2 * linux/arch/arm/mm/mmap.c
4 #include <linux/config.h>
7 #include <linux/mman.h>
10 #include <asm/system.h>
12 #define COLOUR_ALIGN(addr,pgoff) \
13 ((((addr)+SHMLBA-1)&~(SHMLBA-1)) + \
14 (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
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
22 * We unconditionally provide this function for all cases, however
23 * in the VIVT case, we optimise out the alignment rules.
26 arch_get_unmapped_area(struct file *filp, unsigned long addr,
27 unsigned long len, unsigned long pgoff, unsigned long flags)
29 struct mm_struct *mm = current->mm;
30 struct vm_area_struct *vma;
31 unsigned long start_addr;
33 unsigned int cache_type;
34 int do_align = 0, aliasing = 0;
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.
41 cache_type = read_cpuid(CPUID_CACHETYPE);
42 if (cache_type != read_cpuid(CPUID_ID)) {
43 aliasing = (cache_type | cache_type >> 12) & (1 << 11);
45 do_align = filp || flags & MAP_SHARED;
53 * We should enforce the MAP_FIXED case. However, currently
54 * the generic kernel code doesn't allow us to handle this.
56 if (flags & MAP_FIXED) {
57 if (aliasing && flags & MAP_SHARED && addr & (SHMLBA - 1))
67 addr = COLOUR_ALIGN(addr, pgoff);
69 addr = PAGE_ALIGN(addr);
71 vma = find_vma(mm, addr);
72 if (TASK_SIZE - len >= addr &&
73 (!vma || addr + len <= vma->vm_start))
76 start_addr = addr = mm->free_area_cache;
80 addr = COLOUR_ALIGN(addr, pgoff);
82 addr = PAGE_ALIGN(addr);
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) {
88 * Start a new search - just in case we missed
91 if (start_addr != TASK_UNMAPPED_BASE) {
92 start_addr = addr = TASK_UNMAPPED_BASE;
97 if (!vma || addr + len <= vma->vm_start) {
99 * Remember the place where we stopped the search:
101 mm->free_area_cache = addr + len;
106 addr = COLOUR_ALIGN(addr, pgoff);