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charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-1.7 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RDNS_NONE, SPF_HELO_NONE,T_SCC_BODY_TEXT_LINE autolearn=no 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 Wed, Feb 09, 2022 at 08:05:05AM -0800, Andrii Nakryiko wrote: > On Wed, Feb 9, 2022 at 7:01 AM Jiri Olsa wrote: > > > > 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? > > > So not inlining it isn't even considered? this function will be called > once or at most a few times per BPF program invocation. Anyone calling > it in a tight loop is going to use it very-very suboptimally (and even > then useful program logic will dominate). There is no point in > inlining it. I agree that given its usage pattern there won't be too much gain, on the other hand it's simple verifier code changing call/load/ret into simple load, so I thought why not.. also there are just few helpers we can inline so easily but yea.. I can't think of any sane usage of this helper that inlining would matter for.. which doesn't mean there isn't one ;-) jirka > > > > > 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 > > > >