Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> [Wed, 2019-12-18 21:50 -0800]:
> 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.
OK, will do both OPTS_VALID and OPTS_GET in v4.
>
>
> >
> > return sys_bpf(BPF_PROG_ATTACH, &attr, sizeof(attr));
> > }
>
> [...]
--
Andrey Ignatov
