[RFC PATCH v2 bpf-next 03/15] bpf: Add API to get program from id

[Toshiaki Makita <toshiaki.makita1@gmail.com>]

Factor out the logic in bpf_prog_get_fd_by_id() and add
bpf_prog_get_by_id()/bpf_prog_get_type_dev_by_id().
Also export bpf_prog_get_type_dev_by_id(), which will be used by the
following commit to get bpf prog from its id.

Signed-off-by: Toshiaki Makita <toshiaki.makita1@gmail.com>
---
 include/linux/bpf.h  |  8 ++++++++
 kernel/bpf/syscall.c | 42 ++++++++++++++++++++++++++++++++++--------
 2 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 282e28b..78fe7ef 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -636,6 +636,8 @@ int bpf_prog_array_copy(struct bpf_prog_array *old_array,
 struct bpf_prog *bpf_prog_get(u32 ufd);
 struct bpf_prog *bpf_prog_get_type_dev(u32 ufd, enum bpf_prog_type type,
 				       bool attach_drv);
+struct bpf_prog *bpf_prog_get_type_dev_by_id(u32 id, enum bpf_prog_type type,
+					     bool attach_drv);
 struct bpf_prog * __must_check bpf_prog_add(struct bpf_prog *prog, int i);
 void bpf_prog_sub(struct bpf_prog *prog, int i);
 struct bpf_prog * __must_check bpf_prog_inc(struct bpf_prog *prog);
@@ -760,6 +762,12 @@ static inline struct bpf_prog *bpf_prog_get_type_dev(u32 ufd,
 	return ERR_PTR(-EOPNOTSUPP);
 }
 
+static inline struct bpf_prog *
+bpf_prog_get_type_dev_by_id(u32 id, enum bpf_prog_type type, bool attach_drv)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
 static inline struct bpf_prog * __must_check bpf_prog_add(struct bpf_prog *prog,
 							  int i)
 {
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 82eabd4..2dd6cfc 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2139,6 +2139,39 @@ static int bpf_obj_get_next_id(const union bpf_attr *attr,
 	return err;
 }
 
+static struct bpf_prog *bpf_prog_get_by_id(u32 id)
+{
+	struct bpf_prog *prog;
+
+	spin_lock_bh(&prog_idr_lock);
+	prog = idr_find(&prog_idr, id);
+	if (prog)
+		prog = bpf_prog_inc_not_zero(prog);
+	else
+		prog = ERR_PTR(-ENOENT);
+	spin_unlock_bh(&prog_idr_lock);
+
+	return prog;
+}
+
+struct bpf_prog *bpf_prog_get_type_dev_by_id(u32 id, enum bpf_prog_type type,
+					     bool attach_drv)
+{
+	struct bpf_prog *prog;
+
+	prog = bpf_prog_get_by_id(id);
+	if (IS_ERR(prog))
+		return prog;
+
+	if (!bpf_prog_get_ok(prog, &type, attach_drv)) {
+		bpf_prog_put(prog);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return prog;
+}
+EXPORT_SYMBOL_GPL(bpf_prog_get_type_dev_by_id);
+
 #define BPF_PROG_GET_FD_BY_ID_LAST_FIELD prog_id
 
 static int bpf_prog_get_fd_by_id(const union bpf_attr *attr)
@@ -2153,14 +2186,7 @@ static int bpf_prog_get_fd_by_id(const union bpf_attr *attr)
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	spin_lock_bh(&prog_idr_lock);
-	prog = idr_find(&prog_idr, id);
-	if (prog)
-		prog = bpf_prog_inc_not_zero(prog);
-	else
-		prog = ERR_PTR(-ENOENT);
-	spin_unlock_bh(&prog_idr_lock);
-
+	prog = bpf_prog_get_by_id(id);
 	if (IS_ERR(prog))
 		return PTR_ERR(prog);
 
-- 
1.8.3.1