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Date: Thu, 16 Jul 2020 15:31:41 -0400
From: Gabriel Krisman Bertazi <krisman@...labora.com>
To: tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org, kernel@...labora.com,
willy@...radead.org, luto@...nel.org, gofmanp@...il.com,
keescook@...omium.org, linux-kselftest@...r.kernel.org,
shuah@...nel.org, Gabriel Krisman Bertazi <krisman@...labora.com>
Subject: [PATCH v4 2/2] selftests: Add kselftest for syscall user dispatch
Implement functionality tests for syscall user dispatch. In order to
make the test portable, refrain from open coding syscall dispatchers and
calculating glibc memory ranges.
changes since v3:
- Sort entry in Makefile
- Add SPDX header
- Use __NR_syscalls if available
Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
---
tools/testing/selftests/Makefile | 1 +
.../syscall_user_dispatch/.gitignore | 2 +
.../selftests/syscall_user_dispatch/Makefile | 9 +
.../selftests/syscall_user_dispatch/config | 1 +
.../syscall_user_dispatch.c | 256 ++++++++++++++++++
5 files changed, 269 insertions(+)
create mode 100644 tools/testing/selftests/syscall_user_dispatch/.gitignore
create mode 100644 tools/testing/selftests/syscall_user_dispatch/Makefile
create mode 100644 tools/testing/selftests/syscall_user_dispatch/config
create mode 100644 tools/testing/selftests/syscall_user_dispatch/syscall_user_dispatch.c
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 1195bd85af38..07a3c682f1e4 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -53,6 +53,7 @@ TARGETS += sparc64
TARGETS += splice
TARGETS += static_keys
TARGETS += sync
+TARGETS += syscall_user_dispatch
TARGETS += sysctl
TARGETS += timens
ifneq (1, $(quicktest))
diff --git a/tools/testing/selftests/syscall_user_dispatch/.gitignore b/tools/testing/selftests/syscall_user_dispatch/.gitignore
new file mode 100644
index 000000000000..637f08107add
--- /dev/null
+++ b/tools/testing/selftests/syscall_user_dispatch/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+syscall_user_dispatch
diff --git a/tools/testing/selftests/syscall_user_dispatch/Makefile b/tools/testing/selftests/syscall_user_dispatch/Makefile
new file mode 100644
index 000000000000..eeb07a791057
--- /dev/null
+++ b/tools/testing/selftests/syscall_user_dispatch/Makefile
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0
+top_srcdir = ../../../..
+INSTALL_HDR_PATH = $(top_srcdir)/usr
+LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/
+
+CFLAGS += -Wall -I$(LINUX_HDR_PATH)
+
+TEST_GEN_PROGS := syscall_user_dispatch
+include ../lib.mk
diff --git a/tools/testing/selftests/syscall_user_dispatch/config b/tools/testing/selftests/syscall_user_dispatch/config
new file mode 100644
index 000000000000..22c4dfe167ca
--- /dev/null
+++ b/tools/testing/selftests/syscall_user_dispatch/config
@@ -0,0 +1 @@
+CONFIG_SYSCALL_USER_DISPATCH=y
diff --git a/tools/testing/selftests/syscall_user_dispatch/syscall_user_dispatch.c b/tools/testing/selftests/syscall_user_dispatch/syscall_user_dispatch.c
new file mode 100644
index 000000000000..ed783fc447a2
--- /dev/null
+++ b/tools/testing/selftests/syscall_user_dispatch/syscall_user_dispatch.c
@@ -0,0 +1,256 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2020 Collabora Ltd.
+ *
+ * Test code for syscall user dispatch
+ */
+
+#define _GNU_SOURCE
+#include <sys/prctl.h>
+#include <sys/sysinfo.h>
+#include <sys/syscall.h>
+#include <signal.h>
+
+#include <asm/unistd.h>
+#include "../kselftest_harness.h"
+
+#ifndef PR_SET_SYSCALL_USER_DISPATCH
+# define PR_SET_SYSCALL_USER_DISPATCH 59
+# define PR_SYS_DISPATCH_OFF 0
+# define PR_SYS_DISPATCH_ON 1
+#endif
+
+#ifndef SYS_USER_DISPATCH
+# define SYS_USER_DISPATCH 2
+#endif
+
+#ifdef __NR_syscalls
+# define MAGIC_SYSCALL_1 (__NR_syscalls + 1) /* Bad Linux syscall number */
+#else
+# define MAGIC_SYSCALL_1 (0xff00) /* Bad Linux syscall number */
+#endif
+
+#define SYSCALL_DISPATCH_ON(x) ((x) = 1)
+#define SYSCALL_DISPATCH_OFF(x) ((x) = 0)
+
+/* Test Summary:
+ *
+ * - dispatch_trigger_sigsys: Verify if PR_SET_SYSCALL_USER_DISPATCH is
+ * able to trigger SIGSYS on a syscall.
+ *
+ * - bad_selector: Test that a bad selector value triggers SIGSEGV.
+ *
+ * - bad_prctl_param: Test that the API correctly rejects invalid
+ * parameters on prctl
+ *
+ * - dispatch_and_return: Test that a syscall is selectively dispatched
+ * to userspace depending on the value of selector.
+ *
+ * - disable_dispatch: Test that the PR_SYS_DISPATCH_OFF correctly
+ * disables the dispatcher
+ *
+ * - direct_dispatch_range: Test that a syscall within the allowed range
+ * can bypass the dispatcher.
+ */
+
+TEST_SIGNAL(dispatch_trigger_sigsys, SIGSYS)
+{
+ char sel = 0;
+ struct sysinfo info;
+ int ret;
+
+ ret = sysinfo(&info);
+ ASSERT_EQ(0, ret);
+
+ ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &sel);
+ ASSERT_EQ(0, ret) {
+ TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
+ }
+
+ SYSCALL_DISPATCH_ON(sel);
+
+ sysinfo(&info);
+
+ EXPECT_FALSE(true) {
+ TH_LOG("Unreachable!");
+ }
+}
+
+TEST_SIGNAL(bad_selector, SIGSEGV)
+{
+ char sel = -1;
+ long ret;
+
+ ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &sel);
+ ASSERT_EQ(0, ret) {
+ TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
+ }
+ EXPECT_FALSE(true) {
+ TH_LOG("Unreachable!");
+ }
+}
+
+TEST(bad_prctl_param)
+{
+ char sel = 0;
+ int op;
+
+ /* Invalid op */
+ op = -1;
+ prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0, 0, &sel);
+ ASSERT_EQ(EINVAL, errno);
+
+ /* PR_SYS_DISPATCH_OFF */
+ op = PR_SYS_DISPATCH_OFF;
+
+ /* start_addr != 0 */
+ prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x1, 0xff, 0);
+ EXPECT_EQ(EINVAL, errno);
+
+ /* end_addr != 0 */
+ prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0xff, 0);
+ EXPECT_EQ(EINVAL, errno);
+
+ /* sel != NULL */
+ prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x0, &sel);
+ EXPECT_EQ(EINVAL, errno);
+
+ /* Valid parameter */
+ errno = 0;
+ prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x0, 0x0);
+ EXPECT_EQ(0, errno);
+
+ /* PR_SYS_DISPATCH_ON */
+ op = PR_SYS_DISPATCH_ON;
+
+ /* start_addr > end_addr */
+ prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x1, 0x0, &sel);
+ EXPECT_EQ(EINVAL, errno);
+
+ /* Invalid selector */
+ prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x1, (void *) -1);
+ ASSERT_EQ(EFAULT, errno);
+}
+
+/*
+ * Use global selector for handle_sigsys tests, to avoid passing
+ * selector to signal handler
+ */
+char glob_sel;
+int nr_syscalls_emulated;
+int si_code;
+
+static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)
+{
+ si_code = info->si_code;
+
+ if (info->si_syscall == MAGIC_SYSCALL_1)
+ nr_syscalls_emulated++;
+
+ /* In preparation for sigreturn. */
+ SYSCALL_DISPATCH_OFF(glob_sel);
+}
+
+TEST(dispatch_and_return)
+{
+ long ret;
+ struct sigaction act;
+ sigset_t mask;
+
+ glob_sel = 0;
+ nr_syscalls_emulated = 0;
+ si_code = 0;
+
+ memset(&act, 0, sizeof(act));
+ sigemptyset(&mask);
+
+ act.sa_sigaction = handle_sigsys;
+ act.sa_flags = SA_SIGINFO;
+ act.sa_mask = mask;
+
+ ret = sigaction(SIGSYS, &act, NULL);
+ ASSERT_EQ(0, ret);
+
+ /* Make sure selector is good prior to prctl. */
+ SYSCALL_DISPATCH_OFF(glob_sel);
+
+ ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &glob_sel);
+ ASSERT_EQ(0, ret) {
+ TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
+ }
+
+ /* MAGIC_SYSCALL_1 doesn't exist. */
+ SYSCALL_DISPATCH_OFF(glob_sel);
+ ret = syscall(MAGIC_SYSCALL_1);
+ EXPECT_EQ(-1, ret) {
+ TH_LOG("Dispatch triggered unexpectedly");
+ }
+
+ /* MAGIC_SYSCALL_1 should be emulated. */
+ nr_syscalls_emulated = 0;
+ SYSCALL_DISPATCH_ON(glob_sel);
+
+ ret = syscall(MAGIC_SYSCALL_1);
+ EXPECT_EQ(MAGIC_SYSCALL_1, ret) {
+ TH_LOG("Failed to intercept syscall");
+ }
+ EXPECT_EQ(1, nr_syscalls_emulated) {
+ TH_LOG("Failed to emulate syscall");
+ }
+ ASSERT_EQ(SYS_USER_DISPATCH, si_code) {
+ TH_LOG("Bad si_code in SIGSYS");
+ }
+}
+
+TEST(disable_dispatch)
+{
+ int ret;
+ struct sysinfo info;
+ char sel = 0;
+
+ ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &sel);
+ ASSERT_EQ(0, ret) {
+ TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
+ }
+
+ /* MAGIC_SYSCALL_1 doesn't exist. */
+ SYSCALL_DISPATCH_OFF(glob_sel);
+
+ ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_OFF, 0, 0, 0);
+ EXPECT_EQ(0, ret) {
+ TH_LOG("Failed to unset syscall user dispatch");
+ }
+
+ /* Shouldn't have any effect... */
+ SYSCALL_DISPATCH_ON(glob_sel);
+
+ ret = syscall(__NR_sysinfo, &info);
+ EXPECT_EQ(0, ret) {
+ TH_LOG("Dispatch triggered unexpectedly");
+ }
+}
+
+TEST(direct_dispatch_range)
+{
+ int ret = 0;
+ struct sysinfo info;
+ char sel = 0;
+
+ /*
+ * Instead of calculating libc addresses; allow the entire
+ * memory map and lock the selector.
+ */
+ ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, -1L, &sel);
+ ASSERT_EQ(0, ret) {
+ TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");
+ }
+
+ SYSCALL_DISPATCH_ON(sel);
+
+ ret = sysinfo(&info);
+ ASSERT_EQ(0, ret) {
+ TH_LOG("Dispatch triggered unexpectedly");
+ }
+}
+
+TEST_HARNESS_MAIN
--
2.27.0
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