[Xen-changelog] [xen-unstable] x86: Re-instate warnings for HVM guest writes to read-only memory.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1231420866 0
# Node ID 6cec460c3290ebe4f33916d7315d9cb61c8f2dd9
# Parent  7df072566b8c90914aa71bc5ef0d4f7ec33d70a7
x86: Re-instate warnings for HVM guest writes to read-only memory.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c         |   10 +++++++++-
 xen/arch/x86/mm/shadow/multi.c |    7 +++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff -r 7df072566b8c -r 6cec460c3290 xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c    Thu Jan 08 13:15:49 2009 +0000
+++ b/xen/arch/x86/hvm/hvm.c    Thu Jan 08 13:21:06 2009 +0000
@@ -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 -r 7df072566b8c -r 6cec460c3290 xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c    Thu Jan 08 13:15:49 2009 +0000
+++ b/xen/arch/x86/mm/shadow/multi.c    Thu Jan 08 13:21:06 2009 +0000
@@ -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

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