From f0d74c4da1f060d2a66976193712a5e6abd361f5 Mon Sep 17 00:00:00 2001 From: Kui-Feng Lee Date: Mon, 26 Sep 2022 11:49:53 -0700 Subject: 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: Kui-Feng Lee Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20220926184957.208194-2-kuifeng@fb.com --- kernel/bpf/task_iter.c | 188 +++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 166 insertions(+), 22 deletions(-) (limited to 'kernel/bpf') diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 8c921799def4..8b2f47e7139d 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -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; @@ -151,21 +285,18 @@ again: 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(); @@ -186,9 +317,15 @@ again: /* 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 @@ again: 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 = { -- cgit v1.2.3