Hi! > >>> Right, so you're going to love uprobes, which does exactly that. The > >>> current proposal is overwriting the target instruction with an INT3 and > >>> injecting an extra vma into the target process's address space > >>> containing the original instruction(s) and possible jumps back to the > >>> old code stream. > >> > >> Just out of interest, how does it handle the threading issue? > >> > >> Last I saw, at least some CPU people were _very_ nervous about overwriting > >> instructions if another CPU might be just about to execute them. > > > > I think the issue was that ring 0 was never meant to do that, where as, > > ring 3 does it all the time. Doesn't the dynamic library modify its > > text? > > No, it has nothing to do with ring. It has to do with modifying code > that another CPU could be executing at the same time, and with modifying > code on the same processor through another virtual alias (they are > different issues.) The same issues apply regardless of the CPL of the > processor. ...but these are always 'there could be cpu bugs around' issues, right? Like amd k6. AFAICT x86 always supported self-modifying code without any extra barriers needed... -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
