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 DA7A6C433EF for ; Mon, 18 Jul 2022 12:48:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233933AbiGRMsy (ORCPT ); Mon, 18 Jul 2022 08:48:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39416 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230193AbiGRMsx (ORCPT ); Mon, 18 Jul 2022 08:48:53 -0400 Received: from mail-ej1-x632.google.com (mail-ej1-x632.google.com [IPv6:2a00:1450:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A13CE274; Mon, 18 Jul 2022 05:48:51 -0700 (PDT) Received: by mail-ej1-x632.google.com with SMTP id bp15so21020462ejb.6; Mon, 18 Jul 2022 05:48:51 -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=TeGVCUHeLxV7GRevtfvM+qomfGbRC+tXZ9uiMLV6+TY=; b=njIbtwRABHwo1EuVlDmBZl5/FfMEVieI0PWSxOowMr14u+vgbwUdzACh1FX0Z5QT3I NwlS4Wvt3WPDSo5+c90fkGtVn4fxYFvOoTGGw7mIVewnJvOZndlPGb6yUx/4qwDBmtvc FflvOm+utwIey+OP2PLkl90+gv4M/nievVIhkYfVNQFfwaQyG+ATBsmOxPtfGqshXRe+ Ass+P5pjmix/lZf0A7RnNHFyVYPGm+al2LZKZfcAr6BwogORogjpVRjte0NdvjBtWl2G bqcvCu+jgtOnXnl2kj5HFnBiJqhWYE2CvQZFeXqB6JK0b3wy7p8xYDAdR7tWHL6HVKye 7/GQ== 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=TeGVCUHeLxV7GRevtfvM+qomfGbRC+tXZ9uiMLV6+TY=; b=bXZMlvS+5eGxJT2F4qa1YzdJupP/UCfTesTNW9qyHh6MSPmXCsKhLqr1QkY6Q4Lz7r 2r72wslnO80P68pCbZWV4zcCePp+eS7mBuKy/sBn7JlPcHlSpzb0YOt1bV8LZE67SwPd aNq2mopT9NxFkdT9CNTelG2OjlqeEC60fweLs5iIMH5yXH0GPATGJObqbPRBnQX/UGVE xQLsLiFqf4UT97Emw9qEONGlK6YzJHrrfZutFGL4w67RfyWHgEkvgkadHnwiXSzBMjM0 OaJZsCc7uDbAUDRgq+hOm/GHJRqZZEcOtCXdXYIknCDRYPHbElgw14SQHL7yw4wYr5BD dyug== X-Gm-Message-State: AJIora8dtXLQ3/fwdkujGFIlsYqTRpLTWF0zR6H9bx8UlPRT0p5OWwgT W/PtbRESJmK9BFbA0qyrPkc= X-Google-Smtp-Source: AGRyM1v5W3XVAP+3An41B0subOY/ynUHBsIavZ/hmJ7cpd6pECSZfwhJE5T7jKBSQ6hbg4w6JUffTg== X-Received: by 2002:a17:906:4785:b0:72e:dd6c:1ba1 with SMTP id cw5-20020a170906478500b0072edd6c1ba1mr20369468ejc.712.1658148529973; Mon, 18 Jul 2022 05:48:49 -0700 (PDT) Received: from krava ([193.85.244.190]) by smtp.gmail.com with ESMTPSA id t18-20020a1709067c1200b006febce7081bsm5436352ejo.163.2022.07.18.05.48.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Jul 2022 05:48:48 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Mon, 18 Jul 2022 14:48:46 +0200 To: Martynas Pumputis Cc: Jiri Olsa , 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 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 02:09:54PM +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 jirka > > > > > and that kprobe address is what we return in helper: > > > > BPF_CALL_1(bpf_get_func_ip_kprobe, struct pt_regs *, regs) > > { > > struct kprobe *kp = kprobe_running(); > > > > return kp ? (uintptr_t)kp->addr : 0; > > } > > > > so the adjustment would work only for address at function entry, but > > would be wrong for address within the function > > > > perhaps we could add flag to kprobe to indicate the addr adjustment > > was done and use it in helper > > > > but that's why I thought I'd keep bpf_get_func_ip_kprobe as it and > > leave it up to user > > > > kprobe_multi and trampolines are different, because they can be > > only at the function entry, so we can adjust the ip properly > > > > jirka