1 /*
2 * Copyright (c) 1991, 1992 Paul Kranenburg <pk@cs.few.eur.nl>
3 * Copyright (c) 1993 Branko Lankester <branko@hacktic.nl>
4 * Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <jrs@world.std.com>
5 * Copyright (c) 1996-1999 Wichert Akkerman <wichert@cistron.nl>
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. The name of the author may not be used to endorse or promote products
17 * derived from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31 #include "defs.h"
32 #include <stdarg.h>
33 #include <sys/param.h>
34 #include <fcntl.h>
35 #include <sys/resource.h>
36 #include <sys/wait.h>
37 #include <sys/stat.h>
38 #include <pwd.h>
39 #include <grp.h>
40 #include <dirent.h>
41 #include <sys/utsname.h>
42 #ifdef HAVE_PRCTL
43 # include <sys/prctl.h>
44 #endif
45 #if defined(IA64)
46 # include <asm/ptrace_offsets.h>
47 #endif
48 /* In some libc, these aren't declared. Do it ourself: */
49 extern char **environ;
50 extern int optind;
51 extern char *optarg;
52
53 #ifdef USE_LIBUNWIND
54 /* if this is true do the stack trace for every system call */
55 bool stack_trace_enabled = false;
56 #endif
57
58 #if defined __NR_tkill
59 # define my_tkill(tid, sig) syscall(__NR_tkill, (tid), (sig))
60 #else
61 /* kill() may choose arbitrarily the target task of the process group
62 while we later wait on a that specific TID. PID process waits become
63 TID task specific waits for a process under ptrace(2). */
64 # warning "tkill(2) not available, risk of strace hangs!"
65 # define my_tkill(tid, sig) kill((tid), (sig))
66 #endif
67
68 /* Glue for systems without a MMU that cannot provide fork() */
69 #if !defined(HAVE_FORK)
70 # undef NOMMU_SYSTEM
71 # define NOMMU_SYSTEM 1
72 #endif
73 #if NOMMU_SYSTEM
74 # define fork() vfork()
75 #endif
76
77 cflag_t cflag = CFLAG_NONE;
78 unsigned int followfork = 0;
79 unsigned int ptrace_setoptions = 0;
80 unsigned int xflag = 0;
81 bool need_fork_exec_workarounds = 0;
82 bool debug_flag = 0;
83 bool Tflag = 0;
84 bool iflag = 0;
85 bool count_wallclock = 0;
86 unsigned int qflag = 0;
87 /* Which WSTOPSIG(status) value marks syscall traps? */
88 static unsigned int syscall_trap_sig = SIGTRAP;
89 static unsigned int tflag = 0;
90 static bool rflag = 0;
91 static bool print_pid_pfx = 0;
92
93 /* -I n */
94 enum {
95 INTR_NOT_SET = 0,
96 INTR_ANYWHERE = 1, /* don't block/ignore any signals */
97 INTR_WHILE_WAIT = 2, /* block fatal signals while decoding syscall. default */
98 INTR_NEVER = 3, /* block fatal signals. default if '-o FILE PROG' */
99 INTR_BLOCK_TSTP_TOO = 4, /* block fatal signals and SIGTSTP (^Z) */
100 NUM_INTR_OPTS
101 };
102 static int opt_intr;
103 /* We play with signal mask only if this mode is active: */
104 #define interactive (opt_intr == INTR_WHILE_WAIT)
105
106 /*
107 * daemonized_tracer supports -D option.
108 * With this option, strace forks twice.
109 * Unlike normal case, with -D *grandparent* process exec's,
110 * becoming a traced process. Child exits (this prevents traced process
111 * from having children it doesn't expect to have), and grandchild
112 * attaches to grandparent similarly to strace -p PID.
113 * This allows for more transparent interaction in cases
114 * when process and its parent are communicating via signals,
115 * wait() etc. Without -D, strace process gets lodged in between,
116 * disrupting parent<->child link.
117 */
118 static bool daemonized_tracer = 0;
119
120 #if USE_SEIZE
121 static int post_attach_sigstop = TCB_IGNORE_ONE_SIGSTOP;
122 # define use_seize (post_attach_sigstop == 0)
123 #else
124 # define post_attach_sigstop TCB_IGNORE_ONE_SIGSTOP
125 # define use_seize 0
126 #endif
127
128 /* Sometimes we want to print only succeeding syscalls. */
129 bool not_failing_only = 0;
130
131 /* Show path associated with fd arguments */
132 bool show_fd_path = 0;
133
134 static bool detach_on_execve = 0;
135 /* Are we "strace PROG" and need to skip detach on first execve? */
136 static bool skip_one_b_execve = 0;
137 /* Are we "strace PROG" and need to hide everything until execve? */
138 bool hide_log_until_execve = 0;
139
140 static int exit_code = 0;
141 static int strace_child = 0;
142 static int strace_tracer_pid = 0;
143
144 static char *username = NULL;
145 static uid_t run_uid;
146 static gid_t run_gid;
147
148 unsigned int max_strlen = DEFAULT_STRLEN;
149 static int acolumn = DEFAULT_ACOLUMN;
150 static char *acolumn_spaces;
151
152 static char *outfname = NULL;
153 /* If -ff, points to stderr. Else, it's our common output log */
154 static FILE *shared_log;
155
156 struct tcb *printing_tcp = NULL;
157 static struct tcb *current_tcp;
158
159 static struct tcb **tcbtab;
160 static unsigned int nprocs, tcbtabsize;
161 static const char *progname;
162
163 unsigned os_release; /* generated from uname()'s u.release */
164
165 static void detach(struct tcb *tcp);
166 static void cleanup(void);
167 static void interrupt(int sig);
168 static sigset_t empty_set, blocked_set;
169
170 #ifdef HAVE_SIG_ATOMIC_T
171 static volatile sig_atomic_t interrupted;
172 #else
173 static volatile int interrupted;
174 #endif
175
176 #ifndef HAVE_STRERROR
177
178 #if !HAVE_DECL_SYS_ERRLIST
179 extern int sys_nerr;
180 extern char *sys_errlist[];
181 #endif
182
183 const char *
strerror(int err_no)184 strerror(int err_no)
185 {
186 static char buf[sizeof("Unknown error %d") + sizeof(int)*3];
187
188 if (err_no < 1 || err_no >= sys_nerr) {
189 sprintf(buf, "Unknown error %d", err_no);
190 return buf;
191 }
192 return sys_errlist[err_no];
193 }
194
195 #endif /* HAVE_STERRROR */
196
197 static void
usage(FILE * ofp,int exitval)198 usage(FILE *ofp, int exitval)
199 {
200 fprintf(ofp, "\
201 usage: strace [-CdffhiqrtttTvVxxy] [-I n] [-e expr]...\n\
202 [-a column] [-o file] [-s strsize] [-P path]...\n\
203 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
204 or: strace -c[df] [-I n] [-e expr]... [-O overhead] [-S sortby]\n\
205 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
206 -c -- count time, calls, and errors for each syscall and report summary\n\
207 -C -- like -c but also print regular output\n\
208 -w -- summarise syscall latency (default is system time)\n\
209 -d -- enable debug output to stderr\n\
210 -D -- run tracer process as a detached grandchild, not as parent\n\
211 -f -- follow forks, -ff -- with output into separate files\n\
212 -i -- print instruction pointer at time of syscall\n\
213 -q -- suppress messages about attaching, detaching, etc.\n\
214 -r -- print relative timestamp, -t -- absolute timestamp, -tt -- with usecs\n\
215 -T -- print time spent in each syscall\n\
216 -v -- verbose mode: print unabbreviated argv, stat, termios, etc. args\n\
217 -x -- print non-ascii strings in hex, -xx -- print all strings in hex\n\
218 -y -- print paths associated with file descriptor arguments\n\
219 -h -- print help message, -V -- print version\n\
220 -a column -- alignment COLUMN for printing syscall results (default %d)\n\
221 -b execve -- detach on this syscall\n\
222 -e expr -- a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
223 options: trace, abbrev, verbose, raw, signal, read, write\n\
224 -I interruptible --\n\
225 1: no signals are blocked\n\
226 2: fatal signals are blocked while decoding syscall (default)\n\
227 3: fatal signals are always blocked (default if '-o FILE PROG')\n\
228 4: fatal signals and SIGTSTP (^Z) are always blocked\n\
229 (useful to make 'strace -o FILE PROG' not stop on ^Z)\n\
230 -o file -- send trace output to FILE instead of stderr\n\
231 -O overhead -- set overhead for tracing syscalls to OVERHEAD usecs\n\
232 -p pid -- trace process with process id PID, may be repeated\n\
233 -s strsize -- limit length of print strings to STRSIZE chars (default %d)\n\
234 -S sortby -- sort syscall counts by: time, calls, name, nothing (default %s)\n\
235 -u username -- run command as username handling setuid and/or setgid\n\
236 -E var=val -- put var=val in the environment for command\n\
237 -E var -- remove var from the environment for command\n\
238 -P path -- trace accesses to path\n\
239 "
240 #ifdef USE_LIBUNWIND
241 "-k obtain stack trace between each syscall (experimental)\n\
242 "
243 #endif
244 /* ancient, no one should use it
245 -F -- attempt to follow vforks (deprecated, use -f)\n\
246 */
247 /* this is broken, so don't document it
248 -z -- print only succeeding syscalls\n\
249 */
250 , DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
251 exit(exitval);
252 }
253
254 static void die(void) __attribute__ ((noreturn));
die(void)255 static void die(void)
256 {
257 if (strace_tracer_pid == getpid()) {
258 cflag = 0;
259 cleanup();
260 }
261 exit(1);
262 }
263
verror_msg(int err_no,const char * fmt,va_list p)264 static void verror_msg(int err_no, const char *fmt, va_list p)
265 {
266 char *msg;
267
268 fflush(NULL);
269
270 /* We want to print entire message with single fprintf to ensure
271 * message integrity if stderr is shared with other programs.
272 * Thus we use vasprintf + single fprintf.
273 */
274 msg = NULL;
275 if (vasprintf(&msg, fmt, p) >= 0) {
276 if (err_no)
277 fprintf(stderr, "%s: %s: %s\n", progname, msg, strerror(err_no));
278 else
279 fprintf(stderr, "%s: %s\n", progname, msg);
280 free(msg);
281 } else {
282 /* malloc in vasprintf failed, try it without malloc */
283 fprintf(stderr, "%s: ", progname);
284 vfprintf(stderr, fmt, p);
285 if (err_no)
286 fprintf(stderr, ": %s\n", strerror(err_no));
287 else
288 putc('\n', stderr);
289 }
290 /* We don't switch stderr to buffered, thus fprintf(stderr)
291 * always flushes its output and this is not necessary: */
292 /* fflush(stderr); */
293 }
294
error_msg(const char * fmt,...)295 void error_msg(const char *fmt, ...)
296 {
297 va_list p;
298 va_start(p, fmt);
299 verror_msg(0, fmt, p);
300 va_end(p);
301 }
302
error_msg_and_die(const char * fmt,...)303 void error_msg_and_die(const char *fmt, ...)
304 {
305 va_list p;
306 va_start(p, fmt);
307 verror_msg(0, fmt, p);
308 die();
309 }
310
perror_msg(const char * fmt,...)311 void perror_msg(const char *fmt, ...)
312 {
313 va_list p;
314 va_start(p, fmt);
315 verror_msg(errno, fmt, p);
316 va_end(p);
317 }
318
perror_msg_and_die(const char * fmt,...)319 void perror_msg_and_die(const char *fmt, ...)
320 {
321 va_list p;
322 va_start(p, fmt);
323 verror_msg(errno, fmt, p);
324 die();
325 }
326
die_out_of_memory(void)327 void die_out_of_memory(void)
328 {
329 static bool recursed = 0;
330 if (recursed)
331 exit(1);
332 recursed = 1;
333 error_msg_and_die("Out of memory");
334 }
335
336 static void
error_opt_arg(int opt,const char * arg)337 error_opt_arg(int opt, const char *arg)
338 {
339 error_msg_and_die("Invalid -%c argument: '%s'", opt, arg);
340 }
341
342 #if USE_SEIZE
343 static int
ptrace_attach_or_seize(int pid)344 ptrace_attach_or_seize(int pid)
345 {
346 int r;
347 if (!use_seize)
348 return ptrace(PTRACE_ATTACH, pid, 0L, 0L);
349 r = ptrace(PTRACE_SEIZE, pid, 0L, (unsigned long)ptrace_setoptions);
350 if (r)
351 return r;
352 r = ptrace(PTRACE_INTERRUPT, pid, 0L, 0L);
353 return r;
354 }
355 #else
356 # define ptrace_attach_or_seize(pid) ptrace(PTRACE_ATTACH, (pid), 0, 0)
357 #endif
358
359 /*
360 * Used when we want to unblock stopped traced process.
361 * Should be only used with PTRACE_CONT, PTRACE_DETACH and PTRACE_SYSCALL.
362 * Returns 0 on success or if error was ESRCH
363 * (presumably process was killed while we talk to it).
364 * Otherwise prints error message and returns -1.
365 */
366 static int
ptrace_restart(int op,struct tcb * tcp,int sig)367 ptrace_restart(int op, struct tcb *tcp, int sig)
368 {
369 int err;
370 const char *msg;
371
372 errno = 0;
373 ptrace(op, tcp->pid, (void *) 0, (long) sig);
374 err = errno;
375 if (!err)
376 return 0;
377
378 msg = "SYSCALL";
379 if (op == PTRACE_CONT)
380 msg = "CONT";
381 if (op == PTRACE_DETACH)
382 msg = "DETACH";
383 #ifdef PTRACE_LISTEN
384 if (op == PTRACE_LISTEN)
385 msg = "LISTEN";
386 #endif
387 /*
388 * Why curcol != 0? Otherwise sometimes we get this:
389 *
390 * 10252 kill(10253, SIGKILL) = 0
391 * <ptrace(SYSCALL,10252):No such process>10253 ...next decode...
392 *
393 * 10252 died after we retrieved syscall exit data,
394 * but before we tried to restart it. Log looks ugly.
395 */
396 if (current_tcp && current_tcp->curcol != 0) {
397 tprintf(" <ptrace(%s):%s>\n", msg, strerror(err));
398 line_ended();
399 }
400 if (err == ESRCH)
401 return 0;
402 errno = err;
403 perror_msg("ptrace(PTRACE_%s,pid:%d,sig:%d)", msg, tcp->pid, sig);
404 return -1;
405 }
406
407 static void
set_cloexec_flag(int fd)408 set_cloexec_flag(int fd)
409 {
410 int flags, newflags;
411
412 flags = fcntl(fd, F_GETFD);
413 if (flags < 0) {
414 /* Can happen only if fd is bad.
415 * Should never happen: if it does, we have a bug
416 * in the caller. Therefore we just abort
417 * instead of propagating the error.
418 */
419 perror_msg_and_die("fcntl(%d, F_GETFD)", fd);
420 }
421
422 newflags = flags | FD_CLOEXEC;
423 if (flags == newflags)
424 return;
425
426 fcntl(fd, F_SETFD, newflags); /* never fails */
427 }
428
kill_save_errno(pid_t pid,int sig)429 static void kill_save_errno(pid_t pid, int sig)
430 {
431 int saved_errno = errno;
432
433 (void) kill(pid, sig);
434 errno = saved_errno;
435 }
436
437 /*
438 * When strace is setuid executable, we have to swap uids
439 * before and after filesystem and process management operations.
440 */
441 static void
swap_uid(void)442 swap_uid(void)
443 {
444 int euid = geteuid(), uid = getuid();
445
446 if (euid != uid && setreuid(euid, uid) < 0) {
447 perror_msg_and_die("setreuid");
448 }
449 }
450
451 #ifdef _LARGEFILE64_SOURCE
452 # ifdef HAVE_FOPEN64
453 # define fopen_for_output fopen64
454 # else
455 # define fopen_for_output fopen
456 # endif
457 # define struct_stat struct stat64
458 # define stat_file stat64
459 # define struct_dirent struct dirent64
460 # define read_dir readdir64
461 # define struct_rlimit struct rlimit64
462 # define set_rlimit setrlimit64
463 #else
464 # define fopen_for_output fopen
465 # define struct_stat struct stat
466 # define stat_file stat
467 # define struct_dirent struct dirent
468 # define read_dir readdir
469 # define struct_rlimit struct rlimit
470 # define set_rlimit setrlimit
471 #endif
472
473 static FILE *
strace_fopen(const char * path)474 strace_fopen(const char *path)
475 {
476 FILE *fp;
477
478 swap_uid();
479 fp = fopen_for_output(path, "w");
480 if (!fp)
481 perror_msg_and_die("Can't fopen '%s'", path);
482 swap_uid();
483 set_cloexec_flag(fileno(fp));
484 return fp;
485 }
486
487 static int popen_pid = 0;
488
489 #ifndef _PATH_BSHELL
490 # define _PATH_BSHELL "/bin/sh"
491 #endif
492
493 /*
494 * We cannot use standard popen(3) here because we have to distinguish
495 * popen child process from other processes we trace, and standard popen(3)
496 * does not export its child's pid.
497 */
498 static FILE *
strace_popen(const char * command)499 strace_popen(const char *command)
500 {
501 FILE *fp;
502 int pid;
503 int fds[2];
504
505 swap_uid();
506 if (pipe(fds) < 0)
507 perror_msg_and_die("pipe");
508
509 set_cloexec_flag(fds[1]); /* never fails */
510
511 pid = vfork();
512 if (pid < 0)
513 perror_msg_and_die("vfork");
514
515 if (pid == 0) {
516 /* child */
517 close(fds[1]);
518 if (fds[0] != 0) {
519 if (dup2(fds[0], 0))
520 perror_msg_and_die("dup2");
521 close(fds[0]);
522 }
523 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
524 perror_msg_and_die("Can't execute '%s'", _PATH_BSHELL);
525 }
526
527 /* parent */
528 popen_pid = pid;
529 close(fds[0]);
530 swap_uid();
531 fp = fdopen(fds[1], "w");
532 if (!fp)
533 die_out_of_memory();
534 return fp;
535 }
536
537 void
tprintf(const char * fmt,...)538 tprintf(const char *fmt, ...)
539 {
540 va_list args;
541
542 va_start(args, fmt);
543 if (current_tcp) {
544 int n = strace_vfprintf(current_tcp->outf, fmt, args);
545 if (n < 0) {
546 if (current_tcp->outf != stderr)
547 perror_msg("%s", outfname);
548 } else
549 current_tcp->curcol += n;
550 }
551 va_end(args);
552 }
553
554 #ifndef HAVE_FPUTS_UNLOCKED
555 # define fputs_unlocked fputs
556 #endif
557
558 void
tprints(const char * str)559 tprints(const char *str)
560 {
561 if (current_tcp) {
562 int n = fputs_unlocked(str, current_tcp->outf);
563 if (n >= 0) {
564 current_tcp->curcol += strlen(str);
565 return;
566 }
567 if (current_tcp->outf != stderr)
568 perror_msg("%s", outfname);
569 }
570 }
571
572 void
line_ended(void)573 line_ended(void)
574 {
575 if (current_tcp) {
576 current_tcp->curcol = 0;
577 fflush(current_tcp->outf);
578 }
579 if (printing_tcp) {
580 printing_tcp->curcol = 0;
581 printing_tcp = NULL;
582 }
583 }
584
585 void
printleader(struct tcb * tcp)586 printleader(struct tcb *tcp)
587 {
588 /* If -ff, "previous tcb we printed" is always the same as current,
589 * because we have per-tcb output files.
590 */
591 if (followfork >= 2)
592 printing_tcp = tcp;
593
594 if (printing_tcp) {
595 current_tcp = printing_tcp;
596 if (printing_tcp->curcol != 0 && (followfork < 2 || printing_tcp == tcp)) {
597 /*
598 * case 1: we have a shared log (i.e. not -ff), and last line
599 * wasn't finished (same or different tcb, doesn't matter).
600 * case 2: split log, we are the same tcb, but our last line
601 * didn't finish ("SIGKILL nuked us after syscall entry" etc).
602 */
603 tprints(" <unfinished ...>\n");
604 printing_tcp->curcol = 0;
605 }
606 }
607
608 printing_tcp = tcp;
609 current_tcp = tcp;
610 current_tcp->curcol = 0;
611
612 if (print_pid_pfx)
613 tprintf("%-5d ", tcp->pid);
614 else if (nprocs > 1 && !outfname)
615 tprintf("[pid %5u] ", tcp->pid);
616
617 if (tflag) {
618 char str[sizeof("HH:MM:SS")];
619 struct timeval tv, dtv;
620 static struct timeval otv;
621
622 gettimeofday(&tv, NULL);
623 if (rflag) {
624 if (otv.tv_sec == 0)
625 otv = tv;
626 tv_sub(&dtv, &tv, &otv);
627 tprintf("%6ld.%06ld ",
628 (long) dtv.tv_sec, (long) dtv.tv_usec);
629 otv = tv;
630 }
631 else if (tflag > 2) {
632 tprintf("%ld.%06ld ",
633 (long) tv.tv_sec, (long) tv.tv_usec);
634 }
635 else {
636 time_t local = tv.tv_sec;
637 strftime(str, sizeof(str), "%T", localtime(&local));
638 if (tflag > 1)
639 tprintf("%s.%06ld ", str, (long) tv.tv_usec);
640 else
641 tprintf("%s ", str);
642 }
643 }
644 if (iflag)
645 print_pc(tcp);
646 }
647
648 void
tabto(void)649 tabto(void)
650 {
651 if (current_tcp->curcol < acolumn)
652 tprints(acolumn_spaces + current_tcp->curcol);
653 }
654
655 /* Should be only called directly *after successful attach* to a tracee.
656 * Otherwise, "strace -oFILE -ff -p<nonexistant_pid>"
657 * may create bogus empty FILE.<nonexistant_pid>, and then die.
658 */
659 static void
newoutf(struct tcb * tcp)660 newoutf(struct tcb *tcp)
661 {
662 tcp->outf = shared_log; /* if not -ff mode, the same file is for all */
663 if (followfork >= 2) {
664 char name[520 + sizeof(int) * 3];
665 sprintf(name, "%.512s.%u", outfname, tcp->pid);
666 tcp->outf = strace_fopen(name);
667 }
668 }
669
670 static void
expand_tcbtab(void)671 expand_tcbtab(void)
672 {
673 /* Allocate some more TCBs and expand the table.
674 We don't want to relocate the TCBs because our
675 callers have pointers and it would be a pain.
676 So tcbtab is a table of pointers. Since we never
677 free the TCBs, we allocate a single chunk of many. */
678 int i = tcbtabsize;
679 struct tcb *newtcbs = calloc(tcbtabsize, sizeof(newtcbs[0]));
680 struct tcb **newtab = realloc(tcbtab, tcbtabsize * 2 * sizeof(tcbtab[0]));
681 if (!newtab || !newtcbs)
682 die_out_of_memory();
683 tcbtabsize *= 2;
684 tcbtab = newtab;
685 while (i < tcbtabsize)
686 tcbtab[i++] = newtcbs++;
687 }
688
689 static struct tcb *
alloctcb(int pid)690 alloctcb(int pid)
691 {
692 int i;
693 struct tcb *tcp;
694
695 if (nprocs == tcbtabsize)
696 expand_tcbtab();
697
698 for (i = 0; i < tcbtabsize; i++) {
699 tcp = tcbtab[i];
700 if (!tcp->pid) {
701 memset(tcp, 0, sizeof(*tcp));
702 tcp->pid = pid;
703 #if SUPPORTED_PERSONALITIES > 1
704 tcp->currpers = current_personality;
705 #endif
706
707 #ifdef USE_LIBUNWIND
708 if (stack_trace_enabled)
709 unwind_tcb_init(tcp);
710 #endif
711
712 nprocs++;
713 if (debug_flag)
714 fprintf(stderr, "new tcb for pid %d, active tcbs:%d\n", tcp->pid, nprocs);
715 return tcp;
716 }
717 }
718 error_msg_and_die("bug in alloctcb");
719 }
720
721 static void
droptcb(struct tcb * tcp)722 droptcb(struct tcb *tcp)
723 {
724 if (tcp->pid == 0)
725 return;
726
727 #ifdef USE_LIBUNWIND
728 if (stack_trace_enabled) {
729 unwind_tcb_fin(tcp);
730 }
731 #endif
732
733 nprocs--;
734 if (debug_flag)
735 fprintf(stderr, "dropped tcb for pid %d, %d remain\n", tcp->pid, nprocs);
736
737 if (tcp->outf) {
738 if (followfork >= 2) {
739 if (tcp->curcol != 0)
740 fprintf(tcp->outf, " <detached ...>\n");
741 fclose(tcp->outf);
742 } else {
743 if (printing_tcp == tcp && tcp->curcol != 0)
744 fprintf(tcp->outf, " <detached ...>\n");
745 fflush(tcp->outf);
746 }
747 }
748
749 if (current_tcp == tcp)
750 current_tcp = NULL;
751 if (printing_tcp == tcp)
752 printing_tcp = NULL;
753
754 memset(tcp, 0, sizeof(*tcp));
755 }
756
757 /* Detach traced process.
758 * Never call DETACH twice on the same process as both unattached and
759 * attached-unstopped processes give the same ESRCH. For unattached process we
760 * would SIGSTOP it and wait for its SIGSTOP notification forever.
761 */
762 static void
detach(struct tcb * tcp)763 detach(struct tcb *tcp)
764 {
765 int error;
766 int status;
767
768 if (tcp->flags & TCB_BPTSET)
769 clearbpt(tcp);
770
771 /*
772 * Linux wrongly insists the child be stopped
773 * before detaching. Arghh. We go through hoops
774 * to make a clean break of things.
775 */
776 #if defined(SPARC)
777 # undef PTRACE_DETACH
778 # define PTRACE_DETACH PTRACE_SUNDETACH
779 #endif
780
781 if (!(tcp->flags & TCB_ATTACHED))
782 goto drop;
783
784 /* We attached but possibly didn't see the expected SIGSTOP.
785 * We must catch exactly one as otherwise the detached process
786 * would be left stopped (process state T).
787 */
788 if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
789 goto wait_loop;
790
791 error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
792 if (!error) {
793 /* On a clear day, you can see forever. */
794 goto drop;
795 }
796 if (errno != ESRCH) {
797 /* Shouldn't happen. */
798 perror_msg("detach: ptrace(PTRACE_DETACH,%u)", tcp->pid);
799 goto drop;
800 }
801 /* ESRCH: process is either not stopped or doesn't exist. */
802 if (my_tkill(tcp->pid, 0) < 0) {
803 if (errno != ESRCH)
804 /* Shouldn't happen. */
805 perror_msg("detach: tkill(%u,0)", tcp->pid);
806 /* else: process doesn't exist. */
807 goto drop;
808 }
809 /* Process is not stopped, need to stop it. */
810 if (use_seize) {
811 /*
812 * With SEIZE, tracee can be in group-stop already.
813 * In this state sending it another SIGSTOP does nothing.
814 * Need to use INTERRUPT.
815 * Testcase: trying to ^C a "strace -p <stopped_process>".
816 */
817 error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
818 if (!error)
819 goto wait_loop;
820 if (errno != ESRCH)
821 perror_msg("detach: ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
822 }
823 else {
824 error = my_tkill(tcp->pid, SIGSTOP);
825 if (!error)
826 goto wait_loop;
827 if (errno != ESRCH)
828 perror_msg("detach: tkill(%u,SIGSTOP)", tcp->pid);
829 }
830 /* Either process doesn't exist, or some weird error. */
831 goto drop;
832
833 wait_loop:
834 /* We end up here in three cases:
835 * 1. We sent PTRACE_INTERRUPT (use_seize case)
836 * 2. We sent SIGSTOP (!use_seize)
837 * 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
838 */
839 for (;;) {
840 int sig;
841 if (waitpid(tcp->pid, &status, __WALL) < 0) {
842 if (errno == EINTR)
843 continue;
844 /*
845 * if (errno == ECHILD) break;
846 * ^^^ WRONG! We expect this PID to exist,
847 * and want to emit a message otherwise:
848 */
849 perror_msg("detach: waitpid(%u)", tcp->pid);
850 break;
851 }
852 if (!WIFSTOPPED(status)) {
853 /*
854 * Tracee exited or was killed by signal.
855 * We shouldn't normally reach this place:
856 * we don't want to consume exit status.
857 * Consider "strace -p PID" being ^C-ed:
858 * we want merely to detach from PID.
859 *
860 * However, we _can_ end up here if tracee
861 * was SIGKILLed.
862 */
863 break;
864 }
865 sig = WSTOPSIG(status);
866 if (debug_flag)
867 fprintf(stderr, "detach wait: event:%d sig:%d\n",
868 (unsigned)status >> 16, sig);
869 if (use_seize) {
870 unsigned event = (unsigned)status >> 16;
871 if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
872 /*
873 * sig == SIGTRAP: PTRACE_INTERRUPT stop.
874 * sig == other: process was already stopped
875 * with this stopping sig (see tests/detach-stopped).
876 * Looks like re-injecting this sig is not necessary
877 * in DETACH for the tracee to remain stopped.
878 */
879 sig = 0;
880 }
881 /*
882 * PTRACE_INTERRUPT is not guaranteed to produce
883 * the above event if other ptrace-stop is pending.
884 * See tests/detach-sleeping testcase:
885 * strace got SIGINT while tracee is sleeping.
886 * We sent PTRACE_INTERRUPT.
887 * We see syscall exit, not PTRACE_INTERRUPT stop.
888 * We won't get PTRACE_INTERRUPT stop
889 * if we would CONT now. Need to DETACH.
890 */
891 if (sig == syscall_trap_sig)
892 sig = 0;
893 /* else: not sure in which case we can be here.
894 * Signal stop? Inject it while detaching.
895 */
896 ptrace_restart(PTRACE_DETACH, tcp, sig);
897 break;
898 }
899 /* Note: this check has to be after use_seize check */
900 /* (else, in use_seize case SIGSTOP will be mistreated) */
901 if (sig == SIGSTOP) {
902 /* Detach, suppressing SIGSTOP */
903 ptrace_restart(PTRACE_DETACH, tcp, 0);
904 break;
905 }
906 if (sig == syscall_trap_sig)
907 sig = 0;
908 /* Can't detach just yet, may need to wait for SIGSTOP */
909 error = ptrace_restart(PTRACE_CONT, tcp, sig);
910 if (error < 0) {
911 /* Should not happen.
912 * Note: ptrace_restart returns 0 on ESRCH, so it's not it.
913 * ptrace_restart already emitted error message.
914 */
915 break;
916 }
917 }
918
919 drop:
920 if (!qflag && (tcp->flags & TCB_ATTACHED))
921 fprintf(stderr, "Process %u detached\n", tcp->pid);
922
923 droptcb(tcp);
924 }
925
926 static void
process_opt_p_list(char * opt)927 process_opt_p_list(char *opt)
928 {
929 while (*opt) {
930 /*
931 * We accept -p PID,PID; -p "`pidof PROG`"; -p "`pgrep PROG`".
932 * pidof uses space as delim, pgrep uses newline. :(
933 */
934 int pid;
935 char *delim = opt + strcspn(opt, ", \n\t");
936 char c = *delim;
937
938 *delim = '\0';
939 pid = string_to_uint(opt);
940 if (pid <= 0) {
941 error_msg_and_die("Invalid process id: '%s'", opt);
942 }
943 if (pid == strace_tracer_pid) {
944 error_msg_and_die("I'm sorry, I can't let you do that, Dave.");
945 }
946 *delim = c;
947 alloctcb(pid);
948 if (c == '\0')
949 break;
950 opt = delim + 1;
951 }
952 }
953
954 static void
startup_attach(void)955 startup_attach(void)
956 {
957 int tcbi;
958 struct tcb *tcp;
959
960 /*
961 * Block user interruptions as we would leave the traced
962 * process stopped (process state T) if we would terminate in
963 * between PTRACE_ATTACH and wait4() on SIGSTOP.
964 * We rely on cleanup() from this point on.
965 */
966 if (interactive)
967 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
968
969 if (daemonized_tracer) {
970 pid_t pid = fork();
971 if (pid < 0) {
972 perror_msg_and_die("fork");
973 }
974 if (pid) { /* parent */
975 /*
976 * Wait for grandchild to attach to straced process
977 * (grandparent). Grandchild SIGKILLs us after it attached.
978 * Grandparent's wait() is unblocked by our death,
979 * it proceeds to exec the straced program.
980 */
981 pause();
982 _exit(0); /* paranoia */
983 }
984 /* grandchild */
985 /* We will be the tracer process. Remember our new pid: */
986 strace_tracer_pid = getpid();
987 }
988
989 for (tcbi = 0; tcbi < tcbtabsize; tcbi++) {
990 tcp = tcbtab[tcbi];
991
992 if (!tcp->pid)
993 continue;
994
995 /* Is this a process we should attach to, but not yet attached? */
996 if (tcp->flags & TCB_ATTACHED)
997 continue; /* no, we already attached it */
998
999 if (followfork && !daemonized_tracer) {
1000 char procdir[sizeof("/proc/%d/task") + sizeof(int) * 3];
1001 DIR *dir;
1002
1003 sprintf(procdir, "/proc/%d/task", tcp->pid);
1004 dir = opendir(procdir);
1005 if (dir != NULL) {
1006 unsigned int ntid = 0, nerr = 0;
1007 struct_dirent *de;
1008
1009 while ((de = read_dir(dir)) != NULL) {
1010 struct tcb *cur_tcp;
1011 int tid;
1012
1013 if (de->d_fileno == 0)
1014 continue;
1015 /* we trust /proc filesystem */
1016 tid = atoi(de->d_name);
1017 if (tid <= 0)
1018 continue;
1019 ++ntid;
1020 if (ptrace_attach_or_seize(tid) < 0) {
1021 ++nerr;
1022 if (debug_flag)
1023 fprintf(stderr, "attach to pid %d failed\n", tid);
1024 continue;
1025 }
1026 if (debug_flag)
1027 fprintf(stderr, "attach to pid %d succeeded\n", tid);
1028 cur_tcp = tcp;
1029 if (tid != tcp->pid)
1030 cur_tcp = alloctcb(tid);
1031 cur_tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1032 newoutf(cur_tcp);
1033 }
1034 closedir(dir);
1035 if (interactive) {
1036 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1037 if (interrupted)
1038 goto ret;
1039 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
1040 }
1041 ntid -= nerr;
1042 if (ntid == 0) {
1043 perror_msg("attach: ptrace(PTRACE_ATTACH, ...)");
1044 droptcb(tcp);
1045 continue;
1046 }
1047 if (!qflag) {
1048 fprintf(stderr, ntid > 1
1049 ? "Process %u attached with %u threads\n"
1050 : "Process %u attached\n",
1051 tcp->pid, ntid);
1052 }
1053 if (!(tcp->flags & TCB_ATTACHED)) {
1054 /* -p PID, we failed to attach to PID itself
1055 * but did attach to some of its sibling threads.
1056 * Drop PID's tcp.
1057 */
1058 droptcb(tcp);
1059 }
1060 continue;
1061 } /* if (opendir worked) */
1062 } /* if (-f) */
1063 if (ptrace_attach_or_seize(tcp->pid) < 0) {
1064 perror_msg("attach: ptrace(PTRACE_ATTACH, ...)");
1065 droptcb(tcp);
1066 continue;
1067 }
1068 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1069 newoutf(tcp);
1070 if (debug_flag)
1071 fprintf(stderr, "attach to pid %d (main) succeeded\n", tcp->pid);
1072
1073 if (daemonized_tracer) {
1074 /*
1075 * Make parent go away.
1076 * Also makes grandparent's wait() unblock.
1077 */
1078 kill(getppid(), SIGKILL);
1079 }
1080
1081 if (!qflag)
1082 fprintf(stderr,
1083 "Process %u attached\n",
1084 tcp->pid);
1085 } /* for each tcbtab[] */
1086
1087 ret:
1088 if (interactive)
1089 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1090 }
1091
1092 /* Stack-o-phobic exec helper, in the hope to work around
1093 * NOMMU + "daemonized tracer" difficulty.
1094 */
1095 struct exec_params {
1096 int fd_to_close;
1097 uid_t run_euid;
1098 gid_t run_egid;
1099 char **argv;
1100 char *pathname;
1101 };
1102 static struct exec_params params_for_tracee;
1103 static void __attribute__ ((noinline, noreturn))
exec_or_die(void)1104 exec_or_die(void)
1105 {
1106 struct exec_params *params = ¶ms_for_tracee;
1107
1108 if (params->fd_to_close >= 0)
1109 close(params->fd_to_close);
1110 if (!daemonized_tracer && !use_seize) {
1111 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0) {
1112 perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
1113 }
1114 }
1115
1116 if (username != NULL) {
1117 /*
1118 * It is important to set groups before we
1119 * lose privileges on setuid.
1120 */
1121 if (initgroups(username, run_gid) < 0) {
1122 perror_msg_and_die("initgroups");
1123 }
1124 if (setregid(run_gid, params->run_egid) < 0) {
1125 perror_msg_and_die("setregid");
1126 }
1127 if (setreuid(run_uid, params->run_euid) < 0) {
1128 perror_msg_and_die("setreuid");
1129 }
1130 }
1131 else if (geteuid() != 0)
1132 if (setreuid(run_uid, run_uid) < 0) {
1133 perror_msg_and_die("setreuid");
1134 }
1135
1136 if (!daemonized_tracer) {
1137 /*
1138 * Induce a ptrace stop. Tracer (our parent)
1139 * will resume us with PTRACE_SYSCALL and display
1140 * the immediately following execve syscall.
1141 * Can't do this on NOMMU systems, we are after
1142 * vfork: parent is blocked, stopping would deadlock.
1143 */
1144 if (!NOMMU_SYSTEM)
1145 kill(getpid(), SIGSTOP);
1146 } else {
1147 alarm(3);
1148 /* we depend on SIGCHLD set to SIG_DFL by init code */
1149 /* if it happens to be SIG_IGN'ed, wait won't block */
1150 wait(NULL);
1151 alarm(0);
1152 }
1153
1154 execv(params->pathname, params->argv);
1155 perror_msg_and_die("exec");
1156 }
1157
1158 static void
startup_child(char ** argv)1159 startup_child(char **argv)
1160 {
1161 struct_stat statbuf;
1162 const char *filename;
1163 char pathname[MAXPATHLEN];
1164 int pid;
1165 struct tcb *tcp;
1166
1167 filename = argv[0];
1168 if (strchr(filename, '/')) {
1169 if (strlen(filename) > sizeof pathname - 1) {
1170 errno = ENAMETOOLONG;
1171 perror_msg_and_die("exec");
1172 }
1173 strcpy(pathname, filename);
1174 }
1175 #ifdef USE_DEBUGGING_EXEC
1176 /*
1177 * Debuggers customarily check the current directory
1178 * first regardless of the path but doing that gives
1179 * security geeks a panic attack.
1180 */
1181 else if (stat_file(filename, &statbuf) == 0)
1182 strcpy(pathname, filename);
1183 #endif /* USE_DEBUGGING_EXEC */
1184 else {
1185 const char *path;
1186 int m, n, len;
1187
1188 for (path = getenv("PATH"); path && *path; path += m) {
1189 const char *colon = strchr(path, ':');
1190 if (colon) {
1191 n = colon - path;
1192 m = n + 1;
1193 }
1194 else
1195 m = n = strlen(path);
1196 if (n == 0) {
1197 if (!getcwd(pathname, MAXPATHLEN))
1198 continue;
1199 len = strlen(pathname);
1200 }
1201 else if (n > sizeof pathname - 1)
1202 continue;
1203 else {
1204 strncpy(pathname, path, n);
1205 len = n;
1206 }
1207 if (len && pathname[len - 1] != '/')
1208 pathname[len++] = '/';
1209 strcpy(pathname + len, filename);
1210 if (stat_file(pathname, &statbuf) == 0 &&
1211 /* Accept only regular files
1212 with some execute bits set.
1213 XXX not perfect, might still fail */
1214 S_ISREG(statbuf.st_mode) &&
1215 (statbuf.st_mode & 0111))
1216 break;
1217 }
1218 }
1219 if (stat_file(pathname, &statbuf) < 0) {
1220 perror_msg_and_die("Can't stat '%s'", filename);
1221 }
1222
1223 params_for_tracee.fd_to_close = (shared_log != stderr) ? fileno(shared_log) : -1;
1224 params_for_tracee.run_euid = (statbuf.st_mode & S_ISUID) ? statbuf.st_uid : run_uid;
1225 params_for_tracee.run_egid = (statbuf.st_mode & S_ISGID) ? statbuf.st_gid : run_gid;
1226 params_for_tracee.argv = argv;
1227 /*
1228 * On NOMMU, can be safely freed only after execve in tracee.
1229 * It's hard to know when that happens, so we just leak it.
1230 */
1231 params_for_tracee.pathname = NOMMU_SYSTEM ? strdup(pathname) : pathname;
1232
1233 #if defined HAVE_PRCTL && defined PR_SET_PTRACER && defined PR_SET_PTRACER_ANY
1234 if (daemonized_tracer)
1235 prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
1236 #endif
1237
1238 pid = fork();
1239 if (pid < 0) {
1240 perror_msg_and_die("fork");
1241 }
1242 if ((pid != 0 && daemonized_tracer)
1243 || (pid == 0 && !daemonized_tracer)
1244 ) {
1245 /* We are to become the tracee. Two cases:
1246 * -D: we are parent
1247 * not -D: we are child
1248 */
1249 exec_or_die();
1250 }
1251
1252 /* We are the tracer */
1253
1254 if (!daemonized_tracer) {
1255 strace_child = pid;
1256 if (!use_seize) {
1257 /* child did PTRACE_TRACEME, nothing to do in parent */
1258 } else {
1259 if (!NOMMU_SYSTEM) {
1260 /* Wait until child stopped itself */
1261 int status;
1262 while (waitpid(pid, &status, WSTOPPED) < 0) {
1263 if (errno == EINTR)
1264 continue;
1265 perror_msg_and_die("waitpid");
1266 }
1267 if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGSTOP) {
1268 kill_save_errno(pid, SIGKILL);
1269 perror_msg_and_die("Unexpected wait status %x", status);
1270 }
1271 }
1272 /* Else: NOMMU case, we have no way to sync.
1273 * Just attach to it as soon as possible.
1274 * This means that we may miss a few first syscalls...
1275 */
1276
1277 if (ptrace_attach_or_seize(pid)) {
1278 kill_save_errno(pid, SIGKILL);
1279 perror_msg_and_die("Can't attach to %d", pid);
1280 }
1281 if (!NOMMU_SYSTEM)
1282 kill(pid, SIGCONT);
1283 }
1284 tcp = alloctcb(pid);
1285 if (!NOMMU_SYSTEM)
1286 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1287 else
1288 tcp->flags |= TCB_ATTACHED | TCB_STARTUP;
1289 newoutf(tcp);
1290 }
1291 else {
1292 /* With -D, we are *child* here, IOW: different pid. Fetch it: */
1293 strace_tracer_pid = getpid();
1294 /* The tracee is our parent: */
1295 pid = getppid();
1296 alloctcb(pid);
1297 /* attaching will be done later, by startup_attach */
1298 /* note: we don't do newoutf(tcp) here either! */
1299
1300 /* NOMMU BUG! -D mode is active, we (child) return,
1301 * and we will scribble over parent's stack!
1302 * When parent later unpauses, it segfaults.
1303 *
1304 * We work around it
1305 * (1) by declaring exec_or_die() NORETURN,
1306 * hopefully compiler will just jump to it
1307 * instead of call (won't push anything to stack),
1308 * (2) by trying very hard in exec_or_die()
1309 * to not use any stack,
1310 * (3) having a really big (MAXPATHLEN) stack object
1311 * in this function, which creates a "buffer" between
1312 * child's and parent's stack pointers.
1313 * This may save us if (1) and (2) failed
1314 * and compiler decided to use stack in exec_or_die() anyway
1315 * (happens on i386 because of stack parameter passing).
1316 *
1317 * A cleaner solution is to use makecontext + setcontext
1318 * to create a genuine separate stack and execute on it.
1319 */
1320 }
1321 }
1322
1323 /*
1324 * Test whether the kernel support PTRACE_O_TRACECLONE et al options.
1325 * First fork a new child, call ptrace with PTRACE_SETOPTIONS on it,
1326 * and then see which options are supported by the kernel.
1327 */
1328 static int
test_ptrace_setoptions_followfork(void)1329 test_ptrace_setoptions_followfork(void)
1330 {
1331 int pid, expected_grandchild = 0, found_grandchild = 0;
1332 const unsigned int test_options = PTRACE_O_TRACECLONE |
1333 PTRACE_O_TRACEFORK |
1334 PTRACE_O_TRACEVFORK;
1335
1336 /* Need fork for test. NOMMU has no forks */
1337 if (NOMMU_SYSTEM)
1338 goto worked; /* be bold, and pretend that test succeeded */
1339
1340 pid = fork();
1341 if (pid < 0)
1342 perror_msg_and_die("fork");
1343 if (pid == 0) {
1344 pid = getpid();
1345 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0)
1346 perror_msg_and_die("%s: PTRACE_TRACEME doesn't work",
1347 __func__);
1348 kill_save_errno(pid, SIGSTOP);
1349 if (fork() < 0)
1350 perror_msg_and_die("fork");
1351 _exit(0);
1352 }
1353
1354 while (1) {
1355 int status, tracee_pid;
1356
1357 errno = 0;
1358 tracee_pid = wait(&status);
1359 if (tracee_pid <= 0) {
1360 if (errno == EINTR)
1361 continue;
1362 if (errno == ECHILD)
1363 break;
1364 kill_save_errno(pid, SIGKILL);
1365 perror_msg_and_die("%s: unexpected wait result %d",
1366 __func__, tracee_pid);
1367 }
1368 if (WIFEXITED(status)) {
1369 if (WEXITSTATUS(status)) {
1370 if (tracee_pid != pid)
1371 kill_save_errno(pid, SIGKILL);
1372 error_msg_and_die("%s: unexpected exit status %u",
1373 __func__, WEXITSTATUS(status));
1374 }
1375 continue;
1376 }
1377 if (WIFSIGNALED(status)) {
1378 if (tracee_pid != pid)
1379 kill_save_errno(pid, SIGKILL);
1380 error_msg_and_die("%s: unexpected signal %u",
1381 __func__, WTERMSIG(status));
1382 }
1383 if (!WIFSTOPPED(status)) {
1384 if (tracee_pid != pid)
1385 kill_save_errno(tracee_pid, SIGKILL);
1386 kill_save_errno(pid, SIGKILL);
1387 error_msg_and_die("%s: unexpected wait status %x",
1388 __func__, status);
1389 }
1390 if (tracee_pid != pid) {
1391 found_grandchild = tracee_pid;
1392 if (ptrace(PTRACE_CONT, tracee_pid, 0, 0) < 0) {
1393 kill_save_errno(tracee_pid, SIGKILL);
1394 kill_save_errno(pid, SIGKILL);
1395 perror_msg_and_die("PTRACE_CONT doesn't work");
1396 }
1397 continue;
1398 }
1399 switch (WSTOPSIG(status)) {
1400 case SIGSTOP:
1401 if (ptrace(PTRACE_SETOPTIONS, pid, 0, test_options) < 0
1402 && errno != EINVAL && errno != EIO)
1403 perror_msg("PTRACE_SETOPTIONS");
1404 break;
1405 case SIGTRAP:
1406 if (status >> 16 == PTRACE_EVENT_FORK) {
1407 long msg = 0;
1408
1409 if (ptrace(PTRACE_GETEVENTMSG, pid,
1410 NULL, (long) &msg) == 0)
1411 expected_grandchild = msg;
1412 }
1413 break;
1414 }
1415 if (ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0) {
1416 kill_save_errno(pid, SIGKILL);
1417 perror_msg_and_die("PTRACE_SYSCALL doesn't work");
1418 }
1419 }
1420 if (expected_grandchild && expected_grandchild == found_grandchild) {
1421 worked:
1422 ptrace_setoptions |= test_options;
1423 if (debug_flag)
1424 fprintf(stderr, "ptrace_setoptions = %#x\n",
1425 ptrace_setoptions);
1426 return 0;
1427 }
1428 error_msg("Test for PTRACE_O_TRACECLONE failed, "
1429 "giving up using this feature.");
1430 return 1;
1431 }
1432
1433 /*
1434 * Test whether the kernel support PTRACE_O_TRACESYSGOOD.
1435 * First fork a new child, call ptrace(PTRACE_SETOPTIONS) on it,
1436 * and then see whether it will stop with (SIGTRAP | 0x80).
1437 *
1438 * Use of this option enables correct handling of user-generated SIGTRAPs,
1439 * and SIGTRAPs generated by special instructions such as int3 on x86:
1440
1441 # compile with: gcc -nostartfiles -nostdlib -o int3 int3.S
1442 _start: .globl _start
1443 int3
1444 movl $42, %ebx
1445 movl $1, %eax
1446 int $0x80
1447 */
1448 static int
test_ptrace_setoptions_for_all(void)1449 test_ptrace_setoptions_for_all(void)
1450 {
1451 const unsigned int test_options = PTRACE_O_TRACESYSGOOD |
1452 PTRACE_O_TRACEEXEC;
1453 int pid;
1454 int it_worked = 0;
1455
1456 /* Need fork for test. NOMMU has no forks */
1457 if (NOMMU_SYSTEM)
1458 goto worked; /* be bold, and pretend that test succeeded */
1459
1460 pid = fork();
1461 if (pid < 0)
1462 perror_msg_and_die("fork");
1463
1464 if (pid == 0) {
1465 pid = getpid();
1466 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0)
1467 /* Note: exits with exitcode 1 */
1468 perror_msg_and_die("%s: PTRACE_TRACEME doesn't work",
1469 __func__);
1470 kill(pid, SIGSTOP);
1471 _exit(0); /* parent should see entry into this syscall */
1472 }
1473
1474 while (1) {
1475 int status, tracee_pid;
1476
1477 errno = 0;
1478 tracee_pid = wait(&status);
1479 if (tracee_pid <= 0) {
1480 if (errno == EINTR)
1481 continue;
1482 kill_save_errno(pid, SIGKILL);
1483 perror_msg_and_die("%s: unexpected wait result %d",
1484 __func__, tracee_pid);
1485 }
1486 if (WIFEXITED(status)) {
1487 if (WEXITSTATUS(status) == 0)
1488 break;
1489 error_msg_and_die("%s: unexpected exit status %u",
1490 __func__, WEXITSTATUS(status));
1491 }
1492 if (WIFSIGNALED(status)) {
1493 error_msg_and_die("%s: unexpected signal %u",
1494 __func__, WTERMSIG(status));
1495 }
1496 if (!WIFSTOPPED(status)) {
1497 kill(pid, SIGKILL);
1498 error_msg_and_die("%s: unexpected wait status %x",
1499 __func__, status);
1500 }
1501 if (WSTOPSIG(status) == SIGSTOP) {
1502 /*
1503 * We don't check "options aren't accepted" error.
1504 * If it happens, we'll never get (SIGTRAP | 0x80),
1505 * and thus will decide to not use the option.
1506 * IOW: the outcome of the test will be correct.
1507 */
1508 if (ptrace(PTRACE_SETOPTIONS, pid, 0L, test_options) < 0
1509 && errno != EINVAL && errno != EIO)
1510 perror_msg("PTRACE_SETOPTIONS");
1511 }
1512 if (WSTOPSIG(status) == (SIGTRAP | 0x80)) {
1513 it_worked = 1;
1514 }
1515 if (ptrace(PTRACE_SYSCALL, pid, 0L, 0L) < 0) {
1516 kill_save_errno(pid, SIGKILL);
1517 perror_msg_and_die("PTRACE_SYSCALL doesn't work");
1518 }
1519 }
1520
1521 if (it_worked) {
1522 worked:
1523 syscall_trap_sig = (SIGTRAP | 0x80);
1524 ptrace_setoptions |= test_options;
1525 if (debug_flag)
1526 fprintf(stderr, "ptrace_setoptions = %#x\n",
1527 ptrace_setoptions);
1528 return 0;
1529 }
1530
1531 error_msg("Test for PTRACE_O_TRACESYSGOOD failed, "
1532 "giving up using this feature.");
1533 return 1;
1534 }
1535
1536 #if USE_SEIZE
1537 static void
test_ptrace_seize(void)1538 test_ptrace_seize(void)
1539 {
1540 int pid;
1541
1542 /* Need fork for test. NOMMU has no forks */
1543 if (NOMMU_SYSTEM) {
1544 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1545 return;
1546 }
1547
1548 pid = fork();
1549 if (pid < 0)
1550 perror_msg_and_die("fork");
1551
1552 if (pid == 0) {
1553 pause();
1554 _exit(0);
1555 }
1556
1557 /* PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After
1558 * attaching tracee continues to run unless a trap condition occurs.
1559 * PTRACE_SEIZE doesn't affect signal or group stop state.
1560 */
1561 if (ptrace(PTRACE_SEIZE, pid, 0, 0) == 0) {
1562 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1563 } else if (debug_flag) {
1564 fprintf(stderr, "PTRACE_SEIZE doesn't work\n");
1565 }
1566
1567 kill(pid, SIGKILL);
1568
1569 while (1) {
1570 int status, tracee_pid;
1571
1572 errno = 0;
1573 tracee_pid = waitpid(pid, &status, 0);
1574 if (tracee_pid <= 0) {
1575 if (errno == EINTR)
1576 continue;
1577 perror_msg_and_die("%s: unexpected wait result %d",
1578 __func__, tracee_pid);
1579 }
1580 if (WIFSIGNALED(status)) {
1581 return;
1582 }
1583 error_msg_and_die("%s: unexpected wait status %x",
1584 __func__, status);
1585 }
1586 }
1587 #else /* !USE_SEIZE */
1588 # define test_ptrace_seize() ((void)0)
1589 #endif
1590
1591 static unsigned
get_os_release(void)1592 get_os_release(void)
1593 {
1594 unsigned rel;
1595 const char *p;
1596 struct utsname u;
1597 if (uname(&u) < 0)
1598 perror_msg_and_die("uname");
1599 /* u.release has this form: "3.2.9[-some-garbage]" */
1600 rel = 0;
1601 p = u.release;
1602 for (;;) {
1603 if (!(*p >= '0' && *p <= '9'))
1604 error_msg_and_die("Bad OS release string: '%s'", u.release);
1605 /* Note: this open-codes KERNEL_VERSION(): */
1606 rel = (rel << 8) | atoi(p);
1607 if (rel >= KERNEL_VERSION(1,0,0))
1608 break;
1609 while (*p >= '0' && *p <= '9')
1610 p++;
1611 if (*p != '.') {
1612 if (rel >= KERNEL_VERSION(0,1,0)) {
1613 /* "X.Y-something" means "X.Y.0" */
1614 rel <<= 8;
1615 break;
1616 }
1617 error_msg_and_die("Bad OS release string: '%s'", u.release);
1618 }
1619 p++;
1620 }
1621 return rel;
1622 }
1623
1624 /*
1625 * Initialization part of main() was eating much stack (~0.5k),
1626 * which was unused after init.
1627 * We can reuse it if we move init code into a separate function.
1628 *
1629 * Don't want main() to inline us and defeat the reason
1630 * we have a separate function.
1631 */
1632 static void __attribute__ ((noinline))
init(int argc,char * argv[])1633 init(int argc, char *argv[])
1634 {
1635 struct tcb *tcp;
1636 int c, i;
1637 int optF = 0;
1638 struct sigaction sa;
1639
1640 progname = argv[0] ? argv[0] : "strace";
1641
1642 /* Make sure SIGCHLD has the default action so that waitpid
1643 definitely works without losing track of children. The user
1644 should not have given us a bogus state to inherit, but he might
1645 have. Arguably we should detect SIG_IGN here and pass it on
1646 to children, but probably noone really needs that. */
1647 signal(SIGCHLD, SIG_DFL);
1648
1649 strace_tracer_pid = getpid();
1650
1651 os_release = get_os_release();
1652
1653 /* Allocate the initial tcbtab. */
1654 tcbtabsize = argc; /* Surely enough for all -p args. */
1655 tcbtab = calloc(tcbtabsize, sizeof(tcbtab[0]));
1656 if (!tcbtab)
1657 die_out_of_memory();
1658 tcp = calloc(tcbtabsize, sizeof(*tcp));
1659 if (!tcp)
1660 die_out_of_memory();
1661 for (c = 0; c < tcbtabsize; c++)
1662 tcbtab[c] = tcp++;
1663
1664 shared_log = stderr;
1665 set_sortby(DEFAULT_SORTBY);
1666 set_personality(DEFAULT_PERSONALITY);
1667 qualify("trace=all");
1668 qualify("abbrev=all");
1669 qualify("verbose=all");
1670 #if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
1671 # error Bug in DEFAULT_QUAL_FLAGS
1672 #endif
1673 qualify("signal=all");
1674 while ((c = getopt(argc, argv,
1675 "+b:cCdfFhiqrtTvVwxyz"
1676 #ifdef USE_LIBUNWIND
1677 "k"
1678 #endif
1679 "D"
1680 "a:e:o:O:p:s:S:u:E:P:I:")) != EOF) {
1681 switch (c) {
1682 case 'b':
1683 if (strcmp(optarg, "execve") != 0)
1684 error_msg_and_die("Syscall '%s' for -b isn't supported",
1685 optarg);
1686 detach_on_execve = 1;
1687 break;
1688 case 'c':
1689 if (cflag == CFLAG_BOTH) {
1690 error_msg_and_die("-c and -C are mutually exclusive");
1691 }
1692 cflag = CFLAG_ONLY_STATS;
1693 break;
1694 case 'C':
1695 if (cflag == CFLAG_ONLY_STATS) {
1696 error_msg_and_die("-c and -C are mutually exclusive");
1697 }
1698 cflag = CFLAG_BOTH;
1699 break;
1700 case 'd':
1701 debug_flag = 1;
1702 break;
1703 case 'D':
1704 daemonized_tracer = 1;
1705 break;
1706 case 'F':
1707 optF = 1;
1708 break;
1709 case 'f':
1710 followfork++;
1711 break;
1712 case 'h':
1713 usage(stdout, 0);
1714 break;
1715 case 'i':
1716 iflag = 1;
1717 break;
1718 case 'q':
1719 qflag++;
1720 break;
1721 case 'r':
1722 rflag = 1;
1723 /* fall through to tflag++ */
1724 case 't':
1725 tflag++;
1726 break;
1727 case 'T':
1728 Tflag = 1;
1729 break;
1730 case 'w':
1731 count_wallclock = 1;
1732 break;
1733 case 'x':
1734 xflag++;
1735 break;
1736 case 'y':
1737 show_fd_path = 1;
1738 break;
1739 case 'v':
1740 qualify("abbrev=none");
1741 break;
1742 case 'V':
1743 printf("%s -- version %s\n", PACKAGE_NAME, VERSION);
1744 exit(0);
1745 break;
1746 case 'z':
1747 not_failing_only = 1;
1748 break;
1749 case 'a':
1750 acolumn = string_to_uint(optarg);
1751 if (acolumn < 0)
1752 error_opt_arg(c, optarg);
1753 break;
1754 case 'e':
1755 qualify(optarg);
1756 break;
1757 case 'o':
1758 outfname = strdup(optarg);
1759 break;
1760 case 'O':
1761 i = string_to_uint(optarg);
1762 if (i < 0)
1763 error_opt_arg(c, optarg);
1764 set_overhead(i);
1765 break;
1766 case 'p':
1767 process_opt_p_list(optarg);
1768 break;
1769 case 'P':
1770 pathtrace_select(optarg);
1771 break;
1772 case 's':
1773 i = string_to_uint(optarg);
1774 if (i < 0)
1775 error_opt_arg(c, optarg);
1776 max_strlen = i;
1777 break;
1778 case 'S':
1779 set_sortby(optarg);
1780 break;
1781 case 'u':
1782 username = strdup(optarg);
1783 break;
1784 #ifdef USE_LIBUNWIND
1785 case 'k':
1786 stack_trace_enabled = true;
1787 break;
1788 #endif
1789 case 'E':
1790 if (putenv(optarg) < 0)
1791 die_out_of_memory();
1792 break;
1793 case 'I':
1794 opt_intr = string_to_uint(optarg);
1795 if (opt_intr <= 0 || opt_intr >= NUM_INTR_OPTS)
1796 error_opt_arg(c, optarg);
1797 break;
1798 default:
1799 usage(stderr, 1);
1800 break;
1801 }
1802 }
1803 argv += optind;
1804 /* argc -= optind; - no need, argc is not used below */
1805
1806 acolumn_spaces = malloc(acolumn + 1);
1807 if (!acolumn_spaces)
1808 die_out_of_memory();
1809 memset(acolumn_spaces, ' ', acolumn);
1810 acolumn_spaces[acolumn] = '\0';
1811
1812 /* Must have PROG [ARGS], or -p PID. Not both. */
1813 if (!argv[0] == !nprocs)
1814 usage(stderr, 1);
1815
1816 if (nprocs != 0 && daemonized_tracer) {
1817 error_msg_and_die("-D and -p are mutually exclusive");
1818 }
1819
1820 if (!followfork)
1821 followfork = optF;
1822
1823 if (followfork >= 2 && cflag) {
1824 error_msg_and_die("(-c or -C) and -ff are mutually exclusive");
1825 }
1826
1827 if (count_wallclock && !cflag) {
1828 error_msg_and_die("-w must be given with (-c or -C)");
1829 }
1830
1831 if (cflag == CFLAG_ONLY_STATS) {
1832 if (iflag)
1833 error_msg("-%c has no effect with -c", 'i');
1834 #ifdef USE_LIBUNWIND
1835 if (stack_trace_enabled)
1836 error_msg("-%c has no effect with -c", 'k');
1837 #endif
1838 if (rflag)
1839 error_msg("-%c has no effect with -c", 'r');
1840 if (tflag)
1841 error_msg("-%c has no effect with -c", 't');
1842 if (Tflag)
1843 error_msg("-%c has no effect with -c", 'T');
1844 if (show_fd_path)
1845 error_msg("-%c has no effect with -c", 'y');
1846 }
1847
1848 #ifdef USE_LIBUNWIND
1849 if (stack_trace_enabled)
1850 unwind_init();
1851 #endif
1852
1853 /* See if they want to run as another user. */
1854 if (username != NULL) {
1855 struct passwd *pent;
1856
1857 if (getuid() != 0 || geteuid() != 0) {
1858 error_msg_and_die("You must be root to use the -u option");
1859 }
1860 pent = getpwnam(username);
1861 if (pent == NULL) {
1862 error_msg_and_die("Cannot find user '%s'", username);
1863 }
1864 run_uid = pent->pw_uid;
1865 run_gid = pent->pw_gid;
1866 }
1867 else {
1868 run_uid = getuid();
1869 run_gid = getgid();
1870 }
1871
1872 /*
1873 * On any reasonably recent Linux kernel (circa about 2.5.46)
1874 * need_fork_exec_workarounds should stay 0 after these tests:
1875 */
1876 /*need_fork_exec_workarounds = 0; - already is */
1877 if (followfork)
1878 need_fork_exec_workarounds = test_ptrace_setoptions_followfork();
1879 need_fork_exec_workarounds |= test_ptrace_setoptions_for_all();
1880 test_ptrace_seize();
1881
1882 /* Check if they want to redirect the output. */
1883 if (outfname) {
1884 /* See if they want to pipe the output. */
1885 if (outfname[0] == '|' || outfname[0] == '!') {
1886 /*
1887 * We can't do the <outfname>.PID funny business
1888 * when using popen, so prohibit it.
1889 */
1890 if (followfork >= 2)
1891 error_msg_and_die("Piping the output and -ff are mutually exclusive");
1892 shared_log = strace_popen(outfname + 1);
1893 }
1894 else if (followfork < 2)
1895 shared_log = strace_fopen(outfname);
1896 } else {
1897 /* -ff without -o FILE is the same as single -f */
1898 if (followfork >= 2)
1899 followfork = 1;
1900 }
1901
1902 if (!outfname || outfname[0] == '|' || outfname[0] == '!') {
1903 char *buf = malloc(BUFSIZ);
1904 if (!buf)
1905 die_out_of_memory();
1906 setvbuf(shared_log, buf, _IOLBF, BUFSIZ);
1907 }
1908 if (outfname && argv[0]) {
1909 if (!opt_intr)
1910 opt_intr = INTR_NEVER;
1911 qflag = 1;
1912 }
1913 if (!opt_intr)
1914 opt_intr = INTR_WHILE_WAIT;
1915
1916 /* argv[0] -pPID -oFILE Default interactive setting
1917 * yes 0 0 INTR_WHILE_WAIT
1918 * no 1 0 INTR_WHILE_WAIT
1919 * yes 0 1 INTR_NEVER
1920 * no 1 1 INTR_WHILE_WAIT
1921 */
1922
1923 sigemptyset(&empty_set);
1924 sigemptyset(&blocked_set);
1925
1926 /* startup_child() must be called before the signal handlers get
1927 * installed below as they are inherited into the spawned process.
1928 * Also we do not need to be protected by them as during interruption
1929 * in the startup_child() mode we kill the spawned process anyway.
1930 */
1931 if (argv[0]) {
1932 if (!NOMMU_SYSTEM || daemonized_tracer)
1933 hide_log_until_execve = 1;
1934 skip_one_b_execve = 1;
1935 startup_child(argv);
1936 }
1937
1938 sa.sa_handler = SIG_IGN;
1939 sigemptyset(&sa.sa_mask);
1940 sa.sa_flags = 0;
1941 sigaction(SIGTTOU, &sa, NULL); /* SIG_IGN */
1942 sigaction(SIGTTIN, &sa, NULL); /* SIG_IGN */
1943 if (opt_intr != INTR_ANYWHERE) {
1944 if (opt_intr == INTR_BLOCK_TSTP_TOO)
1945 sigaction(SIGTSTP, &sa, NULL); /* SIG_IGN */
1946 /*
1947 * In interactive mode (if no -o OUTFILE, or -p PID is used),
1948 * fatal signals are blocked while syscall stop is processed,
1949 * and acted on in between, when waiting for new syscall stops.
1950 * In non-interactive mode, signals are ignored.
1951 */
1952 if (opt_intr == INTR_WHILE_WAIT) {
1953 sigaddset(&blocked_set, SIGHUP);
1954 sigaddset(&blocked_set, SIGINT);
1955 sigaddset(&blocked_set, SIGQUIT);
1956 sigaddset(&blocked_set, SIGPIPE);
1957 sigaddset(&blocked_set, SIGTERM);
1958 sa.sa_handler = interrupt;
1959 }
1960 /* SIG_IGN, or set handler for these */
1961 sigaction(SIGHUP, &sa, NULL);
1962 sigaction(SIGINT, &sa, NULL);
1963 sigaction(SIGQUIT, &sa, NULL);
1964 sigaction(SIGPIPE, &sa, NULL);
1965 sigaction(SIGTERM, &sa, NULL);
1966 }
1967 if (nprocs != 0 || daemonized_tracer)
1968 startup_attach();
1969
1970 /* Do we want pids printed in our -o OUTFILE?
1971 * -ff: no (every pid has its own file); or
1972 * -f: yes (there can be more pids in the future); or
1973 * -p PID1,PID2: yes (there are already more than one pid)
1974 */
1975 print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
1976 }
1977
1978 static struct tcb *
pid2tcb(int pid)1979 pid2tcb(int pid)
1980 {
1981 int i;
1982
1983 if (pid <= 0)
1984 return NULL;
1985
1986 for (i = 0; i < tcbtabsize; i++) {
1987 struct tcb *tcp = tcbtab[i];
1988 if (tcp->pid == pid)
1989 return tcp;
1990 }
1991
1992 return NULL;
1993 }
1994
1995 static void
cleanup(void)1996 cleanup(void)
1997 {
1998 int i;
1999 struct tcb *tcp;
2000 int fatal_sig;
2001
2002 /* 'interrupted' is a volatile object, fetch it only once */
2003 fatal_sig = interrupted;
2004 if (!fatal_sig)
2005 fatal_sig = SIGTERM;
2006
2007 for (i = 0; i < tcbtabsize; i++) {
2008 tcp = tcbtab[i];
2009 if (!tcp->pid)
2010 continue;
2011 if (debug_flag)
2012 fprintf(stderr,
2013 "cleanup: looking at pid %u\n", tcp->pid);
2014 if (tcp->pid == strace_child) {
2015 kill(tcp->pid, SIGCONT);
2016 kill(tcp->pid, fatal_sig);
2017 }
2018 detach(tcp);
2019 }
2020 if (cflag)
2021 call_summary(shared_log);
2022 }
2023
2024 static void
interrupt(int sig)2025 interrupt(int sig)
2026 {
2027 interrupted = sig;
2028 }
2029
2030 static void
trace(void)2031 trace(void)
2032 {
2033 struct rusage ru;
2034
2035 /* Used to be "while (nprocs != 0)", but in this testcase:
2036 * int main() { _exit(!!fork()); }
2037 * under strace -f, parent sometimes (rarely) manages
2038 * to exit before we see the first stop of the child,
2039 * and we are losing track of it:
2040 * 19923 clone(...) = 19924
2041 * 19923 exit_group(1) = ?
2042 * 19923 +++ exited with 1 +++
2043 * Waiting for ECHILD works better.
2044 * (However, if -o|logger is in use, we can't do that.
2045 * Can work around that by double-forking the logger,
2046 * but that loses the ability to wait for its completion on exit.
2047 * Oh well...)
2048 */
2049 while (1) {
2050 int pid;
2051 int wait_errno;
2052 int status, sig;
2053 int stopped;
2054 struct tcb *tcp;
2055 unsigned event;
2056
2057 if (interrupted)
2058 return;
2059
2060 if (popen_pid != 0 && nprocs == 0)
2061 return;
2062
2063 if (interactive)
2064 sigprocmask(SIG_SETMASK, &empty_set, NULL);
2065 pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
2066 wait_errno = errno;
2067 if (interactive)
2068 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
2069
2070 if (pid < 0) {
2071 if (wait_errno == EINTR)
2072 continue;
2073 if (nprocs == 0 && wait_errno == ECHILD)
2074 return;
2075 /* If nprocs > 0, ECHILD is not expected,
2076 * treat it as any other error here:
2077 */
2078 errno = wait_errno;
2079 perror_msg_and_die("wait4(__WALL)");
2080 }
2081
2082 if (pid == popen_pid) {
2083 if (!WIFSTOPPED(status))
2084 popen_pid = 0;
2085 continue;
2086 }
2087
2088 event = ((unsigned)status >> 16);
2089 if (debug_flag) {
2090 char buf[sizeof("WIFEXITED,exitcode=%u") + sizeof(int)*3 /*paranoia:*/ + 16];
2091 char evbuf[sizeof(",EVENT_VFORK_DONE (%u)") + sizeof(int)*3 /*paranoia:*/ + 16];
2092 strcpy(buf, "???");
2093 if (WIFSIGNALED(status))
2094 #ifdef WCOREDUMP
2095 sprintf(buf, "WIFSIGNALED,%ssig=%s",
2096 WCOREDUMP(status) ? "core," : "",
2097 signame(WTERMSIG(status)));
2098 #else
2099 sprintf(buf, "WIFSIGNALED,sig=%s",
2100 signame(WTERMSIG(status)));
2101 #endif
2102 if (WIFEXITED(status))
2103 sprintf(buf, "WIFEXITED,exitcode=%u", WEXITSTATUS(status));
2104 if (WIFSTOPPED(status))
2105 sprintf(buf, "WIFSTOPPED,sig=%s", signame(WSTOPSIG(status)));
2106 #ifdef WIFCONTINUED
2107 /* Should never be seen */
2108 if (WIFCONTINUED(status))
2109 strcpy(buf, "WIFCONTINUED");
2110 #endif
2111 evbuf[0] = '\0';
2112 if (event != 0) {
2113 static const char *const event_names[] = {
2114 [PTRACE_EVENT_CLONE] = "CLONE",
2115 [PTRACE_EVENT_FORK] = "FORK",
2116 [PTRACE_EVENT_VFORK] = "VFORK",
2117 [PTRACE_EVENT_VFORK_DONE] = "VFORK_DONE",
2118 [PTRACE_EVENT_EXEC] = "EXEC",
2119 [PTRACE_EVENT_EXIT] = "EXIT",
2120 /* [PTRACE_EVENT_STOP (=128)] would make biggish array */
2121 };
2122 const char *e = "??";
2123 if (event < ARRAY_SIZE(event_names))
2124 e = event_names[event];
2125 else if (event == PTRACE_EVENT_STOP)
2126 e = "STOP";
2127 sprintf(evbuf, ",EVENT_%s (%u)", e, event);
2128 }
2129 fprintf(stderr, " [wait(0x%06x) = %u] %s%s\n", status, pid, buf, evbuf);
2130 }
2131
2132 /* Look up 'pid' in our table. */
2133 tcp = pid2tcb(pid);
2134
2135 if (!tcp) {
2136 if (!WIFSTOPPED(status)) {
2137 /* This can happen if we inherited
2138 * an unknown child. Example:
2139 * (sleep 1 & exec strace sleep 2)
2140 */
2141 error_msg("Exit of unknown pid %u seen", pid);
2142 continue;
2143 }
2144 if (followfork) {
2145 /* We assume it's a fork/vfork/clone child */
2146 tcp = alloctcb(pid);
2147 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
2148 newoutf(tcp);
2149 if (!qflag)
2150 fprintf(stderr, "Process %d attached\n",
2151 pid);
2152 } else {
2153 /* This can happen if a clone call used
2154 * CLONE_PTRACE itself.
2155 */
2156 ptrace(PTRACE_CONT, pid, (char *) 0, 0);
2157 error_msg("Stop of unknown pid %u seen, PTRACE_CONTed it", pid);
2158 continue;
2159 }
2160 }
2161
2162 clear_regs();
2163 if (WIFSTOPPED(status))
2164 get_regs(pid);
2165
2166 /* Under Linux, execve changes pid to thread leader's pid,
2167 * and we see this changed pid on EVENT_EXEC and later,
2168 * execve sysexit. Leader "disappears" without exit
2169 * notification. Let user know that, drop leader's tcb,
2170 * and fix up pid in execve thread's tcb.
2171 * Effectively, execve thread's tcb replaces leader's tcb.
2172 *
2173 * BTW, leader is 'stuck undead' (doesn't report WIFEXITED
2174 * on exit syscall) in multithreaded programs exactly
2175 * in order to handle this case.
2176 *
2177 * PTRACE_GETEVENTMSG returns old pid starting from Linux 3.0.
2178 * On 2.6 and earlier, it can return garbage.
2179 */
2180 if (event == PTRACE_EVENT_EXEC && os_release >= KERNEL_VERSION(3,0,0)) {
2181 FILE *fp;
2182 struct tcb *execve_thread;
2183 long old_pid = 0;
2184
2185 if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, (long) &old_pid) < 0)
2186 goto dont_switch_tcbs;
2187 /* Avoid truncation in pid2tcb() param passing */
2188 if (old_pid > UINT_MAX)
2189 goto dont_switch_tcbs;
2190 if (old_pid <= 0 || old_pid == pid)
2191 goto dont_switch_tcbs;
2192 execve_thread = pid2tcb(old_pid);
2193 /* It should be !NULL, but I feel paranoid */
2194 if (!execve_thread)
2195 goto dont_switch_tcbs;
2196
2197 if (execve_thread->curcol != 0) {
2198 /*
2199 * One case we are here is -ff:
2200 * try "strace -oLOG -ff test/threaded_execve"
2201 */
2202 fprintf(execve_thread->outf, " <pid changed to %d ...>\n", pid);
2203 /*execve_thread->curcol = 0; - no need, see code below */
2204 }
2205 /* Swap output FILEs (needed for -ff) */
2206 fp = execve_thread->outf;
2207 execve_thread->outf = tcp->outf;
2208 tcp->outf = fp;
2209 /* And their column positions */
2210 execve_thread->curcol = tcp->curcol;
2211 tcp->curcol = 0;
2212 /* Drop leader, but close execve'd thread outfile (if -ff) */
2213 droptcb(tcp);
2214 /* Switch to the thread, reusing leader's outfile and pid */
2215 tcp = execve_thread;
2216 tcp->pid = pid;
2217 if (cflag != CFLAG_ONLY_STATS) {
2218 printleader(tcp);
2219 tprintf("+++ superseded by execve in pid %lu +++\n", old_pid);
2220 line_ended();
2221 tcp->flags |= TCB_REPRINT;
2222 }
2223 }
2224 dont_switch_tcbs:
2225
2226 if (event == PTRACE_EVENT_EXEC) {
2227 if (detach_on_execve && !skip_one_b_execve)
2228 detach(tcp); /* do "-b execve" thingy */
2229 skip_one_b_execve = 0;
2230 }
2231
2232 /* Set current output file */
2233 current_tcp = tcp;
2234
2235 if (cflag) {
2236 tv_sub(&tcp->dtime, &ru.ru_stime, &tcp->stime);
2237 tcp->stime = ru.ru_stime;
2238 }
2239
2240 if (WIFSIGNALED(status)) {
2241 if (pid == strace_child)
2242 exit_code = 0x100 | WTERMSIG(status);
2243 if (cflag != CFLAG_ONLY_STATS
2244 && (qual_flags[WTERMSIG(status)] & QUAL_SIGNAL)
2245 ) {
2246 printleader(tcp);
2247 #ifdef WCOREDUMP
2248 tprintf("+++ killed by %s %s+++\n",
2249 signame(WTERMSIG(status)),
2250 WCOREDUMP(status) ? "(core dumped) " : "");
2251 #else
2252 tprintf("+++ killed by %s +++\n",
2253 signame(WTERMSIG(status)));
2254 #endif
2255 line_ended();
2256 }
2257 droptcb(tcp);
2258 continue;
2259 }
2260 if (WIFEXITED(status)) {
2261 if (pid == strace_child)
2262 exit_code = WEXITSTATUS(status);
2263 if (cflag != CFLAG_ONLY_STATS &&
2264 qflag < 2) {
2265 printleader(tcp);
2266 tprintf("+++ exited with %d +++\n", WEXITSTATUS(status));
2267 line_ended();
2268 }
2269 droptcb(tcp);
2270 continue;
2271 }
2272 if (!WIFSTOPPED(status)) {
2273 fprintf(stderr, "PANIC: pid %u not stopped\n", pid);
2274 droptcb(tcp);
2275 continue;
2276 }
2277
2278 /* Is this the very first time we see this tracee stopped? */
2279 if (tcp->flags & TCB_STARTUP) {
2280 if (debug_flag)
2281 fprintf(stderr, "pid %d has TCB_STARTUP, initializing it\n", tcp->pid);
2282 tcp->flags &= ~TCB_STARTUP;
2283 if (tcp->flags & TCB_BPTSET) {
2284 /*
2285 * One example is a breakpoint inherited from
2286 * parent through fork().
2287 */
2288 if (clearbpt(tcp) < 0) {
2289 /* Pretty fatal */
2290 droptcb(tcp);
2291 exit_code = 1;
2292 return;
2293 }
2294 }
2295 if (!use_seize && ptrace_setoptions) {
2296 if (debug_flag)
2297 fprintf(stderr, "setting opts 0x%x on pid %d\n", ptrace_setoptions, tcp->pid);
2298 if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, ptrace_setoptions) < 0) {
2299 if (errno != ESRCH) {
2300 /* Should never happen, really */
2301 perror_msg_and_die("PTRACE_SETOPTIONS");
2302 }
2303 }
2304 }
2305 }
2306
2307 sig = WSTOPSIG(status);
2308
2309 if (event != 0) {
2310 /* Ptrace event */
2311 #if USE_SEIZE
2312 if (event == PTRACE_EVENT_STOP) {
2313 /*
2314 * PTRACE_INTERRUPT-stop or group-stop.
2315 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
2316 */
2317 if (sig == SIGSTOP
2318 || sig == SIGTSTP
2319 || sig == SIGTTIN
2320 || sig == SIGTTOU
2321 ) {
2322 stopped = 1;
2323 goto show_stopsig;
2324 }
2325 }
2326 #endif
2327 goto restart_tracee_with_sig_0;
2328 }
2329
2330 /* Is this post-attach SIGSTOP?
2331 * Interestingly, the process may stop
2332 * with STOPSIG equal to some other signal
2333 * than SIGSTOP if we happend to attach
2334 * just before the process takes a signal.
2335 */
2336 if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
2337 if (debug_flag)
2338 fprintf(stderr, "ignored SIGSTOP on pid %d\n", tcp->pid);
2339 tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
2340 goto restart_tracee_with_sig_0;
2341 }
2342
2343 if (sig != syscall_trap_sig) {
2344 siginfo_t si;
2345
2346 /* Nonzero (true) if tracee is stopped by signal
2347 * (as opposed to "tracee received signal").
2348 * TODO: shouldn't we check for errno == EINVAL too?
2349 * We can get ESRCH instead, you know...
2350 */
2351 stopped = (ptrace(PTRACE_GETSIGINFO, pid, 0, (long) &si) < 0);
2352 #if USE_SEIZE
2353 show_stopsig:
2354 #endif
2355 if (cflag != CFLAG_ONLY_STATS
2356 && !hide_log_until_execve
2357 && (qual_flags[sig] & QUAL_SIGNAL)
2358 ) {
2359 printleader(tcp);
2360 if (!stopped) {
2361 tprintf("--- %s ", signame(sig));
2362 printsiginfo(&si, verbose(tcp));
2363 tprints(" ---\n");
2364 } else
2365 tprintf("--- stopped by %s ---\n",
2366 signame(sig));
2367 line_ended();
2368 }
2369
2370 if (!stopped)
2371 /* It's signal-delivery-stop. Inject the signal */
2372 goto restart_tracee;
2373
2374 /* It's group-stop */
2375 if (use_seize) {
2376 /*
2377 * This ends ptrace-stop, but does *not* end group-stop.
2378 * This makes stopping signals work properly on straced process
2379 * (that is, process really stops. It used to continue to run).
2380 */
2381 if (ptrace_restart(PTRACE_LISTEN, tcp, 0) < 0) {
2382 /* Note: ptrace_restart emitted error message */
2383 exit_code = 1;
2384 return;
2385 }
2386 continue;
2387 }
2388 /* We don't have PTRACE_LISTEN support... */
2389 goto restart_tracee;
2390 }
2391
2392 /* We handled quick cases, we are permitted to interrupt now. */
2393 if (interrupted)
2394 return;
2395
2396 /* This should be syscall entry or exit.
2397 * (Or it still can be that pesky post-execve SIGTRAP!)
2398 * Handle it.
2399 */
2400 if (trace_syscall(tcp) < 0) {
2401 /* ptrace() failed in trace_syscall().
2402 * Likely a result of process disappearing mid-flight.
2403 * Observed case: exit_group() or SIGKILL terminating
2404 * all processes in thread group.
2405 * We assume that ptrace error was caused by process death.
2406 * We used to detach(tcp) here, but since we no longer
2407 * implement "detach before death" policy/hack,
2408 * we can let this process to report its death to us
2409 * normally, via WIFEXITED or WIFSIGNALED wait status.
2410 */
2411 continue;
2412 }
2413 restart_tracee_with_sig_0:
2414 sig = 0;
2415 restart_tracee:
2416 if (ptrace_restart(PTRACE_SYSCALL, tcp, sig) < 0) {
2417 /* Note: ptrace_restart emitted error message */
2418 exit_code = 1;
2419 return;
2420 }
2421 } /* while (1) */
2422 }
2423
2424 int
main(int argc,char * argv[])2425 main(int argc, char *argv[])
2426 {
2427 init(argc, argv);
2428
2429 /* Run main tracing loop */
2430 trace();
2431
2432 cleanup();
2433 fflush(NULL);
2434 if (shared_log != stderr)
2435 fclose(shared_log);
2436 if (popen_pid) {
2437 while (waitpid(popen_pid, NULL, 0) < 0 && errno == EINTR)
2438 ;
2439 }
2440 if (exit_code > 0xff) {
2441 /* Avoid potential core file clobbering. */
2442 struct_rlimit rlim = {0, 0};
2443 set_rlimit(RLIMIT_CORE, &rlim);
2444
2445 /* Child was killed by a signal, mimic that. */
2446 exit_code &= 0xff;
2447 signal(exit_code, SIG_DFL);
2448 raise(exit_code);
2449 /* Paranoia - what if this signal is not fatal?
2450 Exit with 128 + signo then. */
2451 exit_code += 128;
2452 }
2453
2454 return exit_code;
2455 }
2456