From nobody Thu Apr 9 14:23:07 2026 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 4C1A5C0502C for ; Mon, 29 Aug 2022 13:35:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229953AbiH2NfY (ORCPT ); Mon, 29 Aug 2022 09:35:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54952 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229909AbiH2NfT (ORCPT ); Mon, 29 Aug 2022 09:35:19 -0400 Received: from xry111.site (xry111.site [89.208.246.23]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 132904DB7A for ; Mon, 29 Aug 2022 06:35:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=xry111.site; s=default; t=1661780115; bh=TwdAnZTgoj4EYEJwsRSSBSF3le/kWOA9MA+6UkrMJuo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gPriV1snZWAJnOMBQq3lW6JNaPqN66GxTiKaq8D6a7q+9clLZ+x/AOWezXdsBluAB u7XrsElOvTmUXqxuDD4peuLrcadeobkIb2/ndMK8jwsUYSV9ksdsiVre8BEMEQuKo1 puenuWwYkUxIvNDjV66pnQGz7q79LpdYuHDIXIfg= Received: from xry111-x57s1.. (unknown [IPv6:240e:358:11dd:1900:dc73:854d:832e:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-384) server-digest SHA384) (Client did not present a certificate) (Authenticated sender: xry111@xry111.site) by xry111.site (Postfix) with ESMTPSA id A7BF866905; Mon, 29 Aug 2022 09:35:09 -0400 (EDT) From: Xi Ruoyao To: loongarch@lists.linux.dev Cc: linux-kernel@vger.kernel.org, WANG Xuerui , Huacai Chen , Youling Tang , Jinyang He , Xi Ruoyao Subject: [PATCH v6 3/6] LoongArch: Use model("extreme") attribute for per-CPU variables in module if CONFIG_AS_HAS_EXPLICIT_RELOCS Date: Mon, 29 Aug 2022 21:31:43 +0800 Message-Id: <20220829133146.15236-4-xry111@xry111.site> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220829133146.15236-1-xry111@xry111.site> References: <20220829133146.15236-1-xry111@xry111.site> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" On LoongArch, The "address" of a per-CPU variable symbol is actually an offset from $r21. The value is nearing the loading address of main kernel image, but far from the address of modules. We need to tell the compiler that a PC-relative addressing with 32-bit offset is not sufficient for local per-CPU variables. After some discussion with GCC maintainers, we implemented this attribute to indicate that a PC-relative addressing with 64-bit offset should be used. This attribute should be available in GCC 13 release. Some early GCC 13 snapshots may support -mexplicit-relocs but lack this attribute, we simply reject them. Signed-off-by: Xi Ruoyao Link: https://gcc.gnu.org/r13-2199 --- arch/loongarch/Makefile | 3 +++ arch/loongarch/include/asm/percpu.h | 8 ++++++++ 2 files changed, 11 insertions(+) diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile index 1563747c4fa8..593818a61741 100644 --- a/arch/loongarch/Makefile +++ b/arch/loongarch/Makefile @@ -53,6 +53,9 @@ LDFLAGS_vmlinux +=3D -G0 -static -n -nostdlib # combination of a "new" assembler and "old" compiler is not supported. E= ither # upgrade the compiler or downgrade the assembler. ifdef CONFIG_AS_HAS_EXPLICIT_RELOCS +ifeq ($(shell echo '__has_attribute(model)' | $(CC) -E -P - 2> /dev/null),= 0) +$(error "C compiler must support model attribute if using explicit relocs") +endif cflags-y +=3D -mexplicit-relocs else cflags-y +=3D $(call cc-option,-mno-explicit-relocs) diff --git a/arch/loongarch/include/asm/percpu.h b/arch/loongarch/include/a= sm/percpu.h index 0bd6b0110198..dd7fcc553efa 100644 --- a/arch/loongarch/include/asm/percpu.h +++ b/arch/loongarch/include/asm/percpu.h @@ -8,6 +8,14 @@ #include #include =20 +#if defined(MODULE) && defined(CONFIG_AS_HAS_EXPLICIT_RELOCS) +/* The "address" (in fact, offset from $r21) of a per-CPU variable is close + * to the load address of main kernel image, but far from where the module= s are + * loaded. Tell the compiler this fact. + */ +# define PER_CPU_ATTRIBUTES __attribute__((model("extreme"))) +#endif + /* Use r21 for fast access */ register unsigned long __my_cpu_offset __asm__("$r21"); =20 --=20 2.37.0