Adding new überApps

Integrating a new überApp into the micro-hypervisor requires the following integration pieces:

  1. Create directory for überApp functionality (e.g., xh_newapp) within the xmhf-uobjs folder

    • xh_newapp.gsm defines key attributes of the überApp
    • xhnewapp_main.c is used to invoke different operations (e.g., initialize, hypercall, shutdown, etc.). Where each of these opertions has a related file (xhnewapp_hcbinit.c)
  2. To integrate the überApp add references in the following locations:

    • Add xh_newapp to the list in xmhf-uobjs/
    • Add a DEFINE XMHFGEEC_SLAB_XH_NEWAPP to include/xmhf-config.h
    • Add a table entry to static xc_hypapp_info_t _xcihub_hypapp_info_table[] corresponding to the operations your hypapp performs in xmhf-uobjs/include/xc.h
    • Add xh_newapp to the list of uobj-callees in xmhf-uobjs/xc_init/sc_init.gsm and xmhf-uobj/xc_ihub/xc_ihub.gsm
  3. Ensure that your reconfigure prior to building (this is required to rewrite xmhf-uobjs/UOBJLST that is used by the Makefile). Follow the steps in uberXMHF (pc-intel-x86_32) Veryfying and Building

  4. Add a test program that exercises your überApp in xmhf-rgapps/linux

    • Create a directory for the test program (rgapp-newapp) that includes a Makefile and the testprogram (rgapp-newapp.c).
    • This test program will need to call __vmcall(eax, ebx, edx, ecx), where eax is the hypercall ID, ebx is the high order 32-bit of the physical address, edx is the low-order 32-bit of the physical address (e.g., of an up to 4KB buffer being passed to the überApp), and ecx is variable based upon the überApp.
    • This test program needs to convert the data buffer being sent to the überApps from a virtual to a physical address. Some approaches for this (such as reading /proc/self/pagemap) require root permissions.
  5. Run the test program (using permissions as required, see above).

xh_uhcalltest is an example überApp that follows the above steps to demonstrate a simple hypercall handling functionality. The corresponding rich-guest application is found within xmhf-rgapps/linux/rgapp-uhcalltest.


Currently, the preferred method of adding überApps is to switch out an existing überApp (to preserve the memory mapping). By default the following überApps are enabled: syscalllog, hyperdep, and ssteptrace. Thus to add a new überApp, one would replace one of the above with the new überApp.


To expand the number of überApps that can be enabled, the memory map must be expanded. This requires changing the size within include/xmhf-config.h by modifying definitions such as XMHFGEEC_xxx_{BASE/MAX}_IDX; and` by modifying exports such as UXMHF_TOTAL_xxSLABS, XMHF_CONFIG_LOADADDR, XMHF_CONFIG_LOADMAXSIZE, and XMHF_CONFIG_LOADMAXADDR.


The folloinwg are default naming conventions for üobjects within the micro-hypervisor: * xc = uberXMHF core * xh = uberXMHF hypapps * xg = uberXMHF Guest