1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * iopl.c - Test case for a Linux on Xen 64-bit bug
4 * Copyright (c) 2015 Andrew Lutomirski
5 */
6
7 #define _GNU_SOURCE
8 #include <err.h>
9 #include <stdio.h>
10 #include <stdint.h>
11 #include <signal.h>
12 #include <setjmp.h>
13 #include <stdlib.h>
14 #include <string.h>
15 #include <errno.h>
16 #include <unistd.h>
17 #include <sys/types.h>
18 #include <sys/wait.h>
19 #include <stdbool.h>
20 #include <sched.h>
21 #include <sys/io.h>
22
23 static int nerrs = 0;
24
sethandler(int sig,void (* handler)(int,siginfo_t *,void *),int flags)25 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
26 int flags)
27 {
28 struct sigaction sa;
29 memset(&sa, 0, sizeof(sa));
30 sa.sa_sigaction = handler;
31 sa.sa_flags = SA_SIGINFO | flags;
32 sigemptyset(&sa.sa_mask);
33 if (sigaction(sig, &sa, 0))
34 err(1, "sigaction");
35
36 }
37
38 static jmp_buf jmpbuf;
39
sigsegv(int sig,siginfo_t * si,void * ctx_void)40 static void sigsegv(int sig, siginfo_t *si, void *ctx_void)
41 {
42 siglongjmp(jmpbuf, 1);
43 }
44
main(void)45 int main(void)
46 {
47 cpu_set_t cpuset;
48 CPU_ZERO(&cpuset);
49 CPU_SET(0, &cpuset);
50 if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
51 err(1, "sched_setaffinity to CPU 0");
52
53 /* Probe for iopl support. Note that iopl(0) works even as nonroot. */
54 if (iopl(3) != 0) {
55 printf("[OK]\tiopl(3) failed (%d) -- try running as root\n",
56 errno);
57 return 0;
58 }
59
60 /* Restore our original state prior to starting the test. */
61 if (iopl(0) != 0)
62 err(1, "iopl(0)");
63
64 pid_t child = fork();
65 if (child == -1)
66 err(1, "fork");
67
68 if (child == 0) {
69 printf("\tchild: set IOPL to 3\n");
70 if (iopl(3) != 0)
71 err(1, "iopl");
72
73 printf("[RUN]\tchild: write to 0x80\n");
74 asm volatile ("outb %%al, $0x80" : : "a" (0));
75
76 return 0;
77 } else {
78 int status;
79 if (waitpid(child, &status, 0) != child ||
80 !WIFEXITED(status)) {
81 printf("[FAIL]\tChild died\n");
82 nerrs++;
83 } else if (WEXITSTATUS(status) != 0) {
84 printf("[FAIL]\tChild failed\n");
85 nerrs++;
86 } else {
87 printf("[OK]\tChild succeeded\n");
88 }
89 }
90
91 printf("[RUN]\tparent: write to 0x80 (should fail)\n");
92
93 sethandler(SIGSEGV, sigsegv, 0);
94 if (sigsetjmp(jmpbuf, 1) != 0) {
95 printf("[OK]\twrite was denied\n");
96 } else {
97 asm volatile ("outb %%al, $0x80" : : "a" (0));
98 printf("[FAIL]\twrite was allowed\n");
99 nerrs++;
100 }
101
102 /* Test the capability checks. */
103 printf("\tiopl(3)\n");
104 if (iopl(3) != 0)
105 err(1, "iopl(3)");
106
107 printf("\tDrop privileges\n");
108 if (setresuid(1, 1, 1) != 0) {
109 printf("[WARN]\tDropping privileges failed\n");
110 goto done;
111 }
112
113 printf("[RUN]\tiopl(3) unprivileged but with IOPL==3\n");
114 if (iopl(3) != 0) {
115 printf("[FAIL]\tiopl(3) should work if iopl is already 3 even if unprivileged\n");
116 nerrs++;
117 }
118
119 printf("[RUN]\tiopl(0) unprivileged\n");
120 if (iopl(0) != 0) {
121 printf("[FAIL]\tiopl(0) should work if iopl is already 3 even if unprivileged\n");
122 nerrs++;
123 }
124
125 printf("[RUN]\tiopl(3) unprivileged\n");
126 if (iopl(3) == 0) {
127 printf("[FAIL]\tiopl(3) should fail if when unprivileged if iopl==0\n");
128 nerrs++;
129 } else {
130 printf("[OK]\tFailed as expected\n");
131 }
132
133 done:
134 return nerrs ? 1 : 0;
135 }
136
137