From 4cb7a44d4e30cd7bc0ec0f07b4b734a7e03f1a3a Mon Sep 17 00:00:00 2001
From: bunnei <bunneidev@gmail.com>
Date: Sat, 22 Nov 2014 22:35:45 -0500
Subject: [PATCH 1/3] MemMap: Renamed "GSP" heap to "linear", as this is not
 specific to GSP.

- Linear simply indicates that the mapped physical address is always MappedVAddr+0x0C000000, thus this memory can be used for hardware devices' DMA (such as the GPU).
---
 src/core/hle/svc.cpp       |  2 +-
 src/core/mem_map.cpp       | 16 ++++++++--------
 src/core/mem_map.h         | 14 +++++++-------
 src/core/mem_map_funcs.cpp | 32 ++++++++++++++++----------------
 src/video_core/pica.h      |  4 ++--
 5 files changed, 34 insertions(+), 34 deletions(-)

diff --git a/src/core/hle/svc.cpp b/src/core/hle/svc.cpp
index a5805ed051..b99c301d41 100644
--- a/src/core/hle/svc.cpp
+++ b/src/core/hle/svc.cpp
@@ -43,7 +43,7 @@ static Result ControlMemory(u32* out_addr, u32 operation, u32 addr0, u32 addr1,
 
     // Map GSP heap memory
     case MEMORY_OPERATION_GSP_HEAP:
-        *out_addr = Memory::MapBlock_HeapGSP(size, operation, permissions);
+        *out_addr = Memory::MapBlock_HeapLinear(size, operation, permissions);
         break;
 
     // Unknown ControlMemory operation
diff --git a/src/core/mem_map.cpp b/src/core/mem_map.cpp
index 74a93b1d92..e1c2580ffe 100644
--- a/src/core/mem_map.cpp
+++ b/src/core/mem_map.cpp
@@ -18,7 +18,7 @@ static MemArena arena;                       ///< The MemArena class
 u8* g_exefs_code                = nullptr;   ///< ExeFS:/.code is loaded here
 u8* g_system_mem                = nullptr;   ///< System memory
 u8* g_heap                      = nullptr;   ///< Application heap (main memory)
-u8* g_heap_gsp                  = nullptr;   ///< GSP heap (main memory)
+u8* g_heap_linear               = nullptr;   ///< Linear heap
 u8* g_vram                      = nullptr;   ///< Video memory (VRAM) pointer
 u8* g_shared_mem                = nullptr;   ///< Shared memory
 u8* g_kernel_mem;                              ///< Kernel memory
@@ -36,13 +36,13 @@ static u8* physical_kernel_mem;              ///< Kernel memory
 
 // We don't declare the IO region in here since its handled by other means.
 static MemoryView g_views[] = {
-    {&g_exefs_code, &physical_exefs_code, EXEFS_CODE_VADDR,       EXEFS_CODE_SIZE,    0},
-    {&g_vram,       &physical_vram,       VRAM_VADDR,             VRAM_SIZE,          0},
-    {&g_heap,       &physical_fcram,      HEAP_VADDR,             HEAP_SIZE,          MV_IS_PRIMARY_RAM},
-    {&g_shared_mem, &physical_shared_mem, SHARED_MEMORY_VADDR,    SHARED_MEMORY_SIZE, 0},
-    {&g_system_mem, &physical_system_mem, SYSTEM_MEMORY_VADDR,    SYSTEM_MEMORY_SIZE,    0},
-    {&g_kernel_mem, &physical_kernel_mem, KERNEL_MEMORY_VADDR,    KERNEL_MEMORY_SIZE, 0},
-    {&g_heap_gsp,   &physical_heap_gsp,   HEAP_GSP_VADDR,         HEAP_GSP_SIZE,      0},
+    {&g_exefs_code,     &physical_exefs_code,   EXEFS_CODE_VADDR,       EXEFS_CODE_SIZE,    0},
+    {&g_vram,           &physical_vram,         VRAM_VADDR,             VRAM_SIZE,          0},
+    {&g_heap,           &physical_fcram,        HEAP_VADDR,             HEAP_SIZE,          MV_IS_PRIMARY_RAM},
+    {&g_shared_mem,     &physical_shared_mem,   SHARED_MEMORY_VADDR,    SHARED_MEMORY_SIZE, 0},
+    {&g_system_mem,     &physical_system_mem,   SYSTEM_MEMORY_VADDR,    SYSTEM_MEMORY_SIZE, 0},
+    {&g_kernel_mem,     &physical_kernel_mem,   KERNEL_MEMORY_VADDR,    KERNEL_MEMORY_SIZE, 0},
+    {&g_heap_linear,    &physical_heap_gsp,     HEAP_LINEAR_VADDR,      HEAP_LINEAR_SIZE,   0},
 };
 
 /*static MemoryView views[] =
diff --git a/src/core/mem_map.h b/src/core/mem_map.h
index f17afb60d3..7b750f8488 100644
--- a/src/core/mem_map.h
+++ b/src/core/mem_map.h
@@ -57,11 +57,11 @@ enum : u32 {
     HEAP_VADDR              = 0x08000000,
     HEAP_VADDR_END          = (HEAP_VADDR + HEAP_SIZE),
 
-    HEAP_GSP_SIZE           = 0x02000000,   ///< GSP heap size... TODO: Define correctly?
-    HEAP_GSP_VADDR          = 0x14000000,
-    HEAP_GSP_VADDR_END      = (HEAP_GSP_VADDR + HEAP_GSP_SIZE),
-    HEAP_GSP_PADDR          = 0x00000000,
-    HEAP_GSP_PADDR_END      = (HEAP_GSP_PADDR + HEAP_GSP_SIZE),
+    HEAP_LINEAR_SIZE        = 0x08000000,   ///< Linear heap size... TODO: Define correctly?
+    HEAP_LINEAR_VADDR       = 0x14000000,
+    HEAP_LINEAR_VADDR_END   = (HEAP_LINEAR_VADDR + HEAP_LINEAR_SIZE),
+    HEAP_LINEAR_PADDR       = 0x00000000,
+    HEAP_LINEAR_PADDR_END   = (HEAP_LINEAR_PADDR + HEAP_LINEAR_SIZE),
 
     HARDWARE_IO_SIZE        = 0x01000000,
     HARDWARE_IO_PADDR       = 0x10000000,                       ///< IO physical address start
@@ -112,7 +112,7 @@ extern u8 *g_base;
 // These are guaranteed to point to "low memory" addresses (sub-32-bit).
 // 64-bit: Pointers to low-mem (sub-0x10000000) mirror
 // 32-bit: Same as the corresponding physical/virtual pointers.
-extern u8* g_heap_gsp;      ///< GSP heap (main memory)
+extern u8* g_heap_linear;   ///< Linear heap (main memory)
 extern u8* g_heap;          ///< Application heap (main memory)
 extern u8* g_vram;          ///< Video memory (VRAM)
 extern u8* g_shared_mem;    ///< Shared memory
@@ -159,7 +159,7 @@ u32 MapBlock_Heap(u32 size, u32 operation, u32 permissions);
  * @param operation Memory map operation type
  * @param permissions Control memory permissions
  */
-u32 MapBlock_HeapGSP(u32 size, u32 operation, u32 permissions);
+u32 MapBlock_HeapLinear(u32 size, u32 operation, u32 permissions);
 
 inline const char* GetCharPointer(const VAddr address) {
     return (const char *)GetPointer(address);
diff --git a/src/core/mem_map_funcs.cpp b/src/core/mem_map_funcs.cpp
index 1887bcedb4..b78821a3bc 100644
--- a/src/core/mem_map_funcs.cpp
+++ b/src/core/mem_map_funcs.cpp
@@ -13,7 +13,7 @@
 namespace Memory {
 
 static std::map<u32, MemoryBlock> heap_map;
-static std::map<u32, MemoryBlock> heap_gsp_map;
+static std::map<u32, MemoryBlock> heap_linear_map;
 static std::map<u32, MemoryBlock> shared_map;
 
 /// Convert a physical address to virtual address
@@ -67,9 +67,9 @@ inline void Read(T &var, const VAddr vaddr) {
     } else if ((vaddr >= EXEFS_CODE_VADDR)  && (vaddr < EXEFS_CODE_VADDR_END)) {
         var = *((const T*)&g_exefs_code[vaddr - EXEFS_CODE_VADDR]);
 
-    // FCRAM - GSP heap
-    } else if ((vaddr >= HEAP_GSP_VADDR) && (vaddr < HEAP_GSP_VADDR_END)) {
-        var = *((const T*)&g_heap_gsp[vaddr - HEAP_GSP_VADDR]);
+    // FCRAM - linear heap
+    } else if ((vaddr >= HEAP_LINEAR_VADDR) && (vaddr < HEAP_LINEAR_VADDR_END)) {
+        var = *((const T*)&g_heap_linear[vaddr - HEAP_LINEAR_VADDR]);
 
     // FCRAM - application heap
     } else if ((vaddr >= HEAP_VADDR)  && (vaddr < HEAP_VADDR_END)) {
@@ -112,9 +112,9 @@ inline void Write(const VAddr vaddr, const T data) {
     } else if ((vaddr >= EXEFS_CODE_VADDR)  && (vaddr < EXEFS_CODE_VADDR_END)) {
         *(T*)&g_exefs_code[vaddr - EXEFS_CODE_VADDR] = data;
 
-    // FCRAM - GSP heap
-    } else if ((vaddr >= HEAP_GSP_VADDR)  && (vaddr < HEAP_GSP_VADDR_END)) {
-        *(T*)&g_heap_gsp[vaddr - HEAP_GSP_VADDR] = data;
+    // FCRAM - linear heap
+    } else if ((vaddr >= HEAP_LINEAR_VADDR)  && (vaddr < HEAP_LINEAR_VADDR_END)) {
+        *(T*)&g_heap_linear[vaddr - HEAP_LINEAR_VADDR] = data;
 
     // FCRAM - application heap
     } else if ((vaddr >= HEAP_VADDR)  && (vaddr < HEAP_VADDR_END)) {
@@ -154,9 +154,9 @@ u8 *GetPointer(const VAddr vaddr) {
     } else if ((vaddr >= EXEFS_CODE_VADDR)  && (vaddr < EXEFS_CODE_VADDR_END)) {
         return g_exefs_code + (vaddr - EXEFS_CODE_VADDR);
 
-    // FCRAM - GSP heap
-    } else if ((vaddr >= HEAP_GSP_VADDR)  && (vaddr < HEAP_GSP_VADDR_END)) {
-        return g_heap_gsp + (vaddr - HEAP_GSP_VADDR);
+    // FCRAM - linear heap
+    } else if ((vaddr >= HEAP_LINEAR_VADDR)  && (vaddr < HEAP_LINEAR_VADDR_END)) {
+        return g_heap_linear + (vaddr - HEAP_LINEAR_VADDR);
 
     // FCRAM - application heap
     } else if ((vaddr >= HEAP_VADDR)  && (vaddr < HEAP_VADDR_END)) {
@@ -204,24 +204,24 @@ u32 MapBlock_Heap(u32 size, u32 operation, u32 permissions) {
 }
 
 /**
- * Maps a block of memory on the GSP heap
+ * Maps a block of memory on the linear heap
  * @param size Size of block in bytes
  * @param operation Memory map operation type
  * @param flags Memory allocation flags
  */
-u32 MapBlock_HeapGSP(u32 size, u32 operation, u32 permissions) {
+u32 MapBlock_HeapLinear(u32 size, u32 operation, u32 permissions) {
     MemoryBlock block;
 
-    block.base_address  = HEAP_GSP_VADDR;
+    block.base_address  = HEAP_LINEAR_VADDR;
     block.size          = size;
     block.operation     = operation;
     block.permissions   = permissions;
 
-    if (heap_gsp_map.size() > 0) {
-        const MemoryBlock last_block = heap_gsp_map.rbegin()->second;
+    if (heap_linear_map.size() > 0) {
+        const MemoryBlock last_block = heap_linear_map.rbegin()->second;
         block.address = last_block.address + last_block.size;
     }
-    heap_gsp_map[block.GetVirtualAddress()] = block;
+    heap_linear_map[block.GetVirtualAddress()] = block;
 
     return block.GetVirtualAddress();
 }
diff --git a/src/video_core/pica.h b/src/video_core/pica.h
index 8bac178caf..4c3791ad9f 100644
--- a/src/video_core/pica.h
+++ b/src/video_core/pica.h
@@ -116,7 +116,7 @@ struct Regs {
         u32 address;
 
         u32 GetPhysicalAddress() const {
-            return DecodeAddressRegister(address) - Memory::FCRAM_PADDR + Memory::HEAP_GSP_VADDR;
+            return DecodeAddressRegister(address) - Memory::FCRAM_PADDR + Memory::HEAP_LINEAR_VADDR;
         }
 
         // texture1 and texture2 store the texture format directly after the address
@@ -312,7 +312,7 @@ struct Regs {
 
         inline u32 GetBaseAddress() const {
             // TODO: Ugly, should fix PhysicalToVirtualAddress instead
-            return DecodeAddressRegister(base_address) - Memory::FCRAM_PADDR + Memory::HEAP_GSP_VADDR;
+            return DecodeAddressRegister(base_address) - Memory::FCRAM_PADDR + Memory::HEAP_LINEAR_VADDR;
         }
 
         // Descriptor for internal vertex attributes

From 5bac72282a340ca30e19efe2cdf6e48699d7ebfd Mon Sep 17 00:00:00 2001
From: bunnei <bunneidev@gmail.com>
Date: Thu, 11 Dec 2014 23:34:55 -0500
Subject: [PATCH 2/3] Common: Add "sysdata" to GetUserPath and cleanup.

---
 src/common/common_paths.h | 14 +-------------
 src/common/file_util.cpp  | 14 +-------------
 src/common/file_util.h    |  1 +
 3 files changed, 3 insertions(+), 26 deletions(-)

diff --git a/src/common/common_paths.h b/src/common/common_paths.h
index ae08d082a3..95479a529c 100644
--- a/src/common/common_paths.h
+++ b/src/common/common_paths.h
@@ -29,19 +29,6 @@
     #endif
 #endif
 
-// Shared data dirs (Sys and shared User for linux)
-#ifdef _WIN32
-    #define SYSDATA_DIR "sys"
-#else
-    #ifdef DATA_DIR
-        #define SYSDATA_DIR DATA_DIR "sys"
-        #define SHARED_USER_DIR  DATA_DIR USERDATA_DIR DIR_SEP
-    #else
-        #define SYSDATA_DIR "sys"
-        #define SHARED_USER_DIR  ROOT_DIR DIR_SEP USERDATA_DIR DIR_SEP
-    #endif
-#endif
-
 // Dirs in both User and Sys
 #define EUR_DIR "EUR"
 #define USA_DIR "USA"
@@ -53,6 +40,7 @@
 #define MAPS_DIR          "maps"
 #define CACHE_DIR         "cache"
 #define SDMC_DIR          "sdmc"
+#define SYSDATA_DIR       "sysdata"
 #define SHADERCACHE_DIR   "shader_cache"
 #define STATESAVES_DIR    "state_saves"
 #define SCREENSHOTS_DIR   "screenShots"
diff --git a/src/common/file_util.cpp b/src/common/file_util.cpp
index 6c4860503d..7579d8c0f9 100644
--- a/src/common/file_util.cpp
+++ b/src/common/file_util.cpp
@@ -676,6 +676,7 @@ const std::string& GetUserPath(const unsigned int DirIDX, const std::string &new
         paths[D_MAPS_IDX]           = paths[D_USER_IDX] + MAPS_DIR DIR_SEP;
         paths[D_CACHE_IDX]          = paths[D_USER_IDX] + CACHE_DIR DIR_SEP;
         paths[D_SDMC_IDX]           = paths[D_USER_IDX] + SDMC_DIR DIR_SEP;
+        paths[D_SYSDATA_IDX]        = paths[D_USER_IDX] + SYSDATA_DIR DIR_SEP;
         paths[D_SHADERCACHE_IDX]    = paths[D_USER_IDX] + SHADERCACHE_DIR DIR_SEP;
         paths[D_SHADERS_IDX]        = paths[D_USER_IDX] + SHADERS_DIR DIR_SEP;
         paths[D_STATESAVES_IDX]     = paths[D_USER_IDX] + STATESAVES_DIR DIR_SEP;
@@ -753,19 +754,6 @@ const std::string& GetUserPath(const unsigned int DirIDX, const std::string &new
     return paths[DirIDX];
 }
 
-//std::string GetThemeDir(const std::string& theme_name)
-//{
-//    std::string dir = FileUtil::GetUserPath(D_THEMES_IDX) + theme_name + "/";
-//
-//#if !defined(_WIN32)
-//    // If theme does not exist in user's dir load from shared directory
-//    if (!FileUtil::Exists(dir))
-//        dir = SHARED_USER_DIR THEMES_DIR "/" + theme_name + "/";
-//#endif
-//
-//    return dir;
-//}
-
 size_t WriteStringToFile(bool text_file, const std::string &str, const char *filename)
 {
     return FileUtil::IOFile(filename, text_file ? "w" : "wb").WriteBytes(str.data(), str.size());
diff --git a/src/common/file_util.h b/src/common/file_util.h
index beaf7174a9..a9d48cfe8a 100644
--- a/src/common/file_util.h
+++ b/src/common/file_util.h
@@ -27,6 +27,7 @@ enum {
     D_STATESAVES_IDX,
     D_SCREENSHOTS_IDX,
     D_SDMC_IDX,
+    D_SYSDATA_IDX,
     D_HIRESTEXTURES_IDX,
     D_DUMP_IDX,
     D_DUMPFRAMES_IDX,

From 6fe61d3debff9da8df7c2422edf426045b87d23b Mon Sep 17 00:00:00 2001
From: bunnei <bunneidev@gmail.com>
Date: Wed, 26 Nov 2014 15:00:51 -0500
Subject: [PATCH 3/3] APT_U: Added GetSharedFont service function.

---
 src/common/common_paths.h      |   3 +
 src/core/hle/service/apt_u.cpp | 134 ++++++++++++++++++++++++---------
 2 files changed, 103 insertions(+), 34 deletions(-)

diff --git a/src/common/common_paths.h b/src/common/common_paths.h
index 95479a529c..42e1a29c10 100644
--- a/src/common/common_paths.h
+++ b/src/common/common_paths.h
@@ -58,6 +58,9 @@
 #define DEBUGGER_CONFIG   "debugger.ini"
 #define LOGGER_CONFIG     "logger.ini"
 
+// Sys files
+#define SHARED_FONT       "shared_font.bin"
+
 // Files in the directory returned by GetUserPath(D_LOGS_IDX)
 #define MAIN_LOG "emu.log"
 
diff --git a/src/core/hle/service/apt_u.cpp b/src/core/hle/service/apt_u.cpp
index 4bb05ce407..181763724f 100644
--- a/src/core/hle/service/apt_u.cpp
+++ b/src/core/hle/service/apt_u.cpp
@@ -4,10 +4,12 @@
 
 
 #include "common/common.h"
+#include "common/file_util.h"
 
 #include "core/hle/hle.h"
 #include "core/hle/kernel/event.h"
 #include "core/hle/kernel/mutex.h"
+#include "core/hle/kernel/shared_memory.h"
 #include "apt_u.h"
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -15,7 +17,19 @@
 
 namespace APT_U {
 
+// Address used for shared font (as observed on HW)
+// TODO(bunnei): This is the hard-coded address where we currently dump the shared font from via
+// https://github.com/citra-emu/3dsutils. This is technically a hack, and will not work at any
+// address other than 0x18000000 due to internal pointers in the shared font dump that would need to
+// be relocated. This might be fixed by dumping the shared font @ address 0x00000000 and then
+// correctly mapping it in Citra, however we still do not understand how the mapping is determined.
+static const VAddr SHARED_FONT_VADDR = 0x18000000;
+
+// Handle to shared memory region designated to for shared system font
+static Handle shared_font_mem = 0;
+
 static Handle lock_handle = 0;
+static std::vector<u8> shared_font;
 
 /// Signals used by APT functions
 enum class SignalType : u32 {
@@ -84,18 +98,18 @@ void InquireNotification(Service::Interface* self) {
  * state so that this command will return an error if this command is used again if parameters were
  * not set again. This is called when the second Initialize event is triggered. It returns a signal
  * type indicating why it was triggered.
- * Inputs:
- * 1 : AppID
- * 2 : Parameter buffer size, max size is 0x1000
- * Outputs:
- * 1 : Result of function, 0 on success, otherwise error code
- * 2 : Unknown, for now assume AppID of the process which sent these parameters
- * 3 : Unknown, for now assume Signal type
- * 4 : Actual parameter buffer size, this is <= to the the input size
- * 5 : Value
- * 6 : Handle from the source process which set the parameters, likely used for shared memory
- * 7 : Size
- * 8 : Output parameter buffer ptr
+ *  Inputs:
+ *      1 : AppID
+ *      2 : Parameter buffer size, max size is 0x1000
+ *  Outputs:
+ *      1 : Result of function, 0 on success, otherwise error code
+ *      2 : Unknown, for now assume AppID of the process which sent these parameters
+ *      3 : Unknown, for now assume Signal type
+ *      4 : Actual parameter buffer size, this is <= to the the input size
+ *      5 : Value
+ *      6 : Handle from the source process which set the parameters, likely used for shared memory
+ *      7 : Size
+ *      8 : Output parameter buffer ptr
  */
 void ReceiveParameter(Service::Interface* self) {
     u32* cmd_buff = Service::GetCommandBuffer();
@@ -115,18 +129,18 @@ void ReceiveParameter(Service::Interface* self) {
  * APT_U::GlanceParameter service function. This is exactly the same as APT_U::ReceiveParameter
  * (except for the word value prior to the output handle), except this will not clear the flag
  * (except when responseword[3]==8 || responseword[3]==9) in NS state.
- * Inputs:
- * 1 : AppID
- * 2 : Parameter buffer size, max size is 0x1000
- * Outputs:
- * 1 : Result of function, 0 on success, otherwise error code
- * 2 : Unknown, for now assume AppID of the process which sent these parameters
- * 3 : Unknown, for now assume Signal type
- * 4 : Actual parameter buffer size, this is <= to the the input size
- * 5 : Value
- * 6 : Handle from the source process which set the parameters, likely used for shared memory
- * 7 : Size
- * 8 : Output parameter buffer ptr
+ *  Inputs:
+ *      1 : AppID
+ *      2 : Parameter buffer size, max size is 0x1000
+ *  Outputs:
+ *      1 : Result of function, 0 on success, otherwise error code
+ *      2 : Unknown, for now assume AppID of the process which sent these parameters
+ *      3 : Unknown, for now assume Signal type
+ *      4 : Actual parameter buffer size, this is <= to the the input size
+ *      5 : Value
+ *      6 : Handle from the source process which set the parameters, likely used for shared memory
+ *      7 : Size
+ *      8 : Output parameter buffer ptr
  */
 void GlanceParameter(Service::Interface* self) {
     u32* cmd_buff = Service::GetCommandBuffer();
@@ -146,14 +160,14 @@ void GlanceParameter(Service::Interface* self) {
 
 /**
  * APT_U::AppletUtility service function
- * Inputs:
- * 1 : Unknown, but clearly used for something
- * 2 : Buffer 1 size (purpose is unknown)
- * 3 : Buffer 2 size (purpose is unknown)
- * 5 : Buffer 1 address (purpose is unknown)
- * 65 : Buffer 2 address (purpose is unknown)
- * Outputs:
- * 1 : Result of function, 0 on success, otherwise error code
+ *  Inputs:
+ *      1 : Unknown, but clearly used for something
+ *      2 : Buffer 1 size (purpose is unknown)
+ *      3 : Buffer 2 size (purpose is unknown)
+ *      5 : Buffer 1 address (purpose is unknown)
+ *      65 : Buffer 2 address (purpose is unknown)
+ *  Outputs:
+ *      1 : Result of function, 0 on success, otherwise error code
  */
 void AppletUtility(Service::Interface* self) {
     u32* cmd_buff = Service::GetCommandBuffer();
@@ -172,6 +186,34 @@ void AppletUtility(Service::Interface* self) {
              buffer1_addr, buffer2_addr);
 }
 
+/**
+ * APT_U::GetSharedFont service function
+ *  Outputs:
+ *      1 : Result of function, 0 on success, otherwise error code
+ *      2 : Virtual address of where shared font will be loaded in memory
+ *      4 : Handle to shared font memory
+ */
+void GetSharedFont(Service::Interface* self) {
+    DEBUG_LOG(KERNEL, "called");
+
+    u32* cmd_buff = Service::GetCommandBuffer();
+
+    if (!shared_font.empty()) {
+        // TODO(bunnei): This function shouldn't copy the shared font every time it's called.
+        // Instead, it should probably map the shared font as RO memory. We don't currently have
+        // an easy way to do this, but the copy should be sufficient for now.
+        memcpy(Memory::GetPointer(SHARED_FONT_VADDR), shared_font.data(), shared_font.size());
+
+        cmd_buff[0] = 0x00440082;
+        cmd_buff[1] = 0; // No error
+        cmd_buff[2] = SHARED_FONT_VADDR;
+        cmd_buff[4] = shared_font_mem;
+    } else {
+        cmd_buff[1] = -1; // Generic error (not really possible to verify this on hardware)
+        ERROR_LOG(KERNEL, "called, but %s has not been loaded!", SHARED_FONT);
+    }
+}
+
 const Interface::FunctionInfo FunctionTable[] = {
     {0x00010040, GetLockHandle,         "GetLockHandle"},
     {0x00020080, Initialize,            "Initialize"},
@@ -240,7 +282,7 @@ const Interface::FunctionInfo FunctionTable[] = {
     {0x00410040, nullptr,               "ReceiveCaptureBufferInfo"},
     {0x00420080, nullptr,               "SleepSystem"},
     {0x00430040, nullptr,               "NotifyToWait"},
-    {0x00440000, nullptr,               "GetSharedFont"},
+    {0x00440000, GetSharedFont,         "GetSharedFont"},
     {0x00450040, nullptr,               "GetWirelessRebootInfo"},
     {0x00460104, nullptr,               "Wrap"},
     {0x00470104, nullptr,               "Unwrap"},
@@ -259,9 +301,33 @@ const Interface::FunctionInfo FunctionTable[] = {
 // Interface class
 
 Interface::Interface() {
-    Register(FunctionTable, ARRAY_SIZE(FunctionTable));
+    // Load the shared system font (if available).
+    // The expected format is a decrypted, uncompressed BCFNT file with the 0x80 byte header
+    // generated by the APT:U service. The best way to get is by dumping it from RAM. We've provided
+    // a homebrew app to do this: https://github.com/citra-emu/3dsutils. Put the resulting file
+    // "shared_font.bin" in the Citra "sysdata" directory.
+
+    shared_font.clear();
+    std::string filepath = FileUtil::GetUserPath(D_SYSDATA_IDX) + SHARED_FONT;
+
+    FileUtil::CreateFullPath(filepath); // Create path if not already created
+    FileUtil::IOFile file(filepath, "rb");
+
+    if (file.IsOpen()) {
+        // Read shared font data
+        shared_font.resize(file.GetSize());
+        file.ReadBytes(shared_font.data(), file.GetSize());
+
+        // Create shared font memory object
+        shared_font_mem = Kernel::CreateSharedMemory("APT_U:shared_font_mem");
+    } else {
+        WARN_LOG(KERNEL, "Unable to load shared font: %s", filepath.c_str());
+        shared_font_mem = 0;
+    }
 
     lock_handle = 0;
+
+    Register(FunctionTable, ARRAY_SIZE(FunctionTable));
 }
 
 Interface::~Interface() {