Fix setup of usermode stack and added final system call to exit.

targets/_any/include/os/syscall.hpp

@@ -12,7 +12,8 @@ namespace baos
 enum class Syscall : std::uint64_t
 {
     FILE_READ = 0,
-    FILE_WRITE = 1
+    FILE_WRITE = 1,
+    EXIT = 0x3C
 };
 
 void setupSyscall() noexcept;

targets/_any/src/app/main.cpp

@@ -108,7 +108,7 @@ void cmdDumpPageTable() noexcept
 }
 }
 
-extern "C" void main()
+extern "C" void usermode_main()
 {
     std::string cmd;
     while(true)
@@ -132,6 +132,10 @@ extern "C" void main()
             cmdDumpPageTable();
             continue;
         }
+        else if (cmd == "exit")
+        {
+            return;
+        }
         std::printf("Unknown command: %s.\n", cmd.c_str());
     }
 }

targets/_any/src/os/syscall.cpp

@@ -46,5 +46,7 @@ extern "C" void __baosSyscall(baos::Syscall cmd, std::uint64_t param0, std::uint
         case Syscall::FILE_WRITE:
             sysFileWrite(static_cast<unsigned>(param0), std::bit_cast<const char*>(param1), param2);
             break;
+        case Syscall::EXIT:
+            break;
     }
 }