[PATCH bpf-next v3 3/7] bpf: Introduce task open coded iterator kfuncs

Chuyi Zhou
2023-09-25T10:56:40Z

This patch adds kfuncs bpf_iter_task_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_task in open-coded iterator
style. BPF programs can use these kfuncs or through bpf_for_each macro to
iterate all processes in the system.

The API design keep consistent with SEC("iter/task"). bpf_iter_task_new()
accepts a specific task and iterating type which allows:
1. iterating all process in the system

2. iterating all threads in the system

3. iterating all threads of a specific task
Here we also resuse enum bpf_iter_task_type and rename BPF_TASK_ITER_TID
to BPF_TASK_ITER_THREAD, rename BPF_TASK_ITER_TGID to BPF_TASK_ITER_PROC.

The newly-added struct bpf_iter_task has a name collision with a selftest
for the seq_file task iter's bpf skel, so the selftests/bpf/progs file is
renamed in order to avoid the collision.

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
---
include/linux/bpf.h | 8 +-
kernel/bpf/helpers.c | 3 +
kernel/bpf/task_iter.c | 96 ++++++++++++++++---
.../testing/selftests/bpf/bpf_experimental.h | 5 +
.../selftests/bpf/prog_tests/bpf_iter.c | 18 ++--
.../{bpf_iter_task.c => bpf_iter_tasks.c} | 0
6 files changed, 106 insertions(+), 24 deletions(-)
rename tools/testing/selftests/bpf/progs/{bpf_iter_task.c => bpf_iter_tasks.c} (100%)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 87eeb3a46a1d..0ef5b7a59d62 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2194,16 +2194,16 @@ int bpf_obj_get_user(int path_fd, const char __user *pathname, int flags);
* BPF_TASK_ITER_ALL (default)
* Iterate over resources of every task.
*
- * BPF_TASK_ITER_TID
+ * BPF_TASK_ITER_THREAD
* Iterate over resources of a task/tid.
*
- * BPF_TASK_ITER_TGID
+ * BPF_TASK_ITER_PROC
* Iterate over resources of every task of a process / task group.
*/
enum bpf_iter_task_type {
BPF_TASK_ITER_ALL = 0,
- BPF_TASK_ITER_TID,
- BPF_TASK_ITER_TGID,
+ BPF_TASK_ITER_THREAD,
+ BPF_TASK_ITER_PROC,
};

struct bpf_iter_aux_info {
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 189d158c9b7f..556262c27a75 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2507,6 +2507,9 @@ BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_iter_css_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
BTF_ID_FLAGS(func, bpf_iter_css_task_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_css_task_destroy, KF_ITER_DESTROY)
+BTF_ID_FLAGS(func, bpf_iter_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_iter_task_next, KF_ITER_NEXT | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_iter_task_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_dynptr_adjust)
BTF_ID_FLAGS(func, bpf_dynptr_is_null)
BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index 2cfcb4dd8a37..9bcd3f9922b1 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -94,7 +94,7 @@ static struct task_struct *task_seq_get_next(struct bpf_iter_seq_task_common *co
struct task_struct *task = NULL;
struct pid *pid;

- if (common->type == BPF_TASK_ITER_TID) {
+ if (common->type == BPF_TASK_ITER_THREAD) {
if (*tid && *tid != common->pid)
return NULL;
rcu_read_lock();
@@ -108,7 +108,7 @@ static struct task_struct *task_seq_get_next(struct bpf_iter_seq_task_common *co
return task;
}

- if (common->type == BPF_TASK_ITER_TGID) {
+ if (common->type == BPF_TASK_ITER_PROC) {
rcu_read_lock();
task = task_group_seq_get_next(common, tid, skip_if_dup_files);
rcu_read_unlock();
@@ -217,15 +217,15 @@ static int bpf_iter_attach_task(struct bpf_prog *prog,

aux->task.type = BPF_TASK_ITER_ALL;
if (linfo->task.tid != 0) {
- aux->task.type = BPF_TASK_ITER_TID;
+ aux->task.type = BPF_TASK_ITER_THREAD;
aux->task.pid = linfo->task.tid;
}
if (linfo->task.pid != 0) {
- aux->task.type = BPF_TASK_ITER_TGID;
+ aux->task.type = BPF_TASK_ITER_PROC;
aux->task.pid = linfo->task.pid;
}
if (linfo->task.pid_fd != 0) {
- aux->task.type = BPF_TASK_ITER_TGID;
+ aux->task.type = BPF_TASK_ITER_PROC;

pid = pidfd_get_pid(linfo->task.pid_fd, &flags);
if (IS_ERR(pid))
@@ -305,7 +305,7 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info)
rcu_read_unlock();
put_task_struct(curr_task);

- if (info->common.type == BPF_TASK_ITER_TID) {
+ if (info->common.type == BPF_TASK_ITER_THREAD) {
info->task = NULL;
return NULL;
}
@@ -566,7 +566,7 @@ task_vma_seq_get_next(struct bpf_iter_seq_task_vma_info *info)
return curr_vma;

next_task:
- if (info->common.type == BPF_TASK_ITER_TID)
+ if (info->common.type == BPF_TASK_ITER_THREAD)
goto finish;

put_task_struct(curr_task);
@@ -677,10 +677,10 @@ static const struct bpf_iter_seq_info task_seq_info = {
static int bpf_iter_fill_link_info(const struct bpf_iter_aux_info *aux, struct bpf_link_info *info)
{
switch (aux->task.type) {
- case BPF_TASK_ITER_TID:
+ case BPF_TASK_ITER_THREAD:
info->iter.task.tid = aux->task.pid;
break;
- case BPF_TASK_ITER_TGID:
+ case BPF_TASK_ITER_PROC:
info->iter.task.pid = aux->task.pid;
break;
default:
@@ -692,9 +692,9 @@ static int bpf_iter_fill_link_info(const struct bpf_iter_aux_info *aux, struct b
static void bpf_iter_task_show_fdinfo(const struct bpf_iter_aux_info *aux, struct seq_file *seq)
{
seq_printf(seq, "task_type:\t%s\n", iter_task_type_names[aux->task.type]);
- if (aux->task.type == BPF_TASK_ITER_TID)
+ if (aux->task.type == BPF_TASK_ITER_THREAD)
seq_printf(seq, "tid:\t%u\n", aux->task.pid);
- else if (aux->task.type == BPF_TASK_ITER_TGID)
+ else if (aux->task.type == BPF_TASK_ITER_PROC)
seq_printf(seq, "pid:\t%u\n", aux->task.pid);
}

@@ -856,6 +856,80 @@ __bpf_kfunc void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it)
bpf_mem_free(&bpf_global_ma, kit->css_it);
}

+struct bpf_iter_task {
+ __u64 __opaque[2];
+ __u32 __opaque_int[1];
+} __attribute__((aligned(8)));
+
+struct bpf_iter_task_kern {
+ struct task_struct *task;
+ struct task_struct *pos;
+ unsigned int type;
+} __attribute__((aligned(8)));
+
+__bpf_kfunc int bpf_iter_task_new(struct bpf_iter_task *it, struct task_struct *task, unsigned int type)
+{
+ struct bpf_iter_task_kern *kit = (void *)it;
+ BUILD_BUG_ON(sizeof(struct bpf_iter_task_kern) != sizeof(struct bpf_iter_task));
+ BUILD_BUG_ON(__alignof__(struct bpf_iter_task_kern) !=
+ __alignof__(struct bpf_iter_task));
+ kit->task = kit->pos = NULL;
+ switch (type) {
+ case BPF_TASK_ITER_ALL:
+ case BPF_TASK_ITER_PROC:
+ case BPF_TASK_ITER_THREAD:
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (type == BPF_TASK_ITER_THREAD)
+ kit->task = task;
+ else
+ kit->task = &init_task;
+ kit->pos = kit->task;
+ kit->type = type;
+ return 0;
+}
+
+__bpf_kfunc struct task_struct *bpf_iter_task_next(struct bpf_iter_task *it)
+{
+ struct bpf_iter_task_kern *kit = (void *)it;
+ struct task_struct *pos;
+ unsigned int type;
+
+ type = kit->type;
+ pos = kit->pos;
+
+ if (!pos)
+ goto out;
+
+ if (type == BPF_TASK_ITER_PROC)
+ goto get_next_task;
+
+ kit->pos = next_thread(kit->pos);
+ if (kit->pos == kit->task) {
+ if (type == BPF_TASK_ITER_THREAD) {
+ kit->pos = NULL;
+ goto out;
+ }
+ } else
+ goto out;
+
+get_next_task:
+ kit->pos = next_task(kit->pos);
+ kit->task = kit->pos;
+ if (kit->pos == &init_task)
+ kit->pos = NULL;
+
+out:
+ return pos;
+}
+
+__bpf_kfunc void bpf_iter_task_destroy(struct bpf_iter_task *it)
+{
+}
+
DEFINE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work);

static void do_mmap_read_unlock(struct irq_work *entry)
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index d3ea90f0e142..d989775dbdb5 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -169,4 +169,9 @@ extern int bpf_iter_css_task_new(struct bpf_iter_css_task *it,
extern struct task_struct *bpf_iter_css_task_next(struct bpf_iter_css_task *it) __weak __ksym;
extern void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it) __weak __ksym;

+struct bpf_iter_task;
+extern int bpf_iter_task_new(struct bpf_iter_task *it, struct task_struct *task, unsigned int type) __weak __ksym;
+extern struct task_struct *bpf_iter_task_next(struct bpf_iter_task *it) __weak __ksym;
+extern void bpf_iter_task_destroy(struct bpf_iter_task *it) __weak __ksym;
+
#endif
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index 1f02168103dd..dc60e8e125cd 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -7,7 +7,7 @@
#include "bpf_iter_ipv6_route.skel.h"
#include "bpf_iter_netlink.skel.h"
#include "bpf_iter_bpf_map.skel.h"
-#include "bpf_iter_task.skel.h"
+#include "bpf_iter_tasks.skel.h"
#include "bpf_iter_task_stack.skel.h"
#include "bpf_iter_task_file.skel.h"
#include "bpf_iter_task_vma.skel.h"
@@ -215,12 +215,12 @@ static void *do_nothing_wait(void *arg)
static void test_task_common_nocheck(struct bpf_iter_attach_opts *opts,
int *num_unknown, int *num_known)
{
- struct bpf_iter_task *skel;
+ struct bpf_iter_tasks *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"))
+ skel = bpf_iter_tasks__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "bpf_iter_tasks__open_and_load"))
return;

ASSERT_OK(pthread_mutex_lock(&do_nothing_mutex), "pthread_mutex_lock");
@@ -239,7 +239,7 @@ static void test_task_common_nocheck(struct bpf_iter_attach_opts *opts,
ASSERT_FALSE(pthread_join(thread_id, &ret) || ret != NULL,
"pthread_join");

- bpf_iter_task__destroy(skel);
+ bpf_iter_tasks__destroy(skel);
}

static void test_task_common(struct bpf_iter_attach_opts *opts, int num_unknown, int num_known)
@@ -307,10 +307,10 @@ static void test_task_pidfd(void)

static void test_task_sleepable(void)
{
- struct bpf_iter_task *skel;
+ struct bpf_iter_tasks *skel;

- skel = bpf_iter_task__open_and_load();
- if (!ASSERT_OK_PTR(skel, "bpf_iter_task__open_and_load"))
+ skel = bpf_iter_tasks__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "bpf_iter_tasks__open_and_load"))
return;

do_dummy_read(skel->progs.dump_task_sleepable);
@@ -320,7 +320,7 @@ static void test_task_sleepable(void)
ASSERT_GT(skel->bss->num_success_copy_from_user_task, 0,
"num_success_copy_from_user_task");

- bpf_iter_task__destroy(skel);
+ bpf_iter_tasks__destroy(skel);
}

static void test_task_stack(void)
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task.c b/tools/testing/selftests/bpf/progs/bpf_iter_tasks.c
similarity index 100%
rename from tools/testing/selftests/bpf/progs/bpf_iter_task.c
rename to tools/testing/selftests/bpf/progs/bpf_iter_tasks.c
--
2.20.1