i#2144: better patch for single step with sandboxing

core/arch/mangle_shared.c

@@ -1016,11 +1016,15 @@ mangle(dcontext_t *dcontext, instrlist_t *ilist, uint *flags INOUT,
             mangle_possible_single_step(dcontext, ilist, instr);
             continue;
         }
-        else if (dcontext->single_step_addr != NULL &&
+        else if (dcontext->single_step_addr != NULL && instr_is_app(instr) &&
                  dcontext->single_step_addr == instr->translation) {
-            mangle_single_step(dcontext, ilist, *flags, instr);
-            /* Resets to generate single step exception only once. */
-            dcontext->single_step_addr = NULL;
+            instr_t * last_addr = instr_get_next_app(instr);
+            /* Checks if sandboxing added another app instruction. */
+            if (last_addr == NULL || last_addr->translation != instr->translation) {
+                mangle_single_step(dcontext, ilist, *flags, instr);
+                /* Resets to generate single step exception only once. */
+                dcontext->single_step_addr = NULL;
+            }
         }
 #endif
 #ifdef FOOL_CPUID

suite/tests/security-win32/singlestep.c

@@ -67,6 +67,7 @@ main(void)
     SetUnhandledExceptionFilter((LPTOP_LEVEL_EXCEPTION_FILTER) our_top_handler);
 
     print("start of test, count = %d\n", count);
+    protect_mem(foo, 1024, ALLOW_READ|ALLOW_WRITE|ALLOW_EXEC);
     count+=foo();
     print("end of test, count = %d\n", count);
 
@@ -78,12 +79,18 @@ main(void)
 START_FILE
 
 /* int foo()
- *   Generates a single step execution on jump and should return 1.
+ *   Generates a single step execution on jump and should return 2.
  */
 #define FUNCNAME foo
 DECLARE_FUNC(FUNCNAME)
 GLOBAL_LABEL(FUNCNAME:)
-        xor      eax, eax
+/* sets sandoxing mode in dynamorio by doing a self modification. */
+        mov      REG_XAX, HEX(1)
+        lea      REG_XDX, SYMREF(sandbox_immediate_addr_plus_four - 4)
+        mov      DWORD [REG_XDX], eax        /* selfmod write */
+        mov      REG_XDX, HEX(0)             /* mov_imm to modify */
+ADDRTAKEN_LABEL(sandbox_immediate_addr_plus_four:)
+        mov      REG_XAX, REG_XDX
 /* push flags on the stack */
         PUSHF
 /* setting the trap flag to 1 on top of the stack */

suite/tests/security-win32/singlestep.expect

@@ -1,3 +1,3 @@
 start of test, count = 0
 single step exception
-end of test, count = 2
+end of test, count = 3