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Wed, 09 Feb 2022 07:01:45 -0800 (PST) Received: from krava ([2a00:102a:5010:3235:47fb:6193:ef68:761d]) by smtp.gmail.com with ESMTPSA id s16sm2227842edt.91.2022.02.09.07.01.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Feb 2022 07:01:44 -0800 (PST) Date: Wed, 9 Feb 2022 16:01:41 +0100 From: Jiri Olsa To: Andrii Nakryiko Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Masami Hiramatsu , Networking , bpf , lkml , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Steven Rostedt Subject: Re: [PATCH 2/8] bpf: Add bpf_get_func_ip kprobe helper for fprobe link Message-ID: References: <20220202135333.190761-1-jolsa@kernel.org> <20220202135333.190761-3-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 07, 2022 at 10:59:18AM -0800, Andrii Nakryiko wrote: > On Wed, Feb 2, 2022 at 5:53 AM Jiri Olsa wrote: > > > > Adding support to call get_func_ip_fprobe helper from kprobe > > programs attached by fprobe link. > > > > Also adding support to inline it, because it's single load > > instruction. > > > > Signed-off-by: Jiri Olsa > > --- > > kernel/bpf/verifier.c | 19 ++++++++++++++++++- > > kernel/trace/bpf_trace.c | 16 +++++++++++++++- > > 2 files changed, 33 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index 1ae41d0cf96c..a745ded00635 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c > > @@ -13625,7 +13625,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env) > > continue; > > } > > > > - /* Implement bpf_get_func_ip inline. */ > > + /* Implement tracing bpf_get_func_ip inline. */ > > if (prog_type == BPF_PROG_TYPE_TRACING && > > insn->imm == BPF_FUNC_get_func_ip) { > > /* Load IP address from ctx - 16 */ > > @@ -13640,6 +13640,23 @@ static int do_misc_fixups(struct bpf_verifier_env *env) > > continue; > > } > > > > + /* Implement kprobe/fprobe bpf_get_func_ip inline. */ > > + if (prog_type == BPF_PROG_TYPE_KPROBE && > > + eatype == BPF_TRACE_FPROBE && > > + insn->imm == BPF_FUNC_get_func_ip) { > > + /* Load IP address from ctx (struct pt_regs) ip */ > > + insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, > > + offsetof(struct pt_regs, ip)); > > Isn't this architecture-specific? I'm starting to dislike this ugh, it is.. I'm not sure we want #ifdef CONFIG_X86 in here, or some arch_* specific function? jirka > inlining whole more and more. It's just a complication in verifier > without clear real-world benefits. We are clearly prematurely > optimizing here. In practice you'll just call bpf_get_func_ip() once > and that's it. Function call overhead will be negligible compare to > other *userful* work you'll be doing in your BPF program. > > > > + > > + new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 1); > > + if (!new_prog) > > + return -ENOMEM; > > + > > + env->prog = prog = new_prog; > > + insn = new_prog->insnsi + i + delta; > > + continue; > > + } > > + > > patch_call_imm: > > fn = env->ops->get_func_proto(insn->imm, env->prog); > > /* all functions that have prototype and verifier allowed > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > > index a2024ba32a20..28e59e31e3db 100644 > > --- a/kernel/trace/bpf_trace.c > > +++ b/kernel/trace/bpf_trace.c > > @@ -1036,6 +1036,19 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = { > > .arg1_type = ARG_PTR_TO_CTX, > > }; > > > > +BPF_CALL_1(bpf_get_func_ip_fprobe, struct pt_regs *, regs) > > +{ > > + /* This helper call is inlined by verifier. */ > > + return regs->ip; > > +} > > + > > +static const struct bpf_func_proto bpf_get_func_ip_proto_fprobe = { > > + .func = bpf_get_func_ip_fprobe, > > + .gpl_only = false, > > + .ret_type = RET_INTEGER, > > + .arg1_type = ARG_PTR_TO_CTX, > > +}; > > + > > BPF_CALL_1(bpf_get_attach_cookie_trace, void *, ctx) > > { > > struct bpf_trace_run_ctx *run_ctx; > > @@ -1279,7 +1292,8 @@ kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > > return &bpf_override_return_proto; > > #endif > > case BPF_FUNC_get_func_ip: > > - return &bpf_get_func_ip_proto_kprobe; > > + return prog->expected_attach_type == BPF_TRACE_FPROBE ? > > + &bpf_get_func_ip_proto_fprobe : &bpf_get_func_ip_proto_kprobe; > > case BPF_FUNC_get_attach_cookie: > > return &bpf_get_attach_cookie_proto_trace; > > default: > > -- > > 2.34.1 > >