1 files changed, 39 insertions, 17 deletions

diff --git a/libc/bionic/sigaction.cpp b/libc/bionic/sigaction.cpp
index 225a823..0633748 100644
--- a/libc/bionic/sigaction.cpp
+++ b/libc/bionic/sigaction.cpp
@@ -28,28 +28,33 @@
 
 #include <signal.h>
 
-#if __LP64__
-extern "C" void __rt_sigreturn(void);
+extern "C" void __restore_rt(void);
+extern "C" void __restore(void);
+
+#if defined(__LP64__)
+
 extern "C" int __rt_sigaction(int, const struct __kernel_sigaction*, struct __kernel_sigaction*, size_t);
-#else
-extern "C" int __sigaction(int, const struct sigaction*, struct sigaction*);
-#endif
 
 int sigaction(int signal, const struct sigaction* bionic_new_action, struct sigaction* bionic_old_action) {
-#if __LP64__
   __kernel_sigaction kernel_new_action;
   if (bionic_new_action != NULL) {
     kernel_new_action.sa_flags = bionic_new_action->sa_flags;
     kernel_new_action.sa_handler = bionic_new_action->sa_handler;
     kernel_new_action.sa_mask = bionic_new_action->sa_mask;
-#ifdef SA_RESTORER
+#if defined(SA_RESTORER)
     kernel_new_action.sa_restorer = bionic_new_action->sa_restorer;
-
+#if defined(__aarch64__)
+    // arm64 has sa_restorer, but unwinding works best if you just let the
+    // kernel supply the default restorer from [vdso]. gdb doesn't care, but
+    // libgcc needs the nop that the kernel includes before the actual code.
+    // (We could add that ourselves, but why bother?)
+#else
     if (!(kernel_new_action.sa_flags & SA_RESTORER)) {
       kernel_new_action.sa_flags |= SA_RESTORER;
-      kernel_new_action.sa_restorer = &__rt_sigreturn;
+      kernel_new_action.sa_restorer = &__restore_rt;
     }
 #endif
+#endif
   }
 
   __kernel_sigaction kernel_old_action;
@@ -62,19 +67,36 @@ int sigaction(int signal, const struct sigaction* bionic_new_action, struct siga
     bionic_old_action->sa_flags = kernel_old_action.sa_flags;
     bionic_old_action->sa_handler = kernel_old_action.sa_handler;
     bionic_old_action->sa_mask = kernel_old_action.sa_mask;
-#ifdef SA_RESTORER
+#if defined(SA_RESTORER)
     bionic_old_action->sa_restorer = kernel_old_action.sa_restorer;
-
-    if (bionic_old_action->sa_restorer == &__rt_sigreturn) {
-      bionic_old_action->sa_flags &= ~SA_RESTORER;
-    }
 #endif
   }
 
   return result;
+}
+
 #else
-  // The 32-bit ABI is broken. struct sigaction includes a too-small sigset_t.
-  // TODO: if we also had correct struct sigaction definitions available, we could copy in and out.
-  return __sigaction(signal, bionic_new_action, bionic_old_action);
+
+extern "C" int __sigaction(int, const struct sigaction*, struct sigaction*);
+
+int sigaction(int signal, const struct sigaction* bionic_new_action, struct sigaction* bionic_old_action) {
+  // The 32-bit ABI is broken. struct sigaction includes a too-small sigset_t,
+  // so we have to use sigaction(2) rather than rt_sigaction(2).
+  struct sigaction kernel_new_action;
+  if (bionic_new_action != NULL) {
+    kernel_new_action.sa_flags = bionic_new_action->sa_flags;
+    kernel_new_action.sa_handler = bionic_new_action->sa_handler;
+    kernel_new_action.sa_mask = bionic_new_action->sa_mask;
+#if defined(SA_RESTORER)
+    kernel_new_action.sa_restorer = bionic_new_action->sa_restorer;
+
+    if (!(kernel_new_action.sa_flags & SA_RESTORER)) {
+      kernel_new_action.sa_flags |= SA_RESTORER;
+      kernel_new_action.sa_restorer = (kernel_new_action.sa_flags & SA_SIGINFO) ? &__restore_rt : &__restore;
+    }
 #endif
+  }
+  return __sigaction(signal, (bionic_new_action != NULL) ? &kernel_new_action : NULL, bionic_old_action);
 }
+
+#endif