From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sami Tolvanen Subject: [PATCH 07/22] kbuild: lto: merge module sections Date: Wed, 24 Jun 2020 13:31:45 -0700 Message-ID: <20200624203200.78870-8-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-kbuild-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 LLD always splits sections with LTO, which increases module sizes. This change adds a linker script that merges the split sections in the final module and discards the .eh_frame section that LLD may generate. Suggested-by: Nick Desaulniers Signed-off-by: Sami Tolvanen --- Makefile | 2 ++ scripts/module-lto.lds | 26 ++++++++++++++++++++++++++ 2 files changed, 28 insertions(+) create mode 100644 scripts/module-lto.lds diff --git a/Makefile b/Makefile index ee66513a5b66..9ffec5fe1737 100644 --- a/Makefile +++ b/Makefile @@ -898,6 +898,8 @@ CC_FLAGS_LTO_CLANG += -fvisibility=default # Limit inlining across translation units to reduce binary size LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5 KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG) + +KBUILD_LDS_MODULE += $(srctree)/scripts/module-lto.lds endif ifdef CONFIG_LTO diff --git a/scripts/module-lto.lds b/scripts/module-lto.lds new file mode 100644 index 000000000000..65884c652bf2 --- /dev/null +++ b/scripts/module-lto.lds @@ -0,0 +1,26 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and + * -ffunction-sections, which increases the size of the final module. + * Merge the split sections in the final binary. + */ +SECTIONS { + __patchable_function_entries : { *(__patchable_function_entries) } + + .bss : { + *(.bss .bss.[0-9a-zA-Z_]*) + *(.bss..L* .bss..compoundliteral*) + } + + .data : { + *(.data .data.[0-9a-zA-Z_]*) + *(.data..L* .data..compoundliteral*) + } + + .rodata : { + *(.rodata .rodata.[0-9a-zA-Z_]*) + *(.rodata..L* .rodata..compoundliteral*) + } + + .text : { *(.text .text.[0-9a-zA-Z_]*) } +} -- 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]:50540 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406476AbgFXUdN (ORCPT ); Wed, 24 Jun 2020 16:33:13 -0400 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCCFDC061798 for ; Wed, 24 Jun 2020 13:33:11 -0700 (PDT) Received: by mail-qt1-x84a.google.com with SMTP id p9so2444943qtn.5 for ; Wed, 24 Jun 2020 13:33:11 -0700 (PDT) Date: Wed, 24 Jun 2020 13:31:45 -0700 In-Reply-To: <20200624203200.78870-1-samitolvanen@google.com> Message-ID: <20200624203200.78870-8-samitolvanen@google.com> Mime-Version: 1.0 References: <20200624203200.78870-1-samitolvanen@google.com> Subject: [PATCH 07/22] kbuild: lto: merge module sections 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: <20200624203145.ahpegNCtxrsv0i9mjL_RMFWnOLXm8mOgmrO6NYZj-u0@z> LLD always splits sections with LTO, which increases module sizes. This change adds a linker script that merges the split sections in the final module and discards the .eh_frame section that LLD may generate. Suggested-by: Nick Desaulniers Signed-off-by: Sami Tolvanen --- Makefile | 2 ++ scripts/module-lto.lds | 26 ++++++++++++++++++++++++++ 2 files changed, 28 insertions(+) create mode 100644 scripts/module-lto.lds diff --git a/Makefile b/Makefile index ee66513a5b66..9ffec5fe1737 100644 --- a/Makefile +++ b/Makefile @@ -898,6 +898,8 @@ CC_FLAGS_LTO_CLANG += -fvisibility=default # Limit inlining across translation units to reduce binary size LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5 KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG) + +KBUILD_LDS_MODULE += $(srctree)/scripts/module-lto.lds endif ifdef CONFIG_LTO diff --git a/scripts/module-lto.lds b/scripts/module-lto.lds new file mode 100644 index 000000000000..65884c652bf2 --- /dev/null +++ b/scripts/module-lto.lds @@ -0,0 +1,26 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and + * -ffunction-sections, which increases the size of the final module. + * Merge the split sections in the final binary. + */ +SECTIONS { + __patchable_function_entries : { *(__patchable_function_entries) } + + .bss : { + *(.bss .bss.[0-9a-zA-Z_]*) + *(.bss..L* .bss..compoundliteral*) + } + + .data : { + *(.data .data.[0-9a-zA-Z_]*) + *(.data..L* .data..compoundliteral*) + } + + .rodata : { + *(.rodata .rodata.[0-9a-zA-Z_]*) + *(.rodata..L* .rodata..compoundliteral*) + } + + .text : { *(.text .text.[0-9a-zA-Z_]*) } +} -- 2.27.0.212.ge8ba1cc988-goog