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Kernel/SharedMemory: Don't take over and unmap the source memory block when creating a shared memory, just reference it.
Also reference the right offset into the backing block for the requested address.
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@ -55,22 +55,19 @@ SharedPtr<SharedMemory> SharedMemory::Create(SharedPtr<Process> owner_process, u
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Kernel::g_current_process->vm_manager.RefreshMemoryBlockMappings(linheap_memory.get());
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}
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} else {
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// TODO(Subv): What happens if an application tries to create multiple memory blocks
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// pointing to the same address?
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auto& vm_manager = shared_memory->owner_process->vm_manager;
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// The memory is already available and mapped in the owner process.
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auto vma = vm_manager.FindVMA(address)->second;
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// Copy it over to our own storage
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shared_memory->backing_block = std::make_shared<std::vector<u8>>(
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vma.backing_block->data() + vma.offset, vma.backing_block->data() + vma.offset + size);
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shared_memory->backing_block_offset = 0;
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// Unmap the existing pages
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vm_manager.UnmapRange(address, size);
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// Map our own block into the address space
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vm_manager.MapMemoryBlock(address, shared_memory->backing_block, 0, size,
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MemoryState::Shared);
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// Reprotect the block with the new permissions
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vm_manager.ReprotectRange(address, size, ConvertPermissions(permissions));
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auto vma = vm_manager.FindVMA(address);
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ASSERT_MSG(vma != vm_manager.vma_map.end(), "Invalid memory address");
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ASSERT_MSG(vma->second.backing_block, "Backing block doesn't exist for address");
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// The returned VMA might be a bigger one encompassing the desired address.
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auto vma_offset = address - vma->first;
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ASSERT_MSG(vma_offset + size <= vma->second.size,
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"Shared memory exceeds bounds of mapped block");
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shared_memory->backing_block = vma->second.backing_block;
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shared_memory->backing_block_offset = vma->second.offset + vma_offset;
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}
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shared_memory->base_address = address;
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@ -184,4 +181,4 @@ u8* SharedMemory::GetPointer(u32 offset) {
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return backing_block->data() + backing_block_offset + offset;
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}
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} // namespace
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} // namespace Kernel
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