uClinux Toolchain

Using the arm-uclinux toolchain for ARM7 FLAT binaries

Building uClibc

1. Use the PIC version of crt0

   In the uClibc source from the http://cvs.uclinux.org, make a symlink so that the PIC version of crt0.S is used.

2. Modify gcc-uClibc

   The gcc wrapper must be modified so that crt0.o is linked as the first object file.

   Index: extra/gcc-uClibc/gcc-uClibc.c =================================================================== RCS file: /var/cvs/uClibc/extra/gcc-uClibc/gcc-uClibc.c,v retrieving revision 1.20 diff -u -r1.20 gcc-uClibc.c --- extra/gcc-uClibc/gcc-uClibc.c 2001/05/31 23:07:50 1.20 +++ extra/gcc-uClibc/gcc-uClibc.c 2001/06/21 17:33:31 @@ -200,6 +200,13 @@ i = 0; gcc_argv[i++] = GCC_BIN; + + + // crt0 must be specified as the first object file + if (linking && source_count && use_start){ + gcc_argv[i++] = crt0_path[use_build_dir]; + } + for ( j = 1 ; j < argc ; j++ ) { if (strcmp("--uclibc-use-build-dir",argv[j]) == 0) { use_build_dir = 1; @@ -229,7 +236,7 @@ gcc_argv[i++] = usr_lib_path; } if (use_start) { - gcc_argv[i++] = crt0_path[use_build_dir]; + //xxxxxxxxxxxx gcc_argv[i++] = crt0_path[use_build_dir]; } if (use_stdlib) { gcc_argv[i++] = nostdlib;

3. Modify the link script for arm-uclinux-gcc

   --- armelf_uclinux.xr.orig Wed Jun 20 19:32:23 2001 +++ armelf_uclinux.xr Thu Jun 21 12:18:11 2001 @ -68,7 +68,12 @ the same address within the page on the next page up. */ .data 0 : { + __data_start = . ; + + *(.rodata) *(.rodata.*) *(.gnu.linkonce.r*) + *(.rodata1) *(.data) + *(.data.*) } .data1 0 : { *(.data1) } .eh_frame : { *(.eh_frame) }

   This modification is necessary to move the .rodata section into the data segment. If this is not done, all relocation offsets in the .data section are wrong.

4. Edit the configuration file After copying extra/Configs/Config.arm to ./Config, modify/add the following variables :

   CROSS = arm-uclinux CPUFLAGS=-mdisable-got OPTIMIZATION=-O2 HAS_MMU = false

5. Build the library according to the instructions in the README.

Building applications

1. Setting the path

   export PATH=<your uclibc-directory>/bin:$PATH

2. Compile

   gcc -mdisable-got -c source.c

3. Linking

   gcc -mdisable-got -Wl,-r obj1.o obj2.o ..... -o out.elf

4. Convert to FLAT format

   To convert to flat format, ldelft2 from the elf2flt-0.8 package can be used. Linking with ldelf2flt from the Aplio tools will not work, because all relocations are made from the data segment to the text segment. The conversion can be done with

   ldelf2flt -o out.flat out.elf

   It is very important to look for missing symbols here, because linking with -r doesn't give any error messages during the link process. The resuling flat file `out.flat' can be copied into the directory that is used to create the rom filesystem image. The applications that are created this way are suitable for XIP execution. Initialized variables will work as expected.