On Thu, Nov 06, 2014 at 10:20:49AM -0600, Seth Jennings wrote: > On Thu, Nov 06, 2014 at 04:11:37PM +0100, Jiri Kosina wrote: > > On Thu, 6 Nov 2014, Seth Jennings wrote: > > > +/**************************************** > > > + * dynamic relocations (load-time linker) > > > + ****************************************/ > > > + > > > +/* > > > + * external symbols are located outside the parent object (where the parent > > > + * object is either vmlinux or the kmod being patched). > > > + */ > > > > I have no ideas what dynrela is, and quickly reading the source doesn't > > really help too much. > > > > Could you please provide some explanation / pointer to some documentation, > > explaining what exactly it is, and why should it be part of the common > > infrastructure? > > Yes, I should explain it. > > This is something that is currently only used in the kpatch approach. > It allows the patching core to do dynamic relocations on the new > function code, similar to what the kernel module linker does, but this > works for non-exported symbols as well. > > This is so the patch module doesn't have to do a kallsyms lookup on > every non-exported symbol that the new functions use. > > The fields of the dynrela structure are those of a normal ELF rela > entry, except for the "external" field, which conveys information about > where the core module should go looking for the symbol referenced in the > dynrela entry. BTW, use of the dynrelas is optional, but highly recommended. The kGraft approach of manually doing a kallsyms lookup for each non-exported symbol is inherently dangerous because of duplicate symbols. -- 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
