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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0CD4FA3741 for ; Mon, 31 Oct 2022 17:39:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231838AbiJaRjU (ORCPT ); Mon, 31 Oct 2022 13:39:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231829AbiJaRix (ORCPT ); Mon, 31 Oct 2022 13:38:53 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DFDAE13D40; Mon, 31 Oct 2022 10:38:40 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 17017B819BA; Mon, 31 Oct 2022 17:38:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38709C43147; Mon, 31 Oct 2022 17:38:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667237917; bh=P9CiTbFkLwYXgkEJtoE1pjsCHoI48SKWU5aipbF3igg=; h=From:To:Cc:Subject:Date:From; b=FWoSDZLAWEJZUT6mSbEXa8gW75M91KXEbFRnzgmaEPaVFzfP862DtwPc35OjioWj4 vFG/stMP+8m/M+TkH6HKIlUgBQ9FYWXbSvARZmvo6To5gL70wjkOHX6orXCFjdBmhD xS/m5oOjcxexhDG0tJ+96hf9aJKgssVytSEDvVzMg410YPKKTf/58hEwcA+//8NAaI ryWnBKa99eryMwamtaxUrn3YJWkCCeFYU/JOEl99g9AZLhAraPxrxb6DOE7WZOSRb+ 9cp5p/hkjTkepOa4SW2CKlYlT5qRTftB9rkHvam03HxfVaTEAudlh4rLMtsk+F/ngt H77toNMvDffKQ== From: Nathan Chancellor To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Nick Desaulniers , Tom Rix , x86@kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, patches@lists.linux.dev, Nathan Chancellor Subject: [PATCH bpf] bpf: Mark bpf_arch_init_dispatcher_early() as __init_or_module Date: Mon, 31 Oct 2022 10:38:19 -0700 Message-Id: <20221031173819.2344270-1-nathan@kernel.org> X-Mailer: git-send-email 2.38.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After commit dbe69b299884 ("bpf: Fix dispatcher patchable function entry to 5 bytes nop"), building kernel/bpf/dispatcher.c in certain configurations with LLVM's integrated assembler results in a known recordmcount bug: Cannot find symbol for section 4: .init.text. kernel/bpf/dispatcher.o: failed This occurs when there are only weak symbols in a particular section in the translation unit; in this case, bpf_arch_init_dispatcher_early() is marked '__weak __init' and it is the only symbol in the .init.text section. recordmcount expects there to be a symbol for a particular section but LLVM's integrated assembler (and GNU as after 2.37) do not generated section symbols. This has been worked around in the kernel before in commit 55d5b7dd6451 ("initramfs: fix clang build failure") and commit 6e7b64b9dd6d ("elfcore: fix building with clang"). Fixing recordmcount has been brought up before but there is no clear solution that does not break ftrace outright. Unfortunately, working around this issue by removing the '__init' from bpf_arch_init_dispatcher_early() is not an option, as the x86 version of bpf_arch_init_dispatcher_early() calls text_poke_early(), which is marked '__init_or_module', meaning that when CONFIG_MODULES is disabled, bpf_arch_init_dispatcher_early() has to be marked '__init' as well to avoid a section mismatch warning from modpost. However, bpf_arch_init_dispatcher_early() can be marked '__init_or_module' as well, which would resolve the recordmcount warning for configurations that support modules (i.e., the vast majority of them) while not introducing any new warnings for all configurations. Do so to clear up the build failure for CONFIG_MODULES=y configurations. Link: https://github.com/ClangBuiltLinux/linux/issues/981 Signed-off-by: Nathan Chancellor --- arch/x86/net/bpf_jit_comp.c | 2 +- include/linux/bpf.h | 2 +- kernel/bpf/dispatcher.c | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 00127abd89ee..4145939bbb6a 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -389,7 +389,7 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t, return ret; } -int __init bpf_arch_init_dispatcher_early(void *ip) +int __init_or_module bpf_arch_init_dispatcher_early(void *ip) { const u8 *nop_insn = x86_nops[5]; diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 0566705c1d4e..4aa7bde406f5 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -971,7 +971,7 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key, struct bpf_attach_target_info *tgt_info); void bpf_trampoline_put(struct bpf_trampoline *tr); int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs); -int __init bpf_arch_init_dispatcher_early(void *ip); +int __init_or_module bpf_arch_init_dispatcher_early(void *ip); #define BPF_DISPATCHER_INIT(_name) { \ .mutex = __MUTEX_INITIALIZER(_name.mutex), \ diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c index 04f0a045dcaa..e14a68e9a74f 100644 --- a/kernel/bpf/dispatcher.c +++ b/kernel/bpf/dispatcher.c @@ -91,7 +91,7 @@ int __weak arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int n return -ENOTSUPP; } -int __weak __init bpf_arch_init_dispatcher_early(void *ip) +int __weak __init_or_module bpf_arch_init_dispatcher_early(void *ip) { return -ENOTSUPP; } base-commit: 8bdc2acd420c6f3dd1f1c78750ec989f02a1e2b9 -- 2.38.1