3 files changed, 24 insertions, 15 deletions

diff --git a/src/core/hle/kernel/shared_memory.cpp b/src/core/hle/kernel/shared_memory.cpp
index 02d5a7a36..d45daca35 100644
--- a/src/core/hle/kernel/shared_memory.cpp
+++ b/src/core/hle/kernel/shared_memory.cpp
@@ -55,22 +55,19 @@ SharedPtr<SharedMemory> SharedMemory::Create(SharedPtr<Process> owner_process, u
             Kernel::g_current_process->vm_manager.RefreshMemoryBlockMappings(linheap_memory.get());
         }
     } else {
-        // TODO(Subv): What happens if an application tries to create multiple memory blocks
-        // pointing to the same address?
         auto& vm_manager = shared_memory->owner_process->vm_manager;
         // The memory is already available and mapped in the owner process.
-        auto vma = vm_manager.FindVMA(address)->second;
-        // Copy it over to our own storage
-        shared_memory->backing_block = std::make_shared<std::vector<u8>>(
-            vma.backing_block->data() + vma.offset, vma.backing_block->data() + vma.offset + size);
-        shared_memory->backing_block_offset = 0;
-        // Unmap the existing pages
-        vm_manager.UnmapRange(address, size);
-        // Map our own block into the address space
-        vm_manager.MapMemoryBlock(address, shared_memory->backing_block, 0, size,
-                                  MemoryState::Shared);
-        // Reprotect the block with the new permissions
-        vm_manager.ReprotectRange(address, size, ConvertPermissions(permissions));
+        auto vma = vm_manager.FindVMA(address);
+        ASSERT_MSG(vma != vm_manager.vma_map.end(), "Invalid memory address");
+        ASSERT_MSG(vma->second.backing_block, "Backing block doesn't exist for address");
+
+        // The returned VMA might be a bigger one encompassing the desired address.
+        auto vma_offset = address - vma->first;
+        ASSERT_MSG(vma_offset + size <= vma->second.size,
+                   "Shared memory exceeds bounds of mapped block");
+
+        shared_memory->backing_block = vma->second.backing_block;
+        shared_memory->backing_block_offset = vma->second.offset + vma_offset;
     }
 
     shared_memory->base_address = address;
@@ -184,4 +181,4 @@ u8* SharedMemory::GetPointer(u32 offset) {
     return backing_block->data() + backing_block_offset + offset;
 }
 
-} // namespace
+} // namespace Kernel
diff --git a/src/core/hle/kernel/thread.cpp b/src/core/hle/kernel/thread.cpp
index 2614a260c..0f7970ebe 100644
--- a/src/core/hle/kernel/thread.cpp
+++ b/src/core/hle/kernel/thread.cpp
@@ -541,6 +541,12 @@ s32 Thread::GetWaitObjectIndex(WaitObject* object) const {
     return static_cast<s32>(std::distance(match, wait_objects.rend()) - 1);
 }
 
+VAddr Thread::GetCommandBufferAddress() const {
+    // Offset from the start of TLS at which the IPC command buffer begins.
+    static constexpr int CommandHeaderOffset = 0x80;
+    return GetTLSAddress() + CommandHeaderOffset;
+}
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
 void ThreadingInit() {
diff --git a/src/core/hle/kernel/thread.h b/src/core/hle/kernel/thread.h
index 4679c2022..314fba81f 100644
--- a/src/core/hle/kernel/thread.h
+++ b/src/core/hle/kernel/thread.h
@@ -164,6 +164,12 @@ public:
         return tls_address;
     }
 
+    /*
+     * Returns the address of the current thread's command buffer, located in the TLS.
+     * @returns VAddr of the thread's command buffer.
+     */
+    VAddr GetCommandBufferAddress() const;
+
     /**
      * Returns whether this thread is waiting for all the objects in
      * its wait list to become ready, as a result of a WaitSynchronizationN call