Re: bin/47271: host (1) dumps core on latest netbsd-6

[Taylor R Campbell <campbell+netbsd%mumble.net@localhost>]

The attached patch works around the problem, at least on amd64, but I
think we ought to discuss whether it is actually appropriate to double
the size of each pthread for the thread-specific data deletion kludge,
both in HEAD and in netbsd-6.  For now, until that discussion happens,
riz has reverted the TSD change in netbsd-6.

Index: lib/libpthread/pthread.c
===================================================================
RCS file: /cvsroot/src/lib/libpthread/pthread.c,v
retrieving revision 1.125.4.1
diff -p -u -r1.125.4.1 pthread.c
--- lib/libpthread/pthread.c    7 May 2012 03:12:33 -0000       1.125.4.1
+++ lib/libpthread/pthread.c    2 Dec 2012 18:50:03 -0000
@@ -1274,22 +1274,32 @@ pthread__stackid_setup(void *base, size_
 {
        pthread_t t;
        void *redaddr;
-       size_t pagesize;
+       size_t pagesize, bytes_needed;
        int ret;
 
        t = base;
        pagesize = (size_t)sysconf(_SC_PAGESIZE);
+       bytes_needed = roundup(sizeof(*t), pagesize);
+
+       if (pagesize >= size)
+               return ENOMEM;
+       if (bytes_needed >= (size - pagesize))
+               return ENOMEM;
 
        /*
         * Put a pointer to the pthread in the bottom (but
          * redzone-protected section) of the stack. 
+        *
+        * XXX If the stack grows up, the pthread is *not*
+        * protected by the redzone.
         */
-       redaddr = STACK_SHRINK(STACK_MAX(base, size), pagesize);
-       t->pt_stack.ss_size = size - 2 * pagesize;
+       t->pt_stack.ss_size = size - bytes_needed - pagesize;
 #ifdef __MACHINE_STACK_GROWS_UP
-       t->pt_stack.ss_sp = (char *)(void *)base + pagesize;
+       redaddr = STACK_SHRINK(STACK_MAX(base, size), pagesize);
+       t->pt_stack.ss_sp = (char *)(void *)base + bytes_needed;
 #else
-       t->pt_stack.ss_sp = (char *)(void *)base + 2 * pagesize;
+       redaddr = STACK_SHRINK(STACK_MAX(base, size), bytes_needed);
+       t->pt_stack.ss_sp = (char *)(void *)base + bytes_needed + pagesize;
 #endif
        /* Protect the next-to-bottom stack page as a red zone. */
        ret = mprotect(redaddr, pagesize, PROT_NONE);