|    sigreturn14: pc 0x4 or npc 0x1b2 invalid
|    kdb breakpoint at 1320bd8
|    Stopped in pid 173 (cron) at    cpu_Debugger+0x4:       nop
|    db> trace
|    syscall(9263ed0, 127, ffffffffffffdfd4, 0, 181c000, 154) at syscall+0x844
|    syscall_setup(ffffffffffffd998, 100190, 107000, ffffffffffffd940, badcafe, badca
|    fe) at syscall_setup+0x140
|    db> continue

For the umpteenth time:

This is caused by a diagnostic assertion when a call to sigreturn has an invalid
PC or NPC value.  If you don't want to see it then don't build a DEBUG kernel.

Eduardo