On Wed, Dec 18, 2019 at 6:56 PM Andrey Ignatov <rdna@xxxxxx> wrote:
>
> Introduce a new bpf_prog_attach_xattr function that, in addition to
> program fd, target fd and attach type, accepts an extendable struct
> bpf_prog_attach_opts.
>
> bpf_prog_attach_opts relies on DECLARE_LIBBPF_OPTS macro to maintain
> backward and forward compatibility and has the following "optional"
> attach attributes:
>
> * existing attach_flags, since it's not required when attaching in NONE
> mode. Even though it's quite often used in MULTI and OVERRIDE mode it
> seems to be a good idea to reduce number of arguments to
> bpf_prog_attach_xattr;
>
> * newly introduced attribute of BPF_PROG_ATTACH command: replace_prog_fd
> that is fd of previously attached cgroup-bpf program to replace if
> BPF_F_REPLACE flag is used.
>
> The new function is named to be consistent with other xattr-functions
> (bpf_prog_test_run_xattr, bpf_create_map_xattr, bpf_load_program_xattr).
>
> The struct bpf_prog_attach_opts is supposed to be used with
> DECLARE_LIBBPF_OPTS macro.
>
> Signed-off-by: Andrey Ignatov <rdna@xxxxxx>
> ---
> tools/lib/bpf/bpf.c | 16 +++++++++++++++-
> tools/lib/bpf/bpf.h | 11 +++++++++++
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 98596e15390f..ebb4f8d71bdb 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -466,6 +466,17 @@ int bpf_obj_get(const char *pathname)
>
> int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type,
> unsigned int flags)
> +{
> + DECLARE_LIBBPF_OPTS(bpf_prog_attach_opts, opts,
> + .flags = flags,
> + );
> +
> + return bpf_prog_attach_xattr(prog_fd, target_fd, type, &opts);
> +}
> +
> +int bpf_prog_attach_xattr(int prog_fd, int target_fd,
> + enum bpf_attach_type type,
> + const struct bpf_prog_attach_opts *opts)
> {
> union bpf_attr attr;
>
You need to validate opts with OPTS_VALID macro (see
btf_dump__emit_type_decl() for simple example).
> @@ -473,7 +484,10 @@ int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type,
> attr.target_fd = target_fd;
> attr.attach_bpf_fd = prog_fd;
> attr.attach_type = type;
> - attr.attach_flags = flags;
> + if (opts) {
> + attr.attach_flags = opts->flags;
> + attr.replace_bpf_fd = opts->replace_prog_fd;
> + }
Please use OPTS_GET() macro to fetch values from opts struct and
provide default value if they are not specified.
>
> return sys_bpf(BPF_PROG_ATTACH, &attr, sizeof(attr));
> }
[...]
