linux-kernel - Re: [PATCH 5/5] x86/kernel: jump

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Message-ID: <20180628083107.GY2494@hirez.programming.kicks-ass.net>
Date:   Thu, 28 Jun 2018 10:31:07 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org, Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        Steven Rostedt <rostedt@...dmis.org>, namit@...are.com
Subject: Re: [PATCH 5/5] x86/kernel: jump_table: use relative references

On Wed, Jun 27, 2018 at 06:06:04PM +0200, Ard Biesheuvel wrote:
> Similar to the arm64 case, 64-bit x86 can benefit from using 32-bit
> relative references rather than 64-bit absolute ones when emitting
> struct jump_entry instances. Not only does this reduce the memory
> footprint of the entries themselves by 50%, it also removes the need
> for carrying relocation metadata on relocatable builds (i.e., for KASLR)
> which saves a fair chunk of .init space as well (although the savings
> are not as dramatic as on arm64)

This will conflict with:

  https://lkml.kernel.org/r/20180622172212.199633-10-namit@vmware.com