Kernel, APT: SharedFont/SharedMemoryOnSharedDevice should always use old linear heap VAddr

src/core/hle/kernel/shared_memory.cpp

@@ -142,7 +142,10 @@ ResultCode SharedMemory::Map(Process* target_process, VAddr address, MemoryPermi
 
     if (base_address == 0 && target_address == 0) {
         // Calculate the address at which to map the memory block.
-        target_address = linear_heap_phys_offset + target_process->GetLinearHeapAreaAddress();
+        // Note: even on new firmware versions, the target address is still in the old linear heap
+        // region. This exception is made to keep the shared font compatibility. See
+        // APT:GetSharedFont for detail.
+        target_address = linear_heap_phys_offset + Memory::LINEAR_HEAP_VADDR;
     }
 
     auto vma = target_process->vm_manager.FindVMA(target_address);

src/core/hle/service/apt/apt.cpp

@@ -207,10 +207,17 @@ void Module::Interface::GetSharedFont(Kernel::HLERequestContext& ctx) {
 
     // The shared font has to be relocated to the new address before being passed to the
     // application.
-    auto maybe_vaddr = Memory::PhysicalToVirtualAddress(
-        apt->shared_font_mem->linear_heap_phys_offset + Memory::FCRAM_PADDR);
-    ASSERT(maybe_vaddr);
-    VAddr target_address = *maybe_vaddr;
+
+    // Note: the target address is still in the old linear heap region even on new firmware
+    // versions. This exception is made for shared font to resolve the following compatibility
+    // issue:
+    // The linear heap region changes depending on the kernel version marked in application's
+    // exheader (not the actual version the application is running on). If an application with old
+    // kernel version and an applet with new kernel version run at the same time, and they both use
+    // shared font, different linear heap region would have required shared font to relocate
+    // according to two different addresses at the same time, which is impossible.
+    VAddr target_address =
+        apt->shared_font_mem->linear_heap_phys_offset + Memory::LINEAR_HEAP_VADDR;
     if (!apt->shared_font_relocated) {
         BCFNT::RelocateSharedFont(apt->shared_font_mem, target_address);
         apt->shared_font_relocated = true;