Commit f0d74c4d authored by Kui-Feng Lee's avatar Kui-Feng Lee Committed by Andrii Nakryiko
Browse files

bpf: Parameterize task iterators. 



Allow creating an iterator that loops through resources of one
thread/process.

People could only create iterators to loop through all resources of
files, vma, and tasks in the system, even though they were interested
in only the resources of a specific task or process.  Passing the
additional parameters, people can now create an iterator to go
through all resources or only the resources of a task.

Signed-off-by: default avatarKui-Feng Lee <kuifeng@fb.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Acked-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/bpf/20220926184957.208194-2-kuifeng@fb.com
parent 87dbdc23

include/linux/bpf.h

+25 −0
Original line number Diff line number Diff line
@@ -1796,6 +1796,27 @@ int bpf_obj_get_user(const char __user *pathname, int flags); 
	extern int bpf_iter_ ## target(args);			\

	int __init bpf_iter_ ## target(args) { return 0; }



/*

 * The task type of iterators.

 *

 * For BPF task iterators, they can be parameterized with various

 * parameters to visit only some of tasks.

 *

 * BPF_TASK_ITER_ALL (default)

 *	Iterate over resources of every task.

 *

 * BPF_TASK_ITER_TID

 *	Iterate over resources of a task/tid.

 *

 * BPF_TASK_ITER_TGID

 *	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,

};



struct bpf_iter_aux_info {

	/* for map_elem iter */

	struct bpf_map *map;
@@ -1805,6 +1826,10 @@ struct bpf_iter_aux_info { 
		struct cgroup *start; /* starting cgroup */

		enum bpf_cgroup_iter_order order;

	} cgroup;

	struct {

		enum bpf_iter_task_type	type;

		u32 pid;

	} task;

};



typedef int (*bpf_iter_attach_target_t)(struct bpf_prog *prog,

include/uapi/linux/bpf.h

+6 −0
Original line number Diff line number Diff line
@@ -110,6 +110,12 @@ union bpf_iter_link_info { 
		__u32	cgroup_fd;

		__u64	cgroup_id;

	} cgroup;

	/* Parameters of task iterators. */

	struct {

		__u32	tid;

		__u32	pid;

		__u32	pid_fd;

	} task;

};



/* BPF syscall commands, see bpf(2) man-page for more details. */

kernel/bpf/task_iter.c

+166 −22
Original line number Diff line number Diff line
@@ -12,6 +12,9 @@ 


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 {
@@ -22,18 +25,115 @@ struct bpf_iter_seq_task_info { 
	u32 tid;

};



static struct task_struct *task_seq_get_next(struct pid_namespace *ns,

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, *next_task;

	struct pid *pid;

	u32 saved_tid;



	if (!*tid) {

		/* The first time, the iterator calls this function. */

		pid = find_pid_ns(common->pid, common->ns);

		if (!pid)

			return NULL;



		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;

	}



	pid = find_pid_ns(common->pid_visiting, common->ns);

	if (!pid)

		return NULL;



	task = get_pid_task(pid, PIDTYPE_PID);

	if (!task)

		return NULL;



retry:

	if (!pid_alive(task)) {

		put_task_struct(task);

		return NULL;

	}



	next_task = next_thread(task);

	put_task_struct(task);

	if (!next_task)

		return NULL;



	saved_tid = *tid;

	*tid = __task_pid_nr_ns(next_task, PIDTYPE_PID, common->ns);

	if (!*tid || *tid == common->pid) {

		/* Run out of tasks of a process.  The tasks of a

		 * thread_group are linked as circular linked list.

		 */

		*tid = saved_tid;

		return NULL;

	}



	get_task_struct(next_task);

	common->pid_visiting = *tid;



	if (skip_if_dup_files && task->files == task->group_leader->files) {

		task = next_task;

		goto retry;

	}



	return next_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_TGID);

			*tid = common->pid;

		}

		rcu_read_unlock();



		return task;

	}



	if (common->type == BPF_TASK_ITER_TGID) {

		rcu_read_lock();

		task = task_group_seq_get_next(common, tid, skip_if_dup_files);

		rcu_read_unlock();



		return task;

	}



	rcu_read_lock();

retry:

	pid = find_ge_pid(*tid, ns);

	pid = find_ge_pid(*tid, common->ns);

	if (pid) {

		*tid = pid_nr_ns(pid, ns);

		*tid = pid_nr_ns(pid, common->ns);

		task = get_pid_task(pid, PIDTYPE_PID);

		if (!task) {

			++*tid;
@@ -56,7 +156,7 @@ static void *task_seq_start(struct seq_file *seq, loff_t *pos) 
	struct bpf_iter_seq_task_info *info = seq->private;

	struct task_struct *task;



	task = task_seq_get_next(info->common.ns, &info->tid, false);

	task = task_seq_get_next(&info->common, &info->tid, false);

	if (!task)

		return NULL;
@@ -73,7 +173,7 @@ static void *task_seq_next(struct seq_file *seq, void *v, loff_t *pos) 
	++*pos;

	++info->tid;

	put_task_struct((struct task_struct *)v);

	task = task_seq_get_next(info->common.ns, &info->tid, false);

	task = task_seq_get_next(&info->common, &info->tid, false);

	if (!task)

		return NULL;
@@ -117,6 +217,41 @@ static void task_seq_stop(struct seq_file *seq, void *v) 
		put_task_struct((struct task_struct *)v);

}



static int bpf_iter_attach_task(struct bpf_prog *prog,

				union bpf_iter_link_info *linfo,

				struct bpf_iter_aux_info *aux)

{

	unsigned int flags;

	struct pid *pid;

	pid_t tgid;



	if ((!!linfo->task.tid + !!linfo->task.pid + !!linfo->task.pid_fd) > 1)

		return -EINVAL;



	aux->task.type = BPF_TASK_ITER_ALL;

	if (linfo->task.tid != 0) {

		aux->task.type = BPF_TASK_ITER_TID;

		aux->task.pid = linfo->task.tid;

	}

	if (linfo->task.pid != 0) {

		aux->task.type = BPF_TASK_ITER_TGID;

		aux->task.pid = linfo->task.pid;

	}

	if (linfo->task.pid_fd != 0) {

		aux->task.type = BPF_TASK_ITER_TGID;



		pid = pidfd_get_pid(linfo->task.pid_fd, &flags);

		if (IS_ERR(pid))

			return PTR_ERR(pid);



		tgid = pid_nr_ns(pid, task_active_pid_ns(current));

		aux->task.pid = tgid;

		put_pid(pid);

	}



	return 0;

}



static const struct seq_operations task_seq_ops = {

	.start	= task_seq_start,

	.next	= task_seq_next,
@@ -137,8 +272,7 @@ struct bpf_iter_seq_task_file_info { 
static struct file *

task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info)

{

	struct pid_namespace *ns = info->common.ns;

	u32 curr_tid = info->tid;

	u32 saved_tid = info->tid;

	struct task_struct *curr_task;

	unsigned int curr_fd = info->fd;
@@ -151,22 +285,19 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info) 
		curr_task = info->task;

		curr_fd = info->fd;

	} else {

                curr_task = task_seq_get_next(ns, &curr_tid, true);

		curr_task = task_seq_get_next(&info->common, &info->tid, true);

                if (!curr_task) {

                        info->task = NULL;

                        info->tid = curr_tid;

                        return NULL;

                }



                /* set info->task and info->tid */

		/* set info->task */

		info->task = curr_task;

		if (curr_tid == info->tid) {

		if (saved_tid == info->tid)

			curr_fd = info->fd;

		} else {

			info->tid = curr_tid;

		else

			curr_fd = 0;

	}

	}



	rcu_read_lock();

	for (;; curr_fd++) {
@@ -186,9 +317,15 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info) 
	/* the current task is done, go to the next task */

	rcu_read_unlock();

	put_task_struct(curr_task);



	if (info->common.type == BPF_TASK_ITER_TID) {

		info->task = NULL;

		return NULL;

	}



	info->task = NULL;

	info->fd = 0;

	curr_tid = ++(info->tid);

	saved_tid = ++(info->tid);

	goto again;

}
@@ -269,6 +406,9 @@ static int init_seq_pidns(void *priv_data, struct bpf_iter_aux_info *aux) 
	struct bpf_iter_seq_task_common *common = priv_data;



	common->ns = get_pid_ns(task_active_pid_ns(current));

	common->type = aux->task.type;

	common->pid = aux->task.pid;



	return 0;

}
@@ -307,11 +447,10 @@ enum bpf_task_vma_iter_find_op { 
static struct vm_area_struct *

task_vma_seq_get_next(struct bpf_iter_seq_task_vma_info *info)

{

	struct pid_namespace *ns = info->common.ns;

	enum bpf_task_vma_iter_find_op op;

	struct vm_area_struct *curr_vma;

	struct task_struct *curr_task;

	u32 curr_tid = info->tid;

	u32 saved_tid = info->tid;



	/* If this function returns a non-NULL vma, it holds a reference to

	 * the task_struct, and holds read lock on vma->mm->mmap_lock.
@@ -371,14 +510,13 @@ task_vma_seq_get_next(struct bpf_iter_seq_task_vma_info *info) 
		}

	} else {

again:

		curr_task = task_seq_get_next(ns, &curr_tid, true);

		curr_task = task_seq_get_next(&info->common, &info->tid, true);

		if (!curr_task) {

			info->tid = curr_tid + 1;

			info->tid++;

			goto finish;

		}



		if (curr_tid != info->tid) {

			info->tid = curr_tid;

		if (saved_tid != info->tid) {

			/* new task, process the first vma */

			op = task_vma_iter_first_vma;

		} else {
@@ -430,9 +568,12 @@ 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)

		goto finish;



	put_task_struct(curr_task);

	info->task = NULL;

	curr_tid++;

	info->tid++;

	goto again;



finish:
@@ -533,6 +674,7 @@ static const struct bpf_iter_seq_info task_seq_info = { 


static struct bpf_iter_reg task_reg_info = {

	.target			= "task",

	.attach_target		= bpf_iter_attach_task,

	.feature		= BPF_ITER_RESCHED,

	.ctx_arg_info_size	= 1,

	.ctx_arg_info		= {
@@ -551,6 +693,7 @@ static const struct bpf_iter_seq_info task_file_seq_info = { 


static struct bpf_iter_reg task_file_reg_info = {

	.target			= "task_file",

	.attach_target		= bpf_iter_attach_task,

	.feature		= BPF_ITER_RESCHED,

	.ctx_arg_info_size	= 2,

	.ctx_arg_info		= {
@@ -571,6 +714,7 @@ static const struct bpf_iter_seq_info task_vma_seq_info = { 


static struct bpf_iter_reg task_vma_reg_info = {

	.target			= "task_vma",

	.attach_target		= bpf_iter_attach_task,

	.feature		= BPF_ITER_RESCHED,

	.ctx_arg_info_size	= 2,

	.ctx_arg_info		= {

tools/include/uapi/linux/bpf.h

+6 −0
Original line number Diff line number Diff line
@@ -110,6 +110,12 @@ union bpf_iter_link_info { 
		__u32	cgroup_fd;

		__u64	cgroup_id;

	} cgroup;

	/* Parameters of task iterators. */

	struct {

		__u32	tid;

		__u32	pid;

		__u32	pid_fd;

	} task;

};



/* BPF syscall commands, see bpf(2) man-page for more details. */