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Commit f6795053 authored by Steve Capper's avatar Steve Capper Committed by Will Deacon
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mm: mmap: Allow for "high" userspace addresses 



This patch adds support for "high" userspace addresses that are
optionally supported on the system and have to be requested via a hint
mechanism ("high" addr parameter to mmap).

Architectures such as powerpc and x86 achieve this by making changes to
their architectural versions of arch_get_unmapped_* functions. However,
on arm64 we use the generic versions of these functions.

Rather than duplicate the generic arch_get_unmapped_* implementations
for arm64, this patch instead introduces two architectural helper macros
and applies them to arch_get_unmapped_*:
 arch_get_mmap_end(addr) - get mmap upper limit depending on addr hint
 arch_get_mmap_base(addr, base) - get mmap_base depending on addr hint

If these macros are not defined in architectural code then they default
to (TASK_SIZE) and (base) so should not introduce any behavioural
changes to architectures that do not define them.

Signed-off-by: default avatarSteve Capper <steve.capper@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 6e883067

mm/mmap.c

+18 −7
Original line number Diff line number Diff line
@@ -2066,6 +2066,15 @@ unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info) 
	return gap_end;

}





#ifndef arch_get_mmap_end

#define arch_get_mmap_end(addr)	(TASK_SIZE)

#endif



#ifndef arch_get_mmap_base

#define arch_get_mmap_base(addr, base) (base)

#endif



/* Get an address range which is currently unmapped.

 * For shmat() with addr=0.

 *
@@ -2085,8 +2094,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, 
	struct mm_struct *mm = current->mm;

	struct vm_area_struct *vma, *prev;

	struct vm_unmapped_area_info info;

	const unsigned long mmap_end = arch_get_mmap_end(addr);



	if (len > TASK_SIZE - mmap_min_addr)

	if (len > mmap_end - mmap_min_addr)

		return -ENOMEM;



	if (flags & MAP_FIXED)
@@ -2095,7 +2105,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, 
	if (addr) {

		addr = PAGE_ALIGN(addr);

		vma = find_vma_prev(mm, addr, &prev);

		if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&

		if (mmap_end - len >= addr && addr >= mmap_min_addr &&

		    (!vma || addr + len <= vm_start_gap(vma)) &&

		    (!prev || addr >= vm_end_gap(prev)))

			return addr;
@@ -2104,7 +2114,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, 
	info.flags = 0;

	info.length = len;

	info.low_limit = mm->mmap_base;

	info.high_limit = TASK_SIZE;

	info.high_limit = mmap_end;

	info.align_mask = 0;

	return vm_unmapped_area(&info);

}
@@ -2124,9 +2134,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, 
	struct mm_struct *mm = current->mm;

	unsigned long addr = addr0;

	struct vm_unmapped_area_info info;

	const unsigned long mmap_end = arch_get_mmap_end(addr);



	/* requested length too big for entire address space */

	if (len > TASK_SIZE - mmap_min_addr)

	if (len > mmap_end - mmap_min_addr)

		return -ENOMEM;



	if (flags & MAP_FIXED)
@@ -2136,7 +2147,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, 
	if (addr) {

		addr = PAGE_ALIGN(addr);

		vma = find_vma_prev(mm, addr, &prev);

		if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&

		if (mmap_end - len >= addr && addr >= mmap_min_addr &&

				(!vma || addr + len <= vm_start_gap(vma)) &&

				(!prev || addr >= vm_end_gap(prev)))

			return addr;
@@ -2145,7 +2156,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, 
	info.flags = VM_UNMAPPED_AREA_TOPDOWN;

	info.length = len;

	info.low_limit = max(PAGE_SIZE, mmap_min_addr);

	info.high_limit = mm->mmap_base;

	info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);

	info.align_mask = 0;

	addr = vm_unmapped_area(&info);
@@ -2159,7 +2170,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, 
		VM_BUG_ON(addr != -ENOMEM);

		info.flags = 0;

		info.low_limit = TASK_UNMAPPED_BASE;

		info.high_limit = TASK_SIZE;

		info.high_limit = mmap_end;

		addr = vm_unmapped_area(&info);

	}