On Tuesday 15 December 2009 08:54:04 pm Avi Kivity wrote: > On 12/15/2009 08:48 PM, Clemens Kolbitsch wrote: > > Hi list, > > > > I'm experiencing a strange emulation bug with the op-code below. The > > instruction raises a segfault in the application (running on the guest), > > however, if I enable KVM to run the exact same application, no segfault > > is raised. > > > > 0x0080023b: 8b 04 65 11 22 33 44 mov regEAX, [0x44332211] > > > > where "11 22 33 44" is just some address. According to gdb (on a 32bit > > little- endian machine), this instruction can be disassembled as a "mov > > address to reg-eax". > > This is an odd encoding for this instruction, since there is a shorter > one possible (8b 05 11 22 33 44). So it is possible there is a bug in > qemu that has never been triggered because compilers/assemblers don't > generate this encoding. > > btw, binutils disassembles this as > > 8b 04 65 11 22 33 44 mov 0x44332211(,%eiz,2),%eax > > I guess %eiz is some mnemonic for a "zero register" so the assembly can > be reassembled into a 7-byte instruction later.
Hi all, thanks for the quick replies. I also saw that the instruction is disassembled to the above instruction, but did not want to complicate my problem description :) Is there anything I can provide to help testing possible patches? --Clemens
