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Kernel: Make it possible to turn off VM guard pages at compile time

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This might be useful for debugging since guard pages introduce a fair
amount of noise in the virtual address space.
This commit is contained in:
Andreas Kling 2019-09-30 17:21:45 +02:00
parent 1a279c5b2a
commit ac20919b13
1 changed files with 11 additions and 4 deletions
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15
Kernel/VM/RangeAllocator.cpp
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@ -3,6 +3,7 @@
#include <Kernel/kstdio.h> #include <Kernel/kstdio.h>
//#define VRA_DEBUG //#define VRA_DEBUG
#define VM_GUARD_PAGES
RangeAllocator::RangeAllocator(VirtualAddress base, size_t size) RangeAllocator::RangeAllocator(VirtualAddress base, size_t size)
{ {
@ -59,14 +60,20 @@ void RangeAllocator::carve_at_index(int index, const Range& range)
Range RangeAllocator::allocate_anywhere(size_t size) Range RangeAllocator::allocate_anywhere(size_t size)
{ {
#ifdef VM_GUARD_PAGES
// NOTE: We pad VM allocations with a guard page on each side. // NOTE: We pad VM allocations with a guard page on each side.
size_t padded_size = size + PAGE_SIZE * 2; size_t effective_size = size + PAGE_SIZE * 2;
size_t offset_from_effective_base = PAGE_SIZE;
#else
size_t effective_size = size;
size_t offset_from_effective_base = 0;
#endif
for (int i = 0; i < m_available_ranges.size(); ++i) { for (int i = 0; i < m_available_ranges.size(); ++i) {
auto& available_range = m_available_ranges[i]; auto& available_range = m_available_ranges[i];
if (available_range.size() < padded_size) if (available_range.size() < effective_size)
continue; continue;
Range allocated_range(available_range.base().offset(PAGE_SIZE), size); Range allocated_range(available_range.base().offset(offset_from_effective_base), size);
if (available_range.size() == padded_size) { if (available_range.size() == effective_size) {
#ifdef VRA_DEBUG #ifdef VRA_DEBUG
dbgprintf("VRA: Allocated perfect-fit anywhere(%u): %x\n", size, allocated_range.base().get()); dbgprintf("VRA: Allocated perfect-fit anywhere(%u): %x\n", size, allocated_range.base().get());
#endif #endif