// 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
# define SYSCALL_DISPATCH_FILTER_ALLOW 0
# define SYSCALL_DISPATCH_FILTER_BLOCK 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) = SYSCALL_DISPATCH_FILTER_BLOCK)
#define SYSCALL_DISPATCH_OFF(x) ((x) = SYSCALL_DISPATCH_FILTER_ALLOW)
/* 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 SIGSYS with
* si_errno EINVAL.
*
* - 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 = SYSCALL_DISPATCH_FILTER_ALLOW;
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(bad_prctl_param)
{
char sel = SYSCALL_DISPATCH_FILTER_ALLOW;
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;
/* offset != 0 */
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x1, 0x0, 0);
EXPECT_EQ(EINVAL, errno);
/* len != 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;
/* Dispatcher region is bad (offset > 0 && len == 0) */
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x1, 0x0, &sel);
EXPECT_EQ(EINVAL, errno);
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, -1L, 0x0, &sel);
EXPECT_EQ(EINVAL, errno);
/* Invalid selector */
prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x1, (void *) -1);
ASSERT_EQ(EFAULT, errno);
/*
* Dispatcher range overflows unsigned long
*/
prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 1, -1L, &sel);
ASSERT_EQ(EINVAL, errno) {
TH_LOG("Should reject bad syscall range");
}
/*
* Allowed range overflows usigned long
*/
prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, -1L, 0x1, &sel);
ASSERT_EQ(EINVAL, errno) {
TH_LOG("Should reject bad syscall range");
}
}
/*
* Use global selector for handle_sigsys tests, to avoid passing
* selector to signal handler
*/
char glob_sel;
int nr_syscalls_emulated;
int si_code;
int si_errno;
static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)
{
si_code = info->si_code;
si_errno = info->si_errno;
if (info->si_syscall == MAGIC_SYSCALL_1)
nr_syscalls_emulated++;
/* In preparation for sigreturn. */
SYSCALL_DISPATCH_OFF(glob_sel);
/*
* The tests for argument handling assume that `syscall(x) == x`. This
* is a NOP on x86 because the syscall number is passed in %rax, which
* happens to also be the function ABI return register. Other
* architectures may need to swizzle the arguments around.
*/
#if defined(__riscv)
/* REG_A7 is not defined in libc headers */
# define REG_A7 (REG_A0 + 7)
((ucontext_t *)ucontext)->uc_mcontext.__gregs[REG_A0] =
((ucontext_t *)ucontext)->uc_mcontext.__gregs[REG_A7];
#endif
}
TEST(dispatch_and_return)
{
long ret;
struct sigaction act;
sigset_t mask;
glob_sel = 0;
nr_syscalls_emulated = 0;
si_code = 0;
si_errno = 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");
}
ASSERT_EQ(0, si_errno) {
TH_LOG("Bad si_errno in SIGSYS");
}
}
TEST_SIGNAL(bad_selector, SIGSYS)
{
long ret;
struct sigaction act;
sigset_t mask;
struct sysinfo info;
glob_sel = SYSCALL_DISPATCH_FILTER_ALLOW;
nr_syscalls_emulated = 0;
si_code = 0;
si_errno = 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");
}
glob_sel = -1;
sysinfo(&info);
/* Even though it is ready to catch SIGSYS, the signal is
* supposed to be uncatchable.
*/
EXPECT_FALSE(true) {
TH_LOG("Unreachable!");
}
}
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 = SYSCALL_DISPATCH_FILTER_ALLOW;
/*
* 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
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