Merge branch 'Parameterize task iterators.'

Kui-Feng Lee says:

====================

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

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.

Major Changes:

 - Add new parameters in bpf_iter_link_info to indicate to go through
   all tasks or to go through a specific task.

 - Change the implementations of BPF iterators of vma, files, and
   tasks to allow going through only the resources of a specific task.

 - Provide the arguments of parameterized task iterators in
   bpf_link_info.

Differences from v10:

 - Check pid_alive() to avoid potential errors.

Differences from v9:

  - Fix the boundary check of computing page_shift.

  - Rewording the reason of checking and returning the same task.

Differences from v8:

 - Fix uninitialized variable.

 - Avoid redundant work of getting task from pid.

 - Change format string to use %u instead of %d.

 - Use the value of page_shift to compute correct offset in
   bpf_iter_vm_offset.c.

Differences from v7:

 - Travel the tasks of a process through task_group linked list
   instead of traveling through the whole namespace.

Differences from v6:

 - Add part 5 to make bpftool show the value of parameters.

 - Change of wording of show_fdinfo() to show pid or tid instead of
   always pid.

 - Simplify error handling and naming of test cases.

Differences from v5:

 - Use user-space tid/pid terminologies in bpf_iter_link_info and
   bpf_link_info.

 - Fix reference count

 - Merge all variants to one 'u32 pid' in internal structs.
   (bpf_iter_aux_info and bpf_iter_seq_task_common)

 - Compare the result of get_uprobe_offset() with the implementation
   with the vma iterators.

 - Implement show_fdinfo.

Differences from v4:

 - Remove 'type' from bpf_iter_link_info and bpf_link_info.

v10: https://lore.kernel.org/all/20220831181039.2680134-1-kuifeng@fb.com/
v9: https://lore.kernel.org/bpf/20220829192317.486946-1-kuifeng@fb.com/
v8: https://lore.kernel.org/bpf/20220829192317.486946-1-kuifeng@fb.com/
v7: https://lore.kernel.org/bpf/20220826003712.2810158-1-kuifeng@fb.com/
v6: https://lore.kernel.org/bpf/20220819220927.3409575-1-kuifeng@fb.com/
v5: https://lore.kernel.org/bpf/20220811001654.1316689-1-kuifeng@fb.com/
v4: https://lore.kernel.org/bpf/20220809195429.1043220-1-kuifeng@fb.com/
v3: https://lore.kernel.org/bpf/20220809063501.667610-1-kuifeng@fb.com/
v2: https://lore.kernel.org/bpf/20220801232649.2306614-1-kuifeng@fb.com/
v1: https://lore.kernel.org/bpf/20220726051713.840431-1-kuifeng@fb.com/
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

2 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5161fac0513f..0f3eaf3ed98c 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -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,
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index d6bd10759eaf..3075018a4ef8 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. */
@@ -6259,6 +6265,10 @@ struct bpf_link_info {
 					__u64 cgroup_id;
 					__u32 order;
 				} cgroup;
+				struct {
+					__u32 tid;
+					__u32 pid;
+				} task;
 			};
 		} iter;
 		struct  {