linux-kernel - Re: [PATCH 0/2] Stop generating .eh

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Date:   Mon, 24 Feb 2020 16:53:31 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Borislav Petkov <bp@...en8.de>,
        Nathan Chancellor <natechancellor@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Michael Matz <matz@...e.de>, Fangrui Song <maskray@...gle.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 0/2] Stop generating .eh_frame sections

On Mon, Feb 24, 2020 at 12:49:03PM -0800, Nick Desaulniers wrote:
> On Sun, Feb 23, 2020 at 11:37 AM Arvind Sankar <nivedita@...m.mit.edu> wrote:
> >
> > In three places in the x86 kernel we are currently generating .eh_frame
> > sections only to discard them later via linker script. This is in the
> > boot code (setup.elf), the realmode trampoline (realmode.elf) and the
> > compressed kernel.
> >
> > Implement Fangrui and Nick's suggestion [1] to fix KBUILD_CFLAGS by
> > adding -fno-asynchronous-unwind-tables to avoid generating .eh_frame
> > sections in the first place, rather than discarding it in the linker
> > script.
> >
> > Arvind Sankar (2):
> >   arch/x86: Use -fno-asynchronous-unwind-tables to suppress .eh_frame sections
> >   arch/x86: Drop unneeded linker script discard of .eh_frame
> 
> Thanks for the series! I've left some feedback for a v2. Would you
> mind please including a revert of ("x86/boot/compressed: Remove
> unnecessary sections from bzImage") in a v2 series?  Our CI being red
> through the weekend is no bueno.

Sorry about that. Boris already updated tip:x86/boot to only discard
eh_frame, so your CI should be ok at least now.

> 
> >
> >  arch/x86/boot/Makefile                | 1 +
> >  arch/x86/boot/compressed/Makefile     | 1 +
> >  arch/x86/boot/setup.ld                | 1 -
> >  arch/x86/kernel/vmlinux.lds.S         | 3 ---
> >  arch/x86/realmode/rm/Makefile         | 1 +
> >  arch/x86/realmode/rm/realmode.lds.S   | 1 -
> >  drivers/firmware/efi/libstub/Makefile | 3 ++-
> >  7 files changed, 5 insertions(+), 6 deletions(-)
> >
> > --
> > 2.24.1
> >
> 
> 
> -- 
> Thanks,
> ~Nick Desaulniers