On 09/11/2015 02:21 AM, Tycho Andersen wrote:
This commit adds a way to dump eBPF programs. The initial implementation
doesn't support maps, and therefore only allows dumping seccomp ebpf
programs which themselves don't currently support maps.

v2: don't export a prog_id for the filter

Signed-off-by: Tycho Andersen <[email protected]>
CC: Kees Cook <[email protected]>
CC: Will Drewry <[email protected]>
CC: Oleg Nesterov <[email protected]>
CC: Andy Lutomirski <[email protected]>
CC: Pavel Emelyanov <[email protected]>
CC: Serge E. Hallyn <[email protected]>
CC: Alexei Starovoitov <[email protected]>
CC: Daniel Borkmann <[email protected]>
[...]
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index dc9b464..58ae9f4 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -586,6 +586,44 @@ free_prog:
        return err;
  }

+static int bpf_prog_dump(union bpf_attr *attr, union bpf_attr __user *uattr)
+{
+       int ufd = attr->prog_fd;
+       struct fd f = fdget(ufd);
+       struct bpf_prog *prog;
+       int ret = -EINVAL;
+
+       prog = get_prog(f);
+       if (IS_ERR(prog))
+               return PTR_ERR(prog);
+
+       /* For now, let's refuse to dump anything that isn't a seccomp program.
+        * Other program types have support for maps, which our current dump
+        * code doesn't support.
+        */
+       if (prog->type != BPF_PROG_TYPE_SECCOMP)
+               goto out;

Yep, also when you start adding helper calls (next to map objects) you'd
need to undo kernel pointers that the verifier sets here.
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