On 07/04/16 04:49, Konrad Rzeszutek Wilk wrote: > This change demonstrates how to generate an xSplice ELF payload. > > The idea here is that we want to patch in the hypervisor > the 'xen_version_extra' function with an function that will > return 'Hello World'. The 'xl info | grep extraversion' > will reflect the new value after the patching. > > To generate this ELF payload file we need: > - C code of the new code (xen_hello_world_func.c). > - C code generating the .xsplice.funcs structure > (xen_hello_world.c) > - The address of the old code (xen_extra_version). We > retrieve it by using 'nm --defined' on xen-syms. > - The size of the new and old code for which we use > nm --defined -S on our code and xen-syms respectively. > > There are two C files and one header files generated > during build. One could make this one C file if the > size of the newly patched function size was known in > advance (or an random value was choosen). > > There is also a strict order of compiling: > 1) xen_hello_world_func.c > 2) config.h - extract the size of the new function, > the old function and the old function address. > 3) xen_hello_world.c - which contains the .xsplice.funcs > structure. > 4) Link the object files in an xen_hello_world.xsplice file. > > The use-case is simple: > > $xen-xsplice load /usr/lib/debug/xen_hello_world.xsplice > $xen-xsplice list > ID | status > ----------------------------------------+------------ > xen_hello_world APPLIED > $xl info | grep extra > xen_extra : Hello World > $xen-xsplice revert xen_hello_world > Performing revert: completed > $xen-xsplice unload xen_hello_world > Performing unload: completed > $xl info | grep extra > xen_extra : -unstable > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com> > > --- > Cc: Stefano Stabellini <stefano.stabell...@citrix.com> > Cc: Julien Grall <julien.gr...@arm.com> > Cc: Keir Fraser <k...@xen.org> > Cc: Jan Beulich <jbeul...@suse.com> > Cc: Andrew Cooper <andrew.coop...@citrix.com>
Reviewed-by: Andrew Cooper <andrew.coop...@citrix.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
