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Subject: [PATCH] arm64: link with -z norelro for LLD or aarch64-elf
From:   Nick Desaulniers <ndesaulniers@google.com>
To:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>
Cc:     kernel-team <kernel-team@android.com>,
        Peter Smith <Peter.Smith@arm.com>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        stable <stable@vger.kernel.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        "=?UTF-8?q?F=C4=81ng-ru=C3=AC=20S=C3=B2ng?=" <maskray@google.com>,
        Quentin Perret <qperret@google.com>,
        Alan Modra <amodra@gmail.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        "kernelci . org bot" <bot@kernelci.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
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With newer GNU binutils, linking with BFD produces warnings for vmlinux:
aarch64-linux-gnu-ld: warning: -z norelro ignored

BFD can produce this warning when the target emulation mode does not
support RELRO relocation types, and -z relro or -z norelro is passed.

Alan Modra clarifies:
  The default linker emulation for an aarch64-linux ld.bfd is
  -maarch64linux, the default for an aarch64-elf linker is
  -maarch64elf.  They are not equivalent.  If you choose -maarch64elf
  you get an emulation that doesn't support -z relro.

The ARCH=3Darm64 kernel prefers -maarch64elf, but may fall back to
-maarch64linux based on the toolchain configuration.

LLD will always create RELRO relocation types regardless of target
emulation.

To avoid the above warning when linking with BFD, pass -z norelro only
when linking with LLD or with -maarch64linux.

Cc: Alan Modra <amodra@gmail.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: F=C4=81ng-ru=C3=AC S=C3=B2ng <maskray@google.com>
Fixes: 3b92fa7485eb ("arm64: link with -z norelro regardless of CONFIG_RELO=
CATABLE")
Reported-by: kernelci.org bot <bot@kernelci.org>
Reported-by: Quentin Perret <qperret@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 arch/arm64/Makefile | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 6be9b3750250..90309208bb28 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -10,7 +10,7 @@
 #
 # Copyright (C) 1995-2001 by Russell King
=20
-LDFLAGS_vmlinux	:=3D--no-undefined -X -z norelro
+LDFLAGS_vmlinux	:=3D--no-undefined -X
=20
 ifeq ($(CONFIG_RELOCATABLE), y)
 # Pass --no-apply-dynamic-relocs to restore pre-binutils-2.27 behaviour
@@ -115,16 +115,20 @@ KBUILD_CPPFLAGS	+=3D -mbig-endian
 CHECKFLAGS	+=3D -D__AARCH64EB__
 # Prefer the baremetal ELF build target, but not all toolchains include
 # it so fall back to the standard linux version if needed.
-KBUILD_LDFLAGS	+=3D -EB $(call ld-option, -maarch64elfb, -maarch64linuxb)
+KBUILD_LDFLAGS	+=3D -EB $(call ld-option, -maarch64elfb, -maarch64linuxb -=
z norelro)
 UTS_MACHINE	:=3D aarch64_be
 else
 KBUILD_CPPFLAGS	+=3D -mlittle-endian
 CHECKFLAGS	+=3D -D__AARCH64EL__
 # Same as above, prefer ELF but fall back to linux target if needed.
-KBUILD_LDFLAGS	+=3D -EL $(call ld-option, -maarch64elf, -maarch64linux)
+KBUILD_LDFLAGS	+=3D -EL $(call ld-option, -maarch64elf, -maarch64linux -z =
norelro)
 UTS_MACHINE	:=3D aarch64
 endif
=20
+ifeq ($(CONFIG_LD_IS_LLD), y)
+KBUILD_LDFLAGS	+=3D -z norelro
+endif
+
 CHECKFLAGS	+=3D -D__aarch64__
=20
 ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_REGS),y)
--=20
2.29.2.684.gfbc64c5ab5-goog