0.pre7.129:

[sbcl.git] / src / runtime / interrupt.c

diff --git a/src/runtime/interrupt.c b/src/runtime/interrupt.c
index ecc3b84..4c56a0a 100644 (file)
--- a/src/runtime/interrupt.c
+++ b/src/runtime/interrupt.c
@@ -14,6 +14,7 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 
 #include <signal.h>
 #ifdef mach /* KLUDGE: #ifdef on lowercase symbols? Ick. -- WHN 19990904 */
@@ -139,8 +140,8 @@ fake_foreign_function_call(os_context_t *context)
        == current_control_frame_pointer) {
         /* There is a small window during call where the callee's
          * frame isn't built yet. */
-        if (LowtagOf(*os_context_register_addr(context, reg_CODE))
-           == type_FunctionPointer) {
+        if (lowtag_of(*os_context_register_addr(context, reg_CODE))
+           == FUN_POINTER_LOWTAG) {
             /* We have called, but not built the new frame, so
              * build it for them. */
             current_control_frame_pointer[0] =
@@ -213,6 +214,7 @@ undo_fake_foreign_function_call(os_context_t *context)
      * FREE_INTERRUPT_CONTEXT_INDEX? If so, we should say so. And
      * perhaps yes, unbind_to_here() really would be clearer and less
      * fragile.. */
+    /* dan (2001.08.10) thinks the above supposition is probably correct */
     unbind();
 
 #ifdef reg_ALLOC
@@ -389,7 +391,7 @@ interrupt_handle_now(int signal, siginfo_t *info, void *void_context)
         * support decides to pass on it. */
        lose("no handler for signal %d in interrupt_handle_now(..)", signal);
 
-    } else if (LowtagOf(handler.lisp) == type_FunctionPointer) {
+    } else if (lowtag_of(handler.lisp) == FUN_POINTER_LOWTAG) {
 
         /* Allocate the SAPs while the interrupts are still disabled.
         * (FIXME: Why? This is the way it was done in CMU CL, and it
@@ -565,22 +567,78 @@ interrupt_maybe_gc(int signal, siginfo_t *info, void *void_context)
  * noise to install handlers
  */
 
-/* Install a special low-level handler for signal; or if handler is
- * SIG_DFL, remove any special handling for signal. */
+/*
+ * what low-level signal handlers looked like before
+ * undoably_install_low_level_interrupt_handler() got involved
+ */
+struct low_level_signal_handler_state {
+    int was_modified;
+    void (*handler)(int, siginfo_t*, void*);
+} old_low_level_signal_handler_states[NSIG];
+
+void
+uninstall_low_level_interrupt_handlers_atexit(void)
+{
+    int signal;
+    for (signal = 0; signal < NSIG; ++signal) {
+       struct low_level_signal_handler_state
+           *old_low_level_signal_handler_state =
+           old_low_level_signal_handler_states + signal;
+       if (old_low_level_signal_handler_state->was_modified) {
+           struct sigaction sa;
+           sa.sa_sigaction = old_low_level_signal_handler_state->handler;
+           sigemptyset(&sa.sa_mask);
+           sa.sa_flags = SA_SIGINFO | SA_RESTART; 
+           sigaction(signal, &sa, NULL);
+       }
+    }
+}
+
+/* Undoably install a special low-level handler for signal; or if
+ * handler is SIG_DFL, remove any special handling for signal.
+ *
+ * The "undoably" aspect is because we also arrange with atexit() for
+ * the handler to be restored to its old value. This is for tidiness:
+ * it shouldn't matter much ordinarily, but it does remove a window
+ * where e.g. memory fault signals (SIGSEGV or SIGBUS, which in
+ * ordinary operation of SBCL are sent to the generational garbage
+ * collector, then possibly onward to Lisp code) or SIGINT (which is
+ * ordinarily passed to Lisp code) could otherwise be handled
+ * bizarrely/brokenly because the Lisp code would try to deal with
+ * them using machinery (like stream output buffers) which has already
+ * been dismantled. */
 void
-interrupt_install_low_level_handler (int signal,
-                                    void handler(int, siginfo_t*, void*))
+undoably_install_low_level_interrupt_handler (int signal,
+                                             void handler(int,
+                                                          siginfo_t*,
+                                                          void*))
 {
     struct sigaction sa;
+    struct low_level_signal_handler_state *old_low_level_signal_handler_state =
+       old_low_level_signal_handler_states + signal;
+
+    if (0 > signal || signal >= NSIG) {
+       lose("bad signal number %d", signal);
+    }
 
     sa.sa_sigaction = handler;
     sigemptyset(&sa.sa_mask);
     sigaddset_blockable(&sa.sa_mask);
     sa.sa_flags = SA_SIGINFO | SA_RESTART;
 
-    sigaction(signal, &sa, NULL);
+    /* In the case of interrupt handlers which are modified more than
+     * once, we only save the original unmodified copy. */
+    if (!old_low_level_signal_handler_state->was_modified) {
+       struct sigaction *old_handler =
+           (struct sigaction*) &old_low_level_signal_handler_state->handler;
+       old_low_level_signal_handler_state->was_modified = 1;
+       sigaction(signal, &sa, old_handler);
+    } else {
+       sigaction(signal, &sa, NULL);
+    }
+
     interrupt_low_level_handlers[signal] =
-       (ARE_SAME_HANDLER(handler,SIG_DFL) ? 0 : handler);
+       (ARE_SAME_HANDLER(handler, SIG_DFL) ? 0 : handler);
 }
 
 /* This is called from Lisp. */
@@ -635,6 +693,11 @@ interrupt_init(void)
     int i;
 
     SHOW("entering interrupt_init()");
+
+    /* Set up for recovery from any installed low-level handlers. */
+    atexit(&uninstall_low_level_interrupt_handlers_atexit);
+
+    /* Set up high level handler information. */
     for (i = 0; i < NSIG; i++) {
         interrupt_handlers[i].c =
            /* (The cast here blasts away the distinction between
@@ -644,5 +707,6 @@ interrupt_init(void)
             * 3-argument form is expected.) */
            (void (*)(int, siginfo_t*, void*))SIG_DFL;
     }
+
     SHOW("returning from interrupt_init()");
 }