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libbpf: Add support to set kprobe/uprobe attach mode

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By default, libbpf will attach the kprobe/uprobe BPF program in the
latest mode that supported by kernel. In this patch, we add the support
to let users manually attach kprobe/uprobe in legacy or perf mode.

There are 3 mode that supported by the kernel to attach kprobe/uprobe:

  LEGACY: create perf event in legacy way and don't use bpf_link
  PERF: create perf event with perf_event_open() and don't use bpf_link

Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Biao Jiang <benbjiang@tencent.com>
Link: create perf event with perf_event_open() and use bpf_link
Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com/
Link: https://lore.kernel.org/bpf/20230306064833.7932-2-imagedong@tencent.com

Users now can manually choose the mode with
bpf_program__attach_uprobe_opts()/bpf_program__attach_kprobe_opts().
This commit is contained in:
Menglong Dong
2023-03-06 14:48:31 +08:00
committed by Andrii Nakryiko
parent cf46d44f0a
commit cc7177624f
2 changed files with 84 additions and 14 deletions
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48
src/libbpf.c
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@@ -9724,6 +9724,7 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p
char errmsg[STRERR_BUFSIZE];
struct bpf_link_perf *link;
int prog_fd, link_fd = -1, err;
bool force_ioctl_attach;
if (!OPTS_VALID(opts, bpf_perf_event_opts))
return libbpf_err_ptr(-EINVAL);
@@ -9747,7 +9748,8 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p
link->link.dealloc = &bpf_link_perf_dealloc;
link->perf_event_fd = pfd;
if (kernel_supports(prog->obj, FEAT_PERF_LINK)) {
force_ioctl_attach = OPTS_GET(opts, force_ioctl_attach, false);
if (kernel_supports(prog->obj, FEAT_PERF_LINK) && !force_ioctl_attach) {
DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts,
.perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0));
@@ -10106,6 +10108,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
const struct bpf_kprobe_opts *opts)
{
DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
enum probe_attach_mode attach_mode;
char errmsg[STRERR_BUFSIZE];
char *legacy_probe = NULL;
struct bpf_link *link;
@@ -10116,11 +10119,32 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
if (!OPTS_VALID(opts, bpf_kprobe_opts))
return libbpf_err_ptr(-EINVAL);
attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);
retprobe = OPTS_GET(opts, retprobe, false);
offset = OPTS_GET(opts, offset, 0);
pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
legacy = determine_kprobe_perf_type() < 0;
switch (attach_mode) {
case PROBE_ATTACH_MODE_LEGACY:
legacy = true;
pe_opts.force_ioctl_attach = true;
break;
case PROBE_ATTACH_MODE_PERF:
if (legacy)
return libbpf_err_ptr(-ENOTSUP);
pe_opts.force_ioctl_attach = true;
break;
case PROBE_ATTACH_MODE_LINK:
if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))
return libbpf_err_ptr(-ENOTSUP);
break;
case PROBE_ATTACH_MODE_DEFAULT:
break;
default:
return libbpf_err_ptr(-EINVAL);
}
if (!legacy) {
pfd = perf_event_open_probe(false /* uprobe */, retprobe,
func_name, offset,
@@ -10852,6 +10876,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
const char *archive_path = NULL, *archive_sep = NULL;
char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL;
DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
enum probe_attach_mode attach_mode;
char full_path[PATH_MAX];
struct bpf_link *link;
size_t ref_ctr_off;
@@ -10862,6 +10887,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
if (!OPTS_VALID(opts, bpf_uprobe_opts))
return libbpf_err_ptr(-EINVAL);
attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);
retprobe = OPTS_GET(opts, retprobe, false);
ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);
pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
@@ -10903,6 +10929,26 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
}
legacy = determine_uprobe_perf_type() < 0;
switch (attach_mode) {
case PROBE_ATTACH_MODE_LEGACY:
legacy = true;
pe_opts.force_ioctl_attach = true;
break;
case PROBE_ATTACH_MODE_PERF:
if (legacy)
return libbpf_err_ptr(-ENOTSUP);
pe_opts.force_ioctl_attach = true;
break;
case PROBE_ATTACH_MODE_LINK:
if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))
return libbpf_err_ptr(-ENOTSUP);
break;
case PROBE_ATTACH_MODE_DEFAULT:
break;
default:
return libbpf_err_ptr(-EINVAL);
}
if (!legacy) {
pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
func_offset, pid, ref_ctr_off);