This patch utilizes bpf_program__set_private(), binding perf_probe_event with bpf program by private field.
Saving those information so 'perf record' knows which kprobe point a program should be attached. Since data in 'struct perf_probe_event' is build by 2 stages, tev_ready is used to mark whether the information (especially tevs) in 'struct perf_probe_event' is valid or not. It is false at first, and set to true by sync_bpf_program_pev(), which copy all pointers in original pev into a program specific memory region. sync_bpf_program_pev() is called after add_perf_probe_events() to make sure ready of data. Remove code which clean 'struct perf_probe_event' after bpf__probe() because pointers in pevs are copied to program's private field, calling clear_perf_probe_event() becomes unsafe. Signed-off-by: Wang Nan <wangn...@huawei.com> Cc: Arnaldo Carvalho de Melo <a...@redhat.com> Cc: Alexei Starovoitov <a...@plumgrid.com> Cc: Brendan Gregg <brendan.d.gr...@gmail.com> Cc: Daniel Borkmann <dan...@iogearbox.net> Cc: David Ahern <dsah...@gmail.com> Cc: He Kuang <heku...@huawei.com> Cc: Jiri Olsa <jo...@kernel.org> Cc: Kaixu Xia <xiaka...@huawei.com> Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com> Cc: Namhyung Kim <namhy...@kernel.org> Cc: Paul Mackerras <pau...@samba.org> Cc: Peter Zijlstra <a.p.zijls...@chello.nl> Cc: Zefan Li <lize...@huawei.com> Cc: pi3or...@163.com Link: http://lkml.kernel.org/n/1436445342-1402-21-git-send-email-wangn...@huawei.com [Splitted from a larger patch] --- tools/perf/util/bpf-loader.c | 90 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 88 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c index 435f52e..ae23f6f 100644 --- a/tools/perf/util/bpf-loader.c +++ b/tools/perf/util/bpf-loader.c @@ -30,9 +30,35 @@ DEFINE_PRINT_FN(debug, 1) static bool libbpf_initialized; +struct bpf_prog_priv { + /* + * If pev_ready is false, ppev pointes to a local memory which + * is only valid inside bpf__probe(). + * pev is valid only when pev_ready. + */ + bool pev_ready; + union { + struct perf_probe_event *ppev; + struct perf_probe_event pev; + }; +}; + +static void +bpf_prog_priv__clear(struct bpf_program *prog __maybe_unused, + void *_priv) +{ + struct bpf_prog_priv *priv = _priv; + + /* check if pev is initialized */ + if (priv && priv->pev_ready) + clear_perf_probe_event(&priv->pev); + free(priv); +} + static int config_bpf_program(struct bpf_program *prog, struct perf_probe_event *pev) { + struct bpf_prog_priv *priv = NULL; const char *config_str; int err; @@ -74,14 +100,58 @@ config_bpf_program(struct bpf_program *prog, struct perf_probe_event *pev) pr_debug("bpf: config '%s' is ok\n", config_str); + priv = calloc(1, sizeof(*priv)); + if (!priv) { + pr_debug("bpf: failed to alloc memory\n"); + err = -ENOMEM; + goto errout; + } + + /* + * At this very early stage, tevs inside pev are not ready. + * It becomes usable after add_perf_probe_events() is called. + * set pev_ready to false so further access read priv->ppev + * only. + */ + priv->pev_ready = false; + priv->ppev = pev; + + err = bpf_program__set_private(prog, priv, + bpf_prog_priv__clear); + if (err) { + pr_debug("bpf: set program private failed\n"); + err = -ENOMEM; + goto errout; + } return 0; errout: if (pev) clear_perf_probe_event(pev); + if (priv) + free(priv); return err; } +static int +sync_bpf_program_pev(struct bpf_program *prog) +{ + int err; + struct bpf_prog_priv *priv; + struct perf_probe_event *ppev; + + err = bpf_program__get_private(prog, (void **)&priv); + if (err || !priv || priv->pev_ready) { + pr_debug("Internal error: sync_bpf_program_pev\n"); + return -EINVAL; + } + + ppev = priv->ppev; + memcpy(&priv->pev, ppev, sizeof(*ppev)); + priv->pev_ready = true; + return 0; +} + int bpf__prepare_load(const char *filename) { struct bpf_object *obj; @@ -172,11 +242,27 @@ int bpf__probe(void) /* add_perf_probe_events return negative when fail */ if (err < 0) { pr_debug("bpf probe: failed to probe events\n"); + goto out; } else is_probed = true; + + /* + * After add_perf_probe_events, 'struct perf_probe_event' is ready. + * Until now copying program's priv->pev field and freeing + * the big array allocated before become safe. + */ + bpf_object__for_each_safe(obj, tmp) { + bpf_object__for_each_program(prog, obj) { + err = sync_bpf_program_pev(prog); + if (err) + goto out; + } + } out: - while (nr_events > 0) - clear_perf_probe_event(&pevs[--nr_events]); + /* + * Don't call clear_perf_probe_event() for entries of pevs: + * they are used by prog's private field. + */ free(pevs); return err < 0 ? err : 0; } -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
