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

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Date:   Wed, 4 May 2022 12:03:35 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.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>
> ---
>  arch/x86/include/asm/setup.h | 30 +++++++++++-------------------
>  1 file changed, 11 insertions(+), 19 deletions(-)

Nice.

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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