On Thu, Jul 30, 2015 at 5:22 PM, Andy Lutomirski <l...@amacapital.net> wrote: > On Thu, Jul 30, 2015 at 8:41 AM, Paolo Bonzini <pbonz...@redhat.com> wrote: >> >> >> On 24/07/2015 23:08, Andy Lutomirski wrote: >>> user_icebp is set if int $0x01 happens, except it isn't because user >>> code can't actually do that -- it'll cause #GP instead. >>> >>> user_icebp is also set if the user has a bloody in-circuit emulator, >>> given the name. But who on Earth has one of those on a system new >>> enough to run Linux and, even if they have one, why on Earth are they >>> using it to send SIGTRAP. >> >> You do not need either "int $0x01" or an ICE to set user_icebp = 1. You >> can use the 0xf1 opcode, which is kinda like 0xcc but generates #DB >> instead of #BP. > > Great. There's an opcode that invokes an interrupt gate that's not > marked as allowing unprivileged access, and that opcode doesn't appear > in the SDM. It appears in the APM opcode map with no explanation at > all. > > Thanks, CPU vendors. > > --Andy
Some Windows programs (running in Wine) use this opcode for anti-debugging code. See commit a1e80fafc9f0742a1776a0490258cb64912411b0. -- Brian Gerst -- 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/
