From patchwork Mon Nov 9 18:57:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Olsa X-Patchwork-Id: 322029 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=-10.0 required=3.0 tests=BAYES_00,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 72D87C2D0A3 for ; Mon, 9 Nov 2020 18:58:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E677206D8 for ; Mon, 9 Nov 2020 18:58:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730103AbgKIS6H convert rfc822-to-8bit (ORCPT ); Mon, 9 Nov 2020 13:58:07 -0500 Received: from us-smtp-delivery-44.mimecast.com ([205.139.111.44]:36221 "EHLO us-smtp-delivery-44.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729451AbgKIS6F (ORCPT ); Mon, 9 Nov 2020 13:58:05 -0500 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-350-dPqptwy7MQiaH7u9vZ87jQ-1; Mon, 09 Nov 2020 13:58:00 -0500 X-MC-Unique: dPqptwy7MQiaH7u9vZ87jQ-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 883A81074654; Mon, 9 Nov 2020 18:57:58 +0000 (UTC) Received: from krava.redhat.com (unknown [10.40.192.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9E2FE7664C; Mon, 9 Nov 2020 18:57:55 +0000 (UTC) From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: Arnaldo Carvalho de Melo , Yonghong Song , Song Liu , Andrii Nakryiko , netdev@vger.kernel.org, bpf@vger.kernel.org, Martin KaFai Lau , John Fastabend , KP Singh Subject: [PATCHv5 bpf] bpf: Move iterator functions into special init section Date: Mon, 9 Nov 2020 19:57:54 +0100 Message-Id: <20201109185754.377373-1-jolsa@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jolsa@kernel.org X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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. Cc: Arnaldo Carvalho de Melo Suggested-by: Yonghong Song Acked-by: Song Liu Acked-by: Andrii Nakryiko Signed-off-by: Jiri Olsa --- v5 changes: - use "" in __section macro due to: 33def8498fdde180 ("treewide: Convert macro and uses of __section(foo) to __section("foo")") [Arnaldo] v4: https://lore.kernel.org/bpf/20201106222512.52454-1-jolsa@kernel.org/ 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 b2b3d81b1535..f91029b3443b 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 /* @@ -741,7 +754,8 @@ #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 2b16bf48aab6..73e8ededde3e 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1276,10 +1276,16 @@ 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 7b53cb3092ee..a7c71e3b5f9a 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.