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,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 17F28C5517A for ; Mon, 9 Nov 2020 18:05:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AEA79206F1 for ; Mon, 9 Nov 2020 18:05:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="pPgtP1Zs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729697AbgKISFE (ORCPT ); Mon, 9 Nov 2020 13:05:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:49116 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729119AbgKISFE (ORCPT ); Mon, 9 Nov 2020 13:05:04 -0500 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 B927A20665; Mon, 9 Nov 2020 18:05:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604945102; bh=vEGmaXFSAlmlJhVlqTb75fDxhB10+fY7IZE9/egG9DY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pPgtP1ZsB8NR+BPAzD7xi6srB/zTtM94awqTaDcpB25RQsRNBVHBee1x/PRYxPqbx Ki9vvzWKPAWlTwDdCL/6PnKi+EzL4x+VXZXZ29f5zqZPt8PrMuoxn8MCrlJE21911I n3wsGdlB5g7diO13GKW94UmIkwZoL6TXKwxynyHg= Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 6F286411D1; Mon, 9 Nov 2020 15:05:00 -0300 (-03) Date: Mon, 9 Nov 2020 15:05:00 -0300 From: Arnaldo Carvalho de Melo To: Jiri Olsa Cc: Yonghong Song , Song Liu , dwarves@vger.kernel.org, bpf@vger.kernel.org, Alexei Starovoitov , Andrii Nakryiko , Hao Luo , "Frank Ch. Eigler" , Mark Wielaard Subject: Re: [PATCH 1/3] bpf: Move iterator functions into special init section Message-ID: <20201109180500.GC340169@kernel.org> References: <20201106222512.52454-1-jolsa@kernel.org> <20201106222512.52454-2-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201106222512.52454-2-jolsa@kernel.org> X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Em Fri, Nov 06, 2020 at 11:25:10PM +0100, Jiri Olsa escreveu: > With upcoming changes to pahole, that change the way how and > which kernel functions are stored in BTF data, we need a way > to recognize iterator functions. > > Iterator functions need to be in BTF data, but have no real > body and are currently placed in .init.text section, so they > are freed after kernel init and are filtered out of BTF data > because of that. > > The solution is to place these functions under new section: > .init.bpf.preserve_type > > And add 2 new symbols to mark that area: > __init_bpf_preserve_type_begin > __init_bpf_preserve_type_end > > The code in pahole responsible for picking up the functions will > be able to recognize functions from this section and add them to > the BTF data and filter out all other .init.text functions. This isn't applying on torvalds/master: [acme@five linux]$ patch -p1 < /wb/1.patch patching file include/asm-generic/vmlinux.lds.h Hunk #2 succeeded at 754 (offset 1 line). patching file include/linux/bpf.h Hunk #1 succeeded at 1276 (offset -1 lines). patching file include/linux/init.h Hunk #1 FAILED at 52. 1 out of 1 hunk FAILED -- saving rejects to file include/linux/init.h.rej [acme@five linux]$ [acme@five linux]$ cat include/linux/init.h.rej --- include/linux/init.h +++ include/linux/init.h @@ -52,6 +52,7 @@ #define __initconst __section(.init.rodata) #define __exitdata __section(.exit.data) #define __exit_call __used __section(.exitcall.exit) +#define __init_bpf_preserve_type __section(.init.bpf.preserve_type) /* * modpost check for section mismatches during the kernel build. [acme@five linux]$ I'm fixing it up by hand to try together with pahole's patches. - Arnaldo > Suggested-by: Yonghong Song > Acked-by: Song Liu > Signed-off-by: Jiri Olsa > --- > include/asm-generic/vmlinux.lds.h | 16 +++++++++++++++- > include/linux/bpf.h | 8 +++++++- > include/linux/init.h | 1 + > 3 files changed, 23 insertions(+), 2 deletions(-) > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index cd14444bf600..e18e1030dabf 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -685,8 +685,21 @@ > .BTF_ids : AT(ADDR(.BTF_ids) - LOAD_OFFSET) { \ > *(.BTF_ids) \ > } > + > +/* > + * .init.bpf.preserve_type > + * > + * This section store special BPF function and marks them > + * with begin/end symbols pair for the sake of pahole tool. > + */ > +#define INIT_BPF_PRESERVE_TYPE \ > + __init_bpf_preserve_type_begin = .; \ > + *(.init.bpf.preserve_type) \ > + __init_bpf_preserve_type_end = .; \ > + MEM_DISCARD(init.bpf.preserve_type) > #else > #define BTF > +#define INIT_BPF_PRESERVE_TYPE > #endif > > /* > @@ -740,7 +753,8 @@ > #define INIT_TEXT \ > *(.init.text .init.text.*) \ > *(.text.startup) \ > - MEM_DISCARD(init.text*) > + MEM_DISCARD(init.text*) \ > + INIT_BPF_PRESERVE_TYPE > > #define EXIT_DATA \ > *(.exit.data .exit.data.*) \ > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index 73d5381a5d5c..894f66c7703e 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -1277,10 +1277,16 @@ struct bpf_link *bpf_link_get_from_fd(u32 ufd); > int bpf_obj_pin_user(u32 ufd, const char __user *pathname); > int bpf_obj_get_user(const char __user *pathname, int flags); > > +#ifdef CONFIG_DEBUG_INFO_BTF > +#define BPF_INIT __init_bpf_preserve_type > +#else > +#define BPF_INIT __init > +#endif > + > #define BPF_ITER_FUNC_PREFIX "bpf_iter_" > #define DEFINE_BPF_ITER_FUNC(target, args...) \ > extern int bpf_iter_ ## target(args); \ > - int __init bpf_iter_ ## target(args) { return 0; } > + int BPF_INIT bpf_iter_ ## target(args) { return 0; } > > struct bpf_iter_aux_info { > struct bpf_map *map; > diff --git a/include/linux/init.h b/include/linux/init.h > index 212fc9e2f691..133462863711 100644 > --- a/include/linux/init.h > +++ b/include/linux/init.h > @@ -52,6 +52,7 @@ > #define __initconst __section(.init.rodata) > #define __exitdata __section(.exit.data) > #define __exit_call __used __section(.exitcall.exit) > +#define __init_bpf_preserve_type __section(.init.bpf.preserve_type) > > /* > * modpost check for section mismatches during the kernel build. > -- > 2.26.2 > -- - Arnaldo