BTW, I think that turning on debugger from qemu is a dangerous action, from security point of view. Once the gdbserver is started, anybody can connect to it (with gdb) and modify VM memory in anyway he wants (like overwrite kernel with malicious code). The problem why this is feasible is because there is no authentication machanism on gdbserver at all.
Any idea? Thanks, Jun On 6/25/07, Dong, Eddie <[EMAIL PROTECTED]> wrote: > Jun Koi wrote: > > On 6/25/07, Dor Laor <[EMAIL PROTECTED]> wrote: > >>> On 6/25/07, Dong, Eddie <[EMAIL PROTECTED]> wrote: > >>>> [EMAIL PROTECTED] wrote: > >>>>> On 6/25/07, Dor Laor <[EMAIL PROTECTED]> wrote: > >>>>>>> I am wondering how KVM handles debug and breakpoint interrupt? > >>>>>>> Does it process them like normal NMI interrupt, or is there any > >>>>>>> special processing? > >>>>>>> > >>>>>> > >>>>>> I haven't use it but KVM does support qemu'd gdbstub. Both single > >>>>>> step and breakpoint are possible. From the source code (vmx.c) it > >>>>>> seems like handle_exception function handle them as regular > >>>>>> exceptions (non nmi). > >>>>> > >>>>> Are you sure? the kvm_vmx_exit_handlers function pointer arrays > >>>>> has the index named EXIT_REASON_EXCEPTION_NMI, so it must be > >>>>> handled as NMI to me. > >>>> > >>>> This exit reason is either NMI, or software interrupt or exception. > >>>> > >>>> Refer update_exception_bitmap for the setting of VM Exit for which > >>>> exception (int n). > >>>> > >>>> In normal situation, I think guest int 1/3 directly get handled in > >>>> guest. > >>> > >>> > >>> So you mean interrupts 1/3 do not cause VMExit?? > >> > >> Int 1 is updated in the update_exception_bitmap, so it does causes > >> vmexit. > >> > > > > Is there any reason only int 1 causes VMExit, but not int 3? > > > This int 1 exit is for host debugging guest purpose not guest self > debuging. > For the case host debuging guest purpose, DR register is used, so no > need of INT3, > but INT1 can be used as single step and probably used to by pass the DR > breakpoint. > > For guest self debug purpose, no INT 1/3 trap. So seemlessly supported. > Eddie > ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
