[RFC PATCH bpf-next 11/16] bpf: implement query for target_proto and file dumper prog_id

Yonghong Song
2020-04-08T23:25:38Z

Given a fd representing a bpfdump target, user
can retrieve the target_proto name which represents
the bpf program prototype.

Given a fd representing a file dumper, user can
retrieve the bpf_prog id associated with that dumper.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 13 +++++++++
kernel/bpf/dump.c | 51 ++++++++++++++++++++++++++++++++++
kernel/bpf/syscall.c | 14 ++++++++++
tools/include/uapi/linux/bpf.h | 13 +++++++++
5 files changed, 92 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f7d4269d77b8..c9aec3b02dfa 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1120,6 +1120,7 @@ int bpf_dump_create(u32 prog_fd, const char __user *dumper_name);
struct bpf_prog *bpf_dump_get_prog(struct seq_file *seq, u32 priv_data_size,
u64 *seq_num);
int bpf_dump_run_prog(struct bpf_prog *prog, void *ctx);
+int bpf_dump_query(const union bpf_attr *attr, union bpf_attr __user *uattr);

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);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index a245f0df53c4..fc2157e319f1 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -113,6 +113,7 @@ enum bpf_cmd {
BPF_MAP_DELETE_BATCH,
BPF_LINK_CREATE,
BPF_LINK_UPDATE,
+ BPF_DUMP_QUERY,
};

enum bpf_map_type {
@@ -594,6 +595,18 @@ union bpf_attr {
__u32 old_prog_fd;
} link_update;

+ struct {
+ __u32 query_fd;
+ __u32 flags;
+ union {
+ struct {
+ __aligned_u64 target_proto;
+ __u32 proto_buf_len;
+ };
+ __u32 prog_id;
+ };
+ } dump_query;
+
} __attribute__((aligned(8)));

/* The description below is an attempt at providing documentation to eBPF
diff --git a/kernel/bpf/dump.c b/kernel/bpf/dump.c
index 4e009b2612c2..f3041b362057 100644
--- a/kernel/bpf/dump.c
+++ b/kernel/bpf/dump.c
@@ -86,6 +86,57 @@ static void *get_extra_priv_dptr(void *old_ptr, u32 old_size)
return old_ptr + roundup(old_size, 8);
}

+int bpf_dump_query(const union bpf_attr *attr, union bpf_attr __user *uattr)
+{
+ struct bpfdump_target_info *tinfo;
+ struct dumper_inode_info *i_info;
+ const char *target_proto;
+ void * __user proto_buf;
+ struct file *filp;
+ u32 proto_len;
+ struct fd qfd;
+ int err = 0;
+
+ if (attr->dump_query.flags != 0)
+ return -EINVAL;
+
+ qfd = fdget(attr->dump_query.query_fd);
+ filp = qfd.file;
+ if (!filp)
+ return -EBADF;
+
+ if (filp->f_op != &bpf_dumper_ops &&
+ filp->f_inode->i_op != &bpf_dir_iops) {
+ err = -EINVAL;
+ goto done;
+ }
+
+ if (filp->f_op == &bpf_dumper_ops) {
+ i_info = filp->f_inode->i_private;
+ if (put_user(i_info->prog->aux->id, &uattr->dump_query.prog_id))
+ err = -EFAULT;
+
+ goto done;
+ }
+
+ tinfo = filp->f_inode->i_private;
+ target_proto = tinfo->target_proto;
+
+ proto_len = strlen(target_proto) + 1;
+ if (attr->dump_query.proto_buf_len < proto_len) {
+ err = -ENOSPC;
+ goto done;
+ }
+
+ proto_buf = u64_to_user_ptr(attr->dump_query.target_proto);
+ if (copy_to_user(proto_buf, target_proto, proto_len))
+ err = -EFAULT;
+
+done:
+ fdput(qfd);
+ return err;
+}
+
#ifdef CONFIG_PROC_FS
static void dumper_show_fdinfo(struct seq_file *m, struct file *filp)
{
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 62a872a406ca..46b58f1f2d75 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3673,6 +3673,17 @@ static int link_update(union bpf_attr *attr)
return ret;
}

+#define BPF_DUMP_QUERY_LAST_FIELD dump_query.proto_buf_len
+
+static int bpf_dump_do_query(const union bpf_attr *attr,
+ union bpf_attr __user *uattr)
+{
+ if (CHECK_ATTR(BPF_DUMP_QUERY))
+ return -EINVAL;
+
+ return bpf_dump_query(attr, uattr);
+}
+
SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
{
union bpf_attr attr;
@@ -3790,6 +3801,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
case BPF_LINK_UPDATE:
err = link_update(&attr);
break;
+ case BPF_DUMP_QUERY:
+ err = bpf_dump_do_query(&attr, uattr);
+ break;
default:
err = -EINVAL;
break;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index a245f0df53c4..fc2157e319f1 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -113,6 +113,7 @@ enum bpf_cmd {
BPF_MAP_DELETE_BATCH,
BPF_LINK_CREATE,
BPF_LINK_UPDATE,
+ BPF_DUMP_QUERY,
};

enum bpf_map_type {
@@ -594,6 +595,18 @@ union bpf_attr {
__u32 old_prog_fd;
} link_update;

+ struct {
+ __u32 query_fd;
+ __u32 flags;
+ union {
+ struct {
+ __aligned_u64 target_proto;
+ __u32 proto_buf_len;
+ };
+ __u32 prog_id;
+ };
+ } dump_query;
+
} __attribute__((aligned(8)));

/* The description below is an attempt at providing documentation to eBPF
--
2.24.1