On 9 November 2013 14:40, Masami Hiramatsu <masami.hiramatsu...@hitachi.com> wrote: > (2013/11/09 1:56), Will Deacon wrote: >> Hi Sandeepa, >> >> On Thu, Oct 17, 2013 at 12:17:47PM +0100, Sandeepa Prabhu wrote: >>> Add support for basic kernel probes(kprobes), jump probes (jprobes) >>> for ARM64. >> >> I think this series will conflict quite heavily with the jump_label series, >> since they both introduce some common instruction manipulation code. On the >> debug side, there will also be conflicts with the kgdb series, so it might >> make sense for us to merge those two first, then you can rebase on a stable >> branch from us. > > [...] > >> In fact, how do you avoid a race with hardware breakpoints? E.g., somebody >> places a hardware breakpoint on an instruction in the kernel for which >> kprobes has patched in a brk. We take the hardware breakpoint, disable the >> breakpoint and set up a single step before returning to the brk. The brk >> then traps, but we must take care not to disable single-step and/or unmask >> debug exceptions, because that will cause the hardware breakpoint code to >> re-arm its breakpoint before we've stepped off the brk instruction. > > Hmm, frankly to say, this kind of race issue is not seriously discussed > on x86 too, since kgdb is still a special tool (not used on the production > system). > I think under such situation kgdb operator must have full control of the > system, and he can (and has to) avoid such kind of race. Masami,
Hmm I think in same lines, but not sure if we expect kprobes to be able to work fool-proof along with kgdb or hw breakpoints ? Thanks, Sandeepa > > Thank you, > > -- > Masami HIRAMATSU > IT Management Research Dept. Linux Technology Center > Hitachi, Ltd., Yokohama Research Laboratory > E-mail: masami.hiramatsu...@hitachi.com > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
