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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 CF4ABC56201 for ; Wed, 21 Oct 2020 19:25:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D85524171 for ; Wed, 21 Oct 2020 19:25:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603308335; bh=XmGtBDIc8rDQrH+DPZt5CdCuiMuBmj/fWwAZdzc8B3Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=UEIhVBKLhfldwnRW9sSHCt6mRiBaQ8qkjZ58Rzei2LRS1eF9/S55ht807aHkSa0RN TX5r+GxSV74Zsq4JzFyRmWMKBrGExc2dloetmqxsF9bTGUbhA7sJ730Pwz7LYXqxYs +rLVxK1NRw7sl175OmE/Bz42crUkED1piVt8gsu0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2504476AbgJUTZe (ORCPT ); Wed, 21 Oct 2020 15:25:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:42300 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2441904AbgJUTZe (ORCPT ); Wed, 21 Oct 2020 15:25:34 -0400 Received: from quaco.ghostprotocols.net (unknown [179.97.37.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1737824170; Wed, 21 Oct 2020 19:25:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603308333; bh=XmGtBDIc8rDQrH+DPZt5CdCuiMuBmj/fWwAZdzc8B3Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TkanMKHvCJdb4SrnL21T/IdHnW9G3ajKYy2gfB+zD8NqWiCeFF7Aek91Pi0wlSDhp GQ2aBuGNjgLRTMOInKjjdlZZjiEFHAgkLZ+fRkKWq3VYJQ2mVomNgmswPa87llMmnk MIHqFw5ylmcDYLJPKoo4LL99uJ7NCivXpc9v8slU= Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 5C1EA403C2; Wed, 21 Oct 2020 16:25:30 -0300 (-03) Date: Wed, 21 Oct 2020 16:25:30 -0300 From: Arnaldo Carvalho de Melo To: Andrii Nakryiko Cc: dwarves@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com, ast@kernel.org Subject: Re: [PATCH dwarves] btf_loader: handle union forward declaration properly Message-ID: <20201021192530.GS2342001@kernel.org> References: <20201009192607.699835-1-andrii@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201009192607.699835-1-andrii@kernel.org> X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Em Fri, Oct 09, 2020 at 12:26:07PM -0700, Andrii Nakryiko escreveu: > Differentiate between struct and union forwards. For BTF_KIND_FWD this is > determined by kflag. So teach btf_loader to use that bit to decide whether > forward is for union or struct. So, before this patch 'btfdiff vmlinux' comes clean, i.e. pretty printing from DWARF matches pretty printing from BTF, after it: [acme@five pahole]$ btfdiff vmlinux | wc -l 1500 [acme@five pahole]$ One of the differences: @@ -117457,7 +117457,7 @@ struct wireless_dev { /* XXX last struct has 1 byte of padding */ - struct cfg80211_cqm_config * cqm_config; /* 952 8 */ + union cfg80211_cqm_config * cqm_config; /* 952 8 */ /* --- cacheline 15 boundary (960 bytes) --- */ struct list_head pmsr_list; /* 960 16 */ spinlock_t pmsr_lock; /* 976 4 */ [acme@five pahole]$ Looking at the source code: struct wireless_dev { ... struct cfg80211_cqm_config *cqm_config; ... } Also: struct nfnl_ct_hook { - struct nf_conn * (*get_ct)(const struct sk_buff *, enum ip_conntrack_info *); /* 0 8 */ - size_t (*build_size)(const struct nf_conn *); /* 8 8 */ - int (*build)(struct sk_buff *, struct nf_conn *, enum ip_conntrack_info, u_int16_t, u_int16_t); /* 16 8 */ - int (*parse)(const struct nlattr *, struct nf_conn *); /* 24 8 */ - int (*attach_expect)(const struct nlattr *, struct nf_conn *, u32, u32); /* 32 8 */ - void (*seq_adjust)(struct sk_buff *, struct nf_conn *, enum ip_conntrack_info, s32); /* 40 8 */ + union nf_conn * (*get_ct)(const struct sk_buff *, enum ip_conntrack_info *); /* 0 8 */ + size_t (*build_size)(const union nf_conn *); /* 8 8 */ + int (*build)(struct sk_buff *, union nf_conn *, enum ip_conntrack_info, u_int16_t, u_int16_t); /* 16 8 */ + int (*parse)(const struct nlattr *, union nf_conn *); /* 24 8 */ + int (*attach_expect)(const struct nlattr *, union nf_conn *, u32, u32); /* 32 8 */ + void (*seq_adjust)(struct sk_buff *, union nf_conn *, enum ip_conntrack_info, s32); /* 40 8 */1 Looking at the source code: struct nfnl_ct_hook { struct nf_conn *(*get_ct)(const struct sk_buff *skb, enum ip_conntrack_info *ctinfo); size_t (*build_size)(const struct nf_conn *ct); int (*build)(struct sk_buff *skb, struct nf_conn *ct, enum ip_conntrack_info ctinfo, u_int16_t ct_attr, u_int16_t ct_info_attr); int (*parse)(const struct nlattr *attr, struct nf_conn *ct); int (*attach_expect)(const struct nlattr *attr, struct nf_conn *ct, u32 portid, u32 report); void (*seq_adjust)(struct sk_buff *skb, struct nf_conn *ct, enum ip_conntrack_info ctinfo, s32 off); }; - Arnaldo > Signed-off-by: Andrii Nakryiko > --- > N.B. This patch is based on top of tmp.libbtf_encoder branch. > > Also seems like non-forward declared union has a slightly different > representation from struct (class). Not sure why it is so, but this change > doesn't seem to break anything. > --- > > btf_loader.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/btf_loader.c b/btf_loader.c > index 9b5da3a4997a..0cb23967fec3 100644 > --- a/btf_loader.c > +++ b/btf_loader.c > @@ -134,12 +134,13 @@ static struct type *type__new(uint16_t tag, strings_t name, size_t size) > return type; > } > > -static struct class *class__new(strings_t name, size_t size) > +static struct class *class__new(strings_t name, size_t size, bool is_union) > { > struct class *class = tag__alloc(sizeof(*class)); > + uint32_t tag = is_union ? DW_TAG_union_type : DW_TAG_structure_type; > > if (class != NULL) { > - type__init(&class->type, DW_TAG_structure_type, name, size); > + type__init(&class->type, tag, name, size); > INIT_LIST_HEAD(&class->vtable); > } > > @@ -228,7 +229,7 @@ static int create_members(struct btf_elf *btfe, const struct btf_type *tp, > > static int create_new_class(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id) > { > - struct class *class = class__new(tp->name_off, tp->size); > + struct class *class = class__new(tp->name_off, tp->size, false); > int member_size = create_members(btfe, tp, &class->type); > > if (member_size < 0) > @@ -313,7 +314,7 @@ static int create_new_subroutine_type(struct btf_elf *btfe, const struct btf_typ > > static int create_new_forward_decl(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id) > { > - struct class *fwd = class__new(tp->name_off, 0); > + struct class *fwd = class__new(tp->name_off, 0, btf_kind(tp)); > > if (fwd == NULL) > return -ENOMEM; > -- > 2.24.1 > -- - Arnaldo