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Date: Mon, 29 Jul 2019 22:04:31 +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>
Subject: Re: [RFC PATCH 09/10] powerpc/fsl_booke/kaslr: support nokaslr
cmdline parameter
On 2019/7/29 19:38, Christophe Leroy wrote:
>
>
> Le 17/07/2019 à 10:06, 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>
>> ---
>> 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 00339c05879f..e65a5d9d2ff1 100644
>> --- a/arch/powerpc/kernel/kaslr_booke.c
>> +++ b/arch/powerpc/kernel/kaslr_booke.c
>> @@ -373,6 +373,18 @@ 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(early_command_line, "nokaslr");
>
> Why using early_command_line instead of boot_command_line ?
>
Will switch to boot_command_line.
>
>> + if ((str == early_command_line) ||
>> + (str > early_command_line && *(str - 1) == ' '))
>
> Is that stuff really needed ?
>
> Why not just:
>
> return strstr(early_command_line, "nokaslr") != NULL;
>
This code is derived from other arch such as arm64/mips. It's trying to
make sure that 'nokaslr' is a separate word but not part of other words
such as 'abcnokaslr'.
>> + return true;
>> +
>> + return false;
>> +}
>
>
>> +
>> /*
>> * To see if we need to relocate the kernel to a random offset
>> * void *dt_ptr - address of the device tree
>> @@ -388,6 +400,8 @@ 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);
>>
>
> Christophe
>
> .
>
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