netdev - [RFC net-next 1/2] bpf: Introduce bpf

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Date:   Wed, 26 Apr 2017 23:24:48 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     <netdev@...r.kernel.org>
CC:     Daniel Borkmann <daniel@...earbox.net>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Alexei Starovoitov <ast@...com>, <kernel-team@...com>
Subject: [RFC net-next 1/2] bpf: Introduce bpf_prog ID

The ID is generated by the existing idr_alloc_cyclic().

This patch also adds BPF_PROG_GET_NEXT_ID to allow userspace to iterate
all bpf_prog id(s).  The API is trying to be consistent with the
existing BPF_MAP_GET_NEXT_KEY.

Signed-off-by: Martin KaFai Lau <kafai@...com>
---
 include/linux/filter.h   |  1 +
 include/uapi/linux/bpf.h |  6 ++++++
 kernel/bpf/syscall.c     | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 9a7786db14fa..6eeeb83c4013 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -417,6 +417,7 @@ struct bpf_prog {
 	kmemcheck_bitfield_end(meta);
 	enum bpf_prog_type	type;		/* Type of BPF program */
 	u32			len;		/* Number of filter blocks */
+	u32			id;
 	u8			tag[BPF_TAG_SIZE];
 	struct bpf_prog_aux	*aux;		/* Auxiliary fields */
 	struct sock_fprog_kern	*orig_prog;	/* Original BPF program */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index e553529929f6..270f501c5597 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -82,6 +82,7 @@ enum bpf_cmd {
 	BPF_PROG_ATTACH,
 	BPF_PROG_DETACH,
 	BPF_PROG_TEST_RUN,
+	BPF_PROG_GET_NEXT_ID,
 };
 
 enum bpf_map_type {
@@ -201,6 +202,11 @@ union bpf_attr {
 		__u32		repeat;
 		__u32		duration;
 	} test;
+
+	struct { /* anonymous struct used by BPF_PROG_GET_NEXT_ID */
+		__u32		start_id;
+		__aligned_u64	next_id;
+	};
 } __attribute__((aligned(8)));
 
 /* BPF helper function descriptions:
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 13642c73dca0..6a654e17bd3c 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -22,8 +22,11 @@
 #include <linux/filter.h>
 #include <linux/version.h>
 #include <linux/kernel.h>
+#include <linux/idr.h>
 
 DEFINE_PER_CPU(int, bpf_prog_active);
+DEFINE_IDR(prog_idr);
+DEFINE_SPINLOCK(prog_idr_lock);
 
 int sysctl_unprivileged_bpf_disabled __read_mostly;
 
@@ -663,6 +666,9 @@ static void __bpf_prog_put_rcu(struct rcu_head *rcu)
 void bpf_prog_put(struct bpf_prog *prog)
 {
 	if (atomic_dec_and_test(&prog->aux->refcnt)) {
+		spin_lock(&prog_idr_lock);
+		idr_remove(&prog_idr, prog->id);
+		spin_unlock(&prog_idr_lock);
 		trace_bpf_prog_put_rcu(prog);
 		bpf_prog_kallsyms_del(prog);
 		call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu);
@@ -790,7 +796,7 @@ static int bpf_prog_load(union bpf_attr *attr)
 {
 	enum bpf_prog_type type = attr->prog_type;
 	struct bpf_prog *prog;
-	int err;
+	int err, id;
 	char license[128];
 	bool is_gpl;
 
@@ -848,6 +854,15 @@ static int bpf_prog_load(union bpf_attr *attr)
 	if (err < 0)
 		goto free_used_maps;
 
+	spin_lock(&prog_idr_lock);
+	id = idr_alloc_cyclic(&prog_idr, prog, 1, INT_MAX, GFP_USER);
+	spin_unlock(&prog_idr_lock);
+	if (id < 0) {
+		err = id;
+		goto free_used_maps;
+	}
+	prog->id = id;
+
 	/* eBPF program is ready to be JITed */
 	prog = bpf_prog_select_runtime(prog, &err);
 	if (err < 0)
@@ -995,6 +1010,33 @@ static int bpf_prog_test_run(const union bpf_attr *attr,
 	return ret;
 }
 
+#define BPF_PROG_GET_NEXT_ID_LAST_FIELD next_id
+
+static int bpf_prog_get_next_id(union bpf_attr *attr)
+{
+	u64 __user *unext_id = u64_to_user_ptr(attr->next_id);
+	u32 next_id = attr->start_id;
+	struct bpf_prog *prog;
+
+	if (CHECK_ATTR(BPF_PROG_GET_NEXT_ID))
+		return -EINVAL;
+
+	if (next_id++ >= INT_MAX)
+		return -EINVAL;
+
+	spin_lock(&prog_idr_lock);
+	prog = idr_get_next(&prog_idr, &next_id);
+	spin_unlock(&prog_idr_lock);
+
+	if (!prog)
+		return -ENOENT;
+
+	if (copy_to_user(unext_id, &next_id, sizeof(next_id)))
+		return -EFAULT;
+
+	return 0;
+}
+
 SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
 {
 	union bpf_attr attr = {};
@@ -1072,6 +1114,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
 	case BPF_PROG_TEST_RUN:
 		err = bpf_prog_test_run(&attr, uattr);
 		break;
+	case BPF_PROG_GET_NEXT_ID:
+		err = bpf_prog_get_next_id(&attr);
+		break;
 	default:
 		err = -EINVAL;
 		break;
-- 
2.9.3