Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2997 insertions, 0 deletions

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
new file mode 100644
index 000000000..14cad657b
--- /dev/null
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -0,0 +1,2997 @@
+/*
+ * 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 <sys/types.h>
+
+/*
+ * glibc 2.26 and later have SIGSYS in siginfo_t. Before that,
+ * we need to use the kernel's siginfo.h file and trick glibc
+ * into accepting it.
+ */
+#if !__GLIBC_PREREQ(2, 26)
+# include <asm/siginfo.h>
+# define __have_siginfo_t 1
+# define __have_sigval_t 1
+# define __have_sigevent_t 1
+#endif
+
+#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 <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <string.h>
+#include <time.h>
+#include <linux/elf.h>
+#include <sys/uio.h>
+#include <sys/utsname.h>
+#include <sys/fcntl.h>
+#include <sys/mman.h>
+#include <sys/times.h>
+
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <sys/syscall.h>
+
+#include "../kselftest_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_ALLOW
+struct seccomp_data {
+	int nr;
+	__u32 arch;
+	__u64 instruction_pointer;
+	__u64 args[6];
+};
+#endif
+
+#ifndef SECCOMP_RET_KILL_PROCESS
+#define SECCOMP_RET_KILL_PROCESS 0x80000000U /* kill the process */
+#define SECCOMP_RET_KILL_THREAD	 0x00000000U /* kill the thread */
+#endif
+#ifndef SECCOMP_RET_KILL
+#define SECCOMP_RET_KILL	 SECCOMP_RET_KILL_THREAD
+#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 */
+#endif
+#ifndef SECCOMP_RET_LOG
+#define SECCOMP_RET_LOG		 0x7ffc0000U /* allow after logging */
+#endif
+
+#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
+# elif defined(__hppa__)
+#  define __NR_seccomp 338
+# elif defined(__powerpc__)
+#  define __NR_seccomp 358
+# elif defined(__s390__)
+#  define __NR_seccomp 348
+# 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_GET_ACTION_AVAIL
+#define SECCOMP_GET_ACTION_AVAIL 2
+#endif
+
+#ifndef SECCOMP_FILTER_FLAG_TSYNC
+#define SECCOMP_FILTER_FLAG_TSYNC (1UL << 0)
+#endif
+
+#ifndef SECCOMP_FILTER_FLAG_LOG
+#define SECCOMP_FILTER_FLAG_LOG (1UL << 1)
+#endif
+
+#ifndef SECCOMP_FILTER_FLAG_SPEC_ALLOW
+#define SECCOMP_FILTER_FLAG_SPEC_ALLOW (1UL << 2)
+#endif
+
+#ifndef PTRACE_SECCOMP_GET_METADATA
+#define PTRACE_SECCOMP_GET_METADATA	0x420d
+
+struct seccomp_metadata {
+	__u64 filter_off;       /* Input: which filter */
+	__u64 flags;             /* Output: filter's flags */
+};
+#endif
+
+#ifndef seccomp
+int seccomp(unsigned int op, unsigned int flags, void *args)
+{
+	errno = 0;
+	return syscall(__NR_seccomp, op, flags, args);
+}
+#endif
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#define syscall_arg(_n) (offsetof(struct seccomp_data, args[_n]))
+#elif __BYTE_ORDER == __BIG_ENDIAN
+#define syscall_arg(_n) (offsetof(struct seccomp_data, args[_n]) + sizeof(__u32))
+#else
+#error "wut? Unknown __BYTE_ORDER?!"
+#endif
+
+#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, 0);
+}
+
+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(log_all)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_LOG),
+	};
+	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);
+
+	/* getppid() should succeed and be logged (no check for logging) */
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+}
+
+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)
+{
+	void *fatal_address;
+	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_times, 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,
+			(unsigned long)&fatal_address, 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();
+	struct tms timebuf;
+	clock_t clock = times(&timebuf);
+
+	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_LE(clock, syscall(__NR_times, &timebuf));
+	/* times() should never return. */
+	EXPECT_EQ(0, syscall(__NR_times, &fatal_address));
+}
+
+TEST_SIGNAL(KILL_one_arg_six, SIGSYS)
+{
+#ifndef __NR_mmap2
+	int sysno = __NR_mmap;
+#else
+	int sysno = __NR_mmap2;
+#endif
+	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, sysno, 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();
+	int fd;
+	void *map1, *map2;
+	int page_size = sysconf(_SC_PAGESIZE);
+
+	ASSERT_LT(0, page_size);
+
+	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);
+
+	fd = open("/dev/zero", O_RDONLY);
+	ASSERT_NE(-1, fd);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	map1 = (void *)syscall(sysno,
+		NULL, page_size, PROT_READ, MAP_PRIVATE, fd, page_size);
+	EXPECT_NE(MAP_FAILED, map1);
+	/* mmap2() should never return. */
+	map2 = (void *)syscall(sysno,
+		 NULL, page_size, PROT_READ, MAP_PRIVATE, fd, 0x0C0FFEE);
+	EXPECT_EQ(MAP_FAILED, map2);
+
+	/* The test failed, so clean up the resources. */
+	munmap(map1, page_size);
+	munmap(map2, page_size);
+	close(fd);
+}
+
+/* This is a thread task to die via seccomp filter violation. */
+void *kill_thread(void *data)
+{
+	bool die = (bool)data;
+
+	if (die) {
+		prctl(PR_GET_SECCOMP, 0, 0, 0, 0);
+		return (void *)SIBLING_EXIT_FAILURE;
+	}
+
+	return (void *)SIBLING_EXIT_UNKILLED;
+}
+
+/* Prepare a thread that will kill itself or both of us. */
+void kill_thread_or_group(struct __test_metadata *_metadata, bool kill_process)
+{
+	pthread_t thread;
+	void *status;
+	/* Kill only when calling __NR_prctl. */
+	struct sock_filter filter_thread[] = {
+		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_KILL_THREAD),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog_thread = {
+		.len = (unsigned short)ARRAY_SIZE(filter_thread),
+		.filter = filter_thread,
+	};
+	struct sock_filter filter_process[] = {
+		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_KILL_PROCESS),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog_process = {
+		.len = (unsigned short)ARRAY_SIZE(filter_process),
+		.filter = filter_process,
+	};
+
+	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
+	}
+
+	ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0,
+			     kill_process ? &prog_process : &prog_thread));
+
+	/*
+	 * Add the KILL_THREAD rule again to make sure that the KILL_PROCESS
+	 * flag cannot be downgraded by a new filter.
+	 */
+	ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog_thread));
+
+	/* Start a thread that will exit immediately. */
+	ASSERT_EQ(0, pthread_create(&thread, NULL, kill_thread, (void *)false));
+	ASSERT_EQ(0, pthread_join(thread, &status));
+	ASSERT_EQ(SIBLING_EXIT_UNKILLED, (unsigned long)status);
+
+	/* Start a thread that will die immediately. */
+	ASSERT_EQ(0, pthread_create(&thread, NULL, kill_thread, (void *)true));
+	ASSERT_EQ(0, pthread_join(thread, &status));
+	ASSERT_NE(SIBLING_EXIT_FAILURE, (unsigned long)status);
+
+	/*
+	 * If we get here, only the spawned thread died. Let the parent know
+	 * the whole process didn't die (i.e. this thread, the spawner,
+	 * stayed running).
+	 */
+	exit(42);
+}
+
+TEST(KILL_thread)
+{
+	int status;
+	pid_t child_pid;
+
+	child_pid = fork();
+	ASSERT_LE(0, child_pid);
+	if (child_pid == 0) {
+		kill_thread_or_group(_metadata, false);
+		_exit(38);
+	}
+
+	ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0));
+
+	/* If only the thread was killed, we'll see exit 42. */
+	ASSERT_TRUE(WIFEXITED(status));
+	ASSERT_EQ(42, WEXITSTATUS(status));
+}
+
+TEST(KILL_process)
+{
+	int status;
+	pid_t child_pid;
+
+	child_pid = fork();
+	ASSERT_LE(0, child_pid);
+	if (child_pid == 0) {
+		kill_thread_or_group(_metadata, true);
+		_exit(38);
+	}
+
+	ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0));
+
+	/* If the entire process was killed, we'll see SIGSYS. */
+	ASSERT_TRUE(WIFSIGNALED(status));
+	ASSERT_EQ(SIGSYS, WTERMSIG(status));
+}
+
+/* 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);
+}
+
+#define ERRNO_FILTER(name, errno)					\
+	struct sock_filter _read_filter_##name[] = {			\
+		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 | errno),	\
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),		\
+	};								\
+	struct sock_fprog prog_##name = {				\
+		.len = (unsigned short)ARRAY_SIZE(_read_filter_##name),	\
+		.filter = _read_filter_##name,				\
+	}
+
+/* Make sure basic errno values are correctly passed through a filter. */
+TEST(ERRNO_valid)
+{
+	ERRNO_FILTER(valid, E2BIG);
+	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_valid);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	EXPECT_EQ(-1, read(0, NULL, 0));
+	EXPECT_EQ(E2BIG, errno);
+}
+
+/* Make sure an errno of zero is correctly handled by the arch code. */
+TEST(ERRNO_zero)
+{
+	ERRNO_FILTER(zero, 0);
+	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_zero);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* "errno" of 0 is ok. */
+	EXPECT_EQ(0, read(0, NULL, 0));
+}
+
+/*
+ * The SECCOMP_RET_DATA mask is 16 bits wide, but errno is smaller.
+ * This tests that the errno value gets capped correctly, fixed by
+ * 580c57f10768 ("seccomp: cap SECCOMP_RET_ERRNO data to MAX_ERRNO").
+ */
+TEST(ERRNO_capped)
+{
+	ERRNO_FILTER(capped, 4096);
+	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_capped);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	EXPECT_EQ(-1, read(0, NULL, 0));
+	EXPECT_EQ(4095, errno);
+}
+
+/*
+ * Filters are processed in reverse order: last applied is executed first.
+ * Since only the SECCOMP_RET_ACTION mask is tested for return values, the
+ * SECCOMP_RET_DATA mask results will follow the most recently applied
+ * matching filter return (and not the lowest or highest value).
+ */
+TEST(ERRNO_order)
+{
+	ERRNO_FILTER(first,  11);
+	ERRNO_FILTER(second, 13);
+	ERRNO_FILTER(third,  12);
+	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_first);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog_second);
+	ASSERT_EQ(0, ret);
+
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog_third);
+	ASSERT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	EXPECT_EQ(-1, read(0, NULL, 0));
+	EXPECT_EQ(12, 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 siginfo_t 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 log;
+	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 log_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_LOG),
+	};
+	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(log);
+	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(log);
+	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->log);
+	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->log);
+	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->log);
+	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->log);
+	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->log);
+	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->log);
+	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->log);
+	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->log);
+	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);
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log);
+	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, log_is_fifth)
+{
+	pid_t mypid, parent;
+	long ret;
+
+	mypid = getpid();
+	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->log);
+	ASSERT_EQ(0, ret);
+	/* Should work just fine. */
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* Should also work just fine */
+	EXPECT_EQ(mypid, syscall(__NR_getpid));
+}
+
+TEST_F(precedence, log_is_fifth_in_any_order)
+{
+	pid_t mypid, parent;
+	long ret;
+
+	mypid = getpid();
+	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->log);
+	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));
+	/* Should also work just fine */
+	EXPECT_EQ(mypid, 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 start_tracer(struct __test_metadata *_metadata, int fd, pid_t tracee,
+	    tracer_func_t tracer_func, void *args, bool ptrace_syscall)
+{
+	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_syscall ?
+						      PTRACE_O_TRACESYSGOOD :
+						      PTRACE_O_TRACESECCOMP);
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Failed to set PTRACE_O_TRACESECCOMP");
+		kill(tracee, SIGKILL);
+	}
+	ret = ptrace(ptrace_syscall ? PTRACE_SYSCALL : PTRACE_CONT,
+		     tracee, NULL, 0);
+	ASSERT_EQ(0, ret);
+
+	/* 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;
+
+		/* Check if this is a seccomp event. */
+		ASSERT_EQ(!ptrace_syscall, IS_SECCOMP_EVENT(status));
+
+		tracer_func(_metadata, tracee, status, args);
+
+		ret = ptrace(ptrace_syscall ? PTRACE_SYSCALL : PTRACE_CONT,
+			     tracee, NULL, 0);
+		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, bool ptrace_syscall)
+{
+	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]);
+		start_tracer(_metadata, pipefd[1], tracee, func, args,
+			     ptrace_syscall);
+		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, false);
+}
+
+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]
+#elif defined(__hppa__)
+# define ARCH_REGS	struct user_regs_struct
+# define SYSCALL_NUM	gr[20]
+# define SYSCALL_RET	gr[28]
+#elif defined(__powerpc__)
+# define ARCH_REGS	struct pt_regs
+# define SYSCALL_NUM	gpr[0]
+# define SYSCALL_RET	gpr[3]
+#elif defined(__s390__)
+# define ARCH_REGS     s390_regs
+# define SYSCALL_NUM   gprs[2]
+# define SYSCALL_RET   gprs[2]
+#elif defined(__mips__)
+# define ARCH_REGS	struct pt_regs
+# define SYSCALL_NUM	regs[2]
+# define SYSCALL_SYSCALL_NUM regs[4]
+# define SYSCALL_RET	regs[2]
+# define SYSCALL_NUM_RET_SHARE_REG
+#else
+# error "Do not know how to find your architecture's registers and syscalls"
+#endif
+
+/* When the syscall return can't be changed, stub out the tests for it. */
+#ifdef SYSCALL_NUM_RET_SHARE_REG
+# define EXPECT_SYSCALL_RETURN(val, action)	EXPECT_EQ(-1, action)
+#else
+# define EXPECT_SYSCALL_RETURN(val, action)		\
+	do {						\
+		errno = 0;				\
+		if (val < 0) {				\
+			EXPECT_EQ(-1, action);		\
+			EXPECT_EQ(-(val), errno);	\
+		} else {				\
+			EXPECT_EQ(val, action);		\
+		}					\
+	} while (0)
+#endif
+
+/* Use PTRACE_GETREGS and PTRACE_SETREGS when available. This is useful for
+ * architectures without HAVE_ARCH_TRACEHOOK (e.g. User-mode Linux).
+ */
+#if defined(__x86_64__) || defined(__i386__) || defined(__mips__)
+#define HAVE_GETREGS
+#endif
+
+/* Architecture-specific syscall fetching routine. */
+int get_syscall(struct __test_metadata *_metadata, pid_t tracee)
+{
+	ARCH_REGS regs;
+#ifdef HAVE_GETREGS
+	EXPECT_EQ(0, ptrace(PTRACE_GETREGS, tracee, 0, &regs)) {
+		TH_LOG("PTRACE_GETREGS failed");
+		return -1;
+	}
+#else
+	struct iovec iov;
+
+	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;
+	}
+#endif
+
+#if defined(__mips__)
+	if (regs.SYSCALL_NUM == __NR_O32_Linux)
+		return regs.SYSCALL_SYSCALL_NUM;
+#endif
+	return regs.SYSCALL_NUM;
+}
+
+/* Architecture-specific syscall changing routine. */
+void change_syscall(struct __test_metadata *_metadata,
+		    pid_t tracee, int syscall, int result)
+{
+	int ret;
+	ARCH_REGS regs;
+#ifdef HAVE_GETREGS
+	ret = ptrace(PTRACE_GETREGS, tracee, 0, &regs);
+#else
+	struct iovec iov;
+	iov.iov_base = &regs;
+	iov.iov_len = sizeof(regs);
+	ret = ptrace(PTRACE_GETREGSET, tracee, NT_PRSTATUS, &iov);
+#endif
+	EXPECT_EQ(0, ret) {}
+
+#if defined(__x86_64__) || defined(__i386__) || defined(__powerpc__) || \
+    defined(__s390__) || defined(__hppa__)
+	{
+		regs.SYSCALL_NUM = syscall;
+	}
+#elif defined(__mips__)
+	{
+		if (regs.SYSCALL_NUM == __NR_O32_Linux)
+			regs.SYSCALL_SYSCALL_NUM = syscall;
+		else
+			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);
+	}
+
+#elif defined(__aarch64__)
+# ifndef NT_ARM_SYSTEM_CALL
+#  define NT_ARM_SYSTEM_CALL 0x404
+# endif
+	{
+		iov.iov_base = &syscall;
+		iov.iov_len = sizeof(syscall);
+		ret = ptrace(PTRACE_SETREGSET, tracee, NT_ARM_SYSTEM_CALL,
+			     &iov);
+		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)
+#ifdef SYSCALL_NUM_RET_SHARE_REG
+		TH_LOG("Can't modify syscall return on this architecture");
+#else
+		regs.SYSCALL_RET = result;
+#endif
+
+#ifdef HAVE_GETREGS
+	ret = ptrace(PTRACE_SETREGS, tracee, 0, &regs);
+#else
+	iov.iov_base = &regs;
+	iov.iov_len = sizeof(regs);
+	ret = ptrace(PTRACE_SETREGSET, tracee, NT_PRSTATUS, &iov);
+#endif
+	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);
+
+	/* Validate and take action on expected syscalls. */
+	switch (msg) {
+	case 0x1002:
+		/* change getpid to getppid. */
+		EXPECT_EQ(__NR_getpid, get_syscall(_metadata, tracee));
+		change_syscall(_metadata, tracee, __NR_getppid, 0);
+		break;
+	case 0x1003:
+		/* skip gettid with valid return code. */
+		EXPECT_EQ(__NR_gettid, get_syscall(_metadata, tracee));
+		change_syscall(_metadata, tracee, -1, 45000);
+		break;
+	case 0x1004:
+		/* skip openat with error. */
+		EXPECT_EQ(__NR_openat, get_syscall(_metadata, tracee));
+		change_syscall(_metadata, tracee, -1, -ESRCH);
+		break;
+	case 0x1005:
+		/* do nothing (allow getppid) */
+		EXPECT_EQ(__NR_getppid, get_syscall(_metadata, tracee));
+		break;
+	default:
+		EXPECT_EQ(0, msg) {
+			TH_LOG("Unknown PTRACE_GETEVENTMSG: 0x%lx", msg);
+			kill(tracee, SIGKILL);
+		}
+	}
+
+}
+
+void tracer_ptrace(struct __test_metadata *_metadata, pid_t tracee,
+		   int status, void *args)
+{
+	int ret, nr;
+	unsigned long msg;
+	static bool entry;
+
+	/* Make sure we got an empty message. */
+	ret = ptrace(PTRACE_GETEVENTMSG, tracee, NULL, &msg);
+	EXPECT_EQ(0, ret);
+	EXPECT_EQ(0, msg);
+
+	/* The only way to tell PTRACE_SYSCALL entry/exit is by counting. */
+	entry = !entry;
+	if (!entry)
+		return;
+
+	nr = get_syscall(_metadata, tracee);
+
+	if (nr == __NR_getpid)
+		change_syscall(_metadata, tracee, __NR_getppid, 0);
+	if (nr == __NR_gettid)
+		change_syscall(_metadata, tracee, -1, 45000);
+	if (nr == __NR_openat)
+		change_syscall(_metadata, tracee, -1, -ESRCH);
+}
+
+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_openat, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1004),
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getppid, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1005),
+		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,
+					   false);
+}
+
+FIXTURE_TEARDOWN(TRACE_syscall)
+{
+	teardown_trace_fixture(_metadata, self->tracer);
+	if (self->prog.filter)
+		free(self->prog.filter);
+}
+
+TEST_F(TRACE_syscall, ptrace_syscall_redirected)
+{
+	/* Swap SECCOMP_RET_TRACE tracer for PTRACE_SYSCALL tracer. */
+	teardown_trace_fixture(_metadata, self->tracer);
+	self->tracer = setup_trace_fixture(_metadata, tracer_ptrace, NULL,
+					   true);
+
+	/* Tracer will redirect getpid to getppid. */
+	EXPECT_NE(self->mypid, syscall(__NR_getpid));
+}
+
+TEST_F(TRACE_syscall, ptrace_syscall_errno)
+{
+	/* Swap SECCOMP_RET_TRACE tracer for PTRACE_SYSCALL tracer. */
+	teardown_trace_fixture(_metadata, self->tracer);
+	self->tracer = setup_trace_fixture(_metadata, tracer_ptrace, NULL,
+					   true);
+
+	/* Tracer should skip the open syscall, resulting in ESRCH. */
+	EXPECT_SYSCALL_RETURN(-ESRCH, syscall(__NR_openat));
+}
+
+TEST_F(TRACE_syscall, ptrace_syscall_faked)
+{
+	/* Swap SECCOMP_RET_TRACE tracer for PTRACE_SYSCALL tracer. */
+	teardown_trace_fixture(_metadata, self->tracer);
+	self->tracer = setup_trace_fixture(_metadata, tracer_ptrace, NULL,
+					   true);
+
+	/* Tracer should skip the gettid syscall, resulting fake pid. */
+	EXPECT_SYSCALL_RETURN(45000, syscall(__NR_gettid));
+}
+
+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_errno)
+{
+	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);
+
+	/* openat has been skipped and an errno return. */
+	EXPECT_SYSCALL_RETURN(-ESRCH, syscall(__NR_openat));
+}
+
+TEST_F(TRACE_syscall, syscall_faked)
+{
+	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_SYSCALL_RETURN(45000, syscall(__NR_gettid));
+}
+
+TEST_F(TRACE_syscall, skip_after_RET_TRACE)
+{
+	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_getppid, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | EPERM),
+		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);
+
+	/* Install fixture filter. */
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Install "errno on getppid" filter. */
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Tracer will redirect getpid to getppid, and we should see EPERM. */
+	errno = 0;
+	EXPECT_EQ(-1, syscall(__NR_getpid));
+	EXPECT_EQ(EPERM, errno);
+}
+
+TEST_F_SIGNAL(TRACE_syscall, kill_after_RET_TRACE, 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_getppid, 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;
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Install fixture filter. */
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Install "death on getppid" filter. */
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Tracer will redirect getpid to getppid, and we should die. */
+	EXPECT_NE(self->mypid, syscall(__NR_getpid));
+}
+
+TEST_F(TRACE_syscall, skip_after_ptrace)
+{
+	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_getppid, 0, 1),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | EPERM),
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	long ret;
+
+	/* Swap SECCOMP_RET_TRACE tracer for PTRACE_SYSCALL tracer. */
+	teardown_trace_fixture(_metadata, self->tracer);
+	self->tracer = setup_trace_fixture(_metadata, tracer_ptrace, NULL,
+					   true);
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Install "errno on getppid" filter. */
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Tracer will redirect getpid to getppid, and we should see EPERM. */
+	EXPECT_EQ(-1, syscall(__NR_getpid));
+	EXPECT_EQ(EPERM, errno);
+}
+
+TEST_F_SIGNAL(TRACE_syscall, kill_after_ptrace, 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_getppid, 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;
+
+	/* Swap SECCOMP_RET_TRACE tracer for PTRACE_SYSCALL tracer. */
+	teardown_trace_fixture(_metadata, self->tracer);
+	self->tracer = setup_trace_fixture(_metadata, tracer_ptrace, NULL,
+					   true);
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Install "death on getppid" filter. */
+	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Tracer will redirect getpid to getppid, and we should die. */
+	EXPECT_NE(self->mypid, syscall(__NR_getpid));
+}
+
+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);
+	ASSERT_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	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);
+	ASSERT_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	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 detection of known and unknown filter flags. Userspace needs to be able
+ * to check if a filter flag is supported by the current kernel and a good way
+ * of doing that is by attempting to enter filter mode, with the flag bit in
+ * question set, and a NULL pointer for the _args_ parameter. EFAULT indicates
+ * that the flag is valid and EINVAL indicates that the flag is invalid.
+ */
+TEST(detect_seccomp_filter_flags)
+{
+	unsigned int flags[] = { SECCOMP_FILTER_FLAG_TSYNC,
+				 SECCOMP_FILTER_FLAG_LOG,
+				 SECCOMP_FILTER_FLAG_SPEC_ALLOW };
+	unsigned int flag, all_flags;
+	int i;
+	long ret;
+
+	/* Test detection of known-good filter flags */
+	for (i = 0, all_flags = 0; i < ARRAY_SIZE(flags); i++) {
+		int bits = 0;
+
+		flag = flags[i];
+		/* Make sure the flag is a single bit! */
+		while (flag) {
+			if (flag & 0x1)
+				bits ++;
+			flag >>= 1;
+		}
+		ASSERT_EQ(1, bits);
+		flag = flags[i];
+
+		ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL);
+		ASSERT_NE(ENOSYS, errno) {
+			TH_LOG("Kernel does not support seccomp syscall!");
+		}
+		EXPECT_EQ(-1, ret);
+		EXPECT_EQ(EFAULT, errno) {
+			TH_LOG("Failed to detect that a known-good filter flag (0x%X) is supported!",
+			       flag);
+		}
+
+		all_flags |= flag;
+	}
+
+	/* Test detection of all known-good filter flags */
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, all_flags, NULL);
+	EXPECT_EQ(-1, ret);
+	EXPECT_EQ(EFAULT, errno) {
+		TH_LOG("Failed to detect that all known-good filter flags (0x%X) are supported!",
+		       all_flags);
+	}
+
+	/* Test detection of an unknown filter flag */
+	flag = -1;
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL);
+	EXPECT_EQ(-1, ret);
+	EXPECT_EQ(EINVAL, errno) {
+		TH_LOG("Failed to detect that an unknown filter flag (0x%X) is unsupported!",
+		       flag);
+	}
+
+	/*
+	 * Test detection of an unknown filter flag that may simply need to be
+	 * added to this test
+	 */
+	flag = flags[ARRAY_SIZE(flags) - 1] << 1;
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL);
+	EXPECT_EQ(-1, ret);
+	EXPECT_EQ(EINVAL, errno) {
+		TH_LOG("Failed to detect that an unknown filter flag (0x%X) is unsupported! Does a new flag need to be added to this test?",
+		       flag);
+	}
+}
+
+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_FILTER_FLAG_TSYNC,
+		      &prog);
+	ASSERT_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	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;
+};
+
+/*
+ * To avoid joining joined threads (which is not allowed by Bionic),
+ * make sure we both successfully join and clear the tid to skip a
+ * later join attempt during fixture teardown. Any remaining threads
+ * will be directly killed during teardown.
+ */
+#define PTHREAD_JOIN(tid, status)					\
+	do {								\
+		int _rc = pthread_join(tid, status);			\
+		if (_rc) {						\
+			TH_LOG("pthread_join of tid %u failed: %d\n",	\
+				(unsigned int)tid, _rc);		\
+		} else {						\
+			tid = 0;					\
+		}							\
+	} while (0)
+
+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];
+
+		if (!s->tid)
+			continue;
+		/*
+		 * If a thread is still running, it may be stuck, so hit
+		 * it over the head really hard.
+		 */
+		pthread_kill(s->tid, 9);
+	}
+	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_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	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_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	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_FILTER_FLAG_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_FILTER_FLAG_TSYNC,
+		      &self->apply_prog);
+	ASSERT_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	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_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	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_FILTER_FLAG_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_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	ASSERT_EQ(0, ret) {
+		TH_LOG("Kernel does not support SECCOMP_SET_MODE_FILTER!");
+	}
+
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_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_FILTER_FLAG_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_FILTER_FLAG_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_nanosleep, 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),
+		/* The nanosleep jump target. */
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE|0x100),
+		/* The restart_syscall jump target. */
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE|0x200),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+#if defined(__arm__)
+	struct utsname utsbuf;
+#endif
+
+	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 timespec timeout = { };
+
+		/* 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 nanosleep to be interrupted. */
+		timeout.tv_sec = 1;
+		errno = 0;
+		EXPECT_EQ(0, nanosleep(&timeout, NULL)) {
+			TH_LOG("Call to nanosleep() 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 nanosleep() 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_nanosleep, 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 nanosleep 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 nanosleep 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:
+	 * - native ARM registers do NOT expose true syscall.
+	 * - compat ARM registers on ARM64 DO expose true syscall.
+	 */
+	ASSERT_EQ(0, uname(&utsbuf));
+	if (strncmp(utsbuf.machine, "arm", 3) == 0) {
+		EXPECT_EQ(__NR_nanosleep, ret);
+	} else
+#endif
+	{
+		EXPECT_EQ(__NR_restart_syscall, ret);
+	}
+
+	/* Write again to end test. */
+	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;
+}
+
+TEST_SIGNAL(filter_flag_log, SIGSYS)
+{
+	struct sock_filter allow_filter[] = {
+		BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_filter kill_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 allow_prog = {
+		.len = (unsigned short)ARRAY_SIZE(allow_filter),
+		.filter = allow_filter,
+	};
+	struct sock_fprog kill_prog = {
+		.len = (unsigned short)ARRAY_SIZE(kill_filter),
+		.filter = kill_filter,
+	};
+	long ret;
+	pid_t parent = getppid();
+
+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	ASSERT_EQ(0, ret);
+
+	/* Verify that the FILTER_FLAG_LOG flag isn't accepted in strict mode */
+	ret = seccomp(SECCOMP_SET_MODE_STRICT, SECCOMP_FILTER_FLAG_LOG,
+		      &allow_prog);
+	ASSERT_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	EXPECT_NE(0, ret) {
+		TH_LOG("Kernel accepted FILTER_FLAG_LOG flag in strict mode!");
+	}
+	EXPECT_EQ(EINVAL, errno) {
+		TH_LOG("Kernel returned unexpected errno for FILTER_FLAG_LOG flag in strict mode!");
+	}
+
+	/* Verify that a simple, permissive filter can be added with no flags */
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &allow_prog);
+	EXPECT_EQ(0, ret);
+
+	/* See if the same filter can be added with the FILTER_FLAG_LOG flag */
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_LOG,
+		      &allow_prog);
+	ASSERT_NE(EINVAL, errno) {
+		TH_LOG("Kernel does not support the FILTER_FLAG_LOG flag!");
+	}
+	EXPECT_EQ(0, ret);
+
+	/* Ensure that the kill filter works with the FILTER_FLAG_LOG flag */
+	ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_LOG,
+		      &kill_prog);
+	EXPECT_EQ(0, ret);
+
+	EXPECT_EQ(parent, syscall(__NR_getppid));
+	/* getpid() should never return. */
+	EXPECT_EQ(0, syscall(__NR_getpid));
+}
+
+TEST(get_action_avail)
+{
+	__u32 actions[] = { SECCOMP_RET_KILL_THREAD, SECCOMP_RET_TRAP,
+			    SECCOMP_RET_ERRNO, SECCOMP_RET_TRACE,
+			    SECCOMP_RET_LOG,   SECCOMP_RET_ALLOW };
+	__u32 unknown_action = 0x10000000U;
+	int i;
+	long ret;
+
+	ret = seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &actions[0]);
+	ASSERT_NE(ENOSYS, errno) {
+		TH_LOG("Kernel does not support seccomp syscall!");
+	}
+	ASSERT_NE(EINVAL, errno) {
+		TH_LOG("Kernel does not support SECCOMP_GET_ACTION_AVAIL operation!");
+	}
+	EXPECT_EQ(ret, 0);
+
+	for (i = 0; i < ARRAY_SIZE(actions); i++) {
+		ret = seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &actions[i]);
+		EXPECT_EQ(ret, 0) {
+			TH_LOG("Expected action (0x%X) not available!",
+			       actions[i]);
+		}
+	}
+
+	/* Check that an unknown action is handled properly (EOPNOTSUPP) */
+	ret = seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &unknown_action);
+	EXPECT_EQ(ret, -1);
+	EXPECT_EQ(errno, EOPNOTSUPP);
+}
+
+TEST(get_metadata)
+{
+	pid_t pid;
+	int pipefd[2];
+	char buf;
+	struct seccomp_metadata md;
+	long ret;
+
+	/* Only real root can get metadata. */
+	if (geteuid()) {
+		XFAIL(return, "get_metadata requires real root");
+		return;
+	}
+
+	ASSERT_EQ(0, pipe(pipefd));
+
+	pid = fork();
+	ASSERT_GE(pid, 0);
+	if (pid == 0) {
+		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,
+		};
+
+		/* one with log, one without */
+		ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER,
+				     SECCOMP_FILTER_FLAG_LOG, &prog));
+		ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog));
+
+		ASSERT_EQ(0, close(pipefd[0]));
+		ASSERT_EQ(1, write(pipefd[1], "1", 1));
+		ASSERT_EQ(0, close(pipefd[1]));
+
+		while (1)
+			sleep(100);
+	}
+
+	ASSERT_EQ(0, close(pipefd[1]));
+	ASSERT_EQ(1, read(pipefd[0], &buf, 1));
+
+	ASSERT_EQ(0, ptrace(PTRACE_ATTACH, pid));
+	ASSERT_EQ(pid, waitpid(pid, NULL, 0));
+
+	/* Past here must not use ASSERT or child process is never killed. */
+
+	md.filter_off = 0;
+	errno = 0;
+	ret = ptrace(PTRACE_SECCOMP_GET_METADATA, pid, sizeof(md), &md);
+	EXPECT_EQ(sizeof(md), ret) {
+		if (errno == EINVAL)
+			XFAIL(goto skip, "Kernel does not support PTRACE_SECCOMP_GET_METADATA (missing CONFIG_CHECKPOINT_RESTORE?)");
+	}
+
+	EXPECT_EQ(md.flags, SECCOMP_FILTER_FLAG_LOG);
+	EXPECT_EQ(md.filter_off, 0);
+
+	md.filter_off = 1;
+	ret = ptrace(PTRACE_SECCOMP_GET_METADATA, pid, sizeof(md), &md);
+	EXPECT_EQ(sizeof(md), ret);
+	EXPECT_EQ(md.flags, 0);
+	EXPECT_EQ(md.filter_off, 1);
+
+skip:
+	ASSERT_EQ(0, kill(pid, SIGKILL));
+}
+
+/*
+ * 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)
+ * - verify that FILTER_FLAG_LOG filters generate log messages
+ * - verify that RET_LOG generates log messages
+ * - ...
+ */
+
+TEST_HARNESS_MAIN