When truncating inodes in the lower filesystem, eCryptfs directly
invoked vmtruncate(). As Christoph Hellwig pointed out, vmtruncate() is
a filesystem helper function, but filesystems may need to do more than
just a call to vmtruncate().
This patch moves the lower inode truncation out of ecryptfs_truncate()
and renames the function to truncate_upper(). truncate_upper() updates
an iattr for the lower inode to indicate if the lower inode needs to be
truncated upon return. ecryptfs_setattr() then calls notify_change(),
using the updated iattr for the lower inode, to complete the truncation.
For eCryptfs functions needing to truncate, ecryptfs_truncate() is
reintroduced as a simple way to truncate the upper inode to a specified
size and then truncate the lower inode accordingly.
https://bugs.launchpad.net/bugs/451368
Reported-by: Christoph Hellwig <hch@lst.de>
Acked-by: Dustin Kirkland <kirkland@canonical.com>
Cc: ecryptfs-devel@lists.launchpad.net
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
* 'for-linus' of git://oss.sgi.com/xfs/xfs:
xfs: xfs_swap_extents needs to handle dynamic fork offsets
xfs: fix missing error check in xfs_rtfree_range
xfs: fix stale inode flush avoidance
xfs: Remove inode iolock held check during allocation
xfs: reclaim all inodes by background tree walks
xfs: Avoid inodes in reclaim when flushing from inode cache
xfs: reclaim inodes under a write lock
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
do_add_mount() should sanitize mnt_flags
CIFS shouldn't make mountpoints shrinkable
mnt_flags fixes in do_remount()
attach_recursive_mnt() needs to hold vfsmount_lock over set_mnt_shared()
may_umount() needs namespace_sem
Fix configfs leak
Fix the -ESTALE handling in do_filp_open()
ecryptfs: Fix refcnt leak on ecryptfs_follow_link() error path
Fix ACC_MODE() for real
Unrot uml mconsole a bit
hppfs: handle ->put_link()
Kill 9p readlink()
fix autofs/afs/etc. magic mountpoint breakage
Fix a problem in NOMMU mmap with ramfs whereby a shared mmap can happen
over the end of a truncation. The problem is that
ramfs_nommu_check_mappings() checks that the reduced file size against the
VMA tree, but not the vm_region tree.
The following sequence of events can cause the problem:
fd = open("/tmp/x", O_RDWR|O_TRUNC|O_CREAT, 0600);
ftruncate(fd, 32 * 1024);
a = mmap(NULL, 32 * 1024, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
b = mmap(NULL, 16 * 1024, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
munmap(a, 32 * 1024);
ftruncate(fd, 16 * 1024);
c = mmap(NULL, 32 * 1024, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
Mapping 'a' creates a vm_region covering 32KB of the file. Mapping 'b'
sees that the vm_region from 'a' is covering the region it wants and so
shares it, pinning it in memory.
Mapping 'a' then goes away and the file is truncated to the end of VMA
'b'. However, the region allocated by 'a' is still in effect, and has
_not_ been reduced.
Mapping 'c' is then created, and because there's a vm_region covering the
desired region, get_unmapped_area() is _not_ called to repeat the check,
and the mapping is granted, even though the pages from the latter half of
the mapping have been discarded.
However:
d = mmap(NULL, 16 * 1024, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
Mapping 'd' should work, and should end up sharing the region allocated by
'a'.
To deal with this, we shrink the vm_region struct during the truncation,
lest do_mmap_pgoff() take it as licence to share the full region
automatically without calling the get_unmapped_area() file op again.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix the race between the truncation of a ramfs file and an attempt to make
a shared mmap of region of that file.
The problem is that do_mmap_pgoff() calls f_op->get_unmapped_area() to
verify that the file region is made of contiguous pages and to find its
base address - but there isn't any locking to guarantee this region until
vma_prio_tree_insert() is called by add_vma_to_mm().
Note that moving the functionality into f_op->mmap() doesn't help as that
is also called before vma_prio_tree_insert().
Instead make ramfs_nommu_check_mappings() grab nommu_region_sem whilst it
does its checks. This means that this function will wait whilst mmaps
take place.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
MNT_WRITE_HOLD shouldn't leak into new vfsmount and neither
should MNT_SHARED (the latter will be set properly, along with
the rest of shared-subtree data structures)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
inotify will WARN() if it finds that the idr and the fsnotify internals
somehow got out of sync. It was only supposed to do this once but due
to this stupid bug it would warn every single time a problem was
detected.
Signed-off-by: Eric Paris <eparis@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit 7e790dd5fc ("inotify: fix
error paths in inotify_update_watch") inotify changed the manor in which
it gave watch descriptors back to userspace. Previous to this commit
inotify acted like the following:
inotify_add_watch(X, Y, Z) = 1
inotify_rm_watch(X, 1);
inotify_add_watch(X, Y, Z) = 2
but after this patch inotify would return watch descriptors like so:
inotify_add_watch(X, Y, Z) = 1
inotify_rm_watch(X, 1);
inotify_add_watch(X, Y, Z) = 1
which I saw as equivalent to opening an fd where
open(file) = 1;
close(1);
open(file) = 1;
seemed perfectly reasonable. The issue is that quite a bit of userspace
apparently relies on the behavior in which watch descriptors will not be
quickly reused. KDE relies on it, I know some selinux packages rely on
it, and I have heard complaints from other random sources such as debian
bug 558981.
Although the man page implies what we do is ok, we broke userspace so
this patch almost reverts us to the old behavior. It is still slightly
racey and I have patches that would fix that, but they are rather large
and this will fix it for all real world cases. The race is as follows:
- task1 creates a watch and blocks in idr_new_watch() before it updates
the hint.
- task2 creates a watch and updates the hint.
- task1 updates the hint with it's older wd
- task removes the watch created by task2
- task adds a new watch and will reuse the wd originally given to task2
it requires moving some locking around the hint (last_wd) but this should
solve it for the real world and be -stable safe.
As a side effect this patch papers over a bug in the lib/idr code which
is causing a large number WARN's to pop on people's system and many
reports in kerneloops.org. I'm working on the root cause of that idr
bug seperately but this should make inotify immune to that issue.
Signed-off-by: Eric Paris <eparis@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When swapping extents, we can corrupt inodes by swapping data forks
that are in incompatible formats. This is caused by the two indoes
having different fork offsets due to the presence of an attribute
fork on an attr2 filesystem. xfs_fsr tries to be smart about
setting the fork offset, but the trick it plays only works on attr1
(old fixed format attribute fork) filesystems.
Changing the way xfs_fsr sets up the attribute fork will prevent
this situation from ever occurring, so in the kernel code we can get
by with a preventative fix - check that the data fork in the
defragmented inode is in a format valid for the inode it is being
swapped into. This will lead to files that will silently and
potentially repeatedly fail defragmentation, so issue a warning to
the log when this particular failure occurs to let us know that
xfs_fsr needs updating/fixing.
To help identify how to improve xfs_fsr to avoid this issue, add
trace points for the inodes being swapped so that we can determine
why the swap was rejected and to confirm that the code is making the
right decisions and modifications when swapping forks.
A further complication is even when the swap is allowed to proceed
when the fork offset is different between the two inodes then value
for the maximum number of extents the data fork can hold can be
wrong. Make sure these are also set correctly after the swap occurs.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
When xfs_rtfind_forw() returns an error, the block is returned
uninitialised. xfs_rtfree_range() is not checking the error return,
so could be using an uninitialised block number for modifying bitmap
summary info.
The problem was found by gcc when compiling the *userspace* libxfs
code - it is an copy of the kernel code with the exact same bug.
gcc gives an uninitialised variable warning on the userspace code
but not on the kernel code. You gotta love the consistency (Mmmm,
slightly chewy today!).
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Alex Elder <aelder@sgi.com>
When reclaiming stale inodes, we need to guarantee that inodes are
unpinned before returning with a "clean" status. If we don't we can
reclaim inodes that are pinned, leading to use after free in the
transaction subsystem as transactions complete.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
lockdep complains about a the lock not being initialised as we do an
ASSERT based check that the lock is not held before we initialise it
to catch inodes freed with the lock held.
lockdep does this check for us in the lock initialisation code, so
remove the ASSERT to stop the lockdep warning.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
We cannot do direct inode reclaim without taking the flush lock to
ensure that we do not reclaim an inode under IO. We check the inode
is clean before doing direct reclaim, but this is not good enough
because the inode flush code marks the inode clean once it has
copied the in-core dirty state to the backing buffer.
It is the flush lock that determines whether the inode is still
under IO, even though it is marked clean, and the inode is still
required at IO completion so we can't reclaim it even though it is
clean in core. Hence the requirement that we need to take the flush
lock even on clean inodes because this guarantees that the inode
writeback IO has completed and it is safe to reclaim the inode.
With delayed write inode flushing, we coul dend up waiting a long
time on the flush lock even for a clean inode. The background
reclaim already handles this efficiently, so avoid all the problems
by killing the direct reclaim path altogether.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
The reclaim code will handle flushing of dirty inodes before reclaim
occurs, so avoid them when determining whether an inode is a
candidate for flushing to disk when walking the radix trees. This
is based on a test patch from Christoph Hellwig.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
Make the inode tree reclaim walk exclusive to avoid races with
concurrent sync walkers and lookups. This is a version of a patch
posted by Christoph Hellwig that avoids all the code duplication.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
Instead of playing sick games with path saving, cleanups, just retry
the entire thing once with LOOKUP_REVAL added. Post-.34 we'll convert
all -ESTALE handling in there to that style, rather than playing with
many retry loops deep in the call chain.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
If ->follow_link handler return the error, it should decrement
nd->path refcnt. But, ecryptfs_follow_link() doesn't decrement.
This patch fix it by using usual nd_set_link() style error handling,
instead of playing with nd->path.
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
commit 5300990c03 had stepped on a rather
nasty mess: definitions of ACC_MODE used to be different. Fixed the
resulting breakage, converting them to variant that takes O_... value;
all callers have that and it actually simplifies life (see tomoyo part
of changes).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
For symlinks generic_readlink() will work just fine and for directories
we don't want ->readlink() at all.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
We end up trying to kfree() nd.last.name on open("/mnt/tmp", O_CREAT)
if /mnt/tmp is an autofs direct mount. The reason is that nd.last_type
is bogus here; we want LAST_BIND for everything of that kind and we
get LAST_NORM left over from finding parent directory.
So make sure that it *is* set properly; set to LAST_BIND before
doing ->follow_link() - for normal symlinks it will be changed
by __vfs_follow_link() and everything else needs it set that way.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
There are two copies of list_sort() in the tree already, one in the DRM
code, another in ubifs. Now XFS needs this as well. Create a generic
list_sort() function from the ubifs version and convert existing users
to it so we don't end up with yet another copy in the tree.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Acked-by: Artem Bityutskiy <dedekind@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for-linus' of git://oss.sgi.com/xfs/xfs:
xfs: Ensure we force all busy extents in range to disk
xfs: Don't flush stale inodes
xfs: fix timestamp handling in xfs_setattr
xfs: use DECLARE_EVENT_CLASS
* git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-2.6-fixes:
GFS2: Use MAX_LFS_FILESIZE for meta inode size
GFS2: Fix gfs2_xattr_acl_chmod()
GFS2: Fix locking bug in rename
GFS2: Ensure uptodate inode size when using O_APPEND
A long time ago we regarded zero page as file_rss and vm_normal_page
doesn't return NULL.
But now, we reinstated ZERO_PAGE and vm_normal_page's implementation can
return NULL in case of zero page. Also we don't count it with file_rss
any more.
Then, RSS and PSS can't be matched. For consistency, Let's ignore zero
page in smaps_pte_range.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: Matt Mackall <mpm@selenic.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit d899bf7b (procfs: provide stack information for threads) introduced
to show stack information in /proc/{pid}/status. But it cause large
performance regression. Unfortunately /proc/{pid}/status is used ps
command too and ps is one of most important component. Because both to
take mmap_sem and page table walk are heavily operation.
If many process run, the ps performance is,
[before d899bf7b]
% perf stat ps >/dev/null
Performance counter stats for 'ps':
4090.435806 task-clock-msecs # 0.032 CPUs
229 context-switches # 0.000 M/sec
0 CPU-migrations # 0.000 M/sec
234 page-faults # 0.000 M/sec
8587565207 cycles # 2099.425 M/sec
9866662403 instructions # 1.149 IPC
3789415411 cache-references # 926.409 M/sec
30419509 cache-misses # 7.437 M/sec
128.859521955 seconds time elapsed
[after d899bf7b]
% perf stat ps > /dev/null
Performance counter stats for 'ps':
4305.081146 task-clock-msecs # 0.028 CPUs
480 context-switches # 0.000 M/sec
2 CPU-migrations # 0.000 M/sec
237 page-faults # 0.000 M/sec
9021211334 cycles # 2095.480 M/sec
10605887536 instructions # 1.176 IPC
3612650999 cache-references # 839.160 M/sec
23917502 cache-misses # 5.556 M/sec
152.277819582 seconds time elapsed
Thus, this patch revert it. Fortunately /proc/{pid}/task/{tid}/smaps
provide almost same information. we can use it.
Commit d899bf7b introduced two features:
1) Add the annotattion of [thread stack: xxxx] mark to
/proc/{pid}/task/{tid}/maps.
2) Add StackUsage field to /proc/{pid}/status.
I only revert (2), because I haven't seen (1) cause regression.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit fd8fbfc1 modified the way we find amount of reserved space
belonging to an inode. The amount of reserved space is checked
from dquot_transfer and thus inode_reserved_space gets called
even for filesystems that don't provide get_reserved_space callback
which results in a BUG.
Fix the problem by checking get_reserved_space callback and return 0 if
the filesystem does not provide it.
CC: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Using ~0ULL was cauing sign issues in filemap_fdatawrite_range, so
use MAX_LFS_FILESIZE instead.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
When we search for and find a busy extent during allocation we
force the log out to ensure the extent free transaction is on
disk before the allocation transaction. The current implementation
has a subtle bug in it--it does not handle multiple overlapping
ranges.
That is, if we free lots of little extents into a single
contiguous extent, then allocate the contiguous extent, the busy
search code stops searching at the first extent it finds that
overlaps the allocated range. It then uses the commit LSN of the
transaction to force the log out to.
Unfortunately, the other busy ranges might have more recent
commit LSNs than the first busy extent that is found, and this
results in xfs_alloc_search_busy() returning before all the
extent free transactions are on disk for the range being
allocated. This can lead to potential metadata corruption or
stale data exposure after a crash because log replay won't replay
all the extent free transactions that cover the allocation range.
Modified-by: Alex Elder <aelder@sgi.com>
(Dropped the "found" argument from the xfs_alloc_busysearch trace
event.)
Signed-off-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
Because inodes remain in cache much longer than inode buffers do
under memory pressure, we can get the situation where we have
stale, dirty inodes being reclaimed but the backing storage has
been freed. Hence we should never, ever flush XFS_ISTALE inodes
to disk as there is no guarantee that the backing buffer is in
cache and still marked stale when the flush occurs.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Alex Elder <aelder@sgi.com>
We currently have some rather odd code in xfs_setattr for
updating the a/c/mtime timestamps:
- first we do a non-transaction update if all three are updated
together
- second we implicitly update the ctime for various changes
instead of relying on the ATTR_CTIME flag
- third we set the timestamps to the current time instead of the
arguments in the iattr structure in many cases.
This patch makes sure we update it in a consistent way:
- always transactional
- ctime is only updated if ATTR_CTIME is set or we do a size
update, which is a special case
- always to the times passed in from the caller instead of the
current time
The only non-size caller of xfs_setattr that doesn't come from
the VFS is updated to set ATTR_CTIME and pass in a valid ctime
value.
Reported-by: Eric Blake <ebb9@byu.net>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
Using DECLARE_EVENT_CLASS allows us to to use trace event code
instead of duplicating it in the binary. This was not available
before 2.6.33 so it had to be done as a separate step once the
prerequisite was merged.
This only requires changes to xfs_trace.h and the results are
rather impressive:
hch@brick:~/work/linux-2.6/obj-kvm$ size fs/xfs/xfs.o*
text data bss dec hex filename
607732 41884 3616 653232 9f7b0 fs/xfs/xfs.o
1026732 41884 3808 1072424 105d28 fs/xfs/xfs.o.old
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
* 'bugfixes' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6:
nfs: fix oops in nfs_rename()
sunrpc: fix build-time warning
sunrpc: on successful gss error pipe write, don't return error
SUNRPC: Fix the return value in gss_import_sec_context()
SUNRPC: Fix up an error return value in gss_import_sec_context_kerberos()
Randy Dunlap Reported printk() format-related warnings reported
on i386 builds in his environment. Dave Chinner provided this
patch to eliminate them.
Signed-off by: Dave Chinner <david@fromorbit.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Alex Elder <aelder@sgi.com>
The ref counting for the bh returned by gfs2_ea_find() was
wrong. This patch ensures that we always drop the ref count
to that bh correctly.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
The rename code was taking a resource group lock in cases where
it wasn't actually needed, this caused problems if the rename
was resulting in an inode being unlinked. The patch ensures that
we only take the rgrp lock early if it is really needed.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
The VFS reads the inode size during generic_file_aio_write() but
with no locking around it. In order to get the expected result
from O_APPEND opens, this patch updated the inode size before
calling generic_file_aio_write()
There is of course still a race here, in that there is nothing to
prevent another node coming in and extending the file in the
mean time. On the other hand, when used with file locking this
will ensure that the expected results are obtained.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Fix remaining xattr locks acquired in reiserfs_xattr_set_handle()
while we are holding the reiserfs lock to avoid lock inversions.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christian Kujau <lists@nerdbynature.de>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Stanse found an unreachable statement in reiserfs_ioctl. There is a
if followed by error assignment and `break' with no braces. Add the
braces so that we don't break every time, but only in error case,
so that REISERFS_IOC_SETVERSION actually works when it returns no
error.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Reiserfs <reiserfs-devel@vger.kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
reiserfs_get_acl is usually not called under the reiserfs lock,
as it doesn't need it. But it happens when it is called by
reiserfs_acl_chmod(), which creates a dependency inversion against
the private xattr inodes mutexes for the given inode.
We need to call it without the reiserfs lock, especially since
it's unnecessary.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christian Kujau <lists@nerdbynature.de>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
The current code will load the stack size and protection markings, but
then only use the markings in the MMU code path. The NOMMU code path
always passes PROT_EXEC to the mmap() call. While this doesn't matter
to most people whilst the code is running, it will cause a pointless
icache flush when starting every FDPIC application. Typically this
icache flush will be of a region on the order of 128KB in size, or may
be the entire icache, depending on the facilities available on the CPU.
In the case where the arch default behaviour seems to be desired
(EXSTACK_DEFAULT), we probe VM_STACK_FLAGS for VM_EXEC to determine
whether we should be setting PROT_EXEC or not.
For arches that support an MPU (Memory Protection Unit - an MMU without
the virtual mapping capability), setting PROT_EXEC or not will make an
important difference.
It should be noted that this change also affects the executability of
the brk region, since ELF-FDPIC has that share with the stack. However,
this is probably irrelevant as NOMMU programs aren't likely to use the
brk region, preferring instead allocation via mmap().
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
