#2 Signals not working completely

[Christopher Williams]

Signal handlers are not being called when signals are raised. This needs to be done when returning to user mode (ie, from syscalls and from other interrupts). A sigreturn() system call will needs to be created to return from a signal handler.

Signals are also not checked every time the kernel returns to user mode, such as after a software exception. The ideal place to put this check is in trapret in entry.s.

[Christopher Williams]

Partially fixed. Signals are checked upon every return to user mode in entry.s, but signal handlers are not called still.