[PATCH bpf-next v2 6/6] selftests/bpf: Add tests for open-coded task and css iter

Chuyi Zhou
2023-09-12T07:02:20Z

This patch adds three tests to demonstrate these patterns and validating
correctness.

test1: We use bpf_for_each(process, task) to iterate all process in the
system and search for the current process with a given pid.

test2: We create a cgroup and add the current task to the cgroup. In the
BPF program, we would use bpf_for_each(css_task, task, css) to iterate all
tasks under the cgroup. As expected, we would find the current process.

test3: We create a cgroup tree. In the BPF program, we use
bpf_for_each(css_{pre,post}, pos, root) to iterate all descendant under the
root with pre and post order. As expected, we would find all descendant and
the last iterating cgroup in post-order is root cgroup, the first
iterating cgroup in pre-order is root cgroup.

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
---
.../testing/selftests/bpf/prog_tests/iters.c | 138 ++++++++++++++++++
.../testing/selftests/bpf/progs/iters_task.c | 104 +++++++++++++
2 files changed, 242 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/iters_task.c

diff --git a/tools/testing/selftests/bpf/prog_tests/iters.c b/tools/testing/selftests/bpf/prog_tests/iters.c
index 10804ae5ae97..f4e69a506509 100644
--- a/tools/testing/selftests/bpf/prog_tests/iters.c
+++ b/tools/testing/selftests/bpf/prog_tests/iters.c
@@ -1,13 +1,21 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */

+#include <sys/syscall.h>
+#include <sys/mman.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <malloc.h>
+#include <stdlib.h>
#include <test_progs.h>
+#include "cgroup_helpers.h"

#include "iters.skel.h"
#include "iters_state_safety.skel.h"
#include "iters_looping.skel.h"
#include "iters_num.skel.h"
#include "iters_testmod_seq.skel.h"
+#include "iters_task.skel.h"

static void subtest_num_iters(void)
{
@@ -90,6 +98,130 @@ static void subtest_testmod_seq_iters(void)
iters_testmod_seq__destroy(skel);
}

+static void subtest_process_iters(void)
+{
+ struct iters_task *skel;
+ int err;
+
+ skel = iters_task__open();
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ goto cleanup;
+ bpf_program__set_autoload(skel->progs.iter_task_for_each_sleep, true);
+ err = iters_task__load(skel);
+ if (!ASSERT_OK(err, "skel_load"))
+ goto cleanup;
+ skel->bss->target_pid = getpid();
+ err = iters_task__attach(skel);
+ if (!ASSERT_OK(err, "iters_task__attach"))
+ goto cleanup;
+ syscall(SYS_getpgid);
+ iters_task__detach(skel);
+ ASSERT_EQ(skel->bss->process_cnt, 1, "process_cnt");
+
+cleanup:
+ iters_task__destroy(skel);
+}
+
+extern int stack_mprotect(void);
+
+static void subtest_css_task_iters(void)
+{
+ struct iters_task *skel;
+ int err, cg_fd, cg_id;
+ const char *cgrp_path = "/cg1";
+
+ err = setup_cgroup_environment();
+ if (!ASSERT_OK(err, "setup_cgroup_environment"))
+ goto cleanup;
+ cg_fd = create_and_get_cgroup(cgrp_path);
+ if (!ASSERT_GE(cg_fd, 0, "cg_create"))
+ goto cleanup;
+ cg_id = get_cgroup_id(cgrp_path);
+ err = join_cgroup(cgrp_path);
+ if (!ASSERT_OK(err, "setup_cgroup_environment"))
+ goto cleanup;
+
+ skel = iters_task__open();
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ goto cleanup;
+
+ bpf_program__set_autoload(skel->progs.iter_css_task_for_each, true);
+ err = iters_task__load(skel);
+ if (!ASSERT_OK(err, "skel_load"))
+ goto cleanup;
+
+ skel->bss->target_pid = getpid();
+ skel->bss->cg_id = cg_id;
+ err = iters_task__attach(skel);
+
+ err = stack_mprotect();
+ if (!ASSERT_OK(err, "iters_task__attach"))
+ goto cleanup;
+
+ iters_task__detach(skel);
+ ASSERT_EQ(skel->bss->css_task_cnt, 1, "css_task_cnt");
+
+cleanup:
+ cleanup_cgroup_environment();
+ iters_task__destroy(skel);
+}
+
+static void subtest_css_dec_iters(void)
+{
+ struct iters_task *skel;
+ struct {
+ const char *path;
+ int fd;
+ } cgs[] = {
+ { "/cg1" },
+ { "/cg1/cg2" },
+ { "/cg1/cg2/cg3" },
+ { "/cg1/cg2/cg3/cg4" },
+ };
+ int err, cg_nr = ARRAY_SIZE(cgs);
+ int i;
+
+ err = setup_cgroup_environment();
+ if (!ASSERT_OK(err, "setup_cgroup_environment"))
+ goto cleanup;
+ for (i = 0; i < cg_nr; i++) {
+ cgs[i].fd = create_and_get_cgroup(cgs[i].path);
+ if (!ASSERT_GE(cgs[i].fd, 0, "cg_create"))
+ goto cleanup;
+ }
+
+ skel = iters_task__open();
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ goto cleanup;
+ bpf_program__set_autoload(skel->progs.iter_css_dec_for_each, true);
+ err = iters_task__load(skel);
+ if (!ASSERT_OK(err, "skel_load"))
+ goto cleanup;
+
+ skel->bss->target_pid = getpid();
+ skel->bss->cg_id = get_cgroup_id(cgs[0].path);
+
+ err = iters_task__attach(skel);
+
+ if (!ASSERT_OK(err, "iters_task__attach"))
+ goto cleanup;
+
+ syscall(SYS_getpgid);
+ ASSERT_EQ(skel->bss->css_dec_cnt, cg_nr, "pre order search dec count");
+ ASSERT_EQ(skel->bss->first_cg_id, get_cgroup_id(cgs[0].path),
+ "pre order search first cgroup id");
+ skel->bss->css_dec_cnt = 0;
+ skel->bss->is_post_order = 1;
+ syscall(SYS_getpgid);
+ ASSERT_EQ(skel->bss->css_dec_cnt, cg_nr, "post order search dec count");
+ ASSERT_EQ(skel->bss->last_cg_id, get_cgroup_id(cgs[0].path),
+ "post order search last cgroup id");
+ iters_task__detach(skel);
+cleanup:
+ cleanup_cgroup_environment();
+ iters_task__destroy(skel);
+}
+
void test_iters(void)
{
RUN_TESTS(iters_state_safety);
@@ -103,4 +235,10 @@ void test_iters(void)
subtest_num_iters();
if (test__start_subtest("testmod_seq"))
subtest_testmod_seq_iters();
+ if (test__start_subtest("process"))
+ subtest_process_iters();
+ if (test__start_subtest("css_task"))
+ subtest_css_task_iters();
+ if (test__start_subtest("css_dec"))
+ subtest_css_dec_iters();
}
diff --git a/tools/testing/selftests/bpf/progs/iters_task.c b/tools/testing/selftests/bpf/progs/iters_task.c
new file mode 100644
index 000000000000..cf24a3b177f2
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/iters_task.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+char _license[] SEC("license") = "GPL";
+
+pid_t target_pid = 0;
+int process_cnt = 0;
+int css_task_cnt = 0;
+int css_dec_cnt = 0;
+
+char is_post_order;
+u64 cg_id;
+u64 last_cg_id;
+u64 first_cg_id;
+
+struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym;
+struct cgroup *bpf_cgroup_acquire(struct cgroup *cgrp) __ksym;
+void bpf_cgroup_release(struct cgroup *p) __ksym;
+void bpf_rcu_read_lock(void) __ksym;
+void bpf_rcu_read_unlock(void) __ksym;
+
+SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
+int iter_task_for_each_sleep(void *ctx)
+{
+ struct task_struct *task;
+ struct task_struct *cur_task = bpf_get_current_task_btf();
+
+ if (cur_task->pid != target_pid)
+ return 0;
+ bpf_rcu_read_lock();
+ bpf_for_each(process, task) {
+ if (task->pid == target_pid)
+ process_cnt += 1;
+ }
+ bpf_rcu_read_unlock();
+ return 0;
+}
+
+
+SEC("?lsm/file_mprotect")
+int BPF_PROG(iter_css_task_for_each)
+{
+ struct task_struct *task;
+ struct task_struct *cur_task = bpf_get_current_task_btf();
+
+ if (cur_task->pid != target_pid)
+ return 0;
+
+ struct cgroup *cgrp = bpf_cgroup_from_id(cg_id);
+
+ if (cgrp == NULL)
+ return 0;
+ struct cgroup_subsys_state *css = &cgrp->self;
+
+ bpf_for_each(css_task, task, css, CSS_TASK_ITER_PROCS) {
+ if (!task)
+ continue;
+ if (task->pid == target_pid)
+ css_task_cnt += 1;
+ }
+ bpf_cgroup_release(cgrp);
+ return 0;
+}
+
+SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
+int iter_css_dec_for_each(const void *ctx)
+{
+ struct task_struct *cur_task = bpf_get_current_task_btf();
+
+ if (cur_task->pid != target_pid)
+ return 0;
+
+ struct cgroup *cgrp = bpf_cgroup_from_id(cg_id);
+
+ if (cgrp == NULL)
+ return 0;
+ struct cgroup_subsys_state *root = &cgrp->self;
+ struct cgroup_subsys_state *pos = NULL;
+
+ bpf_rcu_read_lock();
+ if (is_post_order) {
+ bpf_for_each(css_post, pos, root) {
+ struct cgroup *cur_cgrp = pos->cgroup;
+
+ css_dec_cnt += 1;
+ if (cur_cgrp)
+ last_cg_id = cur_cgrp->kn->id;
+ }
+ } else {
+ bpf_for_each(css_pre, pos, root) {
+ struct cgroup *cur_cgrp = pos->cgroup;
+
+ css_dec_cnt += 1;
+ if (cur_cgrp && !first_cg_id)
+ first_cg_id = cur_cgrp->kn->id;
+ }
+ }
+ bpf_rcu_read_unlock();
+ bpf_cgroup_release(cgrp);
+ return 0;
+}
+
--
2.20.1