linux-kernel - Re: [PATCH] arch: um: Mark the stack non-executable to fix a binutils warning

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Date:   Fri, 26 Aug 2022 13:35:13 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     David Gow <davidgow@...gle.com>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Brendan Higgins <brendan.higgins@...ux.dev>,
        Daniel Latypov <dlatypov@...gle.com>,
        linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kunit-dev@...glegroups.com, x86@...nel.org
Subject: Re: [PATCH] arch: um: Mark the stack non-executable to fix a binutils
 warning



On 8/22/22 18:08, David Gow wrote:
> Since binutils 2.39, ld will print a warning if any stack section is
> executable, which is the default for stack sections on files without a
> .note.GNU-stack section.
> 
> This was fixed for x86 in commit ffcf9c5700e4 ("x86: link vdso and boot with -z noexecstack --no-warn-rwx-segments"),
> but remained broken for UML, resulting in several warnings:
> 
> /usr/bin/ld: warning: arch/x86/um/vdso/vdso.o: missing .note.GNU-stack section implies executable stack
> /usr/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
> /usr/bin/ld: warning: .tmp_vmlinux.kallsyms1 has a LOAD segment with RWX permissions
> /usr/bin/ld: warning: .tmp_vmlinux.kallsyms1.o: missing .note.GNU-stack section implies executable stack
> /usr/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
> /usr/bin/ld: warning: .tmp_vmlinux.kallsyms2 has a LOAD segment with RWX permissions
> /usr/bin/ld: warning: .tmp_vmlinux.kallsyms2.o: missing .note.GNU-stack section implies executable stack
> /usr/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
> /usr/bin/ld: warning: vmlinux has a LOAD segment with RWX permissions
> 
> Link both the VDSO and vmlinux with -z noexecstack, fixing the warnings
> about .note.GNU-stack sections. In addition, pass --no-warn-rwx-segments
> to dodge the remaining warnings about LOAD segments with RWX permissions
> in the kallsyms objects. (Note that this flag is apparently not
> available on lld, so hide it behind a test for BFD, which is what the
> x86 patch does.)
> 
> Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ffcf9c5700e49c0aee42dcba9a12ba21338e8136
> Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
> Signed-off-by: David Gow <davidgow@...gle.com>

Acked-by: Randy Dunlap <rdunlap@...radead.org> # build-tested

Thanks.

> ---
>  arch/um/Makefile          | 9 ++++++++-
>  arch/x86/um/vdso/Makefile | 2 +-
>  2 files changed, 9 insertions(+), 2 deletions(-)


-- 
~Randy