Home | History | Annotate | Line # | Download | only in compat
README revision 1.4 
      1 $NetBSD: README,v 1.4 2009/12/13 09:27:57 mrg Exp $
      2 
      3 
      4 Building multi- ABI libraries for NetBSD platforms.
      5 
      6 
      7 src/compat has a framework to (re)build the libraries shipped with
      8 NetBSD for a different ABI than the default for that platform.  This
      9 allow 32-bit libraries for the amd64 and sparc64 ports, and enables
     10 the mips64 port to support all three of old-style 32-bit ("o32"), the
     11 new 32-bit (default, "n32", 64-bit CPU required) or the 64-bit ABI.
     12 
     13 
     14 The basic premise is to re-set $MAKEOBJDIRPREFIX to fresh subdirectory
     15 underneath src/compat and rebuild the libraries with a different set
     16 of options.  Each platform wanting support should create their port
     17 subdirectory directly in src/compat, and then one subdirectory in here
     18 for each ABI required.  e.g., src/compat/amd64/i386 is where we build
     19 the 32-bit compat libraries for the amd64port.  In each of these
     20 subdirs, a small Makefile and makefile fragment should exist.  The
     21 Makefile should set BSD_MK_COMPAT_FILE to equal the fragment, and then
     22 include "../../Makefile.common".  Eg, amd64/i386/Makefile has:
     23 
     24 	BSD_MK_COMPAT_FILE=${.CURDIR}/bsd.i386.mk
     25 
     26 	.include "../../Makefile.common"
     27 
     28 In the makefile fragment any changes to ABI flags are passed here
     29 and the MLIBDIR variable must be set to the subdirectory in /usr/lib
     30 where libraries for the ABI will be installed.  There are a couple of
     31 helper Makefile's around.  amd64/i386/bsd.i386.mk looks like:
     32 
     33 	LD+=			-m elf_i386
     34 	MLIBDIR=		i386
     35 	LIBC_MACHINE_ARCH=	${MLIBDIR}
     36 	COMMON_MACHINE_ARCH=	${MLIBDIR}
     37 	KVM_MACHINE_ARCH=	${MLIBDIR}
     38 	PTHREAD_MACHINE_ARCH=	${MLIBDIR}
     39 	BFD_MACHINE_ARCH=	${MLIBDIR}
     40 	CSU_MACHINE_ARCH=	${MLIBDIR}
     41 	CRYPTO_MACHINE_CPU=	${MLIBDIR}
     42 	LDELFSO_MACHINE_CPU=	${MLIBDIR}
     43 
     44 	.include "${NETBSDSRCDIR}/compat/Makefile.m32"
     45 
     46 and the referenced Makefile.m32 looks like:
     47 
     48 	COPTS+=			-m32
     49 	CPUFLAGS+=		-m32
     50 	LDADD+=			-m32
     51 	LDFLAGS+=		-m32
     52 	MKDEPFLAGS+=		-m32
     53 
     54 	.include "Makefile.compat"
     55 
     56 
     57 Makefile.common holds the list of subdirectories (the libraries and
     58 ld.elf_so) to build with this ABI.
     59 
     60 Makefile.md_subdir holds the list of subdirectories for each port.
     61 
     62 Makefile.compat has the basic framework to force the right paths for
     63 library and ld.elf_so linkage.  It contains a hack to create subdirs
     64 in the build that should be fixed.
     65 
     66 dirshack/Makefile is a hack to get objdirs created timely, and should
     67 be fixed in a better way.
     68 
     69 
     70 
     71 mrg (a] eterna.com.au
     72 december 2009
     73