diff --git a/VKernel/Kernel/drivers/usb/uhci.vp b/VKernel/Kernel/drivers/usb/uhci.vp
index 22e381c..298d2bc 100644
--- a/VKernel/Kernel/drivers/usb/uhci.vp
+++ b/VKernel/Kernel/drivers/usb/uhci.vp
@@ -7,6 +7,7 @@ import platform.pch.timer as timer
 import intr.idt as idt
 import platform.pch.pic as pic
 import drivers.usb.pci as pci
+import viperlib
 
 UHCI_USBCMD: t.CDefine = 0x00
 UHCI_USBSTS: t.CDefine = 0x02
@@ -253,6 +254,9 @@ def init(io_base: t.CUInt16T) -> t.CInt:
 
     serial.puts("[uhci] allocating frame list...\n")
     _frame_list = mm.malloc(UHCI_NUM_FRAMES * 4)
+    _dbg_fl: t.CArray[t.CChar, 96]
+    viperlib.snprintf(c.Addr(_dbg_fl), 96, "[dbg] frame_list ret=0x%lx\n", t.CUInt64T(_frame_list))
+    serial.puts(c.Addr(_dbg_fl))
     if _frame_list is None:
         serial.puts("[uhci] frame list alloc failed\n")
         return -2
diff --git a/VKernel/Kernel/services/desktop.vp b/VKernel/Kernel/services/desktop.vp
index 5494914..8a18d73 100644
--- a/VKernel/Kernel/services/desktop.vp
+++ b/VKernel/Kernel/services/desktop.vp
@@ -1856,6 +1856,9 @@ def start(fb_ptr: t.CVoid | t.CPtr, w: t.CInt, h: t.CInt, pitch: t.CInt = 0) ->
         return None
 
     _back_fb = mm.malloc(w * h * 4)
+    _dbg_bf: t.CArray[t.CChar, 96]
+    viperlib.snprintf(c.Addr(_dbg_bf), 96, "[dbg] back_fb ret=0x%lx w=%d h=%d\n", t.CUInt64T(_back_fb), w, h)
+    serial.puts(c.Addr(_dbg_bf))
     if _back_fb:
         string.memset(_back_fb, 0, w * h * 4)
     else:
@@ -1863,12 +1866,18 @@ def start(fb_ptr: t.CVoid | t.CPtr, w: t.CInt, h: t.CInt, pitch: t.CInt = 0) ->
         return None
 
     _row_buf = mm.malloc(w * 4)
+    _dbg_rb: t.CArray[t.CChar, 96]
+    viperlib.snprintf(c.Addr(_dbg_rb), 96, "[dbg] row_buf ret=0x%lx\n", t.CUInt64T(_row_buf))
+    serial.puts(c.Addr(_dbg_rb))
     if _row_buf:
         string.memset(_row_buf, 0, w * 4)
     else:
         serial.puts("[desktop] row_buf malloc FAILED!\n")
 
     _bg_row_buf = mm.malloc(w * 4)
+    _dbg_br: t.CArray[t.CChar, 96]
+    viperlib.snprintf(c.Addr(_dbg_br), 96, "[dbg] bg_row_buf ret=0x%lx\n", t.CUInt64T(_bg_row_buf))
+    serial.puts(c.Addr(_dbg_br))
     if _bg_row_buf:
         desktop_init_col: t.CUInt32T = gfx.COLOR_RGB(25, 25, 35)
         for ri in range(w):