linux-kernel - Re: [PATCH] x86/mm: Do not shuffle CPU entry areas without KASLR

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Date:   Fri, 3 Mar 2023 13:24:53 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Michal Koutný <mkoutny@...e.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/mm: Do not shuffle CPU entry areas without KASLR

On 3/3/23 08:06, Michal Koutný wrote:
> @@ -29,6 +30,12 @@ static __init void init_cea_offsets(void)
>  	unsigned int max_cea;
>  	unsigned int i, j;
>  
> +	if (!kaslr_memory_enabled()) {
> +		for_each_possible_cpu(i)
> +			per_cpu(_cea_offset, i) = i;
> +		return;
> +	}

Should this be kaslr_memory_enabled() or kaslr_enabled()?

The delta seems to be CONFIG_KASAN, and the cpu entry area randomization
works just fine with KASAN after some recent fixes.  I _think_ that
makes cpu entry area randomization more like module randomization which
would point toward kaslr_enabled().