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=-6.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 CE5D3C06511 for ; Mon, 1 Jul 2019 15:36:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9C09D20881 for ; Mon, 1 Jul 2019 15:36:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GxqJoOIA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729417AbfGAPgQ (ORCPT ); Mon, 1 Jul 2019 11:36:16 -0400 Received: from mail-qt1-f194.google.com ([209.85.160.194]:42161 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728275AbfGAPgQ (ORCPT ); Mon, 1 Jul 2019 11:36:16 -0400 Received: by mail-qt1-f194.google.com with SMTP id s15so15058286qtk.9; Mon, 01 Jul 2019 08:36:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=bkx/qJ8eI3y0m6A4MBTtNAvtV8T8ESk/GkGO0UYcsNM=; b=GxqJoOIApBZHzobayrcuAqJlSdNKhKYFWFaLw/v6b3hDe8238Fe7EDQph9waZcoxDn DW+egfkCCR5g8bJKuaN+p6Oj3DRURuoiXQIjuiupypuNyIQA2JQ6ImEfLd+VxkpvB4KT 9EPbuf5YSKwvBo8uZXQ9S6ID9XeCx2/Hqs4YOs363TR1vJS6tyadG1yyLJT8iOpLhDIW fBamoF+3XWPv6wFeLrInNsp9xcyAbF6rInEoo0QdnNZAvQtxWWmoGaML6ubA+em9UOGZ wejXxtMt/N7+Hi2HMS+D2jDTvqXoRXHZCKlGct7zZNCIH2R56SezAoFsIfIsRhnFRNXJ uqEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=bkx/qJ8eI3y0m6A4MBTtNAvtV8T8ESk/GkGO0UYcsNM=; b=TfyGQ2Nx0JnQwDzOqVzxdMh9MxUcl2kHzZLMkYWeg/t40MtoyzG2CbdSQy+rMBkhIC dcAt59zEbDVJxLcYaNGt7mCggQ0Co2HYRb7UCDz2dRpF0JXLW7UyFbB1Iy19/ftq8YVU z3aaCJky2Fwx6430bwPpspFF9eb7+lX2VIPPXonTTwuoqCevLumSAqhziIllZgvfYQUd ugf2mYokyOebP712/Ebfka4hZG62CojNoV3MuZFl/cUFJKphYzNFREXMevMOTiXIxy4b lN1ljdvfE5RwRpCOF1DxNGTSjPcPjnw48fBFHjtTbiIpDtLT5ELPN4fLemfQp1wJ3hId NCGg== X-Gm-Message-State: APjAAAUJPBhD+s8GbO1Newiw+zijgh57TMl9EFyBQ2npdQvSl0DXmwWc XpoHiA7Y2ieJ34q/ObnjBFTj5keMI1coser3wWA= X-Google-Smtp-Source: APXvYqwCGpbkxLueVdnYY2wo4dyIXr3ZwLLdZih8GlBpjIDXsi2Od/xlKq4jnJaIYKTF4MI+q4XUcYMK1DIig0yAntw= X-Received: by 2002:ac8:2d56:: with SMTP id o22mr20760377qta.171.1561995375099; Mon, 01 Jul 2019 08:36:15 -0700 (PDT) MIME-Version: 1.0 References: <20190628231049.22149-1-sdf@google.com> In-Reply-To: From: Andrii Nakryiko Date: Mon, 1 Jul 2019 08:36:04 -0700 Message-ID: Subject: Re: [PATCH bpf-next 1/2] bpf: allow wide (u64) aligned stores for some fields of bpf_sock_addr To: Yonghong Song Cc: Stanislav Fomichev , "netdev@vger.kernel.org" , "bpf@vger.kernel.org" , "davem@davemloft.net" , "ast@kernel.org" , "daniel@iogearbox.net" , Andrii Nakryiko , kernel test robot Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, Jun 29, 2019 at 10:53 PM Yonghong Song wrote: > > > > On 6/28/19 4:10 PM, Stanislav Fomichev wrote: > > Since commit cd17d7770578 ("bpf/tools: sync bpf.h") clang decided > > that it can do a single u64 store into user_ip6[2] instead of two > > separate u32 ones: > > > > # 17: (18) r2 = 0x100000000000000 > > # ; ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2); > > # 19: (7b) *(u64 *)(r1 +16) = r2 > > # invalid bpf_context access off=16 size=8 > > > > From the compiler point of view it does look like a correct thing > > to do, so let's support it on the kernel side. > > > > Credit to Andrii Nakryiko for a proper implementation of > > bpf_ctx_wide_store_ok. > > > > Cc: Andrii Nakryiko > > Cc: Yonghong Song > > Fixes: cd17d7770578 ("bpf/tools: sync bpf.h") > > Reported-by: kernel test robot > > Signed-off-by: Stanislav Fomichev > > The change looks good to me with the following nits: > 1. could you add a cover letter for the patch set? > typically if the number of patches is more than one, > it would be a good practice with a cover letter. > See bpf_devel_QA.rst . > 2. with this change, the comments in uapi bpf.h > are not accurate any more. > __u32 user_ip6[4]; /* Allows 1,2,4-byte read an 4-byte write. > * Stored in network byte order. > > */ > __u32 msg_src_ip6[4]; /* Allows 1,2,4-byte read an 4-byte write. > * Stored in network byte order. > */ > now for stores, aligned 8-byte write is permitted. > could you update this as well? > > From the typical usage pattern, I did not see a need > for 8-tye read of user_ip6 and msg_src_ip6 yet. So let > us just deal with write for now. But I guess it's still possible for clang to optimize two consecutive 4-byte reads into single 8-byte read in some circumstances? If that's the case, maybe it's a good idea to have corresponding read checks as well? But overall this looks good to me: Acked-by: Andrii Nakryiko > > With the above two nits, > Acked-by: Yonghong Song > > > --- > > include/linux/filter.h | 6 ++++++ > > net/core/filter.c | 22 ++++++++++++++-------- > > 2 files changed, 20 insertions(+), 8 deletions(-) > > > > diff --git a/include/linux/filter.h b/include/linux/filter.h > > index 340f7d648974..3901007e36f1 100644 > > --- a/include/linux/filter.h > > +++ b/include/linux/filter.h > > @@ -746,6 +746,12 @@ bpf_ctx_narrow_access_ok(u32 off, u32 size, u32 size_default) > > return size <= size_default && (size & (size - 1)) == 0; > > } > > > > +#define bpf_ctx_wide_store_ok(off, size, type, field) \ > > + (size == sizeof(__u64) && \ > > + off >= offsetof(type, field) && \ > > + off + sizeof(__u64) <= offsetofend(type, field) && \ > > + off % sizeof(__u64) == 0) > > + > > #define bpf_classic_proglen(fprog) (fprog->len * sizeof(fprog->filter[0])) > > > > static inline void bpf_prog_lock_ro(struct bpf_prog *fp) > > diff --git a/net/core/filter.c b/net/core/filter.c > > index dc8534be12fc..5d33f2146dab 100644 > > --- a/net/core/filter.c > > +++ b/net/core/filter.c > > @@ -6849,6 +6849,16 @@ static bool sock_addr_is_valid_access(int off, int size, > > if (!bpf_ctx_narrow_access_ok(off, size, size_default)) > > return false; > > } else { > > + if (bpf_ctx_wide_store_ok(off, size, > > + struct bpf_sock_addr, > > + user_ip6)) > > + return true; > > + > > + if (bpf_ctx_wide_store_ok(off, size, > > + struct bpf_sock_addr, > > + msg_src_ip6)) > > + return true; > > + > > if (size != size_default) > > return false; > > } > > @@ -7689,9 +7699,6 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, > > /* SOCK_ADDR_STORE_NESTED_FIELD_OFF() has semantic similar to > > * SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF() but for store operation. > > * > > - * It doesn't support SIZE argument though since narrow stores are not > > - * supported for now. > > - * > > * In addition it uses Temporary Field TF (member of struct S) as the 3rd > > * "register" since two registers available in convert_ctx_access are not > > * enough: we can't override neither SRC, since it contains value to store, nor > > @@ -7699,7 +7706,7 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, > > * instructions. But we need a temporary place to save pointer to nested > > * structure whose field we want to store to. > > */ > > -#define SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, OFF, TF) \ > > +#define SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, SIZE, OFF, TF) \ > > do { \ > > int tmp_reg = BPF_REG_9; \ > > if (si->src_reg == tmp_reg || si->dst_reg == tmp_reg) \ > > @@ -7710,8 +7717,7 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, > > offsetof(S, TF)); \ > > *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(S, F), tmp_reg, \ > > si->dst_reg, offsetof(S, F)); \ > > - *insn++ = BPF_STX_MEM( \ > > - BPF_FIELD_SIZEOF(NS, NF), tmp_reg, si->src_reg, \ > > + *insn++ = BPF_STX_MEM(SIZE, tmp_reg, si->src_reg, \ > > bpf_target_off(NS, NF, FIELD_SIZEOF(NS, NF), \ > > target_size) \ > > + OFF); \ > > @@ -7723,8 +7729,8 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, > > TF) \ > > do { \ > > if (type == BPF_WRITE) { \ > > - SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, OFF, \ > > - TF); \ > > + SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, SIZE, \ > > + OFF, TF); \ > > } else { \ > > SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF( \ > > S, NS, F, NF, SIZE, OFF); \ > >