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
check_enosys(unsigned long nr,bool * ok)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
test_x32_without_x32_bit(void)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
main()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