Re: [PATCH bpf-next v5 6/7] tools/libbpf: Add support for BPF_PROG_TYPE_LSM

KP Singh
2020-03-24T01:57:49Z

On 23-Mär 13:25, Andrii Nakryiko wrote:
> On Mon, Mar 23, 2020 at 9:45 AM KP Singh <kpsingh@chromium.org> wrote:
> >
> > From: KP Singh <kpsingh@google.com>
> >
> > Since BPF_PROG_TYPE_LSM uses the same attaching mechanism as
> > BPF_PROG_TYPE_TRACING, the common logic is refactored into a static
> > function bpf_program__attach_btf.
> >
> > A new API call bpf_program__attach_lsm is still added to avoid userspace
> > conflicts if this ever changes in the future.
> >
> > Signed-off-by: KP Singh <kpsingh@google.com>
> > Reviewed-by: Brendan Jackman <jackmanb@google.com>
> > Reviewed-by: Florent Revest <revest@google.com>
> > ---
> > tools/lib/bpf/bpf.c | 3 ++-
> > tools/lib/bpf/libbpf.c | 41 +++++++++++++++++++++++++++++++++++-----
> > tools/lib/bpf/libbpf.h | 4 ++++
> > tools/lib/bpf/libbpf.map | 3 +++
> > 4 files changed, 45 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> > index c6dafe563176..73220176728d 100644
> > --- a/tools/lib/bpf/bpf.c
> > +++ b/tools/lib/bpf/bpf.c
> > @@ -235,7 +235,8 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
> > memset(&attr, 0, sizeof(attr));
> > attr.prog_type = load_attr->prog_type;
> > attr.expected_attach_type = load_attr->expected_attach_type;
> > - if (attr.prog_type == BPF_PROG_TYPE_STRUCT_OPS) {
> > + if (attr.prog_type == BPF_PROG_TYPE_STRUCT_OPS ||
> > + attr.prog_type == BPF_PROG_TYPE_LSM) {
> > attr.attach_btf_id = load_attr->attach_btf_id;
> > } else if (attr.prog_type == BPF_PROG_TYPE_TRACING ||
> > attr.prog_type == BPF_PROG_TYPE_EXT) {
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 085e41f9b68e..da8bee78e1ce 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -2362,7 +2362,8 @@ static int bpf_object__finalize_btf(struct bpf_object *obj)
> >
> > static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
> > {
> > - if (prog->type == BPF_PROG_TYPE_STRUCT_OPS)
> > + if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
> > + prog->type == BPF_PROG_TYPE_LSM)
> > return true;
> >
> > /* BPF_PROG_TYPE_TRACING programs which do not attach to other programs
> > @@ -4870,7 +4871,8 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
> > load_attr.insns = insns;
> > load_attr.insns_cnt = insns_cnt;
> > load_attr.license = license;
> > - if (prog->type == BPF_PROG_TYPE_STRUCT_OPS) {
> > + if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
> > + prog->type == BPF_PROG_TYPE_LSM) {
> > load_attr.attach_btf_id = prog->attach_btf_id;
> > } else if (prog->type == BPF_PROG_TYPE_TRACING ||
> > prog->type == BPF_PROG_TYPE_EXT) {
> > @@ -4955,6 +4957,7 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
> > int err = 0, fd, i, btf_id;
> >
> > if ((prog->type == BPF_PROG_TYPE_TRACING ||
> > + prog->type == BPF_PROG_TYPE_LSM ||
> > prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {
> > btf_id = libbpf_find_attach_btf_id(prog);
> > if (btf_id <= 0)
> > @@ -6194,6 +6197,7 @@ bool bpf_program__is_##NAME(const struct bpf_program *prog) \
> > } \
> >
> > BPF_PROG_TYPE_FNS(socket_filter, BPF_PROG_TYPE_SOCKET_FILTER);
> > +BPF_PROG_TYPE_FNS(lsm, BPF_PROG_TYPE_LSM);
> > BPF_PROG_TYPE_FNS(kprobe, BPF_PROG_TYPE_KPROBE);
> > BPF_PROG_TYPE_FNS(sched_cls, BPF_PROG_TYPE_SCHED_CLS);
> > BPF_PROG_TYPE_FNS(sched_act, BPF_PROG_TYPE_SCHED_ACT);
> > @@ -6260,6 +6264,8 @@ static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
> > struct bpf_program *prog);
> > static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
> > struct bpf_program *prog);
> > +static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
> > + struct bpf_program *prog);
> >
> > struct bpf_sec_def {
> > const char *sec;
> > @@ -6310,6 +6316,10 @@ static const struct bpf_sec_def section_defs[] = {
> > SEC_DEF("freplace/", EXT,
> > .is_attach_btf = true,
> > .attach_fn = attach_trace),
> > + SEC_DEF("lsm/", LSM,
> > + .is_attach_btf = true,
> > + .expected_attach_type = BPF_LSM_MAC,
> > + .attach_fn = attach_lsm),
> > BPF_PROG_SEC("xdp", BPF_PROG_TYPE_XDP),
> > BPF_PROG_SEC("perf_event", BPF_PROG_TYPE_PERF_EVENT),
> > BPF_PROG_SEC("lwt_in", BPF_PROG_TYPE_LWT_IN),
> > @@ -6572,6 +6582,7 @@ static int bpf_object__collect_struct_ops_map_reloc(struct bpf_object *obj,
> > }
> >
> > #define BTF_TRACE_PREFIX "btf_trace_"
> > +#define BTF_LSM_PREFIX "bpf_lsm_"
> > #define BTF_MAX_NAME_SIZE 128
> >
> > static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
> > @@ -6599,6 +6610,9 @@ static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name,
> > if (attach_type == BPF_TRACE_RAW_TP)
> > err = find_btf_by_prefix_kind(btf, BTF_TRACE_PREFIX, name,
> > BTF_KIND_TYPEDEF);
> > + else if (attach_type == BPF_LSM_MAC)
> > + err = find_btf_by_prefix_kind(btf, BTF_LSM_PREFIX, name,
> > + BTF_KIND_FUNC);
> > else
> > err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
> >
> > @@ -7452,7 +7466,8 @@ static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
> > return bpf_program__attach_raw_tracepoint(prog, tp_name);
> > }
> >
> > -struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
> > +/* Common logic for all BPF program types that attach to a btf_id */
> > +static struct bpf_link *bpf_program__attach_btf(struct bpf_program *prog)
>
> bpf_program__attach_btf_id() would be a bit more precise name

Agreed, Updated.

>
> > {
> > char errmsg[STRERR_BUFSIZE];
> > struct bpf_link *link;
> > @@ -7474,7 +7489,7 @@ struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
> > if (pfd < 0) {
> > pfd = -errno;
> > free(link);
> > - pr_warn("program '%s': failed to attach to trace: %s\n",
> > + pr_warn("program '%s': failed to attach: %s\n",
> > bpf_program__title(prog, false),
> > libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
> > return ERR_PTR(pfd);
> > @@ -7483,10 +7498,26 @@ struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
> > return (struct bpf_link *)link;
> > }
> >
> > +struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
> > +{
> > + return bpf_program__attach_btf(prog);
> > +}
> > +
> > +struct bpf_link *bpf_program__attach_lsm(struct bpf_program *prog)
> > +{
> > + return bpf_program__attach_btf(prog);
> > +}
> > +
> > static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
> > struct bpf_program *prog)
> > {
> > - return bpf_program__attach_trace(prog);
> > + return bpf_program__attach_btf(prog);
>
> well, no, it should call bpf_program__attach_trace()

You are right, the static helper should not be called directly.

Updated this and the LSM call to call their respective functions.

>
> > +}
> > +
> > +static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
> > + struct bpf_program *prog)
> > +{
> > + return bpf_program__attach_btf(prog);
>
> and bpf_program__attach_lsm() here, don't shortcut invocation (you
> argued yourself above, what if something about LSM changes, why
> updating this invocation as well?)

Makes sense.

- KP

>
> > }
> >
> > struct bpf_link *bpf_program__attach(struct bpf_program *prog)

[...]

> > + bpf_program__is_lsm;
> > bpf_program__set_attach_target;
> > + bpf_program__set_lsm;
> > } LIBBPF_0.0.7;
> > --
> > 2.20.1
> >