[PATCH bpf-next v3 09/21] bpf: add bpf_map iterator

Yonghong Song
2020-05-07T05:40:22Z

Implement seq_file operations to traverse all maps.

Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
include/linux/bpf.h | 1 +
kernel/bpf/Makefile | 2 +-
kernel/bpf/map_iter.c | 97 +++++++++++++++++++++++++++++++++++++++++++
kernel/bpf/syscall.c | 19 +++++++++
4 files changed, 118 insertions(+), 1 deletion(-)
create mode 100644 kernel/bpf/map_iter.c

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index ffe0b9b669bf..363ab0751967 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1082,6 +1082,7 @@ int generic_map_update_batch(struct bpf_map *map,
int generic_map_delete_batch(struct bpf_map *map,
const union bpf_attr *attr,
union bpf_attr __user *uattr);
+struct bpf_map *bpf_map_get_curr_or_next(u32 *id);

extern int sysctl_unprivileged_bpf_disabled;

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 6a8b0febd3f6..b2b5eefc5254 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-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o
+obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_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/map_iter.c b/kernel/bpf/map_iter.c
new file mode 100644
index 000000000000..8162e0c00b9f
--- /dev/null
+++ b/kernel/bpf/map_iter.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2020 Facebook */
+#include <linux/bpf.h>
+#include <linux/fs.h>
+#include <linux/filter.h>
+#include <linux/kernel.h>
+
+struct bpf_iter_seq_map_info {
+ u32 mid;
+};
+
+static void *bpf_map_seq_start(struct seq_file *seq, loff_t *pos)
+{
+ struct bpf_iter_seq_map_info *info = seq->private;
+ struct bpf_map *map;
+
+ map = bpf_map_get_curr_or_next(&info->mid);
+ if (!map)
+ return NULL;
+
+ ++*pos;
+ return map;
+}
+
+static void *bpf_map_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+ struct bpf_iter_seq_map_info *info = seq->private;
+ struct bpf_map *map;
+
+ ++*pos;
+ ++info->mid;
+ bpf_map_put((struct bpf_map *)v);
+ map = bpf_map_get_curr_or_next(&info->mid);
+ if (!map)
+ return NULL;
+
+ return map;
+}
+
+struct bpf_iter__bpf_map {
+ __bpf_md_ptr(struct bpf_iter_meta *, meta);
+ __bpf_md_ptr(struct bpf_map *, map);
+};
+
+DEFINE_BPF_ITER_FUNC(bpf_map, struct bpf_iter_meta *meta, struct bpf_map *map)
+
+static int __bpf_map_seq_show(struct seq_file *seq, void *v, bool in_stop)
+{
+ struct bpf_iter__bpf_map ctx;
+ struct bpf_iter_meta meta;
+ struct bpf_prog *prog;
+ int ret = 0;
+
+ ctx.meta = &meta;
+ ctx.map = v;
+ meta.seq = seq;
+ prog = bpf_iter_get_info(&meta, in_stop);
+ if (prog)
+ ret = bpf_iter_run_prog(prog, &ctx);
+
+ return ret;
+}
+
+static int bpf_map_seq_show(struct seq_file *seq, void *v)
+{
+ return __bpf_map_seq_show(seq, v, false);
+}
+
+static void bpf_map_seq_stop(struct seq_file *seq, void *v)
+{
+ if (!v)
+ (void)__bpf_map_seq_show(seq, v, true);
+ else
+ bpf_map_put((struct bpf_map *)v);
+}
+
+static const struct seq_operations bpf_map_seq_ops = {
+ .start = bpf_map_seq_start,
+ .next = bpf_map_seq_next,
+ .stop = bpf_map_seq_stop,
+ .show = bpf_map_seq_show,
+};
+
+static int __init bpf_map_iter_init(void)
+{
+ struct bpf_iter_reg reg_info = {
+ .target = "bpf_map",
+ .seq_ops = &bpf_map_seq_ops,
+ .init_seq_private = NULL,
+ .fini_seq_private = NULL,
+ .seq_priv_size = sizeof(struct bpf_iter_seq_map_info),
+ };
+
+ return bpf_iter_reg_target(&reg_info);
+}
+
+late_initcall(bpf_map_iter_init);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a293e88ee01a..de2a75500233 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2934,6 +2934,25 @@ static int bpf_obj_get_next_id(const union bpf_attr *attr,
return err;
}

+struct bpf_map *bpf_map_get_curr_or_next(u32 *id)
+{
+ struct bpf_map *map;
+
+ spin_lock_bh(&map_idr_lock);
+again:
+ map = idr_get_next(&map_idr, id);
+ if (map) {
+ map = __bpf_map_inc_not_zero(map, false);
+ if (IS_ERR(map)) {
+ (*id)++;
+ goto again;
+ }
+ }
+ spin_unlock_bh(&map_idr_lock);
+
+ return map;
+}
+
#define BPF_PROG_GET_FD_BY_ID_LAST_FIELD prog_id

struct bpf_prog *bpf_prog_by_id(u32 id)
--
2.24.1