Re: [PATCH 26/26] x86/mm: allow to have userspace mappings above 47-bits
From: Aneesh Kumar K.V
Date: Fri Mar 24 2017 - 05:14:32 EST
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@xxxxxxxxxxxxxxx> 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