On Fri, 2022-08-26 at 12:30 -0700, Yonghong Song wrote:
>
>
> On 8/25/22 5:37 PM, Kui-Feng Lee wrote:
> > 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 <kuifeng@xxxxxx>
> > Acked-by: Yonghong Song <yhs@xxxxxx>
> > ---
> > include/linux/bpf.h | 25 +++++++
> > include/uapi/linux/bpf.h | 6 ++
> > kernel/bpf/task_iter.c | 128 ++++++++++++++++++++++++++--
> > -----
> > tools/include/uapi/linux/bpf.h | 6 ++
> > 4 files changed, 141 insertions(+), 24 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 9c1674973e03..31ac2c1181f5 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -1730,6 +1730,27 @@ 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;
> > @@ -1739,6 +1760,10 @@ 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,
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 0f61f09f467a..385deab984e1 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -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. */
> > diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
> > index 8c921799def4..1200cfde71e3 100644
> > --- a/kernel/bpf/task_iter.c
> > +++ b/kernel/bpf/task_iter.c
> > @@ -12,6 +12,8 @@
> >
> > struct bpf_iter_seq_task_common {
> > struct pid_namespace *ns;
> > + enum bpf_iter_task_type type;
> > + u32 pid;
> > };
> >
> > struct bpf_iter_seq_task_info {
> > @@ -22,24 +24,54 @@ struct bpf_iter_seq_task_info {
> > u32 tid;
> > };
> >
> > -static struct task_struct *task_seq_get_next(struct pid_namespace
> > *ns,
> > +static bool matched_task(struct task_struct *task,
> > + struct bpf_iter_seq_task_common *common,
> > + bool skip_if_dup_file)
> > +{
> > + /* Should not have the same 'files' if skip_if_dup_file is
> > true */
> > + bool diff_files_if =
> > + !skip_if_dup_file ||
> > + (thread_group_leader(task) &&
> > + task->files != task->group_leader->files);
>
> Should this be
> !skip_if_dup_file || thread_group_leader(task) ||
> task->files != task->group_leader->files
> ?
Good catch!
This change will be rollbacked by using next_thread().
>
> > + /* Should have the given tgid if the type is
> > BPF_TASK_ITER_TGI */
>
> BPF_TASK_ITER_TGID?
>
> > + bool have_tgid_if =
> > + common->type != BPF_TASK_ITER_TGID ||
> > + __task_pid_nr_ns(task, PIDTYPE_TGID,
> > + common->ns) == common->pid;
> > + return diff_files_if && have_tgid_if;
> > +}
> > +
> > +
> > +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;
> > + }
> > +
> > 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;
> > goto retry;
> > - } else if (skip_if_dup_files &&
> > !thread_group_leader(task) &&
> > - task->files == task->group_leader-
> > >files) {
> > + } else if (!matched_task(task, common,
> > skip_if_dup_files)) {
> > put_task_struct(task);
> > task = NULL;
> > ++*tid;
> > @@ -56,7 +88,7 @@ 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;
> >
> [...]
