@@ -178,6 +178,8 @@ struct bpf_capabilities {
__u32 array_mmap:1;
/* BTF_FUNC_GLOBAL is supported */
__u32 btf_func_global:1;
+ /* kernel support for expected_attach_type in BPF_PROG_LOAD */
+ __u32 exp_attach_type:1;
};
enum reloc_type {
@@ -194,6 +196,22 @@ struct reloc_desc {
int sym_off;
};
+struct bpf_sec_def;
+
+typedef struct bpf_link *(*attach_fn_t)(const struct bpf_sec_def *sec,
+ struct bpf_program *prog);
+
+struct bpf_sec_def {
+ const char *sec;
+ size_t len;
+ enum bpf_prog_type prog_type;
+ enum bpf_attach_type expected_attach_type;
+ bool is_exp_attach_type_optional;
+ bool is_attachable;
+ bool is_attach_btf;
+ attach_fn_t attach_fn;
+};
+
/*
* bpf_prog should be a better name but it has been used in
* linux/filter.h.
@@ -204,6 +222,7 @@ struct bpf_program {
char *name;
int prog_ifindex;
char *section_name;
+ const struct bpf_sec_def *sec_def;
/* section_name with / replaced by _; makes recursive pinning
* in bpf_object__pin_programs easier
*/
@@ -3315,6 +3334,37 @@ static int bpf_object__probe_array_mmap(struct bpf_object *obj)
return 0;
}
+static int
+bpf_object__probe_exp_attach_type(struct bpf_object *obj)
+{
+ struct bpf_load_program_attr attr;
+ struct bpf_insn insns[] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ int fd;
+
+ memset(&attr, 0, sizeof(attr));
+ /* use any valid combination of program type and (optional)
+ * non-zero expected attach type (i.e., not a BPF_CGROUP_INET_INGRESS)
+ * to see if kernel supports expected_attach_type field for
+ * BPF_PROG_LOAD command
+ */
+ attr.prog_type = BPF_PROG_TYPE_CGROUP_SOCK;
+ attr.expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE;
+ attr.insns = insns;
+ attr.insns_cnt = ARRAY_SIZE(insns);
+ attr.license = "GPL";
+
+ fd = bpf_load_program_xattr(&attr, NULL, 0);
+ if (fd >= 0) {
+ obj->caps.exp_attach_type = 1;
+ close(fd);
+ return 1;
+ }
+ return 0;
+}
+
static int
bpf_object__probe_caps(struct bpf_object *obj)
{
@@ -3325,6 +3375,7 @@ bpf_object__probe_caps(struct bpf_object *obj)
bpf_object__probe_btf_func_global,
bpf_object__probe_btf_datasec,
bpf_object__probe_array_mmap,
+ bpf_object__probe_exp_attach_type,
};
int i, ret;
@@ -4861,7 +4912,12 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
memset(&load_attr, 0, sizeof(struct bpf_load_program_attr));
load_attr.prog_type = prog->type;
- load_attr.expected_attach_type = prog->expected_attach_type;
+ /* old kernels might not support specifying expected_attach_type */
+ if (!prog->caps->exp_attach_type && prog->sec_def &&
+ prog->sec_def->is_exp_attach_type_optional)
+ load_attr.expected_attach_type = 0;
+ else
+ load_attr.expected_attach_type = prog->expected_attach_type;
if (prog->caps->name)
load_attr.name = prog->name;
load_attr.insns = insns;
@@ -5062,6 +5118,8 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level)
return 0;
}
+static const struct bpf_sec_def *find_sec_def(const char *sec_name);
+
static struct bpf_object *
__bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
const struct bpf_object_open_opts *opts)
@@ -5117,24 +5175,17 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
bpf_object__elf_finish(obj);
bpf_object__for_each_program(prog, obj) {
- enum bpf_prog_type prog_type;
- enum bpf_attach_type attach_type;
-
- if (prog->type != BPF_PROG_TYPE_UNSPEC)
- continue;
-
- err = libbpf_prog_type_by_name(prog->section_name, &prog_type,
- &attach_type);
- if (err == -ESRCH)
+ prog->sec_def = find_sec_def(prog->section_name);
+ if (!prog->sec_def)
/* couldn't guess, but user might manually specify */
continue;
- if (err)
- goto out;
- bpf_program__set_type(prog, prog_type);
- bpf_program__set_expected_attach_type(prog, attach_type);
- if (prog_type == BPF_PROG_TYPE_TRACING ||
- prog_type == BPF_PROG_TYPE_EXT)
+ bpf_program__set_type(prog, prog->sec_def->prog_type);
+ bpf_program__set_expected_attach_type(prog,
+ prog->sec_def->expected_attach_type);
+
+ if (prog->sec_def->prog_type == BPF_PROG_TYPE_TRACING ||
+ prog->sec_def->prog_type == BPF_PROG_TYPE_EXT)
prog->attach_prog_fd = OPTS_GET(opts, attach_prog_fd, 0);
}
@@ -6223,23 +6274,32 @@ void bpf_program__set_expected_attach_type(struct bpf_program *prog,
prog->expected_attach_type = type;
}
-#define BPF_PROG_SEC_IMPL(string, ptype, eatype, is_attachable, btf, atype) \
- { string, sizeof(string) - 1, ptype, eatype, is_attachable, btf, atype }
+#define BPF_PROG_SEC_IMPL(string, ptype, eatype, eatype_optional, \
+ attachable, attach_btf) \
+ { \
+ .sec = string, \
+ .len = sizeof(string) - 1, \
+ .prog_type = ptype, \
+ .expected_attach_type = eatype, \
+ .is_exp_attach_type_optional = eatype_optional, \
+ .is_attachable = attachable, \
+ .is_attach_btf = attach_btf, \
+ }
/* Programs that can NOT be attached. */
#define BPF_PROG_SEC(string, ptype) BPF_PROG_SEC_IMPL(string, ptype, 0, 0, 0, 0)
/* Programs that can be attached. */
#define BPF_APROG_SEC(string, ptype, atype) \
- BPF_PROG_SEC_IMPL(string, ptype, 0, 1, 0, atype)
+ BPF_PROG_SEC_IMPL(string, ptype, atype, true, 1, 0)
/* Programs that must specify expected attach type at load time. */
#define BPF_EAPROG_SEC(string, ptype, eatype) \
- BPF_PROG_SEC_IMPL(string, ptype, eatype, 1, 0, eatype)
+ BPF_PROG_SEC_IMPL(string, ptype, eatype, false, 1, 0)
/* Programs that use BTF to identify attach point */
#define BPF_PROG_BTF(string, ptype, eatype) \
- BPF_PROG_SEC_IMPL(string, ptype, eatype, 0, 1, 0)
+ BPF_PROG_SEC_IMPL(string, ptype, eatype, false, 0, 1)
/* Programs that can be attached but attach type can't be identified by section
* name. Kept for backward compatibility.
@@ -6253,11 +6313,6 @@ void bpf_program__set_expected_attach_type(struct bpf_program *prog,
__VA_ARGS__ \
}
-struct bpf_sec_def;
-
-typedef struct bpf_link *(*attach_fn_t)(const struct bpf_sec_def *sec,
- struct bpf_program *prog);
-
static struct bpf_link *attach_kprobe(const struct bpf_sec_def *sec,
struct bpf_program *prog);
static struct bpf_link *attach_tp(const struct bpf_sec_def *sec,
@@ -6269,17 +6324,6 @@ static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
struct bpf_program *prog);
-struct bpf_sec_def {
- const char *sec;
- size_t len;
- enum bpf_prog_type prog_type;
- enum bpf_attach_type expected_attach_type;
- bool is_attachable;
- bool is_attach_btf;
- enum bpf_attach_type attach_type;
- attach_fn_t attach_fn;
-};
-
static const struct bpf_sec_def section_defs[] = {
BPF_PROG_SEC("socket", BPF_PROG_TYPE_SOCKET_FILTER),
BPF_PROG_SEC("sk_reuseport", BPF_PROG_TYPE_SK_REUSEPORT),
@@ -6713,7 +6757,7 @@ int libbpf_attach_type_by_name(const char *name,
continue;
if (!section_defs[i].is_attachable)
return -EINVAL;
- *attach_type = section_defs[i].attach_type;
+ *attach_type = section_defs[i].expected_attach_type;
return 0;
}
pr_debug("failed to guess attach type based on ELF section name '%s'\n", name);
@@ -7542,7 +7586,6 @@ static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
struct bpf_link *
bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd)
{
- const struct bpf_sec_def *sec_def;
enum bpf_attach_type attach_type;
char errmsg[STRERR_BUFSIZE];
struct bpf_link *link;
@@ -7561,11 +7604,6 @@ bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd)
link->detach = &bpf_link__detach_fd;
attach_type = bpf_program__get_expected_attach_type(prog);
- if (!attach_type) {
- sec_def = find_sec_def(bpf_program__title(prog, false));
- if (sec_def)
- attach_type = sec_def->attach_type;
- }
link_fd = bpf_link_create(prog_fd, cgroup_fd, attach_type, NULL);
if (link_fd < 0) {
link_fd = -errno;
@@ -43,18 +43,18 @@ static struct sec_name_test tests[] = {
{"lwt_seg6local", {0, BPF_PROG_TYPE_LWT_SEG6LOCAL, 0}, {-EINVAL, 0} },
{
"cgroup_skb/ingress",
- {0, BPF_PROG_TYPE_CGROUP_SKB, 0},
+ {0, BPF_PROG_TYPE_CGROUP_SKB, BPF_CGROUP_INET_INGRESS},
{0, BPF_CGROUP_INET_INGRESS},
},
{
"cgroup_skb/egress",
- {0, BPF_PROG_TYPE_CGROUP_SKB, 0},
+ {0, BPF_PROG_TYPE_CGROUP_SKB, BPF_CGROUP_INET_EGRESS},
{0, BPF_CGROUP_INET_EGRESS},
},
{"cgroup/skb", {0, BPF_PROG_TYPE_CGROUP_SKB, 0}, {-EINVAL, 0} },
{
"cgroup/sock",
- {0, BPF_PROG_TYPE_CGROUP_SOCK, 0},
+ {0, BPF_PROG_TYPE_CGROUP_SOCK, BPF_CGROUP_INET_SOCK_CREATE},
{0, BPF_CGROUP_INET_SOCK_CREATE},
},
{
@@ -69,26 +69,38 @@ static struct sec_name_test tests[] = {
},
{
"cgroup/dev",
- {0, BPF_PROG_TYPE_CGROUP_DEVICE, 0},
+ {0, BPF_PROG_TYPE_CGROUP_DEVICE, BPF_CGROUP_DEVICE},
{0, BPF_CGROUP_DEVICE},
},
- {"sockops", {0, BPF_PROG_TYPE_SOCK_OPS, 0}, {0, BPF_CGROUP_SOCK_OPS} },
+ {
+ "sockops",
+ {0, BPF_PROG_TYPE_SOCK_OPS, BPF_CGROUP_SOCK_OPS},
+ {0, BPF_CGROUP_SOCK_OPS},
+ },
{
"sk_skb/stream_parser",
- {0, BPF_PROG_TYPE_SK_SKB, 0},
+ {0, BPF_PROG_TYPE_SK_SKB, BPF_SK_SKB_STREAM_PARSER},
{0, BPF_SK_SKB_STREAM_PARSER},
},
{
"sk_skb/stream_verdict",
- {0, BPF_PROG_TYPE_SK_SKB, 0},
+ {0, BPF_PROG_TYPE_SK_SKB, BPF_SK_SKB_STREAM_VERDICT},
{0, BPF_SK_SKB_STREAM_VERDICT},
},
{"sk_skb", {0, BPF_PROG_TYPE_SK_SKB, 0}, {-EINVAL, 0} },
- {"sk_msg", {0, BPF_PROG_TYPE_SK_MSG, 0}, {0, BPF_SK_MSG_VERDICT} },
- {"lirc_mode2", {0, BPF_PROG_TYPE_LIRC_MODE2, 0}, {0, BPF_LIRC_MODE2} },
+ {
+ "sk_msg",
+ {0, BPF_PROG_TYPE_SK_MSG, BPF_SK_MSG_VERDICT},
+ {0, BPF_SK_MSG_VERDICT},
+ },
+ {
+ "lirc_mode2",
+ {0, BPF_PROG_TYPE_LIRC_MODE2, BPF_LIRC_MODE2},
+ {0, BPF_LIRC_MODE2},
+ },
{
"flow_dissector",
- {0, BPF_PROG_TYPE_FLOW_DISSECTOR, 0},
+ {0, BPF_PROG_TYPE_FLOW_DISSECTOR, BPF_FLOW_DISSECTOR},
{0, BPF_FLOW_DISSECTOR},
},
{
@@ -158,17 +170,17 @@ static void test_prog_type_by_name(const struct sec_name_test *test)
&expected_attach_type);
CHECK(rc != test->expected_load.rc, "check_code",
- "prog: unexpected rc=%d for %s", rc, test->sec_name);
+ "prog: unexpected rc=%d for %s\n", rc, test->sec_name);
if (rc)
return;
CHECK(prog_type != test->expected_load.prog_type, "check_prog_type",
- "prog: unexpected prog_type=%d for %s",
+ "prog: unexpected prog_type=%d for %s\n",
prog_type, test->sec_name);
CHECK(expected_attach_type != test->expected_load.expected_attach_type,
- "check_attach_type", "prog: unexpected expected_attach_type=%d for %s",
+ "check_attach_type", "prog: unexpected expected_attach_type=%d for %s\n",
expected_attach_type, test->sec_name);
}
@@ -180,13 +192,13 @@ static void test_attach_type_by_name(const struct sec_name_test *test)
rc = libbpf_attach_type_by_name(test->sec_name, &attach_type);
CHECK(rc != test->expected_attach.rc, "check_ret",
- "attach: unexpected rc=%d for %s", rc, test->sec_name);
+ "attach: unexpected rc=%d for %s\n", rc, test->sec_name);
if (rc)
return;
CHECK(attach_type != test->expected_attach.attach_type,
- "check_attach_type", "attach: unexpected attach_type=%d for %s",
+ "check_attach_type", "attach: unexpected attach_type=%d for %s\n",
attach_type, test->sec_name);
}
For some types of BPF programs that utilize expected_attach_type, libbpf won't set load_attr.expected_attach_type, even if expected_attach_type is known from section definition. This was done to preserve backwards compatibility with old kernels that didn't recognize expected_attach_type attribute yet (which was added in 5e43f899b03a ("bpf: Check attach type at prog load time"). But this is problematic for some BPF programs that utilize never features that require kernel to know specific expected_attach_type (e.g., extended set of return codes for cgroup_skb/egress programs). This patch makes libbpf specify expected_attach_type by default, but also detect support for this field in kernel and not set it during program load. This allows to have a good metadata for bpf_program (e.g., bpf_program__get_extected_attach_type()), but still work with old kernels (for cases where it can work at all). Additionally, due to expected_attach_type being always set for recognized program types, bpf_program__attach_cgroup doesn't have to do extra checks to determine correct attach type, so remove that additional logic. Also adjust section_names selftest to account for this change. More detailed discussion can be found in [0]. [0] https://lore.kernel.org/bpf/20200412003604.GA15986@rdna-mbp.dhcp.thefacebook.com/ Reported-by: Andrey Ignatov <rdna@fb.com> Acked-by: Song Liu <songliubraving@fb.com> Acked-by: Andrey Ignatov <rdna@fb.com> Signed-off-by: Andrii Nakryiko <andriin@fb.com> --- tools/lib/bpf/libbpf.c | 126 ++++++++++++------ .../selftests/bpf/prog_tests/section_names.c | 42 +++--- 2 files changed, 109 insertions(+), 59 deletions(-)