Change the kernel to add features to vircopy and safecopies so that
transparent copy fixing won't happen to avoid deadlocks, and such copies
fail with EFAULT.
Transparently making copying work from filesystems (as normally done by
the kernel & VM when copying fails because of missing/readonly memory)
is problematic as it can happen that, for file-mapped ranges, that that
same filesystem that is blocked on the copy request is needed to satisfy
the memory range, leading to deadlock. Dito for VFS itself, if done with
a blocking call.
This change makes the copying done from a filesystem fail in such cases
with EFAULT by VFS adding the CPF_TRY flag to the grants. If a FS call
fails with EFAULT, VFS will then request the range to be made available
to VM after the FS is unblocked, allowing it to be used to satisfy the
range if need be in another VFS thread.
Similarly, for datacopies that VFS itself does, it uses the failable
vircopy variant and callers use a wrapper that talk to VM if necessary
to get the copy to work.
. kernel: add CPF_TRY flag to safecopies
. kernel: only request writable ranges to VM for the
target buffer when copying fails
. do copying in VFS TRY-first
. some fixes in VM to build SANITYCHECK mode
. add regression test for the cases where
- a FS system call needs memory mapped in a process that the
FS itself must map.
- such a range covers more than one file-mapped region.
. add 'try' mode to vircopy, physcopy
. add flags field to copy kernel call messages
. if CP_FLAG_TRY is set, do not transparently try
to fix memory ranges
. for use by VFS when accessing user buffers to avoid
deadlock
. remove some obsolete backwards compatability assignments
. VFS: let thread scheduling work for VM requests too
Allows VFS to make calls to VM while suspending and resuming
the currently running thread. Does currently not work for the
main thread.
. VM: add fix memory range call for use by VFS
Change-Id: I295794269cea51a3163519a9cfe5901301d90b32
This allows us to write things like this:
message m;
m.m_notify.interrupts = new_value;
or
message *mp;
mp->m_notify.interrupts = new_value;
The shorthands macro have been adapted for the new scheme, and will be
kept as long as we have generic messages being used.
Change-Id: Icfd02b5f126892b1d5d2cebe8c8fb02b180000f7
* Also change _orig to _intr for clarity
* Cleaned up {IPC,KER}VEC
* Renamed _minix_kernel_info_struct to get_minix_kerninfo
* Merged _senda.S into _ipc.S
* Moved into separate files get_minix_kerninfo and _do_kernel_call
* Adapted do_kernel_call to follow same _ convention as ipc functions
* Drop patches in libc/net/send.c and libc/include/namespace.h
Change-Id: If4ea21ecb65435170d7d87de6c826328e84c18d0
- introduce new call numbers, names, and field aliases;
- initialize request messages to zero for all ABI calls;
- format callnr.h in the same way as com.h;
- redo call tables in both servers;
- remove param.h namespace pollution in the servers;
- make brk(2) go to VM directly, rather than through PM;
- remove obsolete BRK, UTIME, and WAIT calls;
- clean up path copying routine in VFS;
- move remaining system calls from libminlib to libc;
- correct some errno-related mistakes in libc routines.
Change-Id: I2d8ec5d061cd7e0b30c51ffd77aa72ebf84e2565
There is no need to pass pointers around when there is a structure
available that already stores other similar state, such as m_in.
Change-Id: I3164c5c55c71f443688103d1f0756c086eb05974
These calls are sent to VFS, and thus should be prefixed with VFS_.
Clean up the protocol and PM's main function a bit.
Since the protocol is substantially big and different from normal VFS
requests, this protocol retains its own numbering range for now.
Change-Id: Ia62104b5c5c929ed787144816d2e4cc70bed3b0b
The getsysinfo(2), getrusage(2), and svrctl(2) calls used the same
call number to different services. Since we want to give each service
its own call number ranges, this is no longer tenable. This patch
introduces per-service call numbers for these calls.
Note that the remainder of the COMMON_ range is left intact, as these
the remaining requests in it are processed by SEF and thus server-
agnostic. The range should really be prefixed with SEF_ now.
Change-Id: I80d728bbeb98227359c525494c433965b40fefc3
- all TTY-related exceptions have now been merged into the regular
code paths, allowing non-TTY drivers to expose TTY-like devices;
- as part of this, CTTY_MAJOR is now fully managed by VFS instead of
being an ugly stepchild of the TTY driver;
- device styles have become completely obsolete, support for them has
been removed throughout the system; same for device flags, which had
already become useless a while ago;
- device map open/close and I/O function pointers have lost their use,
thus finally making the VFS device code actually readable;
- the device-unrelated pm_setsid has been moved to misc.c;
- some other small cleanup-related changes.
Change-Id: If90b10d1818e98a12139da3e94a15d250c9933da
This commit separates the low-level keyboard driver from TTY, putting
it in a separate driver (PCKBD). The commit also separates management
of raw input devices from TTY, and puts it in a separate server
(INPUT). All keyboard and mouse input from hardware is sent by drivers
to the INPUT server, which either sends it to a process that has
opened a raw input device, or otherwise forwards it to TTY for
standard processing.
Design by Dirk Vogt. Prototype by Uli Kastlunger.
Additional changes made to the prototype:
- the event communication is now based on USB HID codes; all input
drivers have to use USB codes to describe events;
- all TTY keymaps have been converted to USB format, with the effect
that a single keymap covers all keys; there is no (static) escaped
keymap anymore;
- further keymap tweaks now allow remapping of literally all keys;
- input device renumbering and protocol rewrite;
- INPUT server rewrite, with added support for cancel and select;
- PCKBD reimplementation, including PC/AT-to-USB translation;
- support for manipulating keyboard LEDs has been added;
- keyboard and mouse multiplexer devices have been added to INPUT,
primarily so that an X server need only open two devices;
- a new "libinputdriver" library abstracts away protocol details from
input drivers, and should be used by all future input drivers;
- both INPUT and PCKBD can be restarted;
- TTY is now scheduled by KERNEL, so that it won't be punished for
running a lot; without this, simply running "yes" on the console
kills the system;
- the KIOCBELL IOCTL has been moved to /dev/console;
- support for the SCANCODES termios setting has been removed;
- obsolete keymap compression has been removed;
- the obsolete Olivetti M24 keymap has been removed.
Change-Id: I3a672fb8c4fd566734e4b46d3994b4b7fc96d578
Previously, VFS would reopen a character device after a driver crash
if the associated file descriptor was opened with the O_REOPEN flag.
This patch removes support for this feature. The code was complex,
full of uncovered corner cases, and hard to test. Moreover, it did not
actually hide the crash from user applications: they would get an
error code to indicate that something went wrong, and have to decide
based on the nature of the underlying device how to continue.
- remove support for O_REOPEN, and make playwave(1) reopen its device;
- remove support for the DEV_REOPEN protocol message;
- remove all code in VFS related to reopening character devices;
- no longer change VFS filp reference count and FD bitmap upon filp
invalidation; instead, make get_filp* fail all calls on invalidated
FDs except when obtained with the locktype VNODE_OPCL which is used
by close_fd only;
- remove the VFS fproc file descriptor bitmap entirely, returning to
the situation that a FD is in use if its slot points to a filp; use
FILP_CLOSED as single means of marking a filp as invalidated.
Change-Id: I34f6bc69a036b3a8fc667c1f80435ff3af56558f
- prefix them with VFS_ as they are going to VFS;
- give these calls normal call numbers;
- give them their own set of message field aliases;
- also make do_mapdriver a regular call.
Change-Id: I2140439f288b06d699a1f65438bd8306509b259e
The main purpose of this patch is to fix handling of unpause calls
from PM while another call is ongoing. The solution to this problem
sparked a full revision of the threading model, consisting of a large
number of related changes:
- all active worker threads are now always associated with a process,
and every process has at most one active thread working for it;
- the process lock is always held by a process's worker thread;
- a process can now have both normal work and postponed PM work
associated to it;
- timer expiry and non-postponed PM work is done from the main thread;
- filp garbage collection is done from a thread associated with VFS;
- reboot calls from PM are now done from a thread associated with PM;
- the DS events handler is protected from starting multiple threads;
- support for a system worker thread has been removed;
- the deadlock recovery thread has been replaced by a parameter to the
worker_start() function; the number of worker threads has
consequently been increased by one;
- saving and restoring of global but per-thread variables is now
centralized in worker_suspend() and worker_resume(); err_code is now
saved and restored in all cases;
- the concept of jobs has been removed, and job_m_in now points to a
message stored in the worker thread structure instead;
- the PM lock has been removed;
- the separate exec lock has been replaced by a lock on the VM
process, which was already being locked for exec calls anyway;
- PM_UNPAUSE is now processed as a postponed PM request, from a thread
associated with the target process;
- the FP_DROP_WORK flag has been removed, since it is no longer more
than just an optimization and only applied to processes operating on
a pipe when getting killed;
- assignment to "fp" now takes place only when obtaining new work in
the main thread or a worker thread, when resuming execution of a
thread, and in the special case of exiting processes during reboot;
- there are no longer special cases where the yield() call is used to
force a thread to run.
Change-Id: I7a97b9b95c2450454a9b5318dfa0e6150d4e6858
The T_DUMPCORE implementation was not only broken - it would currently
produce a coredump of the tracer process rather than the traced
process - but also deeply flawed, and fixing it would require serious
alteration of PM's internal state machine. It should be possible to
implement the same functionality in userland, and that is now the
suggested way forward. For now, also remove the (identical) utilities
using T_DUMPCORE: dumpcore(1) and gcore(1).
Change-Id: I1d51be19c739362b8a5833de949b76382a1edbcc
Previously, processing of some replies coming from character drivers
could block on locks, and therefore, such processing was done from
threads that were associated to the character driver process. The
hidden consequence of this was that if all threads were in use, VFS
could drop replies coming from the driver. This patch returns VFS to
a situation where the replies from character drivers are processed
instantly from the main thread, by removing the situations that may
cause VFS to block while handling those replies.
- change the locking model for select, so that it will never block
on any processing that happens after the select call has been set
up, in particular processing of character driver select replies;
- clearly mark all select routines that may never block;
- protect against race conditions in do_select as result of the
locking that still does happen there (as is required for pipes);
- also handle select timers from the main thread;
- move processing of character driver replies into device.c.
Change-Id: I4dc8e69f265cbd178de0fbf321d35f58f067cc57
- change all sync char drivers into async drivers;
- retire support for the sync protocol in libchardev;
- remove async dev style, as this is now the default;
- remove dev_status from VFS;
- clean up now-unused protocol messages.
Change-Id: I6aacff712292f6b29f2ccd51bc1e7d7003723e87
* Removed startup code patches in lib/csu regarding kernel to userland
ABI.
* Aligned stack layout on NetBSD stack layout.
* Generate valid stack pointers instead of offsets by taking into account
_minix_kerninfo->kinfo->user_sp.
* Refactored stack generation, by moving part of execve in two
functions {minix_stack_params(), minix_stack_fill()} and using them
in execve(), rs and vm.
* Changed load offset of rtld (ld.so) to:
execi.args.stack_high - execi.args.stack_size - 0xa00000
which is 10MB below the main executable stack.
Change-Id: I839daf3de43321cded44105634102d419cb36cec
- pass in file system type through mount(2), and return this type in
statvfs structures as generated by [f]statvfs(2);
- align mount flags field with NetBSD's, splitting out service flags
which are not to be passed to VFS;
- remove limitation of mount ABI to 16-byte labels, so that labels
can be made larger in the future;
- introduce new m11 message union type for mount(2) as side effect.
Change-Id: I88b7710e297e00a5e4582ada5243d3d5c2801fd9
m_out is shared between threads as the reply message, and it can happen
results get overwritten by another thread before the reply is sent. This
change
. makes m_out local to the message handling function,
declared on the stack of the caller
. forces callers of reply() to give it a message, or
declare the reply message has no significant fields except
for the return code by calling replycode()
Change-Id: Id06300083a63c72c00f34f86a5c7d96e4bbdf9f6
There is a deadlock vulnerability when there are no worker threads
available and all of them blocked on a worker thread that's waiting for a
reply from a driver or a reply from an FS that needs to make a back call. In
these cases the deadlock resolver thread should kick in, but didn't in all
cases. Moreover, POSIX calls from File Servers weren't handled properly
anymore, which also could lead to deadlocks.
By decoupling synchronous drivers from VFS, we are a big step closer to
supporting driver crashes under all circumstances. That is, VFS can't
become stuck on IPC with a synchronous driver (e.g., INET) and can
recover from crashing block drivers during open/close/ioctl or during
communication with an FS.
In order to maintain serialized communication with a synchronous driver,
the communication is wrapped by a mutex on a per driver basis (not major
numbers as there can be multiple majors with identical endpoints). Majors
that share a driver endpoint point to a single mutex object.
In order to support crashes from block drivers, the file reopen tactic
had to be changed; first reopen files associated with the crashed
driver, then send the new driver endpoint to FSes. This solves a
deadlock between the FS and the block driver;
- VFS would send REQ_NEW_DRIVER to an FS, but he FS only receives it
after retrying the current request to the newly started driver.
- The block driver would refuse the retried request until all files
had been reopened.
- VFS would reopen files only after getting a reply from the initial
REQ_NEW_DRIVER.
When a character special driver crashes, all associated files have to
be marked invalid and closed (or reopened if flagged as such). However,
they can only be closed if a thread holds exclusive access to it. To
obtain exclusive access, the worker thread (which handles the new driver
endpoint event from DS) schedules a new job to garbage collect invalid
files. This way, we can signal the worker thread that was talking to the
crashed driver and will release exclusive access to a file associated
with the crashed driver and prevent the garbage collecting worker thread
from dead locking on that file.
Also, when a character special driver crashes, RS will unmap the driver
and remap it upon restart. During unmapping, associated files are marked
invalid instead of waiting for an endpoint up event from DS, as that
event might come later than new read/write/select requests and thus
cause confusion in the freshly started driver.
When locking a filp, the usage counters are no longer checked. The usage
counter can legally go down to zero during filp invalidation while there
are locks pending.
DS events are handled by a separate worker thread instead of the main
thread as reopening files could lead to another crash and a stuck thread.
An additional worker thread is then necessary to unlock it.
Finally, with everything asynchronous a race condition in do_select
surfaced. A select entry was only marked in use after succesfully sending
initial select requests to drivers and having to wait. When multiple
select() calls were handled there was opportunity that these entries
were overwritten. This had as effect that some select results were
ignored (and select() remained blocking instead if returning) or do_select
tried to access filps that were not present (because thrown away by
secondary select()). This bug manifested itself with sendrecs, but was
very hard to reproduce. However, it became awfully easy to trigger with
asynsends only.
This commit removes all traces of Minix segments (the text/data/stack
memory map abstraction in the kernel) and significance of Intel segments
(hardware segments like CS, DS that add offsets to all addressing before
page table translation). This ultimately simplifies the memory layout
and addressing and makes the same layout possible on non-Intel
architectures.
There are only two types of addresses in the world now: virtual
and physical; even the kernel and processes have the same virtual
address space. Kernel and user processes can be distinguished at a
glance as processes won't use 0xF0000000 and above.
No static pre-allocated memory sizes exist any more.
Changes to booting:
. The pre_init.c leaves the kernel and modules exactly as
they were left by the bootloader in physical memory
. The kernel starts running using physical addressing,
loaded at a fixed location given in its linker script by the
bootloader. All code and data in this phase are linked to
this fixed low location.
. It makes a bootstrap pagetable to map itself to a
fixed high location (also in linker script) and jumps to
the high address. All code and data then use this high addressing.
. All code/data symbols linked at the low addresses is prefixed by
an objcopy step with __k_unpaged_*, so that that code cannot
reference highly-linked symbols (which aren't valid yet) or vice
versa (symbols that aren't valid any more).
. The two addressing modes are separated in the linker script by
collecting the unpaged_*.o objects and linking them with low
addresses, and linking the rest high. Some objects are linked
twice, once low and once high.
. The bootstrap phase passes a lot of information (e.g. free memory
list, physical location of the modules, etc.) using the kinfo
struct.
. After this bootstrap the low-linked part is freed.
. The kernel maps in VM into the bootstrap page table so that VM can
begin executing. Its first job is to make page tables for all other
boot processes. So VM runs before RS, and RS gets a fully dynamic,
VM-managed address space. VM gets its privilege info from RS as usual
but that happens after RS starts running.
. Both the kernel loading VM and VM organizing boot processes happen
using the libexec logic. This removes the last reason for VM to
still know much about exec() and vm/exec.c is gone.
Further Implementation:
. All segments are based at 0 and have a 4 GB limit.
. The kernel is mapped in at the top of the virtual address
space so as not to constrain the user processes.
. Processes do not use segments from the LDT at all; there are
no segments in the LDT any more, so no LLDT is needed.
. The Minix segments T/D/S are gone and so none of the
user-space or in-kernel copy functions use them. The copy
functions use a process endpoint of NONE to realize it's
a physical address, virtual otherwise.
. The umap call only makes sense to translate a virtual address
to a physical address now.
. Segments-related calls like newmap and alloc_segments are gone.
. All segments-related translation in VM is gone (vir2map etc).
. Initialization in VM is simpler as no moving around is necessary.
. VM and all other boot processes can be linked wherever they wish
and will be mapped in at the right location by the kernel and VM
respectively.
Other changes:
. The multiboot code is less special: it does not use mb_print
for its diagnostics any more but uses printf() as normal, saving
the output into the diagnostics buffer, only printing to the
screen using the direct print functions if a panic() occurs.
. The multiboot code uses the flexible 'free memory map list'
style to receive the list of free memory if available.
. The kernel determines the memory layout of the processes to
a degree: it tells VM where the kernel starts and ends and
where the kernel wants the top of the process to be. VM then
uses this entire range, i.e. the stack is right at the top,
and mmap()ped bits of memory are placed below that downwards,
and the break grows upwards.
Other Consequences:
. Every process gets its own page table as address spaces
can't be separated any more by segments.
. As all segments are 0-based, there is no distinction between
virtual and linear addresses, nor between userspace and
kernel addresses.
. Less work is done when context switching, leading to a net
performance increase. (8% faster on my machine for 'make servers'.)
. The layout and configuration of the GDT makes sysenter and syscall
possible.
. all invocations were S or D, so can safely be dropped
to prepare for the segmentless world
. still assign D to the SCP_SEG field in the message
to make previous kernels usable
. vfs: pass execname in aux vectors
. ld.elf_so: use this to expand $ORIGIN
. this requires the executable to reserve more
space at exec() calling time
. generalize libexec slightly to get some more necessary information
from ELF files, e.g. the interpreter
. execute dynamically linked executables when exec()ed by VFS
. switch to netbsd variant of elf32.h exclusively, solves some
conflicting headers
When running out of worker threads to handle device replies a dead
lock resolver thread is used. However, it was only used for FS
endpoints; it is now used for "system processes" (drivers and FS
endpoints). Also, drivers were marked as system process when they
were not "forced" to map (i.e., mapping was done before endpoint was
alive).
By making m_in job local (i.e., each job has its own copy of m_in instead
of refering to the global m_in) we don't have to store and restore m_in
on every thread yield. This reduces overhead. Moreover, remove the
assumption that m_in is preserved. Do_XXX functions have to copy the
system call parameters as soon as possible and only pass those copies to
other functions.
Furthermore, this patch cleans up some code and uses better types in a lot
of places.
Currently, all servers and drivers run as root as they are forks of
RS. srv_fork now tells PM with which credentials to run the resulting
fork. Subsequently, PM lets VFS now as well.
This patch also fixes the following bugs:
- RS doesn't initialize the setugid variable during exec, causing the
servers and drivers to run setuid rendering the srv_fork extension
useless.
- PM erroneously tells VFS to run processes setuid. This doesn't
actually lead to setuid processes as VFS sets {r,e}uid and {r,e}gid
properly before checking PM's approval.
This patch separates the character and block driver communication
protocols. The old character protocol remains the same, but a new
block protocol is introduced. The libdriver library is replaced by
two new libraries: libchardriver and libblockdriver. Their exposed
API, and drivers that use them, have been updated accordingly.
Together, libbdev and libblockdriver now completely abstract away
the message format used by the block protocol. As the memory driver
is both a character and a block device driver, it now implements its
own message loop.
The most important semantic change made to the block protocol is that
it is no longer possible to return both partial results and an error
for a single transfer. This simplifies the interaction between the
caller and the driver, as the I/O vector no longer needs to be copied
back. Also, drivers are now no longer supposed to decide based on the
layout of the I/O vector when a transfer should be cut short. Put
simply, transfers are now supposed to either succeed completely, or
result in an error.
After this patch, the state of the various pieces is as follows:
- block protocol: stable
- libbdev API: stable for synchronous communication
- libblockdriver API: needs slight revision (the drvlib/partition API
in particular; the threading API will also change shortly)
- character protocol: needs cleanup
- libchardriver API: needs cleanup accordingly
- driver restarts: largely unsupported until endpoint changes are
reintroduced
As a side effect, this patch eliminates several bugs, hacks, and gcc
-Wall and -W warnings all over the place. It probably introduces a
few new ones, too.
Update warning: this patch changes the protocol between MFS and disk
drivers, so in order to use old/new images, the MFS from the ramdisk
must be used to mount all file systems.
