Re: Hang in E01 due to zpty on OpenBSD

[Matthew Martin <phy1729@gmail.com>]

On Sun, Apr 03, 2022 at 06:04:30PM -0700, Bart Schaefer wrote:
> On Sun, Apr 3, 2022 at 2:43 PM Matthew Martin <phy1729@gmail.com> wrote:
> >
> > I assume the EPERM on open is an OpenBSD bug, but zsh should probably
> > not hang either.
> 
> I'm not sure what could be done about this from the zsh code.  The
> only reasonable assumption for the pty master-side reader is that the
> slave-slide will become closed upon an error and the read will fail.
> Using a non-blocking read would defeat the purpose.

The only reasonable thing I can come up with is open both pty and tty on
the first call to get_pty, so the second call can't fail. 

The tests pass when I use openpty; though since that's in libutil and
I didn't immedietly see a way to link that in, there's a terrible work
around with dlopen/dlsym. I have no intention to commit this.

I've sent a mail to OpenBSD. I don't think this should block the
release. Worst case there will be a patch in the port that can be
upstreamed by the next release.


diff --git a/Src/Modules/zpty.c b/Src/Modules/zpty.c
index dfd2a2a7a..3f21c2b89 100644
--- a/Src/Modules/zpty.c
+++ b/Src/Modules/zpty.c
@@ -37,6 +37,12 @@
 #endif
 #endif
 
+#ifdef __OpenBSD__
+#include <dlfcn.h>
+#include <termios.h>
+#include <util.h>
+#endif
+
 /* The number of bytes we normally read when given no pattern and the
  * upper bound on the number of bytes we read (even if we are give a
  * pattern). */
@@ -161,8 +167,38 @@ getptycmd(char *name)
     return NULL;
 }
 
-/* posix_openpt() seems to have some problem on OpenBSD */
-#if defined(USE_DEV_PTMX) && !defined(__OpenBSD__)
+#if defined(__OpenBSD__)
+
+static int
+get_pty(int master, int *retfd)
+{
+    static int mfd, sfd;
+
+    if (master) {
+	void *handle;
+	int (*openpty)(int *, int *, char *, struct termios *, struct winsize *);
+
+	if ((handle = dlopen("libutil.so", 0)) == NULL) {
+	    return 1;
+	}
+	if ((openpty = dlsym(handle, "openpty")) == NULL) {
+	    dlclose(handle);
+	    return 1;
+	}
+	if (openpty(&mfd, &sfd, NULL, NULL, NULL) == -1) {
+	    dlclose(handle);
+	    return 1;
+	}
+	dlclose(handle);
+	*retfd = mfd;
+	return 0;
+    }
+
+    *retfd = sfd;
+    return 0;
+}
+
+#elif defined(USE_DEV_PTMX)
 
 #ifdef HAVE_SYS_STROPTS_H
 #include <sys/stropts.h>
@@ -261,12 +297,7 @@ get_pty(int master, int *retfd)
 #elif defined(__FreeBSD__) || defined(__DragonFly__)
     static char char1[] = "pqrsPQRS";
     static char char2[] = "0123456789abcdefghijklmnopqrstuv";
-#elif defined(__OpenBSD__)
-    static char char1[] = "pqrstuvwxyzPQRST";
-    static char char2[] = "0123456789"
-                          "abcdefghijklmnopqrstuvwxyz"
-                          "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
-#else /* __FreeBSD__ || __DragonFly__  || __OpenBSD*/
+#else /* __FreeBSD__ || __DragonFly__ */
     static char char1[] = "pqrstuvwxyzPQRST";
     static char char2[] = "0123456789abcdef";
 #endif