1 /* $OpenBSD: f00f.c,v 1.2 2018/05/21 23:34:20 bluhm Exp $ */
2 /*
3 * Copyright (c) 2018 Alexander Bluhm <bluhm@genua.de>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 /* Test the Pentium f00f bug workaround by executing 0xF0,0x0F,0xC7,0xC8. */
19
20 #include <err.h>
21 #include <signal.h>
22 #include <stdint.h>
23 #include <stdio.h>
24 #include <stdlib.h>
25 #include <string.h>
26
27 void
handler(int sig,siginfo_t * sip,void * ctx)28 handler(int sig, siginfo_t *sip, void *ctx)
29 {
30 printf("signo %d, code %d, errno %d\n",
31 sip->si_signo, sip->si_code, sip->si_errno);
32 if (sig != SIGILL)
33 errx(1, "expected SIGILL: %d", sig);
34 printf("addr %p, trapno %d\n", sip->si_addr, sip->si_trapno);
35 printf("instruction %.2x %.2x %.2x %.2x\n",
36 ((uint8_t *)sip->si_addr)[0],
37 ((uint8_t *)sip->si_addr)[1],
38 ((uint8_t *)sip->si_addr)[2],
39 ((uint8_t *)sip->si_addr)[3]);
40 if (*((uint32_t *)sip->si_addr) != 0xc8c70ff0)
41 errx(1, "expected instrcution f0 0f c7 c8");
42
43 exit(0);
44 }
45
46 int
main(int argc,char * argv[])47 main(int argc, char *argv[])
48 {
49 struct sigaction sa;
50 uint64_t mem;
51 uint32_t eax, ebx, ecx, edx;
52
53 mem = 0x0123456789abcdefLL;
54 eax = 0x11111111;
55 ebx = 0x22222222;
56 ecx = 0x33333333;
57 edx = 0x44444444;
58
59 /* First check that the cmpxchg8b instruction works as expected. */
60 printf("mem %.16llx, edx:eax %.8x%8x, ecx:ebx %.8x%.8x\n",
61 mem, edx, eax, ecx, ebx);
62 printf("cmpxchg8b mem, mem != edx:eax\n");
63 asm volatile (
64 "lock cmpxchg8b %0"
65 : "+m" (mem), "+a" (eax), "+b" (ebx), "+c" (ecx), "+d" (edx));
66 printf("mem %.16llx, edx:eax %.8x%8x, ecx:ebx %.8x%.8x\n",
67 mem, edx, eax, ecx, ebx);
68
69 if (mem != 0x0123456789abcdefLL)
70 errx(1, "expected mem 0x0123456789abcdef");
71 if (edx != 0x01234567 || eax != 0x89abcdef)
72 errx(1, "expected edx:eax 0x0123456789abcdef");
73 if (ecx != 0x33333333 || ebx != 0x22222222)
74 errx(1, "expected ecx:ebx 0x3333333322222222");
75
76 printf("cmpxchg8b mem, mem == edx:eax\n");
77 asm volatile (
78 "lock cmpxchg8b %0"
79 : "+m" (mem), "+a" (eax), "+b" (ebx), "+c" (ecx), "+d" (edx));
80 printf("mem %.16llx, edx:eax %.8x%8x, ecx:ebx %.8x%.8x\n",
81 mem, edx, eax, ecx, ebx);
82
83 if (mem != 0x3333333322222222LL)
84 errx(1, "expected mem 0x3333333322222222");
85 if (edx != 0x01234567 || eax != 0x89abcdef)
86 errx(1, "expected edx:eax 0x0123456789abcdef");
87 if (ecx != 0x33333333 || ebx != 0x22222222)
88 errx(1, "expected ecx:ebx 0x3333333322222222");
89
90 /* An illegal instruction must be signalled to user land. */
91 memset(&sa, 0 ,sizeof(sa));
92 sa.sa_sigaction = handler;
93 sa.sa_flags = SA_SIGINFO;
94 if (sigaction(SIGILL, &sa, NULL) == -1)
95 err(2, "sigaction");
96
97 /* Execute the cmpxchg8b instruction with invalid addressing mode. */
98 printf("cmpxchg8b eax\n");
99 asm volatile (
100 ".byte 0xF0,0x0F,0xC7,0xC8"
101 : : : "%eax", "%ebx", "%ecx", "%edx");
102 printf("mem %.16llx, edx:eax %.8x%8x, ecx:ebx %.8x%.8x\n",
103 mem, edx, eax, ecx, ebx);
104
105 /* Not reached, the processor hangs or the signal handler exits. */
106 errx(1, "expected signal");
107 }
108