Hi David,
as outlined by Stefan, the 'linux_x86' platform looks for the host system and automatically decides whether to build for 32bit or 64bit. If the host system is 64bit, then Genode is built for 64bit. This is because our only current use case for the linux version is running Genode on the host. However, in your case, this causes trouble.
I'll try to briefly describe what is going on: You can find the detection-magic at 'base-linux/etc/specs.conf'. Depending on the host system, the 'spec.conf' file will set the 'linux_x86_64' or 'linux_x86_32' spec value, which triggers the inclusion of 'base-linux/mk/spec-linux_x86_32.mk' or 'base-linux/mk/spec-linux_x86_64.mk' respectively. In these files, the spec value 'x86_32' (or 'x86_64') get defined, which gets further broken up in 'base/mk/spec-x86_32.mk' (analogously for 64bit). This spec file adds the '32bit' spec value. If you like to peek onto the result of the successive spec decomposition, you might add the following line to '<build-dir>/Makefile' (right after the 'export SPECS' line:
$(warning SPECS=$(SPECS))
As Stefan already mentioned, you can override the default SPECS definition by a custom '<build-dir>/etc/specs.conf' file. Note the use of the assignment in contrast to the version found in 'base-linux/etc/specs.conf'.
I tried to force LIB_MK to the right syscall.mk but it then followed with a load of redefinition errors. Below is the make VERBOSE_DIR= output.
... /home/dwaddington/git/omnios/genode/base-linux/../base-linux/sr
/platform/x86_64/lx_clone.S:21:
Error: bad register name `%rsi'
It seems that the build system has not picked up your custom SPECS definition and still tries to use the SPECS as defined in 'base-linux/etc/specs.conf'. Hence, the build system keeps trying to build the 64bit code with the 32bit compiler. As a quick work-around, just to see if the code works, you may modify the 'base-linux/etc/specs.conf' file. But we should investigate why the build system ignores your '<build-dir>/etc/specs.conf' file. Could I have a look at your version of the file?
Best regards Norman