README ====== This README file describes the contents of the build configurations available for the NuttX QEMU i486 port. Contents ======== * QEMU - Building QEMU - Cygwin Build Problems - Running QEMU * Toolchains - Cygwin Buildroot Toolchain - Buildroot Instructions * FAQ * Configurations - ostest - nsh QEMU ==== QEMU is a generic and open source machine emulator and virtualizer. Here are some links (which will probably be mostly outdated by the time your read this): Home Page: http://wiki.qemu.org/Main_Page Downloads: http://wiki.qemu.org/Download Documentation: http://wiki.qemu.org/Manual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 --target-list=i386-softmmu 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 (I understand that this is difficult). NOTE: As of this writing, I have not been successful getting ANY pre-built version of QEMU to work successfully with WinXP. The same binaries work fine on Vista, however. Running QEMU ------------ In the top-level NuttX directory: qemu -cpu 486 -m 2 -kernel nuttx.elf -nographic The -nographic option redirects COM1 to your console. However, the -nographic option does not work under Cygwin. For simple testing under Cygwin, I use qemu -cpu 486 -m 2 -kernel nuttx.elf -serial file:test.txt which will send COM1 output to the file test.txt. 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. NOTE: It has also been reported to me that with a certain Ubuntu virtual installation, the native x86 did not build correct i486 code. Other installations of the same vintage do not have such issues. However, there is always a possibility that any GCC release will be incompatible with i486. That fallback used by this person in this particular case was to use the Buildroot i486 cross-development tool described below. I suspect that this was not necessary, but it was a simple work-around that allowed that person to build a work-able system. In any event, the PATH environment variable should be modified to point to the correct path to the GCC toolchain. 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 GIT or in any any 1.10 or later buildroot release. Buildroot Instructions ---------------------- 1. You must have already configured Nuttx in /nuttx. tools/configure.sh qemu-i486/ 2. Download the latest buildroot package into 3. unpack the buildroot tarball. The resulting directory may have versioning information on it like buildroot-x.y.z. If so, rename /buildroot-x.y.z to /buildroot. 4. cd /buildroot 5. cp configs/i486-defconfig-4.3.3 .config 6. make oldconfig 7. make 8. Make sure 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. FAQ === Q: I get the following error message, "undefined reference to '__stack_chk_fail'" A: Add -fno-stack-protector to ARCHCPUFLAGS in you Make.defs file. Switch the commenting on the following two lines in the Make.defs file: ARCHCPUFLAGS = -march=i486 -mtune=i486 -fno-builtin #ARCHCPUFLAGS = -march=i486 -mtune=i486 -fno-builtin -fno-stack-protector Configurations ============== Common Configuration Notes -------------------------- 1. Each Qemu-i486 Web Server configuration is maintained in a sub-directory and can be selected as follow: tools/configure.sh qemu-i486/ Where is one of the configuration sub-directories described in the following paragraph. 2. These configurations use the mconf-based configuration tool. To change a configurations using that tool, you should: a. Build and install the kconfig-mconf tool. See nuttx/README.txt see additional README.txt files in the NuttX tools repository. b. Execute 'make menuconfig' in nuttx/ in order to start the reconfiguration process. 3. By default, all configurations assume the Linux. This is easily reconfigured: CONFIG_HOST_LINUX=y Configuration Sub-Directories ----------------------------- ostest The "standard" NuttX examples/ostest configuration. nsh Configures the NuttShell (nsh) located at examples/nsh.