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Kernel: munmap multiple regions at a time

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This implements a fallback to munmap that unmaps multiple regions at a
time, with splitting some when needed.

The way it is implemented is possibly not optimal, due to it searching
without looking into the cache
This commit is contained in:
Hendiadyoin1 2021-02-24 17:00:58 +01:00 committed by Andreas Kling
parent 61f0aa6e75
commit b7f1171a1c
Notes: sideshowbarker 2024-07-18 21:26:38 +09:00 
Author: https://github.com/Hendiadyoin1
Commit: https://github.com/SerenityOS/serenity/commit/b7f1171a1ce
Pull-request: https://github.com/SerenityOS/serenity/pull/5510
Issue: https://github.com/SerenityOS/serenity/issues/175
Reviewed-by: https://github.com/BenWiederhake
Reviewed-by: https://github.com/linusg
Reviewed-by: https://github.com/tomuta
1 changed files with 39 additions and 2 deletions
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41
Kernel/Syscalls/mmap.cpp
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@ -1,5 +1,6 @@
/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Leon Albrecht <leon2002.la@gmail.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -490,9 +491,45 @@ KResultOr<int> Process::sys$munmap(Userspace<void*> addr, size_t size)
return 0;
}
// FIXME: We should also support munmap() across multiple regions. (#175)
// Try again while checkin multiple regions at a time
// slow: without caching
const auto& regions = space().find_regions_intersecting(range_to_unmap);
// if there still no regions found error out
if (!regions.size())
return EINVAL;
// check if any of the regions is not mmaped, to not accientally
// error-out with just half a region map left
for (auto* region : regions) {
if (!region->is_mmap())
return EPERM;
}
Vector<Region*, 2> new_regions;
for (auto* old_region : regions) {
// if it's a full match we can delete the complete old region
if (old_region->range().intersect(range_to_unmap).size() == old_region->size()) {
bool res = space().deallocate_region(*old_region);
VERIFY(res);
continue;
}
// otherwise just split the regions and collect them for future mapping
new_regions.append(space().split_region_around_range(*old_region, range_to_unmap));
// We manually unmap the old region here, specifying that we *don't* want the VM deallocated.
old_region->unmap(Region::ShouldDeallocateVirtualMemoryRange::No);
bool res = space().deallocate_region(*old_region);
VERIFY(res);
}
// Instead we give back the unwanted VM manually at the end.
space().page_directory().range_allocator().deallocate(range_to_unmap);
// And finally we map the new region(s) using our page directory (they were just allocated and don't have one).
for (auto* new_region : new_regions) {
new_region->map(space().page_directory());
}
return 0;
}
KResultOr<FlatPtr> Process::sys$mremap(Userspace<const Syscall::SC_mremap_params*> user_params)