From: Keir Fraser <keir.fraser@citrix.com>
Date: Thu, 8 Jan 2009 13:21:06 +0000 (+0000)
Subject: x86: Re-instate warnings for HVM guest writes to read-only memory.
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~14014^2~92
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=21b9b29dc4008f7466b45561f8846d87c775730f;p=xen.git

x86: Re-instate warnings for HVM guest writes to read-only memory.
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
---

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index fdcea74097..0d13a79a5f 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1503,7 +1503,15 @@ static enum hvm_copy_result __hvm_copy(
 
         if ( flags & HVMCOPY_to_guest )
         {
-            if ( p2mt != p2m_ram_ro )
+            if ( p2mt == p2m_ram_ro )
+            {
+                static unsigned long lastpage;
+                if ( xchg(&lastpage, gfn) != gfn )
+                    gdprintk(XENLOG_DEBUG, "guest attempted write to read-only"
+                             " memory page. gfn=%#lx, mfn=%#lx\n",
+                             gfn, mfn);
+            }
+            else
             {
                 memcpy(p, buf, count);
                 paging_mark_dirty(curr->domain, mfn);
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index 5f335177d0..338b8cf5dd 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -3230,7 +3230,14 @@ static int sh_page_fault(struct vcpu *v,
 
     /* Ignore attempts to write to read-only memory. */
     if ( (p2mt == p2m_ram_ro) && (ft == ft_demand_write) )
+    {
+        static unsigned long lastpage;
+        if ( xchg(&lastpage, va & PAGE_MASK) != (va & PAGE_MASK) )
+            gdprintk(XENLOG_DEBUG, "guest attempted write to read-only memory"
+                     " page. va page=%#lx, mfn=%#lx\n",
+                     va & PAGE_MASK, mfn_x(gmfn));
         goto emulate_readonly; /* skip over the instruction */
+    }
 
     /* In HVM guests, we force CR0.WP always to be set, so that the
      * pagetables are always write-protected.  If the guest thinks