linux-kernel - Re: [PATCH v4 09/10] powerpc/fsl_booke/kaslr: support nokaslr cmdline parameter

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Message-ID: <3a83c812-ac14-3e89-241e-eeade105d23e@huawei.com>
Date:   Wed, 7 Aug 2019 11:22:14 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     Christophe Leroy <christophe.leroy@....fr>, <mpe@...erman.id.au>,
        <linuxppc-dev@...ts.ozlabs.org>, <diana.craciun@....com>,
        <benh@...nel.crashing.org>, <paulus@...ba.org>,
        <npiggin@...il.com>, <keescook@...omium.org>,
        <kernel-hardening@...ts.openwall.com>
CC:     <linux-kernel@...r.kernel.org>, <wangkefeng.wang@...wei.com>,
        <yebin10@...wei.com>, <thunder.leizhen@...wei.com>,
        <jingxiangfeng@...wei.com>, <fanchengyang@...wei.com>,
        <zhaohongjiang@...wei.com>
Subject: Re: [PATCH v4 09/10] powerpc/fsl_booke/kaslr: support nokaslr cmdline
 parameter



On 2019/8/6 15:59, Christophe Leroy wrote:
> 
> 
> Le 05/08/2019 à 08:43, Jason Yan a écrit :
>> One may want to disable kaslr when boot, so provide a cmdline parameter
>> 'nokaslr' to support this.
>>
>> Signed-off-by: Jason Yan <yanaijie@...wei.com>
>> Cc: Diana Craciun <diana.craciun@....com>
>> Cc: Michael Ellerman <mpe@...erman.id.au>
>> Cc: Christophe Leroy <christophe.leroy@....fr>
>> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> Cc: Paul Mackerras <paulus@...ba.org>
>> Cc: Nicholas Piggin <npiggin@...il.com>
>> Cc: Kees Cook <keescook@...omium.org>
>> Reviewed-by: Diana Craciun <diana.craciun@....com>
>> Tested-by: Diana Craciun <diana.craciun@....com>
> 
> Reviewed-by: Christophe Leroy <christophe.leroy@....fr>
> 
> Tiny comment below.
> 
>> ---
>>   arch/powerpc/kernel/kaslr_booke.c | 14 ++++++++++++++
>>   1 file changed, 14 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/kaslr_booke.c 
>> b/arch/powerpc/kernel/kaslr_booke.c
>> index 4b3f19a663fc..7c3cb41e7122 100644
>> --- a/arch/powerpc/kernel/kaslr_booke.c
>> +++ b/arch/powerpc/kernel/kaslr_booke.c
>> @@ -361,6 +361,18 @@ static unsigned long __init 
>> kaslr_choose_location(void *dt_ptr, phys_addr_t size
>>       return kaslr_offset;
>>   }
>> +static inline __init bool kaslr_disabled(void)
>> +{
>> +    char *str;
>> +
>> +    str = strstr(boot_command_line, "nokaslr");
>> +    if ((str == boot_command_line) ||
>> +        (str > boot_command_line && *(str - 1) == ' '))
>> +        return true;
> 
> I don't think additional () are needed for the left part 'str == 
> boot_command_line'
> 

Agree.

>> +
>> +    return false;
>> +}
>> +
>>   /*
>>    * To see if we need to relocate the kernel to a random offset
>>    * void *dt_ptr - address of the device tree
>> @@ -376,6 +388,8 @@ notrace void __init kaslr_early_init(void *dt_ptr, 
>> phys_addr_t size)
>>       kernel_sz = (unsigned long)_end - KERNELBASE;
>>       kaslr_get_cmdline(dt_ptr);
>> +    if (kaslr_disabled())
>> +        return;
>>       offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
>>
> 
> .
>