This patch generates prologue for each 'struct probe_trace_event' for fetching arguments for BPF programs.
After bpf__probe(), iterate over each programs to check whether prologue is required. If none of 'struct perf_probe_event' a program will attach to has at least one argument, simply skip preprocessor hooking. For those who prologue is required, calls bpf__gen_prologue() and paste original instruction after prologue. Signed-off-by: Wang Nan <wangn...@huawei.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 Cc: Arnaldo Carvalho de Melo <a...@redhat.com> Link: http://lkml.kernel.org/n/ebpf-6yw9eg0ej3l4jnqhinngk...@git.kernel.org --- tools/perf/util/bpf-loader.c | 120 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 119 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c index f4c690f..c363907 100644 --- a/tools/perf/util/bpf-loader.c +++ b/tools/perf/util/bpf-loader.c @@ -5,11 +5,14 @@ * Copyright (C) 2015 Huawei Inc. */ +#include <linux/bpf.h> #include <bpf/libbpf.h> #include <linux/err.h> #include "perf.h" #include "debug.h" #include "bpf-loader.h" +#include "bpf-prologue.h" +#include "llvm-utils.h" #include "probe-event.h" #include "probe-finder.h" // for MAX_PROBES #include "llvm-utils.h" @@ -32,6 +35,8 @@ DEFINE_PRINT_FN(debug, 1) struct bpf_prog_priv { struct perf_probe_event pev; + bool need_prologue; + struct bpf_insn *insns_buf; }; struct bpf_object * @@ -98,6 +103,7 @@ bpf_prog_priv__clear(struct bpf_program *prog __maybe_unused, struct bpf_prog_priv *priv = _priv; cleanup_perf_probe_events(&priv->pev, 1); + zfree(&priv->insns_buf); free(priv); } @@ -189,6 +195,102 @@ static int bpf__prepare_probe(void) return err; } +static int +preproc_gen_prologue(struct bpf_program *prog, int n, + struct bpf_insn *orig_insns, int orig_insns_cnt, + struct bpf_prog_prep_result *res) +{ + struct probe_trace_event *tev; + struct perf_probe_event *pev; + struct bpf_prog_priv *priv; + struct bpf_insn *buf; + size_t prologue_cnt = 0; + int err; + + err = bpf_program__get_private(prog, (void **)&priv); + if (err || !priv) + goto errout; + + pev = &priv->pev; + + if (n < 0 || n >= pev->ntevs) + goto errout; + + tev = &pev->tevs[n]; + + buf = priv->insns_buf; + err = bpf__gen_prologue(tev->args, tev->nargs, + buf, &prologue_cnt, + BPF_MAXINSNS - orig_insns_cnt); + if (err) { + const char *title; + + title = bpf_program__title(prog, false); + if (!title) + title = "[unknown]"; + + pr_debug("Failed to generate prologue for program %s\n", + title); + return err; + } + + memcpy(&buf[prologue_cnt], orig_insns, + sizeof(struct bpf_insn) * orig_insns_cnt); + + res->new_insn_ptr = buf; + res->new_insn_cnt = prologue_cnt + orig_insns_cnt; + res->pfd = NULL; + return 0; + +errout: + pr_debug("Internal error in preproc_gen_prologue\n"); + return -EINVAL; +} + +static int hook_load_preprocessor(struct bpf_program *prog) +{ + struct perf_probe_event *pev; + struct bpf_prog_priv *priv; + bool need_prologue = false; + int err, i; + + err = bpf_program__get_private(prog, (void **)&priv); + if (err || !priv) { + pr_debug("Internal error when hook preprocessor\n"); + return -EINVAL; + } + + pev = &priv->pev; + for (i = 0; i < pev->ntevs; i++) { + struct probe_trace_event *tev = &pev->tevs[i]; + + if (tev->nargs > 0) { + need_prologue = true; + break; + } + } + + /* + * Since all tev doesn't have argument, we don't need generate + * prologue. + */ + if (!need_prologue) { + priv->need_prologue = false; + return 0; + } + + priv->need_prologue = true; + priv->insns_buf = malloc(sizeof(struct bpf_insn) * BPF_MAXINSNS); + if (!priv->insns_buf) { + pr_debug("No enough memory: alloc insns_buf failed\n"); + return -ENOMEM; + } + + err = bpf_program__set_prep(prog, pev->ntevs, + preproc_gen_prologue); + return err; +} + int bpf__probe(struct bpf_object *obj) { int err = 0; @@ -223,6 +325,18 @@ int bpf__probe(struct bpf_object *obj) pr_debug("bpf_probe: failed to apply perf probe events"); goto out; } + + /* + * After probing, let's consider prologue, which + * adds program fetcher to BPF programs. + * + * hook_load_preprocessorr() hooks pre-processor + * to bpf_program, let it generate prologue + * dynamically during loading. + */ + err = hook_load_preprocessor(prog); + if (err) + goto out; } out: return err < 0 ? err : 0; @@ -306,7 +420,11 @@ int bpf__foreach_tev(struct bpf_object *obj, for (i = 0; i < pev->ntevs; i++) { tev = &pev->tevs[i]; - fd = bpf_program__fd(prog); + if (priv->need_prologue) + fd = bpf_program__nth_fd(prog, i); + else + fd = bpf_program__fd(prog); + if (fd < 0) { pr_debug("bpf: failed to get file descriptor\n"); return fd; -- 1.8.3.4 -- 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/
