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
|
/* Linux-specific ptrace manipulation routines.
Copyright (C) 2012 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"
/* 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);
}
#ifdef __i386__
/* 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 <sys/wait.h>
#include <stdint.h>
#endif /* __i386__ */
/* Test broken off-trunk Linux kernel patchset for NX support on i386. It was
removed in Fedora kernel 88fa1f0332d188795ed73d7ac2b1564e11a0b4cd. */
static void
linux_ptrace_test_ret_to_nx (void)
{
#ifdef __i386__
pid_t child, got_pid;
gdb_byte *return_address, *pc;
long l;
int 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
{
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");
gdb_assert_not_reached ("asm block did not terminate");
}
_exit (1);
}
got_pid = waitpid (child, &status, 0);
gdb_assert (got_pid == child);
gdb_assert (WIFSTOPPED (status));
/* We may get SIGSEGV due to missing PROT_EXEC of the return_address. */
gdb_assert (WSTOPSIG (status) == SIGTRAP || WSTOPSIG (status) == SIGSEGV);
errno = 0;
l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (EIP * 4), NULL);
gdb_assert (errno == 0);
pc = (void *) (uintptr_t) l;
if (ptrace (PTRACE_KILL, child, NULL, NULL) != 0)
warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_KILL: %s"),
strerror (errno));
else
{
int kill_status;
got_pid = waitpid (child, &kill_status, 0);
gdb_assert (got_pid == child);
gdb_assert (WIFSIGNALED (kill_status));
}
/* + 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;
}
gdb_assert ((void (*) (void)) pc == &linux_ptrace_test_ret_to_nx_instr);
warning (_("Cannot call inferior functions, you have broken "
"Linux kernel i386 NX (non-executable pages) support!"));
#endif /* __i386__ */
}
/* 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 ();
}
|
