linux-kernel - Re: [PATCH] x86/kaslr: remove useless code in mem_avoid

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Message-ID: <20190822132628.GA3887@MiWiFi-R3L-srv>
Date:   Thu, 22 Aug 2019 21:26:28 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Qian Cai <cai@....pw>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/kaslr: remove useless code in mem_avoid_memmap

On 08/22/19 at 08:32am, Qian Cai wrote:
> MAX_MEMMAP_REGIONS is a macro that equal to 4. "i" is static local
> variable that default to 0. The comparison "i >= MAX_MEMMAP_REGIONS"
> will always be false.

Seems not true. mem_avoid_memmap() could be invoked many times if
multiple memmap= added. It will carry the value accumulated from
the past.

> 
> Signed-off-by: Qian Cai <cai@....pw>
> ---
>  arch/x86/boot/compressed/kaslr.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 2e53c056ba20..a4a5a88edb94 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -176,9 +176,6 @@ static void mem_avoid_memmap(char *str)
>  {
>  	static int i;
>  
> -	if (i >= MAX_MEMMAP_REGIONS)
> -		return;
> -
>  	while (str && (i < MAX_MEMMAP_REGIONS)) {
>  		int rc;
>  		unsigned long long start, size;
> -- 
> 1.8.3.1
>