It's now possible to block until another thread in the same process has
exited. We can also retrieve its exit value, which is whatever value it
passed to pthread_exit(). :^)
While executing in the kernel, a thread can acquire various resources
that need cleanup, such as locks and references to RefCounted objects.
This cleanup normally happens on the exit path, such as in destructors
for various RAII guards. But we weren't calling those exit paths when
killing threads that have been executing in the kernel, such as threads
blocked on reading or sleeping, thus causing leaks.
This commit changes how killing threads works. Now, instead of killing
a thread directly, one is supposed to call thread->set_should_die(),
which will unblock it and make it unwind the stack if it is blocked
in the kernel. Then, just before returning to the userspace, the thread
will automatically die.
This patch adds pthread_create() and pthread_exit(), which currently
simply wrap our existing create_thread() and exit_thread() syscalls.
LibThread is also ported to using LibPthread.
Some syscalls have to pass parameters through a struct, since we can
only fit 3 parameters with our calling convention.
This patch makes use of C++ structured binding to clean up the places
where we expand those parameters structs into local variables.
POSIX's openat() is very similar to open(), except you also provide a
file descriptor referring to a directory from which relative paths
should be resolved.
Passing it the magical fd number AT_FDCWD means "resolve from current
directory" (which is indeed also what open() normally does.)
This fixes libarchive's bsdtar, since it was trying to do something
extremely wrong in the absence of openat() support. The issue has
recently been fixed upstream in libarchive:
https://github.com/libarchive/libarchive/issues/1239
However, we should have openat() support anyway, so I went ahead and
implemented it. :^)
Fixes#748.
Don't wait for someone to wait() on a dead process before releasing its
TTY object. This fixes the child process death detection used by the
Terminal application, which relies on getting an EOF on the master PTY
in order to know it's time to wait() on the child process. :^)
Instead of the big ugly switch statement, build a lookup table using
the syscall enumeration macro.
This greatly simplifies the syscall implementation. :^)
Scheduling priority is now set at the thread level instead of at the
process level.
This is a step towards allowing processes to set different priorities
for threads. There's no userspace API for that yet, since only the main
thread's priority is affected by sched_setparam().
This patch changes the parameter to Region::map() to be a PageDirectory
since that matches how we think about the memory model:
Regions are views onto VMObjects, and are mapped into PageDirectories.
Each Process has a PageDirectory. The kernel also has a PageDirectory.
Add the ability to both pass arguments to scripts with shebangs
(./script argument1 argument2) and to specify them in the shebang line
(#!/usr/local/bin/bash -x -e)
Fixes#585
We now return EISDIR whenever a program attempts to call sys$read
on a directory. Previously, attempting to read a directory could
either return junk data or, in the case of /proc/, cause a kernel
panic.
Thread::make_userspace_stack_for_main_thread is only ever called from
Process::do_exec, after all the fun ELF loading and TSS setup has
occured.
The calculations in there that check if the combined argv + envp
size will exceed the default stack size are not used in the rest of
the stack setup. So, it should be safe to move this to the beginning
of do_exec and bail early with -E2BIG, just like the man pages say.
Additionally, advertise this limit in limits.h to be a good POSIX.1
citizen. :)
ELFLoader::layout() had a "failed" variable that was never set. This
patch checks the return value of each hook (alloc/map section and tls)
and fails the load if they return null.
I also needed to patch Process so that the alloc_section_hook and
map_section_hook actually return nullptr when allocating a region fails.
Fixes#664 :)
The way it gets the entropy and blasts it to the buffer is pretty
ugly IMHO, but it does work for now. (It should be replaced, by
not truncating a u32.)
It implements an (unused for now) flags argument, like Linux but
instead of OpenBSD's. This is in case we want to distinguish
between entropy sources or any other reason and have to implement
a new syscall later. Of course, learn from Linux's struggles with
entropy sourcing too.
Make sure we don't move accepted sockets to the Completed setup state
until we've actually constructed a FileDescription for them.
This is important, since this state transition will trigger connect()
to unblock on the client side, and the client may try writing to the
socket right away.
This makes DNS lookups way more reliable since we don't just fail to
write() right after connect()ing to LookupServer sometimes. :^)
Added the exception_code field to RegisterDump, removing the need
for RegisterDumpWithExceptionCode. To accomplish this, I had to
push a dummy exception code during some interrupt entries to properly
pad out the RegisterDump. Note that we also needed to change some code
in sys$sigreturn to deal with the new RegisterDump layout.
When splitting an Region that's already the result of an earlier split,
we have to take the Region's offset-in-VMObject into account since it
may be non-zero.
We were always returning the full VM range of the partially-unmapped
Region to the range allocator. This caused us to re-use those addresses
for subsequent VM allocations.
This patch also skips creating a new VMObject in partial munmap().
Instead we just make split regions that point into the same VMObject.
This fixes the mysterious GCC ICE on large C++ programs.
This simplifies the ownership model and makes Region easier to reason
about. Userspace Regions are now primarily kept by Process::m_regions.
Kernel Regions are kept in various OwnPtr<Regions>'s.
Regions now only ever get unmapped when they are destroyed.
We now no longer hardcode the sigreturn syscall in
the signal trampoline. Because of the way inline asm inputs
work, I've had to enclose the trampoline in the function
signal_trampoline_dummy.
This patch makes it possible to *run* text files that start with the
characters "#!" followed by an interpreter.
I've tested this with both the Serenity built-in shell and the Bash
shell, and it works as expected. :^)
The fchdir() function is equivalent to chdir() except that the
directory that is to be the new current working directory is
specified by a file descriptor.
Due to the changes in signal handling m_kernel_stack_for_signal_handler_region
and m_signal_stack_user_region are no longer necessary, and so, have been
removed. I've also removed the similarly reduntant m_tss_to_resume_kernel.
This patch adds support for TLS according to the x86 System V ABI.
Each thread gets a thread-specific memory region, and the GS segment
register always points _to a pointer_ to the thread-specific memory.
In other words, to access thread-local variables, userspace programs
start by dereferencing the pointer at [gs:0].
The Process keeps a master copy of the TLS segment that new threads
should use, and when a new thread is created, they get a copy of it.
It's basically whatever the PT_TLS program header in the ELF says.
This commit drastically changes how signals are handled.
In the case that an unblocked thread is signaled it works much
in the same way as previously. However, when a blocking syscall
is interrupted, we set up the signal trampoline on the user
stack, complete the blocking syscall, return down the kernel
stack and then jump to the handler. This means that from the
kernel stack's perspective, we only ever get one system call deep.
The signal trampoline has also been changed in order to properly
store the return value from system calls. This is necessary due
to the new way we exit from signaled system calls.
You can now munmap() a part of a region. The kernel will then create
one or two new regions around the "hole" and re-map them using the same
physical pages as before.
This goes towards fixing #175, but not all the way since we don't yet
do munmap() across multiple mappings.
We were doing this for the initial kernel-spawned userspace process(es)
to work around instability in the page fault handler. Now that the page
fault handler is more robust, we can stop worrying about this.
Specifically, the page fault handler was previous not able to handle
getting a page fault in anything but the currently executing task's
page directory.
It is now possible to unmount file systems from the VFS via `umount`.
It works via looking up the `fsid` of the filesystem from the `Inode`'s
metatdata so I'm not sure how fragile it is. It seems to work for now
though as something to get us going.
We were forced to do this because the page fault code would fall apart
when trying to generate a backtrace for a non-current thread.
This issue has been fixed for a while now, so let's go back to lazily
loading executable pages which should make everything a little better.
This patch adds the mprotect() syscall to allow changing the protection
flags for memory regions. We don't do any region splitting/merging yet,
so this only works on whole mmap() regions.
Added a "crash -r" flag to verify that we crash when you attempt to
write to read-only memory. :^)
This is more logical and allows us to solve the problem of
non-blocking TCP sockets getting stuck in SocketRole::None.
The only complication is that a single LocalSocket may be shared
between two file descriptions (on the connect and accept sides),
and should have two different roles depending from which side
you look at it. To deal with it, Socket::role() is made a
virtual method that accepts a file description, and LocalSocket
internally tracks which FileDescription is the which one and
returns a correct role.
After a fork, the parent and the child are supposed to share
the same file description. For example, modifying the current
offset of a file description is visible in both of them.
We were only doing this in Process::deallocate_region(), which meant
that kernel-only Regions never gave back their VM.
With this patch, we can start reusing freed-up address space! :^)
This is not perfect as it uses a lot of VM, but since the buffers are
supposed to be temporary it's not super terrible.
This could be improved by giving back the unused VM to the kernel's
RangeAllocator after finishing the buffer building.
InodeVMObject is a VMObject with an underlying Inode in the filesystem.
AnonymousVMObject has no Inode.
I'm happy that InodeVMObject::inode() can now return Inode& instead of
VMObject::inode() return Inode*. :^)
The VMObject name was always either the owning region's name, or the
absolute path of the underlying inode.
We can reconstitute this information if wanted, no need to keep copies
of these strings around.
This allows the page fault code to find the owning PageDirectory and
corresponding process for faulting regions.
The mapping is implemented as a global hash map right now, which is
definitely not optimal. We can come up with something better when it
becomes necessary.
In the userspace, this mimics the Linux pipe2() syscall;
in the kernel, the Process::sys$pipe() now always accepts
a flags argument, the no-argument pipe() syscall is now a
userspace wrapper over pipe2().
In the future, we should allow mounting any block device. At the moment
there is too much filesystem code that depends on the underlying device
being a DiskDevice.
- You must now have superuser privileges to use mount().
- We now verify that the mount point is a valid path first, before
trying to find a filesystem on the specified device.
- Convert some dbgprintf() to dbg().
It is now possible to mount ext2 `DiskDevice` devices under Serenity on
any folder in the root filesystem. Currently any user can do this with
any permissions. There's a fair amount of assumptions made here too,
that might not be too good, but can be worked on in the future. This is
a good start to allow more dynamic operation under the OS itself.
It is also currently impossible to unmount and such, and devices will
fail to mount in Linux as the FS 'needs to be cleaned'. I'll work on
getting `umount` done ASAP to rectify this (as well as working on less
assumption-making in the mount syscall. We don't want to just be able
to mount DiskDevices!). This could probably be fixed with some `-t`
flag or something similar.
Processes can now have an icon assigned, which is essentially a 16x16 RGBA32
bitmap exposed as a shared buffer ID.
You set the icon ID by calling set_process_icon(int) and the icon ID will be
exposed through /proc/all.
To make this work, I added a mechanism for making shared buffers globally
accessible. For safety reasons, each app seals the icon buffer before making
it global.
Right now the first call to GWindow::set_icon() is what determines the
process icon. We'll probably change this in the future. :^)
This is expensive because we have to page in the entire executable for every
process up front for this to work. This is due to the page fault code not
being strong enough to run while another process is active.
Note that we already had userspace symbols in *crash* stacks. This patch
adds them generally, so they show up in /proc, Process Manager, etc.
There's room for improvement here, but the debugging benefits way overshadow
the performance penalty right now. :^)
This makes assertion failures generate backtraces again. Sorry to everyone
who suffered from the lack of backtraces lately. :^)
We share code with the /proc/PID/stack implementation. You can now get the
current backtrace for a Thread via Thread::backtrace(), and all the traces
for a Process via Process::backtrace().
The syscall is quite simple:
int watch_file(const char* path, int path_length);
It returns a file descriptor referring to a "InodeWatcher" object in the
kernel. It becomes readable whenever something changes about the inode.
Currently this is implemented by hooking the "metadata dirty bit" in
Inode which isn't perfect, but it's a start. :^)
The "stddbg" stream was a cute idea but we never ended up using it in
practice, so let's simplify this and implement userspace dbgprintf() on top
of a simple dbgputch() syscall instead.
This makes debugging LibC startup a little bit easier. :^)
This is very simple but already very useful. Now you're able to call to
dump_backtrace() from anywhere userspace to get a nice symbolicated
backtrace in the debugger output. :^)
And use this to return EINTR in various places; some of which we were
not handling properly before.
This might expose a few bugs in userspace, but should be more compatible
with other POSIX systems, and is certainly a little cleaner.
It's a very bad idea to increment the refcount on behalf of another
process. That process may (for either benign or evil reasons) not
reference the SharedBuffer, and then we'll be stuck with loads of
SharedBuffers until we OOM.
Instead, increment the refcount when the buffer is mapped. That way, a
buffer is only kept if *someone* has explicitly requested it via
get_shared_buffer.
Fixes#341
Generate a special page containing the "return from signal" trampoline code
on startup and then route signalled threads to it. This avoids a page
allocation in every process that ever receives a signal.
Region now has is_user_accessible(), which informs the memory manager how
to map these pages. Previously, we were just passing a "bool user_allowed"
to various functions and I'm not at all sure that any of that was correct.
All the Region constructors are now hidden, and you must go through one of
these helpers to construct a region:
- Region::create_user_accessible(...)
- Region::create_kernel_only(...)
That ensures that we don't accidentally create a Region without specifying
user accessibility. :^)
"Blocking" is not terribly informative, but now that everything is
ported over, we can force the blocker to provide us with a reason.
This does mean that to_string(State) needed to become a member, but
that's OK.
