Even if the PIC was disabled it can still generate noise (spurious IRQs)
so we need to register two handlers for handling such cases.
Also, we declare interrupt service routine offset 0x20 to 0x2f as
reserved, so when the PIC is disabled, we can handle spurious IRQs from
the PIC at separate handlers.
Move this architecture-specific sanity check (IOPL must be 0) out of
Scheduler and into the x86 enter_thread_context(). Also do this for
every thread and not just userspace ones.
It was annoyingly hard to spot these when we were using them with
different amounts of qualification everywhere.
This patch uses Thread::State::Foo everywhere instead of Thread::Foo
or just Foo.
Signal dispatch is already taken care of elsewhere, so there appears to
be no need for the hack in enter_current().
This also allows us to remove the Thread::m_in_block flag, simplifying
thread blocking logic somewhat.
Verified with the original repro for #4336 which this was meant to fix.
Ideally the x86 fault handler would only do x86 specific things and
delegate the rest of the work to MemoryManager. This patch moves some of
the address checks to a more generic place.
This allows us to enable Write-Combine on e.g. framebuffers,
significantly improving performance on bare metal.
To keep things simple we right now only use one of up to three bits
(bit 7 in the PTE), which maps to the PA4 entry in the PAT MSR, which
we set to the Write-Combine mode on each CPU at boot time.
If there's nobody listening for the crash signal, fall back to the
normal crash path where we get some debug output about what happened.
Thanks to Idan for suggesting the fix.
Since the inline capacity of the Vector return type was not specified
explicitly, the vector was automatically copied to a 0-length inline
capacity one, essentially eliminating the optimization.
Contradictory to the comment above it, this while loop was actually
clearing the selectors above or equal to the edited one (instead of
the selectors that were skipped when the gdt was extended), this wasn't
really an issue so far, as all calls to this function did extend the
GDT, which meant this condition was always false, but future calls to
this function that will try to edit an existing entry would fail.
... instead of returning the maximum number of Processor objects that we
can allocate.
Some ports (e.g. gdb) rely on this information to determine the number
of worker threads to spawn. When gdb spawned 64 threads, the kernel
could not cope with generating backtraces for it, which prevented us
from debugging it properly.
This commit also removes the confusingly named
`Processor::processor_count` function so that this mistake can't happen
again.
Add a kernel data segment and make the user code segment come after
the data segment. We need the GDT to be in a certain order to support
the syscall and sysret instruction pair.
In order to reduce our reliance on __builtin_{ffs, clz, ctz, popcount},
this commit removes all calls to these functions and replaces them with
the equivalent functions in AK/BuiltinWrappers.h.
Unsurprisingly, the /proc/PID/stacks/TID stack walk had the same
arbitrary memory read problem as the perf event stack walk.
It would be nice if the kernel had a single stack walk implementation,
but that's outside the scope of this commit.
Clang rejects binding a reference to a null pointer at compile-time.
Let's just crash explicitly, instead of waiting for a null dereference
to mess things up.
SIGSTKFLT is a signal that signifies a stack fault in a x87 coprocessor,
this signal is not POSIX and also unused by Linux and the BSDs, so let's
use SIGSEGV so programs that setup signal handlers for the common
signals could still handle them in serenity.
