i#4197: Add new drwrap post-call scheme: replace retaddr

api/docs/release.dox

@@ -255,6 +255,9 @@ Further non-compatibility-affecting changes include:
  - Added drwrap_get_stats().
  - Added #DRWRAP_NO_DYNAMIC_RETADDRS for reducing drwrap overhead at the cost
    of missing some post-call callbacks.
+ - Added #DRWRAP_REPLACE_RETADDR for an alternative method of setting up post-call
+   control points by replacing return addresses.  This does not work for every
+   application, but reduces overhead.
  - Added -record_dynsym_only to drcachesim for faster function tracing symbol
    lookups when internal symbols are not needed.
  - Added dr_merge_arith_flags() as a convenience routine to merge arithmetic flags

core/synch.c

@@ -447,6 +447,27 @@ translate_mcontext(thread_record_t *trec, priv_mcontext_t *mcontext, bool restor
                 dump_mcontext(get_mcontext(trec->dcontext), THREAD_GET, DUMP_NOT_XML);
             });
             *mcontext = *get_mcontext(trec->dcontext);
+#ifdef CLIENT_INTERFACE
+            if (dr_xl8_hook_exists()) {
+                /* The client may need to translate here if it's using sentinel
+                 * addresses outside of the code cache as targets.
+                 */
+                dr_restore_state_info_t client_info;
+                dr_mcontext_t client_mcontext;
+                dr_mcontext_init(&client_mcontext);
+                priv_mcontext_to_dr_mcontext(&client_mcontext, mcontext);
+                client_info.raw_mcontext = &client_mcontext;
+                client_info.raw_mcontext_valid = true;
+                client_info.mcontext = &client_mcontext;
+                client_info.fragment_info.tag = NULL;
+                client_info.fragment_info.cache_start_pc = NULL;
+                client_info.fragment_info.is_trace = false;
+                client_info.fragment_info.app_code_consistent = true;
+                if (!instrument_restore_state(trec->dcontext, true, &client_info))
+                    return false;
+                dr_mcontext_to_priv_mcontext(mcontext, &client_mcontext);
+            }
+#endif
             return true;
         }
     }
@@ -2165,6 +2186,14 @@ detach_on_permanent_stack(bool internal, bool do_cleanup, dr_stats_t *drstats)
              * app that assumes no signals and assumes its non-auto-restart syscalls
              * don't need loops could be broken.
              */
+            LOG(GLOBAL, LOG_ALL, 3,
+                /* Having the code bytes can help diagnose post-detach where the code
+                 * cache is gone.
+                 */
+                "Detach: pre-xl8 pc=%p (%02x %02x %02x %02x %02x), xsp=%p "
+                "for thread " TIDFMT "\n",
+                mc.pc, *mc.pc, *(mc.pc + 1), *(mc.pc + 2), *(mc.pc + 3), *(mc.pc + 4),
+                mc.xsp, threads[i]->id);
             DEBUG_DECLARE(ok =)
             translate_mcontext(threads[i], &mc, true /*restore mem*/, NULL /*f*/);
             ASSERT(ok);

core/translate.c

@@ -584,6 +584,7 @@ translate_restore_clean_call(dcontext_t *tdcontext, translate_walk_t *walk)
     /* PR 302951: we recognize a clean call by its combination of
      * our-mangling and NULL translation.
      * We restore to the priv_mcontext_t that was pushed on the stack.
+     * FIXME i#4219: This is not safe: see comment below.
      */
     LOG(THREAD_GET, LOG_INTERP, 2, "\ttranslating clean call arg crash\n");
     dr_get_mcontext_priv(tdcontext, NULL, walk->mc);
@@ -733,7 +734,11 @@ recreate_app_state_from_info(dcontext_t *tdcontext, const translation_info_t *in
          * (should spend enough time at syscalls that will hit safe spot in
          * reasonable time).
          */
-        /* PR 302951: our clean calls do show up here and have full state */
+        /* PR 302951: our clean calls do show up here and have full state.
+         * FIXME i#4219: Actually we do *not* always have full state: for asynch
+         * xl8 we could be before setup or after teardown of the mcontext on the
+         * dstack, and with leaner clean calls we might not have the full mcontext.
+         */
         if (answer == NULL && ours)
             translate_restore_clean_call(tdcontext, &walk);
         else
@@ -888,7 +893,9 @@ recreate_app_state_from_ilist(dcontext_t *tdcontext, instrlist_t *ilist, byte *s
                  * in the middle of client meta code.
                  */
                 ASSERT(instr_is_meta(inst));
-                /* PR 302951: our clean calls do show up here and have full state */
+                /* PR 302951: our clean calls do show up here and have full state.
+                 * FIXME i#4219: This is not safe: see comment above.
+                 */
                 if (instr_is_our_mangling(inst))
                     translate_restore_clean_call(tdcontext, &walk);
                 else