Root/mm/nommu.c

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

Archive Download this file



interactive