Invalid Opcode on ia32, Pistachio 0.4

Hi!

I'm trying to understand the handling of the invalid opcode exception on
ia32. In particular, I wonder in which cases the handler
(/source/kernel/src/glue/v4-ia32/exception.cc, L.211 et seq.) will send
an exception-IPC to the exception-handler-thread (if existent).

The code there reads as follows:

221     if (space->is_user_area(addr))
222     {
223         switch(space->get_from_user(addr))
224         {
225         case 0xf0: /* lock prefix */
226             if (space->get_from_user(addr_offset(addr, 1)) == 0x90)
227             {
228                 /* lock; nop */
229                 frame->eax =
(u32_t)space->get_kip_page_area().get_base();
230                 frame->ecx = get_kip()->api_version;
231                 frame->edx = get_kip()->api_flags;
232                 frame->esi =
get_kip()->get_kernel_descriptor()->kernel_id.get_raw();
233                 frame->eip+= 2;
234                 return;
235             }
236         default:
237             printf("invalid opcode  at IP %p\n", addr);
238             enter_kdebug("invalid opcode");
239         }
240     }
241
242     if (send_exception_ipc(frame, IA32_EXC_INVALIDOPCODE))
243         return;

This looks to me like any invalid opcode in the user area (except the
sequence lock; nop;) will execute enter_kdebug() and thus basicly crash.
By this, the exception-IPC will only be sent if the invalid opcode was
executed _not_ in user area.
Does this make sense? Wouldn't it make more sense to skip the
enter_kdebug() in L.238 (comment out) to sent the exception-IPC if the
exception was not caused by the KIP-syscall?

Any hints appreciated..


Best regards,

Alexander Wieder