In the same fashion like in the Linux kernel, we support pre-initialized
framebuffers that were set up by either the BIOS or the bootloader.
These framebuffers can be backed by any kind of video hardware, and are
not tied to VGA hardware at all. Therefore, this code should be in a
separate sub-folder in the Graphics subsystem to indicate this.
The flag will automatically initialize all variables to a pattern based
on it's type. The goal being here is to eradicate an entire bug class
of issues that can originate from uninitialized stack memory.
Some examples include:
- Kernel information disclosure, where uninitialized struct members
or struct padding is copied back to usermode, leaking kernel
information such as stack or heap addresses, or secret data like
stack cookies.
- Control flow based on uninitialized memory can cause a variety of
issues at runtime, including stack corruptions like buffer
overflows, heap corruptions due to deleting stray pointers.
Even basic logic bugs can result from control flow operating on
uninitialized data.
As of GCC 12 this flag is now supported.
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=a25e0b5e6ac8a77a71c229e0a7b744603365b0e9
Clang has already supported it for a few releases.
https://reviews.llvm.org/D54604
When the size of the audio data was not a multiple of a page size,
subtracting the page size from this unsigned variable would underflow it
close to 2^32 and be clamped to the page size again. This would lead to
writes into garbage addresses because of an incorrect write size,
interestingly only causing the write() call to error out.
Using saturating math neatly fixes this problem and allows buffer
lengths that are not a multiple of a page size.
Currently CursorStyle enum handles both the styles and the steadiness or
blinking of the terminal caret, which doubles the amount of its entries.
This commit changes CursorStyle to CursorShape and moves the blinking
option to a seperate boolean value.
The RDGSBASE userspace instruction allows programs to read the contents
of the gs segment register which contains a kernel pointer to the base
of the current Processor struct.
Since we don't use this instruction in Serenity at the moment, we can
simply disable it for now to ensure we don't break KASLR. Support can
later be restored once proper swapping of the contents of gs is done on
userspace/kernel boundaries.
This is basically unchanged since the beginning of 2020, which is a year
before we had proper ASLR.
Now that we have a proper ASLR implementation, we can turn this down a
bit, as it is no longer our only protection against predictable dynamic
loader addresses, and it actually obstructs the default loading address
of x86_64 quite frequently.
There's nothing stopping a userspace program from keeping a bunch of
threads around with a custom signal stack in a suspended state with
their normal thread stack mprotected to PROT_NONE.
OpenJDK seems to do this, for example.
In a previous commit I moved everything into the new subdirectories in
FileSystem/SysFS directory without trying to actually make changes in
the code itself too much. Now it's time to split the code to make it
more readable and understandable, hence this change occurs now.
This is necessary for the next commit in the patch, otherwise this can't
be compiled. It seems like this was a hidden issue that is discovered
now only by changing includes in a mass-scale.
Move methods that are overriding the virtual methods in the File class,
to a private access scope in the DisplayConnector class because nobody
tries to access them in any derived class of this class.
- Remove some magic numbers
- Remove some duplicate branches
- Reduce the amount of casting between u8* and u32*
- Some renaming of confusing variables
The WindowServer doesn't use this interface anymore and therefore it's
not used by any userspace application, so let's remove this stale method
to ensure we don't have to bother with it anymore.
The mmap interface was removed when we introduced the DisplayConnector
class, as it was quite unsafe to use and didn't handle switching between
graphical and text modes safely. By using the SharedFramebufferVMObject,
we are able to elegantly coordinate the switch by remapping the attached
mmap'ed-Memory::Region(s) with different mappings, therefore, keeping
WindowServer to think that the mappings it has are still valid, while
they are going to a different physical range until we are back to the
graphical mode (after a switch from text mode).
Most drivers take advantage of the fact that we know where is the actual
framebuffer in physical memory space, the SharedFramebufferVMObject is
created with that information. However, the VirtIO driver is different
in that aspect, because it relies on DMA transactions to show graphics
on the framebuffer, so the SharedFramebufferVMObject is created with
that mindset to support the arbitrary framebuffer location in physical
memory space.
This new type of VMObject will be used to coordinate switching safely
from graphical mode to text mode and vice-versa, by supplying a way to
remap all Regions that were created with this object, so mappings can be
changed according to the given state of system mode. This makes it quite
easy to give applications like WindowServer the feeling of having full
access to the framebuffer device from a DisplayConnector, but still keep
the Kernel in control to be able to safely switch to text console.
We should first enable the VirtualConsole and then enable graphical
mode, to ensure proper display output on the switched-to virtual console
that has been chosen. When de-activating graphical mode, we do the
de-activating first then enable the VirtualConsole to ensure proper text
output on screen.
Keeping the exact details of a dirty rectangle doesn't make any sense
when we just flush the entire screen, so just keep a simple boolean
value to know if the screen needs to be flushed or not.
This change unifies the naming convention for kernel tasks.
The goal of this change is to:
- Make the task names more descriptive, so users can more
easily understand their purpose in System Monitor.
- Unify the naming convention so they are consistent.
For an upcoming change to support interrupts in this driver, this class
has to inherit from IRQHandler. That in turn will make this class
virtual, which will then actually call the destructor of the class. We
don't want this to happen, thus we have to wrap the class in a
AK::NeverDestroyed.
These 2 classes currently contain much code that is x86(_64) specific.
Move them to the architecture specific directory. This also allows for a
simpler implementation for aarch64.
