Add 'Android.mk' file, fix compile on Android.

This requires disabling LDPRELOAD and temporarily disabling
capabilities support.

Reland of https://android-review.googlesource.com/#/c/159755/
with compile fixes. Compile-tested on
aosp_{x86,x86_64,arm,arm64,mips64}-eng.

Bug: 22487289
Change-Id: Ia4530cf09b074aa0a2afe5a5b307ff3c5c5d6c08

1 files changed, 73 insertions, 0 deletions

diff --git a/signal_handler.c b/signal_handler.c
new file mode 100644
index 0000000..dd0ea4f
--- /dev/null
+++ b/signal_handler.c
@@ -0,0 +1,73 @@
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* These header files need to be included before asm/siginfo.h such that
+ * pid_t, timer_t, and clock_t are defined. */
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <asm/siginfo.h>
+#define __have_siginfo_t 1
+#define __have_sigval_t 1
+#define __have_sigevent_t 1
+
+#include <signal.h>
+#include <string.h>
+
+#include "signal_handler.h"
+
+#include "util.h"
+
+struct local_sigsys {
+	void		*ip;
+	int		nr;
+	unsigned int	arch;
+};
+
+void log_sigsys_handler(int nr, siginfo_t *info, void *void_context)
+{
+	struct local_sigsys sigsys;
+	const char *syscall_name;
+	memcpy(&sigsys, &info->_sifields, sizeof(sigsys));
+	syscall_name = lookup_syscall_name(sigsys.nr);
+
+	if (syscall_name)
+		warn("blocked syscall: %s", syscall_name);
+	else
+		warn("blocked syscall: %d", nr);
+
+	(void) void_context;
+
+	/*
+	 * We trapped on a syscall that should have killed the process.
+	 * This should never ever return, but we're paranoid.
+	 */
+	for (;;)
+		_exit(1);
+}
+
+int install_sigsys_handler()
+{
+	int ret = 0;
+	struct sigaction act;
+	sigset_t mask;
+
+	memset(&act, 0, sizeof(act));
+	act.sa_sigaction = &log_sigsys_handler;
+	act.sa_flags = SA_SIGINFO;
+
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGSYS);
+
+	ret = sigaction(SIGSYS, &act, NULL);
+	if (ret < 0)
+		return ret;
+
+	ret = sigprocmask(SIG_UNBLOCK, &mask, NULL);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}