linux-kernel - Re: [PATCH] x86/mm: Simplify RESERVE

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Message-ID: <Ymu5e24d3JRWJdHb@hirez.programming.kicks-ass.net>
Date:   Fri, 29 Apr 2022 12:10:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/mm: Simplify RESERVE_BRK()

On Thu, Apr 28, 2022 at 01:04:25PM -0700, Josh Poimboeuf wrote:
> RESERVE_BRK() reserves data in the .brk_reservation section.  The data
> is initialized to zero, like BSS, so the macro specifies 'nobits' to
> prevent the data from taking up space in the vmlinux binary.  The only
> way to get the compiler to do that (without putting the variable in .bss
> proper) is to use inline asm.
> 
> The macro also has a hack which encloses the inline asm in a discarded
> function, which allows the size to be passed (global inline asm doesn't
> allow inputs).
> 
> Remove the need for the discarded function hack by just stringifying the
> size rather than supplying it as an input to the inline asm.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>

Tested-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>