Messages in this thread | | | Date | Fri, 7 Oct 2011 12:40:48 +0200 | Subject | Re: [PATCH 07/12] perf_events: add LBR software filter support for Intel X86 | From | Stephane Eranian <> |
| |
On Fri, Oct 7, 2011 at 12:38 PM, Stephane Eranian <eranian@google.com> wrote: > On Thu, Oct 6, 2011 at 5:32 PM, Andi Kleen <andi@firstfloor.org> wrote: >>> + kernel_insn_init(&insn, kaddr); >>> + insn_get_opcode(&insn); >> >> This makes me uncomfortable. AFAIK that's the first use of the opcode >> decoder being used directly for user space. It has a quite large attack >> surface. Who says it cannot be exploited? >> > This is not new, it's already used for the PEBS fixups and that includes > user level fixups, if possible. > > We are not executing the instruction here, just decoding it to filter it out > from a buffer if necessary. > I would add that in this particular usage, the source address is coming straight from LBR, it's not made up my SW. That means it corresponds to a point where there was a control flow change. But it can certainly be any x86 opcode (not just branches). LBR captures control flow changes due to traps, faults, interrupts. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |