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libbpf: Add uprobe multi link support to bpf_program__attach_usdt

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Adding support for usdt_manager_attach_usdt to use uprobe_multi
link to attach to usdt probes.

The uprobe_multi support is detected before the usdt program is
loaded and its expected_attach_type is set accordingly.

If uprobe_multi support is detected the usdt_manager_attach_usdt
gathers uprobes info and calls bpf_program__attach_uprobe to
create all needed uprobes.

If uprobe_multi support is not detected the old behaviour stays.

Also adding usdt.s program section for sleepable usdt probes.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-18-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Jiri Olsa 2023-08-09 10:34:29 +02:00 committed by Alexei Starovoitov
parent 7e1b468123
commit 5902da6d8a
2 changed files with 82 additions and 17 deletions
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13
tools/lib/bpf/libbpf.c
View file

@ -367,6 +367,8 @@ enum sec_def_flags {
SEC_SLEEPABLE = 8,
/* BPF program support non-linear XDP buffer */
SEC_XDP_FRAGS = 16,
/* Setup proper attach type for usdt probes. */
SEC_USDT = 32,
};
struct bpf_sec_def {
@ -6828,6 +6830,10 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog,
if (prog->type == BPF_PROG_TYPE_XDP && (def & SEC_XDP_FRAGS))
opts->prog_flags |= BPF_F_XDP_HAS_FRAGS;
/* special check for usdt to use uprobe_multi link */
if ((def & SEC_USDT) && kernel_supports(prog->obj, FEAT_UPROBE_MULTI_LINK))
prog->expected_attach_type = BPF_TRACE_UPROBE_MULTI;
if ((def & SEC_ATTACH_BTF) && !prog->attach_btf_id) {
int btf_obj_fd = 0, btf_type_id = 0, err;
const char *attach_name;
@ -6896,7 +6902,6 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
if (!insns || !insns_cnt)
return -EINVAL;
load_attr.expected_attach_type = prog->expected_attach_type;
if (kernel_supports(obj, FEAT_PROG_NAME))
prog_name = prog->name;
load_attr.attach_prog_fd = prog->attach_prog_fd;
@ -6932,6 +6937,9 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
insns_cnt = prog->insns_cnt;
}
/* allow prog_prepare_load_fn to change expected_attach_type */
load_attr.expected_attach_type = prog->expected_attach_type;
if (obj->gen_loader) {
bpf_gen__prog_load(obj->gen_loader, prog->type, prog->name,
license, insns, insns_cnt, &load_attr,
@ -8759,7 +8767,8 @@ static const struct bpf_sec_def section_defs[] = {
SEC_DEF("uretprobe.multi.s+", KPROBE, BPF_TRACE_UPROBE_MULTI, SEC_SLEEPABLE, attach_uprobe_multi),
SEC_DEF("ksyscall+", KPROBE, 0, SEC_NONE, attach_ksyscall),
SEC_DEF("kretsyscall+", KPROBE, 0, SEC_NONE, attach_ksyscall),
SEC_DEF("usdt+", KPROBE, 0, SEC_NONE, attach_usdt),
SEC_DEF("usdt+", KPROBE, 0, SEC_USDT, attach_usdt),
SEC_DEF("usdt.s+", KPROBE, 0, SEC_USDT | SEC_SLEEPABLE, attach_usdt),
SEC_DEF("tc/ingress", SCHED_CLS, BPF_TCX_INGRESS, SEC_NONE), /* alias for tcx */
SEC_DEF("tc/egress", SCHED_CLS, BPF_TCX_EGRESS, SEC_NONE), /* alias for tcx */
SEC_DEF("tcx/ingress", SCHED_CLS, BPF_TCX_INGRESS, SEC_NONE),

86
tools/lib/bpf/usdt.c
View file

@ -250,6 +250,7 @@ struct usdt_manager {
bool has_bpf_cookie;
bool has_sema_refcnt;
bool has_uprobe_multi;
};
struct usdt_manager *usdt_manager_new(struct bpf_object *obj)
@ -284,6 +285,11 @@ struct usdt_manager *usdt_manager_new(struct bpf_object *obj)
*/
man->has_sema_refcnt = faccessat(AT_FDCWD, ref_ctr_sysfs_path, F_OK, AT_EACCESS) == 0;
/*
* Detect kernel support for uprobe multi link to be used for attaching
* usdt probes.
*/
man->has_uprobe_multi = kernel_supports(obj, FEAT_UPROBE_MULTI_LINK);
return man;
}
@ -808,6 +814,8 @@ struct bpf_link_usdt {
long abs_ip;
struct bpf_link *link;
} *uprobes;
struct bpf_link *multi_link;
};
static int bpf_link_usdt_detach(struct bpf_link *link)
@ -816,6 +824,9 @@ static int bpf_link_usdt_detach(struct bpf_link *link)
struct usdt_manager *man = usdt_link->usdt_man;
int i;
bpf_link__destroy(usdt_link->multi_link);
/* When having multi_link, uprobe_cnt is 0 */
for (i = 0; i < usdt_link->uprobe_cnt; i++) {
/* detach underlying uprobe link */
bpf_link__destroy(usdt_link->uprobes[i].link);
@ -946,11 +957,13 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
const char *usdt_provider, const char *usdt_name,
__u64 usdt_cookie)
{
unsigned long *offsets = NULL, *ref_ctr_offsets = NULL;
int i, err, spec_map_fd, ip_map_fd;
LIBBPF_OPTS(bpf_uprobe_opts, opts);
struct hashmap *specs_hash = NULL;
struct bpf_link_usdt *link = NULL;
struct usdt_target *targets = NULL;
__u64 *cookies = NULL;
struct elf_fd elf_fd;
size_t target_cnt;
@ -997,10 +1010,21 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
link->link.detach = &bpf_link_usdt_detach;
link->link.dealloc = &bpf_link_usdt_dealloc;
link->uprobes = calloc(target_cnt, sizeof(*link->uprobes));
if (!link->uprobes) {
err = -ENOMEM;
goto err_out;
if (man->has_uprobe_multi) {
offsets = calloc(target_cnt, sizeof(*offsets));
cookies = calloc(target_cnt, sizeof(*cookies));
ref_ctr_offsets = calloc(target_cnt, sizeof(*ref_ctr_offsets));
if (!offsets || !ref_ctr_offsets || !cookies) {
err = -ENOMEM;
goto err_out;
}
} else {
link->uprobes = calloc(target_cnt, sizeof(*link->uprobes));
if (!link->uprobes) {
err = -ENOMEM;
goto err_out;
}
}
for (i = 0; i < target_cnt; i++) {
@ -1041,20 +1065,48 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
goto err_out;
}
opts.ref_ctr_offset = target->sema_off;
opts.bpf_cookie = man->has_bpf_cookie ? spec_id : 0;
uprobe_link = bpf_program__attach_uprobe_opts(prog, pid, path,
target->rel_ip, &opts);
err = libbpf_get_error(uprobe_link);
if (err) {
pr_warn("usdt: failed to attach uprobe #%d for '%s:%s' in '%s': %d\n",
i, usdt_provider, usdt_name, path, err);
if (man->has_uprobe_multi) {
offsets[i] = target->rel_ip;
ref_ctr_offsets[i] = target->sema_off;
cookies[i] = spec_id;
} else {
opts.ref_ctr_offset = target->sema_off;
opts.bpf_cookie = man->has_bpf_cookie ? spec_id : 0;
uprobe_link = bpf_program__attach_uprobe_opts(prog, pid, path,
target->rel_ip, &opts);
err = libbpf_get_error(uprobe_link);
if (err) {
pr_warn("usdt: failed to attach uprobe #%d for '%s:%s' in '%s': %d\n",
i, usdt_provider, usdt_name, path, err);
goto err_out;
}
link->uprobes[i].link = uprobe_link;
link->uprobes[i].abs_ip = target->abs_ip;
link->uprobe_cnt++;
}
}
if (man->has_uprobe_multi) {
LIBBPF_OPTS(bpf_uprobe_multi_opts, opts_multi,
.ref_ctr_offsets = ref_ctr_offsets,
.offsets = offsets,
.cookies = cookies,
.cnt = target_cnt,
);
link->multi_link = bpf_program__attach_uprobe_multi(prog, pid, path,
NULL, &opts_multi);
if (!link->multi_link) {
err = -errno;
pr_warn("usdt: failed to attach uprobe multi for '%s:%s' in '%s': %d\n",
usdt_provider, usdt_name, path, err);
goto err_out;
}
link->uprobes[i].link = uprobe_link;
link->uprobes[i].abs_ip = target->abs_ip;
link->uprobe_cnt++;
free(offsets);
free(ref_ctr_offsets);
free(cookies);
}
free(targets);
@ -1063,6 +1115,10 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
return &link->link;
err_out:
free(offsets);
free(ref_ctr_offsets);
free(cookies);
if (link)
bpf_link__destroy(&link->link);
free(targets);