scsh-0.6/scsh/sighandlers.scm

365 lines
13 KiB
Scheme

;;; Copyright (c) 1993 by Olin Shivers.
;;; Signal handler system
;;; The principal trickiness here is that we have to interface to Unix signals
;;; *through* an intermediate interface, the S48 vm's idea of interrupts.
;;; So there is a difference between delivering a signal to the underlying
;;; Unix process and delivering it to the program that runs on the VM.
;;;
;;; One effect is that we have two separate codes for the same thing -- the
;;; Unix signal code, and the S48 interrupt value. E.g., SIGNAL/TSTP and
;;; INTERRUPT/TSTP.
;;; These system calls can return EINTR or restart. In order for the S48 vm's
;;; interrupt system to detect a signal and invoke the handler, they *must*
;;; return EINTR, and this must cause a return from C to Scheme.
;;;
;;; open close dup2 accept connect
;;; read recv recvfrom recvmsg
;;; write send sendto sendmsg
;;; select
;;; wait
;;; fcntl* ioctl
;;; sigsuspend
;;; HP-UX, but I don't use: poll lockf msem_lock msgsnd msgrcv semop
;;;
;;; * Only during a F_SETLKW
;;;
;;; From rts/interrupt.scm (package interrupts, interface interrupts-interface)
;;; WITH-INTERRUPTS INTERRUPT-HANDLERS SET-ENABLED-INTERRUPTS !
;;; ENABLED-INTERRUPTS
;;; Must define WITH-INTERRUPTS* and WITH-INTERRUPTS.
(foreign-init-name "sighandlers")
(foreign-source
"extern int errno;"
""
"/* Make sure foreign-function stubs interface to the C funs correctly: */"
"#include \"sighandlers1.h\""
"" "")
;;; Map a Unix async signal to its S48 interrupt value.
;;; -1 => Not defined.
(define-foreign %signal->interrupt (sig2interrupt (integer sig))
integer)
(define (signal->interrupt sig)
(let ((int (%signal->interrupt sig)))
(if (>= int 0) int
(error "Unix signal has no Scheme 48 interrupt." sig))))
(define (interrupt-set . interrupts)
(let lp ((ints interrupts) (ans 0))
(if (pair? ints)
(lp (cdr ints) (bitwise-ior ans (arithmetic-shift 1 (car ints) )))
ans)))
(define (interrupt-enabled? int mask)
(not (zero? (bitwise-and (arithmetic-shift 1 int) mask))))
(define (interrupt-enable int mask)
(bitwise-ior (arithmetic-shift 1 int) mask))
(define *enabled-interrupts*
(let lp ((i 0) (mask 0))
(if (= i number-of-interrupts)
mask
(lp (+ i 1) (interrupt-enable i mask)))))
(define (enabled-interrupts) *enabled-interrupts*)
;;; I'm trying to be consistent about the ! suffix -- I don't use it
;;; when frobbing process state. This is not a great rule; perhaps I
;;; should change it.
;;;
;;; I think you should...
(define (set-enabled-interrupts new-enabled-interrupts)
(do ((int 0 (+ int 1)))
((= int number-of-interrupts) new-enabled-interrupts)
(let ((old-state (interrupt-enabled? int *enabled-interrupts*))
(new-state (interrupt-enabled? int new-enabled-interrupts)))
(cond ((and old-state (not new-state))
(vector-set! blockade-vector int (block-interrupt int)))
((and (not old-state) new-state)
(let ((blockade (vector-ref blockade-vector int)))
(if (not blockade)
(error "there was no blockade" int))
(unblock-interrupt blockade)
(vector-set! blockade-vector int #f)))
(else 'unchanged))))
(set! *enabled-interrupts* new-enabled-interrupts))
;;; Enableing/Disableing = Unblocking/Blocking
;;;
;;; issues:
;;; + prevent delivery of the interrupt => install fake handler in
;;; low-interrupt
;;; + support setting of handler during blocking => install fake
;;; set-proc in interrupt-handler-vector
;;; + record if an interrupt occures while interupt blocked => pending?
;;; + restore everything after interrupt unublocked => reinstall handler
;;; in low-interrupt, set-proc in interrupt-handler-vector
;;; + if pending? interrupt: call handler
;(define-record-type blockade :blockade
; (really-make-blockade interrupt-vector-cell pending? low-int-set!)
; blockade?
; (interrupt-vector-cell blockade:interrupt-vector-cell)
; (pending? blockade:pending? set-blockade:pending?)
; (low-int-set! blockade:low-int-set!))
(define-record blockade
interrupt-vector-cell
low-int-set! ; proc to set interrupt in low-interrupt
(pending? #f))
(define blockade-vector (make-vector number-of-interrupts #f))
;;; do nothing in low-interrupt, the new handler will be recorded in the
;;; interrupt-handler-vector however
(define (fake-set-interrupt blockade)
(lambda (new-handler)
#f))
;;; to be installed in low-interrupt
(define (fake-handler blockade)
(lambda a
(if (not (blockade:pending? blockade))
(set-blockade:pending? blockade a))))
;;; generate blockade and install fake handler and set-proc
(define (block-interrupt int)
(let* ((handler-setter-cell (vector-ref *interrupt-handlers-vector* int))
(low-int-set! (cdr handler-setter-cell))
(blockade (make-blockade handler-setter-cell
low-int-set!)))
; fade out the low-interupt-set
(set-cdr! handler-setter-cell (fake-set-interrupt blockade))
; set the fake handler in low-interupt:
((blockade:low-int-set! blockade) (fake-handler blockade))
blockade))
(define (unblock-interrupt blockade)
(let ((handler (car (blockade:interrupt-vector-cell blockade))))
; install the handler that resides in the vector
(let ((low-int-set! (blockade:low-int-set! blockade)))
(low-int-set! handler)
; reinstall the low-interrupt-setter
(set-cdr! (blockade:interrupt-vector-cell blockade)
low-int-set!)
(if (blockade:pending? blockade)
(apply handler (blockade:pending? blockade))))))
(define-simple-syntax (with-enabled-interrupts interrupt-set body ...)
(begin
(with-enabled-interrupts* interrupt-set (lambda () body ...))))
(define (with-enabled-interrupts* interrupt-set thunk)
(let ((before *enabled-interrupts*))
(set-enabled-interrupts interrupt-set)
(let ((return (thunk)))
(set-enabled-interrupts before)
return)))
; Fakes vm vector
;;; car is the actual handler, cdr is a proc to set handler in
;;; low-interrupt system
(define *interrupt-handlers-vector*
(make-vector number-of-interrupts (cons #f #f)))
(define (interrupt-handlers-vector)
*interrupt-handlers-vector*)
(define (interrupt-handler-ref int)
(if (or (< int 0) (>= int number-of-interrupts))
(error "ill signum in interrupt-handler-ref" int)
(car (vector-ref *interrupt-handlers-vector* int))))
;;; the handler is not interested in the enabled interupts of the vm
;;; but in those managed here
(define (make-handler handler)
(lambda (enabled-low)
(handler (enabled-interrupts))))
(define (set-interrupt-handler! int handler)
(if (or (< int 0) (>= int number-of-interrupts))
(error "ill signum in set-interrupt-handler!" int)
(let ((handler-setter (vector-ref *interrupt-handlers-vector* int))
(handler-enabled-here (make-handler handler)))
(if (not (cdr handler-setter)) ; not yet registered?
(let ((setter (low-interrupt-register
int handler-enabled-here)))
(vector-set! *interrupt-handlers-vector*
int
(cons handler setter)))
(begin
((cdr handler-setter) handler-enabled-here) ; set it with setter
(set-car! (vector-ref *interrupt-handlers-vector* int)
handler))))))
;;; Get/Set signal handlers
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; When you set a signal's handler to "default," if the default for that
;;; signal is something other than "ignore," we actually install this guy.
;;; When he is called by the S48 interrupt system, he'll magically make
;;; the default action happen (by calling C code that *really* sets the
;;; handler to SIGDFL, and then re-sending the signal). This basically
;;; terminates the process, since if the default isn't "ignore," it's always
;;; "terminate" of some kind. Doing it this way means the exit code given
;;; to our waiting parent proc correctly reflects how we died, and also
;;; makes the core dump happen if it should. Details, details.
(define-foreign %do-default-sigaction (do_default_sigaction (fixnum signal))
ignore)
(define default-int-handler-vec
;; Non-Unix-signal interrupts just get their default values from
;; the current value of I-H.
(let ((v (make-vector 32)))
(do ((sig 31 (- sig 1))) ; For each Unix signal
((< sig 0)) ; make & install a default
(let ((i (%signal->interrupt sig))) ; signal handler.
(if (>= i 0) ; Don't mess with non-signal interrupts.
(vector-set! v i (if (memv sig signals-ignored-by-default)
(lambda (enabled-interrupts) #f)
(lambda (enabled-interrupts)
(%do-default-sigaction sig)))))))
v))
;(define default-int-handler-vec
; (let ((v (make-vector interrupt-count)))
; (do ((sig 31 (- sig 1))) ; For each Unix signal
; ((< sig 0)) ; make & install a default
; (let ((i (%signal->interrupt sig))) ; signal handler.
; (vector-set! v i (if (>= i 0) ; Don't mess with non-signal interrupts.
; (if (memv sig signals-ignored-by-default)
; (lambda (enabled-interrupts) #f)
; (lambda (enabled-interrupts)
; (%do-default-sigaction sig)))
; 'default-s48-interrupt-action))))
; v))
;;; HANDLER is #f (ignore), #t (default), or a procedure taking an integer
;;; argument. The interrupt is delivered to a procedure by (1) setting the
;;; ENABLED-INTERRUPTS register to 0 (i.e., blocking all interrupts), and (2)
;;; applying the procedure to the previous value of the ENABLED-INTERRUPTS
;;; register. If the procedure returns normally, the ENABLED-INTERRUPTS
;;; register will be restored to its previous value.
;;; This handler does nothing -- used when the handler is #f.
(define (noop-sig-handler enabled-interrupts) #f)
(define (set-interrupt-handler int handler)
(let ((ohandler (interrupt-handler int)))
(set-interrupt-handler!
int
(case handler
((#t) (vector-ref default-int-handler-vec int))
((#f) noop-sig-handler)
(else handler)))
ohandler))
; (cond ((and (not handler) ohandler ; Toggling from something
; (int->signal int)) => ; to ignored.
; (lambda (sig)
; (%set-unix-signal-handler sig 0)))
; ((and handler (not ohandler) ; Toggling from ignored
; (int->signal int)) => ; to something.
; (lambda (sig)
; (%set-unix-signal-handler sig 2))))
; ohandler))
(define (interrupt-handler int)
(let ((handler (interrupt-handler-ref int)))
(cond ((eq? handler (vector-ref default-int-handler-vec int)) #t)
((eq? handler noop-sig-handler) #f)
(else handler))))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Set the Unix signal handler. One doesn't usually use this; one usually
;;; uses the S48 VM's interrupt system.
;;; HANDLER-CODE: 0 => ignore, 1 => default, 2 => S48 VM
;;; Returns equivalent code, additionally 3 => other handler.
;;; Raises an error exception if there's a problem.
(define (%set-unix-signal-handler sig handler-code)
(check-arg (lambda (x) (and (integer? sig) (< 0 sig 32)))
sig
%set-unix-signal-handler)
(check-arg (lambda (x) (and (integer? handler-code) (<= 0 handler-code 2)))
handler-code
%set-unix-signal-handler)
(let retry ()
(receive (err old-hc old-flags)
(%%set-unix-signal-handler sig handler-code 0)
(cond ((not err) old-hc)
((= err errno/intr) (retry))
(else (errno-error err %set-unix-signal-handler sig handler-code))))))
(define-foreign %%set-unix-signal-handler
(scsh_set_sig (fixnum sig) (fixnum hc) (fixnum flags))
desc ; #f or errno
integer ; previous handler-code
integer) ; previous handler flags
(define (%unix-signal-handler sig)
(check-arg (lambda (x) (and (integer? sig) (< 0 sig 32)))
sig
%unix-signal-handler)
(let retry ()
(receive (err hc flags) (%%unix-signal-handler sig)
(cond ((not err) hc)
((= err errno/intr) (retry))
(else (errno-error err %unix-signal-handler sig))))))
(define-foreign %%unix-signal-handler (scsh_get_sig (fixnum sig))
desc ; #f or errno
integer ; previous handler-code
integer) ; previous handler flags
(define-foreign %install-unix-scsh-handlers (install_scsh_handlers) ignore)
(define-foreign %%get-int-handlers (get_int_handlers) desc)
(define (%install-scsh-handlers)
(do ((int 0 (+ int 1)))
((= int number-of-interrupts))
(set-interrupt-handler
int
(lambda a #f)))
(do ((sig 32 (- sig 1)))
((< sig 0))
(let ((i (%signal->interrupt sig)))
(if (not (or (= i -1)
(= sig signal/int) ; Leave ^c and
(= sig signal/alrm))) ; alarm handlers alone.
(set-interrupt-handler
i
(vector-ref default-int-handler-vec i))))))
;;; I am ashamed to say the 33 below is completely bogus.
;;; What we want is a value that is 1 + max interrupt value.
(define int->sig-vec
(let ((v (make-vector 33 #f)))
(do ((sig 32 (- sig 1)))
((< sig 0))
(let ((i (%signal->interrupt sig)))
(if (not (= i -1)) (vector-set! v i sig))))
v))
(define (int->signal i) (and (<= 0 i 32) (vector-ref int->sig-vec i)))