Some notes to help future porters. Replace 'ARCH' with whatever arch you are hacking on. ==================== === Config Files === ==================== - create extra/Configs/Config.ARCH See the other arch files for some good examples. powerpc/sparc/alpha should be pretty simple templates. - add ARCH to the 'Target Architecture' list in extra/Configs/Config.in - Initially you will want to disable shared libraries, since making the shared library loader work requires you first have basic architecture support working. Thus you should add HAVE_NO_SHARED and ARCH_HAS_NO_LDSO to Config.ARCH's HAVE_ELF ==================== === libc sysdeps === ==================== (note: if glibc has already been ported to your arch, you can usually just copy a lot of files from them rather than coding from scratch) - create libc/sysdeps/linux/ARCH - copy Makefile and Makefile.arch from libc/sysdeps/linux/i386/ - set CSRC and SSRC to nothing in Makefile.arch for now - create crt1.S which defines the _start function ... you will probably want to clear the frame pointer to make gdb happy, and then you will want to call the funcion __uClibc_main() which takes these parameters: __uClibc_main(main(), argc, argv, _init(), _fini()) Initially if you wish to make things easier on yourself, you can disable the UCLIBC_CTOR_DTOR option and just set those two arguments to NULL glibc generally stores this function in libc/sysdeps/ARCH/elf/start.S - create these additional files in ARCH/bits/ (template versions can be found in common/bits/ for you to tweak) endian.h fcntl.h setjmp.h stackinfo.h uClibc_arch_features.h wordsize.h kernel_types.h should be created based upon linux asm-ARCH/posix_types.h copy linux asm-ARCH/stat.h to bits/kernel_stat.h create syscalls.h based upon linux's unistd.h / glibc's sysdeps.h ... really you just want to define the _syscall[0-6] macros. It is important that these syscalls should be PIC safe (or you should provide a PIC and non-PIC version) if you wish to properly support shared libraries. - at this point, you should have enough to generate a working HELLO WORLD static binary (see test/silly/*.c files) - if you want UCLIBC_CTOR_DTOR support, you will need to create crti.S and crtn.S files which define function prologues/epilogues. - for a more stable static port, you will need to create these files (and update the Makefile.arch values accordingly) __longjmp bsd-_setjmp bsd-setjmp brk clone setjmp syscall vfork usually these are written in assembler, but you may be able to cheat and write them in C ... see other ports for more information ==================== === pthread deps === ==================== TODO: nptl / linuxthreads / linuxthreads.old ==================== === ldso sysdeps === ==================== - enable ldso/shared options in your extra/Configs/Config.ARCH file - you will need to create the following files in ldso/ldso/ARCH/ dl-debug.h dl-startup.h dl-syscalls.h dl-sysdep.h elfinterp.c resolve.S - dl-debug.h: define string versions of all the relocations of your arch in the _dl_reltypes_tab array ... the index should match the actual reloc type, so if the value of say R_X86_64_PC16 is 13, then "R_X86_64_PC16" better be at index 13 of the array - dl-startup.h: - define the _start function which should call _dl_start which takes just one parameter ... a pointer to argc (usually on the stack) - define the GET_ARGV() macro which calculates the value of argv based upon the parameter passed to _dl_start (usually it's simply just ARGS+1) - define PERFORM_BOOTSTRAP_RELOC() macro which will handle just the relocs that the ldso itself will generate - dl-syscalls.h: if you wrote your bits/syscalls.h file correctly in the libc step above, you can simply copy this file from another arch and be done ... otherwise you will have to define the syscall[0-6] macros again, but this time setting _dl_errno instead of just errno - dl-sysdep.h: misc cruft goes in here ... you want to: - either define or undefine ELF_USES_RELOCA - define the INIT_GOT macro - define MAGIC1 to the EM_### value your ELF arch uses - define ELF_TARGET to a string name for your arch - define the do_rem() macro - define misc ALIGN macro's - define elf_machine_type_class() macro - define the inline functions elf_machine_dynamic, elf_machine_load_address, and elf_machine_relative glibc stores a bunch of these values in libc/sysdeps/ARCH/dl-machine.h - elfinterp.c: define all the relocation functions ... it's best if you just copy from another arch which uses the same type of relocations (REL or RELA) and start from there. - resolve.S: front end of lazy relocation ... define the _dl_linux_resolve symbol which is called by a PLT entry which has yet to be setup ... you will want to: - set up arguments for _dl_linux_resolver() - call _dl_linux_resolver() - clean up after call - jump to function address now stored in PLT