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Commit 7a0eedee authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Michael Ellerman
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powerpc/mm/radix: Pick the address layout for radix config 



Hash needs special get_unmapped_area() handling because of limitations
around base page size, so we have to set HAVE_ARCH_UNMAPPED_AREA.

With radix we don't have such restrictions, so we could use the generic
code. But because we've set HAVE_ARCH_UNMAPPED_AREA (for hash), we have
to re-implement the same logic as the generic code.

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 177ba7c6

arch/powerpc/mm/mmap.c

+109 −0
Original line number Diff line number Diff line
@@ -27,6 +27,8 @@ 
#include <linux/random.h>

#include <linux/sched.h>

#include <linux/elf-randomize.h>

#include <linux/security.h>

#include <linux/mman.h>



/*

 * Top of mmap area (just below the process stack).
@@ -79,6 +81,111 @@ static inline unsigned long mmap_base(unsigned long rnd) 
	return PAGE_ALIGN(TASK_SIZE - gap - rnd);

}



#ifdef CONFIG_PPC_RADIX_MMU

/*

 * Same function as generic code used only for radix, because we don't need to overload

 * the generic one. But we will have to duplicate, because hash select

 * HAVE_ARCH_UNMAPPED_AREA

 */

static unsigned long

radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,

			     unsigned long len, unsigned long pgoff,

			     unsigned long flags)

{

	struct mm_struct *mm = current->mm;

	struct vm_area_struct *vma;

	struct vm_unmapped_area_info info;



	if (len > TASK_SIZE - mmap_min_addr)

		return -ENOMEM;



	if (flags & MAP_FIXED)

		return addr;



	if (addr) {

		addr = PAGE_ALIGN(addr);

		vma = find_vma(mm, addr);

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

		    (!vma || addr + len <= vma->vm_start))

			return addr;

	}



	info.flags = 0;

	info.length = len;

	info.low_limit = mm->mmap_base;

	info.high_limit = TASK_SIZE;

	info.align_mask = 0;

	return vm_unmapped_area(&info);

}



static unsigned long

radix__arch_get_unmapped_area_topdown(struct file *filp,

				     const unsigned long addr0,

				     const unsigned long len,

				     const unsigned long pgoff,

				     const unsigned long flags)

{

	struct vm_area_struct *vma;

	struct mm_struct *mm = current->mm;

	unsigned long addr = addr0;

	struct vm_unmapped_area_info info;



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

	if (len > TASK_SIZE - mmap_min_addr)

		return -ENOMEM;



	if (flags & MAP_FIXED)

		return addr;



	/* requesting a specific address */

	if (addr) {

		addr = PAGE_ALIGN(addr);

		vma = find_vma(mm, addr);

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

				(!vma || addr + len <= vma->vm_start))

			return addr;

	}



	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.align_mask = 0;

	addr = vm_unmapped_area(&info);



	/*

	 * A failed mmap() very likely causes application failure,

	 * so fall back to the bottom-up function here. This scenario

	 * can happen with large stack limits and large mmap()

	 * allocations.

	 */

	if (addr & ~PAGE_MASK) {

		VM_BUG_ON(addr != -ENOMEM);

		info.flags = 0;

		info.low_limit = TASK_UNMAPPED_BASE;

		info.high_limit = TASK_SIZE;

		addr = vm_unmapped_area(&info);

	}



	return addr;

}



static void radix__arch_pick_mmap_layout(struct mm_struct *mm,

					unsigned long random_factor)

{

	if (mmap_is_legacy()) {

		mm->mmap_base = TASK_UNMAPPED_BASE;

		mm->get_unmapped_area = radix__arch_get_unmapped_area;

	} else {

		mm->mmap_base = mmap_base(random_factor);

		mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown;

	}

}

#else

/* dummy */

extern void radix__arch_pick_mmap_layout(struct mm_struct *mm,

					unsigned long random_factor);

#endif

/*

 * This function, called very early during the creation of a new

 * process VM image, sets up which VM layout function to use:
@@ -90,6 +197,8 @@ void arch_pick_mmap_layout(struct mm_struct *mm) 
	if (current->flags & PF_RANDOMIZE)

		random_factor = arch_mmap_rnd();



	if (radix_enabled())

		return radix__arch_pick_mmap_layout(mm, random_factor);

	/*

	 * Fall back to the standard layout if the personality

	 * bit is set, or if the expected stack growth is unlimited: