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SubjectRe: [PATCH 26/26] x86/mm: allow to have userspace mappings above 47-bits
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On Friday 24 March 2017 02:34 PM, Kirill A. Shutemov wrote:
> On Mon, Mar 20, 2017 at 10:40:20AM +0530, Aneesh Kumar K.V wrote:
>> "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> writes:
>> @@ -168,6 +182,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
>>> unsigned long addr = addr0;
>>> struct vm_unmapped_area_info info;
>>>
>>> + addr = mpx_unmapped_area_check(addr, len, flags);
>>> + if (IS_ERR_VALUE(addr))
>>> + return addr;
>>> +
>>> /* requested length too big for entire address space */
>>> if (len > TASK_SIZE)
>>> return -ENOMEM;
>>> @@ -192,6 +210,14 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
>>> info.length = len;
>>> info.low_limit = PAGE_SIZE;
>>> info.high_limit = mm->mmap_base;
>>> +
>>> + /*
>>> + * If hint address is above DEFAULT_MAP_WINDOW, look for unmapped area
>>> + * in the full address space.
>>> + */
>>> + if (addr > DEFAULT_MAP_WINDOW)
>>> + info.high_limit += TASK_SIZE - DEFAULT_MAP_WINDOW;
>>> +
>>
>> Is this ok for 32 bit application ?
>
> DEFAULT_MAP_WINDOW is equal to TASK_SIZE on 32-bit, so it's nop and will
> be compile out.
>

That is not about CONFIG_X86_32 but about 32 bit application on a 64 bit
kernel. I guess we will never find addr > DEFAULT_MAP_WINDOW with
a 32 bit app ?

-aneesh

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