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5f572dec | 1 | /* Linux-specific ptrace manipulation routines. |
28e7fd62 | 2 | Copyright (C) 2012-2013 Free Software Foundation, Inc. |
5f572dec JK |
3 | |
4 | This file is part of GDB. | |
5 | ||
6 | This program is free software; you can redistribute it and/or modify | |
7 | it under the terms of the GNU General Public License as published by | |
8 | the Free Software Foundation; either version 3 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | This program is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | GNU General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
17 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ | |
18 | ||
19 | #ifdef GDBSERVER | |
20 | #include "server.h" | |
21 | #else | |
22 | #include "defs.h" | |
23 | #include "gdb_string.h" | |
24 | #endif | |
25 | ||
26 | #include "linux-ptrace.h" | |
87b0bb13 JK |
27 | #include "linux-procfs.h" |
28 | #include "buffer.h" | |
aa7c7447 | 29 | #include "gdb_assert.h" |
8bdce1ff | 30 | #include "gdb_wait.h" |
87b0bb13 JK |
31 | |
32 | /* Find all possible reasons we could fail to attach PID and append these | |
33 | newline terminated reason strings to initialized BUFFER. '\0' termination | |
34 | of BUFFER must be done by the caller. */ | |
35 | ||
36 | void | |
37 | linux_ptrace_attach_warnings (pid_t pid, struct buffer *buffer) | |
38 | { | |
39 | pid_t tracerpid; | |
40 | ||
41 | tracerpid = linux_proc_get_tracerpid (pid); | |
42 | if (tracerpid > 0) | |
43 | buffer_xml_printf (buffer, _("warning: process %d is already traced " | |
44 | "by process %d\n"), | |
45 | (int) pid, (int) tracerpid); | |
46 | ||
47 | if (linux_proc_pid_is_zombie (pid)) | |
48 | buffer_xml_printf (buffer, _("warning: process %d is a zombie " | |
49 | "- the process has already terminated\n"), | |
50 | (int) pid); | |
51 | } | |
aa7c7447 | 52 | |
6e3c039e | 53 | #if defined __i386__ || defined __x86_64__ |
aa7c7447 JK |
54 | |
55 | /* Address of the 'ret' instruction in asm code block below. */ | |
56 | extern void (linux_ptrace_test_ret_to_nx_instr) (void); | |
57 | ||
58 | #include <sys/reg.h> | |
59 | #include <sys/mman.h> | |
60 | #include <signal.h> | |
aa7c7447 JK |
61 | #include <stdint.h> |
62 | ||
6e3c039e | 63 | #endif /* defined __i386__ || defined __x86_64__ */ |
aa7c7447 JK |
64 | |
65 | /* Test broken off-trunk Linux kernel patchset for NX support on i386. It was | |
6e3c039e JK |
66 | removed in Fedora kernel 88fa1f0332d188795ed73d7ac2b1564e11a0b4cd. |
67 | ||
68 | Test also x86_64 arch for PaX support. */ | |
aa7c7447 JK |
69 | |
70 | static void | |
71 | linux_ptrace_test_ret_to_nx (void) | |
72 | { | |
6e3c039e | 73 | #if defined __i386__ || defined __x86_64__ |
aa7c7447 JK |
74 | pid_t child, got_pid; |
75 | gdb_byte *return_address, *pc; | |
76 | long l; | |
77 | int status; | |
78 | ||
79 | return_address = mmap (NULL, 2, PROT_READ | PROT_WRITE, | |
80 | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); | |
81 | if (return_address == MAP_FAILED) | |
82 | { | |
83 | warning (_("linux_ptrace_test_ret_to_nx: Cannot mmap: %s"), | |
84 | strerror (errno)); | |
85 | return; | |
86 | } | |
87 | ||
88 | /* Put there 'int3'. */ | |
89 | *return_address = 0xcc; | |
90 | ||
91 | child = fork (); | |
92 | switch (child) | |
93 | { | |
94 | case -1: | |
95 | warning (_("linux_ptrace_test_ret_to_nx: Cannot fork: %s"), | |
96 | strerror (errno)); | |
97 | return; | |
98 | ||
99 | case 0: | |
100 | l = ptrace (PTRACE_TRACEME, 0, NULL, NULL); | |
101 | if (l != 0) | |
102 | warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_TRACEME: %s"), | |
103 | strerror (errno)); | |
104 | else | |
105 | { | |
6e3c039e | 106 | #if defined __i386__ |
aa7c7447 JK |
107 | asm volatile ("pushl %0;" |
108 | ".globl linux_ptrace_test_ret_to_nx_instr;" | |
109 | "linux_ptrace_test_ret_to_nx_instr:" | |
110 | "ret" | |
111 | : : "r" (return_address) : "%esp", "memory"); | |
6e3c039e JK |
112 | #elif defined __x86_64__ |
113 | asm volatile ("pushq %0;" | |
114 | ".globl linux_ptrace_test_ret_to_nx_instr;" | |
115 | "linux_ptrace_test_ret_to_nx_instr:" | |
116 | "ret" | |
bdad4180 MF |
117 | : : "r" ((uint64_t) (uintptr_t) return_address) |
118 | : "%rsp", "memory"); | |
6e3c039e JK |
119 | #else |
120 | # error "!__i386__ && !__x86_64__" | |
121 | #endif | |
aa7c7447 JK |
122 | gdb_assert_not_reached ("asm block did not terminate"); |
123 | } | |
124 | ||
125 | _exit (1); | |
126 | } | |
127 | ||
6e3c039e | 128 | errno = 0; |
aa7c7447 | 129 | got_pid = waitpid (child, &status, 0); |
6e3c039e JK |
130 | if (got_pid != child) |
131 | { | |
132 | warning (_("linux_ptrace_test_ret_to_nx: waitpid returned %ld: %s"), | |
133 | (long) got_pid, strerror (errno)); | |
134 | return; | |
135 | } | |
136 | ||
137 | if (WIFSIGNALED (status)) | |
138 | { | |
139 | if (WTERMSIG (status) != SIGKILL) | |
140 | warning (_("linux_ptrace_test_ret_to_nx: WTERMSIG %d is not SIGKILL!"), | |
141 | (int) WTERMSIG (status)); | |
142 | else | |
143 | warning (_("Cannot call inferior functions, Linux kernel PaX " | |
144 | "protection forbids return to non-executable pages!")); | |
145 | return; | |
146 | } | |
147 | ||
148 | if (!WIFSTOPPED (status)) | |
149 | { | |
150 | warning (_("linux_ptrace_test_ret_to_nx: status %d is not WIFSTOPPED!"), | |
151 | status); | |
152 | return; | |
153 | } | |
aa7c7447 JK |
154 | |
155 | /* We may get SIGSEGV due to missing PROT_EXEC of the return_address. */ | |
6e3c039e JK |
156 | if (WSTOPSIG (status) != SIGTRAP && WSTOPSIG (status) != SIGSEGV) |
157 | { | |
158 | warning (_("linux_ptrace_test_ret_to_nx: " | |
159 | "WSTOPSIG %d is neither SIGTRAP nor SIGSEGV!"), | |
160 | (int) WSTOPSIG (status)); | |
161 | return; | |
162 | } | |
aa7c7447 JK |
163 | |
164 | errno = 0; | |
6e3c039e | 165 | #if defined __i386__ |
aa7c7447 | 166 | l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (EIP * 4), NULL); |
6e3c039e JK |
167 | #elif defined __x86_64__ |
168 | l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (RIP * 8), NULL); | |
169 | #else | |
170 | # error "!__i386__ && !__x86_64__" | |
171 | #endif | |
172 | if (errno != 0) | |
173 | { | |
174 | warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_PEEKUSER: %s"), | |
175 | strerror (errno)); | |
176 | return; | |
177 | } | |
aa7c7447 JK |
178 | pc = (void *) (uintptr_t) l; |
179 | ||
180 | if (ptrace (PTRACE_KILL, child, NULL, NULL) != 0) | |
6e3c039e JK |
181 | { |
182 | warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_KILL: %s"), | |
183 | strerror (errno)); | |
184 | return; | |
185 | } | |
aa7c7447 JK |
186 | else |
187 | { | |
188 | int kill_status; | |
189 | ||
6e3c039e | 190 | errno = 0; |
aa7c7447 | 191 | got_pid = waitpid (child, &kill_status, 0); |
6e3c039e JK |
192 | if (got_pid != child) |
193 | { | |
194 | warning (_("linux_ptrace_test_ret_to_nx: " | |
195 | "PTRACE_KILL waitpid returned %ld: %s"), | |
196 | (long) got_pid, strerror (errno)); | |
197 | return; | |
198 | } | |
199 | if (!WIFSIGNALED (kill_status)) | |
200 | { | |
201 | warning (_("linux_ptrace_test_ret_to_nx: " | |
202 | "PTRACE_KILL status %d is not WIFSIGNALED!"), | |
203 | status); | |
204 | return; | |
205 | } | |
aa7c7447 JK |
206 | } |
207 | ||
208 | /* + 1 is there as x86* stops after the 'int3' instruction. */ | |
209 | if (WSTOPSIG (status) == SIGTRAP && pc == return_address + 1) | |
210 | { | |
211 | /* PASS */ | |
212 | return; | |
213 | } | |
214 | ||
215 | /* We may get SIGSEGV due to missing PROT_EXEC of the RETURN_ADDRESS page. */ | |
216 | if (WSTOPSIG (status) == SIGSEGV && pc == return_address) | |
217 | { | |
218 | /* PASS */ | |
219 | return; | |
220 | } | |
221 | ||
6e3c039e JK |
222 | if ((void (*) (void)) pc != &linux_ptrace_test_ret_to_nx_instr) |
223 | warning (_("linux_ptrace_test_ret_to_nx: PC %p is neither near return " | |
224 | "address %p nor is the return instruction %p!"), | |
225 | pc, return_address, &linux_ptrace_test_ret_to_nx_instr); | |
226 | else | |
227 | warning (_("Cannot call inferior functions, you have broken " | |
228 | "Linux kernel i386 NX (non-executable pages) support!")); | |
229 | #endif /* defined __i386__ || defined __x86_64__ */ | |
aa7c7447 JK |
230 | } |
231 | ||
232 | /* Display possible problems on this system. Display them only once per GDB | |
233 | execution. */ | |
234 | ||
235 | void | |
236 | linux_ptrace_init_warnings (void) | |
237 | { | |
238 | static int warned = 0; | |
239 | ||
240 | if (warned) | |
241 | return; | |
242 | warned = 1; | |
243 | ||
244 | linux_ptrace_test_ret_to_nx (); | |
245 | } |