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
235
236
237
238
|
/* Linux-specific ptrace manipulation routines.
Copyright (C) 2012-2013 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifdef GDBSERVER
#include "server.h"
#else
#include "defs.h"
#include "gdb_string.h"
#endif
#include "linux-ptrace.h"
#include "linux-procfs.h"
#include "buffer.h"
#include "gdb_assert.h"
#include "gdb_wait.h"
/* Find all possible reasons we could fail to attach PID and append these
newline terminated reason strings to initialized BUFFER. '\0' termination
of BUFFER must be done by the caller. */
void
linux_ptrace_attach_warnings (pid_t pid, struct buffer *buffer)
{
pid_t tracerpid;
tracerpid = linux_proc_get_tracerpid (pid);
if (tracerpid > 0)
buffer_xml_printf (buffer, _("warning: process %d is already traced "
"by process %d\n"),
(int) pid, (int) tracerpid);
if (linux_proc_pid_is_zombie (pid))
buffer_xml_printf (buffer, _("warning: process %d is a zombie "
"- the process has already terminated\n"),
(int) pid);
}
#if defined __i386__ || defined __x86_64__
/* Address of the 'ret' instruction in asm code block below. */
extern void (linux_ptrace_test_ret_to_nx_instr) (void);
#include <sys/reg.h>
#include <sys/mman.h>
#include <signal.h>
#include <stdint.h>
#endif /* defined __i386__ || defined __x86_64__ */
/* Test broken off-trunk Linux kernel patchset for NX support on i386. It was
removed in Fedora kernel 88fa1f0332d188795ed73d7ac2b1564e11a0b4cd.
Test also x86_64 arch for PaX support. */
static void
linux_ptrace_test_ret_to_nx (void)
{
#if defined __i386__ || defined __x86_64__
pid_t child, got_pid;
gdb_byte *return_address, *pc;
long l;
int status, kill_status;
return_address = mmap (NULL, 2, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (return_address == MAP_FAILED)
{
warning (_("linux_ptrace_test_ret_to_nx: Cannot mmap: %s"),
strerror (errno));
return;
}
/* Put there 'int3'. */
*return_address = 0xcc;
child = fork ();
switch (child)
{
case -1:
warning (_("linux_ptrace_test_ret_to_nx: Cannot fork: %s"),
strerror (errno));
return;
case 0:
l = ptrace (PTRACE_TRACEME, 0, NULL, NULL);
if (l != 0)
warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_TRACEME: %s"),
strerror (errno));
else
{
#if defined __i386__
asm volatile ("pushl %0;"
".globl linux_ptrace_test_ret_to_nx_instr;"
"linux_ptrace_test_ret_to_nx_instr:"
"ret"
: : "r" (return_address) : "%esp", "memory");
#elif defined __x86_64__
asm volatile ("pushq %0;"
".globl linux_ptrace_test_ret_to_nx_instr;"
"linux_ptrace_test_ret_to_nx_instr:"
"ret"
: : "r" ((uint64_t) (uintptr_t) return_address)
: "%rsp", "memory");
#else
# error "!__i386__ && !__x86_64__"
#endif
gdb_assert_not_reached ("asm block did not terminate");
}
_exit (1);
}
errno = 0;
got_pid = waitpid (child, &status, 0);
if (got_pid != child)
{
warning (_("linux_ptrace_test_ret_to_nx: waitpid returned %ld: %s"),
(long) got_pid, strerror (errno));
return;
}
if (WIFSIGNALED (status))
{
if (WTERMSIG (status) != SIGKILL)
warning (_("linux_ptrace_test_ret_to_nx: WTERMSIG %d is not SIGKILL!"),
(int) WTERMSIG (status));
else
warning (_("Cannot call inferior functions, Linux kernel PaX "
"protection forbids return to non-executable pages!"));
return;
}
if (!WIFSTOPPED (status))
{
warning (_("linux_ptrace_test_ret_to_nx: status %d is not WIFSTOPPED!"),
status);
return;
}
/* We may get SIGSEGV due to missing PROT_EXEC of the return_address. */
if (WSTOPSIG (status) != SIGTRAP && WSTOPSIG (status) != SIGSEGV)
{
warning (_("linux_ptrace_test_ret_to_nx: "
"WSTOPSIG %d is neither SIGTRAP nor SIGSEGV!"),
(int) WSTOPSIG (status));
return;
}
errno = 0;
#if defined __i386__
l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (EIP * 4), NULL);
#elif defined __x86_64__
l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (RIP * 8), NULL);
#else
# error "!__i386__ && !__x86_64__"
#endif
if (errno != 0)
{
warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_PEEKUSER: %s"),
strerror (errno));
return;
}
pc = (void *) (uintptr_t) l;
kill (child, SIGKILL);
ptrace (PTRACE_KILL, child, NULL, NULL);
errno = 0;
got_pid = waitpid (child, &kill_status, 0);
if (got_pid != child)
{
warning (_("linux_ptrace_test_ret_to_nx: "
"PTRACE_KILL waitpid returned %ld: %s"),
(long) got_pid, strerror (errno));
return;
}
if (!WIFSIGNALED (kill_status))
{
warning (_("linux_ptrace_test_ret_to_nx: "
"PTRACE_KILL status %d is not WIFSIGNALED!"),
status);
return;
}
/* + 1 is there as x86* stops after the 'int3' instruction. */
if (WSTOPSIG (status) == SIGTRAP && pc == return_address + 1)
{
/* PASS */
return;
}
/* We may get SIGSEGV due to missing PROT_EXEC of the RETURN_ADDRESS page. */
if (WSTOPSIG (status) == SIGSEGV && pc == return_address)
{
/* PASS */
return;
}
if ((void (*) (void)) pc != &linux_ptrace_test_ret_to_nx_instr)
warning (_("linux_ptrace_test_ret_to_nx: PC %p is neither near return "
"address %p nor is the return instruction %p!"),
pc, return_address, &linux_ptrace_test_ret_to_nx_instr);
else
warning (_("Cannot call inferior functions on this system - "
"Linux kernel with broken i386 NX (non-executable pages) "
"support detected!"));
#endif /* defined __i386__ || defined __x86_64__ */
}
/* Display possible problems on this system. Display them only once per GDB
execution. */
void
linux_ptrace_init_warnings (void)
{
static int warned = 0;
if (warned)
return;
warned = 1;
linux_ptrace_test_ret_to_nx ();
}
|
