On Fri, May 15, 2015 at 10:22:48AM +0800, Minfei Huang wrote: > From: Minfei Huang <mnfhuang@xxxxxxxxx> > > The previous patches can be applied, once the corresponding module is > loaded. In general, the patch will do relocation (if necessary) and > obtain/verify function address before we start to enable patch. > > There are three different situations in which the coming module notifier > can fail: > > 1) relocations are not applied for some reason. In this case kallsyms > for module symbol is not called at all. The patch is not applied to the > module. If the user disable and enable patch again, there is possible > bug in klp_enable_func. If the user specified func->old_addr for some > function in the module (and he shouldn't do that, but nevertheless) our > warning would not catch it, ftrace will reject to register the handler > because of wrong address or will register the handler for wrong address. > > 2) relocations are applied successfully, but kallsyms lookup fails. In > this case func->old_addr can be correct for all previous lookups, 0 for > current failed one, and "unspecified" for the rest. If we undergo the > same scenario as in 1, the behaviour differs for three cases, but the > patch is not enabled anyway. > > 3) the object is initialized, but klp_enable_object fails in the > notifier due to possible ftrace error. Since it is improbable that > ftrace would heal itself in the future, we would get those errors > everytime the patch is enabled. > > In order to fix above situations, we can make obj->mod to NULL, if the > coming modified notifier fails. > > Signed-off-by: Minfei Huang <mnfhuang@xxxxxxxxx> Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Thanks! -- Josh -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
