1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
|
/*
* entry_from_vm86.c - tests kernel entries from vm86 mode
* Copyright (c) 2014-2015 Andrew Lutomirski
*
* This exercises a few paths that need to special-case vm86 mode.
*
* GPL v2.
*/
#define _GNU_SOURCE
#include <assert.h>
#include <stdlib.h>
#include <sys/syscall.h>
#include <sys/signal.h>
#include <sys/ucontext.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <sys/mman.h>
#include <err.h>
#include <stddef.h>
#include <stdbool.h>
#include <errno.h>
#include <sys/vm86.h>
static unsigned long load_addr = 0x10000;
static int nerrs = 0;
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
int flags)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = handler;
sa.sa_flags = SA_SIGINFO | flags;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
static void clearhandler(int sig)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = SIG_DFL;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
static sig_atomic_t got_signal;
static void sighandler(int sig, siginfo_t *info, void *ctx_void)
{
ucontext_t *ctx = (ucontext_t*)ctx_void;
if (ctx->uc_mcontext.gregs[REG_EFL] & X86_EFLAGS_VM ||
(ctx->uc_mcontext.gregs[REG_CS] & 3) != 3) {
printf("[FAIL]\tSignal frame should not reflect vm86 mode\n");
nerrs++;
}
const char *signame;
if (sig == SIGSEGV)
signame = "SIGSEGV";
else if (sig == SIGILL)
signame = "SIGILL";
else
signame = "unexpected signal";
printf("[INFO]\t%s: FLAGS = 0x%lx, CS = 0x%hx\n", signame,
(unsigned long)ctx->uc_mcontext.gregs[REG_EFL],
(unsigned short)ctx->uc_mcontext.gregs[REG_CS]);
got_signal = 1;
}
asm (
".pushsection .rodata\n\t"
".type vmcode_bound, @object\n\t"
"vmcode:\n\t"
"vmcode_bound:\n\t"
".code16\n\t"
"bound %ax, (2048)\n\t"
"int3\n\t"
"vmcode_sysenter:\n\t"
"sysenter\n\t"
"vmcode_syscall:\n\t"
"syscall\n\t"
"vmcode_sti:\n\t"
"sti\n\t"
"vmcode_int3:\n\t"
"int3\n\t"
"vmcode_int80:\n\t"
"int $0x80\n\t"
".size vmcode, . - vmcode\n\t"
"end_vmcode:\n\t"
".code32\n\t"
".popsection"
);
extern unsigned char vmcode[], end_vmcode[];
extern unsigned char vmcode_bound[], vmcode_sysenter[], vmcode_syscall[],
vmcode_sti[], vmcode_int3[], vmcode_int80[];
/* Returns false if the test was skipped. */
static bool do_test(struct vm86plus_struct *v86, unsigned long eip,
unsigned int rettype, unsigned int retarg,
const char *text)
{
long ret;
printf("[RUN]\t%s from vm86 mode\n", text);
v86->regs.eip = eip;
ret = vm86(VM86_ENTER, v86);
if (ret == -1 && (errno == ENOSYS || errno == EPERM)) {
printf("[SKIP]\tvm86 %s\n",
errno == ENOSYS ? "not supported" : "not allowed");
return false;
}
if (VM86_TYPE(ret) == VM86_INTx) {
char trapname[32];
int trapno = VM86_ARG(ret);
if (trapno == 13)
strcpy(trapname, "GP");
else if (trapno == 5)
strcpy(trapname, "BR");
else if (trapno == 14)
strcpy(trapname, "PF");
else
sprintf(trapname, "%d", trapno);
printf("[INFO]\tExited vm86 mode due to #%s\n", trapname);
} else if (VM86_TYPE(ret) == VM86_UNKNOWN) {
printf("[INFO]\tExited vm86 mode due to unhandled GP fault\n");
} else if (VM86_TYPE(ret) == VM86_TRAP) {
printf("[INFO]\tExited vm86 mode due to a trap (arg=%ld)\n",
VM86_ARG(ret));
} else if (VM86_TYPE(ret) == VM86_SIGNAL) {
printf("[INFO]\tExited vm86 mode due to a signal\n");
} else if (VM86_TYPE(ret) == VM86_STI) {
printf("[INFO]\tExited vm86 mode due to STI\n");
} else {
printf("[INFO]\tExited vm86 mode due to type %ld, arg %ld\n",
VM86_TYPE(ret), VM86_ARG(ret));
}
if (rettype == -1 ||
(VM86_TYPE(ret) == rettype && VM86_ARG(ret) == retarg)) {
printf("[OK]\tReturned correctly\n");
} else {
printf("[FAIL]\tIncorrect return reason\n");
nerrs++;
}
return true;
}
int main(void)
{
struct vm86plus_struct v86;
unsigned char *addr = mmap((void *)load_addr, 4096,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_ANONYMOUS | MAP_PRIVATE, -1,0);
if (addr != (unsigned char *)load_addr)
err(1, "mmap");
memcpy(addr, vmcode, end_vmcode - vmcode);
addr[2048] = 2;
addr[2050] = 3;
memset(&v86, 0, sizeof(v86));
v86.regs.cs = load_addr / 16;
v86.regs.ss = load_addr / 16;
v86.regs.ds = load_addr / 16;
v86.regs.es = load_addr / 16;
assert((v86.regs.cs & 3) == 0); /* Looks like RPL = 0 */
/* #BR -- should deliver SIG??? */
do_test(&v86, vmcode_bound - vmcode, VM86_INTx, 5, "#BR");
/*
* SYSENTER -- should cause #GP or #UD depending on CPU.
* Expected return type -1 means that we shouldn't validate
* the vm86 return value. This will avoid problems on non-SEP
* CPUs.
*/
sethandler(SIGILL, sighandler, 0);
do_test(&v86, vmcode_sysenter - vmcode, -1, 0, "SYSENTER");
clearhandler(SIGILL);
/*
* SYSCALL would be a disaster in VM86 mode. Fortunately,
* there is no kernel that both enables SYSCALL and sets
* EFER.SCE, so it's #UD on all systems. But vm86 is
* buggy (or has a "feature"), so the SIGILL will actually
* be delivered.
*/
sethandler(SIGILL, sighandler, 0);
do_test(&v86, vmcode_syscall - vmcode, VM86_SIGNAL, 0, "SYSCALL");
clearhandler(SIGILL);
/* STI with VIP set */
v86.regs.eflags |= X86_EFLAGS_VIP;
v86.regs.eflags &= ~X86_EFLAGS_IF;
do_test(&v86, vmcode_sti - vmcode, VM86_STI, 0, "STI with VIP set");
/* INT3 -- should cause #BP */
do_test(&v86, vmcode_int3 - vmcode, VM86_TRAP, 3, "INT3");
/* INT80 -- should exit with "INTx 0x80" */
v86.regs.eax = (unsigned int)-1;
do_test(&v86, vmcode_int80 - vmcode, VM86_INTx, 0x80, "int80");
/* Execute a null pointer */
v86.regs.cs = 0;
v86.regs.ss = 0;
sethandler(SIGSEGV, sighandler, 0);
got_signal = 0;
if (do_test(&v86, 0, VM86_SIGNAL, 0, "Execute null pointer") &&
!got_signal) {
printf("[FAIL]\tDid not receive SIGSEGV\n");
nerrs++;
}
clearhandler(SIGSEGV);
return (nerrs == 0 ? 0 : 1);
}
|
