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Commit fa5dc22f authored by Roland McGrath's avatar Roland McGrath Committed by Linus Torvalds
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[PATCH] Add install_special_mapping 



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: default avatarRoland 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a25700a5

include/linux/mm.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

mm/mmap.c

+72 −0
Original line number Diff line number Diff line
@@ -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;

}