1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * syscall_arg_fault.c - tests faults 32-bit fast syscall stack args
4  * Copyright (c) 2018 Andrew Lutomirski
5  */
6 
7 #define _GNU_SOURCE
8 
9 #include <stdlib.h>
10 #include <stdio.h>
11 #include <stdbool.h>
12 #include <errno.h>
13 #include <unistd.h>
14 #include <syscall.h>
15 
16 static int nerrs;
17 
18 #define X32_BIT 0x40000000UL
19 
20 static void check_enosys(unsigned long nr, bool *ok)
21 {
22 	/* If this fails, a segfault is reasonably likely. */
23 	fflush(stdout);
24 
25 	long ret = syscall(nr, 0, 0, 0, 0, 0, 0);
26 	if (ret == 0) {
27 		printf("[FAIL]\tsyscall %lu succeeded, but it should have failed\n", nr);
28 		*ok = false;
29 	} else if (errno != ENOSYS) {
30 		printf("[FAIL]\tsyscall %lu had error code %d, but it should have reported ENOSYS\n", nr, errno);
31 		*ok = false;
32 	}
33 }
34 
35 static void test_x32_without_x32_bit(void)
36 {
37 	bool ok = true;
38 
39 	/*
40 	 * Syscalls 512-547 are "x32" syscalls.  They are intended to be
41 	 * called with the x32 (0x40000000) bit set.  Calling them without
42 	 * the x32 bit set is nonsense and should not work.
43 	 */
44 	printf("[RUN]\tChecking syscalls 512-547\n");
45 	for (int i = 512; i <= 547; i++)
46 		check_enosys(i, &ok);
47 
48 	/*
49 	 * Check that a handful of 64-bit-only syscalls are rejected if the x32
50 	 * bit is set.
51 	 */
52 	printf("[RUN]\tChecking some 64-bit syscalls in x32 range\n");
53 	check_enosys(16 | X32_BIT, &ok);	/* ioctl */
54 	check_enosys(19 | X32_BIT, &ok);	/* readv */
55 	check_enosys(20 | X32_BIT, &ok);	/* writev */
56 
57 	/*
58 	 * Check some syscalls with high bits set.
59 	 */
60 	printf("[RUN]\tChecking numbers above 2^32-1\n");
61 	check_enosys((1UL << 32), &ok);
62 	check_enosys(X32_BIT | (1UL << 32), &ok);
63 
64 	if (!ok)
65 		nerrs++;
66 	else
67 		printf("[OK]\tThey all returned -ENOSYS\n");
68 }
69 
70 int main()
71 {
72 	/*
73 	 * Anyone diagnosing a failure will want to know whether the kernel
74 	 * supports x32.  Tell them.
75 	 */
76 	printf("\tChecking for x32...");
77 	fflush(stdout);
78 	if (syscall(39 | X32_BIT, 0, 0, 0, 0, 0, 0) >= 0) {
79 		printf(" supported\n");
80 	} else if (errno == ENOSYS) {
81 		printf(" not supported\n");
82 	} else {
83 		printf(" confused\n");
84 	}
85 
86 	test_x32_without_x32_bit();
87 
88 	return nerrs ? 1 : 0;
89 }
90