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 <signal.h>
36 #include <sys/resource.h>
37 #include <sys/wait.h>
38 #include <sys/stat.h>
39 #include <pwd.h>
40 #include <grp.h>
41 #include <dirent.h>
42 #include <sys/utsname.h>
43 #ifdef HAVE_PRCTL
44 # include <sys/prctl.h>
45 #endif
46 #include <asm/unistd.h>
47
48 #include "scno.h"
49 #include "ptrace.h"
50 #include "printsiginfo.h"
51
52 /* In some libc, these aren't declared. Do it ourself: */
53 extern char **environ;
54 extern int optind;
55 extern char *optarg;
56
57 #ifdef USE_LIBUNWIND
58 /* if this is true do the stack trace for every system call */
59 bool stack_trace_enabled = false;
60 #endif
61
62 #define my_tkill(tid, sig) syscall(__NR_tkill, (tid), (sig))
63
64 /* Glue for systems without a MMU that cannot provide fork() */
65 #if !defined(HAVE_FORK)
66 # undef NOMMU_SYSTEM
67 # define NOMMU_SYSTEM 1
68 #endif
69 #if NOMMU_SYSTEM
70 # define fork() vfork()
71 #endif
72
73 const unsigned int syscall_trap_sig = SIGTRAP | 0x80;
74
75 cflag_t cflag = CFLAG_NONE;
76 unsigned int followfork = 0;
77 unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC
78 | PTRACE_O_TRACEEXIT;
79 unsigned int xflag = 0;
80 bool debug_flag = 0;
81 bool Tflag = 0;
82 bool iflag = 0;
83 bool count_wallclock = 0;
84 unsigned int qflag = 0;
85 static unsigned int tflag = 0;
86 static bool rflag = 0;
87 static bool print_pid_pfx = 0;
88
89 /* -I n */
90 enum {
91 INTR_NOT_SET = 0,
92 INTR_ANYWHERE = 1, /* don't block/ignore any signals */
93 INTR_WHILE_WAIT = 2, /* block fatal signals while decoding syscall. default */
94 INTR_NEVER = 3, /* block fatal signals. default if '-o FILE PROG' */
95 INTR_BLOCK_TSTP_TOO = 4, /* block fatal signals and SIGTSTP (^Z) */
96 NUM_INTR_OPTS
97 };
98 static int opt_intr;
99 /* We play with signal mask only if this mode is active: */
100 #define interactive (opt_intr == INTR_WHILE_WAIT)
101
102 /*
103 * daemonized_tracer supports -D option.
104 * With this option, strace forks twice.
105 * Unlike normal case, with -D *grandparent* process exec's,
106 * becoming a traced process. Child exits (this prevents traced process
107 * from having children it doesn't expect to have), and grandchild
108 * attaches to grandparent similarly to strace -p PID.
109 * This allows for more transparent interaction in cases
110 * when process and its parent are communicating via signals,
111 * wait() etc. Without -D, strace process gets lodged in between,
112 * disrupting parent<->child link.
113 */
114 static bool daemonized_tracer = 0;
115
116 #if USE_SEIZE
117 static int post_attach_sigstop = TCB_IGNORE_ONE_SIGSTOP;
118 # define use_seize (post_attach_sigstop == 0)
119 #else
120 # define post_attach_sigstop TCB_IGNORE_ONE_SIGSTOP
121 # define use_seize 0
122 #endif
123
124 /* Sometimes we want to print only succeeding syscalls. */
125 bool not_failing_only = 0;
126
127 /* Show path associated with fd arguments */
128 unsigned int show_fd_path = 0;
129
130 static bool detach_on_execve = 0;
131
132 static int exit_code;
133 static int strace_child = 0;
134 static int strace_tracer_pid = 0;
135
136 static char *username = NULL;
137 static uid_t run_uid;
138 static gid_t run_gid;
139
140 unsigned int max_strlen = DEFAULT_STRLEN;
141 static int acolumn = DEFAULT_ACOLUMN;
142 static char *acolumn_spaces;
143
144 static char *outfname = NULL;
145 /* If -ff, points to stderr. Else, it's our common output log */
146 static FILE *shared_log;
147
148 struct tcb *printing_tcp = NULL;
149 static struct tcb *current_tcp;
150
151 static struct tcb **tcbtab;
152 static unsigned int nprocs, tcbtabsize;
153 static const char *progname;
154
155 unsigned os_release; /* generated from uname()'s u.release */
156
157 static void detach(struct tcb *tcp);
158 static void cleanup(void);
159 static void interrupt(int sig);
160 static sigset_t empty_set, blocked_set;
161
162 #ifdef HAVE_SIG_ATOMIC_T
163 static volatile sig_atomic_t interrupted;
164 #else
165 static volatile int interrupted;
166 #endif
167
168 #ifndef HAVE_STRERROR
169
170 #if !HAVE_DECL_SYS_ERRLIST
171 extern int sys_nerr;
172 extern char *sys_errlist[];
173 #endif
174
175 const char *
strerror(int err_no)176 strerror(int err_no)
177 {
178 static char buf[sizeof("Unknown error %d") + sizeof(int)*3];
179
180 if (err_no < 1 || err_no >= sys_nerr) {
181 sprintf(buf, "Unknown error %d", err_no);
182 return buf;
183 }
184 return sys_errlist[err_no];
185 }
186
187 #endif /* HAVE_STERRROR */
188
189 static void
print_version(void)190 print_version(void)
191 {
192 printf("%s -- version %s\n"
193 "Copyright (C) %s The strace developers <%s>.\n"
194 "This is free software; see the source for copying conditions. There is NO\n"
195 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n",
196 PACKAGE_NAME, PACKAGE_VERSION, "1991-2017", PACKAGE_URL);
197 }
198
199 static void
usage(void)200 usage(void)
201 {
202 printf("\
203 usage: strace [-CdffhiqrtttTvVwxxy] [-I n] [-e expr]...\n\
204 [-a column] [-o file] [-s strsize] [-P path]...\n\
205 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
206 or: strace -c[dfw] [-I n] [-e expr]... [-O overhead] [-S sortby]\n\
207 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
208 \n\
209 Output format:\n\
210 -a column alignment COLUMN for printing syscall results (default %d)\n\
211 -i print instruction pointer at time of syscall\n\
212 "
213 #ifdef USE_LIBUNWIND
214 "\
215 -k obtain stack trace between each syscall (experimental)\n\
216 "
217 #endif
218 "\
219 -o file send trace output to FILE instead of stderr\n\
220 -q suppress messages about attaching, detaching, etc.\n\
221 -r print relative timestamp\n\
222 -s strsize limit length of print strings to STRSIZE chars (default %d)\n\
223 -t print absolute timestamp\n\
224 -tt print absolute timestamp with usecs\n\
225 -T print time spent in each syscall\n\
226 -x print non-ascii strings in hex\n\
227 -xx print all strings in hex\n\
228 -y print paths associated with file descriptor arguments\n\
229 -yy print protocol specific information associated with socket file descriptors\n\
230 \n\
231 Statistics:\n\
232 -c count time, calls, and errors for each syscall and report summary\n\
233 -C like -c but also print regular output\n\
234 -O overhead set overhead for tracing syscalls to OVERHEAD usecs\n\
235 -S sortby sort syscall counts by: time, calls, name, nothing (default %s)\n\
236 -w summarise syscall latency (default is system time)\n\
237 \n\
238 Filtering:\n\
239 -e expr a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
240 options: trace, abbrev, verbose, raw, signal, read, write, fault\n\
241 -P path trace accesses to path\n\
242 \n\
243 Tracing:\n\
244 -b execve detach on execve syscall\n\
245 -D run tracer process as a detached grandchild, not as parent\n\
246 -f follow forks\n\
247 -ff follow forks with output into separate files\n\
248 -I interruptible\n\
249 1: no signals are blocked\n\
250 2: fatal signals are blocked while decoding syscall (default)\n\
251 3: fatal signals are always blocked (default if '-o FILE PROG')\n\
252 4: fatal signals and SIGTSTP (^Z) are always blocked\n\
253 (useful to make 'strace -o FILE PROG' not stop on ^Z)\n\
254 \n\
255 Startup:\n\
256 -E var remove var from the environment for command\n\
257 -E var=val put var=val in the environment for command\n\
258 -p pid trace process with process id PID, may be repeated\n\
259 -u username run command as username handling setuid and/or setgid\n\
260 \n\
261 Miscellaneous:\n\
262 -d enable debug output to stderr\n\
263 -v verbose mode: print unabbreviated argv, stat, termios, etc. args\n\
264 -h print help message\n\
265 -V print version\n\
266 "
267 /* ancient, no one should use it
268 -F -- attempt to follow vforks (deprecated, use -f)\n\
269 */
270 /* this is broken, so don't document it
271 -z -- print only succeeding syscalls\n\
272 */
273 , DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
274 exit(0);
275 }
276
277 static void ATTRIBUTE_NORETURN
die(void)278 die(void)
279 {
280 if (strace_tracer_pid == getpid()) {
281 cflag = 0;
282 cleanup();
283 }
284 exit(1);
285 }
286
verror_msg(int err_no,const char * fmt,va_list p)287 static void verror_msg(int err_no, const char *fmt, va_list p)
288 {
289 char *msg;
290
291 fflush(NULL);
292
293 /* We want to print entire message with single fprintf to ensure
294 * message integrity if stderr is shared with other programs.
295 * Thus we use vasprintf + single fprintf.
296 */
297 msg = NULL;
298 if (vasprintf(&msg, fmt, p) >= 0) {
299 if (err_no)
300 fprintf(stderr, "%s: %s: %s\n", progname, msg, strerror(err_no));
301 else
302 fprintf(stderr, "%s: %s\n", progname, msg);
303 free(msg);
304 } else {
305 /* malloc in vasprintf failed, try it without malloc */
306 fprintf(stderr, "%s: ", progname);
307 vfprintf(stderr, fmt, p);
308 if (err_no)
309 fprintf(stderr, ": %s\n", strerror(err_no));
310 else
311 putc('\n', stderr);
312 }
313 /* We don't switch stderr to buffered, thus fprintf(stderr)
314 * always flushes its output and this is not necessary: */
315 /* fflush(stderr); */
316 }
317
error_msg(const char * fmt,...)318 void error_msg(const char *fmt, ...)
319 {
320 va_list p;
321 va_start(p, fmt);
322 verror_msg(0, fmt, p);
323 va_end(p);
324 }
325
error_msg_and_die(const char * fmt,...)326 void error_msg_and_die(const char *fmt, ...)
327 {
328 va_list p;
329 va_start(p, fmt);
330 verror_msg(0, fmt, p);
331 die();
332 }
333
error_msg_and_help(const char * fmt,...)334 void error_msg_and_help(const char *fmt, ...)
335 {
336 if (fmt != NULL) {
337 va_list p;
338 va_start(p, fmt);
339 verror_msg(0, fmt, p);
340 }
341 fprintf(stderr, "Try '%s -h' for more information.\n", progname);
342 die();
343 }
344
perror_msg(const char * fmt,...)345 void perror_msg(const char *fmt, ...)
346 {
347 va_list p;
348 va_start(p, fmt);
349 verror_msg(errno, fmt, p);
350 va_end(p);
351 }
352
perror_msg_and_die(const char * fmt,...)353 void perror_msg_and_die(const char *fmt, ...)
354 {
355 va_list p;
356 va_start(p, fmt);
357 verror_msg(errno, fmt, p);
358 die();
359 }
360
361 static void
error_opt_arg(int opt,const char * arg)362 error_opt_arg(int opt, const char *arg)
363 {
364 error_msg_and_help("invalid -%c argument: '%s'", opt, arg);
365 }
366
367 static const char *ptrace_attach_cmd;
368
369 static int
ptrace_attach_or_seize(int pid)370 ptrace_attach_or_seize(int pid)
371 {
372 #if USE_SEIZE
373 int r;
374 if (!use_seize)
375 return ptrace_attach_cmd = "PTRACE_ATTACH",
376 ptrace(PTRACE_ATTACH, pid, 0L, 0L);
377 r = ptrace(PTRACE_SEIZE, pid, 0L, (unsigned long) ptrace_setoptions);
378 if (r)
379 return ptrace_attach_cmd = "PTRACE_SEIZE", r;
380 r = ptrace(PTRACE_INTERRUPT, pid, 0L, 0L);
381 return ptrace_attach_cmd = "PTRACE_INTERRUPT", r;
382 #else
383 return ptrace_attach_cmd = "PTRACE_ATTACH",
384 ptrace(PTRACE_ATTACH, pid, 0L, 0L);
385 #endif
386 }
387
388 /*
389 * Used when we want to unblock stopped traced process.
390 * Should be only used with PTRACE_CONT, PTRACE_DETACH and PTRACE_SYSCALL.
391 * Returns 0 on success or if error was ESRCH
392 * (presumably process was killed while we talk to it).
393 * Otherwise prints error message and returns -1.
394 */
395 static int
ptrace_restart(const unsigned int op,struct tcb * const tcp,unsigned int sig)396 ptrace_restart(const unsigned int op, struct tcb *const tcp, unsigned int sig)
397 {
398 int err;
399 const char *msg;
400
401 errno = 0;
402 ptrace(op, tcp->pid, 0L, (unsigned long) sig);
403 err = errno;
404 if (!err)
405 return 0;
406
407 switch (op) {
408 case PTRACE_CONT:
409 msg = "CONT";
410 break;
411 case PTRACE_DETACH:
412 msg = "DETACH";
413 break;
414 case PTRACE_LISTEN:
415 msg = "LISTEN";
416 break;
417 default:
418 msg = "SYSCALL";
419 }
420
421 /*
422 * Why curcol != 0? Otherwise sometimes we get this:
423 *
424 * 10252 kill(10253, SIGKILL) = 0
425 * <ptrace(SYSCALL,10252):No such process>10253 ...next decode...
426 *
427 * 10252 died after we retrieved syscall exit data,
428 * but before we tried to restart it. Log looks ugly.
429 */
430 if (current_tcp && current_tcp->curcol != 0) {
431 tprintf(" <ptrace(%s):%s>\n", msg, strerror(err));
432 line_ended();
433 }
434 if (err == ESRCH)
435 return 0;
436 errno = err;
437 perror_msg("ptrace(PTRACE_%s,pid:%d,sig:%u)", msg, tcp->pid, sig);
438 return -1;
439 }
440
441 static void
set_cloexec_flag(int fd)442 set_cloexec_flag(int fd)
443 {
444 int flags, newflags;
445
446 flags = fcntl(fd, F_GETFD);
447 if (flags < 0) {
448 /* Can happen only if fd is bad.
449 * Should never happen: if it does, we have a bug
450 * in the caller. Therefore we just abort
451 * instead of propagating the error.
452 */
453 perror_msg_and_die("fcntl(%d, F_GETFD)", fd);
454 }
455
456 newflags = flags | FD_CLOEXEC;
457 if (flags == newflags)
458 return;
459
460 fcntl(fd, F_SETFD, newflags); /* never fails */
461 }
462
463 static void
kill_save_errno(pid_t pid,int sig)464 kill_save_errno(pid_t pid, int sig)
465 {
466 int saved_errno = errno;
467
468 (void) kill(pid, sig);
469 errno = saved_errno;
470 }
471
472 /*
473 * When strace is setuid executable, we have to swap uids
474 * before and after filesystem and process management operations.
475 */
476 static void
swap_uid(void)477 swap_uid(void)
478 {
479 int euid = geteuid(), uid = getuid();
480
481 if (euid != uid && setreuid(euid, uid) < 0) {
482 perror_msg_and_die("setreuid");
483 }
484 }
485
486 #ifdef _LARGEFILE64_SOURCE
487 # ifdef HAVE_FOPEN64
488 # define fopen_for_output fopen64
489 # else
490 # define fopen_for_output fopen
491 # endif
492 # define struct_stat struct stat64
493 # define stat_file stat64
494 # define struct_dirent struct dirent64
495 # define read_dir readdir64
496 # define struct_rlimit struct rlimit64
497 # define set_rlimit setrlimit64
498 #else
499 # define fopen_for_output fopen
500 # define struct_stat struct stat
501 # define stat_file stat
502 # define struct_dirent struct dirent
503 # define read_dir readdir
504 # define struct_rlimit struct rlimit
505 # define set_rlimit setrlimit
506 #endif
507
508 static FILE *
strace_fopen(const char * path)509 strace_fopen(const char *path)
510 {
511 FILE *fp;
512
513 swap_uid();
514 fp = fopen_for_output(path, "w");
515 if (!fp)
516 perror_msg_and_die("Can't fopen '%s'", path);
517 swap_uid();
518 set_cloexec_flag(fileno(fp));
519 return fp;
520 }
521
522 static int popen_pid = 0;
523
524 #ifndef _PATH_BSHELL
525 # define _PATH_BSHELL "/bin/sh"
526 #endif
527
528 /*
529 * We cannot use standard popen(3) here because we have to distinguish
530 * popen child process from other processes we trace, and standard popen(3)
531 * does not export its child's pid.
532 */
533 static FILE *
strace_popen(const char * command)534 strace_popen(const char *command)
535 {
536 FILE *fp;
537 int pid;
538 int fds[2];
539
540 swap_uid();
541 if (pipe(fds) < 0)
542 perror_msg_and_die("pipe");
543
544 set_cloexec_flag(fds[1]); /* never fails */
545
546 pid = vfork();
547 if (pid < 0)
548 perror_msg_and_die("vfork");
549
550 if (pid == 0) {
551 /* child */
552 close(fds[1]);
553 if (fds[0] != 0) {
554 if (dup2(fds[0], 0))
555 perror_msg_and_die("dup2");
556 close(fds[0]);
557 }
558 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
559 perror_msg_and_die("Can't execute '%s'", _PATH_BSHELL);
560 }
561
562 /* parent */
563 popen_pid = pid;
564 close(fds[0]);
565 swap_uid();
566 fp = fdopen(fds[1], "w");
567 if (!fp)
568 die_out_of_memory();
569 return fp;
570 }
571
572 void
tprintf(const char * fmt,...)573 tprintf(const char *fmt, ...)
574 {
575 va_list args;
576
577 va_start(args, fmt);
578 if (current_tcp) {
579 int n = vfprintf(current_tcp->outf, fmt, args);
580 if (n < 0) {
581 if (current_tcp->outf != stderr)
582 perror_msg("%s", outfname);
583 } else
584 current_tcp->curcol += n;
585 }
586 va_end(args);
587 }
588
589 #ifndef HAVE_FPUTS_UNLOCKED
590 # define fputs_unlocked fputs
591 #endif
592
593 void
tprints(const char * str)594 tprints(const char *str)
595 {
596 if (current_tcp) {
597 int n = fputs_unlocked(str, current_tcp->outf);
598 if (n >= 0) {
599 current_tcp->curcol += strlen(str);
600 return;
601 }
602 if (current_tcp->outf != stderr)
603 perror_msg("%s", outfname);
604 }
605 }
606
607 void
line_ended(void)608 line_ended(void)
609 {
610 if (current_tcp) {
611 current_tcp->curcol = 0;
612 fflush(current_tcp->outf);
613 }
614 if (printing_tcp) {
615 printing_tcp->curcol = 0;
616 printing_tcp = NULL;
617 }
618 }
619
620 void
printleader(struct tcb * tcp)621 printleader(struct tcb *tcp)
622 {
623 /* If -ff, "previous tcb we printed" is always the same as current,
624 * because we have per-tcb output files.
625 */
626 if (followfork >= 2)
627 printing_tcp = tcp;
628
629 if (printing_tcp) {
630 current_tcp = printing_tcp;
631 if (printing_tcp->curcol != 0 && (followfork < 2 || printing_tcp == tcp)) {
632 /*
633 * case 1: we have a shared log (i.e. not -ff), and last line
634 * wasn't finished (same or different tcb, doesn't matter).
635 * case 2: split log, we are the same tcb, but our last line
636 * didn't finish ("SIGKILL nuked us after syscall entry" etc).
637 */
638 tprints(" <unfinished ...>\n");
639 printing_tcp->curcol = 0;
640 }
641 }
642
643 printing_tcp = tcp;
644 current_tcp = tcp;
645 current_tcp->curcol = 0;
646
647 if (print_pid_pfx)
648 tprintf("%-5d ", tcp->pid);
649 else if (nprocs > 1 && !outfname)
650 tprintf("[pid %5u] ", tcp->pid);
651
652 if (tflag) {
653 char str[sizeof("HH:MM:SS")];
654 struct timeval tv, dtv;
655 static struct timeval otv;
656
657 gettimeofday(&tv, NULL);
658 if (rflag) {
659 if (otv.tv_sec == 0)
660 otv = tv;
661 tv_sub(&dtv, &tv, &otv);
662 tprintf("%6ld.%06ld ",
663 (long) dtv.tv_sec, (long) dtv.tv_usec);
664 otv = tv;
665 }
666 else if (tflag > 2) {
667 tprintf("%ld.%06ld ",
668 (long) tv.tv_sec, (long) tv.tv_usec);
669 }
670 else {
671 time_t local = tv.tv_sec;
672 strftime(str, sizeof(str), "%T", localtime(&local));
673 if (tflag > 1)
674 tprintf("%s.%06ld ", str, (long) tv.tv_usec);
675 else
676 tprintf("%s ", str);
677 }
678 }
679 if (iflag)
680 print_pc(tcp);
681 }
682
683 void
tabto(void)684 tabto(void)
685 {
686 if (current_tcp->curcol < acolumn)
687 tprints(acolumn_spaces + current_tcp->curcol);
688 }
689
690 /* Should be only called directly *after successful attach* to a tracee.
691 * Otherwise, "strace -oFILE -ff -p<nonexistant_pid>"
692 * may create bogus empty FILE.<nonexistant_pid>, and then die.
693 */
694 static void
newoutf(struct tcb * tcp)695 newoutf(struct tcb *tcp)
696 {
697 tcp->outf = shared_log; /* if not -ff mode, the same file is for all */
698 if (followfork >= 2) {
699 char name[520 + sizeof(int) * 3];
700 sprintf(name, "%.512s.%u", outfname, tcp->pid);
701 tcp->outf = strace_fopen(name);
702 }
703 }
704
705 static void
expand_tcbtab(void)706 expand_tcbtab(void)
707 {
708 /* Allocate some (more) TCBs (and expand the table).
709 We don't want to relocate the TCBs because our
710 callers have pointers and it would be a pain.
711 So tcbtab is a table of pointers. Since we never
712 free the TCBs, we allocate a single chunk of many. */
713 unsigned int new_tcbtabsize, alloc_tcbtabsize;
714 struct tcb *newtcbs;
715
716 if (tcbtabsize) {
717 alloc_tcbtabsize = tcbtabsize;
718 new_tcbtabsize = tcbtabsize * 2;
719 } else {
720 new_tcbtabsize = alloc_tcbtabsize = 1;
721 }
722
723 newtcbs = xcalloc(alloc_tcbtabsize, sizeof(newtcbs[0]));
724 tcbtab = xreallocarray(tcbtab, new_tcbtabsize, sizeof(tcbtab[0]));
725 while (tcbtabsize < new_tcbtabsize)
726 tcbtab[tcbtabsize++] = newtcbs++;
727 }
728
729 static struct tcb *
alloctcb(int pid)730 alloctcb(int pid)
731 {
732 unsigned int i;
733 struct tcb *tcp;
734
735 if (nprocs == tcbtabsize)
736 expand_tcbtab();
737
738 for (i = 0; i < tcbtabsize; i++) {
739 tcp = tcbtab[i];
740 if (!tcp->pid) {
741 memset(tcp, 0, sizeof(*tcp));
742 tcp->pid = pid;
743 #if SUPPORTED_PERSONALITIES > 1
744 tcp->currpers = current_personality;
745 #endif
746
747 #ifdef USE_LIBUNWIND
748 if (stack_trace_enabled)
749 unwind_tcb_init(tcp);
750 #endif
751
752 nprocs++;
753 if (debug_flag)
754 error_msg("new tcb for pid %d, active tcbs:%d",
755 tcp->pid, nprocs);
756 return tcp;
757 }
758 }
759 error_msg_and_die("bug in alloctcb");
760 }
761
762 void *
get_tcb_priv_data(const struct tcb * tcp)763 get_tcb_priv_data(const struct tcb *tcp)
764 {
765 return tcp->_priv_data;
766 }
767
768 int
set_tcb_priv_data(struct tcb * tcp,void * const priv_data,void (* const free_priv_data)(void *))769 set_tcb_priv_data(struct tcb *tcp, void *const priv_data,
770 void (*const free_priv_data)(void *))
771 {
772 if (tcp->_priv_data)
773 return -1;
774
775 tcp->_free_priv_data = free_priv_data;
776 tcp->_priv_data = priv_data;
777
778 return 0;
779 }
780
781 void
free_tcb_priv_data(struct tcb * tcp)782 free_tcb_priv_data(struct tcb *tcp)
783 {
784 if (tcp->_priv_data) {
785 if (tcp->_free_priv_data) {
786 tcp->_free_priv_data(tcp->_priv_data);
787 tcp->_free_priv_data = NULL;
788 }
789 tcp->_priv_data = NULL;
790 }
791 }
792
793 static void
droptcb(struct tcb * tcp)794 droptcb(struct tcb *tcp)
795 {
796 if (tcp->pid == 0)
797 return;
798
799 int p;
800 for (p = 0; p < SUPPORTED_PERSONALITIES; ++p)
801 free(tcp->inject_vec[p]);
802
803 free_tcb_priv_data(tcp);
804
805 #ifdef USE_LIBUNWIND
806 if (stack_trace_enabled) {
807 unwind_tcb_fin(tcp);
808 }
809 #endif
810
811 nprocs--;
812 if (debug_flag)
813 error_msg("dropped tcb for pid %d, %d remain",
814 tcp->pid, nprocs);
815
816 if (tcp->outf) {
817 if (followfork >= 2) {
818 if (tcp->curcol != 0)
819 fprintf(tcp->outf, " <detached ...>\n");
820 fclose(tcp->outf);
821 } else {
822 if (printing_tcp == tcp && tcp->curcol != 0)
823 fprintf(tcp->outf, " <detached ...>\n");
824 fflush(tcp->outf);
825 }
826 }
827
828 if (current_tcp == tcp)
829 current_tcp = NULL;
830 if (printing_tcp == tcp)
831 printing_tcp = NULL;
832
833 memset(tcp, 0, sizeof(*tcp));
834 }
835
836 /* Detach traced process.
837 * Never call DETACH twice on the same process as both unattached and
838 * attached-unstopped processes give the same ESRCH. For unattached process we
839 * would SIGSTOP it and wait for its SIGSTOP notification forever.
840 */
841 static void
detach(struct tcb * tcp)842 detach(struct tcb *tcp)
843 {
844 int error;
845 int status;
846
847 /*
848 * Linux wrongly insists the child be stopped
849 * before detaching. Arghh. We go through hoops
850 * to make a clean break of things.
851 */
852
853 if (!(tcp->flags & TCB_ATTACHED))
854 goto drop;
855
856 /* We attached but possibly didn't see the expected SIGSTOP.
857 * We must catch exactly one as otherwise the detached process
858 * would be left stopped (process state T).
859 */
860 if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
861 goto wait_loop;
862
863 error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
864 if (!error) {
865 /* On a clear day, you can see forever. */
866 goto drop;
867 }
868 if (errno != ESRCH) {
869 /* Shouldn't happen. */
870 perror_msg("detach: ptrace(PTRACE_DETACH,%u)", tcp->pid);
871 goto drop;
872 }
873 /* ESRCH: process is either not stopped or doesn't exist. */
874 if (my_tkill(tcp->pid, 0) < 0) {
875 if (errno != ESRCH)
876 /* Shouldn't happen. */
877 perror_msg("detach: tkill(%u,0)", tcp->pid);
878 /* else: process doesn't exist. */
879 goto drop;
880 }
881 /* Process is not stopped, need to stop it. */
882 if (use_seize) {
883 /*
884 * With SEIZE, tracee can be in group-stop already.
885 * In this state sending it another SIGSTOP does nothing.
886 * Need to use INTERRUPT.
887 * Testcase: trying to ^C a "strace -p <stopped_process>".
888 */
889 error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
890 if (!error)
891 goto wait_loop;
892 if (errno != ESRCH)
893 perror_msg("detach: ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
894 }
895 else {
896 error = my_tkill(tcp->pid, SIGSTOP);
897 if (!error)
898 goto wait_loop;
899 if (errno != ESRCH)
900 perror_msg("detach: tkill(%u,SIGSTOP)", tcp->pid);
901 }
902 /* Either process doesn't exist, or some weird error. */
903 goto drop;
904
905 wait_loop:
906 /* We end up here in three cases:
907 * 1. We sent PTRACE_INTERRUPT (use_seize case)
908 * 2. We sent SIGSTOP (!use_seize)
909 * 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
910 */
911 for (;;) {
912 unsigned int sig;
913 if (waitpid(tcp->pid, &status, __WALL) < 0) {
914 if (errno == EINTR)
915 continue;
916 /*
917 * if (errno == ECHILD) break;
918 * ^^^ WRONG! We expect this PID to exist,
919 * and want to emit a message otherwise:
920 */
921 perror_msg("detach: waitpid(%u)", tcp->pid);
922 break;
923 }
924 if (!WIFSTOPPED(status)) {
925 /*
926 * Tracee exited or was killed by signal.
927 * We shouldn't normally reach this place:
928 * we don't want to consume exit status.
929 * Consider "strace -p PID" being ^C-ed:
930 * we want merely to detach from PID.
931 *
932 * However, we _can_ end up here if tracee
933 * was SIGKILLed.
934 */
935 break;
936 }
937 sig = WSTOPSIG(status);
938 if (debug_flag)
939 error_msg("detach wait: event:%d sig:%d",
940 (unsigned)status >> 16, sig);
941 if (use_seize) {
942 unsigned event = (unsigned)status >> 16;
943 if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
944 /*
945 * sig == SIGTRAP: PTRACE_INTERRUPT stop.
946 * sig == other: process was already stopped
947 * with this stopping sig (see tests/detach-stopped).
948 * Looks like re-injecting this sig is not necessary
949 * in DETACH for the tracee to remain stopped.
950 */
951 sig = 0;
952 }
953 /*
954 * PTRACE_INTERRUPT is not guaranteed to produce
955 * the above event if other ptrace-stop is pending.
956 * See tests/detach-sleeping testcase:
957 * strace got SIGINT while tracee is sleeping.
958 * We sent PTRACE_INTERRUPT.
959 * We see syscall exit, not PTRACE_INTERRUPT stop.
960 * We won't get PTRACE_INTERRUPT stop
961 * if we would CONT now. Need to DETACH.
962 */
963 if (sig == syscall_trap_sig)
964 sig = 0;
965 /* else: not sure in which case we can be here.
966 * Signal stop? Inject it while detaching.
967 */
968 ptrace_restart(PTRACE_DETACH, tcp, sig);
969 break;
970 }
971 /* Note: this check has to be after use_seize check */
972 /* (else, in use_seize case SIGSTOP will be mistreated) */
973 if (sig == SIGSTOP) {
974 /* Detach, suppressing SIGSTOP */
975 ptrace_restart(PTRACE_DETACH, tcp, 0);
976 break;
977 }
978 if (sig == syscall_trap_sig)
979 sig = 0;
980 /* Can't detach just yet, may need to wait for SIGSTOP */
981 error = ptrace_restart(PTRACE_CONT, tcp, sig);
982 if (error < 0) {
983 /* Should not happen.
984 * Note: ptrace_restart returns 0 on ESRCH, so it's not it.
985 * ptrace_restart already emitted error message.
986 */
987 break;
988 }
989 }
990
991 drop:
992 if (!qflag && (tcp->flags & TCB_ATTACHED))
993 error_msg("Process %u detached", tcp->pid);
994
995 droptcb(tcp);
996 }
997
998 static void
process_opt_p_list(char * opt)999 process_opt_p_list(char *opt)
1000 {
1001 while (*opt) {
1002 /*
1003 * We accept -p PID,PID; -p "`pidof PROG`"; -p "`pgrep PROG`".
1004 * pidof uses space as delim, pgrep uses newline. :(
1005 */
1006 int pid;
1007 char *delim = opt + strcspn(opt, ", \n\t");
1008 char c = *delim;
1009
1010 *delim = '\0';
1011 pid = string_to_uint(opt);
1012 if (pid <= 0) {
1013 error_msg_and_die("Invalid process id: '%s'", opt);
1014 }
1015 if (pid == strace_tracer_pid) {
1016 error_msg_and_die("I'm sorry, I can't let you do that, Dave.");
1017 }
1018 *delim = c;
1019 alloctcb(pid);
1020 if (c == '\0')
1021 break;
1022 opt = delim + 1;
1023 }
1024 }
1025
1026 static void
attach_tcb(struct tcb * const tcp)1027 attach_tcb(struct tcb *const tcp)
1028 {
1029 if (ptrace_attach_or_seize(tcp->pid) < 0) {
1030 perror_msg("attach: ptrace(%s, %d)",
1031 ptrace_attach_cmd, tcp->pid);
1032 droptcb(tcp);
1033 return;
1034 }
1035
1036 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1037 newoutf(tcp);
1038 if (debug_flag)
1039 error_msg("attach to pid %d (main) succeeded", tcp->pid);
1040
1041 char procdir[sizeof("/proc/%d/task") + sizeof(int) * 3];
1042 DIR *dir;
1043 unsigned int ntid = 0, nerr = 0;
1044
1045 if (followfork && tcp->pid != strace_child &&
1046 sprintf(procdir, "/proc/%d/task", tcp->pid) > 0 &&
1047 (dir = opendir(procdir)) != NULL) {
1048 struct_dirent *de;
1049
1050 while ((de = read_dir(dir)) != NULL) {
1051 if (de->d_fileno == 0)
1052 continue;
1053
1054 int tid = string_to_uint(de->d_name);
1055 if (tid <= 0 || tid == tcp->pid)
1056 continue;
1057
1058 ++ntid;
1059 if (ptrace_attach_or_seize(tid) < 0) {
1060 ++nerr;
1061 if (debug_flag)
1062 perror_msg("attach: ptrace(%s, %d)",
1063 ptrace_attach_cmd, tid);
1064 continue;
1065 }
1066 if (debug_flag)
1067 error_msg("attach to pid %d succeeded", tid);
1068
1069 struct tcb *tid_tcp = alloctcb(tid);
1070 tid_tcp->flags |= TCB_ATTACHED | TCB_STARTUP |
1071 post_attach_sigstop;
1072 newoutf(tid_tcp);
1073 }
1074
1075 closedir(dir);
1076 }
1077
1078 if (!qflag) {
1079 if (ntid > nerr)
1080 error_msg("Process %u attached"
1081 " with %u threads",
1082 tcp->pid, ntid - nerr + 1);
1083 else
1084 error_msg("Process %u attached",
1085 tcp->pid);
1086 }
1087 }
1088
1089 static void
startup_attach(void)1090 startup_attach(void)
1091 {
1092 pid_t parent_pid = strace_tracer_pid;
1093 unsigned int tcbi;
1094 struct tcb *tcp;
1095
1096 /*
1097 * Block user interruptions as we would leave the traced
1098 * process stopped (process state T) if we would terminate in
1099 * between PTRACE_ATTACH and wait4() on SIGSTOP.
1100 * We rely on cleanup() from this point on.
1101 */
1102 if (interactive)
1103 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
1104
1105 if (daemonized_tracer) {
1106 pid_t pid = fork();
1107 if (pid < 0) {
1108 perror_msg_and_die("fork");
1109 }
1110 if (pid) { /* parent */
1111 /*
1112 * Wait for grandchild to attach to straced process
1113 * (grandparent). Grandchild SIGKILLs us after it attached.
1114 * Grandparent's wait() is unblocked by our death,
1115 * it proceeds to exec the straced program.
1116 */
1117 pause();
1118 _exit(0); /* paranoia */
1119 }
1120 /* grandchild */
1121 /* We will be the tracer process. Remember our new pid: */
1122 strace_tracer_pid = getpid();
1123 }
1124
1125 for (tcbi = 0; tcbi < tcbtabsize; tcbi++) {
1126 tcp = tcbtab[tcbi];
1127
1128 if (!tcp->pid)
1129 continue;
1130
1131 /* Is this a process we should attach to, but not yet attached? */
1132 if (tcp->flags & TCB_ATTACHED)
1133 continue; /* no, we already attached it */
1134
1135 if (tcp->pid == parent_pid || tcp->pid == strace_tracer_pid) {
1136 errno = EPERM;
1137 perror_msg("attach: pid %d", tcp->pid);
1138 droptcb(tcp);
1139 continue;
1140 }
1141
1142 attach_tcb(tcp);
1143
1144 if (interactive) {
1145 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1146 if (interrupted)
1147 goto ret;
1148 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
1149 }
1150 } /* for each tcbtab[] */
1151
1152 if (daemonized_tracer) {
1153 /*
1154 * Make parent go away.
1155 * Also makes grandparent's wait() unblock.
1156 */
1157 kill(parent_pid, SIGKILL);
1158 strace_child = 0;
1159 }
1160
1161 ret:
1162 if (interactive)
1163 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1164 }
1165
1166 /* Stack-o-phobic exec helper, in the hope to work around
1167 * NOMMU + "daemonized tracer" difficulty.
1168 */
1169 struct exec_params {
1170 int fd_to_close;
1171 uid_t run_euid;
1172 gid_t run_egid;
1173 char **argv;
1174 char *pathname;
1175 };
1176 static struct exec_params params_for_tracee;
1177
1178 static void ATTRIBUTE_NOINLINE ATTRIBUTE_NORETURN
exec_or_die(void)1179 exec_or_die(void)
1180 {
1181 struct exec_params *params = ¶ms_for_tracee;
1182
1183 if (params->fd_to_close >= 0)
1184 close(params->fd_to_close);
1185 if (!daemonized_tracer && !use_seize) {
1186 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0) {
1187 perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
1188 }
1189 }
1190
1191 if (username != NULL) {
1192 /*
1193 * It is important to set groups before we
1194 * lose privileges on setuid.
1195 */
1196 if (initgroups(username, run_gid) < 0) {
1197 perror_msg_and_die("initgroups");
1198 }
1199 if (setregid(run_gid, params->run_egid) < 0) {
1200 perror_msg_and_die("setregid");
1201 }
1202 if (setreuid(run_uid, params->run_euid) < 0) {
1203 perror_msg_and_die("setreuid");
1204 }
1205 }
1206 else if (geteuid() != 0)
1207 if (setreuid(run_uid, run_uid) < 0) {
1208 perror_msg_and_die("setreuid");
1209 }
1210
1211 if (!daemonized_tracer) {
1212 /*
1213 * Induce a ptrace stop. Tracer (our parent)
1214 * will resume us with PTRACE_SYSCALL and display
1215 * the immediately following execve syscall.
1216 * Can't do this on NOMMU systems, we are after
1217 * vfork: parent is blocked, stopping would deadlock.
1218 */
1219 if (!NOMMU_SYSTEM)
1220 kill(getpid(), SIGSTOP);
1221 } else {
1222 alarm(3);
1223 /* we depend on SIGCHLD set to SIG_DFL by init code */
1224 /* if it happens to be SIG_IGN'ed, wait won't block */
1225 wait(NULL);
1226 alarm(0);
1227 }
1228
1229 execv(params->pathname, params->argv);
1230 perror_msg_and_die("exec");
1231 }
1232
1233 /*
1234 * Open a dummy descriptor for use as a placeholder.
1235 * The descriptor is O_RDONLY with FD_CLOEXEC flag set.
1236 * A read attempt from such descriptor ends with EOF,
1237 * a write attempt is rejected with EBADF.
1238 */
1239 static int
open_dummy_desc(void)1240 open_dummy_desc(void)
1241 {
1242 int fds[2];
1243
1244 if (pipe(fds))
1245 perror_msg_and_die("pipe");
1246 close(fds[1]);
1247 set_cloexec_flag(fds[0]);
1248 return fds[0];
1249 }
1250
1251 /* placeholder fds status for stdin and stdout */
1252 static bool fd_is_placeholder[2];
1253
1254 /*
1255 * Ensure that all standard file descriptors are open by opening placeholder
1256 * file descriptors for those standard file descriptors that are not open.
1257 *
1258 * The information which descriptors have been made open is saved
1259 * in fd_is_placeholder for later use.
1260 */
1261 static void
ensure_standard_fds_opened(void)1262 ensure_standard_fds_opened(void)
1263 {
1264 int fd;
1265
1266 while ((fd = open_dummy_desc()) <= 2) {
1267 if (fd == 2)
1268 break;
1269 fd_is_placeholder[fd] = true;
1270 }
1271
1272 if (fd > 2)
1273 close(fd);
1274 }
1275
1276 /*
1277 * Redirect stdin and stdout unless they have been opened earlier
1278 * by ensure_standard_fds_opened as placeholders.
1279 */
1280 static void
redirect_standard_fds(void)1281 redirect_standard_fds(void)
1282 {
1283 int i;
1284
1285 /*
1286 * It might be a good idea to redirect stderr as well,
1287 * but we sometimes need to print error messages.
1288 */
1289 for (i = 0; i <= 1; ++i) {
1290 if (!fd_is_placeholder[i]) {
1291 close(i);
1292 open_dummy_desc();
1293 }
1294 }
1295 }
1296
1297 static void
startup_child(char ** argv)1298 startup_child(char **argv)
1299 {
1300 struct_stat statbuf;
1301 const char *filename;
1302 size_t filename_len;
1303 char pathname[PATH_MAX];
1304 int pid;
1305 struct tcb *tcp;
1306
1307 filename = argv[0];
1308 filename_len = strlen(filename);
1309
1310 if (filename_len > sizeof(pathname) - 1) {
1311 errno = ENAMETOOLONG;
1312 perror_msg_and_die("exec");
1313 }
1314 if (strchr(filename, '/')) {
1315 strcpy(pathname, filename);
1316 }
1317 #ifdef USE_DEBUGGING_EXEC
1318 /*
1319 * Debuggers customarily check the current directory
1320 * first regardless of the path but doing that gives
1321 * security geeks a panic attack.
1322 */
1323 else if (stat_file(filename, &statbuf) == 0)
1324 strcpy(pathname, filename);
1325 #endif /* USE_DEBUGGING_EXEC */
1326 else {
1327 const char *path;
1328 size_t m, n, len;
1329
1330 for (path = getenv("PATH"); path && *path; path += m) {
1331 const char *colon = strchr(path, ':');
1332 if (colon) {
1333 n = colon - path;
1334 m = n + 1;
1335 }
1336 else
1337 m = n = strlen(path);
1338 if (n == 0) {
1339 if (!getcwd(pathname, PATH_MAX))
1340 continue;
1341 len = strlen(pathname);
1342 }
1343 else if (n > sizeof pathname - 1)
1344 continue;
1345 else {
1346 strncpy(pathname, path, n);
1347 len = n;
1348 }
1349 if (len && pathname[len - 1] != '/')
1350 pathname[len++] = '/';
1351 if (filename_len + len > sizeof(pathname) - 1)
1352 continue;
1353 strcpy(pathname + len, filename);
1354 if (stat_file(pathname, &statbuf) == 0 &&
1355 /* Accept only regular files
1356 with some execute bits set.
1357 XXX not perfect, might still fail */
1358 S_ISREG(statbuf.st_mode) &&
1359 (statbuf.st_mode & 0111))
1360 break;
1361 }
1362 if (!path || !*path)
1363 pathname[0] = '\0';
1364 }
1365 if (stat_file(pathname, &statbuf) < 0) {
1366 perror_msg_and_die("Can't stat '%s'", filename);
1367 }
1368
1369 params_for_tracee.fd_to_close = (shared_log != stderr) ? fileno(shared_log) : -1;
1370 params_for_tracee.run_euid = (statbuf.st_mode & S_ISUID) ? statbuf.st_uid : run_uid;
1371 params_for_tracee.run_egid = (statbuf.st_mode & S_ISGID) ? statbuf.st_gid : run_gid;
1372 params_for_tracee.argv = argv;
1373 /*
1374 * On NOMMU, can be safely freed only after execve in tracee.
1375 * It's hard to know when that happens, so we just leak it.
1376 */
1377 params_for_tracee.pathname = NOMMU_SYSTEM ? xstrdup(pathname) : pathname;
1378
1379 #if defined HAVE_PRCTL && defined PR_SET_PTRACER && defined PR_SET_PTRACER_ANY
1380 if (daemonized_tracer)
1381 prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
1382 #endif
1383
1384 pid = fork();
1385 if (pid < 0) {
1386 perror_msg_and_die("fork");
1387 }
1388 if ((pid != 0 && daemonized_tracer)
1389 || (pid == 0 && !daemonized_tracer)
1390 ) {
1391 /* We are to become the tracee. Two cases:
1392 * -D: we are parent
1393 * not -D: we are child
1394 */
1395 exec_or_die();
1396 }
1397
1398 /* We are the tracer */
1399
1400 if (!daemonized_tracer) {
1401 strace_child = pid;
1402 if (!use_seize) {
1403 /* child did PTRACE_TRACEME, nothing to do in parent */
1404 } else {
1405 if (!NOMMU_SYSTEM) {
1406 /* Wait until child stopped itself */
1407 int status;
1408 while (waitpid(pid, &status, WSTOPPED) < 0) {
1409 if (errno == EINTR)
1410 continue;
1411 perror_msg_and_die("waitpid");
1412 }
1413 if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGSTOP) {
1414 kill_save_errno(pid, SIGKILL);
1415 perror_msg_and_die("Unexpected wait status %#x",
1416 status);
1417 }
1418 }
1419 /* Else: NOMMU case, we have no way to sync.
1420 * Just attach to it as soon as possible.
1421 * This means that we may miss a few first syscalls...
1422 */
1423
1424 if (ptrace_attach_or_seize(pid)) {
1425 kill_save_errno(pid, SIGKILL);
1426 perror_msg_and_die("attach: ptrace(%s, %d)",
1427 ptrace_attach_cmd, pid);
1428 }
1429 if (!NOMMU_SYSTEM)
1430 kill(pid, SIGCONT);
1431 }
1432 tcp = alloctcb(pid);
1433 tcp->flags |= TCB_ATTACHED | TCB_STARTUP
1434 | TCB_SKIP_DETACH_ON_FIRST_EXEC
1435 | (NOMMU_SYSTEM ? 0 : (TCB_HIDE_LOG | post_attach_sigstop));
1436 newoutf(tcp);
1437 }
1438 else {
1439 /* With -D, we are *child* here, the tracee is our parent. */
1440 strace_child = strace_tracer_pid;
1441 strace_tracer_pid = getpid();
1442 tcp = alloctcb(strace_child);
1443 tcp->flags |= TCB_SKIP_DETACH_ON_FIRST_EXEC | TCB_HIDE_LOG;
1444 /* attaching will be done later, by startup_attach */
1445 /* note: we don't do newoutf(tcp) here either! */
1446
1447 /* NOMMU BUG! -D mode is active, we (child) return,
1448 * and we will scribble over parent's stack!
1449 * When parent later unpauses, it segfaults.
1450 *
1451 * We work around it
1452 * (1) by declaring exec_or_die() NORETURN,
1453 * hopefully compiler will just jump to it
1454 * instead of call (won't push anything to stack),
1455 * (2) by trying very hard in exec_or_die()
1456 * to not use any stack,
1457 * (3) having a really big (PATH_MAX) stack object
1458 * in this function, which creates a "buffer" between
1459 * child's and parent's stack pointers.
1460 * This may save us if (1) and (2) failed
1461 * and compiler decided to use stack in exec_or_die() anyway
1462 * (happens on i386 because of stack parameter passing).
1463 *
1464 * A cleaner solution is to use makecontext + setcontext
1465 * to create a genuine separate stack and execute on it.
1466 */
1467 }
1468 /*
1469 * A case where straced process is part of a pipe:
1470 * { sleep 1; yes | head -n99999; } | strace -o/dev/null sh -c 'exec <&-; sleep 9'
1471 * If strace won't close its fd#0, closing it in tracee is not enough:
1472 * the pipe is still open, it has a reader. Thus, "head" will not get its
1473 * SIGPIPE at once, on the first write.
1474 *
1475 * Preventing it by redirecting strace's stdin/out.
1476 * (Don't leave fds 0 and 1 closed, this is bad practice: future opens
1477 * will reuse them, unexpectedly making a newly opened object "stdin").
1478 */
1479 redirect_standard_fds();
1480 }
1481
1482 #if USE_SEIZE
1483 static void
test_ptrace_seize(void)1484 test_ptrace_seize(void)
1485 {
1486 int pid;
1487
1488 /* Need fork for test. NOMMU has no forks */
1489 if (NOMMU_SYSTEM) {
1490 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1491 return;
1492 }
1493
1494 pid = fork();
1495 if (pid < 0)
1496 perror_msg_and_die("fork");
1497
1498 if (pid == 0) {
1499 pause();
1500 _exit(0);
1501 }
1502
1503 /* PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After
1504 * attaching tracee continues to run unless a trap condition occurs.
1505 * PTRACE_SEIZE doesn't affect signal or group stop state.
1506 */
1507 if (ptrace(PTRACE_SEIZE, pid, 0, 0) == 0) {
1508 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1509 } else if (debug_flag) {
1510 error_msg("PTRACE_SEIZE doesn't work");
1511 }
1512
1513 kill(pid, SIGKILL);
1514
1515 while (1) {
1516 int status, tracee_pid;
1517
1518 errno = 0;
1519 tracee_pid = waitpid(pid, &status, 0);
1520 if (tracee_pid <= 0) {
1521 if (errno == EINTR)
1522 continue;
1523 perror_msg_and_die("%s: unexpected wait result %d",
1524 __func__, tracee_pid);
1525 }
1526 if (WIFSIGNALED(status)) {
1527 return;
1528 }
1529 error_msg_and_die("%s: unexpected wait status %#x",
1530 __func__, status);
1531 }
1532 }
1533 #else /* !USE_SEIZE */
1534 # define test_ptrace_seize() ((void)0)
1535 #endif
1536
1537 static unsigned
get_os_release(void)1538 get_os_release(void)
1539 {
1540 unsigned rel;
1541 const char *p;
1542 struct utsname u;
1543 if (uname(&u) < 0)
1544 perror_msg_and_die("uname");
1545 /* u.release has this form: "3.2.9[-some-garbage]" */
1546 rel = 0;
1547 p = u.release;
1548 for (;;) {
1549 if (!(*p >= '0' && *p <= '9'))
1550 error_msg_and_die("Bad OS release string: '%s'", u.release);
1551 /* Note: this open-codes KERNEL_VERSION(): */
1552 rel = (rel << 8) | atoi(p);
1553 if (rel >= KERNEL_VERSION(1,0,0))
1554 break;
1555 while (*p >= '0' && *p <= '9')
1556 p++;
1557 if (*p != '.') {
1558 if (rel >= KERNEL_VERSION(0,1,0)) {
1559 /* "X.Y-something" means "X.Y.0" */
1560 rel <<= 8;
1561 break;
1562 }
1563 error_msg_and_die("Bad OS release string: '%s'", u.release);
1564 }
1565 p++;
1566 }
1567 return rel;
1568 }
1569
1570 /*
1571 * Initialization part of main() was eating much stack (~0.5k),
1572 * which was unused after init.
1573 * We can reuse it if we move init code into a separate function.
1574 *
1575 * Don't want main() to inline us and defeat the reason
1576 * we have a separate function.
1577 */
1578 static void ATTRIBUTE_NOINLINE
init(int argc,char * argv[])1579 init(int argc, char *argv[])
1580 {
1581 int c, i;
1582 int optF = 0;
1583 struct sigaction sa;
1584
1585 progname = argv[0] ? argv[0] : "strace";
1586
1587 /* Make sure SIGCHLD has the default action so that waitpid
1588 definitely works without losing track of children. The user
1589 should not have given us a bogus state to inherit, but he might
1590 have. Arguably we should detect SIG_IGN here and pass it on
1591 to children, but probably noone really needs that. */
1592 signal(SIGCHLD, SIG_DFL);
1593
1594 strace_tracer_pid = getpid();
1595
1596 os_release = get_os_release();
1597
1598 shared_log = stderr;
1599 set_sortby(DEFAULT_SORTBY);
1600 set_personality(DEFAULT_PERSONALITY);
1601 qualify("trace=all");
1602 qualify("abbrev=all");
1603 qualify("verbose=all");
1604 #if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
1605 # error Bug in DEFAULT_QUAL_FLAGS
1606 #endif
1607 qualify("signal=all");
1608 while ((c = getopt(argc, argv,
1609 "+b:cCdfFhiqrtTvVwxyz"
1610 #ifdef USE_LIBUNWIND
1611 "k"
1612 #endif
1613 "D"
1614 "a:e:o:O:p:s:S:u:E:P:I:")) != EOF) {
1615 switch (c) {
1616 case 'b':
1617 if (strcmp(optarg, "execve") != 0)
1618 error_msg_and_die("Syscall '%s' for -b isn't supported",
1619 optarg);
1620 detach_on_execve = 1;
1621 break;
1622 case 'c':
1623 if (cflag == CFLAG_BOTH) {
1624 error_msg_and_help("-c and -C are mutually exclusive");
1625 }
1626 cflag = CFLAG_ONLY_STATS;
1627 break;
1628 case 'C':
1629 if (cflag == CFLAG_ONLY_STATS) {
1630 error_msg_and_help("-c and -C are mutually exclusive");
1631 }
1632 cflag = CFLAG_BOTH;
1633 break;
1634 case 'd':
1635 debug_flag = 1;
1636 break;
1637 case 'D':
1638 daemonized_tracer = 1;
1639 break;
1640 case 'F':
1641 optF = 1;
1642 break;
1643 case 'f':
1644 followfork++;
1645 break;
1646 case 'h':
1647 usage();
1648 break;
1649 case 'i':
1650 iflag = 1;
1651 break;
1652 case 'q':
1653 qflag++;
1654 break;
1655 case 'r':
1656 rflag = 1;
1657 break;
1658 case 't':
1659 tflag++;
1660 break;
1661 case 'T':
1662 Tflag = 1;
1663 break;
1664 case 'w':
1665 count_wallclock = 1;
1666 break;
1667 case 'x':
1668 xflag++;
1669 break;
1670 case 'y':
1671 show_fd_path++;
1672 break;
1673 case 'v':
1674 qualify("abbrev=none");
1675 break;
1676 case 'V':
1677 print_version();
1678 exit(0);
1679 break;
1680 case 'z':
1681 not_failing_only = 1;
1682 break;
1683 case 'a':
1684 acolumn = string_to_uint(optarg);
1685 if (acolumn < 0)
1686 error_opt_arg(c, optarg);
1687 break;
1688 case 'e':
1689 qualify(optarg);
1690 break;
1691 case 'o':
1692 outfname = xstrdup(optarg);
1693 break;
1694 case 'O':
1695 i = string_to_uint(optarg);
1696 if (i < 0)
1697 error_opt_arg(c, optarg);
1698 set_overhead(i);
1699 break;
1700 case 'p':
1701 process_opt_p_list(optarg);
1702 break;
1703 case 'P':
1704 pathtrace_select(optarg);
1705 break;
1706 case 's':
1707 i = string_to_uint(optarg);
1708 if (i < 0)
1709 error_opt_arg(c, optarg);
1710 max_strlen = i;
1711 break;
1712 case 'S':
1713 set_sortby(optarg);
1714 break;
1715 case 'u':
1716 username = xstrdup(optarg);
1717 break;
1718 #ifdef USE_LIBUNWIND
1719 case 'k':
1720 stack_trace_enabled = true;
1721 break;
1722 #endif
1723 case 'E':
1724 if (putenv(optarg) < 0)
1725 die_out_of_memory();
1726 break;
1727 case 'I':
1728 opt_intr = string_to_uint_upto(optarg, NUM_INTR_OPTS - 1);
1729 if (opt_intr <= 0)
1730 error_opt_arg(c, optarg);
1731 break;
1732 default:
1733 error_msg_and_help(NULL);
1734 break;
1735 }
1736 }
1737 argv += optind;
1738 /* argc -= optind; - no need, argc is not used below */
1739
1740 acolumn_spaces = xmalloc(acolumn + 1);
1741 memset(acolumn_spaces, ' ', acolumn);
1742 acolumn_spaces[acolumn] = '\0';
1743
1744 if (!argv[0] && !nprocs) {
1745 error_msg_and_help("must have PROG [ARGS] or -p PID");
1746 }
1747
1748 if (!argv[0] && daemonized_tracer) {
1749 error_msg_and_help("PROG [ARGS] must be specified with -D");
1750 }
1751
1752 if (!followfork)
1753 followfork = optF;
1754
1755 if (followfork >= 2 && cflag) {
1756 error_msg_and_help("(-c or -C) and -ff are mutually exclusive");
1757 }
1758
1759 if (count_wallclock && !cflag) {
1760 error_msg_and_help("-w must be given with (-c or -C)");
1761 }
1762
1763 if (cflag == CFLAG_ONLY_STATS) {
1764 if (iflag)
1765 error_msg("-%c has no effect with -c", 'i');
1766 #ifdef USE_LIBUNWIND
1767 if (stack_trace_enabled)
1768 error_msg("-%c has no effect with -c", 'k');
1769 #endif
1770 if (rflag)
1771 error_msg("-%c has no effect with -c", 'r');
1772 if (tflag)
1773 error_msg("-%c has no effect with -c", 't');
1774 if (Tflag)
1775 error_msg("-%c has no effect with -c", 'T');
1776 if (show_fd_path)
1777 error_msg("-%c has no effect with -c", 'y');
1778 }
1779
1780 if (rflag) {
1781 if (tflag > 1)
1782 error_msg("-tt has no effect with -r");
1783 tflag = 1;
1784 }
1785
1786 #ifdef USE_LIBUNWIND
1787 if (stack_trace_enabled) {
1788 unsigned int tcbi;
1789
1790 unwind_init();
1791 for (tcbi = 0; tcbi < tcbtabsize; ++tcbi) {
1792 unwind_tcb_init(tcbtab[tcbi]);
1793 }
1794 }
1795 #endif
1796
1797 /* See if they want to run as another user. */
1798 if (username != NULL) {
1799 struct passwd *pent;
1800
1801 if (getuid() != 0 || geteuid() != 0) {
1802 error_msg_and_die("You must be root to use the -u option");
1803 }
1804 pent = getpwnam(username);
1805 if (pent == NULL) {
1806 error_msg_and_die("Cannot find user '%s'", username);
1807 }
1808 run_uid = pent->pw_uid;
1809 run_gid = pent->pw_gid;
1810 }
1811 else {
1812 run_uid = getuid();
1813 run_gid = getgid();
1814 }
1815
1816 if (followfork)
1817 ptrace_setoptions |= PTRACE_O_TRACECLONE |
1818 PTRACE_O_TRACEFORK |
1819 PTRACE_O_TRACEVFORK;
1820 if (debug_flag)
1821 error_msg("ptrace_setoptions = %#x", ptrace_setoptions);
1822 test_ptrace_seize();
1823
1824 /*
1825 * Is something weird with our stdin and/or stdout -
1826 * for example, may they be not open? In this case,
1827 * ensure that none of the future opens uses them.
1828 *
1829 * This was seen in the wild when /proc/sys/kernel/core_pattern
1830 * was set to "|/bin/strace -o/tmp/LOG PROG":
1831 * kernel runs coredump helper with fd#0 open but fd#1 closed (!),
1832 * therefore LOG gets opened to fd#1, and fd#1 is closed by
1833 * "don't hold up stdin/out open" code soon after.
1834 */
1835 ensure_standard_fds_opened();
1836
1837 /* Check if they want to redirect the output. */
1838 if (outfname) {
1839 /* See if they want to pipe the output. */
1840 if (outfname[0] == '|' || outfname[0] == '!') {
1841 /*
1842 * We can't do the <outfname>.PID funny business
1843 * when using popen, so prohibit it.
1844 */
1845 if (followfork >= 2)
1846 error_msg_and_help("piping the output and -ff are mutually exclusive");
1847 shared_log = strace_popen(outfname + 1);
1848 }
1849 else if (followfork < 2)
1850 shared_log = strace_fopen(outfname);
1851 } else {
1852 /* -ff without -o FILE is the same as single -f */
1853 if (followfork >= 2)
1854 followfork = 1;
1855 }
1856
1857 if (!outfname || outfname[0] == '|' || outfname[0] == '!') {
1858 setvbuf(shared_log, NULL, _IOLBF, 0);
1859 }
1860 if (outfname && argv[0]) {
1861 if (!opt_intr)
1862 opt_intr = INTR_NEVER;
1863 if (!qflag)
1864 qflag = 1;
1865 }
1866 if (!opt_intr)
1867 opt_intr = INTR_WHILE_WAIT;
1868
1869 /* argv[0] -pPID -oFILE Default interactive setting
1870 * yes * 0 INTR_WHILE_WAIT
1871 * no 1 0 INTR_WHILE_WAIT
1872 * yes * 1 INTR_NEVER
1873 * no 1 1 INTR_WHILE_WAIT
1874 */
1875
1876 sigemptyset(&empty_set);
1877 sigemptyset(&blocked_set);
1878
1879 /* startup_child() must be called before the signal handlers get
1880 * installed below as they are inherited into the spawned process.
1881 * Also we do not need to be protected by them as during interruption
1882 * in the startup_child() mode we kill the spawned process anyway.
1883 */
1884 if (argv[0]) {
1885 startup_child(argv);
1886 }
1887
1888 sa.sa_handler = SIG_IGN;
1889 sigemptyset(&sa.sa_mask);
1890 sa.sa_flags = 0;
1891 sigaction(SIGTTOU, &sa, NULL); /* SIG_IGN */
1892 sigaction(SIGTTIN, &sa, NULL); /* SIG_IGN */
1893 if (opt_intr != INTR_ANYWHERE) {
1894 if (opt_intr == INTR_BLOCK_TSTP_TOO)
1895 sigaction(SIGTSTP, &sa, NULL); /* SIG_IGN */
1896 /*
1897 * In interactive mode (if no -o OUTFILE, or -p PID is used),
1898 * fatal signals are blocked while syscall stop is processed,
1899 * and acted on in between, when waiting for new syscall stops.
1900 * In non-interactive mode, signals are ignored.
1901 */
1902 if (opt_intr == INTR_WHILE_WAIT) {
1903 sigaddset(&blocked_set, SIGHUP);
1904 sigaddset(&blocked_set, SIGINT);
1905 sigaddset(&blocked_set, SIGQUIT);
1906 sigaddset(&blocked_set, SIGPIPE);
1907 sigaddset(&blocked_set, SIGTERM);
1908 sa.sa_handler = interrupt;
1909 }
1910 /* SIG_IGN, or set handler for these */
1911 sigaction(SIGHUP, &sa, NULL);
1912 sigaction(SIGINT, &sa, NULL);
1913 sigaction(SIGQUIT, &sa, NULL);
1914 sigaction(SIGPIPE, &sa, NULL);
1915 sigaction(SIGTERM, &sa, NULL);
1916 }
1917 if (nprocs != 0 || daemonized_tracer)
1918 startup_attach();
1919
1920 /* Do we want pids printed in our -o OUTFILE?
1921 * -ff: no (every pid has its own file); or
1922 * -f: yes (there can be more pids in the future); or
1923 * -p PID1,PID2: yes (there are already more than one pid)
1924 */
1925 print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
1926 }
1927
1928 static struct tcb *
pid2tcb(int pid)1929 pid2tcb(int pid)
1930 {
1931 unsigned int i;
1932
1933 if (pid <= 0)
1934 return NULL;
1935
1936 for (i = 0; i < tcbtabsize; i++) {
1937 struct tcb *tcp = tcbtab[i];
1938 if (tcp->pid == pid)
1939 return tcp;
1940 }
1941
1942 return NULL;
1943 }
1944
1945 static void
cleanup(void)1946 cleanup(void)
1947 {
1948 unsigned int i;
1949 struct tcb *tcp;
1950 int fatal_sig;
1951
1952 /* 'interrupted' is a volatile object, fetch it only once */
1953 fatal_sig = interrupted;
1954 if (!fatal_sig)
1955 fatal_sig = SIGTERM;
1956
1957 for (i = 0; i < tcbtabsize; i++) {
1958 tcp = tcbtab[i];
1959 if (!tcp->pid)
1960 continue;
1961 if (debug_flag)
1962 error_msg("cleanup: looking at pid %u", tcp->pid);
1963 if (tcp->pid == strace_child) {
1964 kill(tcp->pid, SIGCONT);
1965 kill(tcp->pid, fatal_sig);
1966 }
1967 detach(tcp);
1968 }
1969 if (cflag)
1970 call_summary(shared_log);
1971 }
1972
1973 static void
interrupt(int sig)1974 interrupt(int sig)
1975 {
1976 interrupted = sig;
1977 }
1978
1979 static void
print_debug_info(const int pid,int status)1980 print_debug_info(const int pid, int status)
1981 {
1982 const unsigned int event = (unsigned int) status >> 16;
1983 char buf[sizeof("WIFEXITED,exitcode=%u") + sizeof(int)*3 /*paranoia:*/ + 16];
1984 char evbuf[sizeof(",EVENT_VFORK_DONE (%u)") + sizeof(int)*3 /*paranoia:*/ + 16];
1985
1986 strcpy(buf, "???");
1987 if (WIFSIGNALED(status))
1988 #ifdef WCOREDUMP
1989 sprintf(buf, "WIFSIGNALED,%ssig=%s",
1990 WCOREDUMP(status) ? "core," : "",
1991 signame(WTERMSIG(status)));
1992 #else
1993 sprintf(buf, "WIFSIGNALED,sig=%s",
1994 signame(WTERMSIG(status)));
1995 #endif
1996 if (WIFEXITED(status))
1997 sprintf(buf, "WIFEXITED,exitcode=%u", WEXITSTATUS(status));
1998 if (WIFSTOPPED(status))
1999 sprintf(buf, "WIFSTOPPED,sig=%s", signame(WSTOPSIG(status)));
2000 #ifdef WIFCONTINUED
2001 /* Should never be seen */
2002 if (WIFCONTINUED(status))
2003 strcpy(buf, "WIFCONTINUED");
2004 #endif
2005 evbuf[0] = '\0';
2006 if (event != 0) {
2007 static const char *const event_names[] = {
2008 [PTRACE_EVENT_CLONE] = "CLONE",
2009 [PTRACE_EVENT_FORK] = "FORK",
2010 [PTRACE_EVENT_VFORK] = "VFORK",
2011 [PTRACE_EVENT_VFORK_DONE] = "VFORK_DONE",
2012 [PTRACE_EVENT_EXEC] = "EXEC",
2013 [PTRACE_EVENT_EXIT] = "EXIT",
2014 /* [PTRACE_EVENT_STOP (=128)] would make biggish array */
2015 };
2016 const char *e = "??";
2017 if (event < ARRAY_SIZE(event_names))
2018 e = event_names[event];
2019 else if (event == PTRACE_EVENT_STOP)
2020 e = "STOP";
2021 sprintf(evbuf, ",EVENT_%s (%u)", e, event);
2022 }
2023 error_msg("[wait(0x%06x) = %u] %s%s", status, pid, buf, evbuf);
2024 }
2025
2026 static struct tcb *
maybe_allocate_tcb(const int pid,int status)2027 maybe_allocate_tcb(const int pid, int status)
2028 {
2029 if (!WIFSTOPPED(status)) {
2030 if (detach_on_execve && pid == strace_child) {
2031 /* example: strace -bexecve sh -c 'exec true' */
2032 strace_child = 0;
2033 return NULL;
2034 }
2035 /*
2036 * This can happen if we inherited an unknown child.
2037 * Example: (sleep 1 & exec strace true)
2038 */
2039 error_msg("Exit of unknown pid %u ignored", pid);
2040 return NULL;
2041 }
2042 if (followfork) {
2043 /* We assume it's a fork/vfork/clone child */
2044 struct tcb *tcp = alloctcb(pid);
2045 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
2046 newoutf(tcp);
2047 if (!qflag)
2048 error_msg("Process %d attached", pid);
2049 return tcp;
2050 } else {
2051 /* This can happen if a clone call used
2052 * CLONE_PTRACE itself.
2053 */
2054 ptrace(PTRACE_CONT, pid, NULL, 0);
2055 error_msg("Stop of unknown pid %u seen, PTRACE_CONTed it", pid);
2056 return NULL;
2057 }
2058 }
2059
2060 static struct tcb *
maybe_switch_tcbs(struct tcb * tcp,const int pid)2061 maybe_switch_tcbs(struct tcb *tcp, const int pid)
2062 {
2063 FILE *fp;
2064 struct tcb *execve_thread;
2065 long old_pid = 0;
2066
2067 if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, &old_pid) < 0)
2068 return tcp;
2069 /* Avoid truncation in pid2tcb() param passing */
2070 if (old_pid <= 0 || old_pid == pid)
2071 return tcp;
2072 if ((unsigned long) old_pid > UINT_MAX)
2073 return tcp;
2074 execve_thread = pid2tcb(old_pid);
2075 /* It should be !NULL, but I feel paranoid */
2076 if (!execve_thread)
2077 return tcp;
2078
2079 if (execve_thread->curcol != 0) {
2080 /*
2081 * One case we are here is -ff:
2082 * try "strace -oLOG -ff test/threaded_execve"
2083 */
2084 fprintf(execve_thread->outf, " <pid changed to %d ...>\n", pid);
2085 /*execve_thread->curcol = 0; - no need, see code below */
2086 }
2087 /* Swap output FILEs (needed for -ff) */
2088 fp = execve_thread->outf;
2089 execve_thread->outf = tcp->outf;
2090 tcp->outf = fp;
2091 /* And their column positions */
2092 execve_thread->curcol = tcp->curcol;
2093 tcp->curcol = 0;
2094 /* Drop leader, but close execve'd thread outfile (if -ff) */
2095 droptcb(tcp);
2096 /* Switch to the thread, reusing leader's outfile and pid */
2097 tcp = execve_thread;
2098 tcp->pid = pid;
2099 if (cflag != CFLAG_ONLY_STATS) {
2100 printleader(tcp);
2101 tprintf("+++ superseded by execve in pid %lu +++\n", old_pid);
2102 line_ended();
2103 tcp->flags |= TCB_REPRINT;
2104 }
2105
2106 return tcp;
2107 }
2108
2109 static void
print_signalled(struct tcb * tcp,const int pid,int status)2110 print_signalled(struct tcb *tcp, const int pid, int status)
2111 {
2112 if (pid == strace_child) {
2113 exit_code = 0x100 | WTERMSIG(status);
2114 strace_child = 0;
2115 }
2116
2117 if (cflag != CFLAG_ONLY_STATS
2118 && is_number_in_set(WTERMSIG(status), &signal_set)) {
2119 printleader(tcp);
2120 #ifdef WCOREDUMP
2121 tprintf("+++ killed by %s %s+++\n",
2122 signame(WTERMSIG(status)),
2123 WCOREDUMP(status) ? "(core dumped) " : "");
2124 #else
2125 tprintf("+++ killed by %s +++\n",
2126 signame(WTERMSIG(status)));
2127 #endif
2128 line_ended();
2129 }
2130 }
2131
2132 static void
print_exited(struct tcb * tcp,const int pid,int status)2133 print_exited(struct tcb *tcp, const int pid, int status)
2134 {
2135 if (pid == strace_child) {
2136 exit_code = WEXITSTATUS(status);
2137 strace_child = 0;
2138 }
2139
2140 if (cflag != CFLAG_ONLY_STATS &&
2141 qflag < 2) {
2142 printleader(tcp);
2143 tprintf("+++ exited with %d +++\n", WEXITSTATUS(status));
2144 line_ended();
2145 }
2146 }
2147
2148 static void
print_stopped(struct tcb * tcp,const siginfo_t * si,const unsigned int sig)2149 print_stopped(struct tcb *tcp, const siginfo_t *si, const unsigned int sig)
2150 {
2151 if (cflag != CFLAG_ONLY_STATS
2152 && !hide_log(tcp)
2153 && is_number_in_set(sig, &signal_set)) {
2154 printleader(tcp);
2155 if (si) {
2156 tprintf("--- %s ", signame(sig));
2157 printsiginfo(si);
2158 tprints(" ---\n");
2159 } else
2160 tprintf("--- stopped by %s ---\n", signame(sig));
2161 line_ended();
2162 }
2163 }
2164
2165 static void
startup_tcb(struct tcb * tcp)2166 startup_tcb(struct tcb *tcp)
2167 {
2168 if (debug_flag)
2169 error_msg("pid %d has TCB_STARTUP, initializing it", tcp->pid);
2170
2171 tcp->flags &= ~TCB_STARTUP;
2172
2173 if (!use_seize) {
2174 if (debug_flag)
2175 error_msg("setting opts 0x%x on pid %d",
2176 ptrace_setoptions, tcp->pid);
2177 if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, ptrace_setoptions) < 0) {
2178 if (errno != ESRCH) {
2179 /* Should never happen, really */
2180 perror_msg_and_die("PTRACE_SETOPTIONS");
2181 }
2182 }
2183 }
2184 }
2185
2186 static void
print_event_exit(struct tcb * tcp)2187 print_event_exit(struct tcb *tcp)
2188 {
2189 if (entering(tcp) || filtered(tcp) || hide_log(tcp)
2190 || cflag == CFLAG_ONLY_STATS) {
2191 return;
2192 }
2193
2194 if (followfork < 2 && printing_tcp && printing_tcp != tcp
2195 && printing_tcp->curcol != 0) {
2196 current_tcp = printing_tcp;
2197 tprints(" <unfinished ...>\n");
2198 fflush(printing_tcp->outf);
2199 printing_tcp->curcol = 0;
2200 current_tcp = tcp;
2201 }
2202
2203 if ((followfork < 2 && printing_tcp != tcp)
2204 || (tcp->flags & TCB_REPRINT)) {
2205 tcp->flags &= ~TCB_REPRINT;
2206 printleader(tcp);
2207 tprintf("<... %s resumed>", tcp->s_ent->sys_name);
2208 }
2209
2210 if (!(tcp->sys_func_rval & RVAL_DECODED)) {
2211 /*
2212 * The decoder has probably decided to print something
2213 * on exiting syscall which is not going to happen.
2214 */
2215 tprints(" <unfinished ...>");
2216 }
2217 tprints(") ");
2218 tabto();
2219 tprints("= ?\n");
2220 line_ended();
2221 }
2222
2223 /* Returns true iff the main trace loop has to continue. */
2224 static bool
trace(void)2225 trace(void)
2226 {
2227 int pid;
2228 int wait_errno;
2229 int status;
2230 bool stopped;
2231 unsigned int sig;
2232 unsigned int event;
2233 struct tcb *tcp;
2234 struct rusage ru;
2235
2236 if (interrupted)
2237 return false;
2238
2239 /*
2240 * Used to exit simply when nprocs hits zero, but in this testcase:
2241 * int main() { _exit(!!fork()); }
2242 * under strace -f, parent sometimes (rarely) manages
2243 * to exit before we see the first stop of the child,
2244 * and we are losing track of it:
2245 * 19923 clone(...) = 19924
2246 * 19923 exit_group(1) = ?
2247 * 19923 +++ exited with 1 +++
2248 * Exiting only when wait() returns ECHILD works better.
2249 */
2250 if (popen_pid != 0) {
2251 /* However, if -o|logger is in use, we can't do that.
2252 * Can work around that by double-forking the logger,
2253 * but that loses the ability to wait for its completion
2254 * on exit. Oh well...
2255 */
2256 if (nprocs == 0)
2257 return false;
2258 }
2259
2260 if (interactive)
2261 sigprocmask(SIG_SETMASK, &empty_set, NULL);
2262 pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
2263 wait_errno = errno;
2264 if (interactive)
2265 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
2266
2267 if (pid < 0) {
2268 if (wait_errno == EINTR)
2269 return true;
2270 if (nprocs == 0 && wait_errno == ECHILD)
2271 return false;
2272 /*
2273 * If nprocs > 0, ECHILD is not expected,
2274 * treat it as any other error here:
2275 */
2276 errno = wait_errno;
2277 perror_msg_and_die("wait4(__WALL)");
2278 }
2279
2280 if (pid == popen_pid) {
2281 if (!WIFSTOPPED(status))
2282 popen_pid = 0;
2283 return true;
2284 }
2285
2286 if (debug_flag)
2287 print_debug_info(pid, status);
2288
2289 /* Look up 'pid' in our table. */
2290 tcp = pid2tcb(pid);
2291
2292 if (!tcp) {
2293 tcp = maybe_allocate_tcb(pid, status);
2294 if (!tcp)
2295 return true;
2296 }
2297
2298 if (WIFSTOPPED(status))
2299 get_regs(pid);
2300 else
2301 clear_regs();
2302
2303 event = (unsigned int) status >> 16;
2304
2305 if (event == PTRACE_EVENT_EXEC) {
2306 /*
2307 * Under Linux, execve changes pid to thread leader's pid,
2308 * and we see this changed pid on EVENT_EXEC and later,
2309 * execve sysexit. Leader "disappears" without exit
2310 * notification. Let user know that, drop leader's tcb,
2311 * and fix up pid in execve thread's tcb.
2312 * Effectively, execve thread's tcb replaces leader's tcb.
2313 *
2314 * BTW, leader is 'stuck undead' (doesn't report WIFEXITED
2315 * on exit syscall) in multithreaded programs exactly
2316 * in order to handle this case.
2317 *
2318 * PTRACE_GETEVENTMSG returns old pid starting from Linux 3.0.
2319 * On 2.6 and earlier, it can return garbage.
2320 */
2321 if (os_release >= KERNEL_VERSION(3,0,0))
2322 tcp = maybe_switch_tcbs(tcp, pid);
2323
2324 if (detach_on_execve) {
2325 if (tcp->flags & TCB_SKIP_DETACH_ON_FIRST_EXEC) {
2326 tcp->flags &= ~TCB_SKIP_DETACH_ON_FIRST_EXEC;
2327 } else {
2328 detach(tcp); /* do "-b execve" thingy */
2329 return true;
2330 }
2331 }
2332 }
2333
2334 /* Set current output file */
2335 current_tcp = tcp;
2336
2337 if (cflag) {
2338 tv_sub(&tcp->dtime, &ru.ru_stime, &tcp->stime);
2339 tcp->stime = ru.ru_stime;
2340 }
2341
2342 if (WIFSIGNALED(status)) {
2343 print_signalled(tcp, pid, status);
2344 droptcb(tcp);
2345 return true;
2346 }
2347
2348 if (WIFEXITED(status)) {
2349 print_exited(tcp, pid, status);
2350 droptcb(tcp);
2351 return true;
2352 }
2353
2354 if (!WIFSTOPPED(status)) {
2355 /*
2356 * Neither signalled, exited or stopped.
2357 * How could that be?
2358 */
2359 error_msg("pid %u not stopped!", pid);
2360 droptcb(tcp);
2361 return true;
2362 }
2363
2364 /* Is this the very first time we see this tracee stopped? */
2365 if (tcp->flags & TCB_STARTUP) {
2366 startup_tcb(tcp);
2367 if (get_scno(tcp) == 1)
2368 tcp->s_prev_ent = tcp->s_ent;
2369 }
2370
2371 sig = WSTOPSIG(status);
2372
2373 switch (event) {
2374 case 0:
2375 break;
2376 case PTRACE_EVENT_EXIT:
2377 print_event_exit(tcp);
2378 goto restart_tracee_with_sig_0;
2379 #if USE_SEIZE
2380 case PTRACE_EVENT_STOP:
2381 /*
2382 * PTRACE_INTERRUPT-stop or group-stop.
2383 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
2384 */
2385 switch (sig) {
2386 case SIGSTOP:
2387 case SIGTSTP:
2388 case SIGTTIN:
2389 case SIGTTOU:
2390 stopped = true;
2391 goto show_stopsig;
2392 }
2393 /* fall through */
2394 #endif
2395 default:
2396 goto restart_tracee_with_sig_0;
2397 }
2398
2399 /*
2400 * Is this post-attach SIGSTOP?
2401 * Interestingly, the process may stop
2402 * with STOPSIG equal to some other signal
2403 * than SIGSTOP if we happend to attach
2404 * just before the process takes a signal.
2405 */
2406 if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
2407 if (debug_flag)
2408 error_msg("ignored SIGSTOP on pid %d", tcp->pid);
2409 tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
2410 goto restart_tracee_with_sig_0;
2411 }
2412
2413 if (sig != syscall_trap_sig) {
2414 siginfo_t si = {};
2415
2416 /*
2417 * True if tracee is stopped by signal
2418 * (as opposed to "tracee received signal").
2419 * TODO: shouldn't we check for errno == EINVAL too?
2420 * We can get ESRCH instead, you know...
2421 */
2422 stopped = ptrace(PTRACE_GETSIGINFO, pid, 0, &si) < 0;
2423 #if USE_SEIZE
2424 show_stopsig:
2425 #endif
2426 print_stopped(tcp, stopped ? NULL : &si, sig);
2427
2428 if (!stopped)
2429 /* It's signal-delivery-stop. Inject the signal */
2430 goto restart_tracee;
2431
2432 /* It's group-stop */
2433 if (use_seize) {
2434 /*
2435 * This ends ptrace-stop, but does *not* end group-stop.
2436 * This makes stopping signals work properly on straced process
2437 * (that is, process really stops. It used to continue to run).
2438 */
2439 if (ptrace_restart(PTRACE_LISTEN, tcp, 0) < 0) {
2440 /* Note: ptrace_restart emitted error message */
2441 exit_code = 1;
2442 return false;
2443 }
2444 return true;
2445 }
2446 /* We don't have PTRACE_LISTEN support... */
2447 goto restart_tracee;
2448 }
2449
2450 /* We handled quick cases, we are permitted to interrupt now. */
2451 if (interrupted)
2452 return false;
2453
2454 /*
2455 * This should be syscall entry or exit.
2456 * Handle it.
2457 */
2458 sig = 0;
2459 if (trace_syscall(tcp, &sig) < 0) {
2460 /*
2461 * ptrace() failed in trace_syscall().
2462 * Likely a result of process disappearing mid-flight.
2463 * Observed case: exit_group() or SIGKILL terminating
2464 * all processes in thread group.
2465 * We assume that ptrace error was caused by process death.
2466 * We used to detach(tcp) here, but since we no longer
2467 * implement "detach before death" policy/hack,
2468 * we can let this process to report its death to us
2469 * normally, via WIFEXITED or WIFSIGNALED wait status.
2470 */
2471 return true;
2472 }
2473 goto restart_tracee;
2474
2475 restart_tracee_with_sig_0:
2476 sig = 0;
2477
2478 restart_tracee:
2479 if (ptrace_restart(PTRACE_SYSCALL, tcp, sig) < 0) {
2480 /* Note: ptrace_restart emitted error message */
2481 exit_code = 1;
2482 return false;
2483 }
2484
2485 return true;
2486 }
2487
2488 int
main(int argc,char * argv[])2489 main(int argc, char *argv[])
2490 {
2491 init(argc, argv);
2492
2493 exit_code = !nprocs;
2494
2495 while (trace())
2496 ;
2497
2498 cleanup();
2499 fflush(NULL);
2500 if (shared_log != stderr)
2501 fclose(shared_log);
2502 if (popen_pid) {
2503 while (waitpid(popen_pid, NULL, 0) < 0 && errno == EINTR)
2504 ;
2505 }
2506 if (exit_code > 0xff) {
2507 /* Avoid potential core file clobbering. */
2508 struct_rlimit rlim = {0, 0};
2509 set_rlimit(RLIMIT_CORE, &rlim);
2510
2511 /* Child was killed by a signal, mimic that. */
2512 exit_code &= 0xff;
2513 signal(exit_code, SIG_DFL);
2514 raise(exit_code);
2515 /* Paranoia - what if this signal is not fatal?
2516 Exit with 128 + signo then. */
2517 exit_code += 128;
2518 }
2519
2520 return exit_code;
2521 }
2522