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Message-Id: <20201112183839.1009297-1-natechancellor@gmail.com>
Date: Thu, 12 Nov 2020 11:38:40 -0700
From: Nathan Chancellor <natechancellor@...il.com>
To: Masahiro Yamada <masahiroy@...nel.org>,
Michal Marek <michal.lkml@...kovi.net>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Russell King <linux@...linux.org.uk>
Cc: Florian Fainelli <f.fainelli@...il.com>,
Arnd Bergmann <arnd@...db.de>,
Abbott Liu <liuwenliang@...wei.com>,
Linus Walleij <linus.walleij@...aro.org>,
Jian Cai <jiancai@...gle.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Ard Biesheuvel <ardb@...nel.org>, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
Nathan Chancellor <natechancellor@...il.com>,
Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH] kbuild: Always link with '-z norelro'
Commit 3bbd3db86470 ("arm64: relocatable: fix inconsistencies in linker
script and options") added '-z norelro' to the arm64 Makefile when
CONFIG_RELOCATABLE was set to help support ld.lld because ld.lld
defaults to '-z relro' but the kernel does not use program headers or
adhere to the section layout that is required for RELRO to work.
Commit 3b92fa7485eb ("arm64: link with -z norelro regardless of
CONFIG_RELOCATABLE") unconditionally added it to LDFLAGS_vmlinux because
an error occurs with CONFIG_KASAN set even when CONFIG_RELOCATABLE is
unset.
As it turns out, ARM experiences the same error after CONFIG_KASAN was
implemented, meaning that '-z norelro' needs to be added to that
Makefile as well (multi_v7_defconfig + CONFIG_KASAN=y + LD=ld.lld):
$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- LLVM=1 zImage
ld.lld: error: section: .exit.data is not contiguous with other relro sections
To avoid playing whack-a-mole with different architectures over time,
hoist '-z norelro' into the main Makefile. This does not affect ld.bfd
because '-z norelro' is the default for it.
Link: https://github.com/ClangBuiltLinux/linux/issues/1189
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
Hi all,
This should probably go into Russell's tree with acks from the arm64 and
kbuild maintainers.
Cheers,
Nathan
Makefile | 2 ++
arch/arm64/Makefile | 2 +-
2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index 008aba5f1a20..648bfb486244 100644
--- a/Makefile
+++ b/Makefile
@@ -984,6 +984,8 @@ ifeq ($(CONFIG_RELR),y)
LDFLAGS_vmlinux += --pack-dyn-relocs=relr
endif
+LDFLAGS_vmlinux += -z norelro
+
# Align the bit size of userspace programs with the kernel
KBUILD_USERCFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))
KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 5789c2d18d43..85495ff8f0fd 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -10,7 +10,7 @@
#
# Copyright (C) 1995-2001 by Russell King
-LDFLAGS_vmlinux :=--no-undefined -X -z norelro
+LDFLAGS_vmlinux :=--no-undefined -X
ifeq ($(CONFIG_RELOCATABLE), y)
# Pass --no-apply-dynamic-relocs to restore pre-binutils-2.27 behaviour
base-commit: f8394f232b1eab649ce2df5c5f15b0e528c92091
--
2.29.2
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