The stack is misaligned at this point for some reason, this is a hack
that makes the resulting object "correctly" aligned, thus avoiding a
KUBSAN error.
Mere mortals like myself cannot understand more than two lines of
assembly without a million comments explaining what's happening, so do
that and make sure no one has to go on a wild stack state chase when
hacking on these.
The comments were confusing, and had a mathematical error, stop trying
to be clever and just let the computer do the math.
Also assert that we're pushing exactly as many stack elements as we're
using for the alignment calculations.
POSIX requires that sigaction() and friends set a _process-wide_ signal
handler, so move signal handlers and flags inside Process.
This also fixes a "pid/tid confusion" FIXME, as we can now send the
signal to the process and let that decide which thread should get the
signal (which is the thread with tid==pid, but that's now the Process's
problem).
Note that each thread still retains its signal mask, as that is local to
each thread.
Previously register_string would return incorrect values when
called multiple times with the same input. This patch makes this
function return the same index, identical strings. This change was
required, as this functionality is now being used with read syscall
profiling, (#12465), which uses 'register_string' to registers file
path on every read syscall.
If there's no PCI bus, then it's safe to assume that we run on a x86
machine that has an ISA IDE controller in the system. In such case, we
just instantiate a ISAIDEController object that assumes fixed locations
of IDE IO ports.
If there's no PCI bus, then it's safe to assume that the x86 machine we
run on supports VGA text mode console output with an ISA VGA adapter.
If this is the case, we just instantiate a ISAVGAAdapter object that
assumes this situation and allows us to boot into VGA text mode console.
Reading from /proc/pci assumes we have PCI enabled and also enumerated.
However, if PCI is disabled for some reason, we can't allow the user to
read from it as there's no valuable data we can supply.
To declare that we don't have a PCI bus in the system we do two things:
1. Probe IO ports before enabling access -
In case we are using the QEMU ISA-PC machine type, IO probing results in
floating bus condition (returning 0xFF values), thus, we know we don't
have PCI bus on the system.
2. Allow the user to specify to not use the PCI bus at all in the kernel
commandline.
This change allow the user to request the kernel to not use any PCI
resources/devices at all.
Also, don't try to initialize devices that rely on PCI if disabled.
Instead of winging it with "width * 4", use the actual pitch since it
may be different.
This makes the kernel text console show up in native 1368x768 on my
ThinkPad X250. :^)
We now only reset the PCM out channel during initialization, and handle
the case where the channel's current index has passed the last valid
index properly.
This fixes issues with stuttering audio between multiple subsequent
`aplay` invocations, for example.
This might help with debugging on bare metal. Since the minimum version
that can be specified is revision 2.1, and we do not use any feature
from revision 2.2 or newer, this is merely future-proofing ourselves
for new features yet to be built. Additionally, removing the `VERIFY()`
ensures we will not crash on cards that only support earlier revisions.
These are not technically required, since the Thread constructor
already sets these, but they are set on i686, so let's try and keep
consistent behaviour between the different archs.
The Qemu AC'97 device stops its PCM channel's DMA engine when it is
running and the sample rate is changed. We now make sure the DMA engine
is restarted after changing the sample rate, allowing you to e.g. run
`asctl set r 22050` during `aplay` playback.
In short: QEMU supports both Memory-Mapped-IO and classic IO methods
for controlling the emulated VGA device. Bochs and VirtualBox only
support the classic IO method. An excellent write up on the history of
these interfaces can be found here:
https://www.kraxel.org/blog/2018/10/qemu-vga-emulation-and-bochs-display
The IO method was how things were done originally in SerenityOS. Commit
6a728e2d76 introduced the MMIO method for
all devices, breaking Bochs and VirtualBox compatibility. Later in
commit 6a9dc5562d the classic IO method
was restored for VirtualBox graphics adapters.
QEMU and Bochs use the same PCI VID/DID (0x1234/0x1111) for the emulated
VGA adapter. To distinguish betwen QEMU and Bochs we use the PCI
revision ID field (0=Bochs, 2=QEMU).
This driver is not tested and probably not used on any modern hardware
machine, because it is plugged into the ISA bus and not the PCI bus.
Also, the run script doesn't utilize this device anymore, making it more
hard to test this driver and to ensure it doesn't rot.
