[Xen-devel] RFC: how to differentiate livepatched symbol and original symbol in Xen hypervisor

[Dongli Zhang <dongli.zhang@xxxxxxxxxx>]

Hi,

About the livepatch TODO: "Make XENPF_get_symbol also include Live Patch
symbols" mentioned at http://wiki.xenproject.org/wiki/XSplice, I am wondering
how the patched function would be dumped.

For instance, if function "gnttab_usage_print_all" is livepatched, it  would
show as symbol in both Xen hypervisor and applied livepatch. How are we going
to differentiate the old and new symbols referring to the same symbol name but
different address? One address is the original and another is the on pointed by
instruction "e9 xxxxxxxx".

Here is a sample on my test machine. The following is my own customized xen
debug message in "xl debug-keys x". I am patching my own function "my_old_func"
in Xen hypervisor.

(XEN) name=my_global_domain, value=0xffff82d080409054, size=28, new=1
(XEN) name=my_old_func, value=0xffff82d080409070, size=89, new=0
(XEN) name=mg_data, value=0xffff82d08040a000, size=4, new=1

The following is the current result of XENPF_get_symbol on Dom0:

root@vm:/soft/img# cat /proc/xen/xensyms | grep my_old_func
ffff82d0802465a4 T my_old_func
ffff82d0802465a4 t .text.my_old_func

In this example, I livepatched "my_old_func" and thus we have two symbols
referring the same name but different addresses now (ffff82d0802465a4 and
ffff82d080409070).

Are we going to use new nm symbol flag , append extra string in symbol name
(e.g., my_old_func#livepatch) or this even does not matter?

Thank you very much!

Best,

Dongli Zhang

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel