path: root/nuttx/configs/qemu-i486/README.txt

README
^^^^^^

This README file describes the contents of the build configurations available
for the NuttX QEMU i486 port.

Contents
^^^^^^^^

  * QEMU
  * Toolchains
  * Configurations

QEMU
^^^^

QEMU is a generic and open source machine emulator and virtualizer.  Here are
some links (which are mostly outdated by the time your read this):

  Home Page:     http://wiki.qemu.org/Main_Page
  Downloads:     http://wiki.qemu.org/Download
  Documentation: http://wiki.qemu.org/Manual
  Usage:         qemu -nographic -kernel nuttx.elf

Building QEMU:

  tar zxf qemu-0.14.0.tar.gz 
  cd qemu-0.14.0
  ./configure
  make
  make install

Cygwin build problems:

  Error:
 
    "gcc: The -mno-cygwin flag has been removed; use a mingw-targeted cross-compiler."

  Workaround:
  
    None known.  It does not seem possible to build QEMU using the Cygwin gcc.
	I tried editing configure.  Removing the following line will allow QEMU to
	configure:
  
      QEMU_CFLAGS="-mno-cygwin $QEMU_CFLAGS"

	However, it then fails later during the compilation phase.

  Recommendation:
 
    1. Google for "qemu windows download" and download some pre-built QEMU
	   binaries.  I found 0.14.0 here: http://dietpc.org/windows/qemu/, or
	2. Try building QEMU with MingGW

Toolchains
^^^^^^^^^^

  Two target environments are supported: (1) Linux and (2) Cygwin under Windows.
  Any GCC toolchain that can produce i486 ELF binaries should work.  On Linux,
  you can probably use the installed system gcc.  But that will not work with
  Cygwin.  Why?  Because the Cygwin gcc (and probably the MinGW gcc as well) do
  not produce ELF final binaries but, rather, DOS MZ executables (i.e., .exe
  files).  Those cannot be used with QEMU.

  The file */setenv.sh should be modified to point to the correct path to the
  GCC toolchain (if different from the default in your PATH variable).

  Cygwin Buildroot Toolchain

  With Cygwin the solution is to build an i486 cross-development toolchain to
  generate the i486 ELF files needed by QEMU.  The NuttX buildroot package will
  create such a toolchain.

  NOTE: As of this writing, none of the released buildroot packages support the
  i486 build.  This is only available in SVN or in any any 1.10 or later buildroot
  release.

  Buildroot Instructions

  1. You must have already configured Nuttx in <some-dir>/nuttx.

     cd tools
     ./configure.sh qemu-i486/<sub-dir>

  2. Download the latest buildroot package into <some-dir>

  3. unpack the buildroot tarball.  The resulting directory may
     have versioning information on it like buildroot-x.y.z.  If so,
     rename <some-dir>/buildroot-x.y.z to <some-dir>/buildroot.

  4. cd <some-dir>/buildroot

  5. cp configs/i486-defconfig-4.3.3 .config

  6. make oldconfig

  7. make

  8. Edit setenv.h, if necessary, so that the PATH variable includes
     the path to the newly built binaries.

  See the file configs/README.txt in the buildroot source tree.  That has more
  detailed PLUS some special instructions that you will need to follow if you
  run into problems building the toolchain for Cygwin under Windows.

Configurations
^^^^^^^^^^^^^^

ostest

  The "standard" NuttX examples/ostest configuration.  This
  configuration may be selected as follows:

    cd <nuttx-directory>/tools
    ./configure.sh qemu-i486/ostest