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Subject: Re: [PATCH v4 09/10] powerpc/fsl_booke/kaslr: support nokaslr cmdline
 parameter
To:     Jason Yan <yanaijie@huawei.com>, mpe@ellerman.id.au,
        linuxppc-dev@lists.ozlabs.org, diana.craciun@nxp.com,
        benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com,
        keescook@chromium.org, kernel-hardening@lists.openwall.com
Cc:     linux-kernel@vger.kernel.org, wangkefeng.wang@huawei.com,
        yebin10@huawei.com, thunder.leizhen@huawei.com,
        jingxiangfeng@huawei.com, fanchengyang@huawei.com,
        zhaohongjiang@huawei.com
References: <20190805064335.19156-1-yanaijie@huawei.com>
 <20190805064335.19156-10-yanaijie@huawei.com>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <e7703798-c2e2-c75f-1001-46c01db88238@c-s.fr>
Date:   Tue, 6 Aug 2019 09:59:26 +0200
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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@huawei.com>
> Cc: Diana Craciun <diana.craciun@nxp.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Christophe Leroy <christophe.leroy@c-s.fr>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Kees Cook <keescook@chromium.org>
> Reviewed-by: Diana Craciun <diana.craciun@nxp.com>
> Tested-by: Diana Craciun <diana.craciun@nxp.com>

Reviewed-by: Christophe Leroy <christophe.leroy@c-s.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'

> +
> +	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);
>   
>