Cross-compiler Environment for Linux

USE THIS INSTRUCTIONS AT YOUR OWN RISK. STANDARD DISCLAIMER APPLIES:

  This QUICK-HOWTO is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  General Public License for more details. 

you have to type lines beginning with "#"
lines with // are comments on things you have to do before continuing

// SETUP OUR WORK DIR

# mkdir -p /usr/src/hri

// CVS CHECKOUT OF UCLINUX MODULE FOR REGISTERED USERS
# export CVS_RSH=ssh
# cvs -z9 -d:ext:$EMAIL:/cvsroot/hri co uClinux

// FIXME: test anonymous example
# cvs -z9 -d:pserver:anonymous@cvs.sf.net:/cvsroot/hri co uClinux

// NOW BUILD THE CROSS COMPILE ENVIRONMENT (need to be done only once)

# mkdir -p /usr/src/hri/arm-elf
# cd /usr/src/hri/arm-elf
// wget the following files from snapgear.org distribution
// get these from http://ftp.snapgear.org/pub/snapgear/tools/arm-elf/
	STLport-4.5.3.patch
	STLport-4.5.3.tar.gz
	binutils-2.10.tar.gz
	build-uclinux-tools.sh
	elf2flt-20030314.tar.gz
	gcc-2.95.3-arm-mlib.patch
	gcc-2.95.3-arm-pic.patch
	gcc-2.95.3-arm-pic.patch2
	gcc-2.95.3-full.patch
	gcc-2.95.3.tar.gz
	gdb-5.0.tar.gz
	genromfs-0.5.1.tar.gz
	uClibc-20030314.tar.gz

// get these from http://ftp.snapgear.org/pub/snapgear/tools/m68k-elf/
	binutils-2.10-full.patch
	gcc-2.95.3-m68k-zext.patch
	gcc-2.95.3-sigset.patch

// now edit build script, modify following lines, then build tools
# vi build-uclinux-tools.sh
	KERNEL="/usr/src/hri/uClinux"

	# TARGET=m68k-elf
	TARGET=arm-elf

	# set your install directory here and add the correct PATH
	PREFIX=/opt/tools

# ./build-uclinux-tools.sh build

// go take coffee, walk, wathever
// in case build fails (i.e. you forget to download a file), correct and issue

# ./build-uclinux-tools.sh continue

// and the compile will follow the last successfull module compile

// when it finishes, everything will go to $PREFIX (in my case, /opt/tools)

PATH=/opt/tools/bin:$PATH arm-elf-gcc to compile things

Published on the list on 28/Jan/2004

Sample Hello World Compile

# cat Makefile
CC = /opt/tools/bin/arm-elf-gcc

# this is the method that worked here
CFLAGS= -D__PIC__ --fpic -msingle-pic-base
LDFLAGS= -Wl,-elf2flt

# another method, I think I missed zFLAT executables on kernel
#CFLAGS=
#LDFLAGS= -Wl,-elf2flt=-z
# a third method I found
#CFLAGS = -O2 -pipe -Wall -g -fpic
#LDFLAGS = -Wl,-elf2flt

LIBS =
OBJS = hello.o

all:    hello

hello:  $(OBJS)
        $(CC) $(CFLAGS) $(LDFLAGS) -o hello $(OBJS) $(LIBS)

clean:
        rm -rf *.o *.elf *.gdb hello

# eof Makefile

# cat hello.c
#include 
main(void){
        printf("Hello world!\n");
        exit(0);
}

put it on NFS and run it from unit

# ./hello
Hello world!
#

here are some errors encountered while testing

# ./hello
Support for ZFLAT executables is not enabled.
Support for ZFLAT executables is not enabled.
bFLT: not found
# ./hello
BINFMT_FLAT: reloc outside program 0xa05d0000 (0 - 0x7064/0x5d80), killing hell!
BINFMT_FLAT: reloc outside program 0xa05d0000 (0 - 0x7064/0x5d80), killing hell!
SIGSEGV
# ./hello
Unhandled fault: external abort on linefetch (F4) at 0x00000001
fault-common.c(97): start_code=0x720040, start_stack=0x71ff90)
Bus error 

Published on the list on 28/Jan/2004

On 29/Jan/2004, Erwin Authried (Midori uClinux and armtool's author) shared a tip that one would need to include PIC options in LDFLAGS to some Makefiles (that do not use CFLAGS during linking) work. His example:

Makefile:
-------------------------
hello:	hello.o
-------------------------
If "-fpic" isn't in LDFLAGS, the linker will use wrong (non-pic)
libraries, because of the multilib-support.

Here's how I set the environment with Midori uClinux:

CFLAGS_PIC="-msingle-pic-base -fpic"
CFLAGS="-O2 ${CFLAGS_PIC}"
LDFLAGS="-Wl,-elf2flt ${CFLAGS_PIC}"