diff options
| -rw-r--r-- | Documentation/nommu-mmap.txt | 24 | ||||
| -rw-r--r-- | mm/nommu.c | 63 |
2 files changed, 70 insertions, 17 deletions
diff --git a/Documentation/nommu-mmap.txt b/Documentation/nommu-mmap.txt index 83f4b083d57..3ce89066493 100644 --- a/Documentation/nommu-mmap.txt +++ b/Documentation/nommu-mmap.txt @@ -128,6 +128,30 @@ FURTHER NOTES ON NO-MMU MMAP error will result if they don't. This is most likely to be encountered with character device files, pipes, fifos and sockets. + +============= +NO-MMU MREMAP +============= + +The mremap() function is partially supported. It may change the size of a +mapping, and may move it[*] if MREMAP_MAYMOVE is specified and if the new size +of the mapping exceeds the size of the slab object currently occupied by the +memory to which the mapping refers, or if a smaller slab object could be used. + +MREMAP_FIXED is not supported, though it is ignored if there's no change of +address and the object does not need to be moved. + +Shared mappings may not be moved. Shareable mappings may not be moved either, +even if they are not currently shared. + +The mremap() function must be given an exact match for base address and size of +a previously mapped object. It may not be used to create holes in existing +mappings, move parts of existing mappings or resize parts of mappings. It must +act on a complete mapping. + +[*] Not currently supported. + + ============================================ PROVIDING SHAREABLE CHARACTER DEVICE SUPPORT ============================================ diff --git a/mm/nommu.c b/mm/nommu.c index 4f87b2f43a2..23cfa8ec914 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -350,6 +350,26 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) EXPORT_SYMBOL(find_vma); /* + * look up the first VMA exactly that exactly matches addr + * - should be called with mm->mmap_sem at least held readlocked + */ +static inline struct vm_area_struct *find_vma_exact(struct mm_struct *mm, + unsigned long addr) +{ + struct vm_list_struct *vml; + + /* search the vm_start ordered list */ + for (vml = mm->context.vmlist; vml; vml = vml->next) { + if (vml->vma->vm_start == addr) + return vml->vma; + if (vml->vma->vm_start > addr) + break; + } + + return NULL; +} + +/* * find a VMA in the global tree */ static inline struct vm_area_struct *find_nommu_vma(unsigned long start) @@ -1071,20 +1091,20 @@ unsigned long do_brk(unsigned long addr, unsigned long len) } /* - * Expand (or shrink) an existing mapping, potentially moving it at the - * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) + * expand (or shrink) an existing mapping, potentially moving it at the same + * time (controlled by the MREMAP_MAYMOVE flag and available VM space) * - * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise - * This option implies MREMAP_MAYMOVE. + * under NOMMU conditions, we only permit changing a mapping's size, and only + * as long as it stays within the hole allocated by the kmalloc() call in + * do_mmap_pgoff() and the block is not shareable * - * on uClinux, we only permit changing a mapping's size, and only as long as it stays within the - * hole allocated by the kmalloc() call in do_mmap_pgoff() and the block is not shareable + * MREMAP_FIXED is not supported under NOMMU conditions */ unsigned long do_mremap(unsigned long addr, unsigned long old_len, unsigned long new_len, unsigned long flags, unsigned long new_addr) { - struct vm_list_struct *vml = NULL; + struct vm_area_struct *vma; /* insanity checks first */ if (new_len == 0) @@ -1093,29 +1113,38 @@ unsigned long do_mremap(unsigned long addr, if (flags & MREMAP_FIXED && new_addr != addr) return (unsigned long) -EINVAL; - for (vml = current->mm->context.vmlist; vml; vml = vml->next) - if (vml->vma->vm_start == addr) - goto found; - - return (unsigned long) -EINVAL; + vma = find_vma_exact(current->mm, addr); + if (!vma) + return (unsigned long) -EINVAL; - found: - if (vml->vma->vm_end != vml->vma->vm_start + old_len) + if (vma->vm_end != vma->vm_start + old_len) return (unsigned long) -EFAULT; - if (vml->vma->vm_flags & VM_MAYSHARE) + if (vma->vm_flags & VM_MAYSHARE) return (unsigned long) -EPERM; if (new_len > kobjsize((void *) addr)) return (unsigned long) -ENOMEM; /* all checks complete - do it */ - vml->vma->vm_end = vml->vma->vm_start + new_len; + vma->vm_end = vma->vm_start + new_len; askedalloc -= old_len; askedalloc += new_len; - return vml->vma->vm_start; + return vma->vm_start; +} + +asmlinkage unsigned long sys_mremap(unsigned long addr, + unsigned long old_len, unsigned long new_len, + unsigned long flags, unsigned long new_addr) +{ + unsigned long ret; + + down_write(¤t->mm->mmap_sem); + ret = do_mremap(addr, old_len, new_len, flags, new_addr); + up_write(¤t->mm->mmap_sem); + return ret; } struct page *follow_page(struct vm_area_struct *vma, unsigned long address, |