git.oblomov.eu Git - linux-2.6/blob - arch/arm/mm/mmap.c

   1 /*
   2  *  linux/arch/arm/mm/mmap.c
   3  */
   4 #include <linux/fs.h>
   5 #include <linux/mm.h>
   6 #include <linux/mman.h>
   7 #include <linux/shm.h>
   8
   9 #include <asm/system.h>
  10
  11 #define COLOUR_ALIGN(addr,pgoff)                \
  12         ((((addr)+SHMLBA-1)&~(SHMLBA-1)) +      \
  13          (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
  14
  15 /*
  16  * We need to ensure that shared mappings are correctly aligned to
  17  * avoid aliasing issues with VIPT caches.  We need to ensure that
  18  * a specific page of an object is always mapped at a multiple of
  19  * SHMLBA bytes.
  20  *
  21  * We unconditionally provide this function for all cases, however
  22  * in the VIVT case, we optimise out the alignment rules.
  23  */
  24 unsigned long
  25 arch_get_unmapped_area(struct file *filp, unsigned long addr,
  26                 unsigned long len, unsigned long pgoff, unsigned long flags)
  27 {
  28         struct mm_struct *mm = current->mm;
  29         struct vm_area_struct *vma;
  30         unsigned long start_addr;
  31 #ifdef CONFIG_CPU_V6
  32         unsigned int cache_type;
  33         int do_align = 0, aliasing = 0;
  34
  35         /*
  36          * We only need to do colour alignment if either the I or D
  37          * caches alias.  This is indicated by bits 9 and 21 of the
  38          * cache type register.
  39          */
  40         cache_type = read_cpuid(CPUID_CACHETYPE);
  41         if (cache_type != read_cpuid(CPUID_ID)) {
  42                 aliasing = (cache_type | cache_type >> 12) & (1 << 11);
  43                 if (aliasing)
  44                         do_align = filp || flags & MAP_SHARED;
  45         }
  46 #else
  47 #define do_align 0
  48 #define aliasing 0
  49 #endif
  50
  51         /*
  52          * We should enforce the MAP_FIXED case.  However, currently
  53          * the generic kernel code doesn't allow us to handle this.
  54          */
  55         if (flags & MAP_FIXED) {
  56                 if (aliasing && flags & MAP_SHARED && addr & (SHMLBA - 1))
  57                         return -EINVAL;
  58                 return addr;
  59         }
  60
  61         if (len > TASK_SIZE)
  62                 return -ENOMEM;
  63
  64         if (addr) {
  65                 if (do_align)
  66                         addr = COLOUR_ALIGN(addr, pgoff);
  67                 else
  68                         addr = PAGE_ALIGN(addr);
  69
  70                 vma = find_vma(mm, addr);
  71                 if (TASK_SIZE - len >= addr &&
  72                     (!vma || addr + len <= vma->vm_start))
  73                         return addr;
  74         }
  75         if (len > mm->cached_hole_size) {
  76                 start_addr = addr = mm->free_area_cache;
  77         } else {
  78                 start_addr = addr = TASK_UNMAPPED_BASE;
  79                 mm->cached_hole_size = 0;
  80         }
  81
  82 full_search:
  83         if (do_align)
  84                 addr = COLOUR_ALIGN(addr, pgoff);
  85         else
  86                 addr = PAGE_ALIGN(addr);
  87
  88         for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
  89                 /* At this point:  (!vma || addr < vma->vm_end). */
  90                 if (TASK_SIZE - len < addr) {
  91                         /*
  92                          * Start a new search - just in case we missed
  93                          * some holes.
  94                          */
  95                         if (start_addr != TASK_UNMAPPED_BASE) {
  96                                 start_addr = addr = TASK_UNMAPPED_BASE;
  97                                 mm->cached_hole_size = 0;
  98                                 goto full_search;
  99                         }
 100                         return -ENOMEM;
 101                 }
 102                 if (!vma || addr + len <= vma->vm_start) {
 103                         /*
 104                          * Remember the place where we stopped the search:
 105                          */
 106                         mm->free_area_cache = addr + len;
 107                         return addr;
 108                 }
 109                 if (addr + mm->cached_hole_size < vma->vm_start)
 110                         mm->cached_hole_size = vma->vm_start - addr;
 111                 addr = vma->vm_end;
 112                 if (do_align)
 113                         addr = COLOUR_ALIGN(addr, pgoff);
 114         }
 115 }
 116