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[PATCH] NOMMU: Set BDI capabilities for /dev/mem and /dev/kmem

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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: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
David Howells 2006-09-27 01:50:16 -07:00 committed by Linus Torvalds
parent 0ec76a110f
commit 5da6185bca
3 changed files with 61 additions and 0 deletions
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39
drivers/char/mem.c
View file

@ -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;

20
fs/char_dev.c
View file

@ -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);

2
include/linux/cdev.h
View file

@ -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