Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1853 insertions, 0 deletions

diff --git a/mm/nommu.c b/mm/nommu.c
new file mode 100644
index 000000000..0faf39b32
--- /dev/null
+++ b/mm/nommu.c
@@ -0,0 +1,1853 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/mm/nommu.c
+ *
+ *  Replacement code for mm functions to support CPU's that don't
+ *  have any form of memory management unit (thus no virtual memory).
+ *
+ *  See Documentation/admin-guide/mm/nommu-mmap.rst
+ *
+ *  Copyright (c) 2004-2008 David Howells <dhowells@redhat.com>
+ *  Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
+ *  Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
+ *  Copyright (c) 2002      Greg Ungerer <gerg@snapgear.com>
+ *  Copyright (c) 2007-2010 Paul Mundt <lethal@linux-sh.org>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/sched/mm.h>
+#include <linux/vmacache.h>
+#include <linux/mman.h>
+#include <linux/swap.h>
+#include <linux/file.h>
+#include <linux/highmem.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/compiler.h>
+#include <linux/mount.h>
+#include <linux/personality.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <linux/audit.h>
+#include <linux/printk.h>
+
+#include <linux/uaccess.h>
+#include <asm/tlb.h>
+#include <asm/tlbflush.h>
+#include <asm/mmu_context.h>
+#include "internal.h"
+
+void *high_memory;
+EXPORT_SYMBOL(high_memory);
+struct page *mem_map;
+unsigned long max_mapnr;
+EXPORT_SYMBOL(max_mapnr);
+unsigned long highest_memmap_pfn;
+int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
+int heap_stack_gap = 0;
+
+atomic_long_t mmap_pages_allocated;
+
+EXPORT_SYMBOL(mem_map);
+
+/* list of mapped, potentially shareable regions */
+static struct kmem_cache *vm_region_jar;
+struct rb_root nommu_region_tree = RB_ROOT;
+DECLARE_RWSEM(nommu_region_sem);
+
+const struct vm_operations_struct generic_file_vm_ops = {
+};
+
+/*
+ * Return the total memory allocated for this pointer, not
+ * just what the caller asked for.
+ *
+ * Doesn't have to be accurate, i.e. may have races.
+ */
+unsigned int kobjsize(const void *objp)
+{
+	struct page *page;
+
+	/*
+	 * If the object we have should not have ksize performed on it,
+	 * return size of 0
+	 */
+	if (!objp || !virt_addr_valid(objp))
+		return 0;
+
+	page = virt_to_head_page(objp);
+
+	/*
+	 * If the allocator sets PageSlab, we know the pointer came from
+	 * kmalloc().
+	 */
+	if (PageSlab(page))
+		return ksize(objp);
+
+	/*
+	 * If it's not a compound page, see if we have a matching VMA
+	 * region. This test is intentionally done in reverse order,
+	 * so if there's no VMA, we still fall through and hand back
+	 * PAGE_SIZE for 0-order pages.
+	 */
+	if (!PageCompound(page)) {
+		struct vm_area_struct *vma;
+
+		vma = find_vma(current->mm, (unsigned long)objp);
+		if (vma)
+			return vma->vm_end - vma->vm_start;
+	}
+
+	/*
+	 * The ksize() function is only guaranteed to work for pointers
+	 * returned by kmalloc(). So handle arbitrary pointers here.
+	 */
+	return page_size(page);
+}
+
+/**
+ * follow_pfn - look up PFN at a user virtual address
+ * @vma: memory mapping
+ * @address: user virtual address
+ * @pfn: location to store found PFN
+ *
+ * Only IO mappings and raw PFN mappings are allowed.
+ *
+ * Returns zero and the pfn at @pfn on success, -ve otherwise.
+ */
+int follow_pfn(struct vm_area_struct *vma, unsigned long address,
+	unsigned long *pfn)
+{
+	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
+		return -EINVAL;
+
+	*pfn = address >> PAGE_SHIFT;
+	return 0;
+}
+EXPORT_SYMBOL(follow_pfn);
+
+LIST_HEAD(vmap_area_list);
+
+void vfree(const void *addr)
+{
+	kfree(addr);
+}
+EXPORT_SYMBOL(vfree);
+
+void *__vmalloc(unsigned long size, gfp_t gfp_mask)
+{
+	/*
+	 *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
+	 * returns only a logical address.
+	 */
+	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
+}
+EXPORT_SYMBOL(__vmalloc);
+
+void *__vmalloc_node_range(unsigned long size, unsigned long align,
+		unsigned long start, unsigned long end, gfp_t gfp_mask,
+		pgprot_t prot, unsigned long vm_flags, int node,
+		const void *caller)
+{
+	return __vmalloc(size, gfp_mask);
+}
+
+void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
+		int node, const void *caller)
+{
+	return __vmalloc(size, gfp_mask);
+}
+
+static void *__vmalloc_user_flags(unsigned long size, gfp_t flags)
+{
+	void *ret;
+
+	ret = __vmalloc(size, flags);
+	if (ret) {
+		struct vm_area_struct *vma;
+
+		mmap_write_lock(current->mm);
+		vma = find_vma(current->mm, (unsigned long)ret);
+		if (vma)
+			vma->vm_flags |= VM_USERMAP;
+		mmap_write_unlock(current->mm);
+	}
+
+	return ret;
+}
+
+void *vmalloc_user(unsigned long size)
+{
+	return __vmalloc_user_flags(size, GFP_KERNEL | __GFP_ZERO);
+}
+EXPORT_SYMBOL(vmalloc_user);
+
+struct page *vmalloc_to_page(const void *addr)
+{
+	return virt_to_page(addr);
+}
+EXPORT_SYMBOL(vmalloc_to_page);
+
+unsigned long vmalloc_to_pfn(const void *addr)
+{
+	return page_to_pfn(virt_to_page(addr));
+}
+EXPORT_SYMBOL(vmalloc_to_pfn);
+
+long vread(char *buf, char *addr, unsigned long count)
+{
+	/* Don't allow overflow */
+	if ((unsigned long) buf + count < count)
+		count = -(unsigned long) buf;
+
+	memcpy(buf, addr, count);
+	return count;
+}
+
+long vwrite(char *buf, char *addr, unsigned long count)
+{
+	/* Don't allow overflow */
+	if ((unsigned long) addr + count < count)
+		count = -(unsigned long) addr;
+
+	memcpy(addr, buf, count);
+	return count;
+}
+
+/*
+ *	vmalloc  -  allocate virtually contiguous memory
+ *
+ *	@size:		allocation size
+ *
+ *	Allocate enough pages to cover @size from the page level
+ *	allocator and map them into contiguous kernel virtual space.
+ *
+ *	For tight control over page level allocator and protection flags
+ *	use __vmalloc() instead.
+ */
+void *vmalloc(unsigned long size)
+{
+       return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM);
+}
+EXPORT_SYMBOL(vmalloc);
+
+/*
+ *	vzalloc - allocate virtually contiguous memory with zero fill
+ *
+ *	@size:		allocation size
+ *
+ *	Allocate enough pages to cover @size from the page level
+ *	allocator and map them into contiguous kernel virtual space.
+ *	The memory allocated is set to zero.
+ *
+ *	For tight control over page level allocator and protection flags
+ *	use __vmalloc() instead.
+ */
+void *vzalloc(unsigned long size)
+{
+	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
+}
+EXPORT_SYMBOL(vzalloc);
+
+/**
+ * vmalloc_node - allocate memory on a specific node
+ * @size:	allocation size
+ * @node:	numa node
+ *
+ * Allocate enough pages to cover @size from the page level
+ * allocator and map them into contiguous kernel virtual space.
+ *
+ * For tight control over page level allocator and protection flags
+ * use __vmalloc() instead.
+ */
+void *vmalloc_node(unsigned long size, int node)
+{
+	return vmalloc(size);
+}
+EXPORT_SYMBOL(vmalloc_node);
+
+/**
+ * vzalloc_node - allocate memory on a specific node with zero fill
+ * @size:	allocation size
+ * @node:	numa node
+ *
+ * Allocate enough pages to cover @size from the page level
+ * allocator and map them into contiguous kernel virtual space.
+ * The memory allocated is set to zero.
+ *
+ * For tight control over page level allocator and protection flags
+ * use __vmalloc() instead.
+ */
+void *vzalloc_node(unsigned long size, int node)
+{
+	return vzalloc(size);
+}
+EXPORT_SYMBOL(vzalloc_node);
+
+/**
+ * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
+ *	@size:		allocation size
+ *
+ *	Allocate enough 32bit PA addressable pages to cover @size from the
+ *	page level allocator and map them into contiguous kernel virtual space.
+ */
+void *vmalloc_32(unsigned long size)
+{
+	return __vmalloc(size, GFP_KERNEL);
+}
+EXPORT_SYMBOL(vmalloc_32);
+
+/**
+ * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
+ *	@size:		allocation size
+ *
+ * The resulting memory area is 32bit addressable and zeroed so it can be
+ * mapped to userspace without leaking data.
+ *
+ * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
+ * remap_vmalloc_range() are permissible.
+ */
+void *vmalloc_32_user(unsigned long size)
+{
+	/*
+	 * We'll have to sort out the ZONE_DMA bits for 64-bit,
+	 * but for now this can simply use vmalloc_user() directly.
+	 */
+	return vmalloc_user(size);
+}
+EXPORT_SYMBOL(vmalloc_32_user);
+
+void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
+{
+	BUG();
+	return NULL;
+}
+EXPORT_SYMBOL(vmap);
+
+void vunmap(const void *addr)
+{
+	BUG();
+}
+EXPORT_SYMBOL(vunmap);
+
+void *vm_map_ram(struct page **pages, unsigned int count, int node)
+{
+	BUG();
+	return NULL;
+}
+EXPORT_SYMBOL(vm_map_ram);
+
+void vm_unmap_ram(const void *mem, unsigned int count)
+{
+	BUG();
+}
+EXPORT_SYMBOL(vm_unmap_ram);
+
+void vm_unmap_aliases(void)
+{
+}
+EXPORT_SYMBOL_GPL(vm_unmap_aliases);
+
+void free_vm_area(struct vm_struct *area)
+{
+	BUG();
+}
+EXPORT_SYMBOL_GPL(free_vm_area);
+
+int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
+		   struct page *page)
+{
+	return -EINVAL;
+}
+EXPORT_SYMBOL(vm_insert_page);
+
+int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
+			unsigned long num)
+{
+	return -EINVAL;
+}
+EXPORT_SYMBOL(vm_map_pages);
+
+int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
+				unsigned long num)
+{
+	return -EINVAL;
+}
+EXPORT_SYMBOL(vm_map_pages_zero);
+
+/*
+ *  sys_brk() for the most part doesn't need the global kernel
+ *  lock, except when an application is doing something nasty
+ *  like trying to un-brk an area that has already been mapped
+ *  to a regular file.  in this case, the unmapping will need
+ *  to invoke file system routines that need the global lock.
+ */
+SYSCALL_DEFINE1(brk, unsigned long, brk)
+{
+	struct mm_struct *mm = current->mm;
+
+	if (brk < mm->start_brk || brk > mm->context.end_brk)
+		return mm->brk;
+
+	if (mm->brk == brk)
+		return mm->brk;
+
+	/*
+	 * Always allow shrinking brk
+	 */
+	if (brk <= mm->brk) {
+		mm->brk = brk;
+		return brk;
+	}
+
+	/*
+	 * Ok, looks good - let it rip.
+	 */
+	flush_icache_user_range(mm->brk, brk);
+	return mm->brk = brk;
+}
+
+/*
+ * initialise the percpu counter for VM and region record slabs
+ */
+void __init mmap_init(void)
+{
+	int ret;
+
+	ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
+	VM_BUG_ON(ret);
+	vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC|SLAB_ACCOUNT);
+}
+
+/*
+ * validate the region tree
+ * - the caller must hold the region lock
+ */
+#ifdef CONFIG_DEBUG_NOMMU_REGIONS
+static noinline void validate_nommu_regions(void)
+{
+	struct vm_region *region, *last;
+	struct rb_node *p, *lastp;
+
+	lastp = rb_first(&nommu_region_tree);
+	if (!lastp)
+		return;
+
+	last = rb_entry(lastp, struct vm_region, vm_rb);
+	BUG_ON(last->vm_end <= last->vm_start);
+	BUG_ON(last->vm_top < last->vm_end);
+
+	while ((p = rb_next(lastp))) {
+		region = rb_entry(p, struct vm_region, vm_rb);
+		last = rb_entry(lastp, struct vm_region, vm_rb);
+
+		BUG_ON(region->vm_end <= region->vm_start);
+		BUG_ON(region->vm_top < region->vm_end);
+		BUG_ON(region->vm_start < last->vm_top);
+
+		lastp = p;
+	}
+}
+#else
+static void validate_nommu_regions(void)
+{
+}
+#endif
+
+/*
+ * add a region into the global tree
+ */
+static void add_nommu_region(struct vm_region *region)
+{
+	struct vm_region *pregion;
+	struct rb_node **p, *parent;
+
+	validate_nommu_regions();
+
+	parent = NULL;
+	p = &nommu_region_tree.rb_node;
+	while (*p) {
+		parent = *p;
+		pregion = rb_entry(parent, struct vm_region, vm_rb);
+		if (region->vm_start < pregion->vm_start)
+			p = &(*p)->rb_left;
+		else if (region->vm_start > pregion->vm_start)
+			p = &(*p)->rb_right;
+		else if (pregion == region)
+			return;
+		else
+			BUG();
+	}
+
+	rb_link_node(&region->vm_rb, parent, p);
+	rb_insert_color(&region->vm_rb, &nommu_region_tree);
+
+	validate_nommu_regions();
+}
+
+/*
+ * delete a region from the global tree
+ */
+static void delete_nommu_region(struct vm_region *region)
+{
+	BUG_ON(!nommu_region_tree.rb_node);
+
+	validate_nommu_regions();
+	rb_erase(&region->vm_rb, &nommu_region_tree);
+	validate_nommu_regions();
+}
+
+/*
+ * free a contiguous series of pages
+ */
+static void free_page_series(unsigned long from, unsigned long to)
+{
+	for (; from < to; from += PAGE_SIZE) {
+		struct page *page = virt_to_page(from);
+
+		atomic_long_dec(&mmap_pages_allocated);
+		put_page(page);
+	}
+}
+
+/*
+ * release a reference to a region
+ * - the caller must hold the region semaphore for writing, which this releases
+ * - the region may not have been added to the tree yet, in which case vm_top
+ *   will equal vm_start
+ */
+static void __put_nommu_region(struct vm_region *region)
+	__releases(nommu_region_sem)
+{
+	BUG_ON(!nommu_region_tree.rb_node);
+
+	if (--region->vm_usage == 0) {
+		if (region->vm_top > region->vm_start)
+			delete_nommu_region(region);
+		up_write(&nommu_region_sem);
+
+		if (region->vm_file)
+			fput(region->vm_file);
+
+		/* IO memory and memory shared directly out of the pagecache
+		 * from ramfs/tmpfs mustn't be released here */
+		if (region->vm_flags & VM_MAPPED_COPY)
+			free_page_series(region->vm_start, region->vm_top);
+		kmem_cache_free(vm_region_jar, region);
+	} else {
+		up_write(&nommu_region_sem);
+	}
+}
+
+/*
+ * release a reference to a region
+ */
+static void put_nommu_region(struct vm_region *region)
+{
+	down_write(&nommu_region_sem);
+	__put_nommu_region(region);
+}
+
+/*
+ * add a VMA into a process's mm_struct in the appropriate place in the list
+ * and tree and add to the address space's page tree also if not an anonymous
+ * page
+ * - should be called with mm->mmap_lock held writelocked
+ */
+static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+	struct vm_area_struct *pvma, *prev;
+	struct address_space *mapping;
+	struct rb_node **p, *parent, *rb_prev;
+
+	BUG_ON(!vma->vm_region);
+
+	mm->map_count++;
+	vma->vm_mm = mm;
+
+	/* add the VMA to the mapping */
+	if (vma->vm_file) {
+		mapping = vma->vm_file->f_mapping;
+
+		i_mmap_lock_write(mapping);
+		flush_dcache_mmap_lock(mapping);
+		vma_interval_tree_insert(vma, &mapping->i_mmap);
+		flush_dcache_mmap_unlock(mapping);
+		i_mmap_unlock_write(mapping);
+	}
+
+	/* add the VMA to the tree */
+	parent = rb_prev = NULL;
+	p = &mm->mm_rb.rb_node;
+	while (*p) {
+		parent = *p;
+		pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
+
+		/* sort by: start addr, end addr, VMA struct addr in that order
+		 * (the latter is necessary as we may get identical VMAs) */
+		if (vma->vm_start < pvma->vm_start)
+			p = &(*p)->rb_left;
+		else if (vma->vm_start > pvma->vm_start) {
+			rb_prev = parent;
+			p = &(*p)->rb_right;
+		} else if (vma->vm_end < pvma->vm_end)
+			p = &(*p)->rb_left;
+		else if (vma->vm_end > pvma->vm_end) {
+			rb_prev = parent;
+			p = &(*p)->rb_right;
+		} else if (vma < pvma)
+			p = &(*p)->rb_left;
+		else if (vma > pvma) {
+			rb_prev = parent;
+			p = &(*p)->rb_right;
+		} else
+			BUG();
+	}
+
+	rb_link_node(&vma->vm_rb, parent, p);
+	rb_insert_color(&vma->vm_rb, &mm->mm_rb);
+
+	/* add VMA to the VMA list also */
+	prev = NULL;
+	if (rb_prev)
+		prev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
+
+	__vma_link_list(mm, vma, prev);
+}
+
+/*
+ * delete a VMA from its owning mm_struct and address space
+ */
+static void delete_vma_from_mm(struct vm_area_struct *vma)
+{
+	int i;
+	struct address_space *mapping;
+	struct mm_struct *mm = vma->vm_mm;
+	struct task_struct *curr = current;
+
+	mm->map_count--;
+	for (i = 0; i < VMACACHE_SIZE; i++) {
+		/* if the vma is cached, invalidate the entire cache */
+		if (curr->vmacache.vmas[i] == vma) {
+			vmacache_invalidate(mm);
+			break;
+		}
+	}
+
+	/* remove the VMA from the mapping */
+	if (vma->vm_file) {
+		mapping = vma->vm_file->f_mapping;
+
+		i_mmap_lock_write(mapping);
+		flush_dcache_mmap_lock(mapping);
+		vma_interval_tree_remove(vma, &mapping->i_mmap);
+		flush_dcache_mmap_unlock(mapping);
+		i_mmap_unlock_write(mapping);
+	}
+
+	/* remove from the MM's tree and list */
+	rb_erase(&vma->vm_rb, &mm->mm_rb);
+
+	__vma_unlink_list(mm, vma);
+}
+
+/*
+ * destroy a VMA record
+ */
+static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+	if (vma->vm_ops && vma->vm_ops->close)
+		vma->vm_ops->close(vma);
+	if (vma->vm_file)
+		fput(vma->vm_file);
+	put_nommu_region(vma->vm_region);
+	vm_area_free(vma);
+}
+
+/*
+ * look up the first VMA in which addr resides, NULL if none
+ * - should be called with mm->mmap_lock at least held readlocked
+ */
+struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
+{
+	struct vm_area_struct *vma;
+
+	/* check the cache first */
+	vma = vmacache_find(mm, addr);
+	if (likely(vma))
+		return vma;
+
+	/* trawl the list (there may be multiple mappings in which addr
+	 * resides) */
+	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		if (vma->vm_start > addr)
+			return NULL;
+		if (vma->vm_end > addr) {
+			vmacache_update(addr, vma);
+			return vma;
+		}
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL(find_vma);
+
+/*
+ * find a VMA
+ * - we don't extend stack VMAs under NOMMU conditions
+ */
+struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
+{
+	return find_vma(mm, addr);
+}
+
+/*
+ * expand a stack to a given address
+ * - not supported under NOMMU conditions
+ */
+int expand_stack(struct vm_area_struct *vma, unsigned long address)
+{
+	return -ENOMEM;
+}
+
+/*
+ * look up the first VMA exactly that exactly matches addr
+ * - should be called with mm->mmap_lock at least held readlocked
+ */
+static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
+					     unsigned long addr,
+					     unsigned long len)
+{
+	struct vm_area_struct *vma;
+	unsigned long end = addr + len;
+
+	/* check the cache first */
+	vma = vmacache_find_exact(mm, addr, end);
+	if (vma)
+		return vma;
+
+	/* trawl the list (there may be multiple mappings in which addr
+	 * resides) */
+	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		if (vma->vm_start < addr)
+			continue;
+		if (vma->vm_start > addr)
+			return NULL;
+		if (vma->vm_end == end) {
+			vmacache_update(addr, vma);
+			return vma;
+		}
+	}
+
+	return NULL;
+}
+
+/*
+ * determine whether a mapping should be permitted and, if so, what sort of
+ * mapping we're capable of supporting
+ */
+static int validate_mmap_request(struct file *file,
+				 unsigned long addr,
+				 unsigned long len,
+				 unsigned long prot,
+				 unsigned long flags,
+				 unsigned long pgoff,
+				 unsigned long *_capabilities)
+{
+	unsigned long capabilities, rlen;
+	int ret;
+
+	/* do the simple checks first */
+	if (flags & MAP_FIXED)
+		return -EINVAL;
+
+	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
+	    (flags & MAP_TYPE) != MAP_SHARED)
+		return -EINVAL;
+
+	if (!len)
+		return -EINVAL;
+
+	/* Careful about overflows.. */
+	rlen = PAGE_ALIGN(len);
+	if (!rlen || rlen > TASK_SIZE)
+		return -ENOMEM;
+
+	/* offset overflow? */
+	if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
+		return -EOVERFLOW;
+
+	if (file) {
+		/* files must support mmap */
+		if (!file->f_op->mmap)
+			return -ENODEV;
+
+		/* work out if what we've got could possibly be shared
+		 * - we support chardevs that provide their own "memory"
+		 * - we support files/blockdevs that are memory backed
+		 */
+		if (file->f_op->mmap_capabilities) {
+			capabilities = file->f_op->mmap_capabilities(file);
+		} else {
+			/* no explicit capabilities set, so assume some
+			 * defaults */
+			switch (file_inode(file)->i_mode & S_IFMT) {
+			case S_IFREG:
+			case S_IFBLK:
+				capabilities = NOMMU_MAP_COPY;
+				break;
+
+			case S_IFCHR:
+				capabilities =
+					NOMMU_MAP_DIRECT |
+					NOMMU_MAP_READ |
+					NOMMU_MAP_WRITE;
+				break;
+
+			default:
+				return -EINVAL;
+			}
+		}
+
+		/* eliminate any capabilities that we can't support on this
+		 * device */
+		if (!file->f_op->get_unmapped_area)
+			capabilities &= ~NOMMU_MAP_DIRECT;
+		if (!(file->f_mode & FMODE_CAN_READ))
+			capabilities &= ~NOMMU_MAP_COPY;
+
+		/* The file shall have been opened with read permission. */
+		if (!(file->f_mode & FMODE_READ))
+			return -EACCES;
+
+		if (flags & MAP_SHARED) {
+			/* do checks for writing, appending and locking */
+			if ((prot & PROT_WRITE) &&
+			    !(file->f_mode & FMODE_WRITE))
+				return -EACCES;
+
+			if (IS_APPEND(file_inode(file)) &&
+			    (file->f_mode & FMODE_WRITE))
+				return -EACCES;
+
+			if (locks_verify_locked(file))
+				return -EAGAIN;
+
+			if (!(capabilities & NOMMU_MAP_DIRECT))
+				return -ENODEV;
+
+			/* we mustn't privatise shared mappings */
+			capabilities &= ~NOMMU_MAP_COPY;
+		} else {
+			/* we're going to read the file into private memory we
+			 * allocate */
+			if (!(capabilities & NOMMU_MAP_COPY))
+				return -ENODEV;
+
+			/* we don't permit a private writable mapping to be
+			 * shared with the backing device */
+			if (prot & PROT_WRITE)
+				capabilities &= ~NOMMU_MAP_DIRECT;
+		}
+
+		if (capabilities & NOMMU_MAP_DIRECT) {
+			if (((prot & PROT_READ)  && !(capabilities & NOMMU_MAP_READ))  ||
+			    ((prot & PROT_WRITE) && !(capabilities & NOMMU_MAP_WRITE)) ||
+			    ((prot & PROT_EXEC)  && !(capabilities & NOMMU_MAP_EXEC))
+			    ) {
+				capabilities &= ~NOMMU_MAP_DIRECT;
+				if (flags & MAP_SHARED) {
+					pr_warn("MAP_SHARED not completely supported on !MMU\n");
+					return -EINVAL;
+				}
+			}
+		}
+
+		/* handle executable mappings and implied executable
+		 * mappings */
+		if (path_noexec(&file->f_path)) {
+			if (prot & PROT_EXEC)
+				return -EPERM;
+		} else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
+			/* handle implication of PROT_EXEC by PROT_READ */
+			if (current->personality & READ_IMPLIES_EXEC) {
+				if (capabilities & NOMMU_MAP_EXEC)
+					prot |= PROT_EXEC;
+			}
+		} else if ((prot & PROT_READ) &&
+			 (prot & PROT_EXEC) &&
+			 !(capabilities & NOMMU_MAP_EXEC)
+			 ) {
+			/* backing file is not executable, try to copy */
+			capabilities &= ~NOMMU_MAP_DIRECT;
+		}
+	} else {
+		/* anonymous mappings are always memory backed and can be
+		 * privately mapped
+		 */
+		capabilities = NOMMU_MAP_COPY;
+
+		/* handle PROT_EXEC implication by PROT_READ */
+		if ((prot & PROT_READ) &&
+		    (current->personality & READ_IMPLIES_EXEC))
+			prot |= PROT_EXEC;
+	}
+
+	/* allow the security API to have its say */
+	ret = security_mmap_addr(addr);
+	if (ret < 0)
+		return ret;
+
+	/* looks okay */
+	*_capabilities = capabilities;
+	return 0;
+}
+
+/*
+ * we've determined that we can make the mapping, now translate what we
+ * now know into VMA flags
+ */
+static unsigned long determine_vm_flags(struct file *file,
+					unsigned long prot,
+					unsigned long flags,
+					unsigned long capabilities)
+{
+	unsigned long vm_flags;
+
+	vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(flags);
+	/* vm_flags |= mm->def_flags; */
+
+	if (!(capabilities & NOMMU_MAP_DIRECT)) {
+		/* attempt to share read-only copies of mapped file chunks */
+		vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
+		if (file && !(prot & PROT_WRITE))
+			vm_flags |= VM_MAYSHARE;
+	} else {
+		/* overlay a shareable mapping on the backing device or inode
+		 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
+		 * romfs/cramfs */
+		vm_flags |= VM_MAYSHARE | (capabilities & NOMMU_VMFLAGS);
+		if (flags & MAP_SHARED)
+			vm_flags |= VM_SHARED;
+	}
+
+	/* refuse to let anyone share private mappings with this process if
+	 * it's being traced - otherwise breakpoints set in it may interfere
+	 * with another untraced process
+	 */
+	if ((flags & MAP_PRIVATE) && current->ptrace)
+		vm_flags &= ~VM_MAYSHARE;
+
+	return vm_flags;
+}
+
+/*
+ * set up a shared mapping on a file (the driver or filesystem provides and
+ * pins the storage)
+ */
+static int do_mmap_shared_file(struct vm_area_struct *vma)
+{
+	int ret;
+
+	ret = call_mmap(vma->vm_file, vma);
+	if (ret == 0) {
+		vma->vm_region->vm_top = vma->vm_region->vm_end;
+		return 0;
+	}
+	if (ret != -ENOSYS)
+		return ret;
+
+	/* getting -ENOSYS indicates that direct mmap isn't possible (as
+	 * opposed to tried but failed) so we can only give a suitable error as
+	 * it's not possible to make a private copy if MAP_SHARED was given */
+	return -ENODEV;
+}
+
+/*
+ * set up a private mapping or an anonymous shared mapping
+ */
+static int do_mmap_private(struct vm_area_struct *vma,
+			   struct vm_region *region,
+			   unsigned long len,
+			   unsigned long capabilities)
+{
+	unsigned long total, point;
+	void *base;
+	int ret, order;
+
+	/* invoke the file's mapping function so that it can keep track of
+	 * shared mappings on devices or memory
+	 * - VM_MAYSHARE will be set if it may attempt to share
+	 */
+	if (capabilities & NOMMU_MAP_DIRECT) {
+		ret = call_mmap(vma->vm_file, vma);
+		if (ret == 0) {
+			/* shouldn't return success if we're not sharing */
+			BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
+			vma->vm_region->vm_top = vma->vm_region->vm_end;
+			return 0;
+		}
+		if (ret != -ENOSYS)
+			return ret;
+
+		/* getting an ENOSYS error indicates that direct mmap isn't
+		 * possible (as opposed to tried but failed) so we'll try to
+		 * make a private copy of the data and map that instead */
+	}
+
+
+	/* allocate some memory to hold the mapping
+	 * - note that this may not return a page-aligned address if the object
+	 *   we're allocating is smaller than a page
+	 */
+	order = get_order(len);
+	total = 1 << order;
+	point = len >> PAGE_SHIFT;
+
+	/* we don't want to allocate a power-of-2 sized page set */
+	if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages)
+		total = point;
+
+	base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
+	if (!base)
+		goto enomem;
+
+	atomic_long_add(total, &mmap_pages_allocated);
+
+	region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
+	region->vm_start = (unsigned long) base;
+	region->vm_end   = region->vm_start + len;
+	region->vm_top   = region->vm_start + (total << PAGE_SHIFT);
+
+	vma->vm_start = region->vm_start;
+	vma->vm_end   = region->vm_start + len;
+
+	if (vma->vm_file) {
+		/* read the contents of a file into the copy */
+		loff_t fpos;
+
+		fpos = vma->vm_pgoff;
+		fpos <<= PAGE_SHIFT;
+
+		ret = kernel_read(vma->vm_file, base, len, &fpos);
+		if (ret < 0)
+			goto error_free;
+
+		/* clear the last little bit */
+		if (ret < len)
+			memset(base + ret, 0, len - ret);
+
+	} else {
+		vma_set_anonymous(vma);
+	}
+
+	return 0;
+
+error_free:
+	free_page_series(region->vm_start, region->vm_top);
+	region->vm_start = vma->vm_start = 0;
+	region->vm_end   = vma->vm_end = 0;
+	region->vm_top   = 0;
+	return ret;
+
+enomem:
+	pr_err("Allocation of length %lu from process %d (%s) failed\n",
+	       len, current->pid, current->comm);
+	show_free_areas(0, NULL);
+	return -ENOMEM;
+}
+
+/*
+ * handle mapping creation for uClinux
+ */
+unsigned long do_mmap(struct file *file,
+			unsigned long addr,
+			unsigned long len,
+			unsigned long prot,
+			unsigned long flags,
+			unsigned long pgoff,
+			unsigned long *populate,
+			struct list_head *uf)
+{
+	struct vm_area_struct *vma;
+	struct vm_region *region;
+	struct rb_node *rb;
+	vm_flags_t vm_flags;
+	unsigned long capabilities, result;
+	int ret;
+
+	*populate = 0;
+
+	/* decide whether we should attempt the mapping, and if so what sort of
+	 * mapping */
+	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
+				    &capabilities);
+	if (ret < 0)
+		return ret;
+
+	/* we ignore the address hint */
+	addr = 0;
+	len = PAGE_ALIGN(len);
+
+	/* we've determined that we can make the mapping, now translate what we
+	 * now know into VMA flags */
+	vm_flags = determine_vm_flags(file, prot, flags, capabilities);
+
+	/* we're going to need to record the mapping */
+	region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
+	if (!region)
+		goto error_getting_region;
+
+	vma = vm_area_alloc(current->mm);
+	if (!vma)
+		goto error_getting_vma;
+
+	region->vm_usage = 1;
+	region->vm_flags = vm_flags;
+	region->vm_pgoff = pgoff;
+
+	vma->vm_flags = vm_flags;
+	vma->vm_pgoff = pgoff;
+
+	if (file) {
+		region->vm_file = get_file(file);
+		vma->vm_file = get_file(file);
+	}
+
+	down_write(&nommu_region_sem);
+
+	/* if we want to share, we need to check for regions created by other
+	 * mmap() calls that overlap with our proposed mapping
+	 * - we can only share with a superset match on most regular files
+	 * - shared mappings on character devices and memory backed files are
+	 *   permitted to overlap inexactly as far as we are concerned for in
+	 *   these cases, sharing is handled in the driver or filesystem rather
+	 *   than here
+	 */
+	if (vm_flags & VM_MAYSHARE) {
+		struct vm_region *pregion;
+		unsigned long pglen, rpglen, pgend, rpgend, start;
+
+		pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		pgend = pgoff + pglen;
+
+		for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
+			pregion = rb_entry(rb, struct vm_region, vm_rb);
+
+			if (!(pregion->vm_flags & VM_MAYSHARE))
+				continue;
+
+			/* search for overlapping mappings on the same file */
+			if (file_inode(pregion->vm_file) !=
+			    file_inode(file))
+				continue;
+
+			if (pregion->vm_pgoff >= pgend)
+				continue;
+
+			rpglen = pregion->vm_end - pregion->vm_start;
+			rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
+			rpgend = pregion->vm_pgoff + rpglen;
+			if (pgoff >= rpgend)
+				continue;
+
+			/* handle inexactly overlapping matches between
+			 * mappings */
+			if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
+			    !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
+				/* new mapping is not a subset of the region */
+				if (!(capabilities & NOMMU_MAP_DIRECT))
+					goto sharing_violation;
+				continue;
+			}
+
+			/* we've found a region we can share */
+			pregion->vm_usage++;
+			vma->vm_region = pregion;
+			start = pregion->vm_start;
+			start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
+			vma->vm_start = start;
+			vma->vm_end = start + len;
+
+			if (pregion->vm_flags & VM_MAPPED_COPY)
+				vma->vm_flags |= VM_MAPPED_COPY;
+			else {
+				ret = do_mmap_shared_file(vma);
+				if (ret < 0) {
+					vma->vm_region = NULL;
+					vma->vm_start = 0;
+					vma->vm_end = 0;
+					pregion->vm_usage--;
+					pregion = NULL;
+					goto error_just_free;
+				}
+			}
+			fput(region->vm_file);
+			kmem_cache_free(vm_region_jar, region);
+			region = pregion;
+			result = start;
+			goto share;
+		}
+
+		/* obtain the address at which to make a shared mapping
+		 * - this is the hook for quasi-memory character devices to
+		 *   tell us the location of a shared mapping
+		 */
+		if (capabilities & NOMMU_MAP_DIRECT) {
+			addr = file->f_op->get_unmapped_area(file, addr, len,
+							     pgoff, flags);
+			if (IS_ERR_VALUE(addr)) {
+				ret = addr;
+				if (ret != -ENOSYS)
+					goto error_just_free;
+
+				/* the driver refused to tell us where to site
+				 * the mapping so we'll have to attempt to copy
+				 * it */
+				ret = -ENODEV;
+				if (!(capabilities & NOMMU_MAP_COPY))
+					goto error_just_free;
+
+				capabilities &= ~NOMMU_MAP_DIRECT;
+			} else {
+				vma->vm_start = region->vm_start = addr;
+				vma->vm_end = region->vm_end = addr + len;
+			}
+		}
+	}
+
+	vma->vm_region = region;
+
+	/* set up the mapping
+	 * - the region is filled in if NOMMU_MAP_DIRECT is still set
+	 */
+	if (file && vma->vm_flags & VM_SHARED)
+		ret = do_mmap_shared_file(vma);
+	else
+		ret = do_mmap_private(vma, region, len, capabilities);
+	if (ret < 0)
+		goto error_just_free;
+	add_nommu_region(region);
+
+	/* clear anonymous mappings that don't ask for uninitialized data */
+	if (!vma->vm_file &&
+	    (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
+	     !(flags & MAP_UNINITIALIZED)))
+		memset((void *)region->vm_start, 0,
+		       region->vm_end - region->vm_start);
+
+	/* okay... we have a mapping; now we have to register it */
+	result = vma->vm_start;
+
+	current->mm->total_vm += len >> PAGE_SHIFT;
+
+share:
+	add_vma_to_mm(current->mm, vma);
+
+	/* we flush the region from the icache only when the first executable
+	 * mapping of it is made  */
+	if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
+		flush_icache_user_range(region->vm_start, region->vm_end);
+		region->vm_icache_flushed = true;
+	}
+
+	up_write(&nommu_region_sem);
+
+	return result;
+
+error_just_free:
+	up_write(&nommu_region_sem);
+error:
+	if (region->vm_file)
+		fput(region->vm_file);
+	kmem_cache_free(vm_region_jar, region);
+	if (vma->vm_file)
+		fput(vma->vm_file);
+	vm_area_free(vma);
+	return ret;
+
+sharing_violation:
+	up_write(&nommu_region_sem);
+	pr_warn("Attempt to share mismatched mappings\n");
+	ret = -EINVAL;
+	goto error;
+
+error_getting_vma:
+	kmem_cache_free(vm_region_jar, region);
+	pr_warn("Allocation of vma for %lu byte allocation from process %d failed\n",
+			len, current->pid);
+	show_free_areas(0, NULL);
+	return -ENOMEM;
+
+error_getting_region:
+	pr_warn("Allocation of vm region for %lu byte allocation from process %d failed\n",
+			len, current->pid);
+	show_free_areas(0, NULL);
+	return -ENOMEM;
+}
+
+unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
+			      unsigned long prot, unsigned long flags,
+			      unsigned long fd, unsigned long pgoff)
+{
+	struct file *file = NULL;
+	unsigned long retval = -EBADF;
+
+	audit_mmap_fd(fd, flags);
+	if (!(flags & MAP_ANONYMOUS)) {
+		file = fget(fd);
+		if (!file)
+			goto out;
+	}
+
+	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
+
+	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
+
+	if (file)
+		fput(file);
+out:
+	return retval;
+}
+
+SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
+		unsigned long, prot, unsigned long, flags,
+		unsigned long, fd, unsigned long, pgoff)
+{
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
+}
+
+#ifdef __ARCH_WANT_SYS_OLD_MMAP
+struct mmap_arg_struct {
+	unsigned long addr;
+	unsigned long len;
+	unsigned long prot;
+	unsigned long flags;
+	unsigned long fd;
+	unsigned long offset;
+};
+
+SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
+{
+	struct mmap_arg_struct a;
+
+	if (copy_from_user(&a, arg, sizeof(a)))
+		return -EFAULT;
+	if (offset_in_page(a.offset))
+		return -EINVAL;
+
+	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
+			       a.offset >> PAGE_SHIFT);
+}
+#endif /* __ARCH_WANT_SYS_OLD_MMAP */
+
+/*
+ * split a vma into two pieces at address 'addr', a new vma is allocated either
+ * for the first part or the tail.
+ */
+int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
+	      unsigned long addr, int new_below)
+{
+	struct vm_area_struct *new;
+	struct vm_region *region;
+	unsigned long npages;
+
+	/* we're only permitted to split anonymous regions (these should have
+	 * only a single usage on the region) */
+	if (vma->vm_file)
+		return -ENOMEM;
+
+	if (mm->map_count >= sysctl_max_map_count)
+		return -ENOMEM;
+
+	region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
+	if (!region)
+		return -ENOMEM;
+
+	new = vm_area_dup(vma);
+	if (!new) {
+		kmem_cache_free(vm_region_jar, region);
+		return -ENOMEM;
+	}
+
+	/* most fields are the same, copy all, and then fixup */
+	*region = *vma->vm_region;
+	new->vm_region = region;
+
+	npages = (addr - vma->vm_start) >> PAGE_SHIFT;
+
+	if (new_below) {
+		region->vm_top = region->vm_end = new->vm_end = addr;
+	} else {
+		region->vm_start = new->vm_start = addr;
+		region->vm_pgoff = new->vm_pgoff += npages;
+	}
+
+	if (new->vm_ops && new->vm_ops->open)
+		new->vm_ops->open(new);
+
+	delete_vma_from_mm(vma);
+	down_write(&nommu_region_sem);
+	delete_nommu_region(vma->vm_region);
+	if (new_below) {
+		vma->vm_region->vm_start = vma->vm_start = addr;
+		vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
+	} else {
+		vma->vm_region->vm_end = vma->vm_end = addr;
+		vma->vm_region->vm_top = addr;
+	}
+	add_nommu_region(vma->vm_region);
+	add_nommu_region(new->vm_region);
+	up_write(&nommu_region_sem);
+	add_vma_to_mm(mm, vma);
+	add_vma_to_mm(mm, new);
+	return 0;
+}
+
+/*
+ * shrink a VMA by removing the specified chunk from either the beginning or
+ * the end
+ */
+static int shrink_vma(struct mm_struct *mm,
+		      struct vm_area_struct *vma,
+		      unsigned long from, unsigned long to)
+{
+	struct vm_region *region;
+
+	/* adjust the VMA's pointers, which may reposition it in the MM's tree
+	 * and list */
+	delete_vma_from_mm(vma);
+	if (from > vma->vm_start)
+		vma->vm_end = from;
+	else
+		vma->vm_start = to;
+	add_vma_to_mm(mm, vma);
+
+	/* cut the backing region down to size */
+	region = vma->vm_region;
+	BUG_ON(region->vm_usage != 1);
+
+	down_write(&nommu_region_sem);
+	delete_nommu_region(region);
+	if (from > region->vm_start) {
+		to = region->vm_top;
+		region->vm_top = region->vm_end = from;
+	} else {
+		region->vm_start = to;
+	}
+	add_nommu_region(region);
+	up_write(&nommu_region_sem);
+
+	free_page_series(from, to);
+	return 0;
+}
+
+/*
+ * release a mapping
+ * - under NOMMU conditions the chunk to be unmapped must be backed by a single
+ *   VMA, though it need not cover the whole VMA
+ */
+int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
+{
+	struct vm_area_struct *vma;
+	unsigned long end;
+	int ret;
+
+	len = PAGE_ALIGN(len);
+	if (len == 0)
+		return -EINVAL;
+
+	end = start + len;
+
+	/* find the first potentially overlapping VMA */
+	vma = find_vma(mm, start);
+	if (!vma) {
+		static int limit;
+		if (limit < 5) {
+			pr_warn("munmap of memory not mmapped by process %d (%s): 0x%lx-0x%lx\n",
+					current->pid, current->comm,
+					start, start + len - 1);
+			limit++;
+		}
+		return -EINVAL;
+	}
+
+	/* we're allowed to split an anonymous VMA but not a file-backed one */
+	if (vma->vm_file) {
+		do {
+			if (start > vma->vm_start)
+				return -EINVAL;
+			if (end == vma->vm_end)
+				goto erase_whole_vma;
+			vma = vma->vm_next;
+		} while (vma);
+		return -EINVAL;
+	} else {
+		/* the chunk must be a subset of the VMA found */
+		if (start == vma->vm_start && end == vma->vm_end)
+			goto erase_whole_vma;
+		if (start < vma->vm_start || end > vma->vm_end)
+			return -EINVAL;
+		if (offset_in_page(start))
+			return -EINVAL;
+		if (end != vma->vm_end && offset_in_page(end))
+			return -EINVAL;
+		if (start != vma->vm_start && end != vma->vm_end) {
+			ret = split_vma(mm, vma, start, 1);
+			if (ret < 0)
+				return ret;
+		}
+		return shrink_vma(mm, vma, start, end);
+	}
+
+erase_whole_vma:
+	delete_vma_from_mm(vma);
+	delete_vma(mm, vma);
+	return 0;
+}
+EXPORT_SYMBOL(do_munmap);
+
+int vm_munmap(unsigned long addr, size_t len)
+{
+	struct mm_struct *mm = current->mm;
+	int ret;
+
+	mmap_write_lock(mm);
+	ret = do_munmap(mm, addr, len, NULL);
+	mmap_write_unlock(mm);
+	return ret;
+}
+EXPORT_SYMBOL(vm_munmap);
+
+SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
+{
+	return vm_munmap(addr, len);
+}
+
+/*
+ * release all the mappings made in a process's VM space
+ */
+void exit_mmap(struct mm_struct *mm)
+{
+	struct vm_area_struct *vma;
+
+	if (!mm)
+		return;
+
+	mm->total_vm = 0;
+
+	while ((vma = mm->mmap)) {
+		mm->mmap = vma->vm_next;
+		delete_vma_from_mm(vma);
+		delete_vma(mm, vma);
+		cond_resched();
+	}
+}
+
+int vm_brk(unsigned long addr, unsigned long len)
+{
+	return -ENOMEM;
+}
+
+/*
+ * expand (or shrink) an existing mapping, potentially moving it at the same
+ * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
+ *
+ * under NOMMU conditions, we only permit changing a mapping's size, and only
+ * as long as it stays within the region allocated by do_mmap_private() and the
+ * block is not shareable
+ *
+ * MREMAP_FIXED is not supported under NOMMU conditions
+ */
+static unsigned long do_mremap(unsigned long addr,
+			unsigned long old_len, unsigned long new_len,
+			unsigned long flags, unsigned long new_addr)
+{
+	struct vm_area_struct *vma;
+
+	/* insanity checks first */
+	old_len = PAGE_ALIGN(old_len);
+	new_len = PAGE_ALIGN(new_len);
+	if (old_len == 0 || new_len == 0)
+		return (unsigned long) -EINVAL;
+
+	if (offset_in_page(addr))
+		return -EINVAL;
+
+	if (flags & MREMAP_FIXED && new_addr != addr)
+		return (unsigned long) -EINVAL;
+
+	vma = find_vma_exact(current->mm, addr, old_len);
+	if (!vma)
+		return (unsigned long) -EINVAL;
+
+	if (vma->vm_end != vma->vm_start + old_len)
+		return (unsigned long) -EFAULT;
+
+	if (vma->vm_flags & VM_MAYSHARE)
+		return (unsigned long) -EPERM;
+
+	if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
+		return (unsigned long) -ENOMEM;
+
+	/* all checks complete - do it */
+	vma->vm_end = vma->vm_start + new_len;
+	return vma->vm_start;
+}
+
+SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
+		unsigned long, new_len, unsigned long, flags,
+		unsigned long, new_addr)
+{
+	unsigned long ret;
+
+	mmap_write_lock(current->mm);
+	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
+	mmap_write_unlock(current->mm);
+	return ret;
+}
+
+struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
+			 unsigned int foll_flags)
+{
+	return NULL;
+}
+
+int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
+		unsigned long pfn, unsigned long size, pgprot_t prot)
+{
+	if (addr != (pfn << PAGE_SHIFT))
+		return -EINVAL;
+
+	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
+	return 0;
+}
+EXPORT_SYMBOL(remap_pfn_range);
+
+int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
+{
+	unsigned long pfn = start >> PAGE_SHIFT;
+	unsigned long vm_len = vma->vm_end - vma->vm_start;
+
+	pfn += vma->vm_pgoff;
+	return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
+}
+EXPORT_SYMBOL(vm_iomap_memory);
+
+int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
+			unsigned long pgoff)
+{
+	unsigned int size = vma->vm_end - vma->vm_start;
+
+	if (!(vma->vm_flags & VM_USERMAP))
+		return -EINVAL;
+
+	vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
+	vma->vm_end = vma->vm_start + size;
+
+	return 0;
+}
+EXPORT_SYMBOL(remap_vmalloc_range);
+
+unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
+	unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+	return -ENOMEM;
+}
+
+vm_fault_t filemap_fault(struct vm_fault *vmf)
+{
+	BUG();
+	return 0;
+}
+EXPORT_SYMBOL(filemap_fault);
+
+void filemap_map_pages(struct vm_fault *vmf,
+		pgoff_t start_pgoff, pgoff_t end_pgoff)
+{
+	BUG();
+}
+EXPORT_SYMBOL(filemap_map_pages);
+
+int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+		unsigned long addr, void *buf, int len, unsigned int gup_flags)
+{
+	struct vm_area_struct *vma;
+	int write = gup_flags & FOLL_WRITE;
+
+	if (mmap_read_lock_killable(mm))
+		return 0;
+
+	/* the access must start within one of the target process's mappings */
+	vma = find_vma(mm, addr);
+	if (vma) {
+		/* don't overrun this mapping */
+		if (addr + len >= vma->vm_end)
+			len = vma->vm_end - addr;
+
+		/* only read or write mappings where it is permitted */
+		if (write && vma->vm_flags & VM_MAYWRITE)
+			copy_to_user_page(vma, NULL, addr,
+					 (void *) addr, buf, len);
+		else if (!write && vma->vm_flags & VM_MAYREAD)
+			copy_from_user_page(vma, NULL, addr,
+					    buf, (void *) addr, len);
+		else
+			len = 0;
+	} else {
+		len = 0;
+	}
+
+	mmap_read_unlock(mm);
+
+	return len;
+}
+
+/**
+ * access_remote_vm - access another process' address space
+ * @mm:		the mm_struct of the target address space
+ * @addr:	start address to access
+ * @buf:	source or destination buffer
+ * @len:	number of bytes to transfer
+ * @gup_flags:	flags modifying lookup behaviour
+ *
+ * The caller must hold a reference on @mm.
+ */
+int access_remote_vm(struct mm_struct *mm, unsigned long addr,
+		void *buf, int len, unsigned int gup_flags)
+{
+	return __access_remote_vm(NULL, mm, addr, buf, len, gup_flags);
+}
+
+/*
+ * Access another process' address space.
+ * - source/target buffer must be kernel space
+ */
+int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
+		unsigned int gup_flags)
+{
+	struct mm_struct *mm;
+
+	if (addr + len < addr)
+		return 0;
+
+	mm = get_task_mm(tsk);
+	if (!mm)
+		return 0;
+
+	len = __access_remote_vm(tsk, mm, addr, buf, len, gup_flags);
+
+	mmput(mm);
+	return len;
+}
+EXPORT_SYMBOL_GPL(access_process_vm);
+
+/**
+ * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
+ * @inode: The inode to check
+ * @size: The current filesize of the inode
+ * @newsize: The proposed filesize of the inode
+ *
+ * Check the shared mappings on an inode on behalf of a shrinking truncate to
+ * make sure that any outstanding VMAs aren't broken and then shrink the
+ * vm_regions that extend beyond so that do_mmap() doesn't
+ * automatically grant mappings that are too large.
+ */
+int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
+				size_t newsize)
+{
+	struct vm_area_struct *vma;
+	struct vm_region *region;
+	pgoff_t low, high;
+	size_t r_size, r_top;
+
+	low = newsize >> PAGE_SHIFT;
+	high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+	down_write(&nommu_region_sem);
+	i_mmap_lock_read(inode->i_mapping);
+
+	/* search for VMAs that fall within the dead zone */
+	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
+		/* found one - only interested if it's shared out of the page
+		 * cache */
+		if (vma->vm_flags & VM_SHARED) {
+			i_mmap_unlock_read(inode->i_mapping);
+			up_write(&nommu_region_sem);
+			return -ETXTBSY; /* not quite true, but near enough */
+		}
+	}
+
+	/* reduce any regions that overlap the dead zone - if in existence,
+	 * these will be pointed to by VMAs that don't overlap the dead zone
+	 *
+	 * we don't check for any regions that start beyond the EOF as there
+	 * shouldn't be any
+	 */
+	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, 0, ULONG_MAX) {
+		if (!(vma->vm_flags & VM_SHARED))
+			continue;
+
+		region = vma->vm_region;
+		r_size = region->vm_top - region->vm_start;
+		r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
+
+		if (r_top > newsize) {
+			region->vm_top -= r_top - newsize;
+			if (region->vm_end > region->vm_top)
+				region->vm_end = region->vm_top;
+		}
+	}
+
+	i_mmap_unlock_read(inode->i_mapping);
+	up_write(&nommu_region_sem);
+	return 0;
+}
+
+/*
+ * Initialise sysctl_user_reserve_kbytes.
+ *
+ * This is intended to prevent a user from starting a single memory hogging
+ * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
+ * mode.
+ *
+ * The default value is min(3% of free memory, 128MB)
+ * 128MB is enough to recover with sshd/login, bash, and top/kill.
+ */
+static int __meminit init_user_reserve(void)
+{
+	unsigned long free_kbytes;
+
+	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+
+	sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
+	return 0;
+}
+subsys_initcall(init_user_reserve);
+
+/*
+ * Initialise sysctl_admin_reserve_kbytes.
+ *
+ * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
+ * to log in and kill a memory hogging process.
+ *
+ * Systems with more than 256MB will reserve 8MB, enough to recover
+ * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
+ * only reserve 3% of free pages by default.
+ */
+static int __meminit init_admin_reserve(void)
+{
+	unsigned long free_kbytes;
+
+	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+
+	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
+	return 0;
+}
+subsys_initcall(init_admin_reserve);