diff --git a/MAINTAINERS b/MAINTAINERS
index 474bcb6c0bac6976302641f1592e4d449451bd0b..610e014f80bc13422b110ef3bd48000cbe9b0790 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8773,6 +8773,7 @@ S:	Supported
 F:	kernel/seccomp.c
 F:	include/uapi/linux/seccomp.h
 F:	include/linux/seccomp.h
+F:	tools/testing/selftests/seccomp/*
 K:	\bsecure_computing
 K:	\bTIF_SECCOMP\b
 
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 56b11cdaa2e43005431a729dd612d6dc28063f25..7474b7d9f4be8be791712458bd2a0f4eab8467a3 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -13,6 +13,7 @@ TARGETS += mqueue
 TARGETS += net
 TARGETS += powerpc
 TARGETS += ptrace
+TARGETS += seccomp
 TARGETS += size
 TARGETS += sysctl
 TARGETS += timers
diff --git a/tools/testing/selftests/seccomp/.gitignore b/tools/testing/selftests/seccomp/.gitignore
new file mode 100644
index 0000000000000000000000000000000000000000..346d83ca8069ab2a9f5c4decf26d624d289be988
--- /dev/null
+++ b/tools/testing/selftests/seccomp/.gitignore
@@ -0,0 +1 @@
+seccomp_bpf
diff --git a/tools/testing/selftests/seccomp/Makefile b/tools/testing/selftests/seccomp/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..8401e87e34e17e8103a6d02925c57e486f017f38
--- /dev/null
+++ b/tools/testing/selftests/seccomp/Makefile
@@ -0,0 +1,10 @@
+TEST_PROGS := seccomp_bpf
+CFLAGS += -Wl,-no-as-needed -Wall
+LDFLAGS += -lpthread
+
+all: $(TEST_PROGS)
+
+include ../lib.mk
+
+clean:
+	$(RM) $(TEST_PROGS)
diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
new file mode 100644
index 0000000000000000000000000000000000000000..c5abe7fd7590e3958eef38fa3079669c246c8f9e
--- /dev/null
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -0,0 +1,2109 @@
+/*
+ * Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by the GPLv2 license.
+ *
+ * Test code for seccomp bpf.
+ */
+
+#include <asm/siginfo.h>
+#define __have_siginfo_t 1
+#define __have_sigval_t 1
+#define __have_sigevent_t 1
+
+#include <errno.h>
+#include <linux/filter.h>
+#include <sys/prctl.h>
+#include <sys/ptrace.h>
+#include <sys/user.h>
+#include <linux/prctl.h>
+#include <linux/ptrace.h>
+#include <linux/seccomp.h>
+#include <poll.h>
+#include <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <string.h>
+#include <linux/elf.h>
+#include <sys/uio.h>
+
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <sys/syscall.h>
+
+#include "test_harness.h"
+
+#ifndef PR_SET_PTRACER
+# define PR_SET_PTRACER 0x59616d61
+#endif
+
+#ifndef PR_SET_NO_NEW_PRIVS
+#define PR_SET_NO_NEW_PRIVS 38
+#define PR_GET_NO_NEW_PRIVS 39
+#endif
+
+#ifndef PR_SECCOMP_EXT
+#define PR_SECCOMP_EXT 43
+#endif
+
+#ifndef SECCOMP_EXT_ACT
+#define SECCOMP_EXT_ACT 1
+#endif
+
+#ifndef SECCOMP_EXT_ACT_TSYNC
+#define SECCOMP_EXT_ACT_TSYNC 1
+#endif
+
+#ifndef SECCOMP_MODE_STRICT
+#define SECCOMP_MODE_STRICT 1
+#endif
+
+#ifndef SECCOMP_MODE_FILTER
+#define SECCOMP_MODE_FILTER 2
+#endif
+
+#ifndef SECCOMP_RET_KILL
+#define SECCOMP_RET_KILL        0x00000000U /* kill the task immediately */
+#define SECCOMP_RET_TRAP        0x00030000U /* disallow and force a SIGSYS */
+#define SECCOMP_RET_ERRNO       0x00050000U /* returns an errno */
+#define SECCOMP_RET_TRACE       0x7ff00000U /* pass to a tracer or disallow */
+#define SECCOMP_RET_ALLOW       0x7fff0000U /* allow */
+
+/* Masks for the return value sections. */
+#define SECCOMP_RET_ACTION      0x7fff0000U
+#define SECCOMP_RET_DATA        0x0000ffffU
+
+struct seccomp_data {
+	int nr;
+	__u32 arch;
+	__u64 instruction_pointer;
+	__u64 args[6];
+};
+#endif
+
+#define syscall_arg(_n) (offsetof(struct seccomp_data, args[_n]))
+
+#define SIBLING_EXIT_UNKILLED	0xbadbeef
+#define SIBLING_EXIT_FAILURE	0xbadface
+#define SIBLING_EXIT_NEWPRIVS	0xbadfeed
+
+TEST(mode_strict_support)
+{
+	long ret;
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_STRICT, NULL, NULL, NULL);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support CONFIG_SECCOMP");
+	}
+	syscall(__NR_exit, 1);
+}
+
+TEST_SIGNAL(mode_strict_cannot_call_prctl, SIGKILL)
+{
+	long ret;
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_STRICT, NULL, NULL, NULL);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support CONFIG_SECCOMP");
+	}
+	syscall(__NR_prctl, PR_SET_SECCOMP, SECCOMP_MODE_FILTER,
+		NULL, NULL, NULL);
+	EXPECT_FALSE(true) {
+		TH_LOG("Unreachable!");
+	}
+}
+
+/* Note! This doesn't test no new privs behavior */
+TEST(no_new_privs_support)
+{
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	EXPECT_EQ(0, ret) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+}
+
+/* Tests kernel support by checking for a copy_from_user() fault on * NULL. */
+TEST(mode_filter_support)
+{
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, NULL, 0, 0);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, NULL, NULL, NULL);
+	EXPECT_EQ(-1, ret);
+	EXPECT_EQ(EFAULT, errno) {
+		TH_LOG("Kernel does not support CONFIG_SECCOMP_FILTER!");
+	}
+}
+
+TEST(mode_filter_without_nnp)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_GET_NO_NEW_PRIVS, 0, NULL, 0, 0);
+	ASSERT_LE(0, ret) {
+		TH_LOG("Expected 0 or unsupported for NO_NEW_PRIVS");
+	}
+	errno = 0;
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	/* Succeeds with CAP_SYS_ADMIN, fails without */
+	/* TODO(wad) check caps not euid */
+	if (geteuid()) {
+		EXPECT_EQ(-1, ret);
+		EXPECT_EQ(EACCES, errno);
+	} else {
+		EXPECT_EQ(0, ret);
+	}
+}
+
+#define MAX_INSNS_PER_PATH 32768
+
+TEST(filter_size_limits)
+{
+	int i;
+	int count = BPF_MAXINSNS + 1;
+	struct sock_filter allow[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_filter *filter;
+	struct sock_fprog prog = { };
+	long ret;
+
+	filter = calloc(count, sizeof(*filter));
+	ASSERT_NE(NULL, filter);
+
+	for (i = 0; i < count; i++)
+		filter[i] = allow[0];
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	prog.filter = filter;
+	prog.len = count;
+
+	/* Too many filter instructions in a single filter. */
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	ASSERT_NE(0, ret) {
+		TH_LOG("Installing %d insn filter was allowed", prog.len);
+	}
+
+	/* One less is okay, though. */
+	prog.len -= 1;
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Installing %d insn filter wasn't allowed", prog.len);
+	}
+}
+
+TEST(filter_chain_limits)
+{
+	int i;
+	int count = BPF_MAXINSNS;
+	struct sock_filter allow[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_filter *filter;
+	struct sock_fprog prog = { };
+	long ret;
+
+	filter = calloc(count, sizeof(*filter));
+	ASSERT_NE(NULL, filter);
+
+	for (i = 0; i < count; i++)
+		filter[i] = allow[0];
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	prog.filter = filter;
+	prog.len = 1;
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	prog.len = count;
+
+	/* Too many total filter instructions. */
+	for (i = 0; i < MAX_INSNS_PER_PATH; i++) {
+		ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+		if (ret != 0)
+			break;
+	}
+	ASSERT_NE(0, ret) {
+		TH_LOG("Allowed %d %d-insn filters (total with penalties:%d)",
+		       i, count, i * (count + 4));
+	}
+}
+
+TEST(mode_filter_cannot_move_to_strict)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_STRICT, NULL, 0, 0);
+	EXPECT_EQ(-1, ret);
+	EXPECT_EQ(EINVAL, errno);
+}
+
+
+TEST(mode_filter_get_seccomp)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_GET_SECCOMP, 0, 0, 0, 0);
+	EXPECT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_GET_SECCOMP, 0, 0, 0, 0);
+	EXPECT_EQ(2, ret);
+}
+
+
+TEST(ALLOW_all)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+}
+
+TEST(empty_prog)
+{
+	struct sock_filter filter[] = {
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	EXPECT_EQ(-1, ret);
+	EXPECT_EQ(EINVAL, errno);
+}
+
+TEST_SIGNAL(unknown_ret_is_kill_inside, SIGSYS)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, 0x10000000U),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+	EXPECT_EQ(0, syscall(__NR_getpid)) {
+		TH_LOG("getpid() shouldn't ever return");
+	}
+}
+
+/* return code >= 0x80000000 is unused. */
+TEST_SIGNAL(unknown_ret_is_kill_above_allow, SIGSYS)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, 0x90000000U),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+	EXPECT_EQ(0, syscall(__NR_getpid)) {
+		TH_LOG("getpid() shouldn't ever return");
+	}
+}
+
+TEST_SIGNAL(KILL_all, SIGSYS)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+}
+
+TEST_SIGNAL(KILL_one, SIGSYS)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+	pid_t parent = getppid();
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* getpid() should never return. */
+	EXPECT_EQ(0, syscall(__NR_getpid));
+}
+
+TEST_SIGNAL(KILL_one_arg_one, SIGSYS)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+		/* Only both with lower 32-bit for now. */
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS, syscall_arg(0)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x0C0FFEE, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+	pid_t parent = getppid();
+	pid_t pid = getpid();
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	EXPECT_EQ(pid, syscall(__NR_getpid));
+	/* getpid() should never return. */
+	EXPECT_EQ(0, syscall(__NR_getpid, 0x0C0FFEE));
+}
+
+TEST_SIGNAL(KILL_one_arg_six, SIGSYS)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+		/* Only both with lower 32-bit for now. */
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS, syscall_arg(5)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x0C0FFEE, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+	pid_t parent = getppid();
+	pid_t pid = getpid();
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	EXPECT_EQ(pid, syscall(__NR_getpid));
+	/* getpid() should never return. */
+	EXPECT_EQ(0, syscall(__NR_getpid, 1, 2, 3, 4, 5, 0x0C0FFEE));
+}
+
+/* TODO(wad) add 64-bit versus 32-bit arg tests. */
+TEST(arg_out_of_range)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS, syscall_arg(6)),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	EXPECT_EQ(-1, ret);
+	EXPECT_EQ(EINVAL, errno);
+}
+
+TEST(ERRNO_valid)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | E2BIG),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+	pid_t parent = getppid();
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	EXPECT_EQ(-1, read(0, NULL, 0));
+	EXPECT_EQ(E2BIG, errno);
+}
+
+TEST(ERRNO_zero)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | 0),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+	pid_t parent = getppid();
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* "errno" of 0 is ok. */
+	EXPECT_EQ(0, read(0, NULL, 0));
+}
+
+TEST(ERRNO_capped)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | 4096),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+	pid_t parent = getppid();
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	EXPECT_EQ(-1, read(0, NULL, 0));
+	EXPECT_EQ(4095, errno);
+}
+
+FIXTURE_DATA(TRAP) {
+	struct sock_fprog prog;
+};
+
+FIXTURE_SETUP(TRAP)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRAP),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+
+	memset(&self->prog, 0, sizeof(self->prog));
+	self->prog.filter = malloc(sizeof(filter));
+	ASSERT_NE(NULL, self->prog.filter);
+	memcpy(self->prog.filter, filter, sizeof(filter));
+	self->prog.len = (unsigned short)ARRAY_SIZE(filter);
+}
+
+FIXTURE_TEARDOWN(TRAP)
+{
+	if (self->prog.filter)
+		free(self->prog.filter);
+}
+
+TEST_F_SIGNAL(TRAP, dfl, SIGSYS)
+{
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog);
+	ASSERT_EQ(0, ret);
+	syscall(__NR_getpid);
+}
+
+/* Ensure that SIGSYS overrides SIG_IGN */
+TEST_F_SIGNAL(TRAP, ign, SIGSYS)
+{
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	signal(SIGSYS, SIG_IGN);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog);
+	ASSERT_EQ(0, ret);
+	syscall(__NR_getpid);
+}
+
+static struct siginfo TRAP_info;
+static volatile int TRAP_nr;
+static void TRAP_action(int nr, siginfo_t *info, void *void_context)
+{
+	memcpy(&TRAP_info, info, sizeof(TRAP_info));
+	TRAP_nr = nr;
+}
+
+TEST_F(TRAP, handler)
+{
+	int ret, test;
+	struct sigaction act;
+	sigset_t mask;
+
+	memset(&act, 0, sizeof(act));
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGSYS);
+
+	act.sa_sigaction = &TRAP_action;
+	act.sa_flags = SA_SIGINFO;
+	ret = sigaction(SIGSYS, &act, NULL);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("sigaction failed");
+	}
+	ret = sigprocmask(SIG_UNBLOCK, &mask, NULL);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("sigprocmask failed");
+	}
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog);
+	ASSERT_EQ(0, ret);
+	TRAP_nr = 0;
+	memset(&TRAP_info, 0, sizeof(TRAP_info));
+	/* Expect the registers to be rolled back. (nr = error) may vary
+	 * based on arch. */
+	ret = syscall(__NR_getpid);
+	/* Silence gcc warning about volatile. */
+	test = TRAP_nr;
+	EXPECT_EQ(SIGSYS, test);
+	struct local_sigsys {
+		void *_call_addr;	/* calling user insn */
+		int _syscall;		/* triggering system call number */
+		unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
+	} *sigsys = (struct local_sigsys *)
+#ifdef si_syscall
+		&(TRAP_info.si_call_addr);
+#else
+		&TRAP_info.si_pid;
+#endif
+	EXPECT_EQ(__NR_getpid, sigsys->_syscall);
+	/* Make sure arch is non-zero. */
+	EXPECT_NE(0, sigsys->_arch);
+	EXPECT_NE(0, (unsigned long)sigsys->_call_addr);
+}
+
+FIXTURE_DATA(precedence) {
+	struct sock_fprog allow;
+	struct sock_fprog trace;
+	struct sock_fprog error;
+	struct sock_fprog trap;
+	struct sock_fprog kill;
+};
+
+FIXTURE_SETUP(precedence)
+{
+	struct sock_filter allow_insns[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_filter trace_insns[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE),
+	};
+	struct sock_filter error_insns[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO),
+	};
+	struct sock_filter trap_insns[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRAP),
+	};
+	struct sock_filter kill_insns[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL),
+	};
+
+	memset(self, 0, sizeof(*self));
+#define FILTER_ALLOC(_x) \
+	self->_x.filter = malloc(sizeof(_x##_insns)); \
+	ASSERT_NE(NULL, self->_x.filter); \
+	memcpy(self->_x.filter, &_x##_insns, sizeof(_x##_insns)); \
+	self->_x.len = (unsigned short)ARRAY_SIZE(_x##_insns)
+	FILTER_ALLOC(allow);
+	FILTER_ALLOC(trace);
+	FILTER_ALLOC(error);
+	FILTER_ALLOC(trap);
+	FILTER_ALLOC(kill);
+}
+
+FIXTURE_TEARDOWN(precedence)
+{
+#define FILTER_FREE(_x) if (self->_x.filter) free(self->_x.filter)
+	FILTER_FREE(allow);
+	FILTER_FREE(trace);
+	FILTER_FREE(error);
+	FILTER_FREE(trap);
+	FILTER_FREE(kill);
+}
+
+TEST_F(precedence, allow_ok)
+{
+	pid_t parent, res = 0;
+	long ret;
+
+	parent = getppid();
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trap);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->kill);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	res = syscall(__NR_getppid);
+	EXPECT_EQ(parent, res);
+}
+
+TEST_F_SIGNAL(precedence, kill_is_highest, SIGSYS)
+{
+	pid_t parent, res = 0;
+	long ret;
+
+	parent = getppid();
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trap);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->kill);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	res = syscall(__NR_getppid);
+	EXPECT_EQ(parent, res);
+	/* getpid() should never return. */
+	res = syscall(__NR_getpid);
+	EXPECT_EQ(0, res);
+}
+
+TEST_F_SIGNAL(precedence, kill_is_highest_in_any_order, SIGSYS)
+{
+	pid_t parent;
+	long ret;
+
+	parent = getppid();
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->kill);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trap);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* getpid() should never return. */
+	EXPECT_EQ(0, syscall(__NR_getpid));
+}
+
+TEST_F_SIGNAL(precedence, trap_is_second, SIGSYS)
+{
+	pid_t parent;
+	long ret;
+
+	parent = getppid();
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trap);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* getpid() should never return. */
+	EXPECT_EQ(0, syscall(__NR_getpid));
+}
+
+TEST_F_SIGNAL(precedence, trap_is_second_in_any_order, SIGSYS)
+{
+	pid_t parent;
+	long ret;
+
+	parent = getppid();
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trap);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* getpid() should never return. */
+	EXPECT_EQ(0, syscall(__NR_getpid));
+}
+
+TEST_F(precedence, errno_is_third)
+{
+	pid_t parent;
+	long ret;
+
+	parent = getppid();
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	EXPECT_EQ(0, syscall(__NR_getpid));
+}
+
+TEST_F(precedence, errno_is_third_in_any_order)
+{
+	pid_t parent;
+	long ret;
+
+	parent = getppid();
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	EXPECT_EQ(0, syscall(__NR_getpid));
+}
+
+TEST_F(precedence, trace_is_fourth)
+{
+	pid_t parent;
+	long ret;
+
+	parent = getppid();
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* No ptracer */
+	EXPECT_EQ(-1, syscall(__NR_getpid));
+}
+
+TEST_F(precedence, trace_is_fourth_in_any_order)
+{
+	pid_t parent;
+	long ret;
+
+	parent = getppid();
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace);
+	ASSERT_EQ(0, ret);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* No ptracer */
+	EXPECT_EQ(-1, syscall(__NR_getpid));
+}
+
+#ifndef PTRACE_O_TRACESECCOMP
+#define PTRACE_O_TRACESECCOMP	0x00000080
+#endif
+
+/* Catch the Ubuntu 12.04 value error. */
+#if PTRACE_EVENT_SECCOMP != 7
+#undef PTRACE_EVENT_SECCOMP
+#endif
+
+#ifndef PTRACE_EVENT_SECCOMP
+#define PTRACE_EVENT_SECCOMP 7
+#endif
+
+#define IS_SECCOMP_EVENT(status) ((status >> 16) == PTRACE_EVENT_SECCOMP)
+bool tracer_running;
+void tracer_stop(int sig)
+{
+	tracer_running = false;
+}
+
+typedef void tracer_func_t(struct __test_metadata *_metadata,
+			   pid_t tracee, int status, void *args);
+
+void tracer(struct __test_metadata *_metadata, int fd, pid_t tracee,
+	    tracer_func_t tracer_func, void *args)
+{
+	int ret = -1;
+	struct sigaction action = {
+		.sa_handler = tracer_stop,
+	};
+
+	/* Allow external shutdown. */
+	tracer_running = true;
+	ASSERT_EQ(0, sigaction(SIGUSR1, &action, NULL));
+
+	errno = 0;
+	while (ret == -1 && errno != EINVAL)
+		ret = ptrace(PTRACE_ATTACH, tracee, NULL, 0);
+	ASSERT_EQ(0, ret) {
+		kill(tracee, SIGKILL);
+	}
+	/* Wait for attach stop */
+	wait(NULL);
+
+	ret = ptrace(PTRACE_SETOPTIONS, tracee, NULL, PTRACE_O_TRACESECCOMP);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Failed to set PTRACE_O_TRACESECCOMP");
+		kill(tracee, SIGKILL);
+	}
+	ptrace(PTRACE_CONT, tracee, NULL, 0);
+
+	/* Unblock the tracee */
+	ASSERT_EQ(1, write(fd, "A", 1));
+	ASSERT_EQ(0, close(fd));
+
+	/* Run until we're shut down. Must assert to stop execution. */
+	while (tracer_running) {
+		int status;
+
+		if (wait(&status) != tracee)
+			continue;
+		if (WIFSIGNALED(status) || WIFEXITED(status))
+			/* Child is dead. Time to go. */
+			return;
+
+		/* Make sure this is a seccomp event. */
+		ASSERT_EQ(true, IS_SECCOMP_EVENT(status));
+
+		tracer_func(_metadata, tracee, status, args);
+
+		ret = ptrace(PTRACE_CONT, tracee, NULL, NULL);
+		ASSERT_EQ(0, ret);
+	}
+	/* Directly report the status of our test harness results. */
+	syscall(__NR_exit, _metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE);
+}
+
+/* Common tracer setup/teardown functions. */
+void cont_handler(int num)
+{ }
+pid_t setup_trace_fixture(struct __test_metadata *_metadata,
+			  tracer_func_t func, void *args)
+{
+	char sync;
+	int pipefd[2];
+	pid_t tracer_pid;
+	pid_t tracee = getpid();
+
+	/* Setup a pipe for clean synchronization. */
+	ASSERT_EQ(0, pipe(pipefd));
+
+	/* Fork a child which we'll promote to tracer */
+	tracer_pid = fork();
+	ASSERT_LE(0, tracer_pid);
+	signal(SIGALRM, cont_handler);
+	if (tracer_pid == 0) {
+		close(pipefd[0]);
+		tracer(_metadata, pipefd[1], tracee, func, args);
+		syscall(__NR_exit, 0);
+	}
+	close(pipefd[1]);
+	prctl(PR_SET_PTRACER, tracer_pid, 0, 0, 0);
+	read(pipefd[0], &sync, 1);
+	close(pipefd[0]);
+
+	return tracer_pid;
+}
+void teardown_trace_fixture(struct __test_metadata *_metadata,
+			    pid_t tracer)
+{
+	if (tracer) {
+		int status;
+		/*
+		 * Extract the exit code from the other process and
+		 * adopt it for ourselves in case its asserts failed.
+		 */
+		ASSERT_EQ(0, kill(tracer, SIGUSR1));
+		ASSERT_EQ(tracer, waitpid(tracer, &status, 0));
+		if (WEXITSTATUS(status))
+			_metadata->passed = 0;
+	}
+}
+
+/* "poke" tracer arguments and function. */
+struct tracer_args_poke_t {
+	unsigned long poke_addr;
+};
+
+void tracer_poke(struct __test_metadata *_metadata, pid_t tracee, int status,
+		 void *args)
+{
+	int ret;
+	unsigned long msg;
+	struct tracer_args_poke_t *info = (struct tracer_args_poke_t *)args;
+
+	ret = ptrace(PTRACE_GETEVENTMSG, tracee, NULL, &msg);
+	EXPECT_EQ(0, ret);
+	/* If this fails, don't try to recover. */
+	ASSERT_EQ(0x1001, msg) {
+		kill(tracee, SIGKILL);
+	}
+	/*
+	 * Poke in the message.
+	 * Registers are not touched to try to keep this relatively arch
+	 * agnostic.
+	 */
+	ret = ptrace(PTRACE_POKEDATA, tracee, info->poke_addr, 0x1001);
+	EXPECT_EQ(0, ret);
+}
+
+FIXTURE_DATA(TRACE_poke) {
+	struct sock_fprog prog;
+	pid_t tracer;
+	long poked;
+	struct tracer_args_poke_t tracer_args;
+};
+
+FIXTURE_SETUP(TRACE_poke)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1001),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+
+	self->poked = 0;
+	memset(&self->prog, 0, sizeof(self->prog));
+	self->prog.filter = malloc(sizeof(filter));
+	ASSERT_NE(NULL, self->prog.filter);
+	memcpy(self->prog.filter, filter, sizeof(filter));
+	self->prog.len = (unsigned short)ARRAY_SIZE(filter);
+
+	/* Set up tracer args. */
+	self->tracer_args.poke_addr = (unsigned long)&self->poked;
+
+	/* Launch tracer. */
+	self->tracer = setup_trace_fixture(_metadata, tracer_poke,
+					   &self->tracer_args);
+}
+
+FIXTURE_TEARDOWN(TRACE_poke)
+{
+	teardown_trace_fixture(_metadata, self->tracer);
+	if (self->prog.filter)
+		free(self->prog.filter);
+}
+
+TEST_F(TRACE_poke, read_has_side_effects)
+{
+	ssize_t ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(0, self->poked);
+	ret = read(-1, NULL, 0);
+	EXPECT_EQ(-1, ret);
+	EXPECT_EQ(0x1001, self->poked);
+}
+
+TEST_F(TRACE_poke, getpid_runs_normally)
+{
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(0, self->poked);
+	EXPECT_NE(0, syscall(__NR_getpid));
+	EXPECT_EQ(0, self->poked);
+}
+
+#if defined(__x86_64__)
+# define ARCH_REGS	struct user_regs_struct
+# define SYSCALL_NUM	orig_rax
+# define SYSCALL_RET	rax
+#elif defined(__i386__)
+# define ARCH_REGS	struct user_regs_struct
+# define SYSCALL_NUM	orig_eax
+# define SYSCALL_RET	eax
+#elif defined(__arm__)
+# define ARCH_REGS	struct pt_regs
+# define SYSCALL_NUM	ARM_r7
+# define SYSCALL_RET	ARM_r0
+#elif defined(__aarch64__)
+# define ARCH_REGS	struct user_pt_regs
+# define SYSCALL_NUM	regs[8]
+# define SYSCALL_RET	regs[0]
+#else
+# error "Do not know how to find your architecture's registers and syscalls"
+#endif
+
+/* Architecture-specific syscall fetching routine. */
+int get_syscall(struct __test_metadata *_metadata, pid_t tracee)
+{
+	struct iovec iov;
+	ARCH_REGS regs;
+
+	iov.iov_base = &regs;
+	iov.iov_len = sizeof(regs);
+	EXPECT_EQ(0, ptrace(PTRACE_GETREGSET, tracee, NT_PRSTATUS, &iov)) {
+		TH_LOG("PTRACE_GETREGSET failed");
+		return -1;
+	}
+
+	return regs.SYSCALL_NUM;
+}
+
+/* Architecture-specific syscall changing routine. */
+void change_syscall(struct __test_metadata *_metadata,
+		    pid_t tracee, int syscall)
+{
+	struct iovec iov;
+	int ret;
+	ARCH_REGS regs;
+
+	iov.iov_base = &regs;
+	iov.iov_len = sizeof(regs);
+	ret = ptrace(PTRACE_GETREGSET, tracee, NT_PRSTATUS, &iov);
+	EXPECT_EQ(0, ret);
+
+#if defined(__x86_64__) || defined(__i386__) || defined(__aarch64__)
+	{
+		regs.SYSCALL_NUM = syscall;
+	}
+
+#elif defined(__arm__)
+# ifndef PTRACE_SET_SYSCALL
+#  define PTRACE_SET_SYSCALL   23
+# endif
+	{
+		ret = ptrace(PTRACE_SET_SYSCALL, tracee, NULL, syscall);
+		EXPECT_EQ(0, ret);
+	}
+
+#else
+	ASSERT_EQ(1, 0) {
+		TH_LOG("How is the syscall changed on this architecture?");
+	}
+#endif
+
+	/* If syscall is skipped, change return value. */
+	if (syscall == -1)
+		regs.SYSCALL_RET = 1;
+
+	ret = ptrace(PTRACE_SETREGSET, tracee, NT_PRSTATUS, &iov);
+	EXPECT_EQ(0, ret);
+}
+
+void tracer_syscall(struct __test_metadata *_metadata, pid_t tracee,
+		    int status, void *args)
+{
+	int ret;
+	unsigned long msg;
+
+	/* Make sure we got the right message. */
+	ret = ptrace(PTRACE_GETEVENTMSG, tracee, NULL, &msg);
+	EXPECT_EQ(0, ret);
+
+	switch (msg) {
+	case 0x1002:
+		/* change getpid to getppid. */
+		change_syscall(_metadata, tracee, __NR_getppid);
+		break;
+	case 0x1003:
+		/* skip gettid. */
+		change_syscall(_metadata, tracee, -1);
+		break;
+	case 0x1004:
+		/* do nothing (allow getppid) */
+		break;
+	default:
+		EXPECT_EQ(0, msg) {
+			TH_LOG("Unknown PTRACE_GETEVENTMSG: 0x%lx", msg);
+			kill(tracee, SIGKILL);
+		}
+	}
+
+}
+
+FIXTURE_DATA(TRACE_syscall) {
+	struct sock_fprog prog;
+	pid_t tracer, mytid, mypid, parent;
+};
+
+FIXTURE_SETUP(TRACE_syscall)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1002),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_gettid, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1003),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getppid, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1004),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+
+	memset(&self->prog, 0, sizeof(self->prog));
+	self->prog.filter = malloc(sizeof(filter));
+	ASSERT_NE(NULL, self->prog.filter);
+	memcpy(self->prog.filter, filter, sizeof(filter));
+	self->prog.len = (unsigned short)ARRAY_SIZE(filter);
+
+	/* Prepare some testable syscall results. */
+	self->mytid = syscall(__NR_gettid);
+	ASSERT_GT(self->mytid, 0);
+	ASSERT_NE(self->mytid, 1) {
+		TH_LOG("Running this test as init is not supported. :)");
+	}
+
+	self->mypid = getpid();
+	ASSERT_GT(self->mypid, 0);
+	ASSERT_EQ(self->mytid, self->mypid);
+
+	self->parent = getppid();
+	ASSERT_GT(self->parent, 0);
+	ASSERT_NE(self->parent, self->mypid);
+
+	/* Launch tracer. */
+	self->tracer = setup_trace_fixture(_metadata, tracer_syscall, NULL);
+}
+
+FIXTURE_TEARDOWN(TRACE_syscall)
+{
+	teardown_trace_fixture(_metadata, self->tracer);
+	if (self->prog.filter)
+		free(self->prog.filter);
+}
+
+TEST_F(TRACE_syscall, syscall_allowed)
+{
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* getppid works as expected (no changes). */
+	EXPECT_EQ(self->parent, syscall(__NR_getppid));
+	EXPECT_NE(self->mypid, syscall(__NR_getppid));
+}
+
+TEST_F(TRACE_syscall, syscall_redirected)
+{
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* getpid has been redirected to getppid as expected. */
+	EXPECT_EQ(self->parent, syscall(__NR_getpid));
+	EXPECT_NE(self->mypid, syscall(__NR_getpid));
+}
+
+TEST_F(TRACE_syscall, syscall_dropped)
+{
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* gettid has been skipped and an altered return value stored. */
+	EXPECT_EQ(1, syscall(__NR_gettid));
+	EXPECT_NE(self->mytid, syscall(__NR_gettid));
+}
+
+#ifndef __NR_seccomp
+# if defined(__i386__)
+#  define __NR_seccomp 354
+# elif defined(__x86_64__)
+#  define __NR_seccomp 317
+# elif defined(__arm__)
+#  define __NR_seccomp 383
+# elif defined(__aarch64__)
+#  define __NR_seccomp 277
+# else
+#  warning "seccomp syscall number unknown for this architecture"
+#  define __NR_seccomp 0xffff
+# endif
+#endif
+
+#ifndef SECCOMP_SET_MODE_STRICT
+#define SECCOMP_SET_MODE_STRICT 0
+#endif
+
+#ifndef SECCOMP_SET_MODE_FILTER
+#define SECCOMP_SET_MODE_FILTER 1
+#endif
+
+#ifndef SECCOMP_FLAG_FILTER_TSYNC
+#define SECCOMP_FLAG_FILTER_TSYNC 1
+#endif
+
+#ifndef seccomp
+int seccomp(unsigned int op, unsigned int flags, struct sock_fprog *filter)
+{
+	errno = 0;
+	return syscall(__NR_seccomp, op, flags, filter);
+}
+#endif
+
+TEST(seccomp_syscall)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	/* Reject insane operation. */
+	ret = seccomp(-1, 0, &prog);
+	EXPECT_EQ(EINVAL, errno) {
+		TH_LOG("Did not reject crazy op value!");
+	}
+
+	/* Reject strict with flags or pointer. */
+	ret = seccomp(SECCOMP_SET_MODE_STRICT, -1, NULL);
+	EXPECT_EQ(EINVAL, errno) {
+		TH_LOG("Did not reject mode strict with flags!");
+	}
+	ret = seccomp(SECCOMP_SET_MODE_STRICT, 0, &prog);
+	EXPECT_EQ(EINVAL, errno) {
+		TH_LOG("Did not reject mode strict with uargs!");
+	}
+
+	/* Reject insane args for filter. */
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, -1, &prog);
+	EXPECT_EQ(EINVAL, errno) {
+		TH_LOG("Did not reject crazy filter flags!");
+	}
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, NULL);
+	EXPECT_EQ(EFAULT, errno) {
+		TH_LOG("Did not reject NULL filter!");
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog);
+	EXPECT_EQ(0, errno) {
+		TH_LOG("Kernel does not support SECCOMP_SET_MODE_FILTER: %s",
+			strerror(errno));
+	}
+}
+
+TEST(seccomp_syscall_mode_lock)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, NULL, 0, 0);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog);
+	EXPECT_EQ(0, ret) {
+		TH_LOG("Could not install filter!");
+	}
+
+	/* Make sure neither entry point will switch to strict. */
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_STRICT, 0, 0, 0);
+	EXPECT_EQ(EINVAL, errno) {
+		TH_LOG("Switched to mode strict!");
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_STRICT, 0, NULL);
+	EXPECT_EQ(EINVAL, errno) {
+		TH_LOG("Switched to mode strict!");
+	}
+}
+
+TEST(TSYNC_first)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, NULL, 0, 0);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FLAG_FILTER_TSYNC,
+		      &prog);
+	EXPECT_EQ(0, ret) {
+		TH_LOG("Could not install initial filter with TSYNC!");
+	}
+}
+
+#define TSYNC_SIBLINGS 2
+struct tsync_sibling {
+	pthread_t tid;
+	pid_t system_tid;
+	sem_t *started;
+	pthread_cond_t *cond;
+	pthread_mutex_t *mutex;
+	int diverge;
+	int num_waits;
+	struct sock_fprog *prog;
+	struct __test_metadata *metadata;
+};
+
+FIXTURE_DATA(TSYNC) {
+	struct sock_fprog root_prog, apply_prog;
+	struct tsync_sibling sibling[TSYNC_SIBLINGS];
+	sem_t started;
+	pthread_cond_t cond;
+	pthread_mutex_t mutex;
+	int sibling_count;
+};
+
+FIXTURE_SETUP(TSYNC)
+{
+	struct sock_filter root_filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_filter apply_filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+
+	memset(&self->root_prog, 0, sizeof(self->root_prog));
+	memset(&self->apply_prog, 0, sizeof(self->apply_prog));
+	memset(&self->sibling, 0, sizeof(self->sibling));
+	self->root_prog.filter = malloc(sizeof(root_filter));
+	ASSERT_NE(NULL, self->root_prog.filter);
+	memcpy(self->root_prog.filter, &root_filter, sizeof(root_filter));
+	self->root_prog.len = (unsigned short)ARRAY_SIZE(root_filter);
+
+	self->apply_prog.filter = malloc(sizeof(apply_filter));
+	ASSERT_NE(NULL, self->apply_prog.filter);
+	memcpy(self->apply_prog.filter, &apply_filter, sizeof(apply_filter));
+	self->apply_prog.len = (unsigned short)ARRAY_SIZE(apply_filter);
+
+	self->sibling_count = 0;
+	pthread_mutex_init(&self->mutex, NULL);
+	pthread_cond_init(&self->cond, NULL);
+	sem_init(&self->started, 0, 0);
+	self->sibling[0].tid = 0;
+	self->sibling[0].cond = &self->cond;
+	self->sibling[0].started = &self->started;
+	self->sibling[0].mutex = &self->mutex;
+	self->sibling[0].diverge = 0;
+	self->sibling[0].num_waits = 1;
+	self->sibling[0].prog = &self->root_prog;
+	self->sibling[0].metadata = _metadata;
+	self->sibling[1].tid = 0;
+	self->sibling[1].cond = &self->cond;
+	self->sibling[1].started = &self->started;
+	self->sibling[1].mutex = &self->mutex;
+	self->sibling[1].diverge = 0;
+	self->sibling[1].prog = &self->root_prog;
+	self->sibling[1].num_waits = 1;
+	self->sibling[1].metadata = _metadata;
+}
+
+FIXTURE_TEARDOWN(TSYNC)
+{
+	int sib = 0;
+
+	if (self->root_prog.filter)
+		free(self->root_prog.filter);
+	if (self->apply_prog.filter)
+		free(self->apply_prog.filter);
+
+	for ( ; sib < self->sibling_count; ++sib) {
+		struct tsync_sibling *s = &self->sibling[sib];
+		void *status;
+
+		if (!s->tid)
+			continue;
+		if (pthread_kill(s->tid, 0)) {
+			pthread_cancel(s->tid);
+			pthread_join(s->tid, &status);
+		}
+	}
+	pthread_mutex_destroy(&self->mutex);
+	pthread_cond_destroy(&self->cond);
+	sem_destroy(&self->started);
+}
+
+void *tsync_sibling(void *data)
+{
+	long ret = 0;
+	struct tsync_sibling *me = data;
+
+	me->system_tid = syscall(__NR_gettid);
+
+	pthread_mutex_lock(me->mutex);
+	if (me->diverge) {
+		/* Just re-apply the root prog to fork the tree */
+		ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER,
+				me->prog, 0, 0);
+	}
+	sem_post(me->started);
+	/* Return outside of started so parent notices failures. */
+	if (ret) {
+		pthread_mutex_unlock(me->mutex);
+		return (void *)SIBLING_EXIT_FAILURE;
+	}
+	do {
+		pthread_cond_wait(me->cond, me->mutex);
+		me->num_waits = me->num_waits - 1;
+	} while (me->num_waits);
+	pthread_mutex_unlock(me->mutex);
+
+	ret = prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0);
+	if (!ret)
+		return (void *)SIBLING_EXIT_NEWPRIVS;
+	read(0, NULL, 0);
+	return (void *)SIBLING_EXIT_UNKILLED;
+}
+
+void tsync_start_sibling(struct tsync_sibling *sibling)
+{
+	pthread_create(&sibling->tid, NULL, tsync_sibling, (void *)sibling);
+}
+
+TEST_F(TSYNC, siblings_fail_prctl)
+{
+	long ret;
+	void *status;
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_prctl, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | EINVAL),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+
+	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	/* Check prctl failure detection by requesting sib 0 diverge. */
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("setting filter failed");
+	}
+
+	self->sibling[0].diverge = 1;
+	tsync_start_sibling(&self->sibling[0]);
+	tsync_start_sibling(&self->sibling[1]);
+
+	while (self->sibling_count < TSYNC_SIBLINGS) {
+		sem_wait(&self->started);
+		self->sibling_count++;
+	}
+
+	/* Signal the threads to clean up*/
+	pthread_mutex_lock(&self->mutex);
+	ASSERT_EQ(0, pthread_cond_broadcast(&self->cond)) {
+		TH_LOG("cond broadcast non-zero");
+	}
+	pthread_mutex_unlock(&self->mutex);
+
+	/* Ensure diverging sibling failed to call prctl. */
+	pthread_join(self->sibling[0].tid, &status);
+	EXPECT_EQ(SIBLING_EXIT_FAILURE, (long)status);
+	pthread_join(self->sibling[1].tid, &status);
+	EXPECT_EQ(SIBLING_EXIT_UNKILLED, (long)status);
+}
+
+TEST_F(TSYNC, two_siblings_with_ancestor)
+{
+	long ret;
+	void *status;
+
+	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &self->root_prog);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support SECCOMP_SET_MODE_FILTER!");
+	}
+	tsync_start_sibling(&self->sibling[0]);
+	tsync_start_sibling(&self->sibling[1]);
+
+	while (self->sibling_count < TSYNC_SIBLINGS) {
+		sem_wait(&self->started);
+		self->sibling_count++;
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FLAG_FILTER_TSYNC,
+		      &self->apply_prog);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Could install filter on all threads!");
+	}
+	/* Tell the siblings to test the policy */
+	pthread_mutex_lock(&self->mutex);
+	ASSERT_EQ(0, pthread_cond_broadcast(&self->cond)) {
+		TH_LOG("cond broadcast non-zero");
+	}
+	pthread_mutex_unlock(&self->mutex);
+	/* Ensure they are both killed and don't exit cleanly. */
+	pthread_join(self->sibling[0].tid, &status);
+	EXPECT_EQ(0x0, (long)status);
+	pthread_join(self->sibling[1].tid, &status);
+	EXPECT_EQ(0x0, (long)status);
+}
+
+TEST_F(TSYNC, two_sibling_want_nnp)
+{
+	void *status;
+
+	/* start siblings before any prctl() operations */
+	tsync_start_sibling(&self->sibling[0]);
+	tsync_start_sibling(&self->sibling[1]);
+	while (self->sibling_count < TSYNC_SIBLINGS) {
+		sem_wait(&self->started);
+		self->sibling_count++;
+	}
+
+	/* Tell the siblings to test no policy */
+	pthread_mutex_lock(&self->mutex);
+	ASSERT_EQ(0, pthread_cond_broadcast(&self->cond)) {
+		TH_LOG("cond broadcast non-zero");
+	}
+	pthread_mutex_unlock(&self->mutex);
+
+	/* Ensure they are both upset about lacking nnp. */
+	pthread_join(self->sibling[0].tid, &status);
+	EXPECT_EQ(SIBLING_EXIT_NEWPRIVS, (long)status);
+	pthread_join(self->sibling[1].tid, &status);
+	EXPECT_EQ(SIBLING_EXIT_NEWPRIVS, (long)status);
+}
+
+TEST_F(TSYNC, two_siblings_with_no_filter)
+{
+	long ret;
+	void *status;
+
+	/* start siblings before any prctl() operations */
+	tsync_start_sibling(&self->sibling[0]);
+	tsync_start_sibling(&self->sibling[1]);
+	while (self->sibling_count < TSYNC_SIBLINGS) {
+		sem_wait(&self->started);
+		self->sibling_count++;
+	}
+
+	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FLAG_FILTER_TSYNC,
+		      &self->apply_prog);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Could install filter on all threads!");
+	}
+
+	/* Tell the siblings to test the policy */
+	pthread_mutex_lock(&self->mutex);
+	ASSERT_EQ(0, pthread_cond_broadcast(&self->cond)) {
+		TH_LOG("cond broadcast non-zero");
+	}
+	pthread_mutex_unlock(&self->mutex);
+
+	/* Ensure they are both killed and don't exit cleanly. */
+	pthread_join(self->sibling[0].tid, &status);
+	EXPECT_EQ(0x0, (long)status);
+	pthread_join(self->sibling[1].tid, &status);
+	EXPECT_EQ(0x0, (long)status);
+}
+
+TEST_F(TSYNC, two_siblings_with_one_divergence)
+{
+	long ret;
+	void *status;
+
+	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &self->root_prog);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support SECCOMP_SET_MODE_FILTER!");
+	}
+	self->sibling[0].diverge = 1;
+	tsync_start_sibling(&self->sibling[0]);
+	tsync_start_sibling(&self->sibling[1]);
+
+	while (self->sibling_count < TSYNC_SIBLINGS) {
+		sem_wait(&self->started);
+		self->sibling_count++;
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FLAG_FILTER_TSYNC,
+		      &self->apply_prog);
+	ASSERT_EQ(self->sibling[0].system_tid, ret) {
+		TH_LOG("Did not fail on diverged sibling.");
+	}
+
+	/* Wake the threads */
+	pthread_mutex_lock(&self->mutex);
+	ASSERT_EQ(0, pthread_cond_broadcast(&self->cond)) {
+		TH_LOG("cond broadcast non-zero");
+	}
+	pthread_mutex_unlock(&self->mutex);
+
+	/* Ensure they are both unkilled. */
+	pthread_join(self->sibling[0].tid, &status);
+	EXPECT_EQ(SIBLING_EXIT_UNKILLED, (long)status);
+	pthread_join(self->sibling[1].tid, &status);
+	EXPECT_EQ(SIBLING_EXIT_UNKILLED, (long)status);
+}
+
+TEST_F(TSYNC, two_siblings_not_under_filter)
+{
+	long ret, sib;
+	void *status;
+
+	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	/*
+	 * Sibling 0 will have its own seccomp policy
+	 * and Sibling 1 will not be under seccomp at
+	 * all. Sibling 1 will enter seccomp and 0
+	 * will cause failure.
+	 */
+	self->sibling[0].diverge = 1;
+	tsync_start_sibling(&self->sibling[0]);
+	tsync_start_sibling(&self->sibling[1]);
+
+	while (self->sibling_count < TSYNC_SIBLINGS) {
+		sem_wait(&self->started);
+		self->sibling_count++;
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &self->root_prog);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support SECCOMP_SET_MODE_FILTER!");
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FLAG_FILTER_TSYNC,
+		      &self->apply_prog);
+	ASSERT_EQ(ret, self->sibling[0].system_tid) {
+		TH_LOG("Did not fail on diverged sibling.");
+	}
+	sib = 1;
+	if (ret == self->sibling[0].system_tid)
+		sib = 0;
+
+	pthread_mutex_lock(&self->mutex);
+
+	/* Increment the other siblings num_waits so we can clean up
+	 * the one we just saw.
+	 */
+	self->sibling[!sib].num_waits += 1;
+
+	/* Signal the thread to clean up*/
+	ASSERT_EQ(0, pthread_cond_broadcast(&self->cond)) {
+		TH_LOG("cond broadcast non-zero");
+	}
+	pthread_mutex_unlock(&self->mutex);
+	pthread_join(self->sibling[sib].tid, &status);
+	EXPECT_EQ(SIBLING_EXIT_UNKILLED, (long)status);
+	/* Poll for actual task death. pthread_join doesn't guarantee it. */
+	while (!kill(self->sibling[sib].system_tid, 0))
+		sleep(0.1);
+	/* Switch to the remaining sibling */
+	sib = !sib;
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FLAG_FILTER_TSYNC,
+		      &self->apply_prog);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Expected the remaining sibling to sync");
+	};
+
+	pthread_mutex_lock(&self->mutex);
+
+	/* If remaining sibling didn't have a chance to wake up during
+	 * the first broadcast, manually reduce the num_waits now.
+	 */
+	if (self->sibling[sib].num_waits > 1)
+		self->sibling[sib].num_waits = 1;
+	ASSERT_EQ(0, pthread_cond_broadcast(&self->cond)) {
+		TH_LOG("cond broadcast non-zero");
+	}
+	pthread_mutex_unlock(&self->mutex);
+	pthread_join(self->sibling[sib].tid, &status);
+	EXPECT_EQ(0, (long)status);
+	/* Poll for actual task death. pthread_join doesn't guarantee it. */
+	while (!kill(self->sibling[sib].system_tid, 0))
+		sleep(0.1);
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FLAG_FILTER_TSYNC,
+		      &self->apply_prog);
+	ASSERT_EQ(0, ret);  /* just us chickens */
+}
+
+/* Make sure restarted syscalls are seen directly as "restart_syscall". */
+TEST(syscall_restart)
+{
+	long ret;
+	unsigned long msg;
+	pid_t child_pid;
+	int pipefd[2];
+	int status;
+	siginfo_t info = { };
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
+			 offsetof(struct seccomp_data, nr)),
+
+#ifdef __NR_sigreturn
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_sigreturn, 6, 0),
+#endif
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 5, 0),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_exit, 4, 0),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_rt_sigreturn, 3, 0),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_poll, 4, 0),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_restart_syscall, 4, 0),
+
+		/* Allow __NR_write for easy logging. */
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_write, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE|0x100), /* poll */
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE|0x200), /* restart */
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+
+	ASSERT_EQ(0, pipe(pipefd));
+
+	child_pid = fork();
+	ASSERT_LE(0, child_pid);
+	if (child_pid == 0) {
+		/* Child uses EXPECT not ASSERT to deliver status correctly. */
+		char buf = ' ';
+		struct pollfd fds = {
+			.fd = pipefd[0],
+			.events = POLLIN,
+		};
+
+		/* Attach parent as tracer and stop. */
+		EXPECT_EQ(0, ptrace(PTRACE_TRACEME));
+		EXPECT_EQ(0, raise(SIGSTOP));
+
+		EXPECT_EQ(0, close(pipefd[1]));
+
+		EXPECT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+			TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+		}
+
+		ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+		EXPECT_EQ(0, ret) {
+			TH_LOG("Failed to install filter!");
+		}
+
+		EXPECT_EQ(1, read(pipefd[0], &buf, 1)) {
+			TH_LOG("Failed to read() sync from parent");
+		}
+		EXPECT_EQ('.', buf) {
+			TH_LOG("Failed to get sync data from read()");
+		}
+
+		/* Start poll to be interrupted. */
+		errno = 0;
+		EXPECT_EQ(1, poll(&fds, 1, -1)) {
+			TH_LOG("Call to poll() failed (errno %d)", errno);
+		}
+
+		/* Read final sync from parent. */
+		EXPECT_EQ(1, read(pipefd[0], &buf, 1)) {
+			TH_LOG("Failed final read() from parent");
+		}
+		EXPECT_EQ('!', buf) {
+			TH_LOG("Failed to get final data from read()");
+		}
+
+		/* Directly report the status of our test harness results. */
+		syscall(__NR_exit, _metadata->passed ? EXIT_SUCCESS
+						     : EXIT_FAILURE);
+	}
+	EXPECT_EQ(0, close(pipefd[0]));
+
+	/* Attach to child, setup options, and release. */
+	ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0));
+	ASSERT_EQ(true, WIFSTOPPED(status));
+	ASSERT_EQ(0, ptrace(PTRACE_SETOPTIONS, child_pid, NULL,
+			    PTRACE_O_TRACESECCOMP));
+	ASSERT_EQ(0, ptrace(PTRACE_CONT, child_pid, NULL, 0));
+	ASSERT_EQ(1, write(pipefd[1], ".", 1));
+
+	/* Wait for poll() to start. */
+	ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0));
+	ASSERT_EQ(true, WIFSTOPPED(status));
+	ASSERT_EQ(SIGTRAP, WSTOPSIG(status));
+	ASSERT_EQ(PTRACE_EVENT_SECCOMP, (status >> 16));
+	ASSERT_EQ(0, ptrace(PTRACE_GETEVENTMSG, child_pid, NULL, &msg));
+	ASSERT_EQ(0x100, msg);
+	EXPECT_EQ(__NR_poll, get_syscall(_metadata, child_pid));
+
+	/* Might as well check siginfo for sanity while we're here. */
+	ASSERT_EQ(0, ptrace(PTRACE_GETSIGINFO, child_pid, NULL, &info));
+	ASSERT_EQ(SIGTRAP, info.si_signo);
+	ASSERT_EQ(SIGTRAP | (PTRACE_EVENT_SECCOMP << 8), info.si_code);
+	EXPECT_EQ(0, info.si_errno);
+	EXPECT_EQ(getuid(), info.si_uid);
+	/* Verify signal delivery came from child (seccomp-triggered). */
+	EXPECT_EQ(child_pid, info.si_pid);
+
+	/* Interrupt poll with SIGSTOP (which we'll need to handle). */
+	ASSERT_EQ(0, kill(child_pid, SIGSTOP));
+	ASSERT_EQ(0, ptrace(PTRACE_CONT, child_pid, NULL, 0));
+	ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0));
+	ASSERT_EQ(true, WIFSTOPPED(status));
+	ASSERT_EQ(SIGSTOP, WSTOPSIG(status));
+	/* Verify signal delivery came from parent now. */
+	ASSERT_EQ(0, ptrace(PTRACE_GETSIGINFO, child_pid, NULL, &info));
+	EXPECT_EQ(getpid(), info.si_pid);
+
+	/* Restart poll with SIGCONT, which triggers restart_syscall. */
+	ASSERT_EQ(0, kill(child_pid, SIGCONT));
+	ASSERT_EQ(0, ptrace(PTRACE_CONT, child_pid, NULL, 0));
+	ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0));
+	ASSERT_EQ(true, WIFSTOPPED(status));
+	ASSERT_EQ(SIGCONT, WSTOPSIG(status));
+	ASSERT_EQ(0, ptrace(PTRACE_CONT, child_pid, NULL, 0));
+
+	/* Wait for restart_syscall() to start. */
+	ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0));
+	ASSERT_EQ(true, WIFSTOPPED(status));
+	ASSERT_EQ(SIGTRAP, WSTOPSIG(status));
+	ASSERT_EQ(PTRACE_EVENT_SECCOMP, (status >> 16));
+	ASSERT_EQ(0, ptrace(PTRACE_GETEVENTMSG, child_pid, NULL, &msg));
+	ASSERT_EQ(0x200, msg);
+	ret = get_syscall(_metadata, child_pid);
+#if defined(__arm__)
+	/* FIXME: ARM does not expose true syscall in registers. */
+	EXPECT_EQ(__NR_poll, ret);
+#else
+	EXPECT_EQ(__NR_restart_syscall, ret);
+#endif
+
+	/* Write again to end poll. */
+	ASSERT_EQ(0, ptrace(PTRACE_CONT, child_pid, NULL, 0));
+	ASSERT_EQ(1, write(pipefd[1], "!", 1));
+	EXPECT_EQ(0, close(pipefd[1]));
+
+	ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0));
+	if (WIFSIGNALED(status) || WEXITSTATUS(status))
+		_metadata->passed = 0;
+}
+
+/*
+ * TODO:
+ * - add microbenchmarks
+ * - expand NNP testing
+ * - better arch-specific TRACE and TRAP handlers.
+ * - endianness checking when appropriate
+ * - 64-bit arg prodding
+ * - arch value testing (x86 modes especially)
+ * - ...
+ */
+
+TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/seccomp/test_harness.h b/tools/testing/selftests/seccomp/test_harness.h
new file mode 100644
index 0000000000000000000000000000000000000000..977a6afc448921858992bb02249f1855a5730ae7
--- /dev/null
+++ b/tools/testing/selftests/seccomp/test_harness.h
@@ -0,0 +1,537 @@
+/*
+ * Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by the GPLv2 license.
+ *
+ * test_harness.h: simple C unit test helper.
+ *
+ * Usage:
+ *   #include "test_harness.h"
+ *   TEST(standalone_test) {
+ *     do_some_stuff;
+ *     EXPECT_GT(10, stuff) {
+ *        stuff_state_t state;
+ *        enumerate_stuff_state(&state);
+ *        TH_LOG("expectation failed with state: %s", state.msg);
+ *     }
+ *     more_stuff;
+ *     ASSERT_NE(some_stuff, NULL) TH_LOG("how did it happen?!");
+ *     last_stuff;
+ *     EXPECT_EQ(0, last_stuff);
+ *   }
+ *
+ *   FIXTURE(my_fixture) {
+ *     mytype_t *data;
+ *     int awesomeness_level;
+ *   };
+ *   FIXTURE_SETUP(my_fixture) {
+ *     self->data = mytype_new();
+ *     ASSERT_NE(NULL, self->data);
+ *   }
+ *   FIXTURE_TEARDOWN(my_fixture) {
+ *     mytype_free(self->data);
+ *   }
+ *   TEST_F(my_fixture, data_is_good) {
+ *     EXPECT_EQ(1, is_my_data_good(self->data));
+ *   }
+ *
+ *   TEST_HARNESS_MAIN
+ *
+ * API inspired by code.google.com/p/googletest
+ */
+#ifndef TEST_HARNESS_H_
+#define TEST_HARNESS_H_
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+/* All exported functionality should be declared through this macro. */
+#define TEST_API(x) _##x
+
+/*
+ * Exported APIs
+ */
+
+/* TEST(name) { implementation }
+ * Defines a test by name.
+ * Names must be unique and tests must not be run in parallel.  The
+ * implementation containing block is a function and scoping should be treated
+ * as such.  Returning early may be performed with a bare "return;" statement.
+ *
+ * EXPECT_* and ASSERT_* are valid in a TEST() { } context.
+ */
+#define TEST TEST_API(TEST)
+
+/* TEST_SIGNAL(name, signal) { implementation }
+ * Defines a test by name and the expected term signal.
+ * Names must be unique and tests must not be run in parallel.  The
+ * implementation containing block is a function and scoping should be treated
+ * as such.  Returning early may be performed with a bare "return;" statement.
+ *
+ * EXPECT_* and ASSERT_* are valid in a TEST() { } context.
+ */
+#define TEST_SIGNAL TEST_API(TEST_SIGNAL)
+
+/* FIXTURE(datatype name) {
+ *   type property1;
+ *   ...
+ * };
+ * Defines the data provided to TEST_F()-defined tests as |self|.  It should be
+ * populated and cleaned up using FIXTURE_SETUP and FIXTURE_TEARDOWN.
+ */
+#define FIXTURE TEST_API(FIXTURE)
+
+/* FIXTURE_DATA(datatype name)
+ * This call may be used when the type of the fixture data
+ * is needed.  In general, this should not be needed unless
+ * the |self| is being passed to a helper directly.
+ */
+#define FIXTURE_DATA TEST_API(FIXTURE_DATA)
+
+/* FIXTURE_SETUP(fixture name) { implementation }
+ * Populates the required "setup" function for a fixture.  An instance of the
+ * datatype defined with _FIXTURE_DATA will be exposed as |self| for the
+ * implementation.
+ *
+ * ASSERT_* are valid for use in this context and will prempt the execution
+ * of any dependent fixture tests.
+ *
+ * A bare "return;" statement may be used to return early.
+ */
+#define FIXTURE_SETUP TEST_API(FIXTURE_SETUP)
+
+/* FIXTURE_TEARDOWN(fixture name) { implementation }
+ * Populates the required "teardown" function for a fixture.  An instance of the
+ * datatype defined with _FIXTURE_DATA will be exposed as |self| for the
+ * implementation to clean up.
+ *
+ * A bare "return;" statement may be used to return early.
+ */
+#define FIXTURE_TEARDOWN TEST_API(FIXTURE_TEARDOWN)
+
+/* TEST_F(fixture, name) { implementation }
+ * Defines a test that depends on a fixture (e.g., is part of a test case).
+ * Very similar to TEST() except that |self| is the setup instance of fixture's
+ * datatype exposed for use by the implementation.
+ */
+#define TEST_F TEST_API(TEST_F)
+
+#define TEST_F_SIGNAL TEST_API(TEST_F_SIGNAL)
+
+/* Use once to append a main() to the test file. E.g.,
+ *   TEST_HARNESS_MAIN
+ */
+#define TEST_HARNESS_MAIN TEST_API(TEST_HARNESS_MAIN)
+
+/*
+ * Operators for use in TEST and TEST_F.
+ * ASSERT_* calls will stop test execution immediately.
+ * EXPECT_* calls will emit a failure warning, note it, and continue.
+ */
+
+/* ASSERT_EQ(expected, measured): expected == measured */
+#define ASSERT_EQ TEST_API(ASSERT_EQ)
+/* ASSERT_NE(expected, measured): expected != measured */
+#define ASSERT_NE TEST_API(ASSERT_NE)
+/* ASSERT_LT(expected, measured): expected < measured */
+#define ASSERT_LT TEST_API(ASSERT_LT)
+/* ASSERT_LE(expected, measured): expected <= measured */
+#define ASSERT_LE TEST_API(ASSERT_LE)
+/* ASSERT_GT(expected, measured): expected > measured */
+#define ASSERT_GT TEST_API(ASSERT_GT)
+/* ASSERT_GE(expected, measured): expected >= measured */
+#define ASSERT_GE TEST_API(ASSERT_GE)
+/* ASSERT_NULL(measured): NULL == measured */
+#define ASSERT_NULL TEST_API(ASSERT_NULL)
+/* ASSERT_TRUE(measured): measured != 0 */
+#define ASSERT_TRUE TEST_API(ASSERT_TRUE)
+/* ASSERT_FALSE(measured): measured == 0 */
+#define ASSERT_FALSE TEST_API(ASSERT_FALSE)
+/* ASSERT_STREQ(expected, measured): !strcmp(expected, measured) */
+#define ASSERT_STREQ TEST_API(ASSERT_STREQ)
+/* ASSERT_STRNE(expected, measured): strcmp(expected, measured) */
+#define ASSERT_STRNE TEST_API(ASSERT_STRNE)
+/* EXPECT_EQ(expected, measured): expected == measured */
+#define EXPECT_EQ TEST_API(EXPECT_EQ)
+/* EXPECT_NE(expected, measured): expected != measured */
+#define EXPECT_NE TEST_API(EXPECT_NE)
+/* EXPECT_LT(expected, measured): expected < measured */
+#define EXPECT_LT TEST_API(EXPECT_LT)
+/* EXPECT_LE(expected, measured): expected <= measured */
+#define EXPECT_LE TEST_API(EXPECT_LE)
+/* EXPECT_GT(expected, measured): expected > measured */
+#define EXPECT_GT TEST_API(EXPECT_GT)
+/* EXPECT_GE(expected, measured): expected >= measured */
+#define EXPECT_GE TEST_API(EXPECT_GE)
+/* EXPECT_NULL(measured): NULL == measured */
+#define EXPECT_NULL TEST_API(EXPECT_NULL)
+/* EXPECT_TRUE(measured): 0 != measured */
+#define EXPECT_TRUE TEST_API(EXPECT_TRUE)
+/* EXPECT_FALSE(measured): 0 == measured */
+#define EXPECT_FALSE TEST_API(EXPECT_FALSE)
+/* EXPECT_STREQ(expected, measured): !strcmp(expected, measured) */
+#define EXPECT_STREQ TEST_API(EXPECT_STREQ)
+/* EXPECT_STRNE(expected, measured): strcmp(expected, measured) */
+#define EXPECT_STRNE TEST_API(EXPECT_STRNE)
+
+/* TH_LOG(format, ...)
+ * Optional debug logging function available for use in tests.
+ * Logging may be enabled or disabled by defining TH_LOG_ENABLED.
+ * E.g., #define TH_LOG_ENABLED 1
+ * If no definition is provided, logging is enabled by default.
+ */
+#define TH_LOG  TEST_API(TH_LOG)
+
+/*
+ * Internal implementation.
+ *
+ */
+
+/* Utilities exposed to the test definitions */
+#ifndef TH_LOG_STREAM
+#  define TH_LOG_STREAM stderr
+#endif
+
+#ifndef TH_LOG_ENABLED
+#  define TH_LOG_ENABLED 1
+#endif
+
+#define _TH_LOG(fmt, ...) do { \
+	if (TH_LOG_ENABLED) \
+		__TH_LOG(fmt, ##__VA_ARGS__); \
+} while (0)
+
+/* Unconditional logger for internal use. */
+#define __TH_LOG(fmt, ...) \
+		fprintf(TH_LOG_STREAM, "%s:%d:%s:" fmt "\n", \
+			__FILE__, __LINE__, _metadata->name, ##__VA_ARGS__)
+
+/* Defines the test function and creates the registration stub. */
+#define _TEST(test_name) __TEST_IMPL(test_name, -1)
+
+#define _TEST_SIGNAL(test_name, signal) __TEST_IMPL(test_name, signal)
+
+#define __TEST_IMPL(test_name, _signal) \
+	static void test_name(struct __test_metadata *_metadata); \
+	static struct __test_metadata _##test_name##_object = \
+		{ name: "global." #test_name, \
+		  fn: &test_name, termsig: _signal }; \
+	static void __attribute__((constructor)) _register_##test_name(void) \
+	{ \
+		__register_test(&_##test_name##_object); \
+	} \
+	static void test_name( \
+		struct __test_metadata __attribute__((unused)) *_metadata)
+
+/* Wraps the struct name so we have one less argument to pass around. */
+#define _FIXTURE_DATA(fixture_name) struct _test_data_##fixture_name
+
+/* Called once per fixture to setup the data and register. */
+#define _FIXTURE(fixture_name) \
+	static void __attribute__((constructor)) \
+	_register_##fixture_name##_data(void) \
+	{ \
+		__fixture_count++; \
+	} \
+	_FIXTURE_DATA(fixture_name)
+
+/* Prepares the setup function for the fixture.  |_metadata| is included
+ * so that ASSERT_* work as a convenience.
+ */
+#define _FIXTURE_SETUP(fixture_name) \
+	void fixture_name##_setup( \
+		struct __test_metadata __attribute__((unused)) *_metadata, \
+		_FIXTURE_DATA(fixture_name) __attribute__((unused)) *self)
+#define _FIXTURE_TEARDOWN(fixture_name) \
+	void fixture_name##_teardown( \
+		struct __test_metadata __attribute__((unused)) *_metadata, \
+		_FIXTURE_DATA(fixture_name) __attribute__((unused)) *self)
+
+/* Emits test registration and helpers for fixture-based test
+ * cases.
+ * TODO(wad) register fixtures on dedicated test lists.
+ */
+#define _TEST_F(fixture_name, test_name) \
+	__TEST_F_IMPL(fixture_name, test_name, -1)
+
+#define _TEST_F_SIGNAL(fixture_name, test_name, signal) \
+	__TEST_F_IMPL(fixture_name, test_name, signal)
+
+#define __TEST_F_IMPL(fixture_name, test_name, signal) \
+	static void fixture_name##_##test_name( \
+		struct __test_metadata *_metadata, \
+		_FIXTURE_DATA(fixture_name) *self); \
+	static inline void wrapper_##fixture_name##_##test_name( \
+		struct __test_metadata *_metadata) \
+	{ \
+		/* fixture data is alloced, setup, and torn down per call. */ \
+		_FIXTURE_DATA(fixture_name) self; \
+		memset(&self, 0, sizeof(_FIXTURE_DATA(fixture_name))); \
+		fixture_name##_setup(_metadata, &self); \
+		/* Let setup failure terminate early. */ \
+		if (!_metadata->passed) \
+			return; \
+		fixture_name##_##test_name(_metadata, &self); \
+		fixture_name##_teardown(_metadata, &self); \
+	} \
+	static struct __test_metadata \
+		      _##fixture_name##_##test_name##_object = { \
+		name: #fixture_name "." #test_name, \
+		fn: &wrapper_##fixture_name##_##test_name, \
+		termsig: signal, \
+	 }; \
+	static void __attribute__((constructor)) \
+			_register_##fixture_name##_##test_name(void) \
+	{ \
+		__register_test(&_##fixture_name##_##test_name##_object); \
+	} \
+	static void fixture_name##_##test_name( \
+		struct __test_metadata __attribute__((unused)) *_metadata, \
+		_FIXTURE_DATA(fixture_name) __attribute__((unused)) *self)
+
+/* Exports a simple wrapper to run the test harness. */
+#define _TEST_HARNESS_MAIN \
+	static void __attribute__((constructor)) \
+	__constructor_order_last(void) \
+	{ \
+		if (!__constructor_order) \
+			__constructor_order = _CONSTRUCTOR_ORDER_BACKWARD; \
+	} \
+	int main(int argc, char **argv) { \
+		return test_harness_run(argc, argv); \
+	}
+
+#define _ASSERT_EQ(_expected, _seen) \
+	__EXPECT(_expected, _seen, ==, 1)
+#define _ASSERT_NE(_expected, _seen) \
+	__EXPECT(_expected, _seen, !=, 1)
+#define _ASSERT_LT(_expected, _seen) \
+	__EXPECT(_expected, _seen, <, 1)
+#define _ASSERT_LE(_expected, _seen) \
+	__EXPECT(_expected, _seen, <=, 1)
+#define _ASSERT_GT(_expected, _seen) \
+	__EXPECT(_expected, _seen, >, 1)
+#define _ASSERT_GE(_expected, _seen) \
+	__EXPECT(_expected, _seen, >=, 1)
+#define _ASSERT_NULL(_seen) \
+	__EXPECT(NULL, _seen, ==, 1)
+
+#define _ASSERT_TRUE(_seen) \
+	_ASSERT_NE(0, _seen)
+#define _ASSERT_FALSE(_seen) \
+	_ASSERT_EQ(0, _seen)
+#define _ASSERT_STREQ(_expected, _seen) \
+	__EXPECT_STR(_expected, _seen, ==, 1)
+#define _ASSERT_STRNE(_expected, _seen) \
+	__EXPECT_STR(_expected, _seen, !=, 1)
+
+#define _EXPECT_EQ(_expected, _seen) \
+	__EXPECT(_expected, _seen, ==, 0)
+#define _EXPECT_NE(_expected, _seen) \
+	__EXPECT(_expected, _seen, !=, 0)
+#define _EXPECT_LT(_expected, _seen) \
+	__EXPECT(_expected, _seen, <, 0)
+#define _EXPECT_LE(_expected, _seen) \
+	__EXPECT(_expected, _seen, <=, 0)
+#define _EXPECT_GT(_expected, _seen) \
+	__EXPECT(_expected, _seen, >, 0)
+#define _EXPECT_GE(_expected, _seen) \
+	__EXPECT(_expected, _seen, >=, 0)
+
+#define _EXPECT_NULL(_seen) \
+	__EXPECT(NULL, _seen, ==, 0)
+#define _EXPECT_TRUE(_seen) \
+	_EXPECT_NE(0, _seen)
+#define _EXPECT_FALSE(_seen) \
+	_EXPECT_EQ(0, _seen)
+
+#define _EXPECT_STREQ(_expected, _seen) \
+	__EXPECT_STR(_expected, _seen, ==, 0)
+#define _EXPECT_STRNE(_expected, _seen) \
+	__EXPECT_STR(_expected, _seen, !=, 0)
+
+#define ARRAY_SIZE(a)	(sizeof(a) / sizeof(a[0]))
+
+/* Support an optional handler after and ASSERT_* or EXPECT_*.  The approach is
+ * not thread-safe, but it should be fine in most sane test scenarios.
+ *
+ * Using __bail(), which optionally abort()s, is the easiest way to early
+ * return while still providing an optional block to the API consumer.
+ */
+#define OPTIONAL_HANDLER(_assert) \
+	for (; _metadata->trigger;  _metadata->trigger = __bail(_assert))
+
+#define __EXPECT(_expected, _seen, _t, _assert) do { \
+	/* Avoid multiple evaluation of the cases */ \
+	__typeof__(_expected) __exp = (_expected); \
+	__typeof__(_seen) __seen = (_seen); \
+	if (!(__exp _t __seen)) { \
+		unsigned long long __exp_print = 0; \
+		unsigned long long __seen_print = 0; \
+		/* Avoid casting complaints the scariest way we can. */ \
+		memcpy(&__exp_print, &__exp, sizeof(__exp)); \
+		memcpy(&__seen_print, &__seen, sizeof(__seen)); \
+		__TH_LOG("Expected %s (%llu) %s %s (%llu)", \
+			 #_expected, __exp_print, #_t, \
+			 #_seen, __seen_print); \
+		_metadata->passed = 0; \
+		/* Ensure the optional handler is triggered */ \
+		_metadata->trigger = 1; \
+	} \
+} while (0); OPTIONAL_HANDLER(_assert)
+
+#define __EXPECT_STR(_expected, _seen, _t, _assert) do { \
+	const char *__exp = (_expected); \
+	const char *__seen = (_seen); \
+	if (!(strcmp(__exp, __seen) _t 0))  { \
+		__TH_LOG("Expected '%s' %s '%s'.", __exp, #_t, __seen); \
+		_metadata->passed = 0; \
+		_metadata->trigger = 1; \
+	} \
+} while (0); OPTIONAL_HANDLER(_assert)
+
+/* Contains all the information for test execution and status checking. */
+struct __test_metadata {
+	const char *name;
+	void (*fn)(struct __test_metadata *);
+	int termsig;
+	int passed;
+	int trigger; /* extra handler after the evaluation */
+	struct __test_metadata *prev, *next;
+};
+
+/* Storage for the (global) tests to be run. */
+static struct __test_metadata *__test_list;
+static unsigned int __test_count;
+static unsigned int __fixture_count;
+static int __constructor_order;
+
+#define _CONSTRUCTOR_ORDER_FORWARD   1
+#define _CONSTRUCTOR_ORDER_BACKWARD -1
+
+/*
+ * Since constructors are called in reverse order, reverse the test
+ * list so tests are run in source declaration order.
+ * https://gcc.gnu.org/onlinedocs/gccint/Initialization.html
+ * However, it seems not all toolchains do this correctly, so use
+ * __constructor_order to detect which direction is called first
+ * and adjust list building logic to get things running in the right
+ * direction.
+ */
+static inline void __register_test(struct __test_metadata *t)
+{
+	__test_count++;
+	/* Circular linked list where only prev is circular. */
+	if (__test_list == NULL) {
+		__test_list = t;
+		t->next = NULL;
+		t->prev = t;
+		return;
+	}
+	if (__constructor_order == _CONSTRUCTOR_ORDER_FORWARD) {
+		t->next = NULL;
+		t->prev = __test_list->prev;
+		t->prev->next = t;
+		__test_list->prev = t;
+	} else {
+		t->next = __test_list;
+		t->next->prev = t;
+		t->prev = t;
+		__test_list = t;
+	}
+}
+
+static inline int __bail(int for_realz)
+{
+	if (for_realz)
+		abort();
+	return 0;
+}
+
+void __run_test(struct __test_metadata *t)
+{
+	pid_t child_pid;
+	int status;
+
+	t->passed = 1;
+	t->trigger = 0;
+	printf("[ RUN      ] %s\n", t->name);
+	child_pid = fork();
+	if (child_pid < 0) {
+		printf("ERROR SPAWNING TEST CHILD\n");
+		t->passed = 0;
+	} else if (child_pid == 0) {
+		t->fn(t);
+		_exit(t->passed);
+	} else {
+		/* TODO(wad) add timeout support. */
+		waitpid(child_pid, &status, 0);
+		if (WIFEXITED(status)) {
+			t->passed = t->termsig == -1 ? WEXITSTATUS(status) : 0;
+			if (t->termsig != -1) {
+				fprintf(TH_LOG_STREAM,
+					"%s: Test exited normally "
+					"instead of by signal (code: %d)\n",
+					t->name,
+					WEXITSTATUS(status));
+			}
+		} else if (WIFSIGNALED(status)) {
+			t->passed = 0;
+			if (WTERMSIG(status) == SIGABRT) {
+				fprintf(TH_LOG_STREAM,
+					"%s: Test terminated by assertion\n",
+					t->name);
+			} else if (WTERMSIG(status) == t->termsig) {
+				t->passed = 1;
+			} else {
+				fprintf(TH_LOG_STREAM,
+					"%s: Test terminated unexpectedly "
+					"by signal %d\n",
+					t->name,
+					WTERMSIG(status));
+			}
+		} else {
+			fprintf(TH_LOG_STREAM,
+				"%s: Test ended in some other way [%u]\n",
+				t->name,
+				status);
+		}
+	}
+	printf("[     %4s ] %s\n", (t->passed ? "OK" : "FAIL"), t->name);
+}
+
+static int test_harness_run(int __attribute__((unused)) argc,
+			    char __attribute__((unused)) **argv)
+{
+	struct __test_metadata *t;
+	int ret = 0;
+	unsigned int count = 0;
+	unsigned int pass_count = 0;
+
+	/* TODO(wad) add optional arguments similar to gtest. */
+	printf("[==========] Running %u tests from %u test cases.\n",
+	       __test_count, __fixture_count + 1);
+	for (t = __test_list; t; t = t->next) {
+		count++;
+		__run_test(t);
+		if (t->passed)
+			pass_count++;
+		else
+			ret = 1;
+	}
+	printf("[==========] %u / %u tests passed.\n", pass_count, count);
+	printf("[  %s  ]\n", (ret ? "FAILED" : "PASSED"));
+	return ret;
+}
+
+static void __attribute__((constructor)) __constructor_order_first(void)
+{
+	if (!__constructor_order)
+		__constructor_order = _CONSTRUCTOR_ORDER_FORWARD;
+}
+
+#endif  /* TEST_HARNESS_H_ */