[PATCH v1 1/2] x86: x86_emulate: address violation of MISRA C Rule 13.2

[<victorm.lira@xxxxxxx>]

From: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>

Rule 13.2 states: "The value of an expression and its persistent
side effects shall be the same under all permitted evaluation orders".

The full expansion of macro "commit_far_branch" contains an assignment to
variable "rc", which is also assigned to the result of the GNU statement
expression which "commit_far_branch" expands to.

To avoid any dependence on the order of evaluation, the latter assignment
is moved inside the macro.

Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
Signed-off-by: Victor Lira <victorm.lira@xxxxxxx>
---
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>
Cc: Michal Orzel <michal.orzel@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Julien Grall <julien@xxxxxxx>
Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
Cc: Federico Serafini <federico.serafini@xxxxxxxxxxx>
Cc: Bertrand Marquis <bertrand.marquis@xxxxxxx>
---
 xen/arch/x86/x86_emulate/x86_emulate.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index 8e14ebb35b..7108fe7b30 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -337,7 +337,7 @@ do {                                                        
            \
     validate_far_branch(cs, newip);                                     \
     _regs.r(ip) = (newip);                                              \
     singlestep = _regs.eflags & X86_EFLAGS_TF;                          \
-    ops->write_segment(x86_seg_cs, cs, ctxt);                           \
+    rc = ops->write_segment(x86_seg_cs, cs, ctxt);                      \
 })

 int x86emul_get_fpu(
@@ -2382,7 +2382,7 @@ x86_emulate(
              (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes + src.val),
                               &src.val, op_bytes, ctxt, ops)) ||
              (rc = load_seg(x86_seg_cs, src.val, 1, &cs, ctxt, ops)) ||
-             (rc = commit_far_branch(&cs, dst.val)) )
+             commit_far_branch(&cs, dst.val) )
             goto done;
         break;

@@ -2438,7 +2438,7 @@ x86_emulate(
         _regs.eflags &= mask;
         _regs.eflags |= (eflags & ~mask) | X86_EFLAGS_MBS;
         if ( (rc = load_seg(x86_seg_cs, sel, 1, &cs, ctxt, ops)) ||
-             (rc = commit_far_branch(&cs, (uint32_t)eip)) )
+             commit_far_branch(&cs, (uint32_t)eip) )
             goto done;
         break;
     }
@@ -2557,7 +2557,7 @@ x86_emulate(
         ASSERT(!mode_64bit());
     far_jmp:
         if ( (rc = load_seg(x86_seg_cs, imm2, 0, &cs, ctxt, ops)) ||
-             (rc = commit_far_branch(&cs, imm1)) )
+             commit_far_branch(&cs, imm1) )
             goto done;
         break;

--
2.47.0