Re: [Xen-devel] RFC: how to differentiate livepatched symbol and original symbol in Xen hypervisor
>>> On 06.06.16 at 15:32,wrote: > 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 ". > > 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=0x82d080409054, size=28, new=1 > (XEN) name=my_old_func, value=0x82d080409070, size=89, new=0 > (XEN) name=mg_data, value=0x82d08040a000, 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 > 82d0802465a4 T my_old_func > 82d0802465a4 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 (82d0802465a4 and > 82d080409070). > > 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? While the output is clearly wrong, the problem isn't distinguishing the symbols - that's simple: Everything outside of [_start,_end) is in a livepatch. (One issue here would be multiple replacement of the same symbol.) The main problem I see here is that xensyms_read() doesn't even enumerate the new symbols. Jan ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
Re: [Xen-devel] RFC: how to differentiate livepatched symbol and original symbol in Xen hypervisor
On Mon, Jun 06, 2016 at 06:32:16AM -0700, Dongli Zhang wrote: > 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. Thank you for taking a look! > > 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 ". > > 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=0x82d080409054, size=28, new=1 > (XEN) name=my_old_func, value=0x82d080409070, size=89, new=0 > (XEN) name=mg_data, value=0x82d08040a000, 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 > 82d0802465a4 T my_old_func > 82d0802465a4 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 (82d0802465a4 and > 82d080409070). /me nods. > > 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? It should not matter. What the /proc/xen/xensyms should return is the new address. For that to work the hypercall makes a call to xensyms_read and that needs to be fixed to also look in the livepatch symbols. It probably needs an iterator function to walk over each of the 'virtual_region', like this: diff --git a/xen/include/xen/symbols.h b/xen/include/xen/symbols.h index 20bbb28..5455a79 100644 --- a/xen/include/xen/symbols.h +++ b/xen/include/xen/symbols.h @@ -14,6 +14,9 @@ typedef const char *symbols_lookup_t(unsigned long addr, unsigned long *offset, char *namebuf); +typedef int symbols_iterator_t(uint32_t *symnum, char *type, + unsigned long *address, char *name); + /* Lookup an address. */ const char *symbols_lookup(unsigned long addr, unsigned long *symbolsize, diff --git a/xen/include/xen/virtual_region.h b/xen/include/xen/virtual_region.h index e5e58ed..bba0ac7 100644 --- a/xen/include/xen/virtual_region.h +++ b/xen/include/xen/virtual_region.h @@ -18,6 +18,10 @@ struct virtual_region /* If this is NULL the default lookup mechanism is used. */ symbols_lookup_t *symbols_lookup; +/* Walk over all of the symbols this region provides. */ +symbols_iterator_t *symbol_iterator; +unsigned long nr_symbols; + struct { const struct bug_frame *bugs; /* The pointer to array of bug frames. */ size_t n_bugs; /* The number of them. */ And xensyms_read would hook up to this.. somehow. And the livepatch.c would hook its symbol iterator to this function as well. > > Thank you very much! > > Best, > > Dongli Zhang ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
[Xen-devel] RFC: how to differentiate livepatched symbol and original symbol in Xen hypervisor
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 ". 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=0x82d080409054, size=28, new=1 (XEN) name=my_old_func, value=0x82d080409070, size=89, new=0 (XEN) name=mg_data, value=0x82d08040a000, 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 82d0802465a4 T my_old_func 82d0802465a4 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 (82d0802465a4 and 82d080409070). 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@lists.xen.org http://lists.xen.org/xen-devel