diff mbox series

[v5.4] arm64: link with -z norelro for LLD or aarch64-elf

Message ID 20210624170919.3d018a1a@xhacker.debian
State Superseded
Headers show
Series [v5.4] arm64: link with -z norelro for LLD or aarch64-elf | expand

Commit Message

Jisheng Zhang June 24, 2021, 9:09 a.m. UTC
From: Nick Desaulniers <ndesaulniers@google.com>


commit 311bea3cb9ee20ef150ca76fc60a592bf6b159f5 upstream.

With GNU binutils 2.35+, 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 program headers, 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=arm64 kernel prefers -maarch64elf, but may fall back to
-maarch64linux based on the toolchain configuration.

LLD will always create RELRO program header regardless of target
emulation.

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

Fixes: 3b92fa7485eb ("arm64: link with -z norelro regardless of CONFIG_RELOCATABLE")
Fixes: 3bbd3db86470 ("arm64: relocatable: fix inconsistencies in linker script and options")
Cc: <stable@vger.kernel.org> # 5.0.x-
Reported-by: kernelci.org bot <bot@kernelci.org>
Reported-by: Quentin Perret <qperret@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

Cc: Alan Modra <amodra@gmail.com>
Cc: Fāng-ruì Sòng <maskray@google.com>
Link: https://lore.kernel.org/r/20201218002432.788499-1-ndesaulniers@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

---
 arch/arm64/Makefile | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

-- 
2.32.0

Comments

Nick Desaulniers June 24, 2021, 7:14 p.m. UTC | #1
On Thu, Jun 24, 2021 at 2:09 AM Jisheng Zhang
<Jisheng.Zhang@synaptics.com> wrote:
>

> From: Nick Desaulniers <ndesaulniers@google.com>

>

> commit 311bea3cb9ee20ef150ca76fc60a592bf6b159f5 upstream.

>

> With GNU binutils 2.35+, 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 program headers, 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=arm64 kernel prefers -maarch64elf, but may fall back to

> -maarch64linux based on the toolchain configuration.

>

> LLD will always create RELRO program header regardless of target

> emulation.

>

> To avoid the above warning when linking with BFD, pass -z norelro only

> when linking with LLD or with -maarch64linux.

>

> Fixes: 3b92fa7485eb ("arm64: link with -z norelro thank you regardless of CONFIG_RELOCATABLE")


^ exists in 5.4 as 57a88e44b512

> Fixes: 3bbd3db86470 ("arm64: relocatable: fix inconsistencies in linker script and options")


^ landed in v5.0-rc1

> Cc: <stable@vger.kernel.org> # 5.0.x-

> Reported-by: kernelci.org bot <bot@kernelci.org>

> Reported-by: Quentin Perret <qperret@google.com>

> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> Acked-by: Ard Biesheuvel <ardb@kernel.org>

> Cc: Alan Modra <amodra@gmail.com>

> Cc: Fāng-ruì Sòng <maskray@google.com>

> Link: https://lore.kernel.org/r/20201218002432.788499-1-ndesaulniers@google.com

> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

> ---

>  arch/arm64/Makefile | 10 +++++++---

>  1 file changed, 7 insertions(+), 3 deletions(-)

>

> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile

> index cd8f3cdabfd0..d227cf87c48f 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

>  CPPFLAGS_vmlinux.lds = -DTEXT_OFFSET=$(TEXT_OFFSET)

>  GZFLAGS                :=-9

>

> @@ -82,17 +82,21 @@ CHECKFLAGS  += -D__AARCH64EB__

>  AS             += -EB

>  # Prefer the baremetal ELF build target, but not all toolchains include

>  # it so fall back to the standard linux version if needed.

> -KBUILD_LDFLAGS += -EB $(call ld-option, -maarch64elfb, -maarch64linuxb)

> +KBUILD_LDFLAGS += -EB $(call ld-option, -maarch64elfb, -maarch64linuxb -z norelro)

>  UTS_MACHINE    := aarch64_be

>  else

>  KBUILD_CPPFLAGS        += -mlittle-endian

>  CHECKFLAGS     += -D__AARCH64EL__

>  AS             += -EL

>  # Same as above, prefer ELF but fall back to linux target if needed.

> -KBUILD_LDFLAGS += -EL $(call ld-option, -maarch64elf, -maarch64linux)

> +KBUILD_LDFLAGS += -EL $(call ld-option, -maarch64elf, -maarch64linux -z norelro)

>  UTS_MACHINE    := aarch64

>  endif

>

> +ifeq ($(CONFIG_LD_IS_LLD), y)

> +KBUILD_LDFLAGS += -z norelro

> +endif


^ ah but 5.4 doesn't have
commit b744b43f79cc ("kbuild: add CONFIG_LD_IS_LLD")
which landed in v5.8-rc1. So this patch will break LLD on 5.4. That
should be trivial to backport, but would you please send that first,
then this?

> +

>  CHECKFLAGS     += -D__aarch64__

>

>  ifeq ($(CONFIG_ARM64_MODULE_PLTS),y)

> --

> 2.32.0

>



--
Thanks,
~Nick Desaulniers
Greg KH June 25, 2021, 10:09 a.m. UTC | #2
On Thu, Jun 24, 2021 at 05:09:19PM +0800, Jisheng Zhang wrote:
> From: Nick Desaulniers <ndesaulniers@google.com>

> 

> commit 311bea3cb9ee20ef150ca76fc60a592bf6b159f5 upstream.

> 

> With GNU binutils 2.35+, 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 program headers, 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=arm64 kernel prefers -maarch64elf, but may fall back to

> -maarch64linux based on the toolchain configuration.

> 

> LLD will always create RELRO program header regardless of target

> emulation.

> 

> To avoid the above warning when linking with BFD, pass -z norelro only

> when linking with LLD or with -maarch64linux.

> 

> Fixes: 3b92fa7485eb ("arm64: link with -z norelro regardless of CONFIG_RELOCATABLE")

> Fixes: 3bbd3db86470 ("arm64: relocatable: fix inconsistencies in linker script and options")

> Cc: <stable@vger.kernel.org> # 5.0.x-

> Reported-by: kernelci.org bot <bot@kernelci.org>

> Reported-by: Quentin Perret <qperret@google.com>

> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> Acked-by: Ard Biesheuvel <ardb@kernel.org>

> Cc: Alan Modra <amodra@gmail.com>

> Cc: Fāng-ruì Sòng <maskray@google.com>

> Link: https://lore.kernel.org/r/20201218002432.788499-1-ndesaulniers@google.com

> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

> ---

>  arch/arm64/Makefile | 10 +++++++---

>  1 file changed, 7 insertions(+), 3 deletions(-)


Now queued up, thanks.

greg k-h
Jisheng Zhang June 25, 2021, 10:12 a.m. UTC | #3
Hi Greg,

On Fri, 25 Jun 2021 12:09:33 +0200
Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:


> 

> On Thu, Jun 24, 2021 at 05:09:19PM +0800, Jisheng Zhang wrote:

> > From: Nick Desaulniers <ndesaulniers@google.com>

> >

> > commit 311bea3cb9ee20ef150ca76fc60a592bf6b159f5 upstream.

> >

> > With GNU binutils 2.35+, 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 program headers, 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=arm64 kernel prefers -maarch64elf, but may fall back to

> > -maarch64linux based on the toolchain configuration.

> >

> > LLD will always create RELRO program header regardless of target

> > emulation.

> >

> > To avoid the above warning when linking with BFD, pass -z norelro only

> > when linking with LLD or with -maarch64linux.

> >

> > Fixes: 3b92fa7485eb ("arm64: link with -z norelro regardless of CONFIG_RELOCATABLE")

> > Fixes: 3bbd3db86470 ("arm64: relocatable: fix inconsistencies in linker script and options")

> > Cc: <stable@vger.kernel.org> # 5.0.x-

> > Reported-by: kernelci.org bot <bot@kernelci.org>

> > Reported-by: Quentin Perret <qperret@google.com>

> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

> > Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> > Acked-by: Ard Biesheuvel <ardb@kernel.org>

> > Cc: Alan Modra <amodra@gmail.com>

> > Cc: Fāng-ruì Sòng <maskray@google.com>


> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

> > ---

> >  arch/arm64/Makefile | 10 +++++++---

> >  1 file changed, 7 insertions(+), 3 deletions(-)  

> 

> Now queued up, thanks.

> 


I assume the two patches in v2 series are queued up. Nick pointed out
applying only this patch can break kernel building with lld.

Thanks
Greg KH June 25, 2021, 10:25 a.m. UTC | #4
On Fri, Jun 25, 2021 at 06:12:30PM +0800, Jisheng Zhang wrote:
> Hi Greg,

> 

> On Fri, 25 Jun 2021 12:09:33 +0200

> Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:

> 

> 

> > 

> > On Thu, Jun 24, 2021 at 05:09:19PM +0800, Jisheng Zhang wrote:

> > > From: Nick Desaulniers <ndesaulniers@google.com>

> > >

> > > commit 311bea3cb9ee20ef150ca76fc60a592bf6b159f5 upstream.

> > >

> > > With GNU binutils 2.35+, 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 program headers, 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=arm64 kernel prefers -maarch64elf, but may fall back to

> > > -maarch64linux based on the toolchain configuration.

> > >

> > > LLD will always create RELRO program header regardless of target

> > > emulation.

> > >

> > > To avoid the above warning when linking with BFD, pass -z norelro only

> > > when linking with LLD or with -maarch64linux.

> > >

> > > Fixes: 3b92fa7485eb ("arm64: link with -z norelro regardless of CONFIG_RELOCATABLE")

> > > Fixes: 3bbd3db86470 ("arm64: relocatable: fix inconsistencies in linker script and options")

> > > Cc: <stable@vger.kernel.org> # 5.0.x-

> > > Reported-by: kernelci.org bot <bot@kernelci.org>

> > > Reported-by: Quentin Perret <qperret@google.com>

> > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

> > > Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> > > Acked-by: Ard Biesheuvel <ardb@kernel.org>

> > > Cc: Alan Modra <amodra@gmail.com>

> > > Cc: Fāng-ruì Sòng <maskray@google.com>

> 

> > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

> > > ---

> > >  arch/arm64/Makefile | 10 +++++++---

> > >  1 file changed, 7 insertions(+), 3 deletions(-)  

> > 

> > Now queued up, thanks.

> > 

> 

> I assume the two patches in v2 series are queued up. Nick pointed out

> applying only this patch can break kernel building with lld.


Yes, I now took those instead, thanks.

greg k-h
diff mbox series

Patch

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index cd8f3cdabfd0..d227cf87c48f 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
 CPPFLAGS_vmlinux.lds = -DTEXT_OFFSET=$(TEXT_OFFSET)
 GZFLAGS		:=-9
 
@@ -82,17 +82,21 @@  CHECKFLAGS	+= -D__AARCH64EB__
 AS		+= -EB
 # Prefer the baremetal ELF build target, but not all toolchains include
 # it so fall back to the standard linux version if needed.
-KBUILD_LDFLAGS	+= -EB $(call ld-option, -maarch64elfb, -maarch64linuxb)
+KBUILD_LDFLAGS	+= -EB $(call ld-option, -maarch64elfb, -maarch64linuxb -z norelro)
 UTS_MACHINE	:= aarch64_be
 else
 KBUILD_CPPFLAGS	+= -mlittle-endian
 CHECKFLAGS	+= -D__AARCH64EL__
 AS		+= -EL
 # Same as above, prefer ELF but fall back to linux target if needed.
-KBUILD_LDFLAGS	+= -EL $(call ld-option, -maarch64elf, -maarch64linux)
+KBUILD_LDFLAGS	+= -EL $(call ld-option, -maarch64elf, -maarch64linux -z norelro)
 UTS_MACHINE	:= aarch64
 endif
 
+ifeq ($(CONFIG_LD_IS_LLD), y)
+KBUILD_LDFLAGS	+= -z norelro
+endif
+
 CHECKFLAGS	+= -D__aarch64__
 
 ifeq ($(CONFIG_ARM64_MODULE_PLTS),y)