Before we start disabling acquisition of the big process lock for
specific syscalls, make sure to document and assert that all the
lock is held during all syscalls.
The entire process is not needed, just require the user to pass in the
Space. Also provide no_lock variant to use when you already have the
VM/Space lock acquired, to avoid unnecessary recursive spinlock
acquisitions.
The non CPU specific code of the kernel shouldn't need to deal with
architecture specific registers, and should instead deal with an
abstract view of the machine. This allows us to remove a variety of
architecture specific ifdefs and helps keep the code slightly more
portable.
We do this by exposing the abstract representation of instruction
pointer, stack pointer, base pointer, return register, etc on the
RegisterState struct.
We should never request a regions removal that we don't currently
own. We currently assert this everywhere else by all callers.
Instead lets just push the assert down into the RedBlackTree removal
and assume that we will always successfully remove the region.
Thread::yield_and_release_relock_big_lock releases the big lock, yields
and then relocks the big lock.
Thread::yield_assuming_not_holding_big_lock yields assuming the big
lock is not being held.
We leak a ref() onto every user process when constructing them,
either via Process::create_user_process(), or via Process::sys$fork().
This ref() is balanced by a corresponding unref() in
Thread::WaitBlockCondition::finalize().
Since kernel processes don't have a leaked ref() on them, this led to
an extra Process::unref() on kernel processes during finalization.
This happened during every boot, with the `init_stage2` process.
Found by turning off kfree() scrubbing. :^)
There appears to be no reason why the process registration needs
to happen under the space spin lock. As the first thread is not started
yet it should be completely uncontested, but it's still bad practice.
The System V ABI for both x86 and x86_64 requires that the stack pointer
is 16-byte aligned on entry. Previously we did not align the stack
pointer properly.
As far as "main" was concerned the stack alignment was correct even
without this patch due to how the C++ _start function and the kernel
interacted, i.e. the kernel misaligned the stack as far as the ABI
was concerned but that misalignment (read: it was properly aligned for
a regular function call - but misaligned in terms of what the ABI
dictates) was actually expected by our _start function.
`.text` segments with non-aligned offsets had their lengths applied to
the first page's base address. This meant that in some cases the last
PAGE_SIZE - 1 bytes weren't mapped. Previously, it did not cause any
problems as the GNU ld insists on aligning everything; but that's not
the case with the LLVM toolchain.
This replaces all uses of LexicalPath in the Kernel with the functions
from KLexicalPath. This also allows the Kernel to stop including
AK::LexicalPath.
There is a race condition where we would remove a FutexQueue from
our futex map and in the meanwhile another thread started to queue
itself into that very same futex, leading to that thread to wait
forever as no other wake operation could discover that removed
FutexQueue.
This fixes the problem by:
* Tracking imminent waits, which prevents a new FutexQueue from being
deleted that a thread will wait on momentarily
* Atomically marking a FutexQueue as removed, which prevents a thread
from waiting on it before it is actually removed from the futex map.
This was an old SerenityOS-specific syscall for donating the remainder
of the calling thread's time-slice to another thread within the same
process.
Now that Threading::Lock uses a pthread_mutex_t internally, we no
longer need this syscall, which allows us to get rid of a surprising
amount of unnecessary scheduler logic. :^)
Specifically, explicitly specify the checked type, use the resulting
value instead of doing the same calculation twice, and break down
calculations to discrete operations to ensure no intermediary overflows
are missed.
When creating uninitialized storage for variables, we need to make sure
that the alignment is correct. Fixes a KUBSAN failure when running
kernels compiled with Clang.
In `Syscalls/socket.cpp`, we can simply use local variables, as
`sockaddr_un` is a POD type.
Along with moving the `alignas` specifier to the correct member,
`AK::Optional`'s internal buffer has been made non-zeroed by default.
GCC emitted bogus uninitialized memory access warnings, so we now use
`__builtin_launder` to tell the compiler that we know what we are doing.
This might disable some optimizations, but judging by how GCC failed to
notice that the memory's initialization is dependent on `m_has_value`,
I'm not sure that's a bad thing.
This changes the m_parts, m_dirname, m_basename, m_title and m_extension
member variables to StringViews onto the m_string String. It also
removes the m_is_absolute member in favour of computing if a path is
absolute in the is_absolute() getter. Due to this, the canonicalize()
method has been completely rewritten.
The parts() getter still returns a Vector<String>, although it is no
longer a const reference as m_parts is no longer a Vector<String>.
Rather, it is constructed from the StringViews in m_parts upon request.
The parts_view() getter has been added, which returns Vector<StringView>
const&. Most previous users of parts() have been changed to use
parts_view(), except where Strings are required.
Due to this change, it's is now no longer allow to create temporary
LexicalPath objects to call the dirname, basename, title, or extension
getters on them because the returned StringViews will point to possible
freed memory.
The LexicalPath instance methods dirname(), basename(), title() and
extension() will be changed to return StringView const& in a further
commit. Due to this, users creating temporary LexicalPath objects just
to call one of those getters will recieve a StringView const& pointing
to a possible freed buffer.
To avoid this, static methods for those APIs have been added, which will
return a String by value to avoid those problems. All cases where
temporary LexicalPath objects have been used as described above haven
been changed to use the static APIs.
The new ProcFS design consists of two main parts:
1. The representative ProcFS class, which is derived from the FS class.
The ProcFS and its inodes are much more lean - merely 3 classes to
represent the common type of inodes - regular files, symbolic links and
directories. They're backed by a ProcFSExposedComponent object, which
is responsible for the functional operation behind the scenes.
2. The backend of the ProcFS - the ProcFSComponentsRegistrar class
and all derived classes from the ProcFSExposedComponent class. These
together form the entire backend and handle all the functions you can
expect from the ProcFS.
The ProcFSExposedComponent derived classes split to 3 types in the
manner of lifetime in the kernel:
1. Persistent objects - this category includes all basic objects, like
the root folder, /proc/bus folder, main blob files in the root folders,
etc. These objects are persistent and cannot die ever.
2. Semi-persistent objects - this category includes all PID folders,
and subdirectories to the PID folders. It also includes exposed objects
like the unveil JSON'ed blob. These object are persistent as long as the
the responsible process they represent is still alive.
3. Dynamic objects - this category includes files in the subdirectories
of a PID folder, like /proc/PID/fd/* or /proc/PID/stacks/*. Essentially,
these objects are always created dynamically and when no longer in need
after being used, they're deallocated.
Nevertheless, the new allocated backend objects and inodes try to use
the same InodeIndex if possible - this might change only when a thread
dies and a new thread is born with a new thread stack, or when a file
descriptor is closed and a new one within the same file descriptor
number is opened. This is needed to actually be able to do something
useful with these objects.
The new design assures that many ProcFS instances can be used at once,
with one backend for usage for all instances.
The intention is to add dynamic mechanism for notifying the userspace
about hotplug events. Currently, the DMI (SMBIOS) blobs and ACPI tables
are exposed in the new filesystem.
