libdebuggerd_handler: in-process crash dumping for seccomped processes.

Do an in-process unwind for processes that have PR_SET_NO_NEW_PRIVS
enabled.

Bug: http://b/34684590
Test: debuggerd_test, killall -ABRT media.codec
Change-Id: I62562ec2c419d6643970100ab1cc0288982a1eed

1 files changed, 48 insertions, 0 deletions

diff --git a/debuggerd/handler/debuggerd_fallback.cpp b/debuggerd/handler/debuggerd_fallback.cpp
new file mode 100644
index 000000000..77ad6ac1e
--- /dev/null
+++ b/debuggerd/handler/debuggerd_fallback.cpp
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2017 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 <stddef.h>
+#include <sys/ucontext.h>
+#include <unistd.h>
+
+#include "tombstone.h"
+
+extern "C" void __linker_use_fallback_allocator();
+
+extern "C" bool debuggerd_fallback(ucontext_t* ucontext, siginfo_t* siginfo, void* abort_message) {
+  // This is incredibly sketchy to do inside of a signal handler, especially when libbacktrace
+  // uses the C++ standard library throughout, but this code runs in the linker, so we'll be using
+  // the linker's malloc instead of the libc one. Switch it out for a replacement, just in case.
+  //
+  // This isn't the default method of dumping because it can fail in cases such as memory space
+  // exhaustion.
+  __linker_use_fallback_allocator();
+  engrave_tombstone_ucontext(-1, getpid(), gettid(), reinterpret_cast<uintptr_t>(abort_message),
+                             siginfo, ucontext);
+  return true;
+}