[PATCH bpf-next v3] libbpf: Add support for dynamic program attach target
From: Eelco Chaudron <echaudro@redhat.com>
Date: 2020-02-17 11:02:32
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [library] (libbpf), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest, xdp (express data path) · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds, David S. Miller, Jakub Kicinski, Jesper Dangaard Brouer, John Fastabend
Currently when you want to attach a trace program to a bpf program
the section name needs to match the tracepoint/function semantics.
However the addition of the bpf_program__set_attach_target() API
allows you to specify the tracepoint/function dynamically.
The call flow would look something like this:
xdp_fd = bpf_prog_get_fd_by_id(id);
trace_obj = bpf_object__open_file("func.o", NULL);
prog = bpf_object__find_program_by_title(trace_obj,
"fentry/myfunc");
bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
bpf_program__set_attach_target(prog, xdp_fd,
"xdpfilt_blk_all");
bpf_object__load(trace_obj)
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
---
v1 -> v2: Remove requirement for attach type hint in API
v2 -> v3: Moved common warning to __find_vmlinux_btf_id, requested by Andrii
Updated the xdp_bpf2bpf test to use this new API
tools/lib/bpf/libbpf.c | 34 ++++++++++++++++++--
tools/lib/bpf/libbpf.h | 4 ++
tools/lib/bpf/libbpf.map | 1 +
.../testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c | 16 ++++++++-
.../testing/selftests/bpf/progs/test_xdp_bpf2bpf.c | 4 +-
5 files changed, 50 insertions(+), 9 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 514b1a524abb..0c25d78fb5d8 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c@@ -4939,8 +4939,8 @@ 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_EXT) { + if ((prog->type == BPF_PROG_TYPE_TRACING || + prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) { btf_id = libbpf_find_attach_btf_id(prog); if (btf_id <= 0) return btf_id;
@@ -6583,6 +6583,9 @@ static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name, else err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC); + if (err <= 0) + pr_warn("%s is not found in vmlinux BTF\n", name); + return err; }
@@ -6655,8 +6658,6 @@ static int libbpf_find_attach_btf_id(struct bpf_program *prog) err = __find_vmlinux_btf_id(prog->obj->btf_vmlinux, name + section_defs[i].len, attach_type); - if (err <= 0) - pr_warn("%s is not found in vmlinux BTF\n", name); return err; } pr_warn("failed to identify btf_id based on ELF section name '%s'\n", name);
@@ -8132,6 +8133,31 @@ void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear) } } +int bpf_program__set_attach_target(struct bpf_program *prog, + int attach_prog_fd, + const char *attach_func_name) +{ + int btf_id; + + if (!prog || attach_prog_fd < 0 || !attach_func_name) + return -EINVAL; + + if (attach_prog_fd) + btf_id = libbpf_find_prog_btf_id(attach_func_name, + attach_prog_fd); + else + btf_id = __find_vmlinux_btf_id(prog->obj->btf_vmlinux, + attach_func_name, + prog->expected_attach_type); + + if (btf_id <= 0) + return btf_id; + + prog->attach_btf_id = btf_id; + prog->attach_prog_fd = attach_prog_fd; + return 0; +} + int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz) { int err = 0, n, len, start, end = -1;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 3fe12c9d1f92..02fc58a21a7f 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h@@ -334,6 +334,10 @@ LIBBPF_API void bpf_program__set_expected_attach_type(struct bpf_program *prog, enum bpf_attach_type type); +LIBBPF_API int +bpf_program__set_attach_target(struct bpf_program *prog, int attach_prog_fd, + const char *attach_func_name); + LIBBPF_API bool bpf_program__is_socket_filter(const struct bpf_program *prog); LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program *prog); LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct bpf_program *prog);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index b035122142bb..8aba5438a3f0 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map@@ -230,6 +230,7 @@ LIBBPF_0.0.7 { bpf_program__name; bpf_program__is_extension; bpf_program__is_struct_ops; + bpf_program__set_attach_target; bpf_program__set_extension; bpf_program__set_struct_ops; btf__align_of;
diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c b/tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c
index 6b56bdc73ebc..513fdbf02b81 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c@@ -14,7 +14,7 @@ void test_xdp_bpf2bpf(void) struct test_xdp *pkt_skel = NULL; struct test_xdp_bpf2bpf *ftrace_skel = NULL; struct vip key4 = {.protocol = 6, .family = AF_INET}; - DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts); + struct bpf_program *prog; /* Load XDP program to introspect */ pkt_skel = test_xdp__open_and_load();
@@ -27,11 +27,21 @@ void test_xdp_bpf2bpf(void) bpf_map_update_elem(map_fd, &key4, &value4, 0); /* Load trace program */ - opts.attach_prog_fd = pkt_fd, - ftrace_skel = test_xdp_bpf2bpf__open_opts(&opts); + ftrace_skel = test_xdp_bpf2bpf__open(); if (CHECK(!ftrace_skel, "__open", "ftrace skeleton failed\n")) goto out; + /* Demonstrate the bpf_program__set_attach_target() API rather than + * the load with options, i.e. opts.attach_prog_fd. + */ + prog = *ftrace_skel->skeleton->progs[0].prog; + bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY); + bpf_program__set_attach_target(prog, pkt_fd, "_xdp_tx_iptunnel"); + + prog = *ftrace_skel->skeleton->progs[1].prog; + bpf_program__set_expected_attach_type(prog, BPF_TRACE_FEXIT); + bpf_program__set_attach_target(prog, pkt_fd, "_xdp_tx_iptunnel"); + err = test_xdp_bpf2bpf__load(ftrace_skel); if (CHECK(err, "__load", "ftrace skeleton failed\n")) goto out;
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c b/tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c
index cb8a04ab7a78..b840fc9e3ed5 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c@@ -28,7 +28,7 @@ struct xdp_buff { } __attribute__((preserve_access_index)); __u64 test_result_fentry = 0; -SEC("fentry/_xdp_tx_iptunnel") +SEC("fentry/FUNC") int BPF_PROG(trace_on_entry, struct xdp_buff *xdp) { test_result_fentry = xdp->rxq->dev->ifindex;
@@ -36,7 +36,7 @@ int BPF_PROG(trace_on_entry, struct xdp_buff *xdp) } __u64 test_result_fexit = 0; -SEC("fexit/_xdp_tx_iptunnel") +SEC("fexit/FUNC") int BPF_PROG(trace_on_exit, struct xdp_buff *xdp, int ret) { test_result_fexit = ret;