2012/10/15 Dave Martin <[email protected]>: > On Sun, Oct 14, 2012 at 09:23:13PM +0200, Rabin Vincent wrote: >> Add basic uprobes support for ARM. >> >> perf probe --exec and SystemTap's userspace probing work. The ARM >> kprobes test code has also been run in a userspace harness to test the >> uprobe instruction decoding. > > The assumption that the target code is ARM appears to be buried all over > the place.
Right, as stated: >> Caveats: >> - Thumb is not supported > Certainly this code as currently written must depend on !THUMB2_KERNEL. Why? It currently works for ARM userspace even if the kernel is Thumb-2. > However, there's an underlying problem here which we'd need to solve. > The kprobes code can take advantage of the fact that the kernel is all > ARM or (almost) all Thumb code. So there is no support for kprobes > supporting ARM and Thumb at the same time. > > With userspace, we don't have this luxury. With Debian armhf, Ubuntu > and Linaro building Thumb-2 userspaces, it may be an increasingly common > configuration independently of whether the kernel is built in Thumb-2 > or not. > > Furthermode, there is no such thing as a pure Thumb-2 system in practice: > PLTs are always ARM, for example. For uprobes to work well in userspace, > both should be supported together. Right. I don't think it's difficult to support both of them together, my thought was just to have userspace tell us if they want to probe a Thumb instruction via the usual 0th-bit set convention, and then take it from there. I didn't do the Thumb handling currently because I didn't really look into modifying the kprobes Thumb instruction decoding and the IT handling for uprobes. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
