// 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 <stdbool.h>
#include <stdlib.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 SYSCALL_DISPATCH_FILTER_ALLOW  0
# define SYSCALL_DISPATCH_FILTER_BLOCK  1
#endif

#ifndef PR_SYS_DISPATCH_EXCLUSIVE_ON
# define PR_SYS_DISPATCH_EXCLUSIVE_ON   1
# define PR_SYS_DISPATCH_INCLUSIVE_ON   2
#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_EXCLUSIVE_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!");
        }
}

static void prctl_valid(struct __test_metadata *_metadata,
                        unsigned long op, unsigned long off,
                        unsigned long size, void *sel)
{
        EXPECT_EQ(0, prctl(PR_SET_SYSCALL_USER_DISPATCH, op, off, size, sel));
}

static void prctl_invalid(struct __test_metadata *_metadata,
                          unsigned long op, unsigned long off,
                          unsigned long size, void *sel, int err)
{
        EXPECT_EQ(-1, prctl(PR_SET_SYSCALL_USER_DISPATCH, op, off, size, sel));
        EXPECT_EQ(err, errno);
}

TEST(bad_prctl_param)
{
        char sel = SYSCALL_DISPATCH_FILTER_ALLOW;
        int op;

        /* Invalid op */
        op = -1;
        prctl_invalid(_metadata, op, 0, 0, &sel, EINVAL);

        /* PR_SYS_DISPATCH_OFF */
        op = PR_SYS_DISPATCH_OFF;

        /* offset != 0 */
        prctl_invalid(_metadata, op, 0x1, 0x0, 0, EINVAL);

        /* len != 0 */
        prctl_invalid(_metadata, op, 0x0, 0xff, 0, EINVAL);

        /* sel != NULL */
        prctl_invalid(_metadata, op, 0x0, 0x0, &sel, EINVAL);

        /* Valid parameter */
        prctl_valid(_metadata, op, 0x0, 0x0, 0x0);

        /* PR_SYS_DISPATCH_EXCLUSIVE_ON */
        op = PR_SYS_DISPATCH_EXCLUSIVE_ON;

        /* Dispatcher region is bad (offset > 0 && len == 0) */
        prctl_invalid(_metadata, op, 0x1, 0x0, &sel, EINVAL);
        prctl_invalid(_metadata, op, -1L, 0x0, &sel, EINVAL);

        /* Invalid selector */
        prctl_invalid(_metadata, op, 0x0, 0x1, (void *) -1, EFAULT);

        /*
         * Dispatcher range overflows unsigned long
         */
        prctl_invalid(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, 1, -1L, &sel, EINVAL);

        /*
         * Allowed range overflows usigned long
         */
        prctl_invalid(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, -1L, 0x1, &sel, EINVAL);

        /* 0 len should fail for PR_SYS_DISPATCH_INCLUSIVE_ON */
        prctl_invalid(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, 1, 0, 0, EINVAL);

        /* Range wrap-around should fail */
        prctl_invalid(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, -1L, 2, 0, EINVAL);

        /* Normal range shouldn't fail */
        prctl_valid(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, 2, 3, 0);

        /* Invalid selector */
        prctl_invalid(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, 2, 3, (void *) -1, EFAULT);
}

/*
 * 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;
unsigned long syscall_addr;

static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)
{
        si_code = info->si_code;
        si_errno = info->si_errno;
        syscall_addr = (unsigned long)info->si_call_addr;

        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
}

int setup_sigsys_handler(void)
{
        struct sigaction act;
        sigset_t mask;

        memset(&act, 0, sizeof(act));
        sigemptyset(&mask);
        act.sa_sigaction = handle_sigsys;
        act.sa_flags = SA_SIGINFO;
        act.sa_mask = mask;
        return sigaction(SIGSYS, &act, NULL);
}

TEST(dispatch_and_return)
{
        long ret;

        glob_sel = 0;
        nr_syscalls_emulated = 0;
        si_code = 0;
        si_errno = 0;

        ASSERT_EQ(0, setup_sigsys_handler());

        /* Make sure selector is good prior to prctl. */
        SYSCALL_DISPATCH_OFF(glob_sel);

        ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_EXCLUSIVE_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_EXCLUSIVE_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_EXCLUSIVE_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_EXCLUSIVE_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");
        }
}

static void test_range(struct __test_metadata *_metadata,
                       unsigned long op, unsigned long off,
                       unsigned long size, bool dispatch)
{
        nr_syscalls_emulated = 0;
        SYSCALL_DISPATCH_OFF(glob_sel);
        EXPECT_EQ(0, prctl(PR_SET_SYSCALL_USER_DISPATCH, op, off, size, &glob_sel));
        SYSCALL_DISPATCH_ON(glob_sel);
        if (dispatch) {
                EXPECT_EQ(syscall(MAGIC_SYSCALL_1), MAGIC_SYSCALL_1);
                EXPECT_EQ(nr_syscalls_emulated, 1);
        } else {
                EXPECT_EQ(syscall(MAGIC_SYSCALL_1), -1);
                EXPECT_EQ(nr_syscalls_emulated, 0);
        }
}

TEST(dispatch_range)
{
        ASSERT_EQ(0, setup_sigsys_handler());
        test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, 0, 0, true);
        test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, syscall_addr, 1, false);
        test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, syscall_addr-100, 200, false);
        test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, syscall_addr+1, 100, true);
        test_range(_metadata, PR_SYS_DISPATCH_EXCLUSIVE_ON, syscall_addr-100, 100, true);
        test_range(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, syscall_addr, 1, true);
        test_range(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, syscall_addr-1, 1, false);
        test_range(_metadata, PR_SYS_DISPATCH_INCLUSIVE_ON, syscall_addr+1, 1, false);
        SYSCALL_DISPATCH_OFF(glob_sel);
}

TEST_HARNESS_MAIN