Fix signal trampolines.

* LP32 should use sa_restorer too. gdb expects this, and future (>= 3.15) x86
  kernels will apparently stop supporting the case where SA_RESTORER isn't
  set.

* gdb and libunwind care about the exact instruction sequences, so we need to
  modify the code slightly in a few cases to match what they're looking for.

* gdb also cares about the exact function names (for some architectures),
  so we need to use __restore and __restore_rt rather than __sigreturn and
  __rt_sigreturn.

* It's possible that we don't have a VDSO; dl_iterate_phdr shouldn't assume
  that getauxval(AT_SYSINFO_EHDR) will return a non-null pointer.

This fixes unwinding through a signal handler in gdb for all architectures.
It doesn't fix libunwind for arm and arm64. I'll keep investigating that...

(cherry picked from commit 36f451a6d9)

Bug: 17436734
Change-Id: Ic1ea1184db6655c5d96180dc07bcc09628e647cb

libc/arch-arm/arm.mk

@@ -55,6 +55,8 @@ libc_bionic_src_files_arm += \
     arch-arm/bionic/_exit_with_stack_teardown.S \
     arch-arm/bionic/libgcc_compat.c \
     arch-arm/bionic/memcmp.S \
+    arch-arm/bionic/__restore_rt.S \
+    arch-arm/bionic/__restore.S \
     arch-arm/bionic/_setjmp.S \
     arch-arm/bionic/setjmp.S \
     arch-arm/bionic/sigsetjmp.S \

libc/arch-arm/bionic/__restore.S

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+// This function must have exactly this instruction sequence for gdb and libunwind.
+ENTRY_PRIVATE(__restore)
+  mov r7, #__NR_sigreturn
+  swi #0
+END(__restore)

libc/arch-arm/bionic/__restore_rt.S

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+// This function must have exactly this instruction sequence for gdb and libunwind.
+ENTRY_PRIVATE(__restore_rt)
+  mov r7, #__NR_rt_sigreturn
+  swi #0
+END(__restore_rt)

libc/arch-arm64/arm64.mk

@@ -29,7 +29,7 @@ libc_common_src_files_arm64 += \
 libc_bionic_src_files_arm64 := \
     arch-arm64/bionic/__bionic_clone.S \
     arch-arm64/bionic/_exit_with_stack_teardown.S \
-    arch-arm64/bionic/__rt_sigreturn.S \
+    arch-arm64/bionic/__restore_rt.S \
     arch-arm64/bionic/_setjmp.S \
     arch-arm64/bionic/setjmp.S \
     arch-arm64/bionic/__set_tls.c \

libc/arch-arm64/bionic/__restore_rt.S

@@ -28,7 +28,8 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY_PRIVATE(__rt_sigreturn)
+// This function must have exactly this instruction sequence for gdb and libunwind.
-  mov     x8, __NR_rt_sigreturn
+ENTRY_PRIVATE(__restore_rt)
-  svc     #0
+  mov x8, __NR_rt_sigreturn
-END(__rt_sigreturn)
+  svc #0
+END(__restore_rt)

libc/arch-x86/bionic/__restore.S

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+// This function must have exactly this instruction sequence for gdb and libunwind.
+// This function must have exactly this name for gdb.
+ENTRY(__restore)
+  popl %eax
+  movl $__NR_sigreturn, %eax
+  int $0x80
+END(__restore)

libc/arch-x86/bionic/__restore_rt.S

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+// This function must have exactly this instruction sequence for gdb and libunwind.
+// This function must have exactly this name for gdb.
+ENTRY(__restore_rt)
+  movl $__NR_rt_sigreturn, %eax
+  int $0x80
+END(__restore_rt)

libc/arch-x86/x86.mk

@@ -26,6 +26,8 @@ libc_bionic_src_files_x86 += \
     arch-x86/bionic/__bionic_clone.S \
     arch-x86/bionic/_exit_with_stack_teardown.S \
     arch-x86/bionic/libgcc_compat.c \
+    arch-x86/bionic/__restore_rt.S \
+    arch-x86/bionic/__restore.S \
     arch-x86/bionic/_setjmp.S \
     arch-x86/bionic/setjmp.S \
     arch-x86/bionic/__set_tls.c \

libc/arch-x86_64/bionic/__restore_rt.S

@@ -28,7 +28,9 @@
 
 #include <private/bionic_asm.h>
 
-ENTRY_PRIVATE(__rt_sigreturn)
+// This function must have exactly this instruction sequence for gdb and libunwind.
-  movl $__NR_rt_sigreturn, %eax
+// This function must have exactly this name for gdb.
+ENTRY(__restore_rt)
+  mov $__NR_rt_sigreturn, %rax
   syscall
-END(__rt_sigreturn)
+END(__restore_rt)

libc/arch-x86_64/x86_64.mk

@@ -30,7 +30,7 @@ libc_common_src_files_x86_64 += \
 libc_bionic_src_files_x86_64 := \
     arch-x86_64/bionic/__bionic_clone.S \
     arch-x86_64/bionic/_exit_with_stack_teardown.S \
-    arch-x86_64/bionic/__rt_sigreturn.S \
+    arch-x86_64/bionic/__restore_rt.S \
     arch-x86_64/bionic/_setjmp.S \
     arch-x86_64/bionic/setjmp.S \
     arch-x86_64/bionic/__set_tls.c \

libc/bionic/dl_iterate_phdr_static.cpp

@@ -62,6 +62,11 @@ int dl_iterate_phdr(int (*cb)(struct dl_phdr_info* info, size_t size, void* data
 
   // Try the VDSO if that didn't work.
   ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(getauxval(AT_SYSINFO_EHDR));
+  if (ehdr_vdso == nullptr) {
+    // There is no VDSO, so there's nowhere left to look.
+    return rc;
+  }
+
   struct dl_phdr_info vdso_info;
   vdso_info.dlpi_addr = 0;
   vdso_info.dlpi_name = NULL;

libc/bionic/sigaction.cpp

@@ -28,8 +28,10 @@
 
 #include <signal.h>
 
+extern "C" void __restore_rt(void);
+extern "C" void __restore(void);
+
 #if __LP64__
-extern "C" void __rt_sigreturn(void);
 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*);
@@ -47,7 +49,7 @@ int sigaction(int signal, const struct sigaction* bionic_new_action, struct siga
 
     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
   }
@@ -75,6 +77,20 @@ int sigaction(int signal, const struct sigaction* bionic_new_action, struct siga
 #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);
+  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;
+#ifdef 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
 }