diff --git a/toolbox/r.c b/toolbox/r.c
new file mode 100644
index 0000000..5a82e20
--- /dev/null
+++ b/toolbox/r.c
@@ -0,0 +1,74 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <string.h>
+
+static int usage()
+{
+    fprintf(stderr,"r [-b|-s] <address> [<value>]\n");
+    return -1;
+}
+
+int r_main(int argc, char *argv[])
+{
+    int width = 4, set = 0, fd;
+    unsigned addr, value;
+    void *page;
+    
+    if(argc < 2) return usage();
+
+    if(!strcmp(argv[1], "-b")) {
+        width = 1;
+        argc--;
+        argv++;
+    } else if(!strcmp(argv[1], "-s")) {
+        width = 2;
+        argc--;
+        argv++;
+    }
+
+    if(argc < 2) return usage();
+    addr = strtoul(argv[1], 0, 16);
+
+    if(argc > 2) {
+        set = 1;
+        value = strtoul(argv[2], 0, 16);
+    }
+
+    fd = open("/dev/mem", O_RDWR | O_SYNC);
+    if(fd < 0) {
+        fprintf(stderr,"cannot open /dev/mem\n");
+        return -1;
+    }
+    
+    page = mmap(0, 8192, PROT_READ | PROT_WRITE,
+                MAP_SHARED, fd, addr & (~4095));
+
+    if(page == MAP_FAILED){
+        fprintf(stderr,"cannot mmap region\n");
+        return -1;
+    }
+
+    switch(width){
+    case 4: {
+        unsigned *x = (unsigned*) (((unsigned) page) + (addr & 4095));
+        if(set) *x = value;
+        fprintf(stderr,"%08x: %08x\n", addr, *x);
+        break;
+    }
+    case 2: {
+        unsigned short *x = (unsigned short*) (((unsigned) page) + (addr & 4095));
+        if(set) *x = value;
+        fprintf(stderr,"%08x: %04x\n", addr, *x);
+        break;
+    }
+    case 1: {
+        unsigned char *x = (unsigned char*) (((unsigned) page) + (addr & 4095));
+        if(set) *x = value;
+        fprintf(stderr,"%08x: %02x\n", addr, *x);
+        break;
+    }
+    }    
+    return 0;
+}