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| author | Bernd Schmidt <bernds_cb1@t-online.de> | 2010-05-25 23:43:00 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-26 08:19:23 -0700 |
| commit | 3c7b204547bc3d342a4e31196fe14803581d279f (patch) | |
| tree | 87a3300d266eed413012efd0a985a72caad4a856 /mm | |
| parent | 0cae3457b1a6e88f31020272bcfd90c178716053 (diff) | |
| download | linux-3c7b204547bc3d342a4e31196fe14803581d279f.tar.gz linux-3c7b204547bc3d342a4e31196fe14803581d279f.tar.bz2 linux-3c7b204547bc3d342a4e31196fe14803581d279f.zip | |
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')
| -rw-r--r-- | mm/nommu.c | 32 |
1 files changed, 18 insertions, 14 deletions
diff --git a/mm/nommu.c b/mm/nommu.c index 63fa17d121f0..b76f3ee0abe0 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 |