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Commit 5da6185b authored by David Howells's avatar David Howells Committed by Linus Torvalds
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[PATCH] NOMMU: Set BDI capabilities for /dev/mem and /dev/kmem 



Set the backing device info capabilities for /dev/mem and /dev/kmem to
permit direct sharing under no-MMU conditions and full mapping capabilities
under MMU conditions.  Make the BDI used by these available to all directly
mappable character devices.

Also comment the capabilities for /dev/zero.

[akpm@osdl.org: ifdef reductions]
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 0ec76a11

drivers/char/mem.c

+39 −0
Original line number Diff line number Diff line
@@ -238,6 +238,32 @@ static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn, 
}

#endif



#ifndef CONFIG_MMU

static unsigned long get_unmapped_area_mem(struct file *file,

					   unsigned long addr,

					   unsigned long len,

					   unsigned long pgoff,

					   unsigned long flags)

{

	if (!valid_mmap_phys_addr_range(pgoff, len))

		return (unsigned long) -EINVAL;

	return pgoff;

}



/* can't do an in-place private mapping if there's no MMU */

static inline int private_mapping_ok(struct vm_area_struct *vma)

{

	return vma->vm_flags & VM_MAYSHARE;

}

#else

#define get_unmapped_area_mem	NULL



static inline int private_mapping_ok(struct vm_area_struct *vma)

{

	return 1;

}

#endif



static int mmap_mem(struct file * file, struct vm_area_struct * vma)

{

	size_t size = vma->vm_end - vma->vm_start;
@@ -245,6 +271,9 @@ static int mmap_mem(struct file * file, struct vm_area_struct * vma) 
	if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))

		return -EINVAL;



	if (!private_mapping_ok(vma))

		return -ENOSYS;



	vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,

						 size,

						 vma->vm_page_prot);
@@ -782,6 +811,7 @@ static const struct file_operations mem_fops = { 
	.write		= write_mem,

	.mmap		= mmap_mem,

	.open		= open_mem,

	.get_unmapped_area = get_unmapped_area_mem,

};



static const struct file_operations kmem_fops = {
@@ -790,6 +820,7 @@ static const struct file_operations kmem_fops = { 
	.write		= write_kmem,

	.mmap		= mmap_kmem,

	.open		= open_kmem,

	.get_unmapped_area = get_unmapped_area_mem,

};



static const struct file_operations null_fops = {
@@ -815,6 +846,10 @@ static const struct file_operations zero_fops = { 
	.mmap		= mmap_zero,

};



/*

 * capabilities for /dev/zero

 * - permits private mappings, "copies" are taken of the source of zeros

 */

static struct backing_dev_info zero_bdi = {

	.capabilities	= BDI_CAP_MAP_COPY,

};
@@ -862,9 +897,13 @@ static int memory_open(struct inode * inode, struct file * filp) 
	switch (iminor(inode)) {

		case 1:

			filp->f_op = &mem_fops;

			filp->f_mapping->backing_dev_info =

				&directly_mappable_cdev_bdi;

			break;

		case 2:

			filp->f_op = &kmem_fops;

			filp->f_mapping->backing_dev_info =

				&directly_mappable_cdev_bdi;

			break;

		case 3:

			filp->f_op = &null_fops;

fs/char_dev.c

+20 −0
Original line number Diff line number Diff line
@@ -19,11 +19,30 @@ 
#include <linux/kobj_map.h>

#include <linux/cdev.h>

#include <linux/mutex.h>

#include <linux/backing-dev.h>



#ifdef CONFIG_KMOD

#include <linux/kmod.h>

#endif



/*

 * capabilities for /dev/mem, /dev/kmem and similar directly mappable character

 * devices

 * - permits shared-mmap for read, write and/or exec

 * - does not permit private mmap in NOMMU mode (can't do COW)

 * - no readahead or I/O queue unplugging required

 */

struct backing_dev_info directly_mappable_cdev_bdi = {

	.capabilities	= (

#ifdef CONFIG_MMU

		/* permit private copies of the data to be taken */

		BDI_CAP_MAP_COPY |

#endif

		/* permit direct mmap, for read, write or exec */

		BDI_CAP_MAP_DIRECT |

		BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP),

};



static struct kobj_map *cdev_map;



static DEFINE_MUTEX(chrdevs_lock);
@@ -461,3 +480,4 @@ EXPORT_SYMBOL(cdev_del); 
EXPORT_SYMBOL(cdev_add);

EXPORT_SYMBOL(register_chrdev);

EXPORT_SYMBOL(unregister_chrdev);

EXPORT_SYMBOL(directly_mappable_cdev_bdi);

include/linux/cdev.h

+2 −0
Original line number Diff line number Diff line
@@ -23,5 +23,7 @@ void cdev_del(struct cdev *); 


void cd_forget(struct inode *);



extern struct backing_dev_info directly_mappable_cdev_bdi;



#endif

#endif