[PATCH bpf-next v2 3/6] bpf: Introduce process open coded iterator kfuncs

Chuyi Zhou
2023-09-12T07:02:10Z

This patch adds kfuncs bpf_iter_process_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_process in open-coded iterator
style. BPF programs can use these kfuncs or through bpf_for_each macro to
iterate all processes in the system.

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
---
include/uapi/linux/bpf.h | 4 ++++
kernel/bpf/helpers.c | 3 +++
kernel/bpf/task_iter.c | 29 +++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 4 ++++
tools/lib/bpf/bpf_helpers.h | 5 +++++
5 files changed, 45 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index de02c0971428..befa55b52e29 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -7322,4 +7322,8 @@ struct bpf_iter_css_task {
__u64 __opaque[1];
} __attribute__((aligned(8)));

+struct bpf_iter_process {
+ __u64 __opaque[1];
+} __attribute__((aligned(8)));
+
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index d6a16becfbb9..9b7d2c6f99d1 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2507,6 +2507,9 @@ BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_iter_css_task_new, KF_ITER_NEW)
BTF_ID_FLAGS(func, bpf_iter_css_task_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_css_task_destroy, KF_ITER_DESTROY)
+BTF_ID_FLAGS(func, bpf_iter_process_new, KF_ITER_NEW)
+BTF_ID_FLAGS(func, bpf_iter_process_next, KF_ITER_NEXT | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_iter_process_destroy, KF_ITER_DESTROY)
BTF_ID_FLAGS(func, bpf_dynptr_adjust)
BTF_ID_FLAGS(func, bpf_dynptr_is_null)
BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index d8539cc05ffd..9d1927dc3a06 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -851,6 +851,35 @@ __bpf_kfunc void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it)
kfree(kit->css_it);
}

+struct bpf_iter_process_kern {
+ struct task_struct *tsk;
+} __attribute__((aligned(8)));
+
+__bpf_kfunc int bpf_iter_process_new(struct bpf_iter_process *it)
+{
+ struct bpf_iter_process_kern *kit = (void *)it;
+
+ BUILD_BUG_ON(sizeof(struct bpf_iter_process_kern) != sizeof(struct bpf_iter_process));
+ BUILD_BUG_ON(__alignof__(struct bpf_iter_process_kern) !=
+ __alignof__(struct bpf_iter_process));
+
+ kit->tsk = &init_task;
+ return 0;
+}
+
+__bpf_kfunc struct task_struct *bpf_iter_process_next(struct bpf_iter_process *it)
+{
+ struct bpf_iter_process_kern *kit = (void *)it;
+
+ kit->tsk = next_task(kit->tsk);
+
+ return kit->tsk == &init_task ? NULL : kit->tsk;
+}
+
+__bpf_kfunc void bpf_iter_process_destroy(struct bpf_iter_process *it)
+{
+}
+
DEFINE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work);

static void do_mmap_read_unlock(struct irq_work *entry)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index de02c0971428..befa55b52e29 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -7322,4 +7322,8 @@ struct bpf_iter_css_task {
__u64 __opaque[1];
} __attribute__((aligned(8)));

+struct bpf_iter_process {
+ __u64 __opaque[1];
+} __attribute__((aligned(8)));
+
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index f48723c6c593..858252c2641c 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -310,6 +310,11 @@ extern int bpf_iter_css_task_new(struct bpf_iter_css_task *it,
extern struct task_struct *bpf_iter_css_task_next(struct bpf_iter_css_task *it) __weak __ksym;
extern void bpf_iter_css_task_destroy(struct bpf_iter_css_task *it) __weak __ksym;

+struct bpf_iter_process;
+extern int bpf_iter_process_new(struct bpf_iter_process *it) __weak __ksym;
+extern struct task_struct *bpf_iter_process_next(struct bpf_iter_process *it) __weak __ksym;
+extern void bpf_iter_process_destroy(struct bpf_iter_process *it) __weak __ksym;
+
#ifndef bpf_for_each
/* bpf_for_each(iter_type, cur_elem, args...) provides generic construct for
* using BPF open-coded iterators without having to write mundane explicit
--
2.20.1