Re: [PATCH bpf-next v5 3/3] selftests/bpf: Test parameterized task BPF iterators.

[Yonghong Song <yhs@fb.com>]

On 8/10/22 5:16 PM, Kui-Feng Lee wrote:
> Test iterators of vma, files, and tasks of tasks.
> 
> Ensure the API works appropriately to visit all tasks,
> tasks in a process, or a particular task.
> 
> Signed-off-by: Kui-Feng Lee <kuifeng@fb.com>
> ---
>   .../selftests/bpf/prog_tests/bpf_iter.c       | 204 ++++++++++++++++--
>   .../selftests/bpf/prog_tests/btf_dump.c       |   2 +-
>   .../selftests/bpf/progs/bpf_iter_task.c       |   9 +
>   .../selftests/bpf/progs/bpf_iter_task_file.c  |   7 +
>   .../selftests/bpf/progs/bpf_iter_task_vma.c   |   6 +-
>   5 files changed, 203 insertions(+), 25 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> index a33874b081b6..e66f1f3db562 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> @@ -1,6 +1,9 @@
>   // SPDX-License-Identifier: GPL-2.0
>   /* Copyright (c) 2020 Facebook */
>   #include <test_progs.h>
> +#include <sys/syscall.h>
> +#include <unistd.h>
> +#include <signal.h>

do we need unistd.h and signal.h?

>   #include "bpf_iter_ipv6_route.skel.h"
>   #include "bpf_iter_netlink.skel.h"
>   #include "bpf_iter_bpf_map.skel.h"
> @@ -42,13 +45,13 @@ static void test_btf_id_or_null(void)
>   	}
>   }
>   
> -static void do_dummy_read(struct bpf_program *prog)
> +static void do_dummy_read(struct bpf_program *prog, struct bpf_iter_attach_opts *opts)
>   {
>   	struct bpf_link *link;
>   	char buf[16] = {};
>   	int iter_fd, len;
>   
> -	link = bpf_program__attach_iter(prog, NULL);
> +	link = bpf_program__attach_iter(prog, opts);
>   	if (!ASSERT_OK_PTR(link, "attach_iter"))
>   		return;
>   
> @@ -91,7 +94,7 @@ static void test_ipv6_route(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_ipv6_route__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_ipv6_route);
> +	do_dummy_read(skel->progs.dump_ipv6_route, NULL);
>   
>   	bpf_iter_ipv6_route__destroy(skel);
>   }
> @@ -104,7 +107,7 @@ static void test_netlink(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_netlink__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_netlink);
> +	do_dummy_read(skel->progs.dump_netlink, NULL);
>   
>   	bpf_iter_netlink__destroy(skel);
>   }
> @@ -117,24 +120,139 @@ static void test_bpf_map(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_bpf_map__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_bpf_map);
> +	do_dummy_read(skel->progs.dump_bpf_map, NULL);
>   
>   	bpf_iter_bpf_map__destroy(skel);
>   }
>   
> -static void test_task(void)
> +static int pidfd_open(pid_t pid, unsigned int flags)
> +{
> +	return syscall(SYS_pidfd_open, pid, flags);
> +}
> +
> +static void check_bpf_link_info(const struct bpf_program *prog)
> +{
> +	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
> +	union bpf_iter_link_info linfo;
> +	struct bpf_link_info info = {};
> +	__u32 info_len;
> +	struct bpf_link *link;
> +	int err;

Reverse christmas tree style?

> +
> +	memset(&linfo, 0, sizeof(linfo));
> +	linfo.task.tid = getpid();
> +	opts.link_info = &linfo;
> +	opts.link_info_len = sizeof(linfo);
> +
> +	link = bpf_program__attach_iter(prog, &opts);
> +	if (!ASSERT_OK_PTR(link, "attach_iter"))
> +		return;
> +
> +	info_len = sizeof(info);
> +	err = bpf_obj_get_info_by_fd(bpf_link__fd(link), &info, &info_len);
> +	if (ASSERT_OK(err, "bpf_obj_get_info_by_fd"))
> +		ASSERT_EQ(info.iter.task.tid, getpid(), "check_task_tid");
> +
> +	bpf_link__destroy(link);
> +}
> +
> +static pthread_mutex_t do_nothing_mutex;
> +
> +static void *do_nothing_wait(void *arg)
> +{
> +	pthread_mutex_lock(&do_nothing_mutex);
> +	pthread_mutex_unlock(&do_nothing_mutex);
> +
> +	pthread_exit(arg);
> +}
> +
> +static void test_task_(struct bpf_iter_attach_opts *opts, int num_unknown, int num_known)

The function test_task_ name is weird. Maybe test_task_common?

>   {
>   	struct bpf_iter_task *skel;
> +	pthread_t thread_id;
> +	void *ret;
>   
>   	skel = bpf_iter_task__open_and_load();
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_task__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_task);
> +	if (!ASSERT_OK(pthread_mutex_init(&do_nothing_mutex, NULL), "pthread_mutex_init"))
> +		goto done;
> +	if (!ASSERT_OK(pthread_mutex_lock(&do_nothing_mutex), "pthread_mutex_lock"))
> +		goto done;
> +
> +	if (!ASSERT_OK(pthread_create(&thread_id, NULL, &do_nothing_wait, NULL),
> +		  "pthread_create"))
> +		goto done;
> +
> +
> +	skel->bss->tid = getpid();
> +
> +	do_dummy_read(skel->progs.dump_task, opts);
> +
> +	if (!ASSERT_OK(pthread_mutex_unlock(&do_nothing_mutex), "pthread_mutex_unlock"))
> +		goto done;
> +
> +	if (num_unknown >= 0)
> +		ASSERT_EQ(skel->bss->num_unknown_tid, num_unknown, "check_num_unknown_tid");
> +	if (num_known >= 0)
> +		ASSERT_EQ(skel->bss->num_known_tid, num_known, "check_num_known_tid");
>   
> +	ASSERT_FALSE(pthread_join(thread_id, &ret) || ret != NULL,
> +		     "pthread_join");
> +
> +done:
>   	bpf_iter_task__destroy(skel);
>   }
>   
> +static void test_task(void)
> +{
> +	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
> +	union bpf_iter_link_info linfo;
> +
> +	memset(&linfo, 0, sizeof(linfo));
> +	linfo.task.tid = getpid();
> +	opts.link_info = &linfo;
> +	opts.link_info_len = sizeof(linfo);
> +
> +	test_task_(&opts, 0, 1);
> +
> +	test_task_(NULL, -1, 1);
> +}
> +
> +static void test_task_tgid(void)
> +{
> +	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
> +	union bpf_iter_link_info linfo;
> +
> +	memset(&linfo, 0, sizeof(linfo));
> +	linfo.task.tgid = getpid();
> +	opts.link_info = &linfo;
> +	opts.link_info_len = sizeof(linfo);
> +
> +	test_task_(&opts, 1, 1);
> +}
> +
> +static void test_task_pidfd(void)
> +{
> +	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
> +	union bpf_iter_link_info linfo;
> +	int pidfd;
> +
> +	pidfd = pidfd_open(getpid(), 0);
> +	if (!ASSERT_GE(pidfd, 0, "pidfd_open"))
> +		return;
> +
> +	memset(&linfo, 0, sizeof(linfo));
> +	linfo.task.pid_fd = pidfd;

In kernel, pidfd has to be > 0 to be effective.
So in the above, you should use ASSERT_GT instead of
ASSERT_GE. For test_progs, pidfd == 0 won't happen
since the program does not close stdin.

> +	opts.link_info = &linfo;
> +	opts.link_info_len = sizeof(linfo);
> +
> +	test_task_(&opts, 1, 1);
> +
> +	close(pidfd);
> +}
> +
>   static void test_task_sleepable(void)
>   {
>   	struct bpf_iter_task *skel;
> @@ -143,7 +261,7 @@ static void test_task_sleepable(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_task__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_task_sleepable);
> +	do_dummy_read(skel->progs.dump_task_sleepable, NULL);
>   
>   	ASSERT_GT(skel->bss->num_expected_failure_copy_from_user_task, 0,
>   		  "num_expected_failure_copy_from_user_task");
> @@ -161,8 +279,8 @@ static void test_task_stack(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_task_stack__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_task_stack);
> -	do_dummy_read(skel->progs.get_task_user_stacks);
> +	do_dummy_read(skel->progs.dump_task_stack, NULL);
> +	do_dummy_read(skel->progs.get_task_user_stacks, NULL);
>   
>   	bpf_iter_task_stack__destroy(skel);
>   }
> @@ -174,7 +292,9 @@ static void *do_nothing(void *arg)
>   
>   static void test_task_file(void)
>   {
> +	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
>   	struct bpf_iter_task_file *skel;
> +	union bpf_iter_link_info linfo;
>   	pthread_t thread_id;
>   	void *ret;
>   
> @@ -188,15 +308,31 @@ static void test_task_file(void)
>   		  "pthread_create"))
>   		goto done;
>   
> -	do_dummy_read(skel->progs.dump_task_file);
> +	memset(&linfo, 0, sizeof(linfo));
> +	linfo.task.tid = getpid();
> +	opts.link_info = &linfo;
> +	opts.link_info_len = sizeof(linfo);
> +
> +	do_dummy_read(skel->progs.dump_task_file, &opts);
>   
>   	if (!ASSERT_FALSE(pthread_join(thread_id, &ret) || ret != NULL,
>   		  "pthread_join"))
>   		goto done;
>   
>   	ASSERT_EQ(skel->bss->count, 0, "check_count");
> +	ASSERT_EQ(skel->bss->unique_tgid_count, 1, "check_unique_tgid_count");
>   
> -done:
> +	skel->bss->count = 0;
> +	skel->bss->unique_tgid_count = 0;
> +
> +	do_dummy_read(skel->progs.dump_task_file, NULL);
> +
> +	ASSERT_GE(skel->bss->count, 0, "check_count");
> +	ASSERT_GE(skel->bss->unique_tgid_count, 1, "check_unique_tgid_count");

This is not precise. ASSERT_EQ will be better, right?
Maybe reset last_tgid as well?

> +
> +	check_bpf_link_info(skel->progs.dump_task_file);
> +
> + done:
>   	bpf_iter_task_file__destroy(skel);
>   }
>   
> @@ -274,7 +410,7 @@ static void test_tcp4(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_tcp4__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_tcp4);
> +	do_dummy_read(skel->progs.dump_tcp4, NULL);
>   
>   	bpf_iter_tcp4__destroy(skel);
>   }
> @@ -287,7 +423,7 @@ static void test_tcp6(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_tcp6__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_tcp6);
> +	do_dummy_read(skel->progs.dump_tcp6, NULL);
>   
>   	bpf_iter_tcp6__destroy(skel);
>   }
> @@ -300,7 +436,7 @@ static void test_udp4(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_udp4__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_udp4);
> +	do_dummy_read(skel->progs.dump_udp4, NULL);
>   
>   	bpf_iter_udp4__destroy(skel);
>   }
> @@ -313,7 +449,7 @@ static void test_udp6(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_udp6__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_udp6);
> +	do_dummy_read(skel->progs.dump_udp6, NULL);
>   
>   	bpf_iter_udp6__destroy(skel);
>   }
> @@ -326,7 +462,7 @@ static void test_unix(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_unix__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_unix);
> +	do_dummy_read(skel->progs.dump_unix, NULL);
>   
>   	bpf_iter_unix__destroy(skel);
>   }
> @@ -988,7 +1124,7 @@ static void test_bpf_sk_storage_get(void)
>   	if (!ASSERT_OK(err, "bpf_map_update_elem"))
>   		goto close_socket;
>   
> -	do_dummy_read(skel->progs.fill_socket_owner);
> +	do_dummy_read(skel->progs.fill_socket_owner, NULL);
>   
>   	err = bpf_map_lookup_elem(map_fd, &sock_fd, &val);
>   	if (CHECK(err || val != getpid(), "bpf_map_lookup_elem",
> @@ -996,7 +1132,7 @@ static void test_bpf_sk_storage_get(void)
>   	    getpid(), val, err))
>   		goto close_socket;
>   
> -	do_dummy_read(skel->progs.negate_socket_local_storage);
> +	do_dummy_read(skel->progs.negate_socket_local_storage, NULL);
>   
>   	err = bpf_map_lookup_elem(map_fd, &sock_fd, &val);
>   	CHECK(err || val != -getpid(), "bpf_map_lookup_elem",
> @@ -1116,7 +1252,7 @@ static void test_link_iter(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_bpf_link__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_bpf_link);
> +	do_dummy_read(skel->progs.dump_bpf_link, NULL);
>   
>   	bpf_iter_bpf_link__destroy(skel);
>   }
> @@ -1129,7 +1265,7 @@ static void test_ksym_iter(void)
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_ksym__open_and_load"))
>   		return;
>   
> -	do_dummy_read(skel->progs.dump_ksym);
> +	do_dummy_read(skel->progs.dump_ksym, NULL);
>   
>   	bpf_iter_ksym__destroy(skel);
>   }
> @@ -1154,7 +1290,7 @@ static void str_strip_first_line(char *str)
>   	*dst = '\0';
>   }
>   
> -static void test_task_vma(void)
> +static void test_task_vma_(struct bpf_iter_attach_opts *opts)

test_task_vma_common?

>   {
>   	int err, iter_fd = -1, proc_maps_fd = -1;
>   	struct bpf_iter_task_vma *skel;
> @@ -1166,13 +1302,14 @@ static void test_task_vma(void)
>   		return;
>   
>   	skel->bss->pid = getpid();
> +	skel->bss->one_task = opts ? 1 : 0;
>   
>   	err = bpf_iter_task_vma__load(skel);
>   	if (!ASSERT_OK(err, "bpf_iter_task_vma__load"))
>   		goto out;
>   
>   	skel->links.proc_maps = bpf_program__attach_iter(
> -		skel->progs.proc_maps, NULL);
> +		skel->progs.proc_maps, opts);
>   
>   	if (!ASSERT_OK_PTR(skel->links.proc_maps, "bpf_program__attach_iter")) {
>   		skel->links.proc_maps = NULL;
> @@ -1211,12 +1348,29 @@ static void test_task_vma(void)
>   	str_strip_first_line(proc_maps_output);
>   
>   	ASSERT_STREQ(task_vma_output, proc_maps_output, "compare_output");
> +
> +	check_bpf_link_info(skel->progs.proc_maps);
> +
>   out:
>   	close(proc_maps_fd);
>   	close(iter_fd);
>   	bpf_iter_task_vma__destroy(skel);
>   }
>   
> +static void test_task_vma(void)
> +{
> +	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
> +	union bpf_iter_link_info linfo;
> +
> +	memset(&linfo, 0, sizeof(linfo));
> +	linfo.task.tid = getpid();
> +	opts.link_info = &linfo;
> +	opts.link_info_len = sizeof(linfo);
> +
> +	test_task_vma_(&opts);
> +	test_task_vma_(NULL);
> +}
> +
[...]
> diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_vma.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_vma.c
> index 4ea6a37d1345..44f4a31c2ddd 100644
> --- a/tools/testing/selftests/bpf/progs/bpf_iter_task_vma.c
> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_vma.c
> @@ -20,6 +20,7 @@ char _license[] SEC("license") = "GPL";
>   #define D_PATH_BUF_SIZE 1024
>   char d_path_buf[D_PATH_BUF_SIZE] = {};
>   __u32 pid = 0;
> +__u32 one_task = 0;
>   
>   SEC("iter/task_vma") int proc_maps(struct bpf_iter__task_vma *ctx)
>   {
> @@ -33,8 +34,11 @@ SEC("iter/task_vma") int proc_maps(struct bpf_iter__task_vma *ctx)
>   		return 0;
>   
>   	file = vma->vm_file;
> -	if (task->tgid != pid)
> +	if (task->tgid != pid) {
> +		if (one_task)
> +			BPF_SEQ_PRINTF(seq, "unexpected task (%d != %d)", task->tgid, pid);

This doesn't sound good. Is it possible we add a global variable to 
indicate this condition and do an ASSERT in bpf_iter.c file?

>   		return 0;
> +	}
>   	perm_str[0] = (vma->vm_flags & VM_READ) ? 'r' : '-';
>   	perm_str[1] = (vma->vm_flags & VM_WRITE) ? 'w' : '-';
>   	perm_str[2] = (vma->vm_flags & VM_EXEC) ? 'x' : '-';