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XOR encoded next_object

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This commit adds a simple XOR encoding to the next_object pointer in
FreeObjects.  This removes the trivial way of getting hold of a physical
address from the system by observing the free list pointers in
deallocated objects.
This commit is contained in:
Matthew Parkinson
2021-07-26 09:56:48 +01:00
committed by Matthew Parkinson
parent b69505fc5d
commit 81bf341732
9 changed files with 136 additions and 65 deletions
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8
src/mem/corealloc.h
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@@ -141,7 +141,7 @@ namespace snmalloc
{
auto slab_end = pointer_offset(bumpptr, slab_size + 1 - rsize);
FreeListKey key(entropy.get_constant_key());
auto& key = entropy.get_free_list_key();
FreeListBuilder<false> b;
SNMALLOC_ASSERT(b.empty());
@@ -209,7 +209,7 @@ namespace snmalloc
ChunkRecord* clear_slab(Metaslab* meta, sizeclass_t sizeclass)
{
FreeListKey key(entropy.get_constant_key());
auto& key = entropy.get_free_list_key();
FreeListIter fl;
meta->free_queue.close(fl, key);
void* p = finish_alloc_no_zero(fl.take(key), sizeclass);
@@ -475,7 +475,7 @@ namespace snmalloc
auto cp = CapPtr<FreeObject, CBAlloc>(reinterpret_cast<FreeObject*>(p));
FreeListKey key(entropy.get_constant_key());
auto& key = entropy.get_free_list_key();
// Update the head and the next pointer in the free list.
meta->free_queue.add(cp, key, entropy);
@@ -538,7 +538,7 @@ namespace snmalloc
// Set meta slab to empty.
meta->initialise(sizeclass);
FreeListKey key(entropy.get_constant_key());
auto& key = entropy.get_free_list_key();
// take an allocation from the free list
auto p = fast_free_list.take(key);