Use interruptible syscalls instead of setjmp/longjmp. This makes

less's signal handlers safe.  No one has reported problems so far...

4 files changed, 21 insertions, 74 deletions

diff --git a/usr.bin/less/funcs.h b/usr.bin/less/funcs.h
index 4ee00d493f6..5fab0efdf6a 100644
--- a/usr.bin/less/funcs.h
+++ b/usr.bin/less/funcs.h
@@ -195,7 +195,6 @@
 	public struct loption * findopt ();
 	public struct loption * findopt_name ();
 	public int iread ();
-	public void intread ();
 	public long get_time ();
 	public char * errno_message ();
 	public int percentage ();
@@ -249,3 +248,4 @@
 	public void open_getchr ();
 	public void close_getchr ();
 	public int getchr ();
+	public void (*lsignal()) ();
diff --git a/usr.bin/less/less.h b/usr.bin/less/less.h
index 07911d5ce7d..abb60f323c5 100644
--- a/usr.bin/less/less.h
+++ b/usr.bin/less/less.h
@@ -374,7 +374,7 @@ struct textlist
 #if _OSK_MWC32
 #define	LSIGNAL(sig,func)	os9_signal(sig,func)
 #else
-#define	LSIGNAL(sig,func)	signal(sig,func)
+#define	LSIGNAL(sig,func)	lsignal(sig,func)
 #endif
 
 #if HAVE_SIGPROCMASK
diff --git a/usr.bin/less/os.c b/usr.bin/less/os.c
index ac63960df95..c5343a043a8 100644
--- a/usr.bin/less/os.c
+++ b/usr.bin/less/os.c
@@ -23,7 +23,6 @@
 
 #include "less.h"
 #include <signal.h>
-#include <setjmp.h>
 #if HAVE_TIME_H
 #include <time.h>
 #endif
@@ -40,31 +39,10 @@
 #define	time_type	long
 #endif
 
-/*
- * BSD setjmp() saves (and longjmp() restores) the signal mask.
- * This costs a system call or two per setjmp(), so if possible we clear the
- * signal mask with sigsetmask(), and use _setjmp()/_longjmp() instead.
- * On other systems, setjmp() doesn't affect the signal mask and so
- * _setjmp() does not exist; we just use setjmp().
- */
-#if HAVE__SETJMP && HAVE_SIGSETMASK
-#define SET_JUMP	_setjmp
-#define LONG_JUMP	_longjmp
-#else
-#define SET_JUMP	setjmp
-#define LONG_JUMP	longjmp
-#endif
-
-public int reading;
-
-static jmp_buf read_label;
-
 extern int sigs;
 
 /*
  * Like read() system call, but is deliberately interruptible.
- * A call to intread() from a signal handler will interrupt
- * any pending iread().
  */
 	public int
 iread(fd, buf, len)
@@ -90,32 +68,8 @@ iread(fd, buf, len)
 	}
 #endif
 #endif
-	if (SET_JUMP(read_label))
-	{
-		/*
-		 * We jumped here from intread.
-		 */
-		reading = 0;
-#if HAVE_SIGPROCMASK
-		{
-		  sigset_t mask;
-		  sigemptyset(&mask);
-		  sigprocmask(SIG_SETMASK, &mask, NULL);
-		}
-#else
-#if HAVE_SIGSETMASK
-		sigsetmask(0);
-#else
-#ifdef _OSK
-		sigmask(~0);
-#endif
-#endif
-#endif
-		return (READ_INTR);
-	}
 
 	flush();
-	reading = 1;
 #if MSDOS_COMPILER==DJGPPC
 	if (isatty(fd))
 	{
@@ -154,22 +108,12 @@ iread(fd, buf, len)
 		}
 	}
 #endif
-	reading = 0;
 	if (n < 0)
-		return (-1);
+		return (errno == EINTR ? READ_INTR : -1);
 	return (n);
 }
 
 /*
- * Interrupt a pending iread().
- */
-	public void
-intread()
-{
-	LONG_JUMP(read_label, 1);
-}
-
-/*
  * Return the current time.
  */
 #if HAVE_TIME
diff --git a/usr.bin/less/signal.c b/usr.bin/less/signal.c
index a641d99ee9d..01b510f73e8 100644
--- a/usr.bin/less/signal.c
+++ b/usr.bin/less/signal.c
@@ -15,8 +15,6 @@
  * A signal usually merely causes a bit to be set in the "signals" word.
  * At some convenient time, the mainline code checks to see if any
  * signals need processing by calling psignal().
- * If we happen to be reading from a file [in iread()] at the time
- * the signal is received, we call intread to interrupt the iread.
  */
 
 #include "less.h"
@@ -32,7 +30,6 @@ extern int screen_trashed;
 extern int lnloop;
 extern int linenums;
 extern int wscroll;
-extern int reading;
 
 /*
  * Interrupt signal handler.
@@ -45,7 +42,6 @@ u_interrupt(type)
 #if OS2
 	LSIGNAL(SIGINT, SIG_ACK);
 #endif
-	LSIGNAL(SIGINT, u_interrupt);
 	sigs |= S_INTERRUPT;
 #if MSDOS_COMPILER==DJGPPC
 	/*
@@ -56,8 +52,6 @@ u_interrupt(type)
 	if (kbhit())
 		getkey();
 #endif
-	if (reading)
-		intread();
 }
 
 #ifdef SIGTSTP
@@ -69,10 +63,7 @@ u_interrupt(type)
 stop(type)
 	int type;
 {
-	LSIGNAL(SIGTSTP, stop);
 	sigs |= S_STOP;
-	if (reading)
-		intread();
 }
 #endif
 
@@ -85,10 +76,7 @@ stop(type)
 winch(type)
 	int type;
 {
-	LSIGNAL(SIGWINCH, winch);
 	sigs |= S_WINCH;
-	if (reading)
-		intread();
 }
 #else
 #ifdef SIGWIND
@@ -100,10 +88,7 @@ winch(type)
 winch(type)
 	int type;
 {
-	LSIGNAL(SIGWIND, winch);
 	sigs |= S_WINCH;
-	if (reading)
-		intread();
 }
 #endif
 #endif
@@ -268,3 +253,21 @@ psignals()
 
 	}
 }
+
+/*
+ * Custom version of signal() that causes syscalls to be interrupted.
+ */
+	public void
+(*lsignal(s, a))()
+	int s;
+	void (*a) ();
+{
+	struct sigaction sa, osa;
+
+	sa.sa_handler = a;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = 0;		/* don't restart system calls */
+	if (sigaction(s, &sa, &osa) != 0)
+		return (SIG_ERR);
+	return (osa.sa_handler);
+}