This patch changes the prefetch API so that file systems must now
provide a set of block numbers, rather than a set of buffers. The
result is a leaner and more well-defined API; linear computation of
the range of blocks to prefetch; duplicates no longer interfering
with the prefetch process; guaranteed inclusion of the block needed
next into the prefetch range; and, limits and policy decisions better
established by libminixfs now actually being moved into libminixfs.
libminixfs: better support for read errors and EOF
- The lmfs_get_block*(3) API calls may now return an error. The idea
is to encourage a next generation of file system services to do a
better job at dealing with block read errors than the MFS-derived
implementations do. These existing file systems have been changed
to panic immediately upon getting a block read error, in order to
let unchecked errors cause corruption. Note that libbdev already
retries failing I/O operations a few times first.
- The libminixfs block device I/O module (bio.c) now deals properly
with end-of-file conditions on block devices. Since a device or
partition size may not be a multiple of the root file system's block
size, support for partial block retrival has been added, with a new
internal lmfs_get_partial_block(3) call. A new test program,
test85, tests the new handling of EOF conditions when reading,
writing, and memory-mapping a block device.
This patch changes the libminixfs API and implementation such that the
library is at all times aware of how many total and used blocks there
are in the file system. This removes the last upcall of libminixfs
into file systems (fs_blockstats). In the process, make this part of
the libminixfs API a little prettier and more robust. Change file
systems accordingly. Since this change only adds to MFS being unable
to deal with zones and blocks having different sizes, fail to mount
such file systems immediately rather than triggering an assert later.
This removes an implicit requirement for the way the libminixfs API is
to be used, namely that a block is to be marked as dirty only once its
contents have been fully updated, within a single get_block/put_block
window. The requirement may not be appropriate for all file systems.
With this change, the lmfs_get_block*(3) functions allow the caller to
specify that it only wants the block if it is in the cache or the
secondary VM cache. If the block is not found there, the functions
return NULL. Previously, the PREFETCH method would be used to this
end instead, which was both abuse in name and less efficient.
When VM asks a file system to provide a block to satisfy a page fault
on a file memory mapping, the file system previously had no way to
inform VM that the block is a hole, since there is no corresponding
block on the underlying device. To work around this, MFS and ext2
would actually allocate a block for the hole when asked by VM, which
not only defeats the point of holes in the first place, but also does
not work on read-only file systems. With this patch, a new libminixfs
call allows the file system to inform VM about holes. This issue does
raise the question as to whether the VM cache is using the right data
structures, since there are now two places where we have to fake a
device offset. This will have to be revisited in the future.
The patch changes file systems accordingly, and adds a test to test74.
This patch employs one solution to resolve two independent but related
issues. Both issues are the result of one fundamental aspect of the
way VM's memory mapping works: VM uses its cache to map in blocks for
memory-mapped file regions, and for blocks already in the VM cache, VM
does not go to the file system before mapping them in. To preserve
consistency between the FS and VM caches, VM relies on being informed
about all updates to file contents through the block cache. The two
issues are both the result of VM not being properly informed about
such updates:
1. Once a file system provides libminixfs with an inode association
(inode number + inode offset) for a disk block, this association
is not broken until a new inode association is provided for it.
If a block is freed and reallocated as a metadata (non-inode)
block, its old association is maintained, and may be supplied to
VM's secondary cache. Due to reuse of inodes, it is possible
that the same inode association becomes valid for an actual file
block again. In that case, when that new file is memory-mapped,
under certain circumstances, VM may end up using the metadata
block to satisfy a page fault on the file, due to the stale inode
association. The result is a corrupted memory mapping, with the
application seeing data other than the current file contents
mapped in at the file block.
2. When a hole is created in a file, the underlying block is freed
from the device, but VM is not informed of this update, and thus,
if VM's cache contains the block with its previous inode
association, this block will remain there. As a result, if an
application subsequently memory-maps the file, VM will map in the
old block at the position of the hole, rather than an all-zeroes
block. Thus, again, the result is a corrupted memory mapping.
This patch resolves both issues by making the file system inform the
minixfs library about blocks being freed, so that libminixfs can
break the inode association for that block, both in its own cache and
in the VM cache. Since libminixfs does not know whether VM has the
block in its cache or not, it makes a call to VM for each block being
freed. Thus, this change introduces more calls to VM, but it solves
the correctness issues at hand; optimizations may be introduced
later. On the upside, all freed blocks are now marked as clean,
which should result in fewer blocks being written back to the device,
and the blocks are removed from the caches entirely, which should
result in slightly better cache usage.
This patch is necessary but not sufficient to resolve the situation
with respect to memory mapping of file holes in general. Therefore,
this patch extends test 74 with a (rather particular but effective)
test for the first issue, but not yet with a test for the second one.
There is no reason to keep these tightly coupled data structures
separate. Moreover, there is no reason to have a union of file
descriptor and file pointer, since the second can be derived from
the first. The result are somewhat cleaner VFS internals.
If an asynchronous message is delivered during an ipc_receive(2) call,
but a failure occurred while copying out the status to the sending
process, then the receiving process would be left in an inconsistent
state, leading to a kernel crash shortly after.
For now, we fix this by altogether ignoring errors while copying out
the status field to the sending process. While this resolves the
kernel crash, it is hardly ideal, since it will likely cause the same
message to be delivered repeatedly. It would be better to disable
asynchronous communication from the sender process altogether, but this
solution requires more changes and thus more testing.
Previously, there was a tiny chance that tickdelay(3) would return
early or that it would fail to reinstate a previous alarm.
- sys_setalarm(2) now returns TMR_NEVER instead of 0 for the time
left if no previous alarm was set;
- sys_setalarm(2) now also returns the current time, to allow the
caller to determine whether it got an alarm notification for the
alarm it set or for a previous alarm that has just gone off;
- tickdelay(3) now makes use of these facilities.
The previous approach of including libraries through the parent
directory's Makefile.inc created linking issues, with libchardriver
not finding snprintf in certain cases. The new approach of including
libraries through the driver's only Makefile is the one used by all
other drivers.
This is the combination of two NetBSD patches committed by Christos
Zoulas, based on the findings and Bitrig patch by Martin Natano.
The NetBSD log messages read:
From Martin Natano @bitrig: Use execve(2) instead of system to
apply patches that require rcs command execution instead system(3)
to avoid malicious filenames in patches causing bad things to
happen. In the process, lose SCCS support. It is not like we are
shipping sccs commands for that to work.
And:
Use absolute paths for RCS commands (Martin Natano)
This test connects to a remote HTTP server to retrieve files, using various
chunk sizes and concurrency settings to exercise the network stack. The test
is only performed is USENETWORK=yes. This test requires the following URLs to
remain available: http://test82.minix3.org/test1.txt and
http://test82.minix3.org/test2.bin. The former contains a 'Hello world'
message followed by a newline, the latter all 16-bit values in increasing
order, using big-endian notation.
These new tests are largely based on the code from test 56 (UDS). Common code
is moved into a separate file common-socket.c. In some instances the tests
are too strict for TCP/UDP sockets, which may not always react instantly to
whatever happens on the other side (even locally). For these cases, the
ignore_* fields in struct socket_test_info indicate that there needs to be
an exception. There are also tests where it seems the functionality of inet
is either incorrect or incomplete with regard to the POSIX standard. In these
cases, the bug_* fields are used to document the issues while avoiding
failure of the test.
This patch introduces USENETWORK environment variable to determine whether to
use the network or not, instead of the unreliable ping test; set to 'yes' to
enable network usage.
Extended by David van Moolenbroek to continue using static buffers
for short inode names, so as to prevent important file system
services such as procfs from running out of memory at runtime.
Each /proc/service entry must have a unique label. With cloning,
multiple RS services may have the same label. Since we are not
actually interested in inactive services (for now), eliminate those
entries, leaving only the active service which will then indeed have
a unique label in the list. This resolves a procfs crash.
Previously, procfs would retrieve the rproc and rprocpub tables from
RS in two separate calls. This allowed for a race condition where the
tables could change in between the calls, resulting in a panic in
procfs under certain circumstances. RS now implements a new method
for getsysinfo that allows the retrieval of both tables at once.
This patch adds support for Unix98 pseudo terminals, that is,
posix_openpt(3), grantpt(3), unlockpt(3), /dev/ptmx, and /dev/pts/.
The latter is implemented with a new pseudo file system, PTYFS.
In effect, this patch adds secure support for unprivileged pseudo
terminal allocation, allowing programs such as tmux(1) to be used by
non-root users as well. Test77 has been extended with new tests, and
no longer needs to run as root.
The new functionality is optional. To revert to the old behavior,
remove the "ptyfs" entry from /etc/fstab.
Technical nodes:
o The reason for not implementing the NetBSD /dev/ptm approach is that
implementing the corresponding ioctl (TIOCPTMGET) would require
adding a number of extremely hairy exceptions to VFS, including the
PTY driver having to create new file descriptors for its own device
nodes.
o PTYFS is required for Unix98 PTYs in order to avoid that the PTY
driver has to be aware of old-style PTY naming schemes and even has
to call chmod(2) on a disk-backed file system. PTY cannot be its
own PTYFS since a character driver may currently not also be a file
system. However, PTYFS may be subsumed into a DEVFS in the future.
o The Unix98 PTY behavior differs somewhat from NetBSD's, in that
slave nodes are created on ptyfs only upon the first call to
grantpt(3). This approach obviates the need to revoke access as
part of the grantpt(3) call.
o Shutting down PTY may leave slave nodes on PTYFS, but once PTY is
restarted, these leftover slave nodes will be removed before they
create a security risk. Unmounting PTYFS will make existing PTY
slaves permanently unavailable, and absence of PTYFS will block
allocation of new Unix98 PTYs until PTYFS is (re)mounted.
As part of its built-in mmap emulation support for "none" file system
services, libfsdriver clears the VM cache upon exit. However, for
trivial file systems which do not even support reading from files, the
the VM cache need to be cleared either. With this patch, the VM cache
is cleared only when modified, so that such trivial file systems need
not be given CLEARCACHE permission.
While putnode requests should always succeed, very simple file system
services may not care about reference counts and thus about putnode
requests at all. For this reason, we now default to an OK response if
no fdr_putnode implementation is given.
The stat.st_ino field must always be filled with the inode number
given as part of the fdr_stat request anyway, so libfsdriver can
simply fill in the number and allow the file system not to bother.
Commit 723e513 erroneously removed a yield() call from VFS which was
necessary to get resumed pipe read/write threads to run before VFS
blocks on receive(). The removal caused those threads to run only
once VFS received another message, effectively slowing down activity
on pipes to a crawl in some cases.
Instead of readding the yield() call, this patch restructures the
get_work() code to go back through the main message loop even when no
new work is received, thus ensuring that newly started threads are
always activated without requiring a special case.
Previously, services would obtain the user ID of "service" through
getpwnam(3). While this approach is conceptually better, it also
imposes linking against libc which in turn causes problems with
printf(3), which already led to PFS no longer dropping privileges at
all. For now, we hardcode SERVICE_UID and use that instead.
In the future, two changes should allow removal of SERVICE_UID again:
- "service edit" should cause RS to request that a service (such as
PFS) drop privileges through SEF, using the user ID resolved by
service(8), or something similar;
- a future devfs should make it possible for inet to start without
root privileges altogether.
For VFS, initialization is a special case for processing work: PFS
and the ramdisk MFS must be fully mounted before VFS can process any
other requests, in particular from init(8). This case was handled by
receiving reply messages only from the FS service being mounted, but
this effectively disallowed PFS from calling setuid(2) at startup.
This patch lets VFS receive all messages during the mounting process,
but defer processing any new requests. As a result, the FS services
have a bit more freedom in what they can do during startup.
- If a large (>PIPE_BUF) pipe write is processed partially, only to be
followed by a write error condition, then the process is left in an
incorrect state, possibly causing VFS to crash on a subsequent call.
- If such a partially processed large pipe write ends up resulting in
an EPIPE error, no corresponding SIGPIPE signal is generated.
Thomas Cort [Wed, 25 Mar 2015 19:46:00 +0000 (15:46 -0400)]
mined: increase the size of the tgetent() buffer.
From the termcap section of the GNU termutils manual:
"There is no way you can tell how much space is needed, so the convention
is to allocate a buffer 2048 characters long and assume that is enough.
(Formerly the convention was to allocate 1024 characters and assume that
was enough. But one day, for one kind of terminal, that was not
enough.)"
Thomas Cort [Wed, 25 Mar 2015 18:48:08 +0000 (14:48 -0400)]
mined: remove !__STDC__ code blocks.
__STDC__ is used to mitigate the differences between K&R C and the
ANSI C standard. Nearly every compiler now supports ANSI C, so
there is no need to support non-standard compilers.
Thomas Cort [Wed, 25 Mar 2015 18:32:43 +0000 (14:32 -0400)]
mined: built without UNIX defined.
* Remove undef NULL, EOF, getchar, putchar
* Rename putchar, getchar, _putchar, _getchar to putch, getch, _putch,
_getch to avoid conflict with libc functions.
* Rename UP() to UP1() (for UP 1 line) to avoid conflict with UP
definition in termcap.h. Rename DN1 LF1 RT1 for consistency.
* Add termcap.h for prototypes for tputs and friends.
* Add libterminfo references to Makefile
* Add return value to _putch() to make it work as tputs expects.
* Make putch() call _putch()
* Remove UNIX ifdefs and all code in the !UNIX branches.
Thomas Cort [Sun, 22 Mar 2015 20:14:51 +0000 (16:14 -0400)]
mined1.c: remove i386 guard around escape sequences.
The escape sequences for the function keys used to be separated
out in older versions of Minix when they were different for m68k
and intel. Support for m68k was dropped and that code was
removed, leaving the ifdef i386. Since the sequences are the
same for i386 and arm, there is no need to keep the ifdef i386.
Thomas Cort [Sun, 22 Mar 2015 20:10:17 +0000 (16:10 -0400)]
mined.h: remove irrlevant comment.
It used to refer to several NIL_* definitions. Those were removed
in commit 6e25ad8b0a5606fc9351824adf9034d2ef7f7293 leaving the
comment with nothing to comment on.