[bpf-next,v4,1/3] libbpf: add support to set kprobe/uprobe attach mode
Commit Message
From: Menglong Dong <imagedong@tencent.com>
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
LINK: create perf event with perf_event_open() and use bpf_link
Users now can manually choose the mode with
bpf_program__attach_uprobe_opts()/bpf_program__attach_kprobe_opts().
Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com/
Reviewed-by: Biao Jiang <benbjiang@tencent.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
v4:
- rename eBPF to BPF in the doc
- use OPTS_GET() to get the value of 'force_ioctl_attach'
- error out on attach mode is not supported
v2:
- rename no_link to force_ioctl_attach
- rename probe_mode to probe_attach_mode
- add more doc for probe_attach_mode
- return -ENOTSUP when necessray in bpf_program__attach_uprobe_opts and
bpf_program__attach_kprobe_opts
---
tools/lib/bpf/libbpf.c | 47 +++++++++++++++++++++++++++++++++++++++++-
tools/lib/bpf/libbpf.h | 31 +++++++++++++++++++++++++---
2 files changed, 74 insertions(+), 4 deletions(-)
Comments
On Sun, Mar 5, 2023 at 10:48 PM <menglong8.dong@gmail.com> wrote:
>
> From: Menglong Dong <imagedong@tencent.com>
>
> 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
> LINK: create perf event with perf_event_open() and use bpf_link
>
> Users now can manually choose the mode with
> bpf_program__attach_uprobe_opts()/bpf_program__attach_kprobe_opts().
>
> Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com/
> Reviewed-by: Biao Jiang <benbjiang@tencent.com>
> Signed-off-by: Menglong Dong <imagedong@tencent.com>
> ---
I fixed few small issues I pointed out below and applied to bpf-next. Thanks!
> v4:
> - rename eBPF to BPF in the doc
> - use OPTS_GET() to get the value of 'force_ioctl_attach'
> - error out on attach mode is not supported
> v2:
> - rename no_link to force_ioctl_attach
> - rename probe_mode to probe_attach_mode
> - add more doc for probe_attach_mode
> - return -ENOTSUP when necessray in bpf_program__attach_uprobe_opts and
> bpf_program__attach_kprobe_opts
> ---
> tools/lib/bpf/libbpf.c | 47 +++++++++++++++++++++++++++++++++++++++++-
> tools/lib/bpf/libbpf.h | 31 +++++++++++++++++++++++++---
> 2 files changed, 74 insertions(+), 4 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index dacaae31b76a..77df4d275d22 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -9747,7 +9747,8 @@ 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)) {
> + if (kernel_supports(prog->obj, FEAT_PERF_LINK) && !OPTS_GET(opts, force_ioctl_attach,
> + false)) {
too ugly, I added local variable for OPTS_GET() result
> DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts,
> .perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0));
>
> @@ -10106,6 +10107,7 @@ 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 +10118,32 @@ 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(-ENOTSUP);
this should have been -EINVAL, I changed it; same for another instance below
> + }
> +
> if (!legacy) {
> pfd = perf_event_open_probe(false /* uprobe */, retprobe,
> func_name, offset,
[...]
@@ -9747,7 +9747,8 @@ 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)) {
+ if (kernel_supports(prog->obj, FEAT_PERF_LINK) && !OPTS_GET(opts, force_ioctl_attach,
+ false)) {
DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts,
.perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0));
@@ -10106,6 +10107,7 @@ 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 +10118,32 @@ 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(-ENOTSUP);
+ }
+
if (!legacy) {
pfd = perf_event_open_probe(false /* uprobe */, retprobe,
func_name, offset,
@@ -10852,6 +10875,7 @@ 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 +10886,7 @@ 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 +10928,26 @@ 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(-ENOTSUP);
+ }
+
if (!legacy) {
pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
func_offset, pid, ref_ctr_off);
@@ -451,8 +451,11 @@ struct bpf_perf_event_opts {
size_t sz;
/* custom user-provided value fetchable through bpf_get_attach_cookie() */
__u64 bpf_cookie;
+ /* don't use BPF link when attach BPF program */
+ bool force_ioctl_attach;
+ size_t :0;
};
-#define bpf_perf_event_opts__last_field bpf_cookie
+#define bpf_perf_event_opts__last_field force_ioctl_attach
LIBBPF_API struct bpf_link *
bpf_program__attach_perf_event(const struct bpf_program *prog, int pfd);
@@ -461,6 +464,24 @@ LIBBPF_API struct bpf_link *
bpf_program__attach_perf_event_opts(const struct bpf_program *prog, int pfd,
const struct bpf_perf_event_opts *opts);
+
+/**
+ * enum probe_attach_mode - the mode to attach kprobe/uprobe
+ *
+ * force libbpf to attach kprobe/uprobe in specific mode, -ENOTSUP will
+ * be returned if it is not supported by the kernel.
+ */
+enum probe_attach_mode {
+ /* attach probe in latest supported mode by kernel */
+ PROBE_ATTACH_MODE_DEFAULT = 0,
+ /* attach probe in legacy mode, using debugfs/tracefs */
+ PROBE_ATTACH_MODE_LEGACY,
+ /* create perf event with perf_event_open() syscall */
+ PROBE_ATTACH_MODE_PERF,
+ /* attach probe with BPF link */
+ PROBE_ATTACH_MODE_LINK,
+};
+
struct bpf_kprobe_opts {
/* size of this struct, for forward/backward compatiblity */
size_t sz;
@@ -470,9 +491,11 @@ struct bpf_kprobe_opts {
size_t offset;
/* kprobe is return probe */
bool retprobe;
+ /* kprobe attach mode */
+ enum probe_attach_mode attach_mode;
size_t :0;
};
-#define bpf_kprobe_opts__last_field retprobe
+#define bpf_kprobe_opts__last_field attach_mode
LIBBPF_API struct bpf_link *
bpf_program__attach_kprobe(const struct bpf_program *prog, bool retprobe,
@@ -570,9 +593,11 @@ struct bpf_uprobe_opts {
* binary_path.
*/
const char *func_name;
+ /* uprobe attach mode */
+ enum probe_attach_mode attach_mode;
size_t :0;
};
-#define bpf_uprobe_opts__last_field func_name
+#define bpf_uprobe_opts__last_field attach_mode
/**
* @brief **bpf_program__attach_uprobe()** attaches a BPF program