From: Menglong Dong <imagedong@xxxxxxxxxxx> By default, libbpf will attach the kprobe/uprobe eBPF 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@xxxxxxxxxxx/ Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx> --- 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 | 42 +++++++++++++++++++++++++++++++++++++++++- tools/lib/bpf/libbpf.h | 31 ++++++++++++++++++++++++++++--- 2 files changed, 69 insertions(+), 4 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 35a698eb825d..724ee5fab839 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -9747,7 +9747,7 @@ 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->force_ioctl_attach) { DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts, .perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0)); @@ -10106,6 +10106,7 @@ 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 +10117,30 @@ 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 (!kernel_supports(prog->obj, FEAT_PERF_LINK)) + return libbpf_err_ptr(-ENOTSUP); + break; + default: + break; + } + if (!legacy) { pfd = perf_event_open_probe(false /* uprobe */, retprobe, func_name, offset, @@ -10774,6 +10794,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, { DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts); char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL; + enum probe_attach_mode attach_mode; char full_binary_path[PATH_MAX]; struct bpf_link *link; size_t ref_ctr_off; @@ -10784,6 +10805,7 @@ 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); @@ -10812,6 +10834,24 @@ 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 (!kernel_supports(prog->obj, FEAT_PERF_LINK)) + return libbpf_err_ptr(-ENOTSUP); + break; + default: + break; + } + if (!legacy) { pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path, func_offset, pid, ref_ctr_off); diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 2efd80f6f7b9..ef8f68da42f9 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -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 eBPF 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 */ + 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 -- 2.39.0
