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Kernel+LibC: Allow sys$mmap() callers to specify address alignment

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This is exposed via the non-standard serenity_mmap() call in userspace.
This commit is contained in:
Andreas Kling 2020-02-16 12:55:56 +01:00
parent 02e199a9cb
commit 31e1af732f
7 changed files with 66 additions and 30 deletions
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20
Kernel/VM/RangeAllocator.cpp
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@ -94,7 +94,7 @@ void RangeAllocator::carve_at_index(int index, const Range& range)
m_available_ranges.insert(index + 1, move(remaining_parts[1]));
}
Range RangeAllocator::allocate_anywhere(size_t size)
Range RangeAllocator::allocate_anywhere(size_t size, size_t alignment)
{
#ifdef VM_GUARD_PAGES
// NOTE: We pad VM allocations with a guard page on each side.
@ -104,26 +104,32 @@ Range RangeAllocator::allocate_anywhere(size_t size)
size_t effective_size = size;
size_t offset_from_effective_base = 0;
#endif
for (int i = 0; i < m_available_ranges.size(); ++i) {
auto& available_range = m_available_ranges[i];
if (available_range.size() < effective_size)
// FIXME: This check is probably excluding some valid candidates when using a large alignment.
if (available_range.size() < (effective_size + alignment))
continue;
Range allocated_range(available_range.base().offset(offset_from_effective_base), size);
if (available_range.size() == effective_size) {
uintptr_t initial_base = available_range.base().offset(offset_from_effective_base).get();
uintptr_t aligned_base = round_up_to_power_of_two(initial_base, alignment);
Range allocated_range(VirtualAddress(aligned_base), size);
if (available_range == allocated_range) {
#ifdef VRA_DEBUG
dbgprintf("VRA: Allocated perfect-fit anywhere(%u): %x\n", size, allocated_range.base().get());
dbgprintf("VRA: Allocated perfect-fit anywhere(%zu, %zu): %x\n", size, alignment, allocated_range.base().get());
#endif
m_available_ranges.remove(i);
return allocated_range;
}
carve_at_index(i, allocated_range);
#ifdef VRA_DEBUG
dbgprintf("VRA: Allocated anywhere(%u): %x\n", size, allocated_range.base().get());
dbgprintf("VRA: Allocated anywhere(%zu, %zu): %x\n", size, alignment, allocated_range.base().get());
dump();
#endif
return allocated_range;
}
kprintf("VRA: Failed to allocate anywhere: %u\n", size);
kprintf("VRA: Failed to allocate anywhere: %zu, %zu\n", size, alignment);
return {};
}