[Xen-devel] [PATCH v3 14/17] livepatch/x86/arm: arch/x86/mm: generalize do_page_walk() and implement arch_livepatch_lookup_mfn

[Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>]

With this change we can use _do_page_walk() to implement
arch_livepatch_lookup_mfn() which can be used to find out
vmap virtual addresses (as under x86 virt_to_mfn won't work
for vmap, but it does for arm!).

Signed-off-by: Blaise Boscaccy <blaise.boscaccy@xxxxxxxxxx>
Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 xen/arch/arm/livepatch.c    |  7 ++++---
 xen/arch/x86/livepatch.c    | 10 ++++++++++
 xen/arch/x86/x86_64/mm.c    | 33 ++++++++++++++++++++++++---------
 xen/include/asm-x86/mm.h    |  1 +
 xen/include/xen/livepatch.h |  3 +++
 5 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/xen/arch/arm/livepatch.c b/xen/arch/arm/livepatch.c
index e1d5d58f97..1771b3c558 100644
--- a/xen/arch/arm/livepatch.c
+++ b/xen/arch/arm/livepatch.c
@@ -13,9 +13,10 @@
 #include <asm/livepatch.h>
 #include <asm/mm.h>
 
-/* Override macros from asm/page.h to make them work with mfn_t */
-#undef virt_to_mfn
-#define virt_to_mfn(va) _mfn(__virt_to_mfn(va))
+mfn_t arch_livepatch_lookup_mfn(unsigned long addr)
+{
+    return _mfn(__virt_to_mfn(addr));
+}
 
 void arch_livepatch_revive(void)
 {
diff --git a/xen/arch/x86/livepatch.c b/xen/arch/x86/livepatch.c
index 12287d445f..667573c6de 100644
--- a/xen/arch/x86/livepatch.c
+++ b/xen/arch/x86/livepatch.c
@@ -14,6 +14,16 @@
 #include <asm/nmi.h>
 #include <asm/livepatch.h>
 
+mfn_t arch_livepatch_lookup_mfn(unsigned long addr)
+{
+    unsigned long cr3 = read_cr3() >> PAGE_SHIFT;
+
+    if ( !mfn_valid(_mfn(cr3)) )
+        return INVALID_MFN;
+
+    return _do_page_walk(cr3, addr);
+}
+
 void arch_livepatch_revive(void)
 {
     /* Nothing to do. */
diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 11746730b4..f8a963bbba 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -44,29 +44,28 @@ unsigned int __read_mostly m2p_compat_vstart = 
__HYPERVISOR_COMPAT_VIRT_START;
 
 l2_pgentry_t *compat_idle_pg_table_l2;
 
-void *do_page_walk(struct vcpu *v, unsigned long addr)
+mfn_t _do_page_walk(unsigned long mfn, unsigned long addr)
 {
-    unsigned long mfn = pagetable_get_pfn(v->arch.guest_table);
     l4_pgentry_t l4e, *l4t;
     l3_pgentry_t l3e, *l3t;
     l2_pgentry_t l2e, *l2t;
     l1_pgentry_t l1e, *l1t;
 
-    if ( !is_pv_vcpu(v) || !is_canonical_address(addr) )
-        return NULL;
+    if ( !is_canonical_address(addr) )
+        return INVALID_MFN;
 
     l4t = map_domain_page(_mfn(mfn));
     l4e = l4t[l4_table_offset(addr)];
     unmap_domain_page(l4t);
     if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
-        return NULL;
+        return INVALID_MFN;
 
     l3t = map_l3t_from_l4e(l4e);
     l3e = l3t[l3_table_offset(addr)];
     unmap_domain_page(l3t);
     mfn = l3e_get_pfn(l3e);
     if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) || !mfn_valid(_mfn(mfn)) )
-        return NULL;
+        return INVALID_MFN;
     if ( (l3e_get_flags(l3e) & _PAGE_PSE) )
     {
         mfn += PFN_DOWN(addr & ((1UL << L3_PAGETABLE_SHIFT) - 1));
@@ -78,7 +77,7 @@ void *do_page_walk(struct vcpu *v, unsigned long addr)
     unmap_domain_page(l2t);
     mfn = l2e_get_pfn(l2e);
     if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) || !mfn_valid(_mfn(mfn)) )
-        return NULL;
+        return INVALID_MFN;
     if ( (l2e_get_flags(l2e) & _PAGE_PSE) )
     {
         mfn += PFN_DOWN(addr & ((1UL << L2_PAGETABLE_SHIFT) - 1));
@@ -90,10 +89,26 @@ void *do_page_walk(struct vcpu *v, unsigned long addr)
     unmap_domain_page(l1t);
     mfn = l1e_get_pfn(l1e);
     if ( !(l1e_get_flags(l1e) & _PAGE_PRESENT) || !mfn_valid(_mfn(mfn)) )
-        return NULL;
+        return INVALID_MFN;
 
  ret:
-    return map_domain_page(_mfn(mfn)) + (addr & ~PAGE_MASK);
+    return _mfn(mfn);
+}
+
+void *do_page_walk(struct vcpu *v, unsigned long addr)
+{
+    mfn_t mfn;
+    unsigned long cr3;
+
+    if ( !is_pv_vcpu(v) )
+        return NULL;
+
+    cr3 = pagetable_get_pfn(v->arch.guest_table);
+    mfn = _do_page_walk(cr3, addr);
+    if ( mfn_eq(mfn, INVALID_MFN) )
+        return NULL;
+
+    return map_domain_page(mfn) + (addr & ~PAGE_MASK);
 }
 
 /*
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index bef45e8e9f..224a94494a 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -540,6 +540,7 @@ int new_guest_cr3(mfn_t mfn);
 void make_cr3(struct vcpu *v, mfn_t mfn);
 void update_cr3(struct vcpu *v);
 int vcpu_destroy_pagetables(struct vcpu *);
+mfn_t _do_page_walk(unsigned long mfn, unsigned long addr);
 void *do_page_walk(struct vcpu *v, unsigned long addr);
 
 int __sync_local_execstate(void);
diff --git a/xen/include/xen/livepatch.h b/xen/include/xen/livepatch.h
index 065c1a323a..e529f0e7c3 100644
--- a/xen/include/xen/livepatch.h
+++ b/xen/include/xen/livepatch.h
@@ -72,6 +72,9 @@ int arch_livepatch_secure(const void *va, unsigned int pages, 
enum va_type types
 
 void arch_livepatch_init(void);
 
+#include <xen/mm.h> /* For mfn_t decleration. */
+mfn_t arch_livepatch_lookup_mfn(unsigned long addr);
+
 #include <public/sysctl.h> /* For struct livepatch_func. */
 #include <asm/livepatch.h>
 int arch_livepatch_verify_func(const struct livepatch_func *func);
-- 
2.13.3


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