[src/trunk]: src/sys/uvm/pmap fix the start index generation in pmap_segtab_r...

[mrg <mrg%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/6d4c88d83b5b
branches:  trunk
changeset: 349081:6d4c88d83b5b
user:      mrg <mrg%NetBSD.org@localhost>
date:      Wed Nov 23 03:30:53 2016 +0000

description:
fix the start index generation in pmap_segtab_release() to
ensure it fits in the actual array.  fixes N64 binaries from
triggering later panic.  move the panic check itself into a
common function that is called from a couple of new places too.

diffstat:

 sys/uvm/pmap/pmap_segtab.c |  40 +++++++++++++++++++++++++++++++---------
 1 files changed, 31 insertions(+), 9 deletions(-)

diffs (103 lines):

diff -r 6e8adda0026f -r 6d4c88d83b5b sys/uvm/pmap/pmap_segtab.c
--- a/sys/uvm/pmap/pmap_segtab.c        Wed Nov 23 03:02:56 2016 +0000
+++ b/sys/uvm/pmap/pmap_segtab.c        Wed Nov 23 03:30:53 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap_segtab.c,v 1.3 2016/07/11 16:06:09 matt Exp $     */
+/*     $NetBSD: pmap_segtab.c,v 1.4 2016/11/23 03:30:53 mrg Exp $      */
 
 /*-
  * Copyright (c) 1998, 2001 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
 
 #include <sys/cdefs.h>
 
-__KERNEL_RCSID(0, "$NetBSD: pmap_segtab.c,v 1.3 2016/07/11 16:06:09 matt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap_segtab.c,v 1.4 2016/11/23 03:30:53 mrg Exp $");
 
 /*
  *     Manages physical address maps.
@@ -130,6 +130,24 @@
 
 kmutex_t pmap_segtab_lock __cacheline_aligned;
 
+static void
+pmap_check_stp(pmap_segtab_t *stp, const char *caller, const char *why)
+{
+#ifdef DEBUG
+       for (size_t i = 0; i < PMAP_SEGTABSIZE; i++) {
+               if (stp->seg_tab[i] != 0) {
+#ifdef DEBUG_NOISY
+                       for (size_t j = i; j < PMAP_SEGTABSIZE; j++)
+                               printf("%s: pm_segtab.seg_tab[%zu] = 0x%p\n",
+                                      caller, j, stp->seg_tab[j]);
+#endif
+                       panic("%s: pm_segtab.seg_tab[%zu] != 0 (0x%p): %s",
+                             caller, i, stp->seg_tab[i], why);
+               }
+       }
+#endif
+}
+
 static inline struct vm_page *
 pmap_pte_pagealloc(void)
 {
@@ -190,7 +208,9 @@
 {
        pmap_segtab_t *stp = *stp_p;
 
-       for (size_t i = va / vinc; i < PMAP_SEGTABSIZE; i++, va += vinc) {
+       for (size_t i = (va / vinc) & (PMAP_SEGTABSIZE - 1);
+            i < PMAP_SEGTABSIZE;
+            i++, va += vinc) {
 #ifdef _LP64
                if (vinc > NBSEG) {
                        if (stp->seg_seg[i] != NULL) {
@@ -236,6 +256,8 @@
        }
 
        if (free_stp) {
+               pmap_check_stp(stp, __func__, 
+                              vinc == NBSEG ? "release seg" : "release xseg");
                pmap_segtab_free(stp);
                *stp_p = NULL;
        }
@@ -257,6 +279,7 @@
 pmap_segtab_alloc(void)
 {
        pmap_segtab_t *stp;
+       bool found_on_freelist = false;
 
  again:
        mutex_spin_enter(&pmap_segtab_lock);
@@ -264,6 +287,7 @@
                pmap_segtab_info.free_segtab = stp->seg_seg[0];
                stp->seg_seg[0] = NULL;
                SEGTAB_ADD(nget, 1);
+               found_on_freelist = true;
        }
        mutex_spin_exit(&pmap_segtab_lock);
 
@@ -300,12 +324,9 @@
                }
        }
 
-#ifdef DEBUG
-       for (size_t i = 0; i < PMAP_SEGTABSIZE; i++) {
-               if (stp->seg_tab[i] != 0)
-                       panic("%s: pm_segtab.seg_tab[%zu] != 0", __func__, i);
-       }
-#endif
+       pmap_check_stp(stp, __func__,
+                      found_on_freelist ? "from free list" : "allocated");
+
        return stp;
 }
 
@@ -420,6 +441,7 @@
 #ifdef MULTIPROCESSOR
                        pmap_segtab_t *ostp = atomic_cas_ptr(stp_p, NULL, nstp);
                        if (__predict_false(ostp != NULL)) {
+                               pmap_check_stp(nstp, __func__, "reserve");
                                pmap_segtab_free(nstp);
                                nstp = ostp;
                        }