[src/trunk]: src/sys/arch/xen/x86 Revert to 1.59 (adding back the W^X kernel ...

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

details:   https://anonhg.NetBSD.org/src/rev/d266a8d3d017
branches:  trunk
changeset: 817564:d266a8d3d017
user:      bouyer <bouyer%NetBSD.org@localhost>
date:      Thu Aug 25 17:03:57 2016 +0000

description:
Revert to 1.59 (adding back the W^X kernel mapings), and move the data+bss
mapping late so that mappings that should be RO (such as page tables) won't
be made RW by accident.

diffstat:

 sys/arch/xen/x86/x86_xpmap.c |  57 ++++++++++++++++++++++++++++++-------------
 1 files changed, 40 insertions(+), 17 deletions(-)

diffs (132 lines):

diff -r 12fa9daedf10 -r d266a8d3d017 sys/arch/xen/x86/x86_xpmap.c
--- a/sys/arch/xen/x86/x86_xpmap.c      Thu Aug 25 13:17:09 2016 +0000
+++ b/sys/arch/xen/x86/x86_xpmap.c      Thu Aug 25 17:03:57 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: x86_xpmap.c,v 1.60 2016/08/23 11:03:52 bouyer Exp $    */
+/*     $NetBSD: x86_xpmap.c,v 1.61 2016/08/25 17:03:57 bouyer Exp $    */
 
 /*
  * Copyright (c) 2006 Mathieu Ropert <mro%adviseo.fr@localhost>
@@ -69,7 +69,7 @@
 
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: x86_xpmap.c,v 1.60 2016/08/23 11:03:52 bouyer Exp $");
+__KERNEL_RCSID(0, "$NetBSD: x86_xpmap.c,v 1.61 2016/08/25 17:03:57 bouyer Exp $");
 
 #include "opt_xen.h"
 #include "opt_ddb.h"
@@ -730,15 +730,24 @@
        pd_entry_t *pdtpe, *pde, *pte;
        pd_entry_t *bt_pgd;
        paddr_t addr;
-       vaddr_t page, avail, text_end, map_end;
+       vaddr_t page, avail, map_end;
        int i;
+       extern char __rodata_start;
        extern char __data_start;
+       extern char __kernel_end;
        extern char *early_zerop; /* from pmap.c */
+       pt_entry_t pg_nx;
+       u_int descs[4];
 
        __PRINTK(("xen_bootstrap_tables(%#" PRIxVADDR ", %#" PRIxVADDR ","
            " %d, %d)\n",
            old_pgd, new_pgd, old_count, new_count));
-       text_end = ((vaddr_t)&__data_start) & ~PAGE_MASK;
+
+       /*
+        * Set the NX/XD bit, if available. descs[3] = %edx.
+        */
+       x86_cpuid(0x80000001, descs);
+       pg_nx = (descs[3] & CPUID_NOX) ? PG_NX : 0;
 
        /*
         * size of R/W area after kernel text:
@@ -776,8 +785,7 @@
        }
 #endif /* DOM0OPS */
 
-       __PRINTK(("xen_bootstrap_tables text_end 0x%lx map_end 0x%lx\n",
-           text_end, map_end));
+       __PRINTK(("xen_bootstrap_tables map_end 0x%lx\n", map_end));
        __PRINTK(("console %#lx ", xen_start_info.console_mfn));
        __PRINTK(("xenstore %#" PRIx32 "\n", xen_start_info.store_mfn));
 
@@ -905,20 +913,26 @@
                            page < (vaddr_t)atdevbase + IOM_SIZE) {
                                pte[pl1_pi(page)] =
                                    IOM_BEGIN + (page - (vaddr_t)atdevbase);
+                               pte[pl1_pi(page)] |= pg_nx;
                        }
 #endif
+
                        pte[pl1_pi(page)] |= PG_k | PG_V;
-                       if (page < text_end) {
-                               /* map kernel text RO */
+                       if (page < (vaddr_t)&__rodata_start) {
+                               /* Map the kernel text RX. */
                                pte[pl1_pi(page)] |= PG_RO;
+                       } else if (page >= (vaddr_t)&__rodata_start &&
+                           page < (vaddr_t)&__data_start) {
+                               /* Map the kernel rodata R. */
+                               pte[pl1_pi(page)] |= PG_RO | pg_nx;
                        } else if (page >= old_pgd &&
                            page < old_pgd + (old_count * PAGE_SIZE)) {
-                               /* map old page tables RO */
-                               pte[pl1_pi(page)] |= PG_RO;
+                               /* Map the old page tables R. */
+                               pte[pl1_pi(page)] |= PG_RO | pg_nx;
                        } else if (page >= new_pgd &&
                            page < new_pgd + ((new_count + l2_4_count) * PAGE_SIZE)) {
-                               /* map new page tables RO */
-                               pte[pl1_pi(page)] |= PG_RO;
+                               /* Map the new page tables R. */
+                               pte[pl1_pi(page)] |= PG_RO | pg_nx;
 #ifdef i386
                        } else if (page == (vaddr_t)tmpgdt) {
                                /*
@@ -931,6 +945,10 @@
                                page += PAGE_SIZE;
                                continue;
 #endif /* i386 */
+                       } else if (page >= (vaddr_t)&__data_start &&
+                           page < (vaddr_t)&__kernel_end) {
+                               /* Map the kernel data+bss RW. */
+                               pte[pl1_pi(page)] |= PG_RW | pg_nx;
                        } else {
                                /* map page RW */
                                pte[pl1_pi(page)] |= PG_RW;
@@ -1011,15 +1029,19 @@
        xpq_queue_pin_l2_table(xpmap_ptom_masked(addr));
 #endif
 #else /* PAE */
-       /* recursive entry in higher-level per-cpu PD and pmap_kernel() */
-       bt_pgd[PDIR_SLOT_PTE] = xpmap_ptom_masked((paddr_t)bt_pgd - KERNBASE) | PG_k | PG_V;
+
+       /* Recursive entry in pmap_kernel(). */
+       bt_pgd[PDIR_SLOT_PTE] = xpmap_ptom_masked((paddr_t)bt_pgd - KERNBASE)
+           | PG_k | PG_RO | PG_V | pg_nx;
 #ifdef __x86_64__
-          bt_cpu_pgd[PDIR_SLOT_PTE] =
-                  xpmap_ptom_masked((paddr_t)bt_cpu_pgd - KERNBASE) | PG_k | PG_V;
-#endif /* __x86_64__ */
+       /* Recursive entry in higher-level per-cpu PD. */
+       bt_cpu_pgd[PDIR_SLOT_PTE] = xpmap_ptom_masked((paddr_t)bt_cpu_pgd - KERNBASE)
+           | PG_k | PG_RO | PG_V | pg_nx;
+#endif
        __PRINTK(("bt_pgd[PDIR_SLOT_PTE] va %#" PRIxVADDR " pa %#" PRIxPADDR
            " entry %#" PRIxPADDR "\n", new_pgd, (paddr_t)new_pgd - KERNBASE,
            bt_pgd[PDIR_SLOT_PTE]));
+
        /* Mark tables RO */
        xen_bt_set_readonly((vaddr_t) pde);
 #endif
@@ -1029,6 +1051,7 @@
 #if PTP_LEVELS > 3
        xen_bt_set_readonly(new_pgd);
 #endif
+
        /* Pin the PGD */
        __PRINTK(("pin PGD: %"PRIxVADDR"\n", new_pgd - KERNBASE));
 #ifdef __x86_64__