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libbpf: Add support for attaching BPF programs to other BPF programs

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Extend libbpf api to pass attach_prog_fd into bpf_object__open.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-19-ast@kernel.org
This commit is contained in:
Alexei Starovoitov 2019-11-14 10:57:18 -08:00 committed by Daniel Borkmann
parent 5b92a28aae
commit e7bf94dbb8
5 changed files with 71 additions and 17 deletions
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1
tools/include/uapi/linux/bpf.h
View File

@ -425,6 +425,7 @@ union bpf_attr {
__aligned_u64 line_info; /* line info */
__u32 line_info_cnt; /* number of bpf_line_info records */
__u32 attach_btf_id; /* in-kernel BTF type id to attach to */
__u32 attach_prog_fd; /* 0 to attach to vmlinux */
};
struct { /* anonymous struct used by BPF_OBJ_* commands */

8
tools/lib/bpf/bpf.c
View File

@ -228,10 +228,13 @@ 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 (attr.prog_type == BPF_PROG_TYPE_TRACING) {
attr.attach_btf_id = load_attr->attach_btf_id;
else
attr.attach_prog_fd = load_attr->attach_prog_fd;
} else {
attr.prog_ifindex = load_attr->prog_ifindex;
attr.kern_version = load_attr->kern_version;
}
attr.insn_cnt = (__u32)load_attr->insns_cnt;
attr.insns = ptr_to_u64(load_attr->insns);
attr.license = ptr_to_u64(load_attr->license);
@ -245,7 +248,6 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
attr.log_size = 0;
}
attr.kern_version = load_attr->kern_version;
attr.prog_btf_fd = load_attr->prog_btf_fd;
attr.func_info_rec_size = load_attr->func_info_rec_size;
attr.func_info_cnt = load_attr->func_info_cnt;

5
tools/lib/bpf/bpf.h
View File

@ -77,7 +77,10 @@ struct bpf_load_program_attr {
const struct bpf_insn *insns;
size_t insns_cnt;
const char *license;
__u32 kern_version;
union {
__u32 kern_version;
__u32 attach_prog_fd;
};
union {
__u32 prog_ifindex;
__u32 attach_btf_id;

71
tools/lib/bpf/libbpf.c
View File

@ -189,6 +189,7 @@ struct bpf_program {
enum bpf_attach_type expected_attach_type;
__u32 attach_btf_id;
__u32 attach_prog_fd;
void *func_info;
__u32 func_info_rec_size;
__u32 func_info_cnt;
@ -3683,8 +3684,13 @@ 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;
load_attr.kern_version = kern_version;
load_attr.prog_ifindex = prog->prog_ifindex;
if (prog->type == BPF_PROG_TYPE_TRACING) {
load_attr.attach_prog_fd = prog->attach_prog_fd;
load_attr.attach_btf_id = prog->attach_btf_id;
} else {
load_attr.kern_version = kern_version;
load_attr.prog_ifindex = prog->prog_ifindex;
}
/* if .BTF.ext was loaded, kernel supports associated BTF for prog */
if (prog->obj->btf_ext)
btf_fd = bpf_object__btf_fd(prog->obj);
@ -3699,7 +3705,6 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
load_attr.line_info_cnt = prog->line_info_cnt;
load_attr.log_level = prog->log_level;
load_attr.prog_flags = prog->prog_flags;
load_attr.attach_btf_id = prog->attach_btf_id;
retry_load:
log_buf = malloc(log_buf_size);
@ -3856,9 +3861,9 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level)
return 0;
}
static int libbpf_attach_btf_id_by_name(const char *name,
enum bpf_attach_type attach_type);
static int libbpf_find_attach_btf_id(const char *name,
enum bpf_attach_type attach_type,
__u32 attach_prog_fd);
static struct bpf_object *
__bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
struct bpf_object_open_opts *opts)
@ -3869,6 +3874,7 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
const char *obj_name;
char tmp_name[64];
bool relaxed_maps;
__u32 attach_prog_fd;
int err;
if (elf_version(EV_CURRENT) == EV_NONE) {
@ -3899,6 +3905,7 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
obj->relaxed_core_relocs = OPTS_GET(opts, relaxed_core_relocs, false);
relaxed_maps = OPTS_GET(opts, relaxed_maps, false);
pin_root_path = OPTS_GET(opts, pin_root_path, NULL);
attach_prog_fd = OPTS_GET(opts, attach_prog_fd, 0);
CHECK_ERR(bpf_object__elf_init(obj), err, out);
CHECK_ERR(bpf_object__check_endianness(obj), err, out);
@ -3923,11 +3930,13 @@ __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) {
err = libbpf_attach_btf_id_by_name(prog->section_name,
attach_type);
err = libbpf_find_attach_btf_id(prog->section_name,
attach_type,
attach_prog_fd);
if (err <= 0)
goto out;
prog->attach_btf_id = err;
prog->attach_prog_fd = attach_prog_fd;
}
}
@ -5086,8 +5095,42 @@ int libbpf_find_vmlinux_btf_id(const char *name,
return err;
}
static int libbpf_attach_btf_id_by_name(const char *name,
enum bpf_attach_type attach_type)
static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
{
struct bpf_prog_info_linear *info_linear;
struct bpf_prog_info *info;
struct btf *btf = NULL;
int err = -EINVAL;
info_linear = bpf_program__get_prog_info_linear(attach_prog_fd, 0);
if (IS_ERR_OR_NULL(info_linear)) {
pr_warn("failed get_prog_info_linear for FD %d\n",
attach_prog_fd);
return -EINVAL;
}
info = &info_linear->info;
if (!info->btf_id) {
pr_warn("The target program doesn't have BTF\n");
goto out;
}
if (btf__get_from_id(info->btf_id, &btf)) {
pr_warn("Failed to get BTF of the program\n");
goto out;
}
err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
btf__free(btf);
if (err <= 0) {
pr_warn("%s is not found in prog's BTF\n", name);
goto out;
}
out:
free(info_linear);
return err;
}
static int libbpf_find_attach_btf_id(const char *name,
enum bpf_attach_type attach_type,
__u32 attach_prog_fd)
{
int i, err;
@ -5099,8 +5142,12 @@ static int libbpf_attach_btf_id_by_name(const char *name,
continue;
if (strncmp(name, section_names[i].sec, section_names[i].len))
continue;
err = libbpf_find_vmlinux_btf_id(name + section_names[i].len,
attach_type);
if (attach_prog_fd)
err = libbpf_find_prog_btf_id(name + section_names[i].len,
attach_prog_fd);
else
err = libbpf_find_vmlinux_btf_id(name + section_names[i].len,
attach_type);
if (err <= 0)
pr_warn("%s is not found in vmlinux BTF\n", name);
return err;

3
tools/lib/bpf/libbpf.h
View File

@ -108,8 +108,9 @@ struct bpf_object_open_opts {
* auto-pinned to that path on load; defaults to "/sys/fs/bpf".
*/
const char *pin_root_path;
__u32 attach_prog_fd;
};
#define bpf_object_open_opts__last_field pin_root_path
#define bpf_object_open_opts__last_field attach_prog_fd
LIBBPF_API struct bpf_object *bpf_object__open(const char *path);
LIBBPF_API struct bpf_object *