From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6BDFFC433EF for ; Tue, 19 Jul 2022 08:24:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236378AbiGSIYU (ORCPT ); Tue, 19 Jul 2022 04:24:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230384AbiGSIYT (ORCPT ); Tue, 19 Jul 2022 04:24:19 -0400 Received: from mail-ej1-x631.google.com (mail-ej1-x631.google.com [IPv6:2a00:1450:4864:20::631]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 158DD2AC72; Tue, 19 Jul 2022 01:24:18 -0700 (PDT) Received: by mail-ej1-x631.google.com with SMTP id ez10so25702634ejc.13; Tue, 19 Jul 2022 01:24:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=/SIPwmw47aoCFUJf+ZzbIX6Q4nMBEnXalKToeS/fWng=; b=UPv0gKuMZO+Gc/PXu991fHK9k2kxWWNht/jZ5ygGsGY73ITUi2+nN+o9mACUMtTACu UbX0dQSnd5G8qLAuGNx9A9BLqvWQGdGnl5Qv4mtFODOi09MnJFA142MIVChzyC+NumJX qhjmz0jLDJLyqhnIxkA6XJqn0ulin2oXQo0S8WnKRilMMFRpAEREQuJScvn6foFRh8WJ ZXJa/GElPhpE+YGTQVD9LgMt1IRutsuZonh+kdwM8DNJIG+nyVNcX5tUSqpEtINfCU5j xFAZxZrZEh5pY9dVCpK4nA8M2xVJWMhb2r0HrgplO2oHxYUhIsiJFmzWKMX5OOjUXeiY PtxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=/SIPwmw47aoCFUJf+ZzbIX6Q4nMBEnXalKToeS/fWng=; b=BHzn0AHLkfapP1+cb+49nuFjvU5bIZ54xR0yy5NylKF6J0y/vnfwsjOQ5Dee1CYcKt fLEDKwfJeTlHtN5a4L1mAYVlPCWiyFTMspcYq6kyUzI16/oio99XSOvHAEXBNikyelvs NQZSWP1TGKzGb3Pwj4jwUDvA4UMtssGWpY+EhM9eyDX8eNSiwv6ufBQNa2uxDYPC2aWc flINWIA+EpKP6mHgVjoDEKBAAlXZW/j1OxURZidDknifdxzFZoVh7HnYuVtIf91010iV 1rPXlPL+rItA3buaevLYznqEfCq5MrDzcaz8PXxA8+9XspXN0tw+dBINd6xNpDf5Lg3O pBeg== X-Gm-Message-State: AJIora89u3o0UPC+DHqREgl8uMBxUXz+ZkwBJSQaEl5tmZTBeOG3VxJT VSCrUSAljX8Z7dmYCzYyt+4= X-Google-Smtp-Source: AGRyM1vhnau/Abv5mHDURRwuOnzF3g/SXIcnCCtgO2pBc//7jZW25ou2vaLo5quzRXcgrSPmONnJUg== X-Received: by 2002:a17:906:cc45:b0:72b:313b:f3ee with SMTP id mm5-20020a170906cc4500b0072b313bf3eemr28477978ejb.362.1658219056611; Tue, 19 Jul 2022 01:24:16 -0700 (PDT) Received: from krava ([193.85.244.190]) by smtp.gmail.com with ESMTPSA id r18-20020a17090609d200b006feed200464sm6351476eje.131.2022.07.19.01.24.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jul 2022 01:24:15 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 19 Jul 2022 10:24:12 +0200 To: Jiri Olsa Cc: Martynas Pumputis , Andrii Nakryiko , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Networking , bpf , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Masami Hiramatsu , Yutaro Hayakawa , Peter Zijlstra Subject: Re: [PATCH RFC bpf-next 4/4] selftests/bpf: Fix kprobe get_func_ip tests for CONFIG_X86_KERNEL_IBT Message-ID: References: <20220705190308.1063813-1-jolsa@kernel.org> <20220705190308.1063813-5-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Jul 18, 2022 at 02:48:46PM +0200, Jiri Olsa wrote: > On Mon, Jul 18, 2022 at 02:09:54PM +0300, Martynas Pumputis wrote: > > > > > > On 7/18/22 00:43, Jiri Olsa wrote: > > > On Fri, Jul 08, 2022 at 12:16:35AM +0200, Jiri Olsa wrote: > > > > On Tue, Jul 05, 2022 at 10:29:17PM -0700, Andrii Nakryiko wrote: > > > > > On Tue, Jul 5, 2022 at 12:04 PM Jiri Olsa wrote: > > > > > > > > > > > > The kprobe can be placed anywhere and user must be aware > > > > > > of the underlying instructions. Therefore fixing just > > > > > > the bpf program to 'fix' the address to match the actual > > > > > > function address when CONFIG_X86_KERNEL_IBT is enabled. > > > > > > > > > > > > Signed-off-by: Jiri Olsa > > > > > > --- > > > > > > tools/testing/selftests/bpf/progs/get_func_ip_test.c | 7 +++++-- > > > > > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > > > > > > > > > > diff --git a/tools/testing/selftests/bpf/progs/get_func_ip_test.c b/tools/testing/selftests/bpf/progs/get_func_ip_test.c > > > > > > index a587aeca5ae0..220d56b7c1dc 100644 > > > > > > --- a/tools/testing/selftests/bpf/progs/get_func_ip_test.c > > > > > > +++ b/tools/testing/selftests/bpf/progs/get_func_ip_test.c > > > > > > @@ -2,6 +2,7 @@ > > > > > > #include > > > > > > #include > > > > > > #include > > > > > > +#include > > > > > > > > > > > > char _license[] SEC("license") = "GPL"; > > > > > > > > > > > > @@ -13,6 +14,8 @@ extern const void bpf_modify_return_test __ksym; > > > > > > extern const void bpf_fentry_test6 __ksym; > > > > > > extern const void bpf_fentry_test7 __ksym; > > > > > > > > > > > > +extern bool CONFIG_X86_KERNEL_IBT __kconfig __weak; > > > > > > + > > > > > > __u64 test1_result = 0; > > > > > > SEC("fentry/bpf_fentry_test1") > > > > > > int BPF_PROG(test1, int a) > > > > > > @@ -37,7 +40,7 @@ __u64 test3_result = 0; > > > > > > SEC("kprobe/bpf_fentry_test3") > > > > > > int test3(struct pt_regs *ctx) > > > > > > { > > > > > > - __u64 addr = bpf_get_func_ip(ctx); > > > > > > + __u64 addr = bpf_get_func_ip(ctx) - (CONFIG_X86_KERNEL_IBT ? 4 : 0); > > > > > > > > > > so for kprobe bpf_get_func_ip() gets an address with 5 byte > > > > > compensation for `call __fentry__`, but not for endr? Why can't we > > > > > compensate for endbr inside the kernel code as well? I'd imagine we > > > > > either do no compensation (and thus we get &bpf_fentry_test3+5 or > > > > > &bpf_fentry_test3+9, depending on CONFIG_X86_KERNEL_IBT) or full > > > > > compensation (and thus always get &bpf_fentry_test3), but this > > > > > in-between solution seems to be the worst of both worlds?... > > > > > > > > hm rigth, I guess we should be able to do that in bpf_get_func_ip, > > > > I'll check > > > > > > sorry for late follow up.. > > > > > > so the problem is that you can place kprobe anywhere in the function > > > (on instruction boundary) but the IBT adjustment of kprobe address is > > > made only if it's at the function entry and there's endbr instruction > > > > To add more fun to the issue, not all non-inlined functions get endbr64. For > > example "skb_release_head_state()" does, while "skb_free_head()" doesn't. > > ah great.. thanks for info, will check I checked with Peter and yes the endbr does not need to be there IBT is 'Indirect Branch Tracking' ENDBR needs to be at the target for "JMP *%reg" and "CALL *%reg" direct call/jmp don't need anything specal so we will need to hold the +4 info somewhere for each address and use that in get_func_ip helper or perhaps we could read previous instruction and check if the previous instruction is endbr with check like: if (is_endbr(*(u32 *)(addr - 4))) addr -= 4 jirka