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[PATCH] Add install_special_mapping

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This patch adds a utility function install_special_mapping, for creating a
special vma using a fixed set of preallocated pages as backing, such as for a
vDSO.  This consolidates some nearly identical code used for vDSO mapping
reimplemented for different architectures.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2007-02-08 14:20:41 -08:00 committed by Linus Torvalds
parent a25700a53f
commit fa5dc22f85
2 changed files with 75 additions and 0 deletions
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3
include/linux/mm.h
View file

@ -1030,6 +1030,9 @@ extern struct vm_area_struct *copy_vma(struct vm_area_struct **,
unsigned long addr, unsigned long len, pgoff_t pgoff);
extern void exit_mmap(struct mm_struct *);
extern int may_expand_vm(struct mm_struct *mm, unsigned long npages);
extern int install_special_mapping(struct mm_struct *mm,
unsigned long addr, unsigned long len,
unsigned long flags, struct page **pages);
extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);

72
mm/mmap.c
View file

@ -2101,3 +2101,75 @@ int may_expand_vm(struct mm_struct *mm, unsigned long npages)
return 0;
return 1;
}
static struct page *special_mapping_nopage(struct vm_area_struct *vma,
unsigned long address, int *type)
{
struct page **pages;
BUG_ON(address < vma->vm_start || address >= vma->vm_end);
address -= vma->vm_start;
for (pages = vma->vm_private_data; address > 0 && *pages; ++pages)
address -= PAGE_SIZE;
if (*pages) {
struct page *page = *pages;
get_page(page);
return page;
}
return NOPAGE_SIGBUS;
}
/*
* Having a close hook prevents vma merging regardless of flags.
*/
static void special_mapping_close(struct vm_area_struct *vma)
{
}
static struct vm_operations_struct special_mapping_vmops = {
.close = special_mapping_close,
.nopage = special_mapping_nopage,
};
/*
* Called with mm->mmap_sem held for writing.
* Insert a new vma covering the given region, with the given flags.
* Its pages are supplied by the given array of struct page *.
* The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
* The region past the last page supplied will always produce SIGBUS.
* The array pointer and the pages it points to are assumed to stay alive
* for as long as this mapping might exist.
*/
int install_special_mapping(struct mm_struct *mm,
unsigned long addr, unsigned long len,
unsigned long vm_flags, struct page **pages)
{
struct vm_area_struct *vma;
vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (unlikely(vma == NULL))
return -ENOMEM;
vma->vm_mm = mm;
vma->vm_start = addr;
vma->vm_end = addr + len;
vma->vm_flags = vm_flags | mm->def_flags;
vma->vm_page_prot = protection_map[vma->vm_flags & 7];
vma->vm_ops = &special_mapping_vmops;
vma->vm_private_data = pages;
if (unlikely(insert_vm_struct(mm, vma))) {
kmem_cache_free(vm_area_cachep, vma);
return -ENOMEM;
}
mm->total_vm += len >> PAGE_SHIFT;
return 0;
}