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 X-Spam-Level: X-Spam-Status: No, score=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E58DBC47095 for ; Mon, 7 Jun 2021 18:15:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C47C961003 for ; Mon, 7 Jun 2021 18:15:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230421AbhFGSRh (ORCPT ); Mon, 7 Jun 2021 14:17:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:37007 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230316AbhFGSRf (ORCPT ); Mon, 7 Jun 2021 14:17:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623089743; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=nmsvIH7jJcORAKoc1AzQ0n7U+J/SmLHSILZ4a3vgCdo=; b=RkHYHcUK+5Xu0oaSXkI7vGdZfRcoMoM3MkcfRZTNGdc17g2yknyTRSa45rThG4d3Jeqco7 SOvbi2CDmB2TGy6SpwmrHCiMfo0guWX12XkW+RsY6WA1A5QPe/a93VZJqCdF/P+JMQy/EK zICNmWOrC58sPpGE0LYG+H1eN5RK9qw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-309-KEzEeyYeOQGZv6QW_cC4rw-1; Mon, 07 Jun 2021 14:15:39 -0400 X-MC-Unique: KEzEeyYeOQGZv6QW_cC4rw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9242C101371C; Mon, 7 Jun 2021 18:15:37 +0000 (UTC) Received: from krava (unknown [10.40.192.167]) by smtp.corp.redhat.com (Postfix) with SMTP id DC6A0620DE; Mon, 7 Jun 2021 18:15:34 +0000 (UTC) Date: Mon, 7 Jun 2021 20:15:33 +0200 From: Jiri Olsa To: Yonghong Song Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , "Steven Rostedt (VMware)" , netdev@vger.kernel.org, bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , John Fastabend , KP Singh , Daniel Xu , Viktor Malik Subject: Re: [PATCH 10/19] bpf: Allow to store caller's ip as argument Message-ID: References: <20210605111034.1810858-1-jolsa@kernel.org> <20210605111034.1810858-11-jolsa@kernel.org> <03777e58-a2b0-83b5-959f-3ae4afadb191@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <03777e58-a2b0-83b5-959f-3ae4afadb191@fb.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sun, Jun 06, 2021 at 08:21:51PM -0700, Yonghong Song wrote: > > > On 6/5/21 4:10 AM, Jiri Olsa wrote: > > When we will have multiple functions attached to trampoline > > we need to propagate the function's address to the bpf program. > > > > Adding new BPF_TRAMP_F_IP_ARG flag to arch_prepare_bpf_trampoline > > function that will store origin caller's address before function's > > arguments. > > > > Signed-off-by: Jiri Olsa > > --- > > arch/x86/net/bpf_jit_comp.c | 18 ++++++++++++++---- > > include/linux/bpf.h | 5 +++++ > > 2 files changed, 19 insertions(+), 4 deletions(-) > > > > diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c > > index b77e6bd78354..d2425c18272a 100644 > > --- a/arch/x86/net/bpf_jit_comp.c > > +++ b/arch/x86/net/bpf_jit_comp.c > > @@ -1951,7 +1951,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i > > void *orig_call) > > { > > int ret, i, cnt = 0, nr_args = m->nr_args; > > - int stack_size = nr_args * 8; > > + int stack_size = nr_args * 8, ip_arg = 0; > > struct bpf_tramp_progs *fentry = &tprogs[BPF_TRAMP_FENTRY]; > > struct bpf_tramp_progs *fexit = &tprogs[BPF_TRAMP_FEXIT]; > > struct bpf_tramp_progs *fmod_ret = &tprogs[BPF_TRAMP_MODIFY_RETURN]; > > @@ -1975,6 +1975,9 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i > > */ > > orig_call += X86_PATCH_SIZE; > > + if (flags & BPF_TRAMP_F_IP_ARG) > > + stack_size += 8; > > + > > prog = image; > > EMIT1(0x55); /* push rbp */ > > @@ -1982,7 +1985,14 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i > > EMIT4(0x48, 0x83, 0xEC, stack_size); /* sub rsp, stack_size */ > > EMIT1(0x53); /* push rbx */ > > - save_regs(m, &prog, nr_args, stack_size); > > + if (flags & BPF_TRAMP_F_IP_ARG) { > > + emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8); > > + EMIT4(0x48, 0x83, 0xe8, X86_PATCH_SIZE); /* sub $X86_PATCH_SIZE,%rax*/ > > Could you explain what the above EMIT4 is for? I am not quite familiar with > this piece of code and hence the question. Some comments here > should help too. it's there to generate the 'sub $X86_PATCH_SIZE,%rax' instruction to get the real IP address of the traced function, and it's stored to stack on the next line I'll put more comments in there jirka > > > + emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -stack_size); > > + ip_arg = 8; > > + } > > + > > + save_regs(m, &prog, nr_args, stack_size - ip_arg); > > if (flags & BPF_TRAMP_F_CALL_ORIG) { > > /* arg1: mov rdi, im */ > > @@ -2011,7 +2021,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i > > } > > if (flags & BPF_TRAMP_F_CALL_ORIG) { > > - restore_regs(m, &prog, nr_args, stack_size); > > + restore_regs(m, &prog, nr_args, stack_size - ip_arg); > > if (flags & BPF_TRAMP_F_ORIG_STACK) { > > emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8); > > @@ -2052,7 +2062,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i > > } > > if (flags & BPF_TRAMP_F_RESTORE_REGS) > > - restore_regs(m, &prog, nr_args, stack_size); > > + restore_regs(m, &prog, nr_args, stack_size - ip_arg); > > /* This needs to be done regardless. If there were fmod_ret programs, > > * the return value is only updated on the stack and still needs to be > [...] >