[PATCH 2/6] xen/arm: Introduce flags_has_rwx helper

[Hari Limaye <hari.limaye@xxxxxxx>]

From: Luca Fancellu <luca.fancellu@xxxxxxx>

Introduce flags_has_rwx() function that will check if a
mapping is both writable and executable when modifying
or update the mapping.

This check was already present in pt.c but since it will
be used also for MPU system, it's wrapped into a function
now.

Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
---
 xen/arch/arm/include/asm/mm.h |  2 ++
 xen/arch/arm/mm.c             | 15 +++++++++++++++
 xen/arch/arm/mmu/pt.c         |  9 +--------
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h
index 011bc1fd30..9daaa96d93 100644
--- a/xen/arch/arm/include/asm/mm.h
+++ b/xen/arch/arm/include/asm/mm.h
@@ -192,6 +192,8 @@ extern unsigned long frametable_base_pdx;
 
 /* Boot-time pagetable setup */
 extern void setup_pagetables(void);
+/* Check that the mapping flag has no W and X together */
+extern bool flags_has_rwx(unsigned int flags);
 /* Map FDT in boot pagetable */
 extern void *early_fdt_map(paddr_t fdt_paddr);
 /* Remove early mappings */
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 0613c19169..c2da1e3a05 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -24,6 +24,21 @@
 
 unsigned long frametable_base_pdx __read_mostly;
 
+bool flags_has_rwx(unsigned int flags)
+{
+    /*
+     * The hardware was configured to forbid mapping both writeable and
+     * executable.
+     * When modifying/creating mapping (i.e _PAGE_PRESENT is set),
+     * prevent any update if this happen.
+     */
+    if ( (flags & _PAGE_PRESENT) && !PAGE_RO_MASK(flags) &&
+         !PAGE_XN_MASK(flags) )
+        return true;
+    else
+        return false;
+}
+
 void flush_page_to_ram(unsigned long mfn, bool sync_icache)
 {
     void *v = map_domain_page(_mfn(mfn));
diff --git a/xen/arch/arm/mmu/pt.c b/xen/arch/arm/mmu/pt.c
index 4726e713ef..621b47dbf5 100644
--- a/xen/arch/arm/mmu/pt.c
+++ b/xen/arch/arm/mmu/pt.c
@@ -610,14 +610,7 @@ static int xen_pt_update(unsigned long virt,
      */
     const mfn_t root = maddr_to_mfn(READ_SYSREG64(TTBR0_EL2));
 
-    /*
-     * The hardware was configured to forbid mapping both writeable and
-     * executable.
-     * When modifying/creating mapping (i.e _PAGE_PRESENT is set),
-     * prevent any update if this happen.
-     */
-    if ( (flags & _PAGE_PRESENT) && !PAGE_RO_MASK(flags) &&
-         !PAGE_XN_MASK(flags) )
+    if ( flags_has_rwx(flags) )
     {
         mm_printk("Mappings should not be both Writeable and Executable.\n");
         return -EINVAL;
-- 
2.34.1