On Tue, Nov 10, 2015 at 09:49:09AM +0100, Miroslav Benes wrote: > On Mon, 9 Nov 2015, Josh Poimboeuf wrote: > > > On Mon, Nov 09, 2015 at 05:01:18PM -0600, Chris J Arges wrote: > > > On 11/09/2015 02:56 PM, Josh Poimboeuf wrote: > > > > I'd recommend splitting this up into two separate patches: > > > > > > > > 1. introduce old_sympos > > > > 2. change the sysfs interface > > > > > > > > On Mon, Nov 09, 2015 at 10:16:05AM -0600, Chris J Arges wrote: > > > >> In cases of duplicate symbols in vmlinux, old_sympos will be used to > > > >> disambiguate instead of old_addr. Normally old_sympos will be 0, and > > > >> default to only returning the first found instance of that symbol. If an > > > >> incorrect symbol position is specified then livepatching will fail. > > > > > > > > In the case of old_sympos == 0, instead of just returning the first > > > > symbol it finds, I think it should ensure that the symbol is unique. As > > > > Miroslav suggested: > > > > > > > > 0 - default, preserve more or less current behaviour. If the symbol is > > > > unique there is no problem. If it is not the patching would fail. > > > > 1, 2, ... - occurrence of the symbol in kallsyms. > > > > > > > > The advantage is that if the user does not care and is certain that the > > > > symbol is unique he doesn't have to do anything. If the symbol is not > > > > unique he still has means how to solve it. > > > > > > > > > > So one part that will be confusing here is as follows. > > > > > > If '0' is specified for old_sympos, should the symbol be 'func_name,0' > > > or 'func_name,1' provided we have a unique symbol? We could also default > > > to 'what the user provides', but this seems odd. > > > > I don't feel strongly either way, but I think using the same number the > > user provides is fine, since it makes the sysfs interface consistent > > with the old_sympos usage. > > I think it should be func_name,1 even if '0' is specified and the symbol > is unique. Because if we say that 1, 2, ... is the occurrence of the > symbol in kallsyms it should stay that way everywhere. Hence for > old_sympos == 0 it is func_name,1 in sysfs; for 1 it is still func_name,1; > for 2 it is func_name,2 and so on. > > And I'd add this to sysfs documentation. That makes sense, sounds fine to me. -- Josh -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
