The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/mm/nommu.c

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    1 /*
    2  *  linux/mm/nommu.c
    3  *
    4  *  Replacement code for mm functions to support CPU's that don't
    5  *  have any form of memory management unit (thus no virtual memory).
    6  *
    7  *  See Documentation/nommu-mmap.txt
    8  *
    9  *  Copyright (c) 2004-2008 David Howells <dhowells@redhat.com>
   10  *  Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
   11  *  Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
   12  *  Copyright (c) 2002      Greg Ungerer <gerg@snapgear.com>
   13  *  Copyright (c) 2007-2010 Paul Mundt <lethal@linux-sh.org>
   14  */
   15 
   16 #include <linux/export.h>
   17 #include <linux/mm.h>
   18 #include <linux/mman.h>
   19 #include <linux/swap.h>
   20 #include <linux/file.h>
   21 #include <linux/highmem.h>
   22 #include <linux/pagemap.h>
   23 #include <linux/slab.h>
   24 #include <linux/vmalloc.h>
   25 #include <linux/blkdev.h>
   26 #include <linux/backing-dev.h>
   27 #include <linux/mount.h>
   28 #include <linux/personality.h>
   29 #include <linux/security.h>
   30 #include <linux/syscalls.h>
   31 #include <linux/audit.h>
   32 
   33 #include <asm/uaccess.h>
   34 #include <asm/tlb.h>
   35 #include <asm/tlbflush.h>
   36 #include <asm/mmu_context.h>
   37 #include "internal.h"
   38 
   39 #if 0
   40 #define kenter(FMT, ...) \
   41         printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__)
   42 #define kleave(FMT, ...) \
   43         printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
   44 #define kdebug(FMT, ...) \
   45         printk(KERN_DEBUG "xxx" FMT"yyy\n", ##__VA_ARGS__)
   46 #else
   47 #define kenter(FMT, ...) \
   48         no_printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__)
   49 #define kleave(FMT, ...) \
   50         no_printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
   51 #define kdebug(FMT, ...) \
   52         no_printk(KERN_DEBUG FMT"\n", ##__VA_ARGS__)
   53 #endif
   54 
   55 void *high_memory;
   56 struct page *mem_map;
   57 unsigned long max_mapnr;
   58 unsigned long num_physpages;
   59 unsigned long highest_memmap_pfn;
   60 struct percpu_counter vm_committed_as;
   61 int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */
   62 int sysctl_overcommit_ratio = 50; /* default is 50% */
   63 int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
   64 int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
   65 int heap_stack_gap = 0;
   66 
   67 atomic_long_t mmap_pages_allocated;
   68 
   69 /*
   70  * The global memory commitment made in the system can be a metric
   71  * that can be used to drive ballooning decisions when Linux is hosted
   72  * as a guest. On Hyper-V, the host implements a policy engine for dynamically
   73  * balancing memory across competing virtual machines that are hosted.
   74  * Several metrics drive this policy engine including the guest reported
   75  * memory commitment.
   76  */
   77 unsigned long vm_memory_committed(void)
   78 {
   79         return percpu_counter_read_positive(&vm_committed_as);
   80 }
   81 
   82 EXPORT_SYMBOL_GPL(vm_memory_committed);
   83 
   84 EXPORT_SYMBOL(mem_map);
   85 EXPORT_SYMBOL(num_physpages);
   86 
   87 /* list of mapped, potentially shareable regions */
   88 static struct kmem_cache *vm_region_jar;
   89 struct rb_root nommu_region_tree = RB_ROOT;
   90 DECLARE_RWSEM(nommu_region_sem);
   91 
   92 const struct vm_operations_struct generic_file_vm_ops = {
   93 };
   94 
   95 /*
   96  * Return the total memory allocated for this pointer, not
   97  * just what the caller asked for.
   98  *
   99  * Doesn't have to be accurate, i.e. may have races.
  100  */
  101 unsigned int kobjsize(const void *objp)
  102 {
  103         struct page *page;
  104 
  105         /*
  106          * If the object we have should not have ksize performed on it,
  107          * return size of 0
  108          */
  109         if (!objp || !virt_addr_valid(objp))
  110                 return 0;
  111 
  112         page = virt_to_head_page(objp);
  113 
  114         /*
  115          * If the allocator sets PageSlab, we know the pointer came from
  116          * kmalloc().
  117          */
  118         if (PageSlab(page))
  119                 return ksize(objp);
  120 
  121         /*
  122          * If it's not a compound page, see if we have a matching VMA
  123          * region. This test is intentionally done in reverse order,
  124          * so if there's no VMA, we still fall through and hand back
  125          * PAGE_SIZE for 0-order pages.
  126          */
  127         if (!PageCompound(page)) {
  128                 struct vm_area_struct *vma;
  129 
  130                 vma = find_vma(current->mm, (unsigned long)objp);
  131                 if (vma)
  132                         return vma->vm_end - vma->vm_start;
  133         }
  134 
  135         /*
  136          * The ksize() function is only guaranteed to work for pointers
  137          * returned by kmalloc(). So handle arbitrary pointers here.
  138          */
  139         return PAGE_SIZE << compound_order(page);
  140 }
  141 
  142 int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
  143                      unsigned long start, int nr_pages, unsigned int foll_flags,
  144                      struct page **pages, struct vm_area_struct **vmas,
  145                      int *retry)
  146 {
  147         struct vm_area_struct *vma;
  148         unsigned long vm_flags;
  149         int i;
  150 
  151         /* calculate required read or write permissions.
  152          * If FOLL_FORCE is set, we only require the "MAY" flags.
  153          */
  154         vm_flags  = (foll_flags & FOLL_WRITE) ?
  155                         (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
  156         vm_flags &= (foll_flags & FOLL_FORCE) ?
  157                         (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
  158 
  159         for (i = 0; i < nr_pages; i++) {
  160                 vma = find_vma(mm, start);
  161                 if (!vma)
  162                         goto finish_or_fault;
  163 
  164                 /* protect what we can, including chardevs */
  165                 if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
  166                     !(vm_flags & vma->vm_flags))
  167                         goto finish_or_fault;
  168 
  169                 if (pages) {
  170                         pages[i] = virt_to_page(start);
  171                         if (pages[i])
  172                                 page_cache_get(pages[i]);
  173                 }
  174                 if (vmas)
  175                         vmas[i] = vma;
  176                 start = (start + PAGE_SIZE) & PAGE_MASK;
  177         }
  178 
  179         return i;
  180 
  181 finish_or_fault:
  182         return i ? : -EFAULT;
  183 }
  184 
  185 /*
  186  * get a list of pages in an address range belonging to the specified process
  187  * and indicate the VMA that covers each page
  188  * - this is potentially dodgy as we may end incrementing the page count of a
  189  *   slab page or a secondary page from a compound page
  190  * - don't permit access to VMAs that don't support it, such as I/O mappings
  191  */
  192 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
  193         unsigned long start, int nr_pages, int write, int force,
  194         struct page **pages, struct vm_area_struct **vmas)
  195 {
  196         int flags = 0;
  197 
  198         if (write)
  199                 flags |= FOLL_WRITE;
  200         if (force)
  201                 flags |= FOLL_FORCE;
  202 
  203         return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
  204                                 NULL);
  205 }
  206 EXPORT_SYMBOL(get_user_pages);
  207 
  208 /**
  209  * follow_pfn - look up PFN at a user virtual address
  210  * @vma: memory mapping
  211  * @address: user virtual address
  212  * @pfn: location to store found PFN
  213  *
  214  * Only IO mappings and raw PFN mappings are allowed.
  215  *
  216  * Returns zero and the pfn at @pfn on success, -ve otherwise.
  217  */
  218 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
  219         unsigned long *pfn)
  220 {
  221         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
  222                 return -EINVAL;
  223 
  224         *pfn = address >> PAGE_SHIFT;
  225         return 0;
  226 }
  227 EXPORT_SYMBOL(follow_pfn);
  228 
  229 DEFINE_RWLOCK(vmlist_lock);
  230 struct vm_struct *vmlist;
  231 
  232 void vfree(const void *addr)
  233 {
  234         kfree(addr);
  235 }
  236 EXPORT_SYMBOL(vfree);
  237 
  238 void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
  239 {
  240         /*
  241          *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
  242          * returns only a logical address.
  243          */
  244         return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
  245 }
  246 EXPORT_SYMBOL(__vmalloc);
  247 
  248 void *vmalloc_user(unsigned long size)
  249 {
  250         void *ret;
  251 
  252         ret = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
  253                         PAGE_KERNEL);
  254         if (ret) {
  255                 struct vm_area_struct *vma;
  256 
  257                 down_write(&current->mm->mmap_sem);
  258                 vma = find_vma(current->mm, (unsigned long)ret);
  259                 if (vma)
  260                         vma->vm_flags |= VM_USERMAP;
  261                 up_write(&current->mm->mmap_sem);
  262         }
  263 
  264         return ret;
  265 }
  266 EXPORT_SYMBOL(vmalloc_user);
  267 
  268 struct page *vmalloc_to_page(const void *addr)
  269 {
  270         return virt_to_page(addr);
  271 }
  272 EXPORT_SYMBOL(vmalloc_to_page);
  273 
  274 unsigned long vmalloc_to_pfn(const void *addr)
  275 {
  276         return page_to_pfn(virt_to_page(addr));
  277 }
  278 EXPORT_SYMBOL(vmalloc_to_pfn);
  279 
  280 long vread(char *buf, char *addr, unsigned long count)
  281 {
  282         memcpy(buf, addr, count);
  283         return count;
  284 }
  285 
  286 long vwrite(char *buf, char *addr, unsigned long count)
  287 {
  288         /* Don't allow overflow */
  289         if ((unsigned long) addr + count < count)
  290                 count = -(unsigned long) addr;
  291 
  292         memcpy(addr, buf, count);
  293         return(count);
  294 }
  295 
  296 /*
  297  *      vmalloc  -  allocate virtually continguos memory
  298  *
  299  *      @size:          allocation size
  300  *
  301  *      Allocate enough pages to cover @size from the page level
  302  *      allocator and map them into continguos kernel virtual space.
  303  *
  304  *      For tight control over page level allocator and protection flags
  305  *      use __vmalloc() instead.
  306  */
  307 void *vmalloc(unsigned long size)
  308 {
  309        return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
  310 }
  311 EXPORT_SYMBOL(vmalloc);
  312 
  313 /*
  314  *      vzalloc - allocate virtually continguos memory with zero fill
  315  *
  316  *      @size:          allocation size
  317  *
  318  *      Allocate enough pages to cover @size from the page level
  319  *      allocator and map them into continguos kernel virtual space.
  320  *      The memory allocated is set to zero.
  321  *
  322  *      For tight control over page level allocator and protection flags
  323  *      use __vmalloc() instead.
  324  */
  325 void *vzalloc(unsigned long size)
  326 {
  327         return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
  328                         PAGE_KERNEL);
  329 }
  330 EXPORT_SYMBOL(vzalloc);
  331 
  332 /**
  333  * vmalloc_node - allocate memory on a specific node
  334  * @size:       allocation size
  335  * @node:       numa node
  336  *
  337  * Allocate enough pages to cover @size from the page level
  338  * allocator and map them into contiguous kernel virtual space.
  339  *
  340  * For tight control over page level allocator and protection flags
  341  * use __vmalloc() instead.
  342  */
  343 void *vmalloc_node(unsigned long size, int node)
  344 {
  345         return vmalloc(size);
  346 }
  347 EXPORT_SYMBOL(vmalloc_node);
  348 
  349 /**
  350  * vzalloc_node - allocate memory on a specific node with zero fill
  351  * @size:       allocation size
  352  * @node:       numa node
  353  *
  354  * Allocate enough pages to cover @size from the page level
  355  * allocator and map them into contiguous kernel virtual space.
  356  * The memory allocated is set to zero.
  357  *
  358  * For tight control over page level allocator and protection flags
  359  * use __vmalloc() instead.
  360  */
  361 void *vzalloc_node(unsigned long size, int node)
  362 {
  363         return vzalloc(size);
  364 }
  365 EXPORT_SYMBOL(vzalloc_node);
  366 
  367 #ifndef PAGE_KERNEL_EXEC
  368 # define PAGE_KERNEL_EXEC PAGE_KERNEL
  369 #endif
  370 
  371 /**
  372  *      vmalloc_exec  -  allocate virtually contiguous, executable memory
  373  *      @size:          allocation size
  374  *
  375  *      Kernel-internal function to allocate enough pages to cover @size
  376  *      the page level allocator and map them into contiguous and
  377  *      executable kernel virtual space.
  378  *
  379  *      For tight control over page level allocator and protection flags
  380  *      use __vmalloc() instead.
  381  */
  382 
  383 void *vmalloc_exec(unsigned long size)
  384 {
  385         return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC);
  386 }
  387 
  388 /**
  389  * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
  390  *      @size:          allocation size
  391  *
  392  *      Allocate enough 32bit PA addressable pages to cover @size from the
  393  *      page level allocator and map them into continguos kernel virtual space.
  394  */
  395 void *vmalloc_32(unsigned long size)
  396 {
  397         return __vmalloc(size, GFP_KERNEL, PAGE_KERNEL);
  398 }
  399 EXPORT_SYMBOL(vmalloc_32);
  400 
  401 /**
  402  * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
  403  *      @size:          allocation size
  404  *
  405  * The resulting memory area is 32bit addressable and zeroed so it can be
  406  * mapped to userspace without leaking data.
  407  *
  408  * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
  409  * remap_vmalloc_range() are permissible.
  410  */
  411 void *vmalloc_32_user(unsigned long size)
  412 {
  413         /*
  414          * We'll have to sort out the ZONE_DMA bits for 64-bit,
  415          * but for now this can simply use vmalloc_user() directly.
  416          */
  417         return vmalloc_user(size);
  418 }
  419 EXPORT_SYMBOL(vmalloc_32_user);
  420 
  421 void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
  422 {
  423         BUG();
  424         return NULL;
  425 }
  426 EXPORT_SYMBOL(vmap);
  427 
  428 void vunmap(const void *addr)
  429 {
  430         BUG();
  431 }
  432 EXPORT_SYMBOL(vunmap);
  433 
  434 void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t prot)
  435 {
  436         BUG();
  437         return NULL;
  438 }
  439 EXPORT_SYMBOL(vm_map_ram);
  440 
  441 void vm_unmap_ram(const void *mem, unsigned int count)
  442 {
  443         BUG();
  444 }
  445 EXPORT_SYMBOL(vm_unmap_ram);
  446 
  447 void vm_unmap_aliases(void)
  448 {
  449 }
  450 EXPORT_SYMBOL_GPL(vm_unmap_aliases);
  451 
  452 /*
  453  * Implement a stub for vmalloc_sync_all() if the architecture chose not to
  454  * have one.
  455  */
  456 void  __attribute__((weak)) vmalloc_sync_all(void)
  457 {
  458 }
  459 
  460 /**
  461  *      alloc_vm_area - allocate a range of kernel address space
  462  *      @size:          size of the area
  463  *
  464  *      Returns:        NULL on failure, vm_struct on success
  465  *
  466  *      This function reserves a range of kernel address space, and
  467  *      allocates pagetables to map that range.  No actual mappings
  468  *      are created.  If the kernel address space is not shared
  469  *      between processes, it syncs the pagetable across all
  470  *      processes.
  471  */
  472 struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)
  473 {
  474         BUG();
  475         return NULL;
  476 }
  477 EXPORT_SYMBOL_GPL(alloc_vm_area);
  478 
  479 void free_vm_area(struct vm_struct *area)
  480 {
  481         BUG();
  482 }
  483 EXPORT_SYMBOL_GPL(free_vm_area);
  484 
  485 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
  486                    struct page *page)
  487 {
  488         return -EINVAL;
  489 }
  490 EXPORT_SYMBOL(vm_insert_page);
  491 
  492 /*
  493  *  sys_brk() for the most part doesn't need the global kernel
  494  *  lock, except when an application is doing something nasty
  495  *  like trying to un-brk an area that has already been mapped
  496  *  to a regular file.  in this case, the unmapping will need
  497  *  to invoke file system routines that need the global lock.
  498  */
  499 SYSCALL_DEFINE1(brk, unsigned long, brk)
  500 {
  501         struct mm_struct *mm = current->mm;
  502 
  503         if (brk < mm->start_brk || brk > mm->context.end_brk)
  504                 return mm->brk;
  505 
  506         if (mm->brk == brk)
  507                 return mm->brk;
  508 
  509         /*
  510          * Always allow shrinking brk
  511          */
  512         if (brk <= mm->brk) {
  513                 mm->brk = brk;
  514                 return brk;
  515         }
  516 
  517         /*
  518          * Ok, looks good - let it rip.
  519          */
  520         flush_icache_range(mm->brk, brk);
  521         return mm->brk = brk;
  522 }
  523 
  524 /*
  525  * initialise the VMA and region record slabs
  526  */
  527 void __init mmap_init(void)
  528 {
  529         int ret;
  530 
  531         ret = percpu_counter_init(&vm_committed_as, 0);
  532         VM_BUG_ON(ret);
  533         vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC);
  534 }
  535 
  536 /*
  537  * validate the region tree
  538  * - the caller must hold the region lock
  539  */
  540 #ifdef CONFIG_DEBUG_NOMMU_REGIONS
  541 static noinline void validate_nommu_regions(void)
  542 {
  543         struct vm_region *region, *last;
  544         struct rb_node *p, *lastp;
  545 
  546         lastp = rb_first(&nommu_region_tree);
  547         if (!lastp)
  548                 return;
  549 
  550         last = rb_entry(lastp, struct vm_region, vm_rb);
  551         BUG_ON(unlikely(last->vm_end <= last->vm_start));
  552         BUG_ON(unlikely(last->vm_top < last->vm_end));
  553 
  554         while ((p = rb_next(lastp))) {
  555                 region = rb_entry(p, struct vm_region, vm_rb);
  556                 last = rb_entry(lastp, struct vm_region, vm_rb);
  557 
  558                 BUG_ON(unlikely(region->vm_end <= region->vm_start));
  559                 BUG_ON(unlikely(region->vm_top < region->vm_end));
  560                 BUG_ON(unlikely(region->vm_start < last->vm_top));
  561 
  562                 lastp = p;
  563         }
  564 }
  565 #else
  566 static void validate_nommu_regions(void)
  567 {
  568 }
  569 #endif
  570 
  571 /*
  572  * add a region into the global tree
  573  */
  574 static void add_nommu_region(struct vm_region *region)
  575 {
  576         struct vm_region *pregion;
  577         struct rb_node **p, *parent;
  578 
  579         validate_nommu_regions();
  580 
  581         parent = NULL;
  582         p = &nommu_region_tree.rb_node;
  583         while (*p) {
  584                 parent = *p;
  585                 pregion = rb_entry(parent, struct vm_region, vm_rb);
  586                 if (region->vm_start < pregion->vm_start)
  587                         p = &(*p)->rb_left;
  588                 else if (region->vm_start > pregion->vm_start)
  589                         p = &(*p)->rb_right;
  590                 else if (pregion == region)
  591                         return;
  592                 else
  593                         BUG();
  594         }
  595 
  596         rb_link_node(&region->vm_rb, parent, p);
  597         rb_insert_color(&region->vm_rb, &nommu_region_tree);
  598 
  599         validate_nommu_regions();
  600 }
  601 
  602 /*
  603  * delete a region from the global tree
  604  */
  605 static void delete_nommu_region(struct vm_region *region)
  606 {
  607         BUG_ON(!nommu_region_tree.rb_node);
  608 
  609         validate_nommu_regions();
  610         rb_erase(&region->vm_rb, &nommu_region_tree);
  611         validate_nommu_regions();
  612 }
  613 
  614 /*
  615  * free a contiguous series of pages
  616  */
  617 static void free_page_series(unsigned long from, unsigned long to)
  618 {
  619         for (; from < to; from += PAGE_SIZE) {
  620                 struct page *page = virt_to_page(from);
  621 
  622                 kdebug("- free %lx", from);
  623                 atomic_long_dec(&mmap_pages_allocated);
  624                 if (page_count(page) != 1)
  625                         kdebug("free page %p: refcount not one: %d",
  626                                page, page_count(page));
  627                 put_page(page);
  628         }
  629 }
  630 
  631 /*
  632  * release a reference to a region
  633  * - the caller must hold the region semaphore for writing, which this releases
  634  * - the region may not have been added to the tree yet, in which case vm_top
  635  *   will equal vm_start
  636  */
  637 static void __put_nommu_region(struct vm_region *region)
  638         __releases(nommu_region_sem)
  639 {
  640         kenter("%p{%d}", region, region->vm_usage);
  641 
  642         BUG_ON(!nommu_region_tree.rb_node);
  643 
  644         if (--region->vm_usage == 0) {
  645                 if (region->vm_top > region->vm_start)
  646                         delete_nommu_region(region);
  647                 up_write(&nommu_region_sem);
  648 
  649                 if (region->vm_file)
  650                         fput(region->vm_file);
  651 
  652                 /* IO memory and memory shared directly out of the pagecache
  653                  * from ramfs/tmpfs mustn't be released here */
  654                 if (region->vm_flags & VM_MAPPED_COPY) {
  655                         kdebug("free series");
  656                         free_page_series(region->vm_start, region->vm_top);
  657                 }
  658                 kmem_cache_free(vm_region_jar, region);
  659         } else {
  660                 up_write(&nommu_region_sem);
  661         }
  662 }
  663 
  664 /*
  665  * release a reference to a region
  666  */
  667 static void put_nommu_region(struct vm_region *region)
  668 {
  669         down_write(&nommu_region_sem);
  670         __put_nommu_region(region);
  671 }
  672 
  673 /*
  674  * update protection on a vma
  675  */
  676 static void protect_vma(struct vm_area_struct *vma, unsigned long flags)
  677 {
  678 #ifdef CONFIG_MPU
  679         struct mm_struct *mm = vma->vm_mm;
  680         long start = vma->vm_start & PAGE_MASK;
  681         while (start < vma->vm_end) {
  682                 protect_page(mm, start, flags);
  683                 start += PAGE_SIZE;
  684         }
  685         update_protections(mm);
  686 #endif
  687 }
  688 
  689 /*
  690  * add a VMA into a process's mm_struct in the appropriate place in the list
  691  * and tree and add to the address space's page tree also if not an anonymous
  692  * page
  693  * - should be called with mm->mmap_sem held writelocked
  694  */
  695 static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
  696 {
  697         struct vm_area_struct *pvma, *prev;
  698         struct address_space *mapping;
  699         struct rb_node **p, *parent, *rb_prev;
  700 
  701         kenter(",%p", vma);
  702 
  703         BUG_ON(!vma->vm_region);
  704 
  705         mm->map_count++;
  706         vma->vm_mm = mm;
  707 
  708         protect_vma(vma, vma->vm_flags);
  709 
  710         /* add the VMA to the mapping */
  711         if (vma->vm_file) {
  712                 mapping = vma->vm_file->f_mapping;
  713 
  714                 mutex_lock(&mapping->i_mmap_mutex);
  715                 flush_dcache_mmap_lock(mapping);
  716                 vma_interval_tree_insert(vma, &mapping->i_mmap);
  717                 flush_dcache_mmap_unlock(mapping);
  718                 mutex_unlock(&mapping->i_mmap_mutex);
  719         }
  720 
  721         /* add the VMA to the tree */
  722         parent = rb_prev = NULL;
  723         p = &mm->mm_rb.rb_node;
  724         while (*p) {
  725                 parent = *p;
  726                 pvma = rb_entry(parent, struct vm_area_struct, vm_rb);
  727 
  728                 /* sort by: start addr, end addr, VMA struct addr in that order
  729                  * (the latter is necessary as we may get identical VMAs) */
  730                 if (vma->vm_start < pvma->vm_start)
  731                         p = &(*p)->rb_left;
  732                 else if (vma->vm_start > pvma->vm_start) {
  733                         rb_prev = parent;
  734                         p = &(*p)->rb_right;
  735                 } else if (vma->vm_end < pvma->vm_end)
  736                         p = &(*p)->rb_left;
  737                 else if (vma->vm_end > pvma->vm_end) {
  738                         rb_prev = parent;
  739                         p = &(*p)->rb_right;
  740                 } else if (vma < pvma)
  741                         p = &(*p)->rb_left;
  742                 else if (vma > pvma) {
  743                         rb_prev = parent;
  744                         p = &(*p)->rb_right;
  745                 } else
  746                         BUG();
  747         }
  748 
  749         rb_link_node(&vma->vm_rb, parent, p);
  750         rb_insert_color(&vma->vm_rb, &mm->mm_rb);
  751 
  752         /* add VMA to the VMA list also */
  753         prev = NULL;
  754         if (rb_prev)
  755                 prev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
  756 
  757         __vma_link_list(mm, vma, prev, parent);
  758 }
  759 
  760 /*
  761  * delete a VMA from its owning mm_struct and address space
  762  */
  763 static void delete_vma_from_mm(struct vm_area_struct *vma)
  764 {
  765         struct address_space *mapping;
  766         struct mm_struct *mm = vma->vm_mm;
  767 
  768         kenter("%p", vma);
  769 
  770         protect_vma(vma, 0);
  771 
  772         mm->map_count--;
  773         if (mm->mmap_cache == vma)
  774                 mm->mmap_cache = NULL;
  775 
  776         /* remove the VMA from the mapping */
  777         if (vma->vm_file) {
  778                 mapping = vma->vm_file->f_mapping;
  779 
  780                 mutex_lock(&mapping->i_mmap_mutex);
  781                 flush_dcache_mmap_lock(mapping);
  782                 vma_interval_tree_remove(vma, &mapping->i_mmap);
  783                 flush_dcache_mmap_unlock(mapping);
  784                 mutex_unlock(&mapping->i_mmap_mutex);
  785         }
  786 
  787         /* remove from the MM's tree and list */
  788         rb_erase(&vma->vm_rb, &mm->mm_rb);
  789 
  790         if (vma->vm_prev)
  791                 vma->vm_prev->vm_next = vma->vm_next;
  792         else
  793                 mm->mmap = vma->vm_next;
  794 
  795         if (vma->vm_next)
  796                 vma->vm_next->vm_prev = vma->vm_prev;
  797 }
  798 
  799 /*
  800  * destroy a VMA record
  801  */
  802 static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
  803 {
  804         kenter("%p", vma);
  805         if (vma->vm_ops && vma->vm_ops->close)
  806                 vma->vm_ops->close(vma);
  807         if (vma->vm_file)
  808                 fput(vma->vm_file);
  809         put_nommu_region(vma->vm_region);
  810         kmem_cache_free(vm_area_cachep, vma);
  811 }
  812 
  813 /*
  814  * look up the first VMA in which addr resides, NULL if none
  815  * - should be called with mm->mmap_sem at least held readlocked
  816  */
  817 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
  818 {
  819         struct vm_area_struct *vma;
  820 
  821         /* check the cache first */
  822         vma = mm->mmap_cache;
  823         if (vma && vma->vm_start <= addr && vma->vm_end > addr)
  824                 return vma;
  825 
  826         /* trawl the list (there may be multiple mappings in which addr
  827          * resides) */
  828         for (vma = mm->mmap; vma; vma = vma->vm_next) {
  829                 if (vma->vm_start > addr)
  830                         return NULL;
  831                 if (vma->vm_end > addr) {
  832                         mm->mmap_cache = vma;
  833                         return vma;
  834                 }
  835         }
  836 
  837         return NULL;
  838 }
  839 EXPORT_SYMBOL(find_vma);
  840 
  841 /*
  842  * find a VMA
  843  * - we don't extend stack VMAs under NOMMU conditions
  844  */
  845 struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
  846 {
  847         return find_vma(mm, addr);
  848 }
  849 
  850 /*
  851  * expand a stack to a given address
  852  * - not supported under NOMMU conditions
  853  */
  854 int expand_stack(struct vm_area_struct *vma, unsigned long address)
  855 {
  856         return -ENOMEM;
  857 }
  858 
  859 /*
  860  * look up the first VMA exactly that exactly matches addr
  861  * - should be called with mm->mmap_sem at least held readlocked
  862  */
  863 static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
  864                                              unsigned long addr,
  865                                              unsigned long len)
  866 {
  867         struct vm_area_struct *vma;
  868         unsigned long end = addr + len;
  869 
  870         /* check the cache first */
  871         vma = mm->mmap_cache;
  872         if (vma && vma->vm_start == addr && vma->vm_end == end)
  873                 return vma;
  874 
  875         /* trawl the list (there may be multiple mappings in which addr
  876          * resides) */
  877         for (vma = mm->mmap; vma; vma = vma->vm_next) {
  878                 if (vma->vm_start < addr)
  879                         continue;
  880                 if (vma->vm_start > addr)
  881                         return NULL;
  882                 if (vma->vm_end == end) {
  883                         mm->mmap_cache = vma;
  884                         return vma;
  885                 }
  886         }
  887 
  888         return NULL;
  889 }
  890 
  891 /*
  892  * determine whether a mapping should be permitted and, if so, what sort of
  893  * mapping we're capable of supporting
  894  */
  895 static int validate_mmap_request(struct file *file,
  896                                  unsigned long addr,
  897                                  unsigned long len,
  898                                  unsigned long prot,
  899                                  unsigned long flags,
  900                                  unsigned long pgoff,
  901                                  unsigned long *_capabilities)
  902 {
  903         unsigned long capabilities, rlen;
  904         int ret;
  905 
  906         /* do the simple checks first */
  907         if (flags & MAP_FIXED) {
  908                 printk(KERN_DEBUG
  909                        "%d: Can't do fixed-address/overlay mmap of RAM\n",
  910                        current->pid);
  911                 return -EINVAL;
  912         }
  913 
  914         if ((flags & MAP_TYPE) != MAP_PRIVATE &&
  915             (flags & MAP_TYPE) != MAP_SHARED)
  916                 return -EINVAL;
  917 
  918         if (!len)
  919                 return -EINVAL;
  920 
  921         /* Careful about overflows.. */
  922         rlen = PAGE_ALIGN(len);
  923         if (!rlen || rlen > TASK_SIZE)
  924                 return -ENOMEM;
  925 
  926         /* offset overflow? */
  927         if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
  928                 return -EOVERFLOW;
  929 
  930         if (file) {
  931                 /* validate file mapping requests */
  932                 struct address_space *mapping;
  933 
  934                 /* files must support mmap */
  935                 if (!file->f_op || !file->f_op->mmap)
  936                         return -ENODEV;
  937 
  938                 /* work out if what we've got could possibly be shared
  939                  * - we support chardevs that provide their own "memory"
  940                  * - we support files/blockdevs that are memory backed
  941                  */
  942                 mapping = file->f_mapping;
  943                 if (!mapping)
  944                         mapping = file->f_path.dentry->d_inode->i_mapping;
  945 
  946                 capabilities = 0;
  947                 if (mapping && mapping->backing_dev_info)
  948                         capabilities = mapping->backing_dev_info->capabilities;
  949 
  950                 if (!capabilities) {
  951                         /* no explicit capabilities set, so assume some
  952                          * defaults */
  953                         switch (file->f_path.dentry->d_inode->i_mode & S_IFMT) {
  954                         case S_IFREG:
  955                         case S_IFBLK:
  956                                 capabilities = BDI_CAP_MAP_COPY;
  957                                 break;
  958 
  959                         case S_IFCHR:
  960                                 capabilities =
  961                                         BDI_CAP_MAP_DIRECT |
  962                                         BDI_CAP_READ_MAP |
  963                                         BDI_CAP_WRITE_MAP;
  964                                 break;
  965 
  966                         default:
  967                                 return -EINVAL;
  968                         }
  969                 }
  970 
  971                 /* eliminate any capabilities that we can't support on this
  972                  * device */
  973                 if (!file->f_op->get_unmapped_area)
  974                         capabilities &= ~BDI_CAP_MAP_DIRECT;
  975                 if (!file->f_op->read)
  976                         capabilities &= ~BDI_CAP_MAP_COPY;
  977 
  978                 /* The file shall have been opened with read permission. */
  979                 if (!(file->f_mode & FMODE_READ))
  980                         return -EACCES;
  981 
  982                 if (flags & MAP_SHARED) {
  983                         /* do checks for writing, appending and locking */
  984                         if ((prot & PROT_WRITE) &&
  985                             !(file->f_mode & FMODE_WRITE))
  986                                 return -EACCES;
  987 
  988                         if (IS_APPEND(file->f_path.dentry->d_inode) &&
  989                             (file->f_mode & FMODE_WRITE))
  990                                 return -EACCES;
  991 
  992                         if (locks_verify_locked(file->f_path.dentry->d_inode))
  993                                 return -EAGAIN;
  994 
  995                         if (!(capabilities & BDI_CAP_MAP_DIRECT))
  996                                 return -ENODEV;
  997 
  998                         /* we mustn't privatise shared mappings */
  999                         capabilities &= ~BDI_CAP_MAP_COPY;
 1000                 }
 1001                 else {
 1002                         /* we're going to read the file into private memory we
 1003                          * allocate */
 1004                         if (!(capabilities & BDI_CAP_MAP_COPY))
 1005                                 return -ENODEV;
 1006 
 1007                         /* we don't permit a private writable mapping to be
 1008                          * shared with the backing device */
 1009                         if (prot & PROT_WRITE)
 1010                                 capabilities &= ~BDI_CAP_MAP_DIRECT;
 1011                 }
 1012 
 1013                 if (capabilities & BDI_CAP_MAP_DIRECT) {
 1014                         if (((prot & PROT_READ)  && !(capabilities & BDI_CAP_READ_MAP))  ||
 1015                             ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
 1016                             ((prot & PROT_EXEC)  && !(capabilities & BDI_CAP_EXEC_MAP))
 1017                             ) {
 1018                                 capabilities &= ~BDI_CAP_MAP_DIRECT;
 1019                                 if (flags & MAP_SHARED) {
 1020                                         printk(KERN_WARNING
 1021                                                "MAP_SHARED not completely supported on !MMU\n");
 1022                                         return -EINVAL;
 1023                                 }
 1024                         }
 1025                 }
 1026 
 1027                 /* handle executable mappings and implied executable
 1028                  * mappings */
 1029                 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
 1030                         if (prot & PROT_EXEC)
 1031                                 return -EPERM;
 1032                 }
 1033                 else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
 1034                         /* handle implication of PROT_EXEC by PROT_READ */
 1035                         if (current->personality & READ_IMPLIES_EXEC) {
 1036                                 if (capabilities & BDI_CAP_EXEC_MAP)
 1037                                         prot |= PROT_EXEC;
 1038                         }
 1039                 }
 1040                 else if ((prot & PROT_READ) &&
 1041                          (prot & PROT_EXEC) &&
 1042                          !(capabilities & BDI_CAP_EXEC_MAP)
 1043                          ) {
 1044                         /* backing file is not executable, try to copy */
 1045                         capabilities &= ~BDI_CAP_MAP_DIRECT;
 1046                 }
 1047         }
 1048         else {
 1049                 /* anonymous mappings are always memory backed and can be
 1050                  * privately mapped
 1051                  */
 1052                 capabilities = BDI_CAP_MAP_COPY;
 1053 
 1054                 /* handle PROT_EXEC implication by PROT_READ */
 1055                 if ((prot & PROT_READ) &&
 1056                     (current->personality & READ_IMPLIES_EXEC))
 1057                         prot |= PROT_EXEC;
 1058         }
 1059 
 1060         /* allow the security API to have its say */
 1061         ret = security_mmap_addr(addr);
 1062         if (ret < 0)
 1063                 return ret;
 1064 
 1065         /* looks okay */
 1066         *_capabilities = capabilities;
 1067         return 0;
 1068 }
 1069 
 1070 /*
 1071  * we've determined that we can make the mapping, now translate what we
 1072  * now know into VMA flags
 1073  */
 1074 static unsigned long determine_vm_flags(struct file *file,
 1075                                         unsigned long prot,
 1076                                         unsigned long flags,
 1077                                         unsigned long capabilities)
 1078 {
 1079         unsigned long vm_flags;
 1080 
 1081         vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
 1082         /* vm_flags |= mm->def_flags; */
 1083 
 1084         if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
 1085                 /* attempt to share read-only copies of mapped file chunks */
 1086                 vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
 1087                 if (file && !(prot & PROT_WRITE))
 1088                         vm_flags |= VM_MAYSHARE;
 1089         } else {
 1090                 /* overlay a shareable mapping on the backing device or inode
 1091                  * if possible - used for chardevs, ramfs/tmpfs/shmfs and
 1092                  * romfs/cramfs */
 1093                 vm_flags |= VM_MAYSHARE | (capabilities & BDI_CAP_VMFLAGS);
 1094                 if (flags & MAP_SHARED)
 1095                         vm_flags |= VM_SHARED;
 1096         }
 1097 
 1098         /* refuse to let anyone share private mappings with this process if
 1099          * it's being traced - otherwise breakpoints set in it may interfere
 1100          * with another untraced process
 1101          */
 1102         if ((flags & MAP_PRIVATE) && current->ptrace)
 1103                 vm_flags &= ~VM_MAYSHARE;
 1104 
 1105         return vm_flags;
 1106 }
 1107 
 1108 /*
 1109  * set up a shared mapping on a file (the driver or filesystem provides and
 1110  * pins the storage)
 1111  */
 1112 static int do_mmap_shared_file(struct vm_area_struct *vma)
 1113 {
 1114         int ret;
 1115 
 1116         ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
 1117         if (ret == 0) {
 1118                 vma->vm_region->vm_top = vma->vm_region->vm_end;
 1119                 return 0;
 1120         }
 1121         if (ret != -ENOSYS)
 1122                 return ret;
 1123 
 1124         /* getting -ENOSYS indicates that direct mmap isn't possible (as
 1125          * opposed to tried but failed) so we can only give a suitable error as
 1126          * it's not possible to make a private copy if MAP_SHARED was given */
 1127         return -ENODEV;
 1128 }
 1129 
 1130 /*
 1131  * set up a private mapping or an anonymous shared mapping
 1132  */
 1133 static int do_mmap_private(struct vm_area_struct *vma,
 1134                            struct vm_region *region,
 1135                            unsigned long len,
 1136                            unsigned long capabilities)
 1137 {
 1138         struct page *pages;
 1139         unsigned long total, point, n;
 1140         void *base;
 1141         int ret, order;
 1142 
 1143         /* invoke the file's mapping function so that it can keep track of
 1144          * shared mappings on devices or memory
 1145          * - VM_MAYSHARE will be set if it may attempt to share
 1146          */
 1147         if (capabilities & BDI_CAP_MAP_DIRECT) {
 1148                 ret = vma->vm_file->f_op->mmap(vma->vm_file, vma);
 1149                 if (ret == 0) {
 1150                         /* shouldn't return success if we're not sharing */
 1151                         BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
 1152                         vma->vm_region->vm_top = vma->vm_region->vm_end;
 1153                         return 0;
 1154                 }
 1155                 if (ret != -ENOSYS)
 1156                         return ret;
 1157 
 1158                 /* getting an ENOSYS error indicates that direct mmap isn't
 1159                  * possible (as opposed to tried but failed) so we'll try to
 1160                  * make a private copy of the data and map that instead */
 1161         }
 1162 
 1163 
 1164         /* allocate some memory to hold the mapping
 1165          * - note that this may not return a page-aligned address if the object
 1166          *   we're allocating is smaller than a page
 1167          */
 1168         order = get_order(len);
 1169         kdebug("alloc order %d for %lx", order, len);
 1170 
 1171         pages = alloc_pages(GFP_KERNEL, order);
 1172         if (!pages)
 1173                 goto enomem;
 1174 
 1175         total = 1 << order;
 1176         atomic_long_add(total, &mmap_pages_allocated);
 1177 
 1178         point = len >> PAGE_SHIFT;
 1179 
 1180         /* we allocated a power-of-2 sized page set, so we may want to trim off
 1181          * the excess */
 1182         if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages) {
 1183                 while (total > point) {
 1184                         order = ilog2(total - point);
 1185                         n = 1 << order;
 1186                         kdebug("shave %lu/%lu @%lu", n, total - point, total);
 1187                         atomic_long_sub(n, &mmap_pages_allocated);
 1188                         total -= n;
 1189                         set_page_refcounted(pages + total);
 1190                         __free_pages(pages + total, order);
 1191                 }
 1192         }
 1193 
 1194         for (point = 1; point < total; point++)
 1195                 set_page_refcounted(&pages[point]);
 1196 
 1197         base = page_address(pages);
 1198         region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
 1199         region->vm_start = (unsigned long) base;
 1200         region->vm_end   = region->vm_start + len;
 1201         region->vm_top   = region->vm_start + (total << PAGE_SHIFT);
 1202 
 1203         vma->vm_start = region->vm_start;
 1204         vma->vm_end   = region->vm_start + len;
 1205 
 1206         if (vma->vm_file) {
 1207                 /* read the contents of a file into the copy */
 1208                 mm_segment_t old_fs;
 1209                 loff_t fpos;
 1210 
 1211                 fpos = vma->vm_pgoff;
 1212                 fpos <<= PAGE_SHIFT;
 1213 
 1214                 old_fs = get_fs();
 1215                 set_fs(KERNEL_DS);
 1216                 ret = vma->vm_file->f_op->read(vma->vm_file, base, len, &fpos);
 1217                 set_fs(old_fs);
 1218 
 1219                 if (ret < 0)
 1220                         goto error_free;
 1221 
 1222                 /* clear the last little bit */
 1223                 if (ret < len)
 1224                         memset(base + ret, 0, len - ret);
 1225 
 1226         }
 1227 
 1228         return 0;
 1229 
 1230 error_free:
 1231         free_page_series(region->vm_start, region->vm_top);
 1232         region->vm_start = vma->vm_start = 0;
 1233         region->vm_end   = vma->vm_end = 0;
 1234         region->vm_top   = 0;
 1235         return ret;
 1236 
 1237 enomem:
 1238         printk("Allocation of length %lu from process %d (%s) failed\n",
 1239                len, current->pid, current->comm);
 1240         show_free_areas(0);
 1241         return -ENOMEM;
 1242 }
 1243 
 1244 /*
 1245  * handle mapping creation for uClinux
 1246  */
 1247 unsigned long do_mmap_pgoff(struct file *file,
 1248                             unsigned long addr,
 1249                             unsigned long len,
 1250                             unsigned long prot,
 1251                             unsigned long flags,
 1252                             unsigned long pgoff)
 1253 {
 1254         struct vm_area_struct *vma;
 1255         struct vm_region *region;
 1256         struct rb_node *rb;
 1257         unsigned long capabilities, vm_flags, result;
 1258         int ret;
 1259 
 1260         kenter(",%lx,%lx,%lx,%lx,%lx", addr, len, prot, flags, pgoff);
 1261 
 1262         /* decide whether we should attempt the mapping, and if so what sort of
 1263          * mapping */
 1264         ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
 1265                                     &capabilities);
 1266         if (ret < 0) {
 1267                 kleave(" = %d [val]", ret);
 1268                 return ret;
 1269         }
 1270 
 1271         /* we ignore the address hint */
 1272         addr = 0;
 1273         len = PAGE_ALIGN(len);
 1274 
 1275         /* we've determined that we can make the mapping, now translate what we
 1276          * now know into VMA flags */
 1277         vm_flags = determine_vm_flags(file, prot, flags, capabilities);
 1278 
 1279         /* we're going to need to record the mapping */
 1280         region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
 1281         if (!region)
 1282                 goto error_getting_region;
 1283 
 1284         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 1285         if (!vma)
 1286                 goto error_getting_vma;
 1287 
 1288         region->vm_usage = 1;
 1289         region->vm_flags = vm_flags;
 1290         region->vm_pgoff = pgoff;
 1291 
 1292         INIT_LIST_HEAD(&vma->anon_vma_chain);
 1293         vma->vm_flags = vm_flags;
 1294         vma->vm_pgoff = pgoff;
 1295 
 1296         if (file) {
 1297                 region->vm_file = get_file(file);
 1298                 vma->vm_file = get_file(file);
 1299         }
 1300 
 1301         down_write(&nommu_region_sem);
 1302 
 1303         /* if we want to share, we need to check for regions created by other
 1304          * mmap() calls that overlap with our proposed mapping
 1305          * - we can only share with a superset match on most regular files
 1306          * - shared mappings on character devices and memory backed files are
 1307          *   permitted to overlap inexactly as far as we are concerned for in
 1308          *   these cases, sharing is handled in the driver or filesystem rather
 1309          *   than here
 1310          */
 1311         if (vm_flags & VM_MAYSHARE) {
 1312                 struct vm_region *pregion;
 1313                 unsigned long pglen, rpglen, pgend, rpgend, start;
 1314 
 1315                 pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 1316                 pgend = pgoff + pglen;
 1317 
 1318                 for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
 1319                         pregion = rb_entry(rb, struct vm_region, vm_rb);
 1320 
 1321                         if (!(pregion->vm_flags & VM_MAYSHARE))
 1322                                 continue;
 1323 
 1324                         /* search for overlapping mappings on the same file */
 1325                         if (pregion->vm_file->f_path.dentry->d_inode !=
 1326                             file->f_path.dentry->d_inode)
 1327                                 continue;
 1328 
 1329                         if (pregion->vm_pgoff >= pgend)
 1330                                 continue;
 1331 
 1332                         rpglen = pregion->vm_end - pregion->vm_start;
 1333                         rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
 1334                         rpgend = pregion->vm_pgoff + rpglen;
 1335                         if (pgoff >= rpgend)
 1336                                 continue;
 1337 
 1338                         /* handle inexactly overlapping matches between
 1339                          * mappings */
 1340                         if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
 1341                             !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
 1342                                 /* new mapping is not a subset of the region */
 1343                                 if (!(capabilities & BDI_CAP_MAP_DIRECT))
 1344                                         goto sharing_violation;
 1345                                 continue;
 1346                         }
 1347 
 1348                         /* we've found a region we can share */
 1349                         pregion->vm_usage++;
 1350                         vma->vm_region = pregion;
 1351                         start = pregion->vm_start;
 1352                         start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
 1353                         vma->vm_start = start;
 1354                         vma->vm_end = start + len;
 1355 
 1356                         if (pregion->vm_flags & VM_MAPPED_COPY) {
 1357                                 kdebug("share copy");
 1358                                 vma->vm_flags |= VM_MAPPED_COPY;
 1359                         } else {
 1360                                 kdebug("share mmap");
 1361                                 ret = do_mmap_shared_file(vma);
 1362                                 if (ret < 0) {
 1363                                         vma->vm_region = NULL;
 1364                                         vma->vm_start = 0;
 1365                                         vma->vm_end = 0;
 1366                                         pregion->vm_usage--;
 1367                                         pregion = NULL;
 1368                                         goto error_just_free;
 1369                                 }
 1370                         }
 1371                         fput(region->vm_file);
 1372                         kmem_cache_free(vm_region_jar, region);
 1373                         region = pregion;
 1374                         result = start;
 1375                         goto share;
 1376                 }
 1377 
 1378                 /* obtain the address at which to make a shared mapping
 1379                  * - this is the hook for quasi-memory character devices to
 1380                  *   tell us the location of a shared mapping
 1381                  */
 1382                 if (capabilities & BDI_CAP_MAP_DIRECT) {
 1383                         addr = file->f_op->get_unmapped_area(file, addr, len,
 1384                                                              pgoff, flags);
 1385                         if (IS_ERR_VALUE(addr)) {
 1386                                 ret = addr;
 1387                                 if (ret != -ENOSYS)
 1388                                         goto error_just_free;
 1389 
 1390                                 /* the driver refused to tell us where to site
 1391                                  * the mapping so we'll have to attempt to copy
 1392                                  * it */
 1393                                 ret = -ENODEV;
 1394                                 if (!(capabilities & BDI_CAP_MAP_COPY))
 1395                                         goto error_just_free;
 1396 
 1397                                 capabilities &= ~BDI_CAP_MAP_DIRECT;
 1398                         } else {
 1399                                 vma->vm_start = region->vm_start = addr;
 1400                                 vma->vm_end = region->vm_end = addr + len;
 1401                         }
 1402                 }
 1403         }
 1404 
 1405         vma->vm_region = region;
 1406 
 1407         /* set up the mapping
 1408          * - the region is filled in if BDI_CAP_MAP_DIRECT is still set
 1409          */
 1410         if (file && vma->vm_flags & VM_SHARED)
 1411                 ret = do_mmap_shared_file(vma);
 1412         else
 1413                 ret = do_mmap_private(vma, region, len, capabilities);
 1414         if (ret < 0)
 1415                 goto error_just_free;
 1416         add_nommu_region(region);
 1417 
 1418         /* clear anonymous mappings that don't ask for uninitialized data */
 1419         if (!vma->vm_file && !(flags & MAP_UNINITIALIZED))
 1420                 memset((void *)region->vm_start, 0,
 1421                        region->vm_end - region->vm_start);
 1422 
 1423         /* okay... we have a mapping; now we have to register it */
 1424         result = vma->vm_start;
 1425 
 1426         current->mm->total_vm += len >> PAGE_SHIFT;
 1427 
 1428 share:
 1429         add_vma_to_mm(current->mm, vma);
 1430 
 1431         /* we flush the region from the icache only when the first executable
 1432          * mapping of it is made  */
 1433         if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
 1434                 flush_icache_range(region->vm_start, region->vm_end);
 1435                 region->vm_icache_flushed = true;
 1436         }
 1437 
 1438         up_write(&nommu_region_sem);
 1439 
 1440         kleave(" = %lx", result);
 1441         return result;
 1442 
 1443 error_just_free:
 1444         up_write(&nommu_region_sem);
 1445 error:
 1446         if (region->vm_file)
 1447                 fput(region->vm_file);
 1448         kmem_cache_free(vm_region_jar, region);
 1449         if (vma->vm_file)
 1450                 fput(vma->vm_file);
 1451         kmem_cache_free(vm_area_cachep, vma);
 1452         kleave(" = %d", ret);
 1453         return ret;
 1454 
 1455 sharing_violation:
 1456         up_write(&nommu_region_sem);
 1457         printk(KERN_WARNING "Attempt to share mismatched mappings\n");
 1458         ret = -EINVAL;
 1459         goto error;
 1460 
 1461 error_getting_vma:
 1462         kmem_cache_free(vm_region_jar, region);
 1463         printk(KERN_WARNING "Allocation of vma for %lu byte allocation"
 1464                " from process %d failed\n",
 1465                len, current->pid);
 1466         show_free_areas(0);
 1467         return -ENOMEM;
 1468 
 1469 error_getting_region:
 1470         printk(KERN_WARNING "Allocation of vm region for %lu byte allocation"
 1471                " from process %d failed\n",
 1472                len, current->pid);
 1473         show_free_areas(0);
 1474         return -ENOMEM;
 1475 }
 1476 
 1477 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 1478                 unsigned long, prot, unsigned long, flags,
 1479                 unsigned long, fd, unsigned long, pgoff)
 1480 {
 1481         struct file *file = NULL;
 1482         unsigned long retval = -EBADF;
 1483 
 1484         audit_mmap_fd(fd, flags);
 1485         if (!(flags & MAP_ANONYMOUS)) {
 1486                 file = fget(fd);
 1487                 if (!file)
 1488                         goto out;
 1489         }
 1490 
 1491         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
 1492 
 1493         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
 1494 
 1495         if (file)
 1496                 fput(file);
 1497 out:
 1498         return retval;
 1499 }
 1500 
 1501 #ifdef __ARCH_WANT_SYS_OLD_MMAP
 1502 struct mmap_arg_struct {
 1503         unsigned long addr;
 1504         unsigned long len;
 1505         unsigned long prot;
 1506         unsigned long flags;
 1507         unsigned long fd;
 1508         unsigned long offset;
 1509 };
 1510 
 1511 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
 1512 {
 1513         struct mmap_arg_struct a;
 1514 
 1515         if (copy_from_user(&a, arg, sizeof(a)))
 1516                 return -EFAULT;
 1517         if (a.offset & ~PAGE_MASK)
 1518                 return -EINVAL;
 1519 
 1520         return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
 1521                               a.offset >> PAGE_SHIFT);
 1522 }
 1523 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
 1524 
 1525 /*
 1526  * split a vma into two pieces at address 'addr', a new vma is allocated either
 1527  * for the first part or the tail.
 1528  */
 1529 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 1530               unsigned long addr, int new_below)
 1531 {
 1532         struct vm_area_struct *new;
 1533         struct vm_region *region;
 1534         unsigned long npages;
 1535 
 1536         kenter("");
 1537 
 1538         /* we're only permitted to split anonymous regions (these should have
 1539          * only a single usage on the region) */
 1540         if (vma->vm_file)
 1541                 return -ENOMEM;
 1542 
 1543         if (mm->map_count >= sysctl_max_map_count)
 1544                 return -ENOMEM;
 1545 
 1546         region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
 1547         if (!region)
 1548                 return -ENOMEM;
 1549 
 1550         new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 1551         if (!new) {
 1552                 kmem_cache_free(vm_region_jar, region);
 1553                 return -ENOMEM;
 1554         }
 1555 
 1556         /* most fields are the same, copy all, and then fixup */
 1557         *new = *vma;
 1558         *region = *vma->vm_region;
 1559         new->vm_region = region;
 1560 
 1561         npages = (addr - vma->vm_start) >> PAGE_SHIFT;
 1562 
 1563         if (new_below) {
 1564                 region->vm_top = region->vm_end = new->vm_end = addr;
 1565         } else {
 1566                 region->vm_start = new->vm_start = addr;
 1567                 region->vm_pgoff = new->vm_pgoff += npages;
 1568         }
 1569 
 1570         if (new->vm_ops && new->vm_ops->open)
 1571                 new->vm_ops->open(new);
 1572 
 1573         delete_vma_from_mm(vma);
 1574         down_write(&nommu_region_sem);
 1575         delete_nommu_region(vma->vm_region);
 1576         if (new_below) {
 1577                 vma->vm_region->vm_start = vma->vm_start = addr;
 1578                 vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
 1579         } else {
 1580                 vma->vm_region->vm_end = vma->vm_end = addr;
 1581                 vma->vm_region->vm_top = addr;
 1582         }
 1583         add_nommu_region(vma->vm_region);
 1584         add_nommu_region(new->vm_region);
 1585         up_write(&nommu_region_sem);
 1586         add_vma_to_mm(mm, vma);
 1587         add_vma_to_mm(mm, new);
 1588         return 0;
 1589 }
 1590 
 1591 /*
 1592  * shrink a VMA by removing the specified chunk from either the beginning or
 1593  * the end
 1594  */
 1595 static int shrink_vma(struct mm_struct *mm,
 1596                       struct vm_area_struct *vma,
 1597                       unsigned long from, unsigned long to)
 1598 {
 1599         struct vm_region *region;
 1600 
 1601         kenter("");
 1602 
 1603         /* adjust the VMA's pointers, which may reposition it in the MM's tree
 1604          * and list */
 1605         delete_vma_from_mm(vma);
 1606         if (from > vma->vm_start)
 1607                 vma->vm_end = from;
 1608         else
 1609                 vma->vm_start = to;
 1610         add_vma_to_mm(mm, vma);
 1611 
 1612         /* cut the backing region down to size */
 1613         region = vma->vm_region;
 1614         BUG_ON(region->vm_usage != 1);
 1615 
 1616         down_write(&nommu_region_sem);
 1617         delete_nommu_region(region);
 1618         if (from > region->vm_start) {
 1619                 to = region->vm_top;
 1620                 region->vm_top = region->vm_end = from;
 1621         } else {
 1622                 region->vm_start = to;
 1623         }
 1624         add_nommu_region(region);
 1625         up_write(&nommu_region_sem);
 1626 
 1627         free_page_series(from, to);
 1628         return 0;
 1629 }
 1630 
 1631 /*
 1632  * release a mapping
 1633  * - under NOMMU conditions the chunk to be unmapped must be backed by a single
 1634  *   VMA, though it need not cover the whole VMA
 1635  */
 1636 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
 1637 {
 1638         struct vm_area_struct *vma;
 1639         unsigned long end;
 1640         int ret;
 1641 
 1642         kenter(",%lx,%zx", start, len);
 1643 
 1644         len = PAGE_ALIGN(len);
 1645         if (len == 0)
 1646                 return -EINVAL;
 1647 
 1648         end = start + len;
 1649 
 1650         /* find the first potentially overlapping VMA */
 1651         vma = find_vma(mm, start);
 1652         if (!vma) {
 1653                 static int limit = 0;
 1654                 if (limit < 5) {
 1655                         printk(KERN_WARNING
 1656                                "munmap of memory not mmapped by process %d"
 1657                                " (%s): 0x%lx-0x%lx\n",
 1658                                current->pid, current->comm,
 1659                                start, start + len - 1);
 1660                         limit++;
 1661                 }
 1662                 return -EINVAL;
 1663         }
 1664 
 1665         /* we're allowed to split an anonymous VMA but not a file-backed one */
 1666         if (vma->vm_file) {
 1667                 do {
 1668                         if (start > vma->vm_start) {
 1669                                 kleave(" = -EINVAL [miss]");
 1670                                 return -EINVAL;
 1671                         }
 1672                         if (end == vma->vm_end)
 1673                                 goto erase_whole_vma;
 1674                         vma = vma->vm_next;
 1675                 } while (vma);
 1676                 kleave(" = -EINVAL [split file]");
 1677                 return -EINVAL;
 1678         } else {
 1679                 /* the chunk must be a subset of the VMA found */
 1680                 if (start == vma->vm_start && end == vma->vm_end)
 1681                         goto erase_whole_vma;
 1682                 if (start < vma->vm_start || end > vma->vm_end) {
 1683                         kleave(" = -EINVAL [superset]");
 1684                         return -EINVAL;
 1685                 }
 1686                 if (start & ~PAGE_MASK) {
 1687                         kleave(" = -EINVAL [unaligned start]");
 1688                         return -EINVAL;
 1689                 }
 1690                 if (end != vma->vm_end && end & ~PAGE_MASK) {
 1691                         kleave(" = -EINVAL [unaligned split]");
 1692                         return -EINVAL;
 1693                 }
 1694                 if (start != vma->vm_start && end != vma->vm_end) {
 1695                         ret = split_vma(mm, vma, start, 1);
 1696                         if (ret < 0) {
 1697                                 kleave(" = %d [split]", ret);
 1698                                 return ret;
 1699                         }
 1700                 }
 1701                 return shrink_vma(mm, vma, start, end);
 1702         }
 1703 
 1704 erase_whole_vma:
 1705         delete_vma_from_mm(vma);
 1706         delete_vma(mm, vma);
 1707         kleave(" = 0");
 1708         return 0;
 1709 }
 1710 EXPORT_SYMBOL(do_munmap);
 1711 
 1712 int vm_munmap(unsigned long addr, size_t len)
 1713 {
 1714         struct mm_struct *mm = current->mm;
 1715         int ret;
 1716 
 1717         down_write(&mm->mmap_sem);
 1718         ret = do_munmap(mm, addr, len);
 1719         up_write(&mm->mmap_sem);
 1720         return ret;
 1721 }
 1722 EXPORT_SYMBOL(vm_munmap);
 1723 
 1724 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
 1725 {
 1726         return vm_munmap(addr, len);
 1727 }
 1728 
 1729 /*
 1730  * release all the mappings made in a process's VM space
 1731  */
 1732 void exit_mmap(struct mm_struct *mm)
 1733 {
 1734         struct vm_area_struct *vma;
 1735 
 1736         if (!mm)
 1737                 return;
 1738 
 1739         kenter("");
 1740 
 1741         mm->total_vm = 0;
 1742 
 1743         while ((vma = mm->mmap)) {
 1744                 mm->mmap = vma->vm_next;
 1745                 delete_vma_from_mm(vma);
 1746                 delete_vma(mm, vma);
 1747                 cond_resched();
 1748         }
 1749 
 1750         kleave("");
 1751 }
 1752 
 1753 unsigned long vm_brk(unsigned long addr, unsigned long len)
 1754 {
 1755         return -ENOMEM;
 1756 }
 1757 
 1758 /*
 1759  * expand (or shrink) an existing mapping, potentially moving it at the same
 1760  * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 1761  *
 1762  * under NOMMU conditions, we only permit changing a mapping's size, and only
 1763  * as long as it stays within the region allocated by do_mmap_private() and the
 1764  * block is not shareable
 1765  *
 1766  * MREMAP_FIXED is not supported under NOMMU conditions
 1767  */
 1768 unsigned long do_mremap(unsigned long addr,
 1769                         unsigned long old_len, unsigned long new_len,
 1770                         unsigned long flags, unsigned long new_addr)
 1771 {
 1772         struct vm_area_struct *vma;
 1773 
 1774         /* insanity checks first */
 1775         old_len = PAGE_ALIGN(old_len);
 1776         new_len = PAGE_ALIGN(new_len);
 1777         if (old_len == 0 || new_len == 0)
 1778                 return (unsigned long) -EINVAL;
 1779 
 1780         if (addr & ~PAGE_MASK)
 1781                 return -EINVAL;
 1782 
 1783         if (flags & MREMAP_FIXED && new_addr != addr)
 1784                 return (unsigned long) -EINVAL;
 1785 
 1786         vma = find_vma_exact(current->mm, addr, old_len);
 1787         if (!vma)
 1788                 return (unsigned long) -EINVAL;
 1789 
 1790         if (vma->vm_end != vma->vm_start + old_len)
 1791                 return (unsigned long) -EFAULT;
 1792 
 1793         if (vma->vm_flags & VM_MAYSHARE)
 1794                 return (unsigned long) -EPERM;
 1795 
 1796         if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
 1797                 return (unsigned long) -ENOMEM;
 1798 
 1799         /* all checks complete - do it */
 1800         vma->vm_end = vma->vm_start + new_len;
 1801         return vma->vm_start;
 1802 }
 1803 EXPORT_SYMBOL(do_mremap);
 1804 
 1805 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 1806                 unsigned long, new_len, unsigned long, flags,
 1807                 unsigned long, new_addr)
 1808 {
 1809         unsigned long ret;
 1810 
 1811         down_write(&current->mm->mmap_sem);
 1812         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 1813         up_write(&current->mm->mmap_sem);
 1814         return ret;
 1815 }
 1816 
 1817 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 1818                         unsigned int foll_flags)
 1819 {
 1820         return NULL;
 1821 }
 1822 
 1823 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
 1824                 unsigned long pfn, unsigned long size, pgprot_t prot)
 1825 {
 1826         if (addr != (pfn << PAGE_SHIFT))
 1827                 return -EINVAL;
 1828 
 1829         vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
 1830         return 0;
 1831 }
 1832 EXPORT_SYMBOL(remap_pfn_range);
 1833 
 1834 int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
 1835                         unsigned long pgoff)
 1836 {
 1837         unsigned int size = vma->vm_end - vma->vm_start;
 1838 
 1839         if (!(vma->vm_flags & VM_USERMAP))
 1840                 return -EINVAL;
 1841 
 1842         vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
 1843         vma->vm_end = vma->vm_start + size;
 1844 
 1845         return 0;
 1846 }
 1847 EXPORT_SYMBOL(remap_vmalloc_range);
 1848 
 1849 unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
 1850         unsigned long len, unsigned long pgoff, unsigned long flags)
 1851 {
 1852         return -ENOMEM;
 1853 }
 1854 
 1855 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
 1856 {
 1857 }
 1858 
 1859 void unmap_mapping_range(struct address_space *mapping,
 1860                          loff_t const holebegin, loff_t const holelen,
 1861                          int even_cows)
 1862 {
 1863 }
 1864 EXPORT_SYMBOL(unmap_mapping_range);
 1865 
 1866 /*
 1867  * Check that a process has enough memory to allocate a new virtual
 1868  * mapping. 0 means there is enough memory for the allocation to
 1869  * succeed and -ENOMEM implies there is not.
 1870  *
 1871  * We currently support three overcommit policies, which are set via the
 1872  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
 1873  *
 1874  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 1875  * Additional code 2002 Jul 20 by Robert Love.
 1876  *
 1877  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
 1878  *
 1879  * Note this is a helper function intended to be used by LSMs which
 1880  * wish to use this logic.
 1881  */
 1882 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 1883 {
 1884         unsigned long free, allowed;
 1885 
 1886         vm_acct_memory(pages);
 1887 
 1888         /*
 1889          * Sometimes we want to use more memory than we have
 1890          */
 1891         if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
 1892                 return 0;
 1893 
 1894         if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
 1895                 free = global_page_state(NR_FREE_PAGES);
 1896                 free += global_page_state(NR_FILE_PAGES);
 1897 
 1898                 /*
 1899                  * shmem pages shouldn't be counted as free in this
 1900                  * case, they can't be purged, only swapped out, and
 1901                  * that won't affect the overall amount of available
 1902                  * memory in the system.
 1903                  */
 1904                 free -= global_page_state(NR_SHMEM);
 1905 
 1906                 free += nr_swap_pages;
 1907 
 1908                 /*
 1909                  * Any slabs which are created with the
 1910                  * SLAB_RECLAIM_ACCOUNT flag claim to have contents
 1911                  * which are reclaimable, under pressure.  The dentry
 1912                  * cache and most inode caches should fall into this
 1913                  */
 1914                 free += global_page_state(NR_SLAB_RECLAIMABLE);
 1915 
 1916                 /*
 1917                  * Leave reserved pages. The pages are not for anonymous pages.
 1918                  */
 1919                 if (free <= totalreserve_pages)
 1920                         goto error;
 1921                 else
 1922                         free -= totalreserve_pages;
 1923 
 1924                 /*
 1925                  * Leave the last 3% for root
 1926                  */
 1927                 if (!cap_sys_admin)
 1928                         free -= free / 32;
 1929 
 1930                 if (free > pages)
 1931                         return 0;
 1932 
 1933                 goto error;
 1934         }
 1935 
 1936         allowed = totalram_pages * sysctl_overcommit_ratio / 100;
 1937         /*
 1938          * Leave the last 3% for root
 1939          */
 1940         if (!cap_sys_admin)
 1941                 allowed -= allowed / 32;
 1942         allowed += total_swap_pages;
 1943 
 1944         /* Don't let a single process grow too big:
 1945            leave 3% of the size of this process for other processes */
 1946         if (mm)
 1947                 allowed -= mm->total_vm / 32;
 1948 
 1949         if (percpu_counter_read_positive(&vm_committed_as) < allowed)
 1950                 return 0;
 1951 
 1952 error:
 1953         vm_unacct_memory(pages);
 1954 
 1955         return -ENOMEM;
 1956 }
 1957 
 1958 int in_gate_area_no_mm(unsigned long addr)
 1959 {
 1960         return 0;
 1961 }
 1962 
 1963 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 1964 {
 1965         BUG();
 1966         return 0;
 1967 }
 1968 EXPORT_SYMBOL(filemap_fault);
 1969 
 1970 int generic_file_remap_pages(struct vm_area_struct *vma, unsigned long addr,
 1971                              unsigned long size, pgoff_t pgoff)
 1972 {
 1973         BUG();
 1974         return 0;
 1975 }
 1976 EXPORT_SYMBOL(generic_file_remap_pages);
 1977 
 1978 static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
 1979                 unsigned long addr, void *buf, int len, int write)
 1980 {
 1981         struct vm_area_struct *vma;
 1982 
 1983         down_read(&mm->mmap_sem);
 1984 
 1985         /* the access must start within one of the target process's mappings */
 1986         vma = find_vma(mm, addr);
 1987         if (vma) {
 1988                 /* don't overrun this mapping */
 1989                 if (addr + len >= vma->vm_end)
 1990                         len = vma->vm_end - addr;
 1991 
 1992                 /* only read or write mappings where it is permitted */
 1993                 if (write && vma->vm_flags & VM_MAYWRITE)
 1994                         copy_to_user_page(vma, NULL, addr,
 1995                                          (void *) addr, buf, len);
 1996                 else if (!write && vma->vm_flags & VM_MAYREAD)
 1997                         copy_from_user_page(vma, NULL, addr,
 1998                                             buf, (void *) addr, len);
 1999                 else
 2000                         len = 0;
 2001         } else {
 2002                 len = 0;
 2003         }
 2004 
 2005         up_read(&mm->mmap_sem);
 2006 
 2007         return len;
 2008 }
 2009 
 2010 /**
 2011  * @access_remote_vm - access another process' address space
 2012  * @mm:         the mm_struct of the target address space
 2013  * @addr:       start address to access
 2014  * @buf:        source or destination buffer
 2015  * @len:        number of bytes to transfer
 2016  * @write:      whether the access is a write
 2017  *
 2018  * The caller must hold a reference on @mm.
 2019  */
 2020 int access_remote_vm(struct mm_struct *mm, unsigned long addr,
 2021                 void *buf, int len, int write)
 2022 {
 2023         return __access_remote_vm(NULL, mm, addr, buf, len, write);
 2024 }
 2025 
 2026 /*
 2027  * Access another process' address space.
 2028  * - source/target buffer must be kernel space
 2029  */
 2030 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
 2031 {
 2032         struct mm_struct *mm;
 2033 
 2034         if (addr + len < addr)
 2035                 return 0;
 2036 
 2037         mm = get_task_mm(tsk);
 2038         if (!mm)
 2039                 return 0;
 2040 
 2041         len = __access_remote_vm(tsk, mm, addr, buf, len, write);
 2042 
 2043         mmput(mm);
 2044         return len;
 2045 }
 2046 
 2047 /**
 2048  * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
 2049  * @inode: The inode to check
 2050  * @size: The current filesize of the inode
 2051  * @newsize: The proposed filesize of the inode
 2052  *
 2053  * Check the shared mappings on an inode on behalf of a shrinking truncate to
 2054  * make sure that that any outstanding VMAs aren't broken and then shrink the
 2055  * vm_regions that extend that beyond so that do_mmap_pgoff() doesn't
 2056  * automatically grant mappings that are too large.
 2057  */
 2058 int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
 2059                                 size_t newsize)
 2060 {
 2061         struct vm_area_struct *vma;
 2062         struct vm_region *region;
 2063         pgoff_t low, high;
 2064         size_t r_size, r_top;
 2065 
 2066         low = newsize >> PAGE_SHIFT;
 2067         high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 2068 
 2069         down_write(&nommu_region_sem);
 2070         mutex_lock(&inode->i_mapping->i_mmap_mutex);
 2071 
 2072         /* search for VMAs that fall within the dead zone */
 2073         vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
 2074                 /* found one - only interested if it's shared out of the page
 2075                  * cache */
 2076                 if (vma->vm_flags & VM_SHARED) {
 2077                         mutex_unlock(&inode->i_mapping->i_mmap_mutex);
 2078                         up_write(&nommu_region_sem);
 2079                         return -ETXTBSY; /* not quite true, but near enough */
 2080                 }
 2081         }
 2082 
 2083         /* reduce any regions that overlap the dead zone - if in existence,
 2084          * these will be pointed to by VMAs that don't overlap the dead zone
 2085          *
 2086          * we don't check for any regions that start beyond the EOF as there
 2087          * shouldn't be any
 2088          */
 2089         vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap,
 2090                                   0, ULONG_MAX) {
 2091                 if (!(vma->vm_flags & VM_SHARED))
 2092                         continue;
 2093 
 2094                 region = vma->vm_region;
 2095                 r_size = region->vm_top - region->vm_start;
 2096                 r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
 2097 
 2098                 if (r_top > newsize) {
 2099                         region->vm_top -= r_top - newsize;
 2100                         if (region->vm_end > region->vm_top)
 2101                                 region->vm_end = region->vm_top;
 2102                 }
 2103         }
 2104 
 2105         mutex_unlock(&inode->i_mapping->i_mmap_mutex);
 2106         up_write(&nommu_region_sem);
 2107         return 0;
 2108 }

Cache object: bc11ab12ddc1aeb136552e78f57ee154


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.