linux-kernel - Re: [PATCH v2] powerpc/vdso: link with -z noexecstack

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Message-Id: <CMPW28H38HE0.W6BB976O6ULP@bobo>
Date:   Wed, 07 Sep 2022 14:36:21 +1000
From:   "Nicholas Piggin" <npiggin@...il.com>
To:     "Christophe Leroy" <christophe.leroy@...roup.eu>,
        "Michael Ellerman" <mpe@...erman.id.au>
Cc:     <linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v2] powerpc/vdso: link with -z noexecstack

On Sat Sep 3, 2022 at 1:25 AM AEST, Christophe Leroy wrote:
> With recent binutils, the following warning appears:
>
>   VDSO32L arch/powerpc/kernel/vdso/vdso32.so.dbg
> /opt/gcc-12.2.0-nolibc/powerpc64-linux/bin/../lib/gcc/powerpc64-linux/12.2.0/../../../../powerpc64-linux/bin/ld: warning: arch/powerpc/kernel/vdso/getcpu-32.o: missing .note.GNU-stack section implies executable stack
> /opt/gcc-12.2.0-nolibc/powerpc64-linux/bin/../lib/gcc/powerpc64-linux/12.2.0/../../../../powerpc64-linux/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
>
> To avoid that, explicitely tell the linker we don't
> want executable stack.
>
> For more explanations, see commit ffcf9c5700e4 ("x86: link vdso
> and boot with -z noexecstack --no-warn-rwx-segments")
>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
> v2: Removed unrelated change in arch/powerpc/kernel/Makefile

Seems okay. Here too, commit 0d362be5b1420 ("Makefile: link with -z
noexecstack --no-warn-rwx-segments"). Core and x86 are using
no-warn-rwx-segments as well, should we have that just to match
too?

Reviewed-by: Nicholas Piggin <npiggin@...il.com>

> ---
>  arch/powerpc/kernel/vdso/Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> index 096b0bf1335f..a2e7b0ce5b19 100644
> --- a/arch/powerpc/kernel/vdso/Makefile
> +++ b/arch/powerpc/kernel/vdso/Makefile
> @@ -92,13 +92,13 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
>  
>  # actual build commands
>  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) ; $(cmd_vdso_check)
> +      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
>  quiet_cmd_vdso32as = VDSO32A $@
>        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
>  quiet_cmd_vdso32cc = VDSO32C $@
>        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
>  
>  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) ; $(cmd_vdso_check)
> +      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
>  quiet_cmd_vdso64as = VDSO64A $@
>        cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
> -- 
> 2.37.1