linux-kernel - Re: [PATCH v2] x86: Avoid relocation information in final vmlinux

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Date:   Thu, 24 Nov 2022 13:38:26 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Petr Pavlu <petr.pavlu@...e.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, nicolas@...sle.eu,
        masahiroy@...nel.org, kirill.shutemov@...ux.intel.com,
        tony.luck@...el.com, michael.roth@....com, nathan@...nel.org,
        ndesaulniers@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86: Avoid relocation information in final vmlinux

On Thu, Nov 24, 2022 at 10:21:33AM +0100, Petr Pavlu wrote:
> Option CONFIG_RANDOMIZE_BASE=y needs to be enabled. Switching it on should
> automatically select also CONFIG_X86_NEED_RELOCS=y which is what actually
> enables use of --emit-relocs in arch/x86/Makefile.

Yeah, as I said in my previous mail:

"and before and after .configs simply have RANDOMIZE_BASE =n and =y,
respectively."

I just did it again to make sure:

-rwxr-xr-x 1 boris boris 377666112 Nov 24 13:28 vmlinux.before
-rwxr-xr-x 1 boris boris 377718768 Nov 24 13:33 vmlinux.after

With

$ grep -E "(NEED_RELOCS|RANDOMIZE)" .config
CONFIG_RANDOMIZE_BASE=y
CONFIG_X86_NEED_RELOCS=y
CONFIG_RANDOMIZE_MEMORY=y
CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING=0x0
CONFIG_ARCH_HAS_ELF_RANDOMIZE=y
CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET=y
CONFIG_RANDOMIZE_KSTACK_OFFSET=y

that second vmlinux file is even a bit larger (~51K) ...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette