kernel/bpf/task_iter.c

Source file repositories/reference/linux-study-clean/kernel/bpf/task_iter.c

File Facts

System
Linux kernel
Corpus path
kernel/bpf/task_iter.c
Extension
.c
Size
29254 bytes
Lines
1192
Domain
Core OS
Bucket
Scheduler, Processes, Timers, Sync, And Syscalls
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

struct bpf_iter_seq_task_common {
	struct pid_namespace *ns;
	enum bpf_iter_task_type	type;
	u32 pid;
	u32 pid_visiting;
};

struct bpf_iter_seq_task_info {
	/* The first field must be struct bpf_iter_seq_task_common.
	 * this is assumed by {init, fini}_seq_pidns() callback functions.
	 */
	struct bpf_iter_seq_task_common common;
	u32 tid;
};

static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_common *common,
						   u32 *tid,
						   bool skip_if_dup_files)
{
	struct task_struct *task;
	struct pid *pid;
	u32 next_tid;

	if (!*tid) {
		/* The first time, the iterator calls this function. */
		pid = find_pid_ns(common->pid, common->ns);
		task = get_pid_task(pid, PIDTYPE_TGID);
		if (!task)
			return NULL;

		*tid = common->pid;
		common->pid_visiting = common->pid;

		return task;
	}

	/* If the control returns to user space and comes back to the
	 * kernel again, *tid and common->pid_visiting should be the
	 * same for task_seq_start() to pick up the correct task.
	 */
	if (*tid == common->pid_visiting) {
		pid = find_pid_ns(common->pid_visiting, common->ns);
		task = get_pid_task(pid, PIDTYPE_PID);

		return task;
	}

	task = find_task_by_pid_ns(common->pid_visiting, common->ns);
	if (!task)
		return NULL;

retry:
	task = __next_thread(task);
	if (!task)
		return NULL;

	next_tid = __task_pid_nr_ns(task, PIDTYPE_PID, common->ns);
	if (!next_tid)
		goto retry;

	if (skip_if_dup_files && task->files == task->group_leader->files)
		goto retry;

	*tid = common->pid_visiting = next_tid;
	get_task_struct(task);
	return task;
}

static struct task_struct *task_seq_get_next(struct bpf_iter_seq_task_common *common,
					     u32 *tid,
					     bool skip_if_dup_files)
{
	struct task_struct *task = NULL;
	struct pid *pid;

	if (common->type == BPF_TASK_ITER_TID) {
		if (*tid && *tid != common->pid)
			return NULL;
		rcu_read_lock();
		pid = find_pid_ns(common->pid, common->ns);
		if (pid) {
			task = get_pid_task(pid, PIDTYPE_PID);
			*tid = common->pid;
		}
		rcu_read_unlock();

		return task;
	}

	if (common->type == BPF_TASK_ITER_TGID) {

Annotation

Implementation Notes