diff --git a/Common/printk.c b/Common/printk.c
new file mode 100644
index 0000000..10fbfde
--- /dev/null
+++ b/Common/printk.c
@@ -0,0 +1,385 @@
+/*
+ *
+ * printk.c
+ *
+ * printk for bootbox
+ *
+ * support format:
+ *  %c
+ *  %s
+ *  %[[0]n]x
+ *  %[[0]n]X
+ *  %[[0]n]d
+ *
+ */
+
+#include <pspsdk.h>
+#include <pspkernel.h>
+#include <pspdebug.h>
+#include <pspdisplay.h>
+#include <pspiofilemgr.h>
+
+#include <stdarg.h>
+#include <string.h>
+
+struct pthread_mlock_t {
+	volatile unsigned long l;
+	unsigned int c;
+	int thread_id;
+};
+
+typedef struct pthread_mlock_t MLOCK_T;
+
+static MLOCK_T lock;
+
+extern void printk_lock(void);
+extern void printk_unlock(void);
+
+static int itostr(char *buf, int in_data, int base, int upper, int sign)
+{
+	int res, len, i;
+	unsigned int data;
+	char *str;
+
+	if(base==10 && sign && in_data<0){
+		data = -in_data;
+	}else{
+		data = in_data;
+	}
+
+	str = buf;
+	do{
+		res = data%base;
+		data = data/base;
+		if(res<10){
+			res += '0';
+		}else{
+			if(upper){
+				res += 'A'-10;
+			}else{
+				res += 'a'-10;
+			}
+		}
+		*str++ = res;
+	}while(data);
+	len = str-buf;
+
+	/* reverse digital order */
+	for(i=0; i<len/2; i++){
+		res = buf[i];
+		buf[i] = buf[len-1-i]; 
+		buf[len-1-i] = res; 
+	}
+
+	return len;
+}
+
+/*
+ * vsnprintf - Format a string and place it in a buffer
+ * @buf: The buffer to place the result into
+ * @size: The size of the buffer, including the trailing null space
+ * @fmt: The format string to use
+ * @args: Arguments for the format string
+ */
+
+#define OUT_C(c) \
+	if(str<end){ \
+		*str++ = (c); \
+	}
+
+static char digital_buf[32];
+int vsnprintf(char *buf, int size, char *fmt, va_list args)
+{
+	char ch, *s, *str, *end, *sstr;
+	int zero_pad, left_adj, add_sign, field_width, sign;
+	int i, base, upper, len;
+
+
+	if(!buf || !fmt ||!size){
+		return 0;
+	}
+
+	str = buf;
+	end = buf+size;
+
+	while(*fmt){
+		if(*fmt!='%'){
+			OUT_C(*fmt++);
+			continue;
+		}
+
+		/* skip '%' */
+		sstr = fmt;
+		fmt++;
+
+		/* %% */
+		if(*fmt=='%'){
+			OUT_C(*fmt++);
+			continue;
+		}
+
+		/* get flag */
+		zero_pad = ' ';
+		left_adj = 0;
+		add_sign = 0;
+		while((ch=*fmt)){
+
+			if(*fmt=='0'){
+				zero_pad = '0';
+			}else if(*fmt=='-'){
+				left_adj = 1;
+			}else if(*fmt=='#'){
+			}else if(*fmt==' '){
+				if(add_sign!='+')
+					add_sign = ' ';
+			}else if(*fmt=='+'){
+				add_sign = '+';
+			}else{
+				break;
+			}
+			fmt++;
+		}
+
+		/* get field width: m.n */
+		field_width = 0;
+		/* get m */
+		while(*fmt && *fmt>'0' && *fmt<='9'){
+			field_width = field_width*10+(*fmt-'0');
+			fmt++;
+		}
+		if(*fmt && *fmt=='.'){
+			fmt++;
+			/* skip n */
+			while(*fmt && *fmt>'0' && *fmt<='9'){
+				fmt++;
+			}
+		}
+
+		/* get format char */
+		upper = 0;
+		base = 0;
+		sign = 0;
+		len = 0;
+		s = digital_buf;
+		while((ch=*fmt)){
+			fmt++;
+			switch(ch){
+			/* hexadecimal */
+			case 'p':
+			case 'X':
+				upper = 1;
+			case 'x':
+				base = 16;
+				break;
+
+			/* decimal */
+			case 'd':
+			case 'i':
+				sign = 1;
+			case 'u':
+				base = 10;
+				break;
+
+			/* octal */
+			case 'o':
+				base = 8;
+				break;
+
+			/* character */
+			case 'c':
+				digital_buf[0] = (unsigned char) va_arg(args, int);
+				len = 1;
+				break;
+
+			/* string */
+			case 's':
+				s = va_arg(args, char *);
+				if(!s) s = "<NUL>";
+				len = strlen(s);
+				break;
+
+			/* float format, skip it */
+			case 'e': case 'E': case 'f': case 'F': case 'g': case 'G': case 'a': case 'A':
+				va_arg(args, double);
+				s = NULL;
+				break;
+
+			/* length modifier */
+			case 'l': case 'L': case 'h': case 'j': case 'z': case 't':
+				/* skip it */
+				continue;
+
+			/* bad format */
+			default:
+				s = sstr;
+				len = fmt-sstr;
+				break;
+			}
+			break;
+		}
+
+		if(base){
+			i = va_arg(args, int);
+			if(base==10 && sign){
+				if(i<0){
+					add_sign = '-';
+				}
+			}else{
+				add_sign = 0;
+			}
+
+			len = itostr(digital_buf, i, base, upper, sign);
+		}else{
+			zero_pad = ' ';
+			add_sign = 0;
+		}
+
+		if(s){
+			if(len>=field_width){
+				field_width = len;
+				if(add_sign)
+					field_width++;
+			}
+			for(i=0; i<field_width; i++){
+				if(left_adj){
+					if(i<len){
+						OUT_C(*s++);
+					}else{
+						OUT_C(' ');
+					}
+				}else{
+					if(add_sign && (zero_pad=='0' || i==(field_width-len-1))){
+						OUT_C(add_sign);
+						add_sign = 0;
+						continue;
+					}
+					if(i<(field_width-len)){
+						OUT_C(zero_pad);
+					}else{
+						OUT_C(*s++);
+					}
+				}
+			}
+		}
+	}
+
+	OUT_C(0);
+	return str-buf;
+}
+
+static char printk_buf[128];
+
+static char printk_memory_log[2048];
+static char *printk_memory_log_ptr = printk_memory_log;
+
+int printk(char *fmt, ...)
+{
+	va_list args;
+	int printed_len;
+	int kout;
+
+	printk_lock();
+	va_start(args, fmt);
+	printed_len = vsnprintf(printk_buf, sizeof(printk_buf), fmt, args);
+	va_end(args);
+	printed_len--;
+
+	kout = sceKernelStdout();
+	sceIoWrite(kout, printk_buf, printed_len);
+
+	if ( 1 ) {
+		int fd;
+
+		fd = sceIoOpen("ms0:/LOG_SCTL.TXT", PSP_O_WRONLY | PSP_O_CREAT | PSP_O_APPEND, 0777);
+
+		if(fd < 0) {
+			fd = sceIoOpen("ef0:/LOG_SCTL.txt", PSP_O_WRONLY | PSP_O_CREAT | PSP_O_APPEND, 0777);
+		}
+
+		if (fd >= 0) {
+			if (printk_memory_log_ptr != printk_memory_log) {
+				// flush debug output
+				sceIoWrite(fd, printk_memory_log, printk_memory_log_ptr - printk_memory_log);
+				memset(printk_memory_log, 0, sizeof(printk_memory_log));
+				printk_memory_log_ptr = printk_memory_log;
+			}
+
+			sceIoWrite(fd, printk_buf, printed_len);
+			sceIoClose(fd);
+		} else {
+			// log to memory buf
+
+			if (printk_memory_log_ptr + printed_len < printk_memory_log + sizeof(printk_memory_log)) {
+				memcpy(printk_memory_log_ptr, printk_buf, printed_len);
+				printk_memory_log_ptr += printed_len;
+			}
+		}
+	}
+
+	sceKernelDelayThread(10000);
+	printk_unlock();
+
+	return printed_len;
+}
+
+static unsigned long my_InterlockedExchange(unsigned long volatile *dst, unsigned long exchange)
+{
+	unsigned int flags = pspSdkDisableInterrupts();
+	unsigned long origvalue = *dst;
+
+	*dst = exchange;
+	pspSdkEnableInterrupts(flags);
+
+	return origvalue;
+}
+
+static inline int psp_mutex_lock(MLOCK_T *s)
+{
+	for (;;) {
+		if (s->l != 0) {
+			if (s->thread_id == sceKernelGetThreadId()) {
+				++s->c;
+				return 0;
+			}
+		} else {
+			if (!my_InterlockedExchange(&s->l, 1)) {
+				s->thread_id = sceKernelGetThreadId();
+				s->c = 1;
+				return 0;
+			}
+		}
+
+		sceKernelDelayThread(1000);
+	}
+	
+	return 0;
+}
+
+static inline void psp_mutex_unlock(MLOCK_T *s)
+{
+	if (--s->c == 0) {
+		s->thread_id = 0;
+		my_InterlockedExchange(&s->l, 0);
+	}
+}
+
+void printk_lock(void)
+{
+	psp_mutex_lock(&lock);
+}
+
+void printk_unlock(void)
+{
+	psp_mutex_unlock(&lock);
+}
+
+int printk_init(void)
+{
+	MLOCK_T *s = &lock;
+
+	s->l = 0;
+	s->c = 0;
+	s->thread_id = sceKernelGetThreadId();
+
+	return 0;
+}
diff --git a/Common/printk.h b/Common/printk.h
new file mode 100644
index 0000000..b3944cb
--- /dev/null
+++ b/Common/printk.h
@@ -0,0 +1,17 @@
+#ifndef PRINTK_H
+#define PRINTK_H
+
+#ifdef DEBUG
+int printk_init(void);
+int printk(char *fmt, ...)__attribute__((format (printf, 1, 2)));
+int printk_lock(void);
+int printk_unlock(void);
+#else
+#define printk_init()
+#define printk(...)
+#define printk_lock()
+#define printk_unlock()
+#endif
+
+#endif
+