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Konrad Rzeszutek Wilk
ffcd7c0698
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.wilk@oracle.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Julien Grall <julien.grall@arm.com> [ARM]
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>
xen-bugtool =========== The xen-bugtool command line application will collate the Xen dmesg output, details of the hardware configuration of your machine, information about the build of Xen that you are using, plus, if you allow it, various logs. The information collated can either be posted to a Xen Bugzilla bug (this bug must already exist in the system, and you must be a registered user there), or it can be saved as a .tar.bz2 for sending or archiving. The collated logs may contain private information, and if you are at all worried about that, you should not use this tool, or you should explicitly exclude those logs from the archive. xen-bugtool is wholly interactive, so simply run it, and answer the questions.