libbpf: Support expected_attach_type at prog load

Support setting `expected_attach_type` at prog load time in both
`bpf/bpf.h` and `bpf/libbpf.h`.

Since both headers already have API to load programs, new functions are
added not to break backward compatibility for existing ones:
* `bpf_load_program_xattr()` is added to `bpf/bpf.h`;
* `bpf_prog_load_xattr()` is added to `bpf/libbpf.h`.

Both new functions accept structures, `struct bpf_load_program_attr` and
`struct bpf_prog_load_attr` correspondingly, where new fields can be
added in the future w/o changing the API.

Standard `_xattr` suffix is used to name the new API functions.

Since `bpf_load_program_name()` is not used as heavily as
`bpf_load_program()`, it was removed in favor of more generic
`bpf_load_program_xattr()`.

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

4 files changed, 128 insertions, 46 deletions

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index e0500055f1a6..acbb3f8b3bec 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -146,26 +146,30 @@ int bpf_create_map_in_map(enum bpf_map_type map_type, const char *name,
                                           -1);
 }
 
-int bpf_load_program_name(enum bpf_prog_type type, const char *name,
-                          const struct bpf_insn *insns,
-                          size_t insns_cnt, const char *license,
-                          __u32 kern_version, char *log_buf,
-                          size_t log_buf_sz)
+int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
+                           char *log_buf, size_t log_buf_sz)
 {
-        int fd;
         union bpf_attr attr;
-        __u32 name_len = name ? strlen(name) : 0;
+        __u32 name_len;
+        int fd;
+
+        if (!load_attr)
+                return -EINVAL;
+
+        name_len = load_attr->name ? strlen(load_attr->name) : 0;
 
         bzero(&attr, sizeof(attr));
-        attr.prog_type = type;
-        attr.insn_cnt = (__u32)insns_cnt;
-        attr.insns = ptr_to_u64(insns);
-        attr.license = ptr_to_u64(license);
+        attr.prog_type = load_attr->prog_type;
+        attr.expected_attach_type = load_attr->expected_attach_type;
+        attr.insn_cnt = (__u32)load_attr->insns_cnt;
+        attr.insns = ptr_to_u64(load_attr->insns);
+        attr.license = ptr_to_u64(load_attr->license);
         attr.log_buf = ptr_to_u64(NULL);
         attr.log_size = 0;
         attr.log_level = 0;
-        attr.kern_version = kern_version;
-        memcpy(attr.prog_name, name, min(name_len, BPF_OBJ_NAME_LEN - 1));
+        attr.kern_version = load_attr->kern_version;
+        memcpy(attr.prog_name, load_attr->name,
+               min(name_len, BPF_OBJ_NAME_LEN - 1));
 
         fd = sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
         if (fd >= 0 || !log_buf || !log_buf_sz)
@@ -184,8 +188,18 @@ int bpf_load_program(enum bpf_prog_type type, const struct bpf_insn *insns,
                      __u32 kern_version, char *log_buf,
                      size_t log_buf_sz)
 {
-        return bpf_load_program_name(type, NULL, insns, insns_cnt, license,
-                                     kern_version, log_buf, log_buf_sz);
+        struct bpf_load_program_attr load_attr;
+
+        memset(&load_attr, 0, sizeof(struct bpf_load_program_attr));
+        load_attr.prog_type = type;
+        load_attr.expected_attach_type = 0;
+        load_attr.name = NULL;
+        load_attr.insns = insns;
+        load_attr.insns_cnt = insns_cnt;
+        load_attr.license = license;
+        load_attr.kern_version = kern_version;
+
+        return bpf_load_program_xattr(&load_attr, log_buf, log_buf_sz);
 }
 
 int bpf_verify_program(enum bpf_prog_type type, const struct bpf_insn *insns,
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index ee59342c6f42..39f6a0d64a3b 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -41,13 +41,20 @@ int bpf_create_map_in_map(enum bpf_map_type map_type, const char *name,
                           int key_size, int inner_map_fd, int max_entries,
                           __u32 map_flags);
 
+struct bpf_load_program_attr {
+        enum bpf_prog_type prog_type;
+        enum bpf_attach_type expected_attach_type;
+        const char *name;
+        const struct bpf_insn *insns;
+        size_t insns_cnt;
+        const char *license;
+        __u32 kern_version;
+};
+
 /* Recommend log buffer size */
 #define BPF_LOG_BUF_SIZE (256 * 1024)
-int bpf_load_program_name(enum bpf_prog_type type, const char *name,
-                          const struct bpf_insn *insns,
-                          size_t insns_cnt, const char *license,
-                          __u32 kern_version, char *log_buf,
-                          size_t log_buf_sz);
+int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
+                           char *log_buf, size_t log_buf_sz);
 int bpf_load_program(enum bpf_prog_type type, const struct bpf_insn *insns,
                      size_t insns_cnt, const char *license,
                      __u32 kern_version, char *log_buf,
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 64a8fc384186..48e3e743ebf7 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -203,6 +203,8 @@ struct bpf_program {
         struct bpf_object *obj;
         void *priv;
         bpf_program_clear_priv_t clear_priv;
+
+        enum bpf_attach_type expected_attach_type;
 };
 
 struct bpf_map {
@@ -1162,21 +1164,31 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
 }
 
 static int
-load_program(enum bpf_prog_type type, const char *name, struct bpf_insn *insns,
-             int insns_cnt, char *license, u32 kern_version, int *pfd)
+load_program(enum bpf_prog_type type, enum bpf_attach_type expected_attach_type,
+             const char *name, struct bpf_insn *insns, int insns_cnt,
+             char *license, u32 kern_version, int *pfd)
 {
-        int ret;
+        struct bpf_load_program_attr load_attr;
         char *log_buf;
+        int ret;
 
-        if (!insns || !insns_cnt)
+        memset(&load_attr, 0, sizeof(struct bpf_load_program_attr));
+        load_attr.prog_type = type;
+        load_attr.expected_attach_type = expected_attach_type;
+        load_attr.name = name;
+        load_attr.insns = insns;
+        load_attr.insns_cnt = insns_cnt;
+        load_attr.license = license;
+        load_attr.kern_version = kern_version;
+
+        if (!load_attr.insns || !load_attr.insns_cnt)
                 return -EINVAL;
 
         log_buf = malloc(BPF_LOG_BUF_SIZE);
         if (!log_buf)
                 pr_warning("Alloc log buffer for bpf loader error, continue without log\n");
 
-        ret = bpf_load_program_name(type, name, insns, insns_cnt, license,
-                                    kern_version, log_buf, BPF_LOG_BUF_SIZE);
+        ret = bpf_load_program_xattr(&load_attr, log_buf, BPF_LOG_BUF_SIZE);
 
         if (ret >= 0) {
                 *pfd = ret;
@@ -1192,18 +1204,18 @@ load_program(enum bpf_prog_type type, const char *name, struct bpf_insn *insns,
                 pr_warning("-- BEGIN DUMP LOG ---\n");
                 pr_warning("\n%s\n", log_buf);
                 pr_warning("-- END LOG --\n");
-        } else if (insns_cnt >= BPF_MAXINSNS) {
-                pr_warning("Program too large (%d insns), at most %d insns\n",
-                           insns_cnt, BPF_MAXINSNS);
+        } else if (load_attr.insns_cnt >= BPF_MAXINSNS) {
+                pr_warning("Program too large (%zu insns), at most %d insns\n",
+                           load_attr.insns_cnt, BPF_MAXINSNS);
                 ret = -LIBBPF_ERRNO__PROG2BIG;
         } else {
                 /* Wrong program type? */
-                if (type != BPF_PROG_TYPE_KPROBE) {
+                if (load_attr.prog_type != BPF_PROG_TYPE_KPROBE) {
                         int fd;
 
-                        fd = bpf_load_program_name(BPF_PROG_TYPE_KPROBE, name,
-                                                   insns, insns_cnt, license,
-                                                   kern_version, NULL, 0);
+                        load_attr.prog_type = BPF_PROG_TYPE_KPROBE;
+                        load_attr.expected_attach_type = 0;
+                        fd = bpf_load_program_xattr(&load_attr, NULL, 0);
                         if (fd >= 0) {
                                 close(fd);
                                 ret = -LIBBPF_ERRNO__PROGTYPE;
@@ -1247,8 +1259,9 @@ bpf_program__load(struct bpf_program *prog,
                         pr_warning("Program '%s' is inconsistent: nr(%d) != 1\n",
                                    prog->section_name, prog->instances.nr);
                 }
-                err = load_program(prog->type, prog->name, prog->insns,
-                                   prog->insns_cnt, license, kern_version, &fd);
+                err = load_program(prog->type, prog->expected_attach_type,
+                                   prog->name, prog->insns, prog->insns_cnt,
+                                   license, kern_version, &fd);
                 if (!err)
                         prog->instances.fds[0] = fd;
                 goto out;
@@ -1276,8 +1289,8 @@ bpf_program__load(struct bpf_program *prog,
                         continue;
                 }
 
-                err = load_program(prog->type, prog->name,
-                                   result.new_insn_ptr,
+                err = load_program(prog->type, prog->expected_attach_type,
+                                   prog->name, result.new_insn_ptr,
                                    result.new_insn_cnt,
                                    license, kern_version, &fd);
 
@@ -1835,11 +1848,22 @@ BPF_PROG_TYPE_FNS(tracepoint, BPF_PROG_TYPE_TRACEPOINT);
 BPF_PROG_TYPE_FNS(xdp, BPF_PROG_TYPE_XDP);
 BPF_PROG_TYPE_FNS(perf_event, BPF_PROG_TYPE_PERF_EVENT);
 
-#define BPF_PROG_SEC(string, type) { string, sizeof(string) - 1, type }
+static void bpf_program__set_expected_attach_type(struct bpf_program *prog,
+                                                 enum bpf_attach_type type)
+{
+        prog->expected_attach_type = type;
+}
+
+#define BPF_PROG_SEC_FULL(string, ptype, atype) \
+        { string, sizeof(string) - 1, ptype, atype }
+
+#define BPF_PROG_SEC(string, ptype) BPF_PROG_SEC_FULL(string, ptype, 0)
+
 static const struct {
         const char *sec;
         size_t len;
         enum bpf_prog_type prog_type;
+        enum bpf_attach_type expected_attach_type;
 } section_names[] = {
         BPF_PROG_SEC("socket",          BPF_PROG_TYPE_SOCKET_FILTER),
         BPF_PROG_SEC("kprobe/",         BPF_PROG_TYPE_KPROBE),
@@ -1859,9 +1883,11 @@ static const struct {
         BPF_PROG_SEC("sk_skb",          BPF_PROG_TYPE_SK_SKB),
         BPF_PROG_SEC("sk_msg",          BPF_PROG_TYPE_SK_MSG),
 };
+
 #undef BPF_PROG_SEC
+#undef BPF_PROG_SEC_FULL
 
-static enum bpf_prog_type bpf_program__guess_type(struct bpf_program *prog)
+static int bpf_program__identify_section(struct bpf_program *prog)
 {
         int i;
 
@@ -1871,13 +1897,13 @@ static enum bpf_prog_type bpf_program__guess_type(struct bpf_program *prog)
         for (i = 0; i < ARRAY_SIZE(section_names); i++)
                 if (strncmp(prog->section_name, section_names[i].sec,
                             section_names[i].len) == 0)
-                        return section_names[i].prog_type;
+                        return i;
 
 err:
         pr_warning("failed to guess program type based on section name %s\n",
                    prog->section_name);
 
-        return BPF_PROG_TYPE_UNSPEC;
+        return -1;
 }
 
 int bpf_map__fd(struct bpf_map *map)
@@ -1977,11 +2003,30 @@ long libbpf_get_error(const void *ptr)
 int bpf_prog_load(const char *file, enum bpf_prog_type type,
                   struct bpf_object **pobj, int *prog_fd)
 {
+        struct bpf_prog_load_attr attr;
+
+        memset(&attr, 0, sizeof(struct bpf_prog_load_attr));
+        attr.file = file;
+        attr.prog_type = type;
+        attr.expected_attach_type = 0;
+
+        return bpf_prog_load_xattr(&attr, pobj, prog_fd);
+}
+
+int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
+                        struct bpf_object **pobj, int *prog_fd)
+{
         struct bpf_program *prog, *first_prog = NULL;
+        enum bpf_attach_type expected_attach_type;
+        enum bpf_prog_type prog_type;
         struct bpf_object *obj;
+        int section_idx;
         int err;
 
-        obj = bpf_object__open(file);
+        if (!attr)
+                return -EINVAL;
+
+        obj = bpf_object__open(attr->file);
         if (IS_ERR(obj))
                 return -ENOENT;
 
@@ -1990,15 +2035,23 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
                  * If type is not specified, try to guess it based on
                  * section name.
                  */
-                if (type == BPF_PROG_TYPE_UNSPEC) {
-                        type = bpf_program__guess_type(prog);
-                        if (type == BPF_PROG_TYPE_UNSPEC) {
+                prog_type = attr->prog_type;
+                expected_attach_type = attr->expected_attach_type;
+                if (prog_type == BPF_PROG_TYPE_UNSPEC) {
+                        section_idx = bpf_program__identify_section(prog);
+                        if (section_idx < 0) {
                                 bpf_object__close(obj);
                                 return -EINVAL;
                         }
+                        prog_type = section_names[section_idx].prog_type;
+                        expected_attach_type =
+                                section_names[section_idx].expected_attach_type;
                 }
 
-                bpf_program__set_type(prog, type);
+                bpf_program__set_type(prog, prog_type);
+                bpf_program__set_expected_attach_type(prog,
+                                                      expected_attach_type);
+
                 if (prog->idx != obj->efile.text_shndx && !first_prog)
                         first_prog = prog;
         }
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index f85906533cdd..a3a62a583f27 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -248,6 +248,14 @@ int bpf_map__pin(struct bpf_map *map, const char *path);
 
 long libbpf_get_error(const void *ptr);
 
+struct bpf_prog_load_attr {
+        const char *file;
+        enum bpf_prog_type prog_type;
+        enum bpf_attach_type expected_attach_type;
+};
+
+int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
+                        struct bpf_object **pobj, int *prog_fd);
 int bpf_prog_load(const char *file, enum bpf_prog_type type,
                   struct bpf_object **pobj, int *prog_fd);