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

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Message-ID: <7DA74EEE-45F1-4F84-807A-3C04551DF6F4@zytor.com>
Date:   Wed, 23 Nov 2022 09:45:37 -0800
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Borislav Petkov <bp@...en8.de>, Petr Pavlu <petr.pavlu@...e.com>
CC:     tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
        x86@...nel.org, 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 November 23, 2022 7:54:29 AM PST, Borislav Petkov <bp@...en8.de> wrote:
>On Wed, Nov 23, 2022 at 04:43:20PM +0100, Petr Pavlu wrote:
>> The only post-link analysis tool in this case should be arch/x86/tools/relocs.
>> It produces a vmlinux.relocs file which is appended to vmlinux.bin. This is
>> all internal to the Linux build. I'm not aware of any external tooling, such
>> as kernel debuggers, that would require this relocation information in
>> vmlinux.
>
>It would be good to know why --emit-relocs was added in the first place
>- that might give us a hint. Lemme talk to Micha.
>
>> The size command used in your example includes only allocatable code, data and
>> bss sections. It does not show size of any relocation sections.
>
>This:
>
>361M vmlinux.before
>361M vmlinux.after
>
>is simple ls output.
>
>Maybe I need something else enabled in my .config which would show this
>significant difference *and* *explain* it.
>
>Thx.
>

The real question is: why does anyone care about the size of the vmlinux file specifically?