Compiling ruby for linux running under another processor can be quite an adventure. Considering the limited setups you will find, not only small processing power and limited memory, I consider the building process to be the hardest nut to crack.

When cross-compiling ruby to run under a xscale arm SoC, I ran in a couple of road blocks, not all of them documented or easily found by googling around. I wanted a complete ruby distribution, including openssl and socket capabilities.

From the stock source distribution to a complete binary set, I had about 7 or 8 interations until reach a clean build. I still not satisfied with some workarounds, so I will let comments open to see if someone can come with a more elegant solution.

My cross-compiling environment was all setup, using arm-linux-gcc 3.x, a static openssl installation and ruby source code. Also, you will need a working ruby interpreter on the host machine, which will be used by ruby’s building system to generate makefiles and such.

Ruby’s building system can be fairly complex, and y ou may keep in mind that you wont be able to hack it so easily, as changing variables and parameters. The main config file for the entire build system is rbconfig.rb.

First, untar the source code for Ruby and apply the following patch. I’ve used ruby-1.8.6-p111.tar.gz, along with a static build of openssl-0.9.8g.tar.gz. The patch is needed because in the final linking part, ruby symbols will conflict with static openssl symbols of the same name.

Mainly, the digest module will cause problems. I think that in a runtime environment, these problems wont show up at linking time, but as I used a static library I had to rename these symbols. Basically, I put rb in front of them in ext/digest/sha2.c. The functions area: SHA256_Transform and SHA512_Transform.

So, after untar’ing the source code, apply the following patch using cd ext/Setup/digest ; cat sha2_static_openssl.patch | patch -p1 sha2.c.

— sha2-orig.c 2007-12-14 18:19:16.000000000 -0200
+++ sha2.c 2007-12-14 17:56:51.000000000 -0200
@@ -176,8 +176,8 @@
* only.
void SHA512_Last(SHA512_CTX*);
-void SHA256_Transform(SHA256_CTX*, const sha2_word32*);
-void SHA512_Transform(SHA512_CTX*, const sha2_word64*);
+void rb_SHA256_Transform(SHA256_CTX*, const sha2_word32*);
+void rb_SHA512_Transform(SHA512_CTX*, const sha2_word64*);

/*** SHA-XYZ INITIAL HASH VALUES AND CONSTANTS ************************/
@@ -329,7 +329,7 @@
(h) = T1 + Sigma0_256(a) + Maj((a), (b), (c)); \

-void SHA256_Transform(SHA256_CTX* context, const sha2_word32* data) {
+void rb_SHA256_Transform(SHA256_CTX* context, const sha2_word32* data) {
sha2_word32 a, b, c, d, e, f, g, h, s0, s1;
sha2_word32 T1, *W256;
int j;
@@ -387,7 +387,7 @@


-void SHA256_Transform(SHA256_CTX* context, const sha2_word32* data) {
+void rb_SHA256_Transform(SHA256_CTX* context, const sha2_word32* data) {
sha2_word32 a, b, c, d, e, f, g, h, s0, s1;
sha2_word32 T1, T2, *W256;
int j;
@@ -489,7 +489,7 @@
context->bitcount += freespace << 3;
len -= freespace;
data += freespace;
– SHA256_Transform(context, (sha2_word32*)context->buffer);
+ rb_SHA256_Transform(context, (sha2_word32*)context->buffer);
} else {
/* The buffer is not yet full */
MEMCPY_BCOPY(&context->buffer[usedspace], data, len);
@@ -501,7 +501,7 @@
while (len >= SHA256_BLOCK_LENGTH) {
/* Process as many complete blocks as we can */
– SHA256_Transform(context, (const sha2_word32*)data);
+ rb_SHA256_Transform(context, (const sha2_word32*)data);
context->bitcount += SHA256_BLOCK_LENGTH << 3;
data += SHA256_BLOCK_LENGTH;
@@ -541,7 +541,7 @@
MEMSET_BZERO(&context->buffer[usedspace], SHA256_BLOCK_LENGTH – usedspace);
/* Do second-to-last transform: */
– SHA256_Transform(context, (sha2_word32*)context->buffer);
+ rb_SHA256_Transform(context, (sha2_word32*)context->buffer);

/* And set-up for the last transform: */
@@ -557,7 +557,7 @@
*(sha2_word64*)&context->buffer[SHA256_SHORT_BLOCK_LENGTH] = context->bitcount;

/* Final transform: */
– SHA256_Transform(context, (sha2_word32*)context->buffer);
+ rb_SHA256_Transform(context, (sha2_word32*)context->buffer);

@@ -624,7 +624,7 @@
(h) = T1 + Sigma0_512(a) + Maj((a), (b), (c)); \

-void SHA512_Transform(SHA512_CTX* context, const sha2_word64* data) {
+void rb_SHA512_Transform(SHA512_CTX* context, const sha2_word64* data) {
sha2_word64 a, b, c, d, e, f, g, h, s0, s1;
sha2_word64 T1, *W512 = (sha2_word64*)context->buffer;
int j;
@@ -679,7 +679,7 @@


-void SHA512_Transform(SHA512_CTX* context, const sha2_word64* data) {
+void rb_SHA512_Transform(SHA512_CTX* context, const sha2_word64* data) {
sha2_word64 a, b, c, d, e, f, g, h, s0, s1;
sha2_word64 T1, T2, *W512 = (sha2_word64*)context->buffer;
int j;
@@ -779,7 +779,7 @@
ADDINC128(context->bitcount, freespace << 3);
len -= freespace;
data += freespace;
– SHA512_Transform(context, (const sha2_word64*)context->buffer);
+ rb_SHA512_Transform(context, (const sha2_word64*)context->buffer);
} else {
/* The buffer is not yet full */
MEMCPY_BCOPY(&context->buffer[usedspace], data, len);
@@ -791,7 +791,7 @@
while (len >= SHA512_BLOCK_LENGTH) {
/* Process as many complete blocks as we can */
– SHA512_Transform(context, (const sha2_word64*)data);
+ rb_SHA512_Transform(context, (const sha2_word64*)data);
ADDINC128(context->bitcount, SHA512_BLOCK_LENGTH << 3);
data += SHA512_BLOCK_LENGTH;
@@ -826,7 +826,7 @@
MEMSET_BZERO(&context->buffer[usedspace], SHA512_BLOCK_LENGTH – usedspace);
/* Do second-to-last transform: */
– SHA512_Transform(context, (const sha2_word64*)context->buffer);
+ rb_SHA512_Transform(context, (const sha2_word64*)context->buffer);

/* And set-up for the last transform: */
MEMSET_BZERO(context->buffer, SHA512_BLOCK_LENGTH – 2);
@@ -843,7 +843,7 @@
*(sha2_word64*)&context->buffer[SHA512_SHORT_BLOCK_LENGTH+8] = context->bitcount[0];

/* Final transform: */
– SHA512_Transform(context, (const sha2_word64*)context->buffer);
+ rb_SHA512_Transform(context, (const sha2_word64*)context->buffer);

void SHA512_Finish(SHA512_CTX* context, sha2_byte digest[]) {
Note that you only need this patch if you are using a static openssl lib. You will know if you need it in another situation if in the final part of the make process, the linker yield a message about symbol redefinition or symbol size changed. If the patch is messy, you may edit sha2.c and change the functions signature yourself, by pre-pending rb_ to their names and looking where they are used inside the same file.

Next step is selecting which extensions you want to build. Edit ext/Setup and uncomment what you want. As I am compiling everything static, I uncommented the following options: option nodynamic, all digest options, etc, fcntl, iconv, openssl, socket, stringio, strscan, syck, thread and zlib.

Run autoconf and the follwing script:

— —

export CC=/usr/local/arm-linux/bin/arm-linux-gcc
export LD=/usr/local/arm-linux/bin/arm-linux-gcc
export AR=/usr/local/arm-linux/bin/arm-linux-ar
export RANLIB=/usr/local/arm-linux/bin/arm-linux-ranlib

export ac_cv_func_getpgrp_void=yes
export ac_cv_func_setpgrp_void=yes

./configure –target=arm-linux –host=arm-linux –enable-wide-getaddrinfo –with-openssl-dir=/PATH/TO/OPENSSL/STATIC/INSTALLATION/usr

— end —

Besides setting up the target processor, there are some issues that show up when cross-compiling. One of these are set/getpgrp library functions which make your configure script fail. The other is a IPV6/getaddrinfo issue, which will make socket compilation fail. By using these environment variables and configure flags everything will build nice. Try them if you are stuck cross-compiling for other plataforms than arm.

After configure finish its job, run make and it should build to the end. Then, the trick part I want some input for a elegant way to do. If you setup –prefix when configuring to install in another PATH, the libraries path inside ruby will be registered to that PATH.

I wanted to install under /tmp to package the whole binary distribution and copy to my arm board, but the first time I issued a –prefix=/tmp, it would not load any require’d library inside source code. I ran ‘strings’ in the resulting ruby binary and saw that /tmp/lib was built-in the binary as the place to look for its stuff. Also, it was built on every helper script as irb, erb, ri, in the first line, to look for ruby in /tmp/bin. Definately a no-go.

Then I cleaned everything and rebuild without setting up the –prefix tag, and before issuing a make install, I checked into rbconfig.rb to see if there was something to do to help it. As a side note, when compiling for x86 path modifiers in configure worked as expected…

There was a variable called DESTDIR, so I decided to put /tmp there and see what happens. Well, it installed under /tmp and I managed to build a package to install in my arm board. The only issue I had was that I still had to change bin/irb, bin/ri, bin/rdoc, bin/testrb, bin/erb to point to the ruby binary, but the binary itself contained no references do tmp.

After all this work, irb and the other helpers worked ok. Now, on to get gtk and glade gems compiled under arm.

Good luck and leave a comment if you have any pointers to improve this guide.

10 Responses to “Cross compiling ruby to arm processors – the not so zen way”

  1. Keith Forsythe Says:

    We are a ruby on rails dev team, that needs to build an embeded device application for processing credit cards (kinda like at the grocery store self checkout). We are considering embeded Linux, running a ruby on rails stack (apache, phusion, and using the browser as a UI. Any thoughts?

  2. gm Says:


    I wouldn’t recommend that, as the ruby vm still have an inneficcient (IMO) garbage collector. I think you would be better trying gtk bindings for python or even ruby, and keeping the memory footprint low. That’s why I’ve compiled ruby for arm – to use it with gtk and wxwindows.

    I hope it helps, and let me know if you manage to do the rails stuff.



  3. Keith Forsythe Says:

    According to wikipedia, Ruby bindings for gtk exist, so thats good. I’m really hoping to find some solution where I can leverage my teams experience with Ruby to build a traditional desktop application.

    It’s possible we may go with an x86 device, in which case I have a lot more options for application sdk’s.

    Do you have any experience modifying an OS for embeded device development so that the application auto launches at boot?

  4. gm Says:

    I’m not sure if I understood your question, but in general lines you may use your own init script to start a program at boot…



  5. operat0r Says:

    I managed to get ruby compiled but without -with-openssl-dir= I think my problems are more then just openssl .. do I need to add libruby ? if so how ?

    * I got nmap working ..
    * I would like at least msfconsole
    * how do I also get it working with gems/RoR for autopwn etc ?

    ./lib/rex/text.rb:1:in `require’: no such file to load — digest/md5 (LoadError)

    from ./lib/rex/text.rb:1
    from ./lib/rex.rb:44:in `require’
    from ./lib/rex.rb:44
    from msfopcode:16:in `require’
    from msfopcode:16


    ruby msfconsole
    /sdcard/msf/lib/rex/text.rb:1:in `require’: no such file to load — stringio (Lo
    from /sdcard/msf/lib/rex/text.rb:1
    from /sdcard/msf/lib/rex.rb:44:in `require’
    from /sdcard/msf/lib/rex.rb:44
    from msfconsole:15:in `require’
    from msfconsole:15

    file ruby
    ruby: ELF 32-bit LSB executable, ARM, version 1 (SYSV), statically linked, for GNU/Linux 2.6.14, not stripped


    rmccurdy1@ \

  6. operat0r Says:

    im going to comment out all the require as I see its part of ruby ./ext/stringio/stringio.c so wish me luck. .. still need help with gems/RoR for autopwn on android

  7. operat0r Says:

    No luck is it something with dlopen configure in ruby ? or I need to hackup Metasploit some how ?

  8. gm Says:

    uh, I’m sorry I can’t help you with that, as I dont have any ARM based hardware around anymore. Check your toolchain tho.. it may be too new for the arm stuff be compiled. Let me know if you make any advance.

  9. operat0r Says:

    I managed to get NMAP working and RUBY will do basic hello world apps but still can’t get metasploit to work

  10. operat0r Says:

    Ok I managed to follow this tutorial and get ping compiled :

    I also manage to get ruby to compile ( not using the just toolchain ) but I got errors trying to get metasploit to run
    Read on the bottom )

    so now .. I guess want to statically compile ruby again but using this method ?
    I have folder in ./external/ruby-1.8.6-p111 but now what ?? how do I ./configure;make ?? because I don’t have file ?

    What I want is Metasploit on the Android 🙂 I managed to get nmap to work OK but ruby/metasploit I can assume is missing paths because I keep getting missing libs that I think were compiled in to the bin (ARM using toolchain )

    theres also this but im not sure if this is what I want !?

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