Trap guestOS to run SDL-oriented applications

README.md

@@ -80,6 +80,12 @@ $ make ENABLE_SYSTEM=1
 $ build/rv32emu -k <kernel_img_path> -i <rootfs_img_path>
 ```
 
+Build with a larger INITRD_SIZE (e.g., 64 MiB) to run SDL-oriented application because the default 8 MiB is insufficient for SDL-oriented application artifacts:
+```shell
+$ make system ENABLE_SYSTEM=1 ENABLE_SDL=1 INITRD_SIZE=64
+```
+Once login the guestOS, run `doom-riscv` or `quake` or `smolnes`. To terminate SDL-oriented applications, use the built-in exit utility, ctrl-c or the SDL window close button(X).
+
 #### Build Linux image
 An automated build script is provided to compile the RISC-V cross-compiler, Busybox, and Linux kernel from source. Please note that it only supports the Linux host environment. It can be found at tools/build-linux-image.sh.
 ```

src/devices/uart.c

@@ -12,7 +12,6 @@
 #include <unistd.h>
 
 #include "uart.h"
-
 /* Emulate 8250 (plain, without loopback mode support) */
 
 #define U8250_INTR_THRE 1
@@ -66,10 +65,22 @@ static uint8_t u8250_handle_in(u8250_state_t *uart)
     if (value == 1) {           /* start of heading (Ctrl-a) */
         if (getchar() == 120) { /* keyboard x */
             printf("\n");       /* end emulator with newline */
-            exit(0);
+            exit(EXIT_SUCCESS);
         }
     }
 
+#if RV32_HAS(SDL) && RV32_HAS(SYSTEM) && !RV32_HAS(ELF_LOADER)
+    /*
+     * The guestOS may repeatedly open and close the SDL window,
+     * and the user could close the application by pressing the ctrl-c key.
+     * Need to trap the ctrl-c key and ensure the SDL window and
+     * SDL mixer are destroyed properly.
+     */
+    extern void sdl_video_audio_cleanup();
+    if (value == 3) /* ctrl-c */
+        sdl_video_audio_cleanup();
+#endif
+
     return value;
 }
 

src/emulate.c

@@ -1299,7 +1299,22 @@ void ecall_handler(riscv_t *rv)
     syscall_handler(rv);
 #elif RV32_HAS(SYSTEM)
     if (rv->priv_mode == RV_PRIV_U_MODE) {
-        SET_CAUSE_AND_TVAL_THEN_TRAP(rv, ECALL_U, 0);
+        switch (rv_get_reg(
+            rv,
+            rv_reg_a7)) { /* trap guestOS's SDL-oriented application syscall */
+        case 0xBEEF:
+        case 0xC0DE:
+        case 0xFEED:
+        case 0xBABE:
+        case 0xD00D:
+        case 93:
+            syscall_handler(rv);
+            rv->PC += 4;
+            break;
+        default:
+            SET_CAUSE_AND_TVAL_THEN_TRAP(rv, ECALL_U, 0);
+            break;
+        }
     } else if (rv->priv_mode ==
                RV_PRIV_S_MODE) { /* trap to SBI syscall handler */
         rv->PC += 4;

src/syscall.c

@@ -132,9 +132,20 @@ static void syscall_write(riscv_t *rv)
     rv_set_reg(rv, rv_reg_a0, -1);
 }
 
-
 static void syscall_exit(riscv_t *rv)
 {
+#if RV32_HAS(SDL) && RV32_HAS(SYSTEM) && !RV32_HAS(ELF_LOADER)
+    /*
+     * The guestOS may repeatedly open and close the SDL window,
+     * and the user could close the application using the application’s
+     * built-in exit function. Need to trap the built-in exit and
+     * ensure the SDL window and SDL mixer are destroyed properly.
+     */
+    extern void sdl_video_audio_cleanup();
+    sdl_video_audio_cleanup();
+    return;
+#endif
+
     /* simply halt cpu and save exit code.
      * the application decides the usage of exit code
      */