From patchwork Tue Oct 27 20:57:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 11861879 X-Patchwork-Delegate: bpf@iogearbox.net 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=-13.1 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,USER_AGENT_GIT 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 01368C388F9 for ; Tue, 27 Oct 2020 20:57:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA26E20720 for ; Tue, 27 Oct 2020 20:57:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603832266; bh=1HIv2+pHzyYp8hpDB0NxtuBOQ5Za1hvza5Qv+Vu4Q90=; h=From:To:Cc:Subject:Date:List-ID:From; b=BV2VVgdmeWIhxfi/OJ5gej8COOq3Rmwfy2foCrwN8RLvSR5pnenZ/c6r9zrtjRgki CY9grgGbeebTffu6An0dbihRuhGqU5qw+VpjKwHDQRx8e4fcaMqM3+kf1e2mhS8LQN gMCYFSKIuFELsfFx/eQnxlrmUNyK9MEdQxzqvCcc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S373460AbgJ0U5o (ORCPT ); Tue, 27 Oct 2020 16:57:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:48652 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2443729AbgJ0U5n (ORCPT ); Tue, 27 Oct 2020 16:57:43 -0400 Received: from e123331-lin.nice.arm.com (lfbn-nic-1-188-42.w2-15.abo.wanadoo.fr [2.15.37.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3635020706; Tue, 27 Oct 2020 20:57:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603832263; bh=1HIv2+pHzyYp8hpDB0NxtuBOQ5Za1hvza5Qv+Vu4Q90=; h=From:To:Cc:Subject:Date:From; b=Xz1663r3QuVB6qtvYj+hWv6Y0/0mCAtXKMBUxSc5p7H2qrdBZP9fh5sCiaz/gGRYz no1odXBalplpep8WUZ6WKa9INSgbCA0f2jqpCnDuzWlKbJv2D7Mnhtbt//+7L/0TST MNbZvf/skyuR+zB070g6PH/ufSNL1wVdLbftf0ns= From: Ard Biesheuvel To: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, arnd@arndb.de, Ard Biesheuvel , Nick Desaulniers , Arvind Sankar , Randy Dunlap , Josh Poimboeuf , Thomas Gleixner , Alexei Starovoitov , Daniel Borkmann , Peter Zijlstra , Geert Uytterhoeven , Kees Cook Subject: [PATCH] bpf: don't rely on GCC __attribute__((optimize)) to disable GCSE Date: Tue, 27 Oct 2020 21:57:23 +0100 Message-Id: <20201027205723.12514-1-ardb@kernel.org> X-Mailer: git-send-email 2.17.1 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Commit 3193c0836f203 ("bpf: Disable GCC -fgcse optimization for ___bpf_prog_run()") introduced a __no_fgcse macro that expands to a function scope __attribute__((optimize("-fno-gcse"))), to disable a GCC specific optimization that was causing trouble on x86 builds, and was not expected to have any positive effect in the first place. However, as the GCC manual documents, __attribute__((optimize)) is not for production use, and results in all other optimization options to be forgotten for the function in question. This can cause all kinds of trouble, but in one particular reported case, it causes -fno-asynchronous-unwind-tables to be disregarded, resulting in .eh_frame info to be emitted for the function inadvertently. This reverts commit 3193c0836f203, and instead, it disables the -fgcse optimization for the entire source file, but only when building for X86. Cc: Nick Desaulniers Cc: Arvind Sankar Cc: Randy Dunlap Cc: Josh Poimboeuf Cc: Thomas Gleixner Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Peter Zijlstra (Intel) Cc: Geert Uytterhoeven Cc: Kees Cook Fixes: 3193c0836f203 ("bpf: Disable GCC -fgcse optimization for ___bpf_prog_run()") Signed-off-by: Ard Biesheuvel Tested-by: Geert Uytterhoeven Acked-by: Miguel Ojeda --- include/linux/compiler-gcc.h | 2 -- include/linux/compiler_types.h | 4 ---- kernel/bpf/Makefile | 4 +++- kernel/bpf/core.c | 2 +- 4 files changed, 4 insertions(+), 8 deletions(-) diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index d1e3c6896b71..5deb37024574 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -175,5 +175,3 @@ #else #define __diag_GCC_8(s) #endif - -#define __no_fgcse __attribute__((optimize("-fno-gcse"))) diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 6e390d58a9f8..ac3fa37a84f9 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -247,10 +247,6 @@ struct ftrace_likely_data { #define asm_inline asm #endif -#ifndef __no_fgcse -# define __no_fgcse -#endif - /* Are two types/vars the same type (ignoring qualifiers)? */ #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index bdc8cd1b6767..02b58f44c479 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -1,6 +1,8 @@ # SPDX-License-Identifier: GPL-2.0 obj-y := core.o -CFLAGS_core.o += $(call cc-disable-warning, override-init) +# ___bpf_prog_run() needs GCSE disabled on x86; see 3193c0836f203 for details +cflags-core-$(CONFIG_X86) := -fno-gcse +CFLAGS_core.o += $(call cc-disable-warning, override-init) $(cflags-core-y) obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o prog_iter.o obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 9268d77898b7..55454d2278b1 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -1369,7 +1369,7 @@ u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr) * * Decode and execute eBPF instructions. */ -static u64 __no_fgcse ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) +static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) { #define BPF_INSN_2_LBL(x, y) [BPF_##x | BPF_##y] = &&x##_##y #define BPF_INSN_3_LBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = &&x##_##y##_##z