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authorJosh Poimboeuf <jpoimboe@redhat.com>2015-01-20 09:26:19 -0600
committerJiri Kosina <jkosina@suse.cz>2015-01-20 20:09:41 +0100
commit3c33f5b99d688deafd21d4a770303691c7c3a320 (patch)
tree1b133a30910364c15190202616f65c08d306f55e /samples/livepatch
parent83a90bb1345767f0cb96d242fd8b9db44b2b0e17 (diff)
downloadlinux-3c33f5b99d688deafd21d4a770303691c7c3a320.tar.gz
livepatch: support for repatching a function
Add support for patching a function multiple times. If multiple patches affect a function, the function in the most recently enabled patch "wins". This enables a cumulative patch upgrade path, where each patch is a superset of previous patches. This requires restructuring the data a little bit. With the current design, where each klp_func struct has its own ftrace_ops, we'd have to unregister the old ops and then register the new ops, because FTRACE_OPS_FL_IPMODIFY prevents us from having two ops registered for the same function at the same time. That would leave a regression window where the function isn't patched at all (not good for a patch upgrade path). This patch replaces the per-klp_func ftrace_ops with a global klp_ops list, with one ftrace_ops per original function. A single ftrace_ops is shared between all klp_funcs which have the same old_addr. This allows the switch between function versions to happen instantaneously by updating the klp_ops struct's func_stack list. The winner is the klp_func at the top of the func_stack (front of the list). [ jkosina@suse.cz: turn WARN_ON() into WARN_ON_ONCE() in ftrace handler to avoid storm in pathological cases ] Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Reviewed-by: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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