linux-kernel - Re: [PATCH v5 3/4] x86/boot/KASLR: Walk srat tables to filter immovable memory

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Message-ID: <20180827025611.GC6769@localhost.localdomain>
Date:   Mon, 27 Aug 2018 10:56:12 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Baoquan He <bhe@...hat.com>
CC:     <tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
        <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <keescook@...omium.org>, <n-horiguchi@...jp.nec.com>,
        <indou.takao@...fujitsu.com>, <caoj.fnst@...fujitsu.com>,
        <douly.fnst@...fujitsu.com>
Subject: Re: [PATCH v5 3/4] x86/boot/KASLR: Walk srat tables to filter
 immovable memory

On Mon, Aug 27, 2018 at 10:13:49AM +0800, Baoquan He wrote:
>On 08/07/18 at 02:49pm, Chao Fan wrote:
>> If 'CONFIG_MEMORY_HOTREMOVE' specified, walk the acpi srat memory
>> tables, store the immovable memory regions, so that kaslr can get
>> the information abouth where can be selected or not.
>> If 'CONFIG_MEMORY_HOTREMOVE' not specified, go on the old code.
>Just adjust the patch log a little bit, just for your reference.
>
>If 'CONFIG_MEMORY_HOTREMOVE' specified, walk through the acpi srat memory
>tables and store those immovable memory regions so that kaslr can get
>where to choose for randomization.

OK, I will change more patch log in next version.

>
>> 

[...]

>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/*
>> + * According to ACPI table, filter the immvoable memory regions
>> + * and store them in immovable_mem[].
>> + */
>> +static void handle_immovable_mem(void)
>
>Can we change this function like below, passed in the immovable_mem and
>the array lengty, the value of num_immovable_mem will be passed back?
>
>static void handle_immovable_mem(char* region, int max, int *num)
>{
>}
>
>Like this, you don't need patch 1/4 to make a header file, just put this
>function handle_immovable_mem() into acpitb.c since it's handling acpi
>tables. And its name can be get_immovable_mem().

That makes sense.
But if we change like this, we can put the whole function to acpitb.c.
It will be like:
static void handle_immovable_mem(int *num)
{
}
Because the value of immovable_mem is filled in handle_immovable_mem,
it's better to put immovable_mem in acpitb.c also, then extern in
kaslr.c.

Thanks,
Chao Fan