GCC 4.1 with i386-elf setjmp causes page fault

[ramsdell at mitre dot org (John D. Ramsdell)]

I built a cross-compiler targeted at i386-elf using binutils
2.16.91.0.6, gcc 4.1.0-20060328, and newlib 1.14.0.  I made one change
to newlib--I removed the #ifdef HAVE_GETTIMEOFDAY in time.c.

I used the cross compiler to compile Mini-OS, a small kernel that can
be run using the Xen hypervisor.  The result runs with no obvious
problems.  

I modified the code that implements the console in Mini-OS so that it
exercises setjmp and longjmp.  A page fault occurs when longjmp is
called.  Even stranger, it appears that the address being referenced
is actually a segment descriptor.  Could it be that GCC 4 generates
code that does not work with the newlib's version of setjmp and
longjmp? 

I'm not sure how to provide a better bug report, but I'll supply more
details upon request.  One other thing I did was write a very simple
main routine, and compiled and linked it with
./newlib/libc/machine/i386/{setjmp.S,i386mach.h} using the native GCC,
version 3.3.5.  It also crashes, but I'm not sure what that proves.

John

Attachment: main.c
Description: setjmp main

diff -ur oxen-unstable/extras/mini-os/console/console.c xen-unstable/extras/mini-os/console/console.c
--- oxen-unstable/extras/mini-os/console/console.c	2006-04-29 00:24:30.000000000 -0400
+++ xen-unstable/extras/mini-os/console/console.c	2006-05-02 14:15:30.000000000 -0400
@@ -44,7 +44,26 @@
 #include <xenbus.h>
 #include <xen/io/console.h>
 
+#if defined LUA_CONSOLE
 
+#include <setjmp.h>
+
+void do_jump(jmp_buf env) {
+  printk("About to jump\n");
+  longjmp(env, 1);
+  printk("Missed the jump\n");
+}
+
+void do_setup(void) {
+  jmp_buf env;
+  if (setjmp(env))
+    return;
+  do_jump(env);
+  printk("landed\n");
+}
+
+#endif
+    
 /* Low level functions defined in xencons_ring.c */
 extern int xencons_ring_init(void);
 extern int xencons_ring_send(const char *data, unsigned len);
@@ -64,8 +83,10 @@
         buf[len] = '\0';
         printk("%s", buf);
         
-        if(buf[len-1] == '\r')
-            printk("\nNo console input handler.\n");
+        if(buf[len-1] == '\r') {
+            printk("\nTrying setjmp.\n");
+	    do_setup();
+	}
     }
 }