Re: [PATCH bpf-next v4 2/5] selftests/bpf: Add tests for open-coded style process file iterator

[Jiri Olsa <olsajiri@gmail.com>]

On Tue, Nov 19, 2024 at 05:53:59PM +0000, Juntong Deng wrote:

SNIP

> +static void subtest_task_file_iters(void)
> +{
> +	int prog_fd, child_pid, wstatus, err = 0;
> +	const int stack_size = 1024 * 1024;
> +	struct iters_task_file *skel;
> +	struct files_test_args args;
> +	struct bpf_program *prog;
> +	bool setup_end, test_end;
> +	char *stack;
> +
> +	skel = iters_task_file__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "open_and_load"))
> +		return;
> +
> +	if (!ASSERT_OK(skel->bss->err, "pre_test_err"))
> +		goto cleanup_skel;
> +
> +	prog = bpf_object__find_program_by_name(skel->obj, "test_bpf_iter_task_file");
> +	if (!ASSERT_OK_PTR(prog, "find_program_by_name"))
> +		goto cleanup_skel;
> +
> +	prog_fd = bpf_program__fd(prog);
> +	if (!ASSERT_GT(prog_fd, -1, "bpf_program__fd"))
> +		goto cleanup_skel;

I don't think you need to check on this once we did iters_task_file__open_and_load 

> +
> +	stack = (char *)malloc(stack_size);
> +	if (!ASSERT_OK_PTR(stack, "clone_stack"))
> +		goto cleanup_skel;
> +
> +	setup_end = false;
> +	test_end = false;
> +
> +	args.setup_end = &setup_end;
> +	args.test_end = &test_end;
> +
> +	/* Note that there is no CLONE_FILES */
> +	child_pid = clone(task_file_test_process, stack + stack_size, CLONE_VM | SIGCHLD, &args);
> +	if (!ASSERT_GT(child_pid, -1, "child_pid"))
> +		goto cleanup_stack;
> +
> +	while (!setup_end)
> +		;

I thin kthe preferred way is to synchronize through pipe,
you can check prog_tests/uprobe_multi_test.c

> +
> +	skel->bss->pid = child_pid;
> +
> +	err = bpf_prog_test_run_opts(prog_fd, NULL);
> +	if (!ASSERT_OK(err, "prog_test_run"))
> +		goto cleanup_stack;
> +
> +	test_end = true;
> +
> +	if (!ASSERT_GT(waitpid(child_pid, &wstatus, 0), -1, "waitpid"))
> +		goto cleanup_stack;
> +
> +	if (!ASSERT_OK(WEXITSTATUS(wstatus), "run_task_file_iters_test_err"))
> +		goto cleanup_stack;
> +
> +	ASSERT_OK(skel->bss->err, "run_task_file_iters_test_failure");

could the test check on that the iterated files were (or contained) the ones we expected?

thanks,
jirka


> +cleanup_stack:
> +	free(stack);
> +cleanup_skel:
> +	iters_task_file__destroy(skel);
> +}
> +
>  void test_iters(void)
>  {
>  	RUN_TESTS(iters_state_safety);
> @@ -315,5 +417,8 @@ void test_iters(void)
>  		subtest_css_task_iters();
>  	if (test__start_subtest("css"))
>  		subtest_css_iters();
> +	if (test__start_subtest("task_file"))
> +		subtest_task_file_iters();
>  	RUN_TESTS(iters_task_failure);
> +	RUN_TESTS(iters_task_file_failure);
>  }
> diff --git a/tools/testing/selftests/bpf/progs/iters_task_file.c b/tools/testing/selftests/bpf/progs/iters_task_file.c
> new file mode 100644
> index 000000000000..f14b473936c7
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/iters_task_file.c
> @@ -0,0 +1,71 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +#include "bpf_misc.h"
> +#include "bpf_experimental.h"
> +#include "task_kfunc_common.h"
> +
> +char _license[] SEC("license") = "GPL";
> +
> +int err, pid;
> +
> +SEC("syscall")
> +int test_bpf_iter_task_file(void *ctx)
> +{
> +	struct bpf_iter_task_file task_file_it;
> +	struct bpf_iter_task_file_item *item;
> +	struct task_struct *task;
> +
> +	task = bpf_task_from_vpid(pid);
> +	if (task == NULL) {
> +		err = 1;
> +		return 0;
> +	}
> +
> +	bpf_rcu_read_lock();
> +	bpf_iter_task_file_new(&task_file_it, task);
> +
> +	item = bpf_iter_task_file_next(&task_file_it);
> +	if (item == NULL) {
> +		err = 2;
> +		goto cleanup;
> +	}
> +
> +	if (item->fd != 0) {
> +		err = 3;
> +		goto cleanup;
> +	}
> +
> +	item = bpf_iter_task_file_next(&task_file_it);
> +	if (item == NULL) {
> +		err = 4;
> +		goto cleanup;
> +	}
> +
> +	if (item->fd != 1) {
> +		err = 5;
> +		goto cleanup;
> +	}
> +
> +	item = bpf_iter_task_file_next(&task_file_it);
> +	if (item == NULL) {
> +		err = 6;
> +		goto cleanup;
> +	}
> +
> +	if (item->fd != 2) {
> +		err = 7;
> +		goto cleanup;
> +	}
> +
> +	item = bpf_iter_task_file_next(&task_file_it);
> +	if (item != NULL)
> +		err = 8;
> +cleanup:
> +	bpf_iter_task_file_destroy(&task_file_it);
> +	bpf_rcu_read_unlock();
> +	bpf_task_release(task);
> +	return 0;
> +}
> diff --git a/tools/testing/selftests/bpf/progs/iters_task_file_failure.c b/tools/testing/selftests/bpf/progs/iters_task_file_failure.c
> new file mode 100644
> index 000000000000..c3de9235b888
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/iters_task_file_failure.c
> @@ -0,0 +1,114 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +#include "bpf_misc.h"
> +#include "bpf_experimental.h"
> +#include "task_kfunc_common.h"
> +
> +char _license[] SEC("license") = "GPL";
> +
> +SEC("syscall")
> +__failure __msg("expected an RCU CS when using bpf_iter_task_file")
> +int bpf_iter_task_file_new_without_rcu_lock(void *ctx)
> +{
> +	struct bpf_iter_task_file task_file_it;
> +	struct task_struct *task;
> +
> +	task = bpf_get_current_task_btf();
> +
> +	bpf_iter_task_file_new(&task_file_it, task);
> +
> +	bpf_iter_task_file_destroy(&task_file_it);
> +	return 0;
> +}
> +
> +SEC("syscall")
> +__failure __msg("expected uninitialized iter_task_file as arg #1")
> +int bpf_iter_task_file_new_inited_iter(void *ctx)
> +{
> +	struct bpf_iter_task_file task_file_it;
> +	struct task_struct *task;
> +
> +	task = bpf_get_current_task_btf();
> +
> +	bpf_rcu_read_lock();
> +	bpf_iter_task_file_new(&task_file_it, task);
> +
> +	bpf_iter_task_file_new(&task_file_it, task);
> +
> +	bpf_iter_task_file_destroy(&task_file_it);
> +	bpf_rcu_read_unlock();
> +	return 0;
> +}
> +
> +SEC("syscall")
> +__failure __msg("Possibly NULL pointer passed to trusted arg1")
> +int bpf_iter_task_file_new_null_task(void *ctx)
> +{
> +	struct bpf_iter_task_file task_file_it;
> +	struct task_struct *task = NULL;
> +
> +	bpf_rcu_read_lock();
> +	bpf_iter_task_file_new(&task_file_it, task);
> +
> +	bpf_iter_task_file_destroy(&task_file_it);
> +	bpf_rcu_read_unlock();
> +	return 0;
> +}
> +
> +SEC("syscall")
> +__failure __msg("R2 must be referenced or trusted")
> +int bpf_iter_task_file_new_untrusted_task(void *ctx)
> +{
> +	struct bpf_iter_task_file task_file_it;
> +	struct task_struct *task;
> +
> +	task = bpf_get_current_task_btf()->parent;
> +
> +	bpf_rcu_read_lock();
> +	bpf_iter_task_file_new(&task_file_it, task);
> +
> +	bpf_iter_task_file_destroy(&task_file_it);
> +	bpf_rcu_read_unlock();
> +	return 0;
> +}
> +
> +SEC("syscall")
> +__failure __msg("Unreleased reference")
> +int bpf_iter_task_file_no_destory(void *ctx)
> +{
> +	struct bpf_iter_task_file task_file_it;
> +	struct task_struct *task;
> +
> +	task = bpf_get_current_task_btf();
> +
> +	bpf_rcu_read_lock();
> +	bpf_iter_task_file_new(&task_file_it, task);
> +
> +	bpf_rcu_read_unlock();
> +	return 0;
> +}
> +
> +SEC("syscall")
> +__failure __msg("expected an initialized iter_task_file as arg #1")
> +int bpf_iter_task_file_next_uninit_iter(void *ctx)
> +{
> +	struct bpf_iter_task_file task_file_it;
> +
> +	bpf_iter_task_file_next(&task_file_it);
> +
> +	return 0;
> +}
> +
> +SEC("syscall")
> +__failure __msg("expected an initialized iter_task_file as arg #1")
> +int bpf_iter_task_file_destroy_uninit_iter(void *ctx)
> +{
> +	struct bpf_iter_task_file task_file_it;
> +
> +	bpf_iter_task_file_destroy(&task_file_it);
> +
> +	return 0;
> +}
> -- 
> 2.39.5
>