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 } 116 117