[PATCH bpf-next v1 02/19] bpf: implement an interface to register bpf_iter targets

Yonghong Song
2020-04-27T20:12:45Z

The target can call bpf_iter_reg_target() to register itself.
The needed information:
target: target name, reprsented as a directory hierarchy
target_func_name: the kernel func name used by verifier to
verify bpf programs
seq_ops: the seq_file operations for the target
seq_priv_size: the private_data size needed by the seq_file
operations
target_feature: certain feature requested by the target for
bpf_iter to prepare for seq_file operations.

A little bit more explanations on the target name and target_feature.
For example, the target name can be "bpf_map", "task", "task/file",
which represents iterating all bpf_map's, all tasks, or all files
of all tasks.

The target feature is mostly for reusing existing seq_file operations.
For example, /proc/net/{tcp6, ipv6_route, netlink, ...} seq_file private
data contains a reference to net namespace. When bpf_iter tries to
reuse the same seq_ops, its seq_file private data need the net namespace
setup properly too. In this case, the bpf_iter infrastructure can help
set up properly before doing seq_file operations.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
include/linux/bpf.h | 11 ++++++++++
kernel/bpf/Makefile | 2 +-
kernel/bpf/bpf_iter.c | 50 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 62 insertions(+), 1 deletion(-)
create mode 100644 kernel/bpf/bpf_iter.c

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 10960cfabea4..5e56abc1e2f1 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -31,6 +31,7 @@ struct seq_file;
struct btf;
struct btf_type;
struct exception_table_entry;
+struct seq_operations;

extern struct idr btf_idr;
extern spinlock_t btf_idr_lock;
@@ -1109,6 +1110,16 @@ struct bpf_link *bpf_link_get_from_fd(u32 ufd);
int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
int bpf_obj_get_user(const char __user *pathname, int flags);

+struct bpf_iter_reg {
+ const char *target;
+ const char *target_func_name;
+ const struct seq_operations *seq_ops;
+ u32 seq_priv_size;
+ u32 target_feature;
+};
+
+int bpf_iter_reg_target(struct bpf_iter_reg *reg_info);
+
int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index f2d7be596966..6a8b0febd3f6 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -2,7 +2,7 @@
obj-y := core.o
CFLAGS_core.o += $(call cc-disable-warning, override-init)

-obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o
+obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o
obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o
obj-$(CONFIG_BPF_SYSCALL) += disasm.o
diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
new file mode 100644
index 000000000000..1115b978607a
--- /dev/null
+++ b/kernel/bpf/bpf_iter.c
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2020 Facebook */
+
+#include <linux/fs.h>
+#include <linux/filter.h>
+#include <linux/bpf.h>
+
+struct bpf_iter_target_info {
+ struct list_head list;
+ const char *target;
+ const char *target_func_name;
+ const struct seq_operations *seq_ops;
+ u32 seq_priv_size;
+ u32 target_feature;
+};
+
+static struct list_head targets;
+static struct mutex targets_mutex;
+static bool bpf_iter_inited = false;
+
+int bpf_iter_reg_target(struct bpf_iter_reg *reg_info)
+{
+ struct bpf_iter_target_info *tinfo;
+
+ /* The earliest bpf_iter_reg_target() is called at init time
+ * where the bpf_iter registration is serialized.
+ */
+ if (!bpf_iter_inited) {
+ INIT_LIST_HEAD(&targets);
+ mutex_init(&targets_mutex);
+ bpf_iter_inited = true;
+ }
+
+ tinfo = kmalloc(sizeof(*tinfo), GFP_KERNEL);
+ if (!tinfo)
+ return -ENOMEM;
+
+ tinfo->target = reg_info->target;
+ tinfo->target_func_name = reg_info->target_func_name;
+ tinfo->seq_ops = reg_info->seq_ops;
+ tinfo->seq_priv_size = reg_info->seq_priv_size;
+ tinfo->target_feature = reg_info->target_feature;
+ INIT_LIST_HEAD(&tinfo->list);
+
+ mutex_lock(&targets_mutex);
+ list_add(&tinfo->list, &targets);
+ mutex_unlock(&targets_mutex);
+
+ return 0;
+}
--
2.24.1