This syscall only reads from the shared m_space field, but that field
is only over written to by Process::attach_resources, before the
process was initialized (aka, before syscalls can happen), by
Process::finalize which is only called after all the process' threads
have exited (aka, syscalls can not happen anymore), and by
Process::do_exec which calls all other syscall-capable threads before
doing so. Space's find_region_containing already holds its own lock,
and as such there's no need to hold the big lock.
This syscall doesn't touch any intra-process shared resources and only
accesses the time via the atomic TimeManagement::now so there's no need
to hold the big lock.
This syscall doesn't touch any intra-process shared resources and only
accesses the time via the atomic TimeManagement::current_time so there's
no need to hold the big lock.
This syscall doesn't touch any intra-process shared resources and
reads the time via the atomic TimeManagement::current_time, so it
doesn't need to hold any lock.
...and also RangeAllocator => VirtualRangeAllocator.
This clarifies that the ranges we're dealing with are *virtual* memory
ranges and not anything else.
The sys$alarm() syscall has logic to cache a m_alarm_timer to avoid
allocating a new timer for every call to alarm. Unfortunately that
logic was broken, and there were conditions in which we could have
a timer allocated, but it was no longer on the timer queue, and we
would attempt to cancel that timer again resulting in an infinite
loop waiting for the timers callback to fire.
To fix this, we need to track if a timer is currently in use or not,
allowing us to avoid attempting to cancel inactive timers.
Luke and Tom did the initial investigation, I just happened to have
time to write a repro and attempt a fix, so I'm adding them as the
as co-authors of this commit.
Co-authored-by: Luke <luke.wilde@live.co.uk>
Co-authored-by: Tom <tomut@yahoo.com>
This isn't needed for Process / Thread as they only reference it
by pointer and it's already part of Kernel/Forward.h. So just include
it where the implementation needs to call it.
AnonymousVMObject::set_volatile() assumes that nobody ever calls it on
non-purgeable objects, so let's make sure we don't do that.
Also return EINVAL instead of EPERM for non-anonymous VM objects so the
error codes match.
Previously it was possible to leak the file descriptor if we error out
after allocating the first descriptor. Now we perform both fd
allocations back to back so we can handle the potential error when
processing the second fd allocation.
The way the Process::FileDescriptions::allocate() API works today means
that two callers who allocate back to back without associating a
FileDescription with the allocated FD, will receive the same FD and thus
one will stomp over the other.
Naively tracking which FileDescriptions are allocated and moving onto
the next would introduce other bugs however, as now if you "allocate"
a fd and then return early further down the control flow of the syscall
you would leak that fd.
This change modifies this behavior by tracking which descriptions are
allocated and then having an RAII type to "deallocate" the fd if the
association is not setup the end of it's scope.
This was previously used for a single debug logging statement during
memory purging. There are no remaining users of this weak pointer,
so let's get rid of it.
This patch changes the semantics of purgeable memory.
- AnonymousVMObject now has a "purgeable" flag. It can only be set when
constructing the object. (Previously, all anonymous memory was
effectively purgeable.)
- AnonymousVMObject now has a "volatile" flag. It covers the entire
range of physical pages. (Previously, we tracked ranges of volatile
pages, effectively making it a page-level concept.)
- Non-volatile objects maintain a physical page reservation via the
committed pages mechanism, to ensure full coverage for page faults.
- When an object is made volatile, it relinquishes any unused committed
pages immediately. If later made non-volatile again, we then attempt
to make a new committed pages reservation. If this fails, we return
ENOMEM to userspace.
mmap() now creates purgeable objects if passed the MAP_PURGEABLE option
together with MAP_ANONYMOUS. anon_create() memory is always purgeable.
This bug manifests it self when the caller to sys$pledge() passes valid
promises, but invalid execpromises. The code would apply the promises
and then return an error for the execpromises. This leaves the user in
a confusing state, as the promises were silently applied, but we return
an error suggesting the operation has failed.
Avoid this situation by tweaking the implementation to only apply the
promises / execpromises after all validation has occurred.
This patch greatly simplifies VMObject locking by doing two things:
1. Giving VMObject an IntrusiveList of all its mapping Region objects.
2. Removing VMObject::m_paging_lock in favor of VMObject::m_lock
Before (1), VMObject::for_each_region() was forced to acquire the
global MM lock (since it worked by walking MemoryManager's list of
all regions and checking for regions that pointed to itself.)
With each VMObject having its own list of Regions, VMObject's own
m_lock is all we need.
Before (2), page fault handlers used a separate mutex for preventing
overlapping work. This design required multiple temporary unlocks
and was generally extremely hard to reason about.
Instead, page fault handlers now use VMObject's own m_lock as well.
Depending on the values it might be difficult to figure out whether a
value is decimal or hexadecimal. So let's make this more obvious. Also
this allows copying and pasting those numbers into GNOME calculator and
probably also other apps which auto-detect the base.
Advisory locks don't actually prevent other processes from writing to
the file, but they do prevent other processes looking to acquire and
advisory lock on the file.
This implementation currently only adds non-blocking locks, which are
all I need for now.
