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libbpf: Add generic bpf_program__attach()
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Generalize BPF program attaching and allow libbpf to auto-detect type (and
extra parameters, where applicable) and attach supported BPF program types
based on program sections. Currently this is supported for:
- kprobe/kretprobe;
- tracepoint;
- raw tracepoint;
- tracing programs (typed raw TP/fentry/fexit).

More types support can be trivially added within this framework.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191214014341.3442258-3-andriin@fb.com
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Andrii Nakryiko authored and Alexei Starovoitov committed Dec 15, 2019
1 parent 0d13bfc commit d7a18ea
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Showing 4 changed files with 153 additions and 38 deletions.
181 changes: 147 additions & 34 deletions tools/lib/bpf/libbpf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4972,33 +4972,69 @@ void bpf_program__set_expected_attach_type(struct bpf_program *prog,
*/
#define BPF_APROG_COMPAT(string, ptype) BPF_PROG_SEC(string, ptype)

static const struct {
#define SEC_DEF(sec_pfx, ptype, ...) { \
.sec = sec_pfx, \
.len = sizeof(sec_pfx) - 1, \
.prog_type = BPF_PROG_TYPE_##ptype, \
__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,
struct bpf_program *prog);
static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
struct bpf_program *prog);
static struct bpf_link *attach_trace(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;
} section_names[] = {
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),
BPF_PROG_SEC("kprobe/", BPF_PROG_TYPE_KPROBE),
SEC_DEF("kprobe/", KPROBE,
.attach_fn = attach_kprobe),
BPF_PROG_SEC("uprobe/", BPF_PROG_TYPE_KPROBE),
BPF_PROG_SEC("kretprobe/", BPF_PROG_TYPE_KPROBE),
SEC_DEF("kretprobe/", KPROBE,
.attach_fn = attach_kprobe),
BPF_PROG_SEC("uretprobe/", BPF_PROG_TYPE_KPROBE),
BPF_PROG_SEC("classifier", BPF_PROG_TYPE_SCHED_CLS),
BPF_PROG_SEC("action", BPF_PROG_TYPE_SCHED_ACT),
BPF_PROG_SEC("tracepoint/", BPF_PROG_TYPE_TRACEPOINT),
BPF_PROG_SEC("tp/", BPF_PROG_TYPE_TRACEPOINT),
BPF_PROG_SEC("raw_tracepoint/", BPF_PROG_TYPE_RAW_TRACEPOINT),
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),
SEC_DEF("tracepoint/", TRACEPOINT,
.attach_fn = attach_tp),
SEC_DEF("tp/", TRACEPOINT,
.attach_fn = attach_tp),
SEC_DEF("raw_tracepoint/", RAW_TRACEPOINT,
.attach_fn = attach_raw_tp),
SEC_DEF("raw_tp/", RAW_TRACEPOINT,
.attach_fn = attach_raw_tp),
SEC_DEF("tp_btf/", TRACING,
.expected_attach_type = BPF_TRACE_RAW_TP,
.is_attach_btf = true,
.attach_fn = attach_trace),
SEC_DEF("fentry/", TRACING,
.expected_attach_type = BPF_TRACE_FENTRY,
.is_attach_btf = true,
.attach_fn = attach_trace),
SEC_DEF("fexit/", TRACING,
.expected_attach_type = BPF_TRACE_FEXIT,
.is_attach_btf = true,
.attach_fn = attach_trace),
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),
Expand Down Expand Up @@ -5060,12 +5096,26 @@ static const struct {
#undef BPF_APROG_SEC
#undef BPF_EAPROG_SEC
#undef BPF_APROG_COMPAT
#undef SEC_DEF

#define MAX_TYPE_NAME_SIZE 32

static const struct bpf_sec_def *find_sec_def(const char *sec_name)
{
int i, n = ARRAY_SIZE(section_defs);

for (i = 0; i < n; i++) {
if (strncmp(sec_name,
section_defs[i].sec, section_defs[i].len))
continue;
return &section_defs[i];
}
return NULL;
}

static char *libbpf_get_type_names(bool attach_type)
{
int i, len = ARRAY_SIZE(section_names) * MAX_TYPE_NAME_SIZE;
int i, len = ARRAY_SIZE(section_defs) * MAX_TYPE_NAME_SIZE;
char *buf;

buf = malloc(len);
Expand All @@ -5074,16 +5124,16 @@ static char *libbpf_get_type_names(bool attach_type)

buf[0] = '\0';
/* Forge string buf with all available names */
for (i = 0; i < ARRAY_SIZE(section_names); i++) {
if (attach_type && !section_names[i].is_attachable)
for (i = 0; i < ARRAY_SIZE(section_defs); i++) {
if (attach_type && !section_defs[i].is_attachable)
continue;

if (strlen(buf) + strlen(section_names[i].sec) + 2 > len) {
if (strlen(buf) + strlen(section_defs[i].sec) + 2 > len) {
free(buf);
return NULL;
}
strcat(buf, " ");
strcat(buf, section_names[i].sec);
strcat(buf, section_defs[i].sec);
}

return buf;
Expand All @@ -5092,19 +5142,19 @@ static char *libbpf_get_type_names(bool attach_type)
int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
enum bpf_attach_type *expected_attach_type)
{
const struct bpf_sec_def *sec_def;
char *type_names;
int i;

if (!name)
return -EINVAL;

for (i = 0; i < ARRAY_SIZE(section_names); i++) {
if (strncmp(name, section_names[i].sec, section_names[i].len))
continue;
*prog_type = section_names[i].prog_type;
*expected_attach_type = section_names[i].expected_attach_type;
sec_def = find_sec_def(name);
if (sec_def) {
*prog_type = sec_def->prog_type;
*expected_attach_type = sec_def->expected_attach_type;
return 0;
}

pr_warn("failed to guess program type from ELF section '%s'\n", name);
type_names = libbpf_get_type_names(false);
if (type_names != NULL) {
Expand Down Expand Up @@ -5187,16 +5237,16 @@ static int libbpf_find_attach_btf_id(const char *name,
if (!name)
return -EINVAL;

for (i = 0; i < ARRAY_SIZE(section_names); i++) {
if (!section_names[i].is_attach_btf)
for (i = 0; i < ARRAY_SIZE(section_defs); i++) {
if (!section_defs[i].is_attach_btf)
continue;
if (strncmp(name, section_names[i].sec, section_names[i].len))
if (strncmp(name, section_defs[i].sec, section_defs[i].len))
continue;
if (attach_prog_fd)
err = libbpf_find_prog_btf_id(name + section_names[i].len,
err = libbpf_find_prog_btf_id(name + section_defs[i].len,
attach_prog_fd);
else
err = libbpf_find_vmlinux_btf_id(name + section_names[i].len,
err = libbpf_find_vmlinux_btf_id(name + section_defs[i].len,
attach_type);
if (err <= 0)
pr_warn("%s is not found in vmlinux BTF\n", name);
Expand All @@ -5215,12 +5265,12 @@ int libbpf_attach_type_by_name(const char *name,
if (!name)
return -EINVAL;

for (i = 0; i < ARRAY_SIZE(section_names); i++) {
if (strncmp(name, section_names[i].sec, section_names[i].len))
for (i = 0; i < ARRAY_SIZE(section_defs); i++) {
if (strncmp(name, section_defs[i].sec, section_defs[i].len))
continue;
if (!section_names[i].is_attachable)
if (!section_defs[i].is_attachable)
return -EINVAL;
*attach_type = section_names[i].attach_type;
*attach_type = section_defs[i].attach_type;
return 0;
}
pr_warn("failed to guess attach type based on ELF section name '%s'\n", name);
Expand Down Expand Up @@ -5680,6 +5730,18 @@ struct bpf_link *bpf_program__attach_kprobe(struct bpf_program *prog,
return link;
}

static struct bpf_link *attach_kprobe(const struct bpf_sec_def *sec,
struct bpf_program *prog)
{
const char *func_name;
bool retprobe;

func_name = bpf_program__title(prog, false) + sec->len;
retprobe = strcmp(sec->sec, "kretprobe/") == 0;

return bpf_program__attach_kprobe(prog, retprobe, func_name);
}

struct bpf_link *bpf_program__attach_uprobe(struct bpf_program *prog,
bool retprobe, pid_t pid,
const char *binary_path,
Expand Down Expand Up @@ -5792,6 +5854,32 @@ struct bpf_link *bpf_program__attach_tracepoint(struct bpf_program *prog,
return link;
}

static struct bpf_link *attach_tp(const struct bpf_sec_def *sec,
struct bpf_program *prog)
{
char *sec_name, *tp_cat, *tp_name;
struct bpf_link *link;

sec_name = strdup(bpf_program__title(prog, false));
if (!sec_name)
return ERR_PTR(-ENOMEM);

/* extract "tp/<category>/<name>" */
tp_cat = sec_name + sec->len;
tp_name = strchr(tp_cat, '/');
if (!tp_name) {
link = ERR_PTR(-EINVAL);
goto out;
}
*tp_name = '\0';
tp_name++;

link = bpf_program__attach_tracepoint(prog, tp_cat, tp_name);
out:
free(sec_name);
return link;
}

static int bpf_link__destroy_fd(struct bpf_link *link)
{
struct bpf_link_fd *l = (void *)link;
Expand Down Expand Up @@ -5831,6 +5919,14 @@ struct bpf_link *bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
return (struct bpf_link *)link;
}

static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
struct bpf_program *prog)
{
const char *tp_name = bpf_program__title(prog, false) + sec->len;

return bpf_program__attach_raw_tracepoint(prog, tp_name);
}

struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
{
char errmsg[STRERR_BUFSIZE];
Expand Down Expand Up @@ -5862,6 +5958,23 @@ struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)
return (struct bpf_link *)link;
}

static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
struct bpf_program *prog)
{
return bpf_program__attach_trace(prog);
}

struct bpf_link *bpf_program__attach(struct bpf_program *prog)
{
const struct bpf_sec_def *sec_def;

sec_def = find_sec_def(bpf_program__title(prog, false));
if (!sec_def || !sec_def->attach_fn)
return ERR_PTR(-ESRCH);

return sec_def->attach_fn(sec_def, prog);
}

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,
Expand Down
2 changes: 2 additions & 0 deletions tools/lib/bpf/libbpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -237,6 +237,8 @@ struct bpf_link;

LIBBPF_API int bpf_link__destroy(struct bpf_link *link);

LIBBPF_API struct bpf_link *
bpf_program__attach(struct bpf_program *prog);
LIBBPF_API struct bpf_link *
bpf_program__attach_perf_event(struct bpf_program *prog, int pfd);
LIBBPF_API struct bpf_link *
Expand Down
2 changes: 2 additions & 0 deletions tools/lib/bpf/libbpf.map
View file
Original file line number Diff line number Diff line change
Expand Up @@ -210,4 +210,6 @@ LIBBPF_0.0.6 {
} LIBBPF_0.0.5;

LIBBPF_0.0.7 {
global:
bpf_program__attach;
} LIBBPF_0.0.6;
6 changes: 2 additions & 4 deletions tools/testing/selftests/bpf/prog_tests/probe_user.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,7 @@

void test_probe_user(void)
{
#define kprobe_name "__sys_connect"
const char *prog_name = "kprobe/" kprobe_name;
const char *prog_name = "kprobe/__sys_connect";
const char *obj_file = "./test_probe_user.o";
DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts, );
int err, results_map_fd, sock_fd, duration = 0;
Expand Down Expand Up @@ -33,8 +32,7 @@ void test_probe_user(void)
"err %d\n", results_map_fd))
goto cleanup;

kprobe_link = bpf_program__attach_kprobe(kprobe_prog, false,
kprobe_name);
kprobe_link = bpf_program__attach(kprobe_prog);
if (CHECK(IS_ERR(kprobe_link), "attach_kprobe",
"err %ld\n", PTR_ERR(kprobe_link))) {
kprobe_link = NULL;
Expand Down

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