From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sami Tolvanen Subject: [PATCH 10/22] init: lto: fix PREL32 relocations Date: Wed, 24 Jun 2020 13:31:48 -0700 Message-ID: <20200624203200.78870-11-samitolvanen@google.com> References: <20200624203200.78870-1-samitolvanen@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20200624203200.78870-1-samitolvanen@google.com> Sender: linux-kernel-owner@vger.kernel.org To: Masahiro Yamada , Will Deacon Cc: Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, Sami Tolvanen List-Id: linux-arch.vger.kernel.org With LTO, the compiler can rename static functions to avoid global naming collisions. As initcall functions are typically static, renaming can break references to them in inline assembly. This change adds a global stub with a stable name for each initcall to fix the issue when PREL32 relocations are used. Signed-off-by: Sami Tolvanen --- include/linux/init.h | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/include/linux/init.h b/include/linux/init.h index af638cd6dd52..5b4bdc5a8399 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -209,26 +209,48 @@ extern bool initcall_debug; */ #define __initcall_section(__sec, __iid) \ #__sec ".init.." #__iid + +/* + * With LTO, the compiler can rename static functions to avoid + * global naming collisions. We use a global stub function for + * initcalls to create a stable symbol name whose address can be + * taken in inline assembly when PREL32 relocations are used. + */ +#define __initcall_stub(fn, __iid, id) \ + __initcall_name(initstub, __iid, id) + +#define __define_initcall_stub(__stub, fn) \ + int __init __stub(void) \ + { \ + return fn(); \ + } \ + __ADDRESSABLE(__stub) #else #define __initcall_section(__sec, __iid) \ #__sec ".init" + +#define __initcall_stub(fn, __iid, id) fn + +#define __define_initcall_stub(__stub, fn) \ + __ADDRESSABLE(fn) #endif #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS -#define ____define_initcall(fn, __name, __sec) \ - __ADDRESSABLE(fn) \ +#define ____define_initcall(fn, __stub, __name, __sec) \ + __define_initcall_stub(__stub, fn) \ asm(".section \"" __sec "\", \"a\" \n" \ __stringify(__name) ": \n" \ - ".long " #fn " - . \n" \ + ".long " __stringify(__stub) " - . \n" \ ".previous \n"); #else -#define ____define_initcall(fn, __name, __sec) \ +#define ____define_initcall(fn, __unused, __name, __sec) \ static initcall_t __name __used \ __attribute__((__section__(__sec))) = fn; #endif #define __unique_initcall(fn, id, __sec, __iid) \ ____define_initcall(fn, \ + __initcall_stub(fn, __iid, id), \ __initcall_name(initcall, __iid, id), \ __initcall_section(__sec, __iid)) -- 2.27.0.212.ge8ba1cc988-goog From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406459AbgFXUdS (ORCPT ); Wed, 24 Jun 2020 16:33:18 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 143DBC0613ED for ; Wed, 24 Jun 2020 13:33:17 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id 186so3455097yby.19 for ; Wed, 24 Jun 2020 13:33:17 -0700 (PDT) Date: Wed, 24 Jun 2020 13:31:48 -0700 In-Reply-To: <20200624203200.78870-1-samitolvanen@google.com> Message-ID: <20200624203200.78870-11-samitolvanen@google.com> Mime-Version: 1.0 References: <20200624203200.78870-1-samitolvanen@google.com> Subject: [PATCH 10/22] init: lto: fix PREL32 relocations From: Sami Tolvanen Content-Type: text/plain; charset="UTF-8" Sender: linux-arch-owner@vger.kernel.org List-ID: To: Masahiro Yamada , Will Deacon Cc: Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, Sami Tolvanen Message-ID: <20200624203148.cM4PYYJcSb9f9az_rFad9XU1MRQ1Jw3RiBpXGgoubII@z> With LTO, the compiler can rename static functions to avoid global naming collisions. As initcall functions are typically static, renaming can break references to them in inline assembly. This change adds a global stub with a stable name for each initcall to fix the issue when PREL32 relocations are used. Signed-off-by: Sami Tolvanen --- include/linux/init.h | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/include/linux/init.h b/include/linux/init.h index af638cd6dd52..5b4bdc5a8399 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -209,26 +209,48 @@ extern bool initcall_debug; */ #define __initcall_section(__sec, __iid) \ #__sec ".init.." #__iid + +/* + * With LTO, the compiler can rename static functions to avoid + * global naming collisions. We use a global stub function for + * initcalls to create a stable symbol name whose address can be + * taken in inline assembly when PREL32 relocations are used. + */ +#define __initcall_stub(fn, __iid, id) \ + __initcall_name(initstub, __iid, id) + +#define __define_initcall_stub(__stub, fn) \ + int __init __stub(void) \ + { \ + return fn(); \ + } \ + __ADDRESSABLE(__stub) #else #define __initcall_section(__sec, __iid) \ #__sec ".init" + +#define __initcall_stub(fn, __iid, id) fn + +#define __define_initcall_stub(__stub, fn) \ + __ADDRESSABLE(fn) #endif #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS -#define ____define_initcall(fn, __name, __sec) \ - __ADDRESSABLE(fn) \ +#define ____define_initcall(fn, __stub, __name, __sec) \ + __define_initcall_stub(__stub, fn) \ asm(".section \"" __sec "\", \"a\" \n" \ __stringify(__name) ": \n" \ - ".long " #fn " - . \n" \ + ".long " __stringify(__stub) " - . \n" \ ".previous \n"); #else -#define ____define_initcall(fn, __name, __sec) \ +#define ____define_initcall(fn, __unused, __name, __sec) \ static initcall_t __name __used \ __attribute__((__section__(__sec))) = fn; #endif #define __unique_initcall(fn, id, __sec, __iid) \ ____define_initcall(fn, \ + __initcall_stub(fn, __iid, id), \ __initcall_name(initcall, __iid, id), \ __initcall_section(__sec, __iid)) -- 2.27.0.212.ge8ba1cc988-goog