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SubjectRe: [PATCH v2 3/5] ebpf: add a way to dump an eBPF program
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 <tycho.andersen@canonical.com>
> CC: Kees Cook <keescook@chromium.org>
> CC: Will Drewry <wad@chromium.org>
> CC: Oleg Nesterov <oleg@redhat.com>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Pavel Emelyanov <xemul@parallels.com>
> CC: Serge E. Hallyn <serge.hallyn@ubuntu.com>
> CC: Alexei Starovoitov <ast@kernel.org>
> CC: Daniel Borkmann <daniel@iogearbox.net>
[...]
> 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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