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5f572dec | 1 | /* Linux-specific ptrace manipulation routines. |
42a4f53d | 2 | Copyright (C) 2012-2019 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 | ||
268a13a5 | 19 | #include "gdbsupport/common-defs.h" |
5f572dec | 20 | #include "linux-ptrace.h" |
87b0bb13 | 21 | #include "linux-procfs.h" |
125f8a3d | 22 | #include "linux-waitpid.h" |
268a13a5 | 23 | #include "gdbsupport/buffer.h" |
381beca6 SDJ |
24 | #include "gdbsupport/gdb-dlfcn.h" |
25 | #include "nat/fork-inferior.h" | |
26 | #include "gdbsupport/filestuff.h" | |
2132fe85 | 27 | #ifdef HAVE_SYS_PROCFS_H |
39b22471 | 28 | #include <sys/procfs.h> |
2132fe85 | 29 | #endif |
87b0bb13 | 30 | |
de0d863e DB |
31 | /* Stores the ptrace options supported by the running kernel. |
32 | A value of -1 means we did not check for features yet. A value | |
33 | of 0 means there are no supported features. */ | |
34 | static int supported_ptrace_options = -1; | |
8009206a | 35 | |
381beca6 | 36 | typedef int (*selinux_ftype) (const char *); |
87b0bb13 | 37 | |
381beca6 SDJ |
38 | /* Helper function which checks if ptrace is probably restricted |
39 | (i.e., if ERR is either EACCES or EPERM), and returns a string with | |
40 | possible workarounds. */ | |
41 | ||
42 | static std::string | |
43 | linux_ptrace_restricted_fail_reason (int err) | |
44 | { | |
45 | if (err != EACCES && err != EPERM) | |
46 | { | |
47 | /* It just makes sense to perform the checks below if errno was | |
48 | either EACCES or EPERM. */ | |
49 | return {}; | |
50 | } | |
51 | ||
52 | std::string ret; | |
53 | gdb_dlhandle_up handle; | |
54 | ||
55 | try | |
56 | { | |
57 | handle = gdb_dlopen ("libselinux.so.1"); | |
58 | } | |
59 | catch (const gdb_exception_error &e) | |
60 | { | |
61 | handle.reset (nullptr); | |
62 | } | |
63 | ||
64 | if (handle != nullptr) | |
65 | { | |
66 | selinux_ftype selinux_get_bool | |
67 | = (selinux_ftype) gdb_dlsym (handle, "security_get_boolean_active"); | |
68 | ||
69 | if (selinux_get_bool != NULL | |
70 | && (*selinux_get_bool) ("deny_ptrace") == 1) | |
71 | string_appendf (ret, | |
72 | _("\n\ | |
73 | The SELinux 'deny_ptrace' option is enabled and preventing GDB\n\ | |
74 | from using 'ptrace'. You can disable it by executing (as root):\n\ | |
75 | \n\ | |
76 | setsebool deny_ptrace off\n")); | |
77 | } | |
78 | ||
79 | gdb_file_up yama_ptrace_scope | |
80 | = gdb_fopen_cloexec ("/proc/sys/kernel/yama/ptrace_scope", "r"); | |
81 | ||
82 | if (yama_ptrace_scope != nullptr) | |
83 | { | |
84 | char yama_scope = fgetc (yama_ptrace_scope.get ()); | |
85 | ||
86 | if (yama_scope != '0') | |
87 | string_appendf (ret, | |
88 | _("\n\ | |
89 | The Linux kernel's Yama ptrace scope is in effect, which can prevent\n\ | |
90 | GDB from using 'ptrace'. You can disable it by executing (as root):\n\ | |
91 | \n\ | |
92 | echo 0 > /proc/sys/kernel/yama/ptrace_scope\n")); | |
93 | } | |
94 | ||
95 | if (ret.empty ()) | |
96 | { | |
97 | /* It wasn't possible to determine the exact reason for the | |
98 | ptrace error. Let's just emit a generic error message | |
99 | pointing the user to our documentation, where she can find | |
100 | instructions on how to try to diagnose the problem. */ | |
101 | ret = _("\n\ | |
102 | There might be restrictions preventing ptrace from working. Please see\n\ | |
103 | the appendix \"Linux kernel ptrace restrictions\" in the GDB documentation\n\ | |
104 | for more details."); | |
105 | } | |
106 | ||
107 | /* The user may be debugging remotely, so we have to warn that | |
108 | the instructions above should be performed in the target. */ | |
109 | string_appendf (ret, | |
110 | _("\n\ | |
111 | If you are debugging the inferior remotely, the ptrace restriction(s) must\n\ | |
112 | be disabled in the target system (e.g., where GDBserver is running).")); | |
113 | ||
114 | return ret; | |
115 | } | |
116 | ||
117 | /* Find all possible reasons we could fail to attach PID and return | |
118 | these as a string. An empty string is returned if we didn't find | |
119 | any reason. Helper for linux_ptrace_attach_fail_reason and | |
120 | linux_ptrace_attach_fail_reason_lwp. */ | |
121 | ||
122 | static std::string | |
123 | linux_ptrace_attach_fail_reason_1 (pid_t pid) | |
87b0bb13 | 124 | { |
4d9b86e1 SM |
125 | pid_t tracerpid = linux_proc_get_tracerpid_nowarn (pid); |
126 | std::string result; | |
87b0bb13 | 127 | |
87b0bb13 | 128 | if (tracerpid > 0) |
4d9b86e1 SM |
129 | string_appendf (result, |
130 | _("process %d is already traced by process %d"), | |
131 | (int) pid, (int) tracerpid); | |
87b0bb13 | 132 | |
8784d563 | 133 | if (linux_proc_pid_is_zombie_nowarn (pid)) |
4d9b86e1 SM |
134 | string_appendf (result, |
135 | _("process %d is a zombie - the process has already " | |
136 | "terminated"), | |
137 | (int) pid); | |
138 | ||
139 | return result; | |
87b0bb13 | 140 | } |
aa7c7447 | 141 | |
8784d563 PA |
142 | /* See linux-ptrace.h. */ |
143 | ||
4d9b86e1 | 144 | std::string |
381beca6 SDJ |
145 | linux_ptrace_attach_fail_reason (pid_t pid, int err) |
146 | { | |
147 | std::string result = linux_ptrace_attach_fail_reason_1 (pid); | |
148 | std::string ptrace_restrict = linux_ptrace_restricted_fail_reason (err); | |
149 | ||
150 | if (!ptrace_restrict.empty ()) | |
151 | result += "\n" + ptrace_restrict; | |
152 | ||
153 | return result; | |
154 | } | |
155 | ||
156 | /* See linux-ptrace.h. */ | |
157 | ||
158 | std::string | |
159 | linux_ptrace_attach_fail_reason_lwp (ptid_t ptid, int err) | |
8784d563 | 160 | { |
4d9b86e1 | 161 | long lwpid = ptid.lwp (); |
381beca6 | 162 | std::string reason = linux_ptrace_attach_fail_reason_1 (lwpid); |
4d9b86e1 SM |
163 | |
164 | if (!reason.empty ()) | |
165 | return string_printf ("%s (%d), %s", safe_strerror (err), err, | |
166 | reason.c_str ()); | |
8784d563 | 167 | else |
4d9b86e1 | 168 | return string_printf ("%s (%d)", safe_strerror (err), err); |
8784d563 PA |
169 | } |
170 | ||
381beca6 SDJ |
171 | /* See linux-ptrace.h. */ |
172 | ||
173 | std::string | |
174 | linux_ptrace_me_fail_reason (int err) | |
175 | { | |
176 | return linux_ptrace_restricted_fail_reason (err); | |
177 | } | |
178 | ||
6e3c039e | 179 | #if defined __i386__ || defined __x86_64__ |
aa7c7447 JK |
180 | |
181 | /* Address of the 'ret' instruction in asm code block below. */ | |
56000a98 | 182 | EXTERN_C void linux_ptrace_test_ret_to_nx_instr (void); |
aa7c7447 JK |
183 | |
184 | #include <sys/reg.h> | |
185 | #include <sys/mman.h> | |
186 | #include <signal.h> | |
aa7c7447 | 187 | |
6e3c039e | 188 | #endif /* defined __i386__ || defined __x86_64__ */ |
aa7c7447 | 189 | |
a65f6835 PW |
190 | /* Kill CHILD. WHO is used to report warnings. */ |
191 | ||
192 | static void | |
193 | kill_child (pid_t child, const char *who) | |
194 | { | |
195 | pid_t got_pid; | |
196 | int kill_status; | |
197 | ||
198 | if (kill (child, SIGKILL) != 0) | |
199 | { | |
4ef5dbe4 | 200 | warning (_("%s: failed to kill child pid %ld %s"), |
a65f6835 PW |
201 | who, (long) child, safe_strerror (errno)); |
202 | return; | |
203 | } | |
204 | ||
205 | errno = 0; | |
206 | got_pid = my_waitpid (child, &kill_status, 0); | |
207 | if (got_pid != child) | |
208 | { | |
209 | warning (_("%s: " | |
210 | "kill waitpid returned %ld: %s"), | |
211 | who, (long) got_pid, safe_strerror (errno)); | |
212 | return; | |
213 | } | |
214 | if (!WIFSIGNALED (kill_status)) | |
215 | { | |
216 | warning (_("%s: " | |
217 | "kill status %d is not WIFSIGNALED!"), | |
218 | who, kill_status); | |
219 | return; | |
220 | } | |
221 | } | |
222 | ||
aa7c7447 | 223 | /* Test broken off-trunk Linux kernel patchset for NX support on i386. It was |
6e3c039e JK |
224 | removed in Fedora kernel 88fa1f0332d188795ed73d7ac2b1564e11a0b4cd. |
225 | ||
226 | Test also x86_64 arch for PaX support. */ | |
aa7c7447 JK |
227 | |
228 | static void | |
229 | linux_ptrace_test_ret_to_nx (void) | |
230 | { | |
6e3c039e | 231 | #if defined __i386__ || defined __x86_64__ |
aa7c7447 JK |
232 | pid_t child, got_pid; |
233 | gdb_byte *return_address, *pc; | |
234 | long l; | |
a65f6835 | 235 | int status; |
40c31709 | 236 | elf_gregset_t regs; |
aa7c7447 | 237 | |
224c3ddb SM |
238 | return_address |
239 | = (gdb_byte *) mmap (NULL, 2, PROT_READ | PROT_WRITE, | |
aa7c7447 JK |
240 | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); |
241 | if (return_address == MAP_FAILED) | |
242 | { | |
243 | warning (_("linux_ptrace_test_ret_to_nx: Cannot mmap: %s"), | |
049bb5de | 244 | safe_strerror (errno)); |
aa7c7447 JK |
245 | return; |
246 | } | |
247 | ||
248 | /* Put there 'int3'. */ | |
249 | *return_address = 0xcc; | |
250 | ||
251 | child = fork (); | |
252 | switch (child) | |
253 | { | |
254 | case -1: | |
255 | warning (_("linux_ptrace_test_ret_to_nx: Cannot fork: %s"), | |
049bb5de | 256 | safe_strerror (errno)); |
aa7c7447 JK |
257 | return; |
258 | ||
259 | case 0: | |
96d7229d LM |
260 | l = ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) NULL, |
261 | (PTRACE_TYPE_ARG4) NULL); | |
aa7c7447 JK |
262 | if (l != 0) |
263 | warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_TRACEME: %s"), | |
049bb5de | 264 | safe_strerror (errno)); |
aa7c7447 JK |
265 | else |
266 | { | |
6e3c039e | 267 | #if defined __i386__ |
aa7c7447 JK |
268 | asm volatile ("pushl %0;" |
269 | ".globl linux_ptrace_test_ret_to_nx_instr;" | |
270 | "linux_ptrace_test_ret_to_nx_instr:" | |
271 | "ret" | |
7406a500 | 272 | : : "r" (return_address) : "memory"); |
6e3c039e JK |
273 | #elif defined __x86_64__ |
274 | asm volatile ("pushq %0;" | |
275 | ".globl linux_ptrace_test_ret_to_nx_instr;" | |
276 | "linux_ptrace_test_ret_to_nx_instr:" | |
277 | "ret" | |
bdad4180 | 278 | : : "r" ((uint64_t) (uintptr_t) return_address) |
7406a500 | 279 | : "memory"); |
6e3c039e JK |
280 | #else |
281 | # error "!__i386__ && !__x86_64__" | |
282 | #endif | |
aa7c7447 JK |
283 | gdb_assert_not_reached ("asm block did not terminate"); |
284 | } | |
285 | ||
286 | _exit (1); | |
287 | } | |
288 | ||
6e3c039e | 289 | errno = 0; |
aa7c7447 | 290 | got_pid = waitpid (child, &status, 0); |
6e3c039e JK |
291 | if (got_pid != child) |
292 | { | |
293 | warning (_("linux_ptrace_test_ret_to_nx: waitpid returned %ld: %s"), | |
049bb5de | 294 | (long) got_pid, safe_strerror (errno)); |
6e3c039e JK |
295 | return; |
296 | } | |
297 | ||
298 | if (WIFSIGNALED (status)) | |
299 | { | |
300 | if (WTERMSIG (status) != SIGKILL) | |
301 | warning (_("linux_ptrace_test_ret_to_nx: WTERMSIG %d is not SIGKILL!"), | |
302 | (int) WTERMSIG (status)); | |
303 | else | |
304 | warning (_("Cannot call inferior functions, Linux kernel PaX " | |
305 | "protection forbids return to non-executable pages!")); | |
306 | return; | |
307 | } | |
308 | ||
309 | if (!WIFSTOPPED (status)) | |
310 | { | |
311 | warning (_("linux_ptrace_test_ret_to_nx: status %d is not WIFSTOPPED!"), | |
312 | status); | |
a65f6835 | 313 | kill_child (child, "linux_ptrace_test_ret_to_nx"); |
6e3c039e JK |
314 | return; |
315 | } | |
aa7c7447 JK |
316 | |
317 | /* We may get SIGSEGV due to missing PROT_EXEC of the return_address. */ | |
6e3c039e JK |
318 | if (WSTOPSIG (status) != SIGTRAP && WSTOPSIG (status) != SIGSEGV) |
319 | { | |
320 | warning (_("linux_ptrace_test_ret_to_nx: " | |
321 | "WSTOPSIG %d is neither SIGTRAP nor SIGSEGV!"), | |
322 | (int) WSTOPSIG (status)); | |
a65f6835 | 323 | kill_child (child, "linux_ptrace_test_ret_to_nx"); |
6e3c039e JK |
324 | return; |
325 | } | |
aa7c7447 | 326 | |
40c31709 PA |
327 | if (ptrace (PTRACE_GETREGS, child, (PTRACE_TYPE_ARG3) 0, |
328 | (PTRACE_TYPE_ARG4) ®s) < 0) | |
329 | { | |
330 | warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_GETREGS: %s"), | |
331 | safe_strerror (errno)); | |
332 | } | |
6e3c039e | 333 | #if defined __i386__ |
40c31709 | 334 | pc = (gdb_byte *) (uintptr_t) regs[EIP]; |
6e3c039e | 335 | #elif defined __x86_64__ |
40c31709 | 336 | pc = (gdb_byte *) (uintptr_t) regs[RIP]; |
6e3c039e JK |
337 | #else |
338 | # error "!__i386__ && !__x86_64__" | |
339 | #endif | |
aa7c7447 | 340 | |
a65f6835 | 341 | kill_child (child, "linux_ptrace_test_ret_to_nx"); |
aa7c7447 JK |
342 | |
343 | /* + 1 is there as x86* stops after the 'int3' instruction. */ | |
344 | if (WSTOPSIG (status) == SIGTRAP && pc == return_address + 1) | |
345 | { | |
346 | /* PASS */ | |
347 | return; | |
348 | } | |
349 | ||
350 | /* We may get SIGSEGV due to missing PROT_EXEC of the RETURN_ADDRESS page. */ | |
351 | if (WSTOPSIG (status) == SIGSEGV && pc == return_address) | |
352 | { | |
353 | /* PASS */ | |
354 | return; | |
355 | } | |
356 | ||
6e3c039e JK |
357 | if ((void (*) (void)) pc != &linux_ptrace_test_ret_to_nx_instr) |
358 | warning (_("linux_ptrace_test_ret_to_nx: PC %p is neither near return " | |
359 | "address %p nor is the return instruction %p!"), | |
360 | pc, return_address, &linux_ptrace_test_ret_to_nx_instr); | |
361 | else | |
025e6dce PA |
362 | warning (_("Cannot call inferior functions on this system - " |
363 | "Linux kernel with broken i386 NX (non-executable pages) " | |
364 | "support detected!")); | |
6e3c039e | 365 | #endif /* defined __i386__ || defined __x86_64__ */ |
aa7c7447 JK |
366 | } |
367 | ||
381beca6 SDJ |
368 | /* If the PTRACE_TRACEME call on linux_child_function errors, we need |
369 | to be able to send ERRNO back to the parent so that it can check | |
370 | whether there are restrictions in place preventing ptrace from | |
371 | working. We do that with a pipe. */ | |
372 | static int errno_pipe[2]; | |
373 | ||
96d7229d LM |
374 | /* Helper function to fork a process and make the child process call |
375 | the function FUNCTION, passing CHILD_STACK as parameter. | |
376 | ||
377 | For MMU-less targets, clone is used instead of fork, and | |
378 | CHILD_STACK is used as stack space for the cloned child. If NULL, | |
379 | stack space is allocated via malloc (and subsequently passed to | |
380 | FUNCTION). For MMU targets, CHILD_STACK is ignored. */ | |
381 | ||
382 | static int | |
ba4dd7c4 | 383 | linux_fork_to_function (gdb_byte *child_stack, int (*function) (void *)) |
96d7229d LM |
384 | { |
385 | int child_pid; | |
386 | ||
387 | /* Sanity check the function pointer. */ | |
388 | gdb_assert (function != NULL); | |
389 | ||
381beca6 SDJ |
390 | /* Create the pipe that will be used by the child to pass ERRNO |
391 | after the PTRACE_TRACEME call. */ | |
392 | if (pipe (errno_pipe) != 0) | |
393 | trace_start_error_with_name ("pipe"); | |
394 | ||
96d7229d LM |
395 | #if defined(__UCLIBC__) && defined(HAS_NOMMU) |
396 | #define STACK_SIZE 4096 | |
397 | ||
398 | if (child_stack == NULL) | |
ffce45d2 | 399 | child_stack = (gdb_byte *) xmalloc (STACK_SIZE * 4); |
96d7229d LM |
400 | |
401 | /* Use CLONE_VM instead of fork, to support uClinux (no MMU). */ | |
101158d9 | 402 | #ifdef __ia64__ |
96d7229d LM |
403 | child_pid = __clone2 (function, child_stack, STACK_SIZE, |
404 | CLONE_VM | SIGCHLD, child_stack + STACK_SIZE * 2); | |
101158d9 | 405 | #else /* !__ia64__ */ |
96d7229d LM |
406 | child_pid = clone (function, child_stack + STACK_SIZE, |
407 | CLONE_VM | SIGCHLD, child_stack + STACK_SIZE * 2); | |
101158d9 | 408 | #endif /* !__ia64__ */ |
96d7229d LM |
409 | #else /* !defined(__UCLIBC) && defined(HAS_NOMMU) */ |
410 | child_pid = fork (); | |
411 | ||
412 | if (child_pid == 0) | |
413 | function (NULL); | |
414 | #endif /* defined(__UCLIBC) && defined(HAS_NOMMU) */ | |
415 | ||
416 | if (child_pid == -1) | |
417 | perror_with_name (("fork")); | |
418 | ||
419 | return child_pid; | |
420 | } | |
421 | ||
422 | /* A helper function for linux_check_ptrace_features, called after | |
423 | the child forks a grandchild. */ | |
424 | ||
ba4dd7c4 YQ |
425 | static int |
426 | linux_grandchild_function (void *child_stack) | |
96d7229d LM |
427 | { |
428 | /* Free any allocated stack. */ | |
429 | xfree (child_stack); | |
430 | ||
431 | /* This code is only reacheable by the grandchild (child's child) | |
432 | process. */ | |
433 | _exit (0); | |
434 | } | |
435 | ||
436 | /* A helper function for linux_check_ptrace_features, called after | |
437 | the parent process forks a child. The child allows itself to | |
438 | be traced by its parent. */ | |
439 | ||
ba4dd7c4 YQ |
440 | static int |
441 | linux_child_function (void *child_stack) | |
96d7229d | 442 | { |
381beca6 SDJ |
443 | /* Close read end. */ |
444 | close (errno_pipe[0]); | |
445 | ||
446 | int ret = ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0, | |
447 | (PTRACE_TYPE_ARG4) 0); | |
448 | int ptrace_errno = errno; | |
449 | ||
450 | /* Write ERRNO to the pipe, even if it's zero, and close the writing | |
451 | end of the pipe. */ | |
452 | write (errno_pipe[1], &ptrace_errno, sizeof (ptrace_errno)); | |
453 | close (errno_pipe[1]); | |
454 | ||
455 | if (ret != 0) | |
456 | _exit (0); | |
457 | ||
96d7229d LM |
458 | kill (getpid (), SIGSTOP); |
459 | ||
460 | /* Fork a grandchild. */ | |
d18547d8 | 461 | linux_fork_to_function ((gdb_byte *) child_stack, linux_grandchild_function); |
96d7229d LM |
462 | |
463 | /* This code is only reacheable by the child (grandchild's parent) | |
464 | process. */ | |
465 | _exit (0); | |
466 | } | |
467 | ||
8ae377e8 PA |
468 | static void linux_test_for_tracesysgood (int child_pid); |
469 | static void linux_test_for_tracefork (int child_pid); | |
beed38b8 | 470 | static void linux_test_for_exitkill (int child_pid); |
8ae377e8 | 471 | |
381beca6 SDJ |
472 | /* Helper function to wait for the child to send us the ptrace ERRNO, |
473 | and check if it's OK. */ | |
474 | ||
475 | static void | |
476 | linux_check_child_ptrace_errno () | |
477 | { | |
478 | int child_errno; | |
479 | fd_set rset; | |
480 | struct timeval timeout; | |
481 | ||
482 | /* Close the writing end of the pipe. */ | |
483 | close (errno_pipe[1]); | |
484 | ||
485 | FD_ZERO (&rset); | |
486 | FD_SET (errno_pipe[0], &rset); | |
487 | ||
488 | /* One second should be plenty of time to wait for the child's | |
489 | reply. */ | |
490 | timeout.tv_sec = 1; | |
491 | timeout.tv_usec = 0; | |
492 | ||
493 | int ret = select (errno_pipe[0] + 1, &rset, NULL, NULL, &timeout); | |
494 | ||
495 | if (ret < 0) | |
496 | trace_start_error_with_name ("select"); | |
497 | else if (ret == 0) | |
498 | error (_("Timeout while waiting for child's ptrace errno")); | |
499 | else | |
500 | read (errno_pipe[0], &child_errno, sizeof (child_errno)); | |
501 | ||
502 | if (child_errno != 0) | |
503 | { | |
504 | /* The child can't use PTRACE_TRACEME. We just bail out. */ | |
505 | std::string reason = linux_ptrace_restricted_fail_reason (child_errno); | |
506 | ||
507 | errno = child_errno; | |
508 | trace_start_error_with_name ("ptrace", reason.c_str ()); | |
509 | } | |
510 | ||
511 | close (errno_pipe[0]); | |
512 | } | |
513 | ||
96d7229d LM |
514 | /* Determine ptrace features available on this target. */ |
515 | ||
89245bc0 | 516 | void |
96d7229d LM |
517 | linux_check_ptrace_features (void) |
518 | { | |
519 | int child_pid, ret, status; | |
96d7229d LM |
520 | |
521 | /* Initialize the options. */ | |
de0d863e | 522 | supported_ptrace_options = 0; |
96d7229d LM |
523 | |
524 | /* Fork a child so we can do some testing. The child will call | |
525 | linux_child_function and will get traced. The child will | |
526 | eventually fork a grandchild so we can test fork event | |
527 | reporting. */ | |
528 | child_pid = linux_fork_to_function (NULL, linux_child_function); | |
529 | ||
381beca6 SDJ |
530 | /* Check if the child can successfully use ptrace. */ |
531 | linux_check_child_ptrace_errno (); | |
532 | ||
96d7229d LM |
533 | ret = my_waitpid (child_pid, &status, 0); |
534 | if (ret == -1) | |
535 | perror_with_name (("waitpid")); | |
536 | else if (ret != child_pid) | |
537 | error (_("linux_check_ptrace_features: waitpid: unexpected result %d."), | |
538 | ret); | |
539 | if (! WIFSTOPPED (status)) | |
540 | error (_("linux_check_ptrace_features: waitpid: unexpected status %d."), | |
541 | status); | |
542 | ||
8ae377e8 | 543 | linux_test_for_tracesysgood (child_pid); |
96d7229d | 544 | |
8ae377e8 PA |
545 | linux_test_for_tracefork (child_pid); |
546 | ||
beed38b8 JB |
547 | linux_test_for_exitkill (child_pid); |
548 | ||
a65f6835 PW |
549 | /* Kill child_pid. */ |
550 | kill_child (child_pid, "linux_check_ptrace_features"); | |
8ae377e8 | 551 | } |
96d7229d | 552 | |
8ae377e8 PA |
553 | /* Determine if PTRACE_O_TRACESYSGOOD can be used to catch |
554 | syscalls. */ | |
555 | ||
556 | static void | |
557 | linux_test_for_tracesysgood (int child_pid) | |
558 | { | |
8ae377e8 PA |
559 | int ret; |
560 | ||
96d7229d LM |
561 | ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0, |
562 | (PTRACE_TYPE_ARG4) PTRACE_O_TRACESYSGOOD); | |
8009206a | 563 | |
96d7229d | 564 | if (ret == 0) |
de0d863e | 565 | supported_ptrace_options |= PTRACE_O_TRACESYSGOOD; |
8ae377e8 | 566 | } |
96d7229d | 567 | |
8ae377e8 PA |
568 | /* Determine if PTRACE_O_TRACEFORK can be used to follow fork |
569 | events. */ | |
570 | ||
571 | static void | |
572 | linux_test_for_tracefork (int child_pid) | |
573 | { | |
574 | int ret, status; | |
575 | long second_pid; | |
576 | ||
577 | /* First, set the PTRACE_O_TRACEFORK option. If this fails, we | |
578 | know for sure that it is not supported. */ | |
579 | ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0, | |
580 | (PTRACE_TYPE_ARG4) PTRACE_O_TRACEFORK); | |
581 | ||
582 | if (ret != 0) | |
583 | return; | |
584 | ||
de0d863e DB |
585 | /* Check if the target supports PTRACE_O_TRACEVFORKDONE. */ |
586 | ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0, | |
587 | (PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK | |
588 | | PTRACE_O_TRACEVFORKDONE)); | |
589 | if (ret == 0) | |
590 | supported_ptrace_options |= PTRACE_O_TRACEVFORKDONE; | |
96d7229d LM |
591 | |
592 | /* Setting PTRACE_O_TRACEFORK did not cause an error, however we | |
593 | don't know for sure that the feature is available; old | |
594 | versions of PTRACE_SETOPTIONS ignored unknown options. | |
595 | Therefore, we attach to the child process, use PTRACE_SETOPTIONS | |
596 | to enable fork tracing, and let it fork. If the process exits, | |
597 | we assume that we can't use PTRACE_O_TRACEFORK; if we get the | |
598 | fork notification, and we can extract the new child's PID, then | |
599 | we assume that we can. | |
600 | ||
601 | We do not explicitly check for vfork tracing here. It is | |
602 | assumed that vfork tracing is available whenever fork tracing | |
603 | is available. */ | |
604 | ret = ptrace (PTRACE_CONT, child_pid, (PTRACE_TYPE_ARG3) 0, | |
605 | (PTRACE_TYPE_ARG4) 0); | |
606 | if (ret != 0) | |
8ae377e8 | 607 | warning (_("linux_test_for_tracefork: failed to resume child")); |
96d7229d LM |
608 | |
609 | ret = my_waitpid (child_pid, &status, 0); | |
610 | ||
611 | /* Check if we received a fork event notification. */ | |
612 | if (ret == child_pid && WIFSTOPPED (status) | |
89a5711c | 613 | && linux_ptrace_get_extended_event (status) == PTRACE_EVENT_FORK) |
96d7229d LM |
614 | { |
615 | /* We did receive a fork event notification. Make sure its PID | |
616 | is reported. */ | |
617 | second_pid = 0; | |
618 | ret = ptrace (PTRACE_GETEVENTMSG, child_pid, (PTRACE_TYPE_ARG3) 0, | |
619 | (PTRACE_TYPE_ARG4) &second_pid); | |
620 | if (ret == 0 && second_pid != 0) | |
621 | { | |
622 | int second_status; | |
623 | ||
624 | /* We got the PID from the grandchild, which means fork | |
625 | tracing is supported. */ | |
de0d863e DB |
626 | supported_ptrace_options |= PTRACE_O_TRACECLONE; |
627 | supported_ptrace_options |= (PTRACE_O_TRACEFORK | |
628 | | PTRACE_O_TRACEVFORK | |
629 | | PTRACE_O_TRACEEXEC); | |
96d7229d LM |
630 | |
631 | /* Do some cleanup and kill the grandchild. */ | |
632 | my_waitpid (second_pid, &second_status, 0); | |
a65f6835 | 633 | kill_child (second_pid, "linux_test_for_tracefork"); |
96d7229d LM |
634 | } |
635 | } | |
636 | else | |
8ae377e8 | 637 | warning (_("linux_test_for_tracefork: unexpected result from waitpid " |
96d7229d | 638 | "(%d, status 0x%x)"), ret, status); |
96d7229d LM |
639 | } |
640 | ||
beed38b8 JB |
641 | /* Determine if PTRACE_O_EXITKILL can be used. */ |
642 | ||
643 | static void | |
644 | linux_test_for_exitkill (int child_pid) | |
645 | { | |
646 | int ret; | |
647 | ||
648 | ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0, | |
649 | (PTRACE_TYPE_ARG4) PTRACE_O_EXITKILL); | |
650 | ||
651 | if (ret == 0) | |
de0d863e | 652 | supported_ptrace_options |= PTRACE_O_EXITKILL; |
beed38b8 JB |
653 | } |
654 | ||
655 | /* Enable reporting of all currently supported ptrace events. | |
de0d863e DB |
656 | OPTIONS is a bit mask of extended features we want enabled, |
657 | if supported by the kernel. PTRACE_O_TRACECLONE is always | |
658 | enabled, if supported. */ | |
96d7229d LM |
659 | |
660 | void | |
de0d863e | 661 | linux_enable_event_reporting (pid_t pid, int options) |
96d7229d LM |
662 | { |
663 | /* Check if we have initialized the ptrace features for this | |
664 | target. If not, do it now. */ | |
de0d863e | 665 | if (supported_ptrace_options == -1) |
96d7229d LM |
666 | linux_check_ptrace_features (); |
667 | ||
de0d863e DB |
668 | /* We always want clone events. */ |
669 | options |= PTRACE_O_TRACECLONE; | |
670 | ||
671 | /* Filter out unsupported options. */ | |
672 | options &= supported_ptrace_options; | |
beed38b8 | 673 | |
96d7229d LM |
674 | /* Set the options. */ |
675 | ptrace (PTRACE_SETOPTIONS, pid, (PTRACE_TYPE_ARG3) 0, | |
de0d863e | 676 | (PTRACE_TYPE_ARG4) (uintptr_t) options); |
96d7229d LM |
677 | } |
678 | ||
c077881a HZ |
679 | /* Disable reporting of all currently supported ptrace events. */ |
680 | ||
681 | void | |
682 | linux_disable_event_reporting (pid_t pid) | |
683 | { | |
684 | /* Set the options. */ | |
685 | ptrace (PTRACE_SETOPTIONS, pid, (PTRACE_TYPE_ARG3) 0, 0); | |
686 | } | |
687 | ||
96d7229d | 688 | /* Returns non-zero if PTRACE_OPTIONS is contained within |
de0d863e | 689 | SUPPORTED_PTRACE_OPTIONS, therefore supported. Returns 0 |
96d7229d LM |
690 | otherwise. */ |
691 | ||
692 | static int | |
693 | ptrace_supports_feature (int ptrace_options) | |
694 | { | |
de0d863e | 695 | if (supported_ptrace_options == -1) |
8784d563 | 696 | linux_check_ptrace_features (); |
96d7229d | 697 | |
de0d863e | 698 | return ((supported_ptrace_options & ptrace_options) == ptrace_options); |
96d7229d LM |
699 | } |
700 | ||
701 | /* Returns non-zero if PTRACE_EVENT_FORK is supported by ptrace, | |
702 | 0 otherwise. Note that if PTRACE_EVENT_FORK is supported so is | |
703 | PTRACE_EVENT_CLONE, PTRACE_EVENT_EXEC and PTRACE_EVENT_VFORK, | |
704 | since they were all added to the kernel at the same time. */ | |
705 | ||
706 | int | |
707 | linux_supports_tracefork (void) | |
708 | { | |
709 | return ptrace_supports_feature (PTRACE_O_TRACEFORK); | |
710 | } | |
711 | ||
94585166 DB |
712 | /* Returns non-zero if PTRACE_EVENT_EXEC is supported by ptrace, |
713 | 0 otherwise. Note that if PTRACE_EVENT_FORK is supported so is | |
714 | PTRACE_EVENT_CLONE, PTRACE_EVENT_FORK and PTRACE_EVENT_VFORK, | |
715 | since they were all added to the kernel at the same time. */ | |
716 | ||
717 | int | |
718 | linux_supports_traceexec (void) | |
719 | { | |
720 | return ptrace_supports_feature (PTRACE_O_TRACEEXEC); | |
721 | } | |
722 | ||
96d7229d LM |
723 | /* Returns non-zero if PTRACE_EVENT_CLONE is supported by ptrace, |
724 | 0 otherwise. Note that if PTRACE_EVENT_CLONE is supported so is | |
725 | PTRACE_EVENT_FORK, PTRACE_EVENT_EXEC and PTRACE_EVENT_VFORK, | |
726 | since they were all added to the kernel at the same time. */ | |
727 | ||
728 | int | |
729 | linux_supports_traceclone (void) | |
730 | { | |
731 | return ptrace_supports_feature (PTRACE_O_TRACECLONE); | |
732 | } | |
733 | ||
734 | /* Returns non-zero if PTRACE_O_TRACEVFORKDONE is supported by | |
735 | ptrace, 0 otherwise. */ | |
736 | ||
737 | int | |
738 | linux_supports_tracevforkdone (void) | |
739 | { | |
740 | return ptrace_supports_feature (PTRACE_O_TRACEVFORKDONE); | |
741 | } | |
742 | ||
743 | /* Returns non-zero if PTRACE_O_TRACESYSGOOD is supported by ptrace, | |
744 | 0 otherwise. */ | |
745 | ||
746 | int | |
747 | linux_supports_tracesysgood (void) | |
748 | { | |
749 | return ptrace_supports_feature (PTRACE_O_TRACESYSGOOD); | |
750 | } | |
751 | ||
aa7c7447 JK |
752 | /* Display possible problems on this system. Display them only once per GDB |
753 | execution. */ | |
754 | ||
755 | void | |
756 | linux_ptrace_init_warnings (void) | |
757 | { | |
758 | static int warned = 0; | |
759 | ||
760 | if (warned) | |
761 | return; | |
762 | warned = 1; | |
763 | ||
764 | linux_ptrace_test_ret_to_nx (); | |
765 | } | |
8009206a | 766 | |
89a5711c DB |
767 | /* Extract extended ptrace event from wait status. */ |
768 | ||
769 | int | |
770 | linux_ptrace_get_extended_event (int wstat) | |
771 | { | |
772 | return (wstat >> 16); | |
773 | } | |
774 | ||
775 | /* Determine whether wait status denotes an extended event. */ | |
776 | ||
777 | int | |
778 | linux_is_extended_waitstatus (int wstat) | |
779 | { | |
780 | return (linux_ptrace_get_extended_event (wstat) != 0); | |
781 | } | |
c9587f88 AT |
782 | |
783 | /* Return true if the event in LP may be caused by breakpoint. */ | |
784 | ||
785 | int | |
786 | linux_wstatus_maybe_breakpoint (int wstat) | |
787 | { | |
788 | return (WIFSTOPPED (wstat) | |
789 | && (WSTOPSIG (wstat) == SIGTRAP | |
790 | /* SIGILL and SIGSEGV are also treated as traps in case a | |
791 | breakpoint is inserted at the current PC. */ | |
792 | || WSTOPSIG (wstat) == SIGILL | |
793 | || WSTOPSIG (wstat) == SIGSEGV)); | |
794 | } |