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Kernel: Wrap process address spaces in SpinlockProtected

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This forces anyone who wants to look into and/or manipulate an address
space to lock it. And this replaces the previous, more flimsy, manual
spinlock use.

Note that pointers *into* the address space are not safe to use after
you unlock the space. We've got many issues like this, and we'll have
to track those down as wlel.
This commit is contained in:
Andreas Kling 2022-08-23 17:58:05 +02:00
parent d6ef18f587
commit cf16b2c8e6
38 changed files with 708 additions and 627 deletions
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66
Kernel/Syscalls/futex.cpp
View file

@ -18,7 +18,7 @@ static Singleton<SpinlockProtected<HashMap<GlobalFutexKey, NonnullLockRefPtr<Fut
void Process::clear_futex_queues_on_exec()
{
s_global_futex_queues->with([this](auto& queues) {
auto const* address_space = &this->address_space();
auto const* address_space = this->address_space().with([](auto& space) { return space.ptr(); });
queues.remove_all_matching([address_space](auto& futex_key, auto& futex_queue) {
if ((futex_key.raw.offset & futex_key_private_flag) == 0)
return false;
@ -45,45 +45,47 @@ ErrorOr<GlobalFutexKey> Process::get_futex_key(FlatPtr user_address, bool shared
if (!shared) { // If this is thread-shared, we can skip searching the matching region
return GlobalFutexKey {
.private_ = {
.address_space = &address_space(),
.address_space = this->address_space().with([](auto& space) { return space.ptr(); }),
.user_address = user_address | futex_key_private_flag,
}
};
}
auto* matching_region = address_space().find_region_containing(range);
if (!matching_region)
return EFAULT;
return address_space().with([&](auto& space) -> ErrorOr<GlobalFutexKey> {
auto* matching_region = space->find_region_containing(range);
if (!matching_region)
return EFAULT;
// The user wants to share this futex, but if the address doesn't point to a shared resource, there's not
// much sharing to be done, so let's mark this as private
if (!matching_region->is_shared()) {
return GlobalFutexKey {
.private_ = {
.address_space = space.ptr(),
.user_address = user_address | futex_key_private_flag,
}
};
}
// This address is backed by a shared VMObject, if it's an AnonymousVMObject, it can be shared between processes
// via forking, and shared regions that are cloned during a fork retain their original AnonymousVMObject.
// On the other hand, if it's a SharedInodeVMObject, it can be shared by two processes mapping the same file as
// MAP_SHARED, but since they are deduplicated based on the inode, in all cases the VMObject pointer should be
// a unique global identifier.
// NOTE: This assumes that a program will not unmap the only region keeping the vmobject alive while waiting on it,
// if it does, it will get stuck waiting forever until interrupted by a signal, but since that use case is defined as
// a programmer error, we are fine with it.
auto const& vmobject = matching_region->vmobject();
if (vmobject.is_inode())
VERIFY(vmobject.is_shared_inode());
// The user wants to share this futex, but if the address doesn't point to a shared resource, there's not
// much sharing to be done, so let's mark this as private
if (!matching_region->is_shared()) {
return GlobalFutexKey {
.private_ = {
.address_space = &address_space(),
.user_address = user_address | futex_key_private_flag,
}
.shared = {
.vmobject = &vmobject,
.offset = matching_region->offset_in_vmobject_from_vaddr(range.base()) }
};
}
// This address is backed by a shared VMObject, if it's an AnonymousVMObject, it can be shared between processes
// via forking, and shared regions that are cloned during a fork retain their original AnonymousVMObject.
// On the other hand, if it's a SharedInodeVMObject, it can be shared by two processes mapping the same file as
// MAP_SHARED, but since they are deduplicated based on the inode, in all cases the VMObject pointer should be
// a unique global identifier.
// NOTE: This assumes that a program will not unmap the only region keeping the vmobject alive while waiting on it,
// if it does, it will get stuck waiting forever until interrupted by a signal, but since that use case is defined as
// a programmer error, we are fine with it.
auto const& vmobject = matching_region->vmobject();
if (vmobject.is_inode())
VERIFY(vmobject.is_shared_inode());
return GlobalFutexKey {
.shared = {
.vmobject = &vmobject,
.offset = matching_region->offset_in_vmobject_from_vaddr(range.base()) }
};
});
}
ErrorOr<FlatPtr> Process::sys$futex(Userspace<Syscall::SC_futex_params const*> user_params)