[RFC PATCH 4/4] xen/arm: initialize conditionally uninitialized local variables

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

The function 'guest_walk_tables' contains an initialization
pattern for the pointee of parameter 'perms' that is not easy
for automatic checkers to reason about.

A modified pattern that does not alter the semantics of the
code is introduced.

A const qualifier is added in 'xen/arch/arm/dm.c' because
'copy_to_guest_offset' doesn't modify that parameter.

Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
---
 xen/arch/arm/dm.c         |  2 +-
 xen/arch/arm/guest_walk.c | 12 +++++++-----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/dm.c b/xen/arch/arm/dm.c
index 5569efa121..910788e098 100644
--- a/xen/arch/arm/dm.c
+++ b/xen/arch/arm/dm.c
@@ -129,7 +129,7 @@ int dm_op(const struct dmop_args *op_args)
 
     if ( (!rc || rc == -ERESTART) &&
          !const_op && copy_to_guest_offset(op_args->buf[0].h, offset,
-                                           (void *)&op.u, op_size[op.op]) )
+                                           (const void *)&op.u, 
op_size[op.op]) )
         rc = -EFAULT;
 
  out:
diff --git a/xen/arch/arm/guest_walk.c b/xen/arch/arm/guest_walk.c
index d99b411f3b..6c017242f2 100644
--- a/xen/arch/arm/guest_walk.c
+++ b/xen/arch/arm/guest_walk.c
@@ -552,15 +552,12 @@ bool guest_walk_tables(const struct vcpu *v, vaddr_t gva,
 {
     register_t sctlr = READ_SYSREG(SCTLR_EL1);
     register_t tcr = READ_SYSREG(TCR_EL1);
-    unsigned int _perms;
+    unsigned int _perms = GV2M_READ;
 
     /* We assume that the domain is running on the currently active domain. */
     if ( v != current )
         return false;
 
-    /* Allow perms to be NULL. */
-    perms = perms ?: &_perms;
-
     /*
      * Currently, we assume a GVA to IPA translation with EL1 privileges.
      * Since, valid mappings in the first stage address translation table are
@@ -570,7 +567,12 @@ bool guest_walk_tables(const struct vcpu *v, vaddr_t gva,
      * attributes that distinguish between EL0 and EL1 permissions (EL0 might
      * not have permissions on the particular mapping).
      */
-    *perms = GV2M_READ;
+    /* Allow perms to be NULL. */
+    if( perms ) {
+      *perms = _perms;
+    } else {
+      perms = &_perms;
+    }
 
     /* If the MMU is disabled, there is no need to translate the gva. */
     if ( !(sctlr & SCTLR_Axx_ELx_M) )
-- 
2.34.1