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Message-ID: <87efzgb0v8.fsf@concordia.ellerman.id.au>
Date: Fri, 03 Feb 2017 10:59:23 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Balbir Singh <bsingharora@...il.com>
Cc: Bhupesh Sharma <bhsharma@...hat.com>, linuxppc-dev@...ts.ozlabs.org, kernel-hardening@...ts.openwall.com, Anatolij Gustschin <agust@...x.de>, keescook@...omium.org, Daniel Cashman <dcashman@...roid.com>, Scott Wood <oss@...error.net>, Paul Mackerras <paulus@...ba.org>, dcashman@...gle.com, Alistair Popple <alistair@...ple.id.au>, bhupesh.linux@...il.com, Alexander Graf <agraf@...e.com>
Subject: Re: Re: [PATCH 1/2] powerpc: mm: support ARCH_MMAP_RND_BITS
Balbir Singh <bsingharora@...il.com> writes:
> On Thu, Feb 02, 2017 at 09:23:33PM +1100, Michael Ellerman wrote:
>> +config ARCH_MMAP_RND_BITS_MIN
>> + # On 64-bit up to 1G of address space (2^30)
>> + default 12 if 64BIT && PPC_256K_PAGES # 256K (2^18), = 30 - 18 = 12
>> + default 14 if 64BIT && PPC_64K_PAGES # 64K (2^16), = 30 - 16 = 14
>> + default 16 if 64BIT && PPC_16K_PAGES # 16K (2^14), = 30 - 14 = 16
>> + default 18 if 64BIT # 4K (2^12), = 30 - 12 = 18
>> + default ARCH_MMAP_RND_COMPAT_BITS_MIN
>> +
>> +config ARCH_MMAP_RND_BITS_MAX
>> + # On 64-bit up to 32T of address space (2^45)
>
> I thought it was 64T, TASK_SIZE_USER64 is 2^46?
The virtual address space is 64T. The comment is talking about how much
can be taking up by the randomisation factor.
cheers
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