Now that we no longer need to support the signal trampolines being
user-accessible inside the kernel memory range, we can get rid of the
"kernel" and "user-accessible" flags on Region and simply use the
address of the region to determine whether it's kernel or user.
This also tightens the page table mapping code, since it can now set
user-accessibility based solely on the virtual address of a page.
The signal trampoline was previously in kernelspace memory, but with
a special exception to make it user-accessible.
This patch moves it into each process's regular address space so we
can stop supporting user-allowed memory above 0xc0000000.
This patch adds Space, a class representing a process's address space.
- Each Process has a Space.
- The Space owns the PageDirectory and all Regions in the Process.
This allows us to reorganize sys$execve() so that it constructs and
populates a new Space fully before committing to it.
Previously, we would construct the new address space while still
running in the old one, and encountering an error meant we had to do
tedious and error-prone rollback.
Those problems are now gone, replaced by what's hopefully a set of much
smaller problems and missing cleanups. :^)
Wrap thread creation in a Thread::try_create() helper that first
allocates a kernel stack region. If that allocation fails, we propagate
an ENOMEM error to the caller.
This avoids the situation where a thread is half-constructed, without a
valid kernel stack, and avoids having to do messy cleanup in that case.
There's no need for this to be generic and support running from an
arbitrary thread context. Perf events are always generated from within
the thread being profiled, so take advantage of that to simplify the
code. Also use Vector capacity to avoid heap allocations.
This allows us to get rid of the thread lists in SchedulerData.
Also, instead of iterating over all threads to find a thread by id,
just use a lookup table. In the rare case of having to iterate over
all threads, just iterate the lookup table.
Rather than walking all Thread instances and putting them into
a vector to be sorted by priority, queue them into priority sorted
linked lists as soon as they become ready to be executed.
Attempt to wake idle processors to get threads to be scheduled more quickly.
We don't want to wait until the next timer tick if we have processors that
aren't doing anything.
This allows us to determine what the previous mode (user or kernel)
was, e.g. in the timer interrupt. This is used e.g. to determine
whether a signal handler should be set up.
Fixes#5096
Let's force callers to provide a VM range when allocating a region.
This makes ENOMEM error handling more visible and removes implicit
VM allocation which felt a bit magical.
This was done with the help of several scripts, I dump them here to
easily find them later:
awk '/#ifdef/ { print "#cmakedefine01 "$2 }' AK/Debug.h.in
for debug_macro in $(awk '/#ifdef/ { print $2 }' AK/Debug.h.in)
do
find . \( -name '*.cpp' -o -name '*.h' -o -name '*.in' \) -not -path './Toolchain/*' -not -path './Build/*' -exec sed -i -E 's/#ifdef '$debug_macro'/#if '$debug_macro'/' {} \;
done
# Remember to remove WRAPPER_GERNERATOR_DEBUG from the list.
awk '/#cmake/ { print "set("$2" ON)" }' AK/Debug.h.in
It was possible to signal a process while it was paging in an inode
backed VM object. This would cause the inode read to EINTR, and the
page fault handler would assert.
Solve this by simply not unblocking threads due to signals if they are
currently busy handling a page fault. This is probably not the best way
to solve this issue, so I've added a FIXME to that effect.
These changes are arbitrarily divided into multiple commits to make it
easier to find potentially introduced bugs with git bisect.
This commit touches some dbg() calls which are enclosed in macros. This
should be fine because with the new constexpr stuff, we ensure that the
stuff actually compiles.
Problem:
- Many constructors are defined as `{}` rather than using the ` =
default` compiler-provided constructor.
- Some types provide an implicit conversion operator from `nullptr_t`
instead of requiring the caller to default construct. This violates
the C++ Core Guidelines suggestion to declare single-argument
constructors explicit
(https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit).
Solution:
- Change default constructors to use the compiler-provided default
constructor.
- Remove implicit conversion operators from `nullptr_t` and change
usage to enforce type consistency without conversion.
This patch merges the profiling functionality in the kernel with the
performance events mechanism. A profiler sample is now just another
perf event, rather than a dedicated thing.
Since perf events were already per-process, this now makes profiling
per-process as well.
Processes with perf events would already write out a perfcore.PID file
to the current directory on death, but since we may want to profile
a process and then let it continue running, recorded perf events can
now be accessed at any time via /proc/PID/perf_events.
This patch also adds information about process memory regions to the
perfcore JSON format. This removes the need to supply a core dump to
the Profiler app for symbolication, and so the "profiler coredump"
mechanism is removed entirely.
There's still a hard limit of 4MB worth of perf events per process,
so this is by no means a perfect final design, but it's a nice step
forward for both simplicity and stability.
Fixes#4848Fixes#4849
If the allocation fails (e.g ENOMEM) we want to simply return an error
from sys$execve() and continue executing the current executable.
This patch also moves make_userspace_stack_for_main_thread() out of the
Thread class since it had nothing in particular to do with Thread.
Now that the CrashDaemon symbolicates crashes in userspace, let's take
this one step further and stop trying to symbolicate userspace programs
in the kernel at all.
This implements a number of changes related to time:
* If a HPET is present, it is now used only as a system timer, unless
the Local APIC timer is used (in which case the HPET timer will not
trigger any interrupts at all).
* If a HPET is present, the current time can now be as accurate as the
chip can be, independently from the system timer. We now query the
HPET main counter for the current time in CPU #0's system timer
interrupt, and use that as a base line. If a high precision time is
queried, that base line is used in combination with quering the HPET
timer directly, which should give a much more accurate time stamp at
the expense of more overhead. For faster time stamps, the more coarse
value based on the last interrupt will be returned. This also means
that any missed interrupts should not cause the time to drift.
* The default system interrupt rate is reduced to about 250 per second.
* Fix calculation of Thread CPU usage by using the amount of ticks they
used rather than the number of times a context switch happened.
* Implement CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE and use it
for most cases where precise timestamps are not needed.
Problem:
- `(void)` simply casts the expression to void. This is understood to
indicate that it is ignored, but this is really a compiler trick to
get the compiler to not generate a warning.
Solution:
- Use the `[[maybe_unused]]` attribute to indicate the value is unused.
Note:
- Functions taking a `(void)` argument list have also been changed to
`()` because this is not needed and shows up in the same grep
command.
We need to account for how many shared lock instances the current
thread owns, so that we can properly release such references when
yielding execution.
We also need to release the process lock when donating.
When a process crashes, we generate a coredump file and write it in
/tmp/coredumps/.
The coredump file is an ELF file of type ET_CORE.
It contains a segment for every userspace memory region of the process,
and an additional PT_NOTE segment that contains the registers state for
each thread, and a additional data about memory regions
(e.g their name).
When the main executable needs an interpreter, we load the requested
interpreter program, and pass to it an open file decsriptor to the main
executable via the auxiliary vector.
Note that we do not allocate a TLS region for the interpreter.
