i#6919: Fix XMM saving after synchall

core/unix/os.c

@@ -3792,7 +3792,8 @@ os_thread_sleep(uint64 milliseconds)
          * routine sleep forever
          */
         if (count++ > 3 && !IS_CLIENT_THREAD(get_thread_private_dcontext())) {
-            ASSERT_NOT_REACHED();
+            ASSERT_CURIOSITY_ONCE(
+                false && "os_thread_sleep interrupted by signal more than 3 times.");
             break; /* paranoid */
         }
         req = remain;

core/unix/signal.c

@@ -3235,20 +3235,19 @@ thread_set_self_context(void *cxt, bool is_detach_external)
     ASSERT_NOT_IMPLEMENTED(false); /* PR 405694: can't use regular sigreturn! */
 #endif
     memset(&frame, 0, sizeof(frame));
-#if defined(X86)
-    dcontext_t *dcontext = get_thread_private_dcontext();
-#endif
 #ifdef LINUX
+    frame.uc.uc_mcontext = *sc;
 #    ifdef X86
-    byte *xstate = get_and_initialize_xstate_buffer(dcontext);
-    frame.uc.uc_mcontext.fpstate = &((kernel_xstate_t *)xstate)->fpstate;
+    dcontext_t *dcontext = get_thread_private_dcontext();
+    frame.uc.uc_mcontext.fpstate = (kernel_fpstate_t *)get_and_initialize_xstate_buffer(
+        get_thread_private_dcontext());
 #    endif /* X86 */
-    frame.uc.uc_mcontext = *sc;
-#endif
-    IF_ARM(ASSERT_NOT_TESTED());
+#endif     /* LINUX */
 #if defined(X86)
+    /* This saves both X87 state (from fxsave) and XMM state (from mcontext) */
     save_fpstate(dcontext, &frame);
 #endif
+    IF_ARM(ASSERT_NOT_TESTED());
     /* The kernel calls do_sigaltstack on sys_rt_sigreturn primarily to ensure
      * the frame is ok, but the side effect is we can mess up our own altstack
      * settings if we're not careful.  Having invalid ss_size looks good for
@@ -3341,14 +3340,16 @@ thread_set_self_mcontext(priv_mcontext_t *mc, bool is_detach_external)
     sig_full_cxt_t sc_full;
     sig_full_initialize(&sc_full, &ucxt);
 #if defined(LINUX) && defined(X86)
-    sc_full.sc->fpstate = NULL; /* for mcontext_to_sigcontext */
+    /* This prevents mcontext_to_sigcontext from filling in fpstate.
+     * Instead, it initialized by thread_set_self_context.
+     */
+    sc_full.sc->fpstate = NULL;
 #endif
     mcontext_to_sigcontext(&sc_full, mc, DR_MC_ALL);
     thread_set_segment_registers(sc_full.sc);
     /* sigreturn takes the mode from cpsr */
     IF_ARM(
         set_pc_mode_in_cpsr(sc_full.sc, dr_get_isa_mode(get_thread_private_dcontext())));
-    /* thread_set_self_context will fill in the real fp/simd state for x86 */
     thread_set_self_context((void *)sc_full.sc, is_detach_external);
     ASSERT_NOT_REACHED();
 }

suite/tests/CMakeLists.txt

@@ -5401,6 +5401,13 @@ if (UNIX)
   if (NOT APPLE)
     tobuild(linux.thread linux/thread.c)
     tobuild(linux.threadexit linux/threadexit.c)
+
+    if (X86 AND X64 AND DR_HOST_X86 AND DR_HOST_X64)
+      tobuild_ci(linux.synchall-restore linux/synchall-restore.c "" "" "")
+      set_avx_flags(linux.synchall-restore)
+      link_with_pthread(linux.synchall-restore)
+    endif ()
+
     if (NOT ANDROID)
       tobuild(linux.threadexit2 linux/threadexit2.c) # XXX i#1874: hangs on Android
       tobuild(linux.signalfd linux/signalfd.c) # XXX i#1874: fails natively on Android