Re: [PATCH bpf-next v1 05/13] tools/libbpf: Add support in libbpf for BPF_PROG_TYPE_LSM

From: Andrii Nakryiko
Date: Mon Dec 23 2019 - 19:09:36 EST

On Mon, Dec 23, 2019 at 4:07 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Fri, Dec 20, 2019 at 7:43 AM KP Singh <kpsingh@xxxxxxxxxxxx> wrote:
> >
> > From: KP Singh <kpsingh@xxxxxxxxxx>
> >
> > Update the libbpf library with functionality to load and
> > attach a program type BPF_PROG_TYPE_LSM, currently with
> > only one expected attach type BPF_LSM_MAC.
> >
> > Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx>
> > ---
> > tools/lib/bpf/bpf.c | 2 +-
> > tools/lib/bpf/bpf.h | 6 +++++
> > tools/lib/bpf/libbpf.c | 44 +++++++++++++++++++++--------------
> > tools/lib/bpf/libbpf.h | 2 ++
> > tools/lib/bpf/libbpf.map | 6 +++++
> > tools/lib/bpf/libbpf_probes.c | 1 +
> > 6 files changed, 43 insertions(+), 18 deletions(-)
> >
> > diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> > index 98596e15390f..9c6fb083f7de 100644
> > --- a/tools/lib/bpf/bpf.c
> > +++ b/tools/lib/bpf/bpf.c
> > @@ -228,7 +228,7 @@ 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_TRACING) {
> > + if (needs_btf_attach(attr.prog_type)) {
> > attr.attach_btf_id = load_attr->attach_btf_id;
> > attr.attach_prog_fd = load_attr->attach_prog_fd;
> > } else {
> > diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
> > index 3c791fa8e68e..df2a00ff349f 100644
> > --- a/tools/lib/bpf/bpf.h
> > +++ b/tools/lib/bpf/bpf.h
> > @@ -177,6 +177,12 @@ LIBBPF_API int bpf_task_fd_query(int pid, int fd, __u32 flags, char *buf,
> > __u32 *buf_len, __u32 *prog_id, __u32 *fd_type,
> > __u64 *probe_offset, __u64 *probe_addr);
> >
> > +static inline bool needs_btf_attach(enum bpf_prog_type prog_type)
> > +{
> > + return (prog_type == BPF_PROG_TYPE_TRACING ||
> > + prog_type == BPF_PROG_TYPE_LSM);
> > +}
> > +
>
> This doesn't have to be a public API, right? It also doesn't follow
> naming conventions of libbpf APIs. Let's just move it into
> libbpf_internal.h, given it's used in few files.
>
> Also, Martin's patches add STRUCT_OPS, which do need btf_attach, but
> don't set attach_prog_fd. So maybe something like
> libbpf_need_attach_prog_btf() for a name to be a bit more specific?
>
>
> > #ifdef __cplusplus
> > } /* extern "C" */
> > #endif
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index b20f82e58989..b0b27d8e5a37 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -3738,7 +3738,7 @@ 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_TRACING) {
> > + if (needs_btf_attach(prog->type)) {
> > load_attr.attach_prog_fd = prog->attach_prog_fd;
> > load_attr.attach_btf_id = prog->attach_btf_id;
> > } else {
> > @@ -3983,7 +3983,7 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
> >
> > bpf_program__set_type(prog, prog_type);
> > bpf_program__set_expected_attach_type(prog, attach_type);
> > - if (prog_type == BPF_PROG_TYPE_TRACING) {
> > + if (needs_btf_attach(prog_type)) {
> > err = libbpf_find_attach_btf_id(prog->section_name,
> > attach_type,
> > attach_prog_fd);
> > @@ -4933,6 +4933,7 @@ 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);
> > @@ -5009,6 +5010,8 @@ static const struct {
> > BPF_PROG_SEC("lwt_out", BPF_PROG_TYPE_LWT_OUT),
> > BPF_PROG_SEC("lwt_xmit", BPF_PROG_TYPE_LWT_XMIT),
> > BPF_PROG_SEC("lwt_seg6local", BPF_PROG_TYPE_LWT_SEG6LOCAL),
> > + BPF_PROG_BTF("lsm/", BPF_PROG_TYPE_LSM,
> > + BPF_LSM_MAC),
>
> Is is supposed to be attachable same as BPF_PROG_TYPE_TRACING
> programs? If yes, please define auto-attaching function, similar to
> SEC_DEF("raw_tp") few lines below this one.
>

ah, haven't gotten to patch 11 yet, disregard this.

> > BPF_APROG_SEC("cgroup_skb/ingress", BPF_PROG_TYPE_CGROUP_SKB,
> > BPF_CGROUP_INET_INGRESS),
> > BPF_APROG_SEC("cgroup_skb/egress", BPF_PROG_TYPE_CGROUP_SKB,
> > @@ -5119,32 +5122,39 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
> > return -ESRCH;
> > }
> >
> > -#define BTF_PREFIX "btf_trace_"
> > +static inline int __btf__typdef_with_prefix(struct btf *btf, const char *name,
>
> typo: typdef -> typedef
>
> But actually let's generalize it to pass BTF_KIND as another param, I
> think I have a need for this (we might want to do that for structs,
> not just typedef->func_proto).
> Following btf__find_by_name_kind() naming, it probably should be
> called btf__find_by_prefix_kind()?
>
> > + const char *prefix)
> > +{
> > +
> > + size_t prefix_len = strlen(prefix);
> > + char btf_type_name[128];
> > +
> > + strcpy(btf_type_name, prefix);
> > + strncat(btf_type_name, name, sizeof(btf_type_name) - (prefix_len + 1));
>
> at this point snprintf(btf_type_name, "%s%.*%s", prefix,
> sizeof(btf_type_name) - prefix_len - 1, name) looks like a better and
> cleaner alternative.
>
> > + return btf__find_by_name_kind(btf, btf_type_name, BTF_KIND_TYPEDEF);
> > +}
> > +
> > +#define BTF_TRACE_PREFIX "btf_trace_"
> > +#define BTF_LSM_PREFIX "lsm_btf_"
> > +
>
> [...]