arch/arm/mm/mmap.c

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