURN

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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: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200304191853.1529-8-kpsingh@chromium.org
This commit is contained in:
KP Singh
2020-03-04 20:18:53 +01:00
committed by Alexei Starovoitov
parent da00d2f117
commit 3d08b6f29c
3 changed files with 135 additions and 1 deletions
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65
tools/testing/selftests/bpf/prog_tests/modify_return.c Normal file
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// 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 */);
}