On 23-Mär 13:25, Andrii Nakryiko wrote:

On Mon, Mar 23, 2020 at 9:45 AM KP Singh [off-list ref] wrote:

quoted

From: KP Singh <redacted>

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 <redacted>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <redacted>
---
 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.

quoted

 {
        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.

quoted

+}
+
+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

quoted

 }

 struct bpf_link *bpf_program__attach(struct bpf_program *prog)

[...]

quoted

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