From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Subject: [PATCH v4 11/17] arm64/build: Warn on orphan section placement Date: Sun, 28 Jun 2020 23:18:34 -0700 Message-ID: <20200629061840.4065483-12-keescook@chromium.org> References: <20200629061840.4065483-1-keescook@chromium.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200629061840.4065483-1-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org To: Will Deacon Cc: Kees Cook , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Peter Collingbourne , James Morse , Borislav Petkov , Thomas Gleixner , Ingo Molnar , Russell King , Masahiro Yamada , Arvind Sankar , Nick Desaulniers , Nathan Chancellor , Arnd Bergmann , x86@kernel.org, clang-built-linux@googlegroups.com, linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org List-Id: linux-arch.vger.kernel.org We don't want to depend on the linker's orphan section placement heuristics as these can vary between linkers, and may change between versions. All sections need to be explicitly named in the linker script. Remove .eh_frame, since there are none left. Add .plt, .data.rel.ro, .igot.*, and .iplt to discards as they are not actually used. While .got.plt is also not used, it must be included otherwise ld.bfd will fail to link with the error: aarch64-linux-gnu-ld: discarded output section: `.got.plt' However, as it'd be better to validate that it stays effectively empty, add an assert, as suggested by Ard Biesheuvel. Explicitly include debug sections when they're present. Finally, enable orphan section warnings. Acked-by: Will Deacon Signed-off-by: Kees Cook --- arch/arm64/Makefile | 4 ++++ arch/arm64/kernel/vmlinux.lds.S | 11 ++++++++++- 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 895486606f74..fb3aa2d7de4d 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -29,6 +29,10 @@ LDFLAGS_vmlinux += --fix-cortex-a53-843419 endif endif +# We never want expected sections to be placed heuristically by the +# linker. All sections should be explicitly named in the linker script. +LDFLAGS_vmlinux += --orphan-handling=warn + ifeq ($(CONFIG_ARM64_USE_LSE_ATOMICS), y) ifneq ($(CONFIG_ARM64_LSE_ATOMICS), y) $(warning LSE atomics not supported by binutils) diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index b5a94ec1eada..320ba5ec2adc 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -94,7 +94,8 @@ SECTIONS /DISCARD/ : { *(.interp .dynamic) *(.dynsym .dynstr .hash .gnu.hash) - *(.eh_frame) + *(.plt) *(.data.rel.ro) + *(.igot.*) *(.iplt) } . = KIMAGE_VADDR + TEXT_OFFSET; @@ -244,9 +245,17 @@ SECTIONS _end = .; STABS_DEBUG + DWARF_DEBUG ELF_DETAILS HEAD_SYMBOLS + + /* + * Make sure that the .got.plt is either completely empty or it + * contains only the lazy dispatch entries. + */ + .got.plt (INFO) : { *(.got.plt) } + ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, ".got.plt not empty") } #include "image-vars.h" -- 2.25.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731691AbgF2TOJ (ORCPT ); Mon, 29 Jun 2020 15:14:09 -0400 Received: from mail-pl1-x643.google.com (mail-pl1-x643.google.com [IPv6:2607:f8b0:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1B376C08EB0B for ; Sun, 28 Jun 2020 23:18:53 -0700 (PDT) Received: by mail-pl1-x643.google.com with SMTP id x11so6683757plo.7 for ; Sun, 28 Jun 2020 23:18:53 -0700 (PDT) From: Kees Cook Subject: [PATCH v4 11/17] arm64/build: Warn on orphan section placement Date: Sun, 28 Jun 2020 23:18:34 -0700 Message-ID: <20200629061840.4065483-12-keescook@chromium.org> In-Reply-To: <20200629061840.4065483-1-keescook@chromium.org> References: <20200629061840.4065483-1-keescook@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Will Deacon Cc: Kees Cook , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Peter Collingbourne , James Morse , Borislav Petkov , Thomas Gleixner , Ingo Molnar , Russell King , Masahiro Yamada , Arvind Sankar , Nick Desaulniers , Nathan Chancellor , Arnd Bergmann , x86@kernel.org, clang-built-linux@googlegroups.com, linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Message-ID: <20200629061834.0I05gHwfDAqrGm84oVHfP9hHIl984QkUe8i6Rn9f3Lo@z> We don't want to depend on the linker's orphan section placement heuristics as these can vary between linkers, and may change between versions. All sections need to be explicitly named in the linker script. Remove .eh_frame, since there are none left. Add .plt, .data.rel.ro, .igot.*, and .iplt to discards as they are not actually used. While .got.plt is also not used, it must be included otherwise ld.bfd will fail to link with the error: aarch64-linux-gnu-ld: discarded output section: `.got.plt' However, as it'd be better to validate that it stays effectively empty, add an assert, as suggested by Ard Biesheuvel. Explicitly include debug sections when they're present. Finally, enable orphan section warnings. Acked-by: Will Deacon Signed-off-by: Kees Cook --- arch/arm64/Makefile | 4 ++++ arch/arm64/kernel/vmlinux.lds.S | 11 ++++++++++- 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 895486606f74..fb3aa2d7de4d 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -29,6 +29,10 @@ LDFLAGS_vmlinux += --fix-cortex-a53-843419 endif endif +# We never want expected sections to be placed heuristically by the +# linker. All sections should be explicitly named in the linker script. +LDFLAGS_vmlinux += --orphan-handling=warn + ifeq ($(CONFIG_ARM64_USE_LSE_ATOMICS), y) ifneq ($(CONFIG_ARM64_LSE_ATOMICS), y) $(warning LSE atomics not supported by binutils) diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index b5a94ec1eada..320ba5ec2adc 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -94,7 +94,8 @@ SECTIONS /DISCARD/ : { *(.interp .dynamic) *(.dynsym .dynstr .hash .gnu.hash) - *(.eh_frame) + *(.plt) *(.data.rel.ro) + *(.igot.*) *(.iplt) } . = KIMAGE_VADDR + TEXT_OFFSET; @@ -244,9 +245,17 @@ SECTIONS _end = .; STABS_DEBUG + DWARF_DEBUG ELF_DETAILS HEAD_SYMBOLS + + /* + * Make sure that the .got.plt is either completely empty or it + * contains only the lazy dispatch entries. + */ + .got.plt (INFO) : { *(.got.plt) } + ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, ".got.plt not empty") } #include "image-vars.h" -- 2.25.1