Index:

 Section 0: The Basics

    Q0.0:  What is "lxrun"?

    Q0.1:  That sounds awesome!  Tell me very quickly how I can
	   get started using lxrun!

    Q0.2:  How does lxrun work?

    Q0.3:  That's brilliant.  Who was the genius who came up with lxrun?


 Section 1: Using lxrun

    Q1.0:  What binary formats does lxrun support?

    Q1.1:  What does lxrun need in order to work?

    Q1.2:  How can I run Linux applications that use audio?

    Q1.3:  What sorts of Linux binaries work well with lxrun?


 Section 2: Adding System Calls to lxrun

    Q2.0:  How complete is lxrun?

    Q2.1:  What if I find a Linux binary that lxrun doesn't support?


 Section 3: Troubleshooting

    Q3.0:  What does "linuxemul:  fatal error:  program load failed:  No
	   such file or directory" mean?

    Q3.1:  What does "progname:  can't load library 'some_library_name.so'"
	   mean?

    Q3.2:  Why are my Linux binaries unable to find their data files?

    Q3.3:  What should i do if i find a problem with lxrun ?



		       === Section 0: The Basics ===

Q0.0: What is "lxrun"?

   A: It is a Linux emulator for SCO OpenServer and UnixWare machines.


Q0.1:  That sounds awesome!  Tell me very quickly how I can get
       started using lxrun!

   A:  Follow these steps:

	0. Unpack lxrun-0.8.6.cpio.gz.
           Do this as "root" from the root directory (/).
           Issue the commands (assuming you downloaded into /tmp) :
             # cd /
             # gzcat /tmp/lxrun-0.8.6.cpio.gz | cpio -icdvu
           The lxrun distribution should extract into the
           etc and usr/local directories.

	1. Copy a Linux binary to the /usr/local/linux/bin directory
           If you don't have a Linux system at hand, use one of the
           mirrors at ftp://sunsite.unc.edu/pub/Linux/welcome.html
           to download an app off the net.

           Let's say the Linux binary is called "lyap".

	2. Create a symbolic link to "lxfront" as follows :
           # ln -s /usr/local/linux/bin/lxfront /usr/local/bin/lyap

	3. Type "/usr/local/bin/lyap" or simply "lyap" if
           /usr/local/bin is in your execution search path. 

	3b. Optionally, set the environment variable LINUX_ROOT to
	    "/usr/local/linux" and execute your Linux applications
            by running "lxrun (app-pathname)" where "(app-pathname)"
            refers to the Linux application path (lxfront does this
            for you).


Q0.2: How does lxrun work?

   A: It works by remapping system calls on the fly.  As it turns
      out, there's not much difference between Linux and SCO
      binaries.  The main difference is the way in which system
      calls are handled.  In Linux, an "int 80" instruction is
      used, which jumps to the system-call-handling portion of
      the Linux kernel.  On SCO systems, "int 80" causes a
      SIGSEGV signal.  lxrun intercepts these signals and calls
      the SCO equivalent of the system call that the Linux
      program attempted.  The result is that the Linux binary
      runs (with the help of lxrun) on the SCO platform with a
      small (often negligible) performance penalty.  All this is
      accomplished without modifying the kernel.


Q0.3: That's brilliant.  Who was the genius who came up with lxrun?

   A: Michael Davidson, an engineer at SCO.



		       === Section 1: Using lxrun ===

Q1.0: What binary formats does lxrun support?

   A: lxrun understands Intel Linux a.out and ELF format
   binaries.


Q1.1: What does lxrun need in order to work?

   A: To run most Linux programs, lxrun requires the help of the
      Linux dynamic loader (ld.so) and whatever Linux shared
      libraries are required by the program.  Follow the steps
      in Q0.1 above to set up lxrun.


Q1.2: How can I run Linux applications that use audio?

      If you want to run a program that uses audio, get a copy
      of the OSS drivers from:


	http://www.sco.com/skunkware/audiovis/index.html#4front

      for 100% soundblaster compatible cards or:


      	http://www.4front-tech.com/

      for other sound cards.


Q1.3: What sorts of Linux binaries work well with lxrun?

   A: X applications seem to work well.  Curses programs often
      seem to leave the stty settings in strange states.  (This
      is because the termio ioctls are not handled well by
      lxrun.  Anybody want to fix this?)

      In particular, xdoom and raplayer (RealAudio client) seem
      to work well.


	       === Section 2: Adding System Calls to lxrun ===

Q2.0: How complete is lxrun?

   A: Somewhat complete.  Obviously, the more system calls lxrun is
      able to translate, the more complete its emulation
      capabilities.  In this release, lxrun has a _lot_ of
      unimplemented system calls, but they are calls that are
      not used very often.  So lxrun can successfully run _many_
      Linux binaries.


Q2.1: What if I find a Linux binary that lxrun doesn't support?

   A: Follow these simple steps:

	0. Go to http://www.sco.com/skunkware and make
	sure you have the most recent version of lxrun.  If not,
	download the latest one and try it.  We are updating
	lxrun with new system calls all the time.

	1. Recompile lxrun with the TRACE option enabled.  (This
	requires modifying one line in the Makefile.)  This will
	cause lxrun to produce a history of all system calls
	used by the binary as it was run (similar to the
	"truss" and "trace" commands).  The trace dump will be
	created in a file called "lxrun.log".

	2. Try to narrow down exactly which system call failed.
	Most likely, the failure will be due to a system call
	that has not yet been implemented in lxrun.

	3. Implement the system call mapping.  This is usually
	pretty easy to do.  The vast majority of lxrun's code
	does mappings of this sort, so you can pick out almost
	any source file to see how it is done.  Chances are, the
	system call you need to remap is already in one of the
	lxrun source files, but its code looks something like
	this:

	int lx_flock()		{ errno = ENOSYS; return -1; }	

	This means that you're the first person who has gotten
	around to mapping that particular system call.

	4. After making your modification, recompile lxrun and
	see if it works.  You may have to remap more than one
	system call to get your binary working!

	5. E-Mail your changes to skunkware@sco.com.  This way,
	we can put your changes into the next release of lxrun.

	6. If steps 1-5 seem are beyond your programming
	ability, contact skunkware@sco.com and maybe one of the
	Skunk team will have time to give you a hand with it.
	Make sure to tell us exactly what program you're having
	trouble with.


		     === Section 3: Troubleshooting ===

Q3.0: What does "linuxemul: fatal error: program load failed: No
      such file or directory" mean?

   A: It probably means you have your LINUX_ROOT environment
      variable set up incorrectly.


Q3.1: What does "progname: can't load library 'some_library_name.so'"
      mean?

   A: It means you're missing a shared library that is needed to
      run a particular binary.  You can either try to find a
      compiled version of the library from a Linux ftp site
      (such as ftp://sunsite.unc.edu/pub/Linux/libs/) or if you
      have access to a running Linux system, you can copy the
      library directly.  You should put the library in
      $LINUX_ROOT/lib on your SCO system (/usr/local/linux/lib by default).


Q3.2: Why are my Linux binaries unable to find their data files?

   A: To aid in the emulation process, lxrun prepends the contents
      of the $LINUX_ROOT variable too many common pathnames.  Try
      putting your program's data files in $LINUX_ROOT/whatever
      instead of /whatever.

Q3.3: What should i do if i find a problem with lxrun ?

   A: Please report any difficulty you have with lxrun by e-mailing
      skunkware@sco.com. Feel free to include suggestions, comments, 
      code modifications, extensions, ...