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.Dd August 27, 2020 .Dt COMPAT_BSDOS 8 .Os .Sh NAME .Nm compat_bsdos .Nd binary compatibility for BSDi releases .Sh DESCRIPTION The .Dv COMPAT_NOMID kernel option includes compatibility with .Tn BSDi Ns No 1. Ns Em \^x Ns \|\(en\|3. Ns Em \^x .Xr a.out 5 binaries on .Nx Ns Tn /i386 and .Nx Ns Tn /amd64 . The option is enabled by default in the .Li GENERIC kernel on i386, but needs to be set along with .Dv EXEC_AOUT on amd64.
p Null memory protection must be disabled with the .Xr sysctl 7 option .Va vm.user_va0_disable set to .Li 0 for the binaries to run successfully.
p sx binaries may be placed under
a /emul directory to match the location of other non-native executables on .Nx , but the compatibility environment does not automatically lookup libraries under
a /emul/bsdos as happens with the shared libraries for .Nx 1.0\|\(en\|1.5 .Xr a.out 5 binaries under
p .Tn BSD/386 Ns No 1.0\|\(en\|1.1 uses static binaries that do not dynamically load libraries at runtime.
p sx 2.0 introduced .Dq "static shared libraries" as the default for standard binaries. The shared libraries are compiled from
a /lib and
a /usr/lib to a custom format bound to memory loading addresses for each library under
a /shlib . BSDi libraries under
a /shlib are not in the standard .Xr ar 5 or position-independent shared object formats and cannot be loaded by .Xr ldconfig 8 on .Nx . In order for BSDi executables to access the objects at the hardcoded
a /shlib path, the user may setup a symbolic link from
a /shlib to
a /emul/bsdos/shlib .
or run a shell under a
.Ic chroot
with the command
.Ic chroot "/emul/bsdos /bin/sh" .
One could rebuild the BSDi userland
from source using
.Pa /emul/bsdos/lib
and
.Pa /emul/bsdos/usr/lib .
Then adding
.Pa /emul/bsdos/lib
and
.Pa /emul/bsdos/usr/lib
to
.Pa /etc/ld.so.conf
and running
.Ic ldconfig
to regenerate
.Pa /var/run/ld.so.hints
for a new hybrid setup.
p sx 4.0 switched to an ELF binary executable format that does not run under the compatibility layers currently available on .Nx . .Sh SEE ALSO .Xr ld.aout_so 1 , .Xr options 4 , .Xr a.out 5 , .Xr elf 5 , .Xr sysctl 7 , .Xr compat_netbsd32 8 , .Xr ldconfig 8 .Sh HISTORY .Tn BSD/386 Ns No 1.0\|\(en\|1.1 was derived from x 4.3 Tn Reno code in the .Tn Net/2 release.
p sx 2.0 was based on x 4.4 Tn Lite , but added the new static shared library format as the runtime default for executables. The build system included the .Li shlicc command with the .Fl Bstatic flag that allowed reverting to the standard library archive format that remained available under
a /lib and
p .Nx 1.0 added shared libraries using a standard position-independent shared object format. The previous default relocatable libraries in the traditional .Xr ar 5 format remained available.
p .Ox 2.2\|\(en\|4.7 included a different compatibility implementation under the .Dv COMPAT_BSDOS kernel option. .Sh BUGS sx compatibility was broken on .Nx 5\|\(en\|6 .
p sx 3.0 added .Tn SPARC support, but the binaries are incorrectly recognized as .Tn SunOS executables and fail on .Nx Ns Tn /sparc and .Nx Ns Tn /sparc64 .