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authorBernd Schmidt <bernds_cb1@t-online.de>2010-05-25 23:43:00 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-26 08:19:23 -0700
commit3c7b204547bc3d342a4e31196fe14803581d279f (patch)
tree87a3300d266eed413012efd0a985a72caad4a856 /mm/nommu.c
parent0cae3457b1a6e88f31020272bcfd90c178716053 (diff)
downloadvexpress-lsk-3c7b204547bc3d342a4e31196fe14803581d279f.tar.gz
nommu: allow private mappings of read-only devices
Slightly rearrange the logic that determines capabilities and vm_flags. Disable BDI_CAP_MAP_DIRECT in all cases if the device can't support the protections. Allow private readonly mappings of readonly backing devices. Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de> Signed-off-by: Mike Frysinger <vapier@gentoo.org> Acked-by: David McCullough <davidm@snapgear.com> Acked-by: Greg Ungerer <gerg@uclinux.org> Acked-by: Paul Mundt <lethal@linux-sh.org> Acked-by: David Howells <dhowells@redhat.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/nommu.c')
-rw-r--r--mm/nommu.c32
1 files changed, 18 insertions, 14 deletions
diff --git a/mm/nommu.c b/mm/nommu.c
index 63fa17d121f..b76f3ee0abe 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -918,14 +918,6 @@ static int validate_mmap_request(struct file *file,
if (!(capabilities & BDI_CAP_MAP_DIRECT))
return -ENODEV;
- if (((prot & PROT_READ) && !(capabilities & BDI_CAP_READ_MAP)) ||
- ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
- ((prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP))
- ) {
- printk("MAP_SHARED not completely supported on !MMU\n");
- return -EINVAL;
- }
-
/* we mustn't privatise shared mappings */
capabilities &= ~BDI_CAP_MAP_COPY;
}
@@ -941,6 +933,20 @@ static int validate_mmap_request(struct file *file,
capabilities &= ~BDI_CAP_MAP_DIRECT;
}
+ if (capabilities & BDI_CAP_MAP_DIRECT) {
+ if (((prot & PROT_READ) && !(capabilities & BDI_CAP_READ_MAP)) ||
+ ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) ||
+ ((prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP))
+ ) {
+ capabilities &= ~BDI_CAP_MAP_DIRECT;
+ if (flags & MAP_SHARED) {
+ printk(KERN_WARNING
+ "MAP_SHARED not completely supported on !MMU\n");
+ return -EINVAL;
+ }
+ }
+ }
+
/* handle executable mappings and implied executable
* mappings */
if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
@@ -996,22 +1002,20 @@ static unsigned long determine_vm_flags(struct file *file,
unsigned long vm_flags;
vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags);
- vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
/* vm_flags |= mm->def_flags; */
if (!(capabilities & BDI_CAP_MAP_DIRECT)) {
/* attempt to share read-only copies of mapped file chunks */
+ vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
if (file && !(prot & PROT_WRITE))
vm_flags |= VM_MAYSHARE;
- }
- else {
+ } else {
/* overlay a shareable mapping on the backing device or inode
* if possible - used for chardevs, ramfs/tmpfs/shmfs and
* romfs/cramfs */
+ vm_flags |= VM_MAYSHARE | (capabilities & BDI_CAP_VMFLAGS);
if (flags & MAP_SHARED)
- vm_flags |= VM_MAYSHARE | VM_SHARED;
- else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0)
- vm_flags |= VM_MAYSHARE;
+ vm_flags |= VM_SHARED;
}
/* refuse to let anyone share private mappings with this process if