README
1$NetBSD: README,v 1.9 2024/02/04 05:43:05 mrg Exp $
2
3
4Building multi-ABI libraries for NetBSD platforms.
5
6
7src/compat has a framework to (re)build the libraries shipped with
8NetBSD for a different ABI than the default for that platform. This
9allows 32-bit libraries for the amd64 and sparc64 ports, and enables
10the mips64 port to support all three of old-style 32-bit ("o32"), the
11new 32-bit (default, "n32", 64-bit CPU required) or the 64-bit ABI.
12
13
14The basic premise is to re-set $MAKEOBJDIR to fresh subdirectory
15underneath src/compat and rebuild the libraries with a different set
16of options. Each platform wanting support should create their port
17subdirectory directly in src/compat, and then one subdirectory in here
18for each ABI required, e.g., src/compat/amd64/i386 is where we build
19the 32-bit compat libraries for the amd64 port. In each of these
20subdirectories, a small Makefile and makefile fragment should exist. The
21Makefile should set BSD_MK_COMPAT_FILE to equal the fragment, and then
22include "../../compatsubdir.mk". E.g., amd64/i386/Makefile has:
23
24 BSD_MK_COMPAT_FILE=${.CURDIR}/bsd.i386.mk
25
26 .include "../../compatsubdir.mk"
27
28In the makefile fragment any changes to ABI flags are passed here
29and the MLIBDIR variable must be set to the subdirectory in /usr/lib
30where libraries for the ABI will be installed. There are a couple of
31helper Makefiles 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/m32.mk"
45
46and the referenced m32.mk 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
57compatsubdir.mk holds the list of subdirectories (the libraries and
58ld.elf_so) to build with this ABI.
59
60archdirs.mk holds the list of subdirectories for each port.
61
62Makefile.compat has the basic framework to force the right paths for
63library and ld.elf_so linkage. It contains a hack to create subdirectories
64in the build that should be fixed.
65
66dirshack/Makefile is a hack to get objdirs created timely, and should
67be fixed in a better way.
68
69
70
71mrg@eterna23.net
72december 2009
73