linux-kernel - Re: [PATCH v15 2/6] x86/boot: Introduce get_acpi_rsdp() to parse RSDP in cmdline from KEXEC

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Date:   Fri, 11 Jan 2019 09:17:36 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
        <keescook@...omium.org>, <bhe@...hat.com>, <msys.mizuma@...il.com>,
        <indou.takao@...fujitsu.com>, <caoj.fnst@...fujitsu.com>
Subject: Re: [PATCH v15 2/6] x86/boot: Introduce get_acpi_rsdp() to parse
 RSDP in cmdline from KEXEC

On Thu, Jan 10, 2019 at 06:01:03PM +0100, Borislav Petkov wrote:
>On Mon, Jan 07, 2019 at 11:22:39AM +0800, Chao Fan wrote:
>> KASLR may randomly choose some positions which are located in movable
>> memory regions. This will make the movable memory chosen by KASLR
>> can't be removed.
>> 
>> Memory information in SRAT is necessary to fix the conflict between
>> KASLR and memory-hotremove.
>> 
>> ACPI SRAT (System/Static Resource Affinity Table) shows the details
>> about memory ranges, including ranges of memory provided by hot-added
>> memory devices. SRAT is introduced by Root System Description
>> Pointer(RSDP). So RSDP should be found firstly.
>> 
>> When booting form KEXEC/EFI/BIOS, the methods to find RSDP
>> are different. When booting from KEXEC, 'acpi_rsdp=' may have been
>> added to cmdline, so parse cmdline to find RSDP.
>> 
>> Signed-off-by: Chao Fan <fanc.fnst@...fujitsu.com>
>> ---
>>  arch/x86/boot/compressed/acpi.c | 30 ++++++++++++++++++++++++++++++
>>  1 file changed, 30 insertions(+)
>>  create mode 100644 arch/x86/boot/compressed/acpi.c
>> 
>> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
>> new file mode 100644
>> index 000000000000..7ca5001d7639
>> --- /dev/null
>> +++ b/arch/x86/boot/compressed/acpi.c
>> @@ -0,0 +1,30 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +#define BOOT_CTYPE_H
>> +#include "misc.h"
>> +#include "error.h"
>> +#include "../string.h"
>> +
>> +#include <linux/acpi.h>
>
>Ok, I corrected it to this, please replace in your version:
>
>/*
> * Max length of 64-bit hex address string is 19, prefix "0x" + 16 hex
> * digits, and '\0' for termination.
> */
>#define MAX_ADDR_LEN 19
>
>static acpi_physical_address get_acpi_rsdp(void)
>{
>	acpi_physical_address addr = 0;
>
>#ifdef CONFIG_KEXEC
>	char val[MAX_ADDR_LEN] = { };
>	int ret;
>
>	ret = cmdline_find_option("acpi_rsdp", val, MAX_ADDR_LEN);
>	if (ret < 0)
>		return 0;
>
>	if (kstrtoull(val, 16, &addr))
>		return 0;
>#endif
>	return addr;
>}
>

Thanks for your suggestion, will change it.

Thanks,
Chao Fan

>
>-- 
>Regards/Gruss,
>    Boris.
>
>Good mailing practices for 400: avoid top-posting and trim the reply.
>
>