tag:www.local-guru.net,2005:/blog/tag/helloworld local-guru.net 2009-03-03T04:25:00+01:00 GuruBlog engine tag:www.local-guru.net,2005:Article/129 2009-03-03T04:25:00+01:00 2009-03-03T04:25:00+01:00 Nikolaus Gradwohl <p>motivated by my <a href="http://www.local-guru.net/blog/2009/02/25/machine-language-hello-world-in-120-bytes">hand written x86 machinecode</a>, i decided that i had to take it to the next level.</p> <p>i worte some handassembled java bytecode. run the file below as</p> <pre><code>./dump.sh &gt; HelloAsm </code></pre> <p>and run the programm with</p> <pre><code>java HelloAsm </code></pre> tag:www.local-guru.net,2005:Article/128 2009-02-25T05:37:00+01:00 2009-02-25T05:37:00+01:00 Nikolaus Gradwohl <p>a while ago i read the really cool <a href="http://lab16.axiosmedia.org/2009/02/programming-your-pdp-11-part-0/trackback/">tutorial on programming a pdp11</a>. after typing the "hello world" example into the simulator, i startet to search for instructions how to write the machine code for the pdp11 myself.</p> <p>after a while coding in raw octal numbers, i wanted to take it to the next level and searched for a way to write machine code by hand for my linux box</p> <p>So i downloaded <a href="http://developer.intel.com/design/pentiumii/manuals/243191.htm">Intel Architecture Software Developer's Manual, Volume 2: Instruction Set Reference Manual</a> and wrote a shell script that can be used to dump the raw machine code into a file. of course my dualcore-pentium-mega-bla processor in far more sophisticated than the pdp11 cpu was. so it can't be programmed in octal numbers - i used hexadezimal numbers :-)</p> <p>execute the shellscript and pipe it into a file</p> <pre><code>sh dump.sh &gt; hello </code></pre> <p>make it executable and - TATAAAA - a hello world programm in 120 bytes (including the elf header - which adds 80 bytes all by himself)</p> <pre><code># write a elf header in the file echo -ne "\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00" echo -ne "\x02\x00\x03\x00\x01\x00\x00\x00\x54\x80\x04\x08\x34\x00\x00\x00" echo -ne "\x80\x00\x00\x00\x00\x00\x00\x00\x34\x00\x20\x00\x01\x00\x28\x00" echo -ne "\x03\x00\x02\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x80\x04\x08" echo -ne "\x00\x80\x04\x08\x6f\x00\x00\x00\x6f\x00\x00\x00\x05\x00\x00\x00" echo -ne "\x00\x10\x00\x00" echo -ne "\x31\xc0" # clear eax echo -ne "\x50" # push 0 on the stack echo -ne "\x68rld\x0a" # push the string onto the stack in reverse order, 4 bytes a time echo -ne "\x68o Wo" echo -ne "\x68Hell" echo -ne "\x89\xe1" # move stackpointer to ecx ( the start of our string ) echo -ne "\xb0\x04" # move 4 to al ( eax is already 0 because auf line one ) echo -ne "\x33\xc3\xb3\x01" # xor ebx and move 1 to bl echo -ne "\x32\xc2\xb2\x0c" # xor edx and move 12 onto dl (length of the string ) echo -ne "\xcd\x80" # int 0x80 echo -ne "\xb0\x01" # move 1 into al echo -ne "\xcd\x80" # int 0x80 </code></pre>