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libbpf: Add support to attach to fentry/fexit tracing progs 

Teach libbpf to recognize tracing programs types and attach them to
fentry/fexit.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-7-ast@kernel.org
This commit is contained in:
Alexei Starovoitov 2019-11-14 10:57:06 -08:00 committed by Daniel Borkmann
parent 1442e2871b
commit b8c54ea455
4 changed files with 82 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
tools/include/uapi/linux/bpf.h
View File

@ -201,6 +201,8 @@ enum bpf_attach_type {
BPF_CGROUP_GETSOCKOPT,
BPF_CGROUP_SETSOCKOPT,
BPF_TRACE_RAW_TP,
BPF_TRACE_FENTRY,
BPF_TRACE_FEXIT,
__MAX_BPF_ATTACH_TYPE
};

99
tools/lib/bpf/libbpf.c
View File

@ -3856,7 +3856,8 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level)
return 0;
}
static int libbpf_attach_btf_id_by_name(const char *name, __u32 *btf_id);
static int libbpf_attach_btf_id_by_name(const char *name,
enum bpf_attach_type attach_type);
static struct bpf_object *
__bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
@ -3910,7 +3911,6 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
bpf_object__for_each_program(prog, obj) {
enum bpf_prog_type prog_type;
enum bpf_attach_type attach_type;
__u32 btf_id;
err = libbpf_prog_type_by_name(prog->section_name, &prog_type,
&attach_type);
@ -3923,10 +3923,11 @@ __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, &btf_id);
if (err)
err = libbpf_attach_btf_id_by_name(prog->section_name,
attach_type);
if (err <= 0)
goto out;
prog->attach_btf_id = btf_id;
prog->attach_btf_id = err;
}
}
@ -4935,6 +4936,10 @@ static const struct {
BPF_PROG_SEC("raw_tp/", BPF_PROG_TYPE_RAW_TRACEPOINT),
BPF_PROG_BTF("tp_btf/", BPF_PROG_TYPE_TRACING,
BPF_TRACE_RAW_TP),
BPF_PROG_BTF("fentry/", BPF_PROG_TYPE_TRACING,
BPF_TRACE_FENTRY),
BPF_PROG_BTF("fexit/", BPF_PROG_TYPE_TRACING,
BPF_TRACE_FEXIT),
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),
@ -5052,43 +5057,56 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
}
#define BTF_PREFIX "btf_trace_"
static int libbpf_attach_btf_id_by_name(const char *name, __u32 *btf_id)
int libbpf_find_vmlinux_btf_id(const char *name,
enum bpf_attach_type attach_type)
{
struct btf *btf = bpf_core_find_kernel_btf();
char raw_tp_btf_name[128] = BTF_PREFIX;
char *dst = raw_tp_btf_name + sizeof(BTF_PREFIX) - 1;
int ret, i, err = -EINVAL;
char raw_tp_btf[128] = BTF_PREFIX;
char *dst = raw_tp_btf + sizeof(BTF_PREFIX) - 1;
const char *btf_name;
int err = -EINVAL;
u32 kind;
if (IS_ERR(btf)) {
pr_warn("vmlinux BTF is not found\n");
return -EINVAL;
}
if (attach_type == BPF_TRACE_RAW_TP) {
/* prepend "btf_trace_" prefix per kernel convention */
strncat(dst, name, sizeof(raw_tp_btf) - sizeof(BTF_PREFIX));
btf_name = raw_tp_btf;
kind = BTF_KIND_TYPEDEF;
} else {
btf_name = name;
kind = BTF_KIND_FUNC;
}
err = btf__find_by_name_kind(btf, btf_name, kind);
btf__free(btf);
return err;
}
static int libbpf_attach_btf_id_by_name(const char *name,
enum bpf_attach_type attach_type)
{
int i, err;
if (!name)
goto out;
return -EINVAL;
for (i = 0; i < ARRAY_SIZE(section_names); i++) {
if (!section_names[i].is_attach_btf)
continue;
if (strncmp(name, section_names[i].sec, section_names[i].len))
continue;
/* prepend "btf_trace_" prefix per kernel convention */
strncat(dst, name + section_names[i].len,
sizeof(raw_tp_btf_name) - sizeof(BTF_PREFIX));
ret = btf__find_by_name(btf, raw_tp_btf_name);
if (ret <= 0) {
pr_warn("%s is not found in vmlinux BTF\n", dst);
goto out;
}
*btf_id = ret;
err = 0;
goto out;
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;
}
pr_warn("failed to identify btf_id based on ELF section name '%s'\n", name);
err = -ESRCH;
out:
btf__free(btf);
return err;
return -ESRCH;
}
int libbpf_attach_type_by_name(const char *name,
@ -5716,6 +5734,37 @@ struct bpf_link *bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
return (struct bpf_link *)link;
}
struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
{
char errmsg[STRERR_BUFSIZE];
struct bpf_link_fd *link;
int prog_fd, pfd;
prog_fd = bpf_program__fd(prog);
if (prog_fd < 0) {
pr_warn("program '%s': can't attach before loaded\n",
bpf_program__title(prog, false));
return ERR_PTR(-EINVAL);
}
link = malloc(sizeof(*link));
if (!link)
return ERR_PTR(-ENOMEM);
link->link.destroy = &bpf_link__destroy_fd;
pfd = bpf_raw_tracepoint_open(NULL, prog_fd);
if (pfd < 0) {
pfd = -errno;
free(link);
pr_warn("program '%s': failed to attach to trace: %s\n",
bpf_program__title(prog, false),
libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
return ERR_PTR(pfd);
}
link->fd = pfd;
return (struct bpf_link *)link;
}
enum bpf_perf_event_ret
bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
void **copy_mem, size_t *copy_size,

4
tools/lib/bpf/libbpf.h
View File

@ -188,6 +188,8 @@ libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
enum bpf_attach_type *expected_attach_type);
LIBBPF_API int libbpf_attach_type_by_name(const char *name,
enum bpf_attach_type *attach_type);
LIBBPF_API int libbpf_find_vmlinux_btf_id(const char *name,
enum bpf_attach_type attach_type);
/* Accessors of bpf_program */
struct bpf_program;
@ -251,6 +253,8 @@ LIBBPF_API struct bpf_link *
bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
const char *tp_name);
LIBBPF_API struct bpf_link *
bpf_program__attach_trace(struct bpf_program *prog);
struct bpf_insn;
/*

2
tools/lib/bpf/libbpf.map
View File

@ -199,10 +199,12 @@ LIBBPF_0.0.6 {
bpf_map__set_pin_path;
bpf_object__open_file;
bpf_object__open_mem;
bpf_program__attach_trace;
bpf_program__get_expected_attach_type;
bpf_program__get_type;
bpf_program__is_tracing;
bpf_program__set_tracing;
bpf_program__size;
btf__find_by_name_kind;
libbpf_find_vmlinux_btf_id;
} LIBBPF_0.0.5;