[PATCH] Makefile: Silence new GNU linker warnings

[PATCH] Makefile: Silence new GNU linker warnings

[Joel Stanley]

The next version of the linker will complain about rwx segments with
permissions and executable stacks:

 https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
 https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=0d38576a34ec64a1b4500c9277a8e9d0f07e6774

These warnings are relevant for ELF binaries loaded by an operating
system linker, but do not make sense in the context of u-boot where the
objects are loaded by other means.

Disable the warnings using the following options:

 --no-warn-rwx-segments

  warning: u-boot has a LOAD segment with RWX permissions
  warning: u-boot-spl has a LOAD segment with RWX permissions

 --no-warn-execstack

  warning: arch/arm/lib/setjmp.o: missing .note.GNU-stack section implies executable stack
  NOTE: This behaviour is deprecated and will be removed in a future version of the linker

Signed-off-by: Joel Stanley <joel@jms.id.au>
---
This behaviour can be seen when building with binutils
2.38.90.20220713-2 from Debian testing.

 Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index ff25f9297486..32aac7493f8d 100644
--- a/Makefile
+++ b/Makefile
@@ -432,7 +432,8 @@ KBUILD_CFLAGS   := -Wall -Wstrict-prototypes \
 		   -fno-builtin -ffreestanding $(CSTD_FLAG)
 KBUILD_CFLAGS	+= -fshort-wchar -fno-strict-aliasing
 KBUILD_AFLAGS   := -D__ASSEMBLY__
-KBUILD_LDFLAGS  :=
+KBUILD_LDFLAGS  := $(call ld-option, --no-warn-rwx-segments) \
+		   $(call ld-option, --no-warn-execstack)
 
 ifeq ($(cc-name),clang)
 ifneq ($(CROSS_COMPILE),)
-- 
2.35.1

Re: [PATCH] Makefile: Silence new GNU linker warnings

[Heinrich Schuchardt]

On 8/2/22 10:30, Joel Stanley wrote:
> The next version of the linker will complain about rwx segments with
> permissions and executable stacks:
>
>   https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
>   https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=0d38576a34ec64a1b4500c9277a8e9d0f07e6774
>
> These warnings are relevant for ELF binaries loaded by an operating
> system linker, but do not make sense in the context of u-boot where the
> objects are loaded by other means.

The ELF binary can be loaded by OpenSBI or QEMU. The information about
rwx segments can be relevant for these. Only if a non-ELF form is used
it is irrelevant.

You should instead fix the single file that has a problem:

test/overlay/test-fdt-overlay-stacked.dtb.S

Just add the missing section information or change the build flags for
this single binary.

Best regards

Heinrich


>
> Disable the warnings using the following options:
>
>   --no-warn-rwx-segments
>
>    warning: u-boot has a LOAD segment with RWX permissions
>    warning: u-boot-spl has a LOAD segment with RWX permissions
>
>   --no-warn-execstack
>
>    warning: arch/arm/lib/setjmp.o: missing .note.GNU-stack section implies executable stack
>    NOTE: This behaviour is deprecated and will be removed in a future version of the linker
>
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> ---
> This behaviour can be seen when building with binutils
> 2.38.90.20220713-2 from Debian testing.
>
>   Makefile | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index ff25f9297486..32aac7493f8d 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -432,7 +432,8 @@ KBUILD_CFLAGS   := -Wall -Wstrict-prototypes \
>   		   -fno-builtin -ffreestanding $(CSTD_FLAG)
>   KBUILD_CFLAGS	+= -fshort-wchar -fno-strict-aliasing
>   KBUILD_AFLAGS   := -D__ASSEMBLY__
> -KBUILD_LDFLAGS  :=
> +KBUILD_LDFLAGS  := $(call ld-option, --no-warn-rwx-segments) \
> +		   $(call ld-option, --no-warn-execstack)
>
>   ifeq ($(cc-name),clang)
>   ifneq ($(CROSS_COMPILE),)

Re: [PATCH] Makefile: Silence new GNU linker warnings

[Joel Stanley]

On Tue, 2 Aug 2022 at 10:45, Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:
>
> On 8/2/22 10:30, Joel Stanley wrote:
> > The next version of the linker will complain about rwx segments with
> > permissions and executable stacks:
> >
> >   https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
> >   https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=0d38576a34ec64a1b4500c9277a8e9d0f07e6774
> >
> > These warnings are relevant for ELF binaries loaded by an operating
> > system linker, but do not make sense in the context of u-boot where the
> > objects are loaded by other means.
>
> The ELF binary can be loaded by OpenSBI or QEMU. The information about
> rwx segments can be relevant for these. Only if a non-ELF form is used
> it is irrelevant.

I couldn't see where it was used in the qemu elf loader.

I had assumed the system would need an operating system and/or to be
running with a MMU turned on to do anything sensible with the
information.

>
> You should instead fix the single file that has a problem:
>
> test/overlay/test-fdt-overlay-stacked.dtb.S

I saw it triggering on a different set of files:

$ make evb-ast2600_defconfig && make CROSS_COMPILE=arm-linux-gnueabihf- -s -j8
#
# configuration written to .config
#
arm-linux-gnueabihf-ld.bfd: warning: arch/arm/lib/lib1funcs.o: missing
.note.GNU-stack section implies executable stack
arm-linux-gnueabihf-ld.bfd: NOTE: This behaviour is deprecated and
will be removed in a future version of the linker
arm-linux-gnueabihf-ld.bfd: warning: u-boot has a LOAD segment with
RWX permissions
arm-linux-gnueabihf-ld.bfd: warning: arch/arm/lib/lib1funcs.o: missing
.note.GNU-stack section implies executable stack
arm-linux-gnueabihf-ld.bfd: NOTE: This behaviour is deprecated and
will be removed in a future version of the linker
arm-linux-gnueabihf-ld.bfd: warning: u-boot-spl has a LOAD segment
with RWX permissions

Cheers,

Joel