Re: [PATCH bpf-next v4 6/7] selftests/bpf: Add selftests for new cgroup local storage

[Yonghong Song <yhs@meta.com>]

On 10/23/22 1:14 PM, David Vernet wrote:
> On Sun, Oct 23, 2022 at 11:05:46AM -0700, Yonghong Song wrote:
>> Add two tests for new cgroup local storage, one to test bpf program helpers
>> and user space map APIs, and the other to test recursive fentry
>> triggering won't deadlock.
>>
>> Signed-off-by: Yonghong Song <yhs@fb.com>
>> ---
>>   .../bpf/prog_tests/cgrp_local_storage.c       | 92 +++++++++++++++++++
>>   .../selftests/bpf/progs/cgrp_local_storage.c  | 88 ++++++++++++++++++
>>   .../selftests/bpf/progs/cgrp_ls_recursion.c   | 70 ++++++++++++++
>>   3 files changed, 250 insertions(+)
>>   create mode 100644 tools/testing/selftests/bpf/prog_tests/cgrp_local_storage.c
>>   create mode 100644 tools/testing/selftests/bpf/progs/cgrp_local_storage.c
>>   create mode 100644 tools/testing/selftests/bpf/progs/cgrp_ls_recursion.c
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/cgrp_local_storage.c b/tools/testing/selftests/bpf/prog_tests/cgrp_local_storage.c
>> new file mode 100644
>> index 000000000000..7ee21d598195
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/cgrp_local_storage.c
>> @@ -0,0 +1,92 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates.*/
>> +
>> +#define _GNU_SOURCE
>> +#include <unistd.h>
>> +#include <sys/syscall.h>
>> +#include <sys/types.h>
>> +#include <test_progs.h>
>> +#include "cgrp_local_storage.skel.h"
>> +#include "cgrp_ls_recursion.skel.h"
>> +
>> +static void test_sys_enter_exit(int cgroup_fd)
>> +{
>> +	struct cgrp_local_storage *skel;
>> +	long val1 = 1, val2 = 0;
>> +	int err;
>> +
>> +	skel = cgrp_local_storage__open_and_load();
>> +	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
>> +		return;
>> +
>> +	/* populate a value in cgrp_storage_2 */
>> +	err = bpf_map_update_elem(bpf_map__fd(skel->maps.cgrp_storage_2), &cgroup_fd, &val1, BPF_ANY);
>> +	if (!ASSERT_OK(err, "map_update_elem"))
>> +		goto out;
>> +
>> +	/* check value */
>> +	err = bpf_map_lookup_elem(bpf_map__fd(skel->maps.cgrp_storage_2), &cgroup_fd, &val2);
>> +	if (!ASSERT_OK(err, "map_lookup_elem"))
>> +		goto out;
>> +	if (!ASSERT_EQ(val2, 1, "map_lookup_elem, invalid val"))
>> +		goto out;
>> +
>> +	/* delete value */
>> +	err = bpf_map_delete_elem(bpf_map__fd(skel->maps.cgrp_storage_2), &cgroup_fd);
>> +	if (!ASSERT_OK(err, "map_delete_elem"))
>> +		goto out;
>> +
>> +	skel->bss->target_pid = syscall(SYS_gettid);
>> +
>> +	err = cgrp_local_storage__attach(skel);
>> +	if (!ASSERT_OK(err, "skel_attach"))
>> +		goto out;
>> +
>> +	syscall(SYS_gettid);
>> +	syscall(SYS_gettid);
>> +
>> +	skel->bss->target_pid = 0;
>> +
>> +	/* 3x syscalls: 1x attach and 2x gettid */
>> +	ASSERT_EQ(skel->bss->enter_cnt, 3, "enter_cnt");
>> +	ASSERT_EQ(skel->bss->exit_cnt, 3, "exit_cnt");
>> +	ASSERT_EQ(skel->bss->mismatch_cnt, 0, "mismatch_cnt");
>> +out:
>> +	cgrp_local_storage__destroy(skel);
>> +}
>> +
>> +static void test_recursion(int cgroup_fd)
>> +{
>> +	struct cgrp_ls_recursion *skel;
>> +	int err;
>> +
>> +	skel = cgrp_ls_recursion__open_and_load();
>> +	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
>> +		return;
>> +
>> +	err = cgrp_ls_recursion__attach(skel);
>> +	if (!ASSERT_OK(err, "skel_attach"))
>> +		goto out;
>> +
>> +	/* trigger sys_enter, make sure it does not cause deadlock */
>> +	syscall(SYS_gettid);
>> +
>> +out:
>> +	cgrp_ls_recursion__destroy(skel);
>> +}
>> +
>> +void test_cgrp_local_storage(void)
>> +{
>> +	int cgroup_fd;
>> +
>> +	cgroup_fd = test__join_cgroup("/cgrp_local_storage");
>> +	if (!ASSERT_GE(cgroup_fd, 0, "join_cgroup /cgrp_local_storage"))
>> +		return;
>> +
>> +	if (test__start_subtest("sys_enter_exit"))
>> +		test_sys_enter_exit(cgroup_fd);
>> +	if (test__start_subtest("recursion"))
>> +		test_recursion(cgroup_fd);
>> +
>> +	close(cgroup_fd);
>> +}
>> diff --git a/tools/testing/selftests/bpf/progs/cgrp_local_storage.c b/tools/testing/selftests/bpf/progs/cgrp_local_storage.c
>> new file mode 100644
>> index 000000000000..dee63d4c1512
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/cgrp_local_storage.c
>> @@ -0,0 +1,88 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
>> +
>> +#include "vmlinux.h"
>> +#include <bpf/bpf_helpers.h>
>> +#include <bpf/bpf_tracing.h>
>> +
>> +char _license[] SEC("license") = "GPL";
>> +
>> +struct {
>> +	__uint(type, BPF_MAP_TYPE_CGRP_STORAGE);
>> +	__uint(map_flags, BPF_F_NO_PREALLOC);
>> +	__type(key, int);
>> +	__type(value, long);
>> +} cgrp_storage_1 SEC(".maps");
>> +
>> +struct {
>> +	__uint(type, BPF_MAP_TYPE_CGRP_STORAGE);
>> +	__uint(map_flags, BPF_F_NO_PREALLOC);
>> +	__type(key, int);
>> +	__type(value, long);
>> +} cgrp_storage_2 SEC(".maps");
>> +
>> +#define MAGIC_VALUE 0xabcd1234
>> +
>> +pid_t target_pid = 0;
>> +int mismatch_cnt = 0;
>> +int enter_cnt = 0;
>> +int exit_cnt = 0;
>> +
>> +SEC("tp_btf/sys_enter")
>> +int BPF_PROG(on_enter, struct pt_regs *regs, long id)
>> +{
>> +	struct task_struct *task;
>> +	long *ptr;
>> +	int err;
>> +
>> +	task = bpf_get_current_task_btf();
>> +	if (task->pid != target_pid)
>> +		return 0;
>> +
>> +	/* populate value 0 */
>> +	ptr = bpf_cgrp_storage_get(&cgrp_storage_1, task->cgroups->dfl_cgrp, 0,
>> +				   BPF_LOCAL_STORAGE_GET_F_CREATE);
>> +	if (!ptr)
>> +		return 0;
>> +
>> +	/* delete value 0 */
>> +	err = bpf_cgrp_storage_delete(&cgrp_storage_1, task->cgroups->dfl_cgrp);
>> +	if (err)
>> +		return 0;
>> +
>> +	/* value is not available */
>> +	ptr = bpf_cgrp_storage_get(&cgrp_storage_1, task->cgroups->dfl_cgrp, 0, 0);
>> +	if (ptr)
>> +		return 0;
>> +
>> +	/* re-populate the value */
>> +	ptr = bpf_cgrp_storage_get(&cgrp_storage_1, task->cgroups->dfl_cgrp, 0,
>> +				   BPF_LOCAL_STORAGE_GET_F_CREATE);
>> +	if (!ptr)
>> +		return 0;
> 
> Should we also add a global int err variable to this program that we set
> any time we can't fetch an instance of the local storage, etc  and then
> check in the user space test progs logic?

I think we are fine here. The enter_cnt below should ensure all above
should not prematurely return. Otherwise, the test will fail.

> 
>> +	__sync_fetch_and_add(&enter_cnt, 1);
>> +	*ptr = MAGIC_VALUE + enter_cnt;
>> +
>> +	return 0;
>> +}
>> +
>> +SEC("tp_btf/sys_exit")
>> +int BPF_PROG(on_exit, struct pt_regs *regs, long id)
>> +{
>> +	struct task_struct *task;
>> +	long *ptr;
>> +
>> +	task = bpf_get_current_task_btf();
>> +	if (task->pid != target_pid)
>> +		return 0;
>> +
>> +	ptr = bpf_cgrp_storage_get(&cgrp_storage_1, task->cgroups->dfl_cgrp, 0,
>> +				   BPF_LOCAL_STORAGE_GET_F_CREATE);
>> +	if (!ptr)
>> +		return 0;
>> +
>> +	__sync_fetch_and_add(&exit_cnt, 1);
>> +	if (*ptr != MAGIC_VALUE + exit_cnt)
>> +		__sync_fetch_and_add(&mismatch_cnt, 1);
>> +	return 0;
>> +}
>> diff --git a/tools/testing/selftests/bpf/progs/cgrp_ls_recursion.c b/tools/testing/selftests/bpf/progs/cgrp_ls_recursion.c
>> new file mode 100644
>> index 000000000000..a043d8fefdac
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/cgrp_ls_recursion.c
>> @@ -0,0 +1,70 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
>> +
>> +#include "vmlinux.h"
>> +#include <bpf/bpf_helpers.h>
>> +#include <bpf/bpf_tracing.h>
>> +
>> +char _license[] SEC("license") = "GPL";
>> +
>> +struct {
>> +	__uint(type, BPF_MAP_TYPE_CGRP_STORAGE);
>> +	__uint(map_flags, BPF_F_NO_PREALLOC);
>> +	__type(key, int);
>> +	__type(value, long);
>> +} map_a SEC(".maps");
>> +
>> +struct {
>> +	__uint(type, BPF_MAP_TYPE_CGRP_STORAGE);
>> +	__uint(map_flags, BPF_F_NO_PREALLOC);
>> +	__type(key, int);
>> +	__type(value, long);
>> +} map_b SEC(".maps");
>> +
>> +SEC("fentry/bpf_local_storage_lookup")
>> +int BPF_PROG(on_lookup)
>> +{
>> +	struct task_struct *task = bpf_get_current_task_btf();
>> +
>> +	bpf_cgrp_storage_delete(&map_a, task->cgroups->dfl_cgrp);
>> +	bpf_cgrp_storage_delete(&map_b, task->cgroups->dfl_cgrp);
>> +	return 0;
>> +}
>> +
>> +SEC("fentry/bpf_local_storage_update")
>> +int BPF_PROG(on_update)
>> +{
>> +	struct task_struct *task = bpf_get_current_task_btf();
>> +	long *ptr;
>> +
>> +	ptr = bpf_cgrp_storage_get(&map_a, task->cgroups->dfl_cgrp, 0,
>> +				   BPF_LOCAL_STORAGE_GET_F_CREATE);
>> +	if (ptr)
>> +		*ptr += 1;
>> +
>> +	ptr = bpf_cgrp_storage_get(&map_b, task->cgroups->dfl_cgrp, 0,
>> +				   BPF_LOCAL_STORAGE_GET_F_CREATE);
>> +	if (ptr)
>> +		*ptr += 1;
>> +
>> +	return 0;
>> +}
>> +
>> +SEC("tp_btf/sys_enter")
>> +int BPF_PROG(on_enter, struct pt_regs *regs, long id)
>> +{
>> +	struct task_struct *task;
>> +	long *ptr;
>> +
>> +	task = bpf_get_current_task_btf();
>> +	ptr = bpf_cgrp_storage_get(&map_a, task->cgroups->dfl_cgrp, 0,
>> +				   BPF_LOCAL_STORAGE_GET_F_CREATE);
>> +	if (ptr)
>> +		*ptr = 200;
>> +
>> +	ptr = bpf_cgrp_storage_get(&map_b, task->cgroups->dfl_cgrp, 0,
>> +				   BPF_LOCAL_STORAGE_GET_F_CREATE);
>> +	if (ptr)
>> +		*ptr = 100;
>> +	return 0;
>> +}
>> -- 
>> 2.30.2
>>
> 
> 
> Looks reasonable overall. Should we also include any negative tests,
> like e.g. trying to invoke bpf_cgrp_storage_get() with a struct other
> than a cgroup?

I can add one.

> 
> 
> Thanks,
> David