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UserspaceEmulator+LibC: Have UE notice realloc() and update accounting

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When a mallocation is shrunk/grown without moving, UE needs to update
its precise metadata about the mallocation, since it tracks *exactly*
how many bytes were allocated, not just the malloc chunk size.
This commit is contained in:
Andreas Kling 2020-11-08 10:10:41 +01:00
parent a0e25b2d31
commit c4dd77a170
4 changed files with 41 additions and 1 deletions
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28
DevTools/UserspaceEmulator/MallocTracer.cpp
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@ -87,6 +87,34 @@ void MallocTracer::target_did_free(Badge<SoftCPU>, FlatPtr address)
Emulator::the().dump_backtrace();
}
void MallocTracer::target_did_realloc(Badge<SoftCPU>, FlatPtr address, size_t size)
{
auto* region = Emulator::the().mmu().find_region({ 0x20, address });
ASSERT(region);
ASSERT(region->is_mmap());
auto& mmap_region = static_cast<MmapRegion&>(*region);
ASSERT(mmap_region.is_malloc_block());
auto* existing_mallocation = find_mallocation(address);
ASSERT(existing_mallocation);
ASSERT(!existing_mallocation->freed);
size_t old_size = existing_mallocation->size;
auto* shadow_bits = mmap_region.shadow_data() + address - mmap_region.base();
if (size > old_size) {
memset(shadow_bits + old_size, 1, size - old_size);
} else {
memset(shadow_bits + size, 1, old_size - size);
}
existing_mallocation->size = size;
// FIXME: Should we track malloc/realloc backtrace separately perhaps?
existing_mallocation->malloc_backtrace = Emulator::the().raw_backtrace();
}
MallocTracer::Mallocation* MallocTracer::find_mallocation(FlatPtr address)
{
for (auto& mallocation : m_mallocations) {