Index: linux-user/signal.c
===================================================================
RCS file: /cvsroot/qemu/qemu/linux-user/signal.c,v
retrieving revision 1.27
diff -u -r1.27 signal.c
--- linux-user/signal.c	30 Jan 2005 22:59:18 -0000	1.27
+++ linux-user/signal.c	22 Mar 2005 12:42:30 -0000
@@ -1019,6 +1026,14 @@
 	return err;
 }
 
+void* hack_stack;
+
+void hack_handler(int signum)
+{
+  fprintf(stderr,"QEMU: stack overflow, aborting\n");
+  exit(-SIGSEGV);
+}
+
 static inline void *
 get_sigframe(struct emulated_sigaction *ka, CPUState *regs, int framesize)
 {
@@ -1031,6 +1046,19 @@
 	if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
 		sp = current->sas_ss_sp + current->sas_ss_size;
 #endif
+
+        /* EVIL HACK TIME!
+           This is supposed to prevent endless segfault loops in case of stack
+           overflows that can occur as a result of the dummy sigaltstack()
+           syscall. */
+        struct sigaction oldact;
+        struct sigaction act;
+        memset(&act,0,sizeof(struct sigaction));
+        act.sa_handler=hack_handler;
+        sigaction(SIGSEGV,&act,&oldact);
+        hack_stack = *((void**)((sp-framesize)&~7));
+        sigaction(SIGSEGV,&oldact,&act);
+
 	/*
 	 * ATPCS B01 mandates 8-byte alignment
 	 */
Index: linux-user/syscall.c
===================================================================
RCS file: /cvsroot/qemu/qemu/linux-user/syscall.c,v
retrieving revision 1.58
diff -u -r1.58 syscall.c
--- linux-user/syscall.c	1 Mar 2005 22:32:06 -0000	1.58
+++ linux-user/syscall.c	22 Mar 2005 12:42:30 -0000
@@ -2725,7 +2734,8 @@
     case TARGET_NR_capset:
         goto unimplemented;
     case TARGET_NR_sigaltstack:
-        goto unimplemented;
+        ret = 0; /* good enough for most purposes */
+        break;
     case TARGET_NR_sendfile:
         goto unimplemented;
 #ifdef TARGET_NR_getpmsg