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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen-unstable] x86: Do not allow write access to p2m_ram_ro memory type.
# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1215699596 -3600
# Node ID 8803b305b06c4bc03fa8b8270f3a83844bd446be
# Parent 26714991f24270e07fcec70ddc785f5fe8fe1777
x86: Do not allow write access to p2m_ram_ro memory type.
Log and discard such access attempts.
Signed-off-by: Trolle Selander <trolle.selander@xxxxxxxxxxxxx>
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
xen/arch/x86/hvm/hvm.c | 15 +++++++++-
xen/arch/x86/mm/shadow/multi.c | 58 ++++++++++++++++++++++++-----------------
2 files changed, 48 insertions(+), 25 deletions(-)
diff -r 26714991f242 -r 8803b305b06c xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c Thu Jul 10 14:20:15 2008 +0100
+++ b/xen/arch/x86/hvm/hvm.c Thu Jul 10 15:19:56 2008 +0100
@@ -1496,8 +1496,19 @@ static enum hvm_copy_result __hvm_copy(
if ( flags & HVMCOPY_to_guest )
{
- memcpy(p, buf, count);
- paging_mark_dirty(curr->domain, mfn);
+ 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);
+ }
}
else
{
diff -r 26714991f242 -r 8803b305b06c xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c Thu Jul 10 14:20:15 2008 +0100
+++ b/xen/arch/x86/mm/shadow/multi.c Thu Jul 10 15:19:56 2008 +0100
@@ -3344,13 +3344,22 @@ static int sh_page_fault(struct vcpu *v,
}
}
- /* Need to hand off device-model MMIO and writes to read-only
- * memory to the device model */
- if ( p2mt == p2m_mmio_dm
- || (p2mt == p2m_ram_ro && ft == ft_demand_write) )
+ /* Need to hand off device-model MMIO to the device model */
+ if ( p2mt == p2m_mmio_dm )
{
gpa = guest_walk_to_gpa(&gw);
goto mmio;
+ }
+
+ /* Log attempts to write to read-only memory */
+ if ( (p2mt == p2m_ram_ro) && (ft == ft_demand_write) )
+ {
+ static unsigned long lastpage = 0;
+ 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; /* skip over the instruction */
}
/* In HVM guests, we force CR0.WP always to be set, so that the
@@ -4587,6 +4596,7 @@ int sh_remove_l3_shadow(struct vcpu *v,
/* Translate a VA to an MFN, injecting a page-fault if we fail */
#define BAD_GVA_TO_GFN (~0UL)
#define BAD_GFN_TO_MFN (~1UL)
+#define READONLY_GFN (~2UL)
static mfn_t emulate_gva_to_mfn(struct vcpu *v,
unsigned long vaddr,
struct sh_emulate_ctxt *sh_ctxt)
@@ -4609,21 +4619,22 @@ static mfn_t emulate_gva_to_mfn(struct v
/* Translate the GFN to an MFN */
mfn = gfn_to_mfn(v->domain, _gfn(gfn), &p2mt);
- if ( p2m_is_ram(p2mt) )
- {
- ASSERT(mfn_valid(mfn));
- v->arch.paging.last_write_was_pt = !!sh_mfn_is_a_page_table(mfn);
- return mfn;
- }
-
- return _mfn(BAD_GFN_TO_MFN);
+ if ( p2mt == p2m_ram_ro )
+ return _mfn(READONLY_GFN);
+ if ( !p2m_is_ram(p2mt) )
+ return _mfn(BAD_GFN_TO_MFN);
+
+ ASSERT(mfn_valid(mfn));
+ v->arch.paging.last_write_was_pt = !!sh_mfn_is_a_page_table(mfn);
+ return mfn;
}
/* Check that the user is allowed to perform this write.
* Returns a mapped pointer to write to, or NULL for error. */
-#define MAPPING_UNHANDLEABLE ((void *)0)
-#define MAPPING_EXCEPTION ((void *)1)
-#define emulate_map_dest_failed(rc) ((unsigned long)(rc) <= 1)
+#define MAPPING_UNHANDLEABLE ((void *)(unsigned long)X86EMUL_UNHANDLEABLE)
+#define MAPPING_EXCEPTION ((void *)(unsigned long)X86EMUL_EXCEPTION)
+#define MAPPING_SILENT_FAIL ((void *)(unsigned long)X86EMUL_OKAY)
+#define emulate_map_dest_failed(rc) ((unsigned long)(rc) <= 3)
static void *emulate_map_dest(struct vcpu *v,
unsigned long vaddr,
u32 bytes,
@@ -4641,7 +4652,9 @@ static void *emulate_map_dest(struct vcp
sh_ctxt->mfn1 = emulate_gva_to_mfn(v, vaddr, sh_ctxt);
if ( !mfn_valid(sh_ctxt->mfn1) )
return ((mfn_x(sh_ctxt->mfn1) == BAD_GVA_TO_GFN) ?
- MAPPING_EXCEPTION : MAPPING_UNHANDLEABLE);
+ MAPPING_EXCEPTION :
+ (mfn_x(sh_ctxt->mfn1) == READONLY_GFN) ?
+ MAPPING_SILENT_FAIL : MAPPING_UNHANDLEABLE);
/* Unaligned writes mean probably this isn't a pagetable */
if ( vaddr & (bytes - 1) )
@@ -4665,7 +4678,9 @@ static void *emulate_map_dest(struct vcp
sh_ctxt);
if ( !mfn_valid(sh_ctxt->mfn2) )
return ((mfn_x(sh_ctxt->mfn2) == BAD_GVA_TO_GFN) ?
- MAPPING_EXCEPTION : MAPPING_UNHANDLEABLE);
+ MAPPING_EXCEPTION :
+ (mfn_x(sh_ctxt->mfn2) == READONLY_GFN) ?
+ MAPPING_SILENT_FAIL : MAPPING_UNHANDLEABLE);
/* Cross-page writes mean probably not a pagetable */
sh_remove_shadows(v, sh_ctxt->mfn2, 0, 0 /* Slow, can fail */ );
@@ -4782,8 +4797,7 @@ sh_x86_emulate_write(struct vcpu *v, uns
addr = emulate_map_dest(v, vaddr, bytes, sh_ctxt);
if ( emulate_map_dest_failed(addr) )
- return ((addr == MAPPING_EXCEPTION) ?
- X86EMUL_EXCEPTION : X86EMUL_UNHANDLEABLE);
+ return (long)addr;
shadow_lock(v->domain);
memcpy(addr, src, bytes);
@@ -4809,8 +4823,7 @@ sh_x86_emulate_cmpxchg(struct vcpu *v, u
addr = emulate_map_dest(v, vaddr, bytes, sh_ctxt);
if ( emulate_map_dest_failed(addr) )
- return ((addr == MAPPING_EXCEPTION) ?
- X86EMUL_EXCEPTION : X86EMUL_UNHANDLEABLE);
+ return (long)addr;
shadow_lock(v->domain);
switch ( bytes )
@@ -4854,8 +4867,7 @@ sh_x86_emulate_cmpxchg8b(struct vcpu *v,
addr = emulate_map_dest(v, vaddr, 8, sh_ctxt);
if ( emulate_map_dest_failed(addr) )
- return ((addr == MAPPING_EXCEPTION) ?
- X86EMUL_EXCEPTION : X86EMUL_UNHANDLEABLE);
+ return (long)addr;
old = (((u64) old_hi) << 32) | (u64) old_lo;
new = (((u64) new_hi) << 32) | (u64) new_lo;
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