Add types, enums and whatever to MCP_LoadFile patch

ios_mcp/source/mcp_loadfile.c

@@ -1,4 +1,58 @@
-int _MCP_LoadFile_patch(int arg1, int arg2, int arg3, int arg4, char arg5) {
-    int (*real_func)(int arg1, int arg2, int arg3, int arg4, char arg5) = (void*)0x0501CAA8 + 1; //thumb
-    return real_func(arg1, arg2, arg3, arg4, arg5);
+/* Patch for MCP_LoadFile (ioctl 0x53).
+ *
+ * Reference for most of the types and whatever:
+ * https://github.com/exjam/decaf-emu/tree/ios/src/libdecaf/src/ios/mcp
+ *
+ * This is a proof of concept, and shouldn't be used until it's cleaned up a bit.
+ * Co-authored by QuarkTheAwesome, exjam and Maschell
+ *
+ * Flow of calls:
+ * - kernel loads system libraries, app rpx or user calls OSDynLoad
+ * - goes to loader.elf, which will call ioctl 0x53
+ *   - with fileType = LOAD_FILE_CAFE_OS
+ *   - on failure, again with LOAD_FILE_PROCESS_CODE
+ *   - on failure, again with LOAD_FILE_SYS_DATA_CODE
+ * - each request routes here where we can do whatever
+ */
+
+#include "ipc_types.h"
+
+typedef enum {
+    //Load from the process's code directory (process title id)/code/%s
+    LOAD_FILE_PROCESS_CODE = 0,
+    //Load from the CafeOS directory (00050010-1000400A)/code/%s
+    LOAD_FILE_CAFE_OS = 1,
+    //Load from a system data title's content directory (0005001B-x)/content/%s
+    LOAD_FILE_SYS_DATA_CONTENT = 2,
+    //Load from a system data title's code directory (0005001B-x)/content/%s
+    LOAD_FILE_SYS_DATA_CODE = 3,
+} MCPFileType;
+
+typedef struct {
+    unsigned char unk[0x10];
+
+    unsigned int pos;
+    MCPFileType type;
+    unsigned int cafe_pid;
+
+    unsigned char unk2[0xC];
+
+    char name[0x40];
+
+    unsigned char unk3[0x12D8 - 0x68];
+} __attribute__((packed)) MCPLoadFileRequest;
+//sizeof(MCPLoadFileRequest) = 0x12D8
+
+int (*const real_MCP_LoadFile)(ipcmessage* msg) = (void*)0x0501CAA8 + 1; //+1 for thumb
+
+int _MCP_LoadFile_patch(ipcmessage* msg) {
+    if (msg->ioctl.length_in > 0 /*TODO log this and verify it's 0x12D8*/) {
+        MCPLoadFileRequest* request = (MCPLoadFileRequest*)msg->ioctl.buffer_in;
+    /*  loader.elf tries this value first */
+        if (request->type == LOAD_FILE_CAFE_OS) {
+        /*  Your code here */
+        }
+    }
+    
+    return real_MCP_LoadFile(msg);
 }