kernel/vm_manager: Handle shrinking of the heap size within SetHeapSize()

One behavior that we weren't handling properly in our heap allocation
process was the ability for the heap to be shrunk down in size if a
larger size was previously requested.

This adds the basic behavior to do so and also gets rid of HeapFree, as
it's no longer necessary now that we have allocations and deallocations
going through the same API function.

While we're at it, fully document the behavior that this function
performs.

1 files changed, 13 insertions, 21 deletions

diff --git a/src/core/hle/kernel/vm_manager.cpp b/src/core/hle/kernel/vm_manager.cpp
index 523fe63e9..ec0a480ce 100644
--- a/src/core/hle/kernel/vm_manager.cpp
+++ b/src/core/hle/kernel/vm_manager.cpp
@@ -274,14 +274,23 @@ ResultVal<VAddr> VMManager::SetHeapSize(u64 size) {
         UnmapRange(heap_region_base, GetCurrentHeapSize());
     }
 
-    // If necessary, expand backing vector to cover new heap extents.
-    if (size > GetCurrentHeapSize()) {
-        const u64 alloc_size = size - GetCurrentHeapSize();
+    // If necessary, expand backing vector to cover new heap extents in
+    // the case of allocating. Otherwise, shrink the backing memory,
+    // if a smaller heap has been requested.
+    const u64 old_heap_size = GetCurrentHeapSize();
+    if (size > old_heap_size) {
+        const u64 alloc_size = size - old_heap_size;
 
         heap_memory->insert(heap_memory->end(), alloc_size, 0);
-        heap_end = heap_region_base + size;
+        RefreshMemoryBlockMappings(heap_memory.get());
+    } else if (size < old_heap_size) {
+        heap_memory->resize(size);
+        heap_memory->shrink_to_fit();
+
         RefreshMemoryBlockMappings(heap_memory.get());
     }
+
+    heap_end = heap_region_base + size;
     ASSERT(GetCurrentHeapSize() == heap_memory->size());
 
     const auto mapping_result =
@@ -293,23 +302,6 @@ ResultVal<VAddr> VMManager::SetHeapSize(u64 size) {
     return MakeResult<VAddr>(heap_region_base);
 }
 
-ResultCode VMManager::HeapFree(VAddr target, u64 size) {
-    if (!IsWithinHeapRegion(target, size)) {
-        return ERR_INVALID_ADDRESS;
-    }
-
-    if (size == 0) {
-        return RESULT_SUCCESS;
-    }
-
-    const ResultCode result = UnmapRange(target, size);
-    if (result.IsError()) {
-        return result;
-    }
-
-    return RESULT_SUCCESS;
-}
-
 MemoryInfo VMManager::QueryMemory(VAddr address) const {
     const auto vma = FindVMA(address);
     MemoryInfo memory_info{};