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 * Copyright (c) 1999-2018 The strace developers.
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. The name of the author may not be used to endorse or promote products
18 * derived from this software without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
21 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
22 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
23 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
25 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
29 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #include "defs.h"
33 #include <stdarg.h>
34 #include <limits.h>
35 #include <fcntl.h>
36 #include "ptrace.h"
37 #include <signal.h>
38 #include <sys/resource.h>
39 #include <sys/wait.h>
40 #include <sys/stat.h>
41 #ifdef HAVE_PATHS_H
42 # include <paths.h>
43 #endif
44 #include <pwd.h>
45 #include <grp.h>
46 #include <dirent.h>
47 #include <locale.h>
48 #include <sys/utsname.h>
49 #ifdef HAVE_PRCTL
50 # include <sys/prctl.h>
51 #endif
52 #include <asm/unistd.h>
53
54 #include "largefile_wrappers.h"
55 #include "mmap_cache.h"
56 #include "number_set.h"
57 #include "scno.h"
58 #include "printsiginfo.h"
59 #include "trace_event.h"
60 #include "xstring.h"
61 #include "delay.h"
62
63 /* In some libc, these aren't declared. Do it ourself: */
64 extern char **environ;
65 extern int optind;
66 extern char *optarg;
67
68 #ifdef ENABLE_STACKTRACE
69 /* if this is true do the stack trace for every system call */
70 bool stack_trace_enabled;
71 #endif
72
73 #define my_tkill(tid, sig) syscall(__NR_tkill, (tid), (sig))
74
75 /* Glue for systems without a MMU that cannot provide fork() */
76 #if !defined(HAVE_FORK)
77 # undef NOMMU_SYSTEM
78 # define NOMMU_SYSTEM 1
79 #endif
80 #if NOMMU_SYSTEM
81 # define fork() vfork()
82 #endif
83
84 const unsigned int syscall_trap_sig = SIGTRAP | 0x80;
85
86 cflag_t cflag = CFLAG_NONE;
87 unsigned int followfork;
88 unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC
89 | PTRACE_O_TRACEEXIT;
90 unsigned int xflag;
91 bool debug_flag;
92 bool Tflag;
93 bool iflag;
94 bool count_wallclock;
95 unsigned int qflag;
96 static unsigned int tflag;
97 static bool rflag;
98 static bool print_pid_pfx;
99
100 /* -I n */
101 enum {
102 INTR_NOT_SET = 0,
103 INTR_ANYWHERE = 1, /* don't block/ignore any signals */
104 INTR_WHILE_WAIT = 2, /* block fatal signals while decoding syscall. default */
105 INTR_NEVER = 3, /* block fatal signals. default if '-o FILE PROG' */
106 INTR_BLOCK_TSTP_TOO = 4, /* block fatal signals and SIGTSTP (^Z) */
107 NUM_INTR_OPTS
108 };
109 static int opt_intr;
110 /* We play with signal mask only if this mode is active: */
111 #define interactive (opt_intr == INTR_WHILE_WAIT)
112
113 /*
114 * daemonized_tracer supports -D option.
115 * With this option, strace forks twice.
116 * Unlike normal case, with -D *grandparent* process exec's,
117 * becoming a traced process. Child exits (this prevents traced process
118 * from having children it doesn't expect to have), and grandchild
119 * attaches to grandparent similarly to strace -p PID.
120 * This allows for more transparent interaction in cases
121 * when process and its parent are communicating via signals,
122 * wait() etc. Without -D, strace process gets lodged in between,
123 * disrupting parent<->child link.
124 */
125 static bool daemonized_tracer;
126
127 static int post_attach_sigstop = TCB_IGNORE_ONE_SIGSTOP;
128 #define use_seize (post_attach_sigstop == 0)
129
130 /* Sometimes we want to print only succeeding syscalls. */
131 bool not_failing_only;
132
133 /* Show path associated with fd arguments */
134 unsigned int show_fd_path;
135
136 static bool detach_on_execve;
137
138 static int exit_code;
139 static int strace_child;
140 static int strace_tracer_pid;
141
142 static const char *username;
143 static uid_t run_uid;
144 static gid_t run_gid;
145
146 unsigned int max_strlen = DEFAULT_STRLEN;
147 static int acolumn = DEFAULT_ACOLUMN;
148 static char *acolumn_spaces;
149
150 /* Default output style for xlat entities */
151 enum xlat_style xlat_verbosity = XLAT_STYLE_ABBREV;
152
153 static const char *outfname;
154 /* If -ff, points to stderr. Else, it's our common output log */
155 static FILE *shared_log;
156 static bool open_append;
157
158 struct tcb *printing_tcp;
159 static struct tcb *current_tcp;
160
161 struct tcb_wait_data {
162 enum trace_event te; /**< Event passed to dispatch_event() */
163 int status; /**< status, returned by wait4() */
164 siginfo_t si; /**< siginfo, returned by PTRACE_GETSIGINFO */
165 };
166
167 static struct tcb **tcbtab;
168 static unsigned int nprocs;
169 static size_t tcbtabsize;
170
171 #ifndef HAVE_PROGRAM_INVOCATION_NAME
172 char *program_invocation_name;
173 #endif
174
175 unsigned os_release; /* generated from uname()'s u.release */
176
177 static void detach(struct tcb *tcp);
178 static void cleanup(void);
179 static void interrupt(int sig);
180
181 #ifdef HAVE_SIG_ATOMIC_T
182 static volatile sig_atomic_t interrupted, restart_failed;
183 #else
184 static volatile int interrupted, restart_failed;
185 #endif
186
187 static sigset_t timer_set;
188 static void timer_sighandler(int);
189
190 #ifndef HAVE_STRERROR
191
192 #if !HAVE_DECL_SYS_ERRLIST
193 extern int sys_nerr;
194 extern char *sys_errlist[];
195 #endif
196
197 const char *
strerror(int err_no)198 strerror(int err_no)
199 {
200 static char buf[sizeof("Unknown error %d") + sizeof(int)*3];
201
202 if (err_no < 1 || err_no >= sys_nerr) {
203 xsprintf(buf, "Unknown error %d", err_no);
204 return buf;
205 }
206 return sys_errlist[err_no];
207 }
208
209 #endif /* HAVE_STERRROR */
210
211 static void
print_version(void)212 print_version(void)
213 {
214 static const char features[] =
215 #ifdef ENABLE_STACKTRACE
216 " stack-trace=" USE_UNWINDER
217 #endif
218 #ifdef USE_DEMANGLE
219 " stack-demangle"
220 #endif
221 #if SUPPORTED_PERSONALITIES > 1
222 # if defined HAVE_M32_MPERS
223 " m32-mpers"
224 # else
225 " no-m32-mpers"
226 # endif
227 #endif /* SUPPORTED_PERSONALITIES > 1 */
228 #if SUPPORTED_PERSONALITIES > 2
229 # if defined HAVE_MX32_MPERS
230 " mx32-mpers"
231 # else
232 " no-mx32-mpers"
233 # endif
234 #endif /* SUPPORTED_PERSONALITIES > 2 */
235 "";
236
237 printf("%s -- version %s\n"
238 "Copyright (c) 1991-%s The strace developers <%s>.\n"
239 "This is free software; see the source for copying conditions. There is NO\n"
240 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n",
241 PACKAGE_NAME, PACKAGE_VERSION, COPYRIGHT_YEAR, PACKAGE_URL);
242 printf("\nOptional features enabled:%s\n",
243 features[0] ? features : " (none)");
244 }
245
246 static void
usage(void)247 usage(void)
248 {
249 printf("\
250 usage: strace [-CdffhiqrtttTvVwxxy] [-I n] [-e expr]...\n\
251 [-a column] [-o file] [-s strsize] [-P path]...\n\
252 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
253 or: strace -c[dfw] [-I n] [-e expr]... [-O overhead] [-S sortby]\n\
254 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
255 \n\
256 Output format:\n\
257 -a column alignment COLUMN for printing syscall results (default %d)\n\
258 -i print instruction pointer at time of syscall\n\
259 "
260 #ifdef ENABLE_STACKTRACE
261 "\
262 -k obtain stack trace between each syscall\n\
263 "
264 #endif
265 "\
266 -o file send trace output to FILE instead of stderr\n\
267 -q suppress messages about attaching, detaching, etc.\n\
268 -r print relative timestamp\n\
269 -s strsize limit length of print strings to STRSIZE chars (default %d)\n\
270 -t print absolute timestamp\n\
271 -tt print absolute timestamp with usecs\n\
272 -T print time spent in each syscall\n\
273 -x print non-ascii strings in hex\n\
274 -xx print all strings in hex\n\
275 -y print paths associated with file descriptor arguments\n\
276 -yy print protocol specific information associated with socket file descriptors\n\
277 \n\
278 Statistics:\n\
279 -c count time, calls, and errors for each syscall and report summary\n\
280 -C like -c but also print regular output\n\
281 -O overhead set overhead for tracing syscalls to OVERHEAD usecs\n\
282 -S sortby sort syscall counts by: time, calls, name, nothing (default %s)\n\
283 -w summarise syscall latency (default is system time)\n\
284 \n\
285 Filtering:\n\
286 -e expr a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
287 options: trace, abbrev, verbose, raw, signal, read, write, fault, inject, kvm"
288 "\n\
289 -P path trace accesses to path\n\
290 \n\
291 Tracing:\n\
292 -b execve detach on execve syscall\n\
293 -D run tracer process as a detached grandchild, not as parent\n\
294 -f follow forks\n\
295 -ff follow forks with output into separate files\n\
296 -I interruptible\n\
297 1: no signals are blocked\n\
298 2: fatal signals are blocked while decoding syscall (default)\n\
299 3: fatal signals are always blocked (default if '-o FILE PROG')\n\
300 4: fatal signals and SIGTSTP (^Z) are always blocked\n\
301 (useful to make 'strace -o FILE PROG' not stop on ^Z)\n\
302 \n\
303 Startup:\n\
304 -E var remove var from the environment for command\n\
305 -E var=val put var=val in the environment for command\n\
306 -p pid trace process with process id PID, may be repeated\n\
307 -u username run command as username handling setuid and/or setgid\n\
308 \n\
309 Miscellaneous:\n\
310 -d enable debug output to stderr\n\
311 -v verbose mode: print unabbreviated argv, stat, termios, etc. args\n\
312 -h print help message\n\
313 -V print version\n\
314 "
315 /* ancient, no one should use it
316 -F -- attempt to follow vforks (deprecated, use -f)\n\
317 */
318 /* this is broken, so don't document it
319 -z -- print only succeeding syscalls\n\
320 */
321 , DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
322 exit(0);
323 }
324
325 void ATTRIBUTE_NORETURN
die(void)326 die(void)
327 {
328 if (strace_tracer_pid == getpid()) {
329 cflag = 0;
330 cleanup();
331 exit(1);
332 }
333
334 _exit(1);
335 }
336
337 static void
error_opt_arg(int opt,const char * arg)338 error_opt_arg(int opt, const char *arg)
339 {
340 error_msg_and_help("invalid -%c argument: '%s'", opt, arg);
341 }
342
343 static const char *ptrace_attach_cmd;
344
345 static int
ptrace_attach_or_seize(int pid)346 ptrace_attach_or_seize(int pid)
347 {
348 int r;
349 if (!use_seize)
350 return ptrace_attach_cmd = "PTRACE_ATTACH",
351 ptrace(PTRACE_ATTACH, pid, 0L, 0L);
352 r = ptrace(PTRACE_SEIZE, pid, 0L, (unsigned long) ptrace_setoptions);
353 if (r)
354 return ptrace_attach_cmd = "PTRACE_SEIZE", r;
355 r = ptrace(PTRACE_INTERRUPT, pid, 0L, 0L);
356 return ptrace_attach_cmd = "PTRACE_INTERRUPT", r;
357 }
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(const unsigned int op,struct tcb * const tcp,unsigned int sig)367 ptrace_restart(const unsigned int op, struct tcb *const tcp, unsigned int sig)
368 {
369 int err;
370 const char *msg;
371
372 errno = 0;
373 ptrace(op, tcp->pid, 0L, (unsigned long) sig);
374 err = errno;
375 if (!err)
376 return 0;
377
378 switch (op) {
379 case PTRACE_CONT:
380 msg = "CONT";
381 break;
382 case PTRACE_DETACH:
383 msg = "DETACH";
384 break;
385 case PTRACE_LISTEN:
386 msg = "LISTEN";
387 break;
388 default:
389 msg = "SYSCALL";
390 }
391
392 /*
393 * Why curcol != 0? Otherwise sometimes we get this:
394 *
395 * 10252 kill(10253, SIGKILL) = 0
396 * <ptrace(SYSCALL,10252):No such process>10253 ...next decode...
397 *
398 * 10252 died after we retrieved syscall exit data,
399 * but before we tried to restart it. Log looks ugly.
400 */
401 if (current_tcp && current_tcp->curcol != 0) {
402 tprintf(" <ptrace(%s):%s>\n", msg, strerror(err));
403 line_ended();
404 }
405 if (err == ESRCH)
406 return 0;
407 errno = err;
408 perror_msg("ptrace(PTRACE_%s,pid:%d,sig:%u)", msg, tcp->pid, sig);
409 return -1;
410 }
411
412 static void
set_cloexec_flag(int fd)413 set_cloexec_flag(int fd)
414 {
415 int flags, newflags;
416
417 flags = fcntl(fd, F_GETFD);
418 if (flags < 0) {
419 /* Can happen only if fd is bad.
420 * Should never happen: if it does, we have a bug
421 * in the caller. Therefore we just abort
422 * instead of propagating the error.
423 */
424 perror_msg_and_die("fcntl(%d, F_GETFD)", fd);
425 }
426
427 newflags = flags | FD_CLOEXEC;
428 if (flags == newflags)
429 return;
430
431 if (fcntl(fd, F_SETFD, newflags)) /* never fails */
432 perror_msg_and_die("fcntl(%d, F_SETFD, %#x)", fd, newflags);
433 }
434
435 static void
kill_save_errno(pid_t pid,int sig)436 kill_save_errno(pid_t pid, int sig)
437 {
438 int saved_errno = errno;
439
440 (void) kill(pid, sig);
441 errno = saved_errno;
442 }
443
444 /*
445 * When strace is setuid executable, we have to swap uids
446 * before and after filesystem and process management operations.
447 */
448 static void
swap_uid(void)449 swap_uid(void)
450 {
451 int euid = geteuid(), uid = getuid();
452
453 if (euid != uid && setreuid(euid, uid) < 0) {
454 perror_msg_and_die("setreuid");
455 }
456 }
457
458 static FILE *
strace_fopen(const char * path)459 strace_fopen(const char *path)
460 {
461 FILE *fp;
462
463 swap_uid();
464 fp = fopen_stream(path, open_append ? "a" : "w");
465 if (!fp)
466 perror_msg_and_die("Can't fopen '%s'", path);
467 swap_uid();
468 set_cloexec_flag(fileno(fp));
469 return fp;
470 }
471
472 static int popen_pid;
473
474 #ifndef _PATH_BSHELL
475 # define _PATH_BSHELL "/bin/sh"
476 #endif
477
478 /*
479 * We cannot use standard popen(3) here because we have to distinguish
480 * popen child process from other processes we trace, and standard popen(3)
481 * does not export its child's pid.
482 */
483 static FILE *
strace_popen(const char * command)484 strace_popen(const char *command)
485 {
486 FILE *fp;
487 int pid;
488 int fds[2];
489
490 swap_uid();
491 if (pipe(fds) < 0)
492 perror_msg_and_die("pipe");
493
494 set_cloexec_flag(fds[1]); /* never fails */
495
496 pid = vfork();
497 if (pid < 0)
498 perror_msg_and_die("vfork");
499
500 if (pid == 0) {
501 /* child */
502 close(fds[1]);
503 if (fds[0] != 0) {
504 if (dup2(fds[0], 0))
505 perror_msg_and_die("dup2");
506 close(fds[0]);
507 }
508 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
509 perror_msg_and_die("Can't execute '%s'", _PATH_BSHELL);
510 }
511
512 /* parent */
513 popen_pid = pid;
514 close(fds[0]);
515 swap_uid();
516 fp = fdopen(fds[1], "w");
517 if (!fp)
518 perror_msg_and_die("fdopen");
519 return fp;
520 }
521
522 static void
outf_perror(const struct tcb * const tcp)523 outf_perror(const struct tcb * const tcp)
524 {
525 if (tcp->outf == stderr)
526 return;
527
528 /* This is ugly, but we don't store separate file names */
529 if (followfork >= 2)
530 perror_msg("%s.%u", outfname, tcp->pid);
531 else
532 perror_msg("%s", outfname);
533 }
534
535 ATTRIBUTE_FORMAT((printf, 1, 0))
536 static void
tvprintf(const char * const fmt,va_list args)537 tvprintf(const char *const fmt, va_list args)
538 {
539 if (current_tcp) {
540 int n = vfprintf(current_tcp->outf, fmt, args);
541 if (n < 0) {
542 /* very unlikely due to vfprintf buffering */
543 outf_perror(current_tcp);
544 } else
545 current_tcp->curcol += n;
546 }
547 }
548
549 void
tprintf(const char * fmt,...)550 tprintf(const char *fmt, ...)
551 {
552 va_list args;
553 va_start(args, fmt);
554 tvprintf(fmt, args);
555 va_end(args);
556 }
557
558 #ifndef HAVE_FPUTS_UNLOCKED
559 # define fputs_unlocked fputs
560 #endif
561
562 void
tprints(const char * str)563 tprints(const char *str)
564 {
565 if (current_tcp) {
566 int n = fputs_unlocked(str, current_tcp->outf);
567 if (n >= 0) {
568 current_tcp->curcol += strlen(str);
569 return;
570 }
571 /* very unlikely due to fputs_unlocked buffering */
572 outf_perror(current_tcp);
573 }
574 }
575
576 void
tprints_comment(const char * const str)577 tprints_comment(const char *const str)
578 {
579 if (str && *str)
580 tprintf(" /* %s */", str);
581 }
582
583 void
tprintf_comment(const char * fmt,...)584 tprintf_comment(const char *fmt, ...)
585 {
586 if (!fmt || !*fmt)
587 return;
588
589 va_list args;
590 va_start(args, fmt);
591 tprints(" /* ");
592 tvprintf(fmt, args);
593 tprints(" */");
594 va_end(args);
595 }
596
597 static void
flush_tcp_output(const struct tcb * const tcp)598 flush_tcp_output(const struct tcb *const tcp)
599 {
600 if (fflush(tcp->outf))
601 outf_perror(tcp);
602 }
603
604 void
line_ended(void)605 line_ended(void)
606 {
607 if (current_tcp) {
608 current_tcp->curcol = 0;
609 flush_tcp_output(current_tcp);
610 }
611 if (printing_tcp) {
612 printing_tcp->curcol = 0;
613 printing_tcp = NULL;
614 }
615 }
616
617 void
set_current_tcp(const struct tcb * tcp)618 set_current_tcp(const struct tcb *tcp)
619 {
620 current_tcp = (struct tcb *) tcp;
621
622 /* Sync current_personality and stuff */
623 if (current_tcp)
624 set_personality(current_tcp->currpers);
625 }
626
627 void
printleader(struct tcb * tcp)628 printleader(struct tcb *tcp)
629 {
630 /* If -ff, "previous tcb we printed" is always the same as current,
631 * because we have per-tcb output files.
632 */
633 if (followfork >= 2)
634 printing_tcp = tcp;
635
636 if (printing_tcp) {
637 set_current_tcp(printing_tcp);
638 if (printing_tcp->curcol != 0 && (followfork < 2 || printing_tcp == tcp)) {
639 /*
640 * case 1: we have a shared log (i.e. not -ff), and last line
641 * wasn't finished (same or different tcb, doesn't matter).
642 * case 2: split log, we are the same tcb, but our last line
643 * didn't finish ("SIGKILL nuked us after syscall entry" etc).
644 */
645 tprints(" <unfinished ...>\n");
646 printing_tcp->curcol = 0;
647 }
648 }
649
650 printing_tcp = tcp;
651 set_current_tcp(tcp);
652 current_tcp->curcol = 0;
653
654 if (print_pid_pfx)
655 tprintf("%-5d ", tcp->pid);
656 else if (nprocs > 1 && !outfname)
657 tprintf("[pid %5u] ", tcp->pid);
658
659 if (tflag) {
660 struct timespec ts;
661 clock_gettime(CLOCK_REALTIME, &ts);
662
663 if (tflag > 2) {
664 tprintf("%lld.%06ld ",
665 (long long) ts.tv_sec, (long) ts.tv_nsec / 1000);
666 } else {
667 time_t local = ts.tv_sec;
668 char str[MAX(sizeof("HH:MM:SS"), sizeof(ts.tv_sec) * 3)];
669 struct tm *tm = localtime(&local);
670
671 if (tm)
672 strftime(str, sizeof(str), "%T", tm);
673 else
674 xsprintf(str, "%lld", (long long) local);
675 if (tflag > 1)
676 tprintf("%s.%06ld ",
677 str, (long) ts.tv_nsec / 1000);
678 else
679 tprintf("%s ", str);
680 }
681 }
682
683 if (rflag) {
684 struct timespec ts;
685 clock_gettime(CLOCK_MONOTONIC, &ts);
686
687 static struct timespec ots;
688 if (ots.tv_sec == 0)
689 ots = ts;
690
691 struct timespec dts;
692 ts_sub(&dts, &ts, &ots);
693 ots = ts;
694
695 tprintf("%s%6ld.%06ld%s ",
696 tflag ? "(+" : "",
697 (long) dts.tv_sec, (long) dts.tv_nsec / 1000,
698 tflag ? ")" : "");
699 }
700
701 if (iflag)
702 print_pc(tcp);
703 }
704
705 void
tabto(void)706 tabto(void)
707 {
708 if (current_tcp->curcol < acolumn)
709 tprints(acolumn_spaces + current_tcp->curcol);
710 }
711
712 /* Should be only called directly *after successful attach* to a tracee.
713 * Otherwise, "strace -oFILE -ff -p<nonexistant_pid>"
714 * may create bogus empty FILE.<nonexistant_pid>, and then die.
715 */
716 static void
after_successful_attach(struct tcb * tcp,const unsigned int flags)717 after_successful_attach(struct tcb *tcp, const unsigned int flags)
718 {
719 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | flags;
720 tcp->outf = shared_log; /* if not -ff mode, the same file is for all */
721 if (followfork >= 2) {
722 char name[PATH_MAX];
723 xsprintf(name, "%s.%u", outfname, tcp->pid);
724 tcp->outf = strace_fopen(name);
725 }
726
727 #ifdef ENABLE_STACKTRACE
728 if (stack_trace_enabled)
729 unwind_tcb_init(tcp);
730 #endif
731 }
732
733 static void
expand_tcbtab(void)734 expand_tcbtab(void)
735 {
736 /* Allocate some (more) TCBs (and expand the table).
737 We don't want to relocate the TCBs because our
738 callers have pointers and it would be a pain.
739 So tcbtab is a table of pointers. Since we never
740 free the TCBs, we allocate a single chunk of many. */
741 size_t old_tcbtabsize;
742 struct tcb *newtcbs;
743 struct tcb **tcb_ptr;
744
745 old_tcbtabsize = tcbtabsize;
746
747 tcbtab = xgrowarray(tcbtab, &tcbtabsize, sizeof(tcbtab[0]));
748 newtcbs = xcalloc(tcbtabsize - old_tcbtabsize, sizeof(newtcbs[0]));
749
750 for (tcb_ptr = tcbtab + old_tcbtabsize;
751 tcb_ptr < tcbtab + tcbtabsize; tcb_ptr++, newtcbs++)
752 *tcb_ptr = newtcbs;
753 }
754
755 static struct tcb *
alloctcb(int pid)756 alloctcb(int pid)
757 {
758 unsigned int i;
759 struct tcb *tcp;
760
761 if (nprocs == tcbtabsize)
762 expand_tcbtab();
763
764 for (i = 0; i < tcbtabsize; i++) {
765 tcp = tcbtab[i];
766 if (!tcp->pid) {
767 memset(tcp, 0, sizeof(*tcp));
768 tcp->pid = pid;
769 #if SUPPORTED_PERSONALITIES > 1
770 tcp->currpers = current_personality;
771 #endif
772 nprocs++;
773 debug_msg("new tcb for pid %d, active tcbs:%d",
774 tcp->pid, nprocs);
775 return tcp;
776 }
777 }
778 error_msg_and_die("bug in alloctcb");
779 }
780
781 void *
get_tcb_priv_data(const struct tcb * tcp)782 get_tcb_priv_data(const struct tcb *tcp)
783 {
784 return tcp->_priv_data;
785 }
786
787 int
set_tcb_priv_data(struct tcb * tcp,void * const priv_data,void (* const free_priv_data)(void *))788 set_tcb_priv_data(struct tcb *tcp, void *const priv_data,
789 void (*const free_priv_data)(void *))
790 {
791 if (tcp->_priv_data)
792 return -1;
793
794 tcp->_free_priv_data = free_priv_data;
795 tcp->_priv_data = priv_data;
796
797 return 0;
798 }
799
800 void
free_tcb_priv_data(struct tcb * tcp)801 free_tcb_priv_data(struct tcb *tcp)
802 {
803 if (tcp->_priv_data) {
804 if (tcp->_free_priv_data) {
805 tcp->_free_priv_data(tcp->_priv_data);
806 tcp->_free_priv_data = NULL;
807 }
808 tcp->_priv_data = NULL;
809 }
810 }
811
812 static void
droptcb(struct tcb * tcp)813 droptcb(struct tcb *tcp)
814 {
815 if (tcp->pid == 0)
816 return;
817
818 int p;
819 for (p = 0; p < SUPPORTED_PERSONALITIES; ++p)
820 free(tcp->inject_vec[p]);
821
822 free_tcb_priv_data(tcp);
823
824 #ifdef ENABLE_STACKTRACE
825 if (stack_trace_enabled)
826 unwind_tcb_fin(tcp);
827 #endif
828
829 #ifdef HAVE_LINUX_KVM_H
830 kvm_vcpu_info_free(tcp);
831 #endif
832
833 if (tcp->mmap_cache)
834 tcp->mmap_cache->free_fn(tcp, __func__);
835
836 nprocs--;
837 debug_msg("dropped tcb for pid %d, %d remain", tcp->pid, nprocs);
838
839 if (tcp->outf) {
840 if (followfork >= 2) {
841 if (tcp->curcol != 0)
842 fprintf(tcp->outf, " <detached ...>\n");
843 fclose(tcp->outf);
844 } else {
845 if (printing_tcp == tcp && tcp->curcol != 0)
846 fprintf(tcp->outf, " <detached ...>\n");
847 flush_tcp_output(tcp);
848 }
849 }
850
851 if (current_tcp == tcp)
852 set_current_tcp(NULL);
853 if (printing_tcp == tcp)
854 printing_tcp = NULL;
855
856 memset(tcp, 0, sizeof(*tcp));
857 }
858
859 /* Detach traced process.
860 * Never call DETACH twice on the same process as both unattached and
861 * attached-unstopped processes give the same ESRCH. For unattached process we
862 * would SIGSTOP it and wait for its SIGSTOP notification forever.
863 */
864 static void
detach(struct tcb * tcp)865 detach(struct tcb *tcp)
866 {
867 int error;
868 int status;
869
870 /*
871 * Linux wrongly insists the child be stopped
872 * before detaching. Arghh. We go through hoops
873 * to make a clean break of things.
874 */
875
876 if (!(tcp->flags & TCB_ATTACHED))
877 goto drop;
878
879 /* We attached but possibly didn't see the expected SIGSTOP.
880 * We must catch exactly one as otherwise the detached process
881 * would be left stopped (process state T).
882 */
883 if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
884 goto wait_loop;
885
886 error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
887 if (!error) {
888 /* On a clear day, you can see forever. */
889 goto drop;
890 }
891 if (errno != ESRCH) {
892 /* Shouldn't happen. */
893 perror_func_msg("ptrace(PTRACE_DETACH,%u)", tcp->pid);
894 goto drop;
895 }
896 /* ESRCH: process is either not stopped or doesn't exist. */
897 if (my_tkill(tcp->pid, 0) < 0) {
898 if (errno != ESRCH)
899 /* Shouldn't happen. */
900 perror_func_msg("tkill(%u,0)", tcp->pid);
901 /* else: process doesn't exist. */
902 goto drop;
903 }
904 /* Process is not stopped, need to stop it. */
905 if (use_seize) {
906 /*
907 * With SEIZE, tracee can be in group-stop already.
908 * In this state sending it another SIGSTOP does nothing.
909 * Need to use INTERRUPT.
910 * Testcase: trying to ^C a "strace -p <stopped_process>".
911 */
912 error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
913 if (!error)
914 goto wait_loop;
915 if (errno != ESRCH)
916 perror_func_msg("ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
917 } else {
918 error = my_tkill(tcp->pid, SIGSTOP);
919 if (!error)
920 goto wait_loop;
921 if (errno != ESRCH)
922 perror_func_msg("tkill(%u,SIGSTOP)", tcp->pid);
923 }
924 /* Either process doesn't exist, or some weird error. */
925 goto drop;
926
927 wait_loop:
928 /* We end up here in three cases:
929 * 1. We sent PTRACE_INTERRUPT (use_seize case)
930 * 2. We sent SIGSTOP (!use_seize)
931 * 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
932 */
933 for (;;) {
934 unsigned int sig;
935 if (waitpid(tcp->pid, &status, __WALL) < 0) {
936 if (errno == EINTR)
937 continue;
938 /*
939 * if (errno == ECHILD) break;
940 * ^^^ WRONG! We expect this PID to exist,
941 * and want to emit a message otherwise:
942 */
943 perror_func_msg("waitpid(%u)", tcp->pid);
944 break;
945 }
946 if (!WIFSTOPPED(status)) {
947 /*
948 * Tracee exited or was killed by signal.
949 * We shouldn't normally reach this place:
950 * we don't want to consume exit status.
951 * Consider "strace -p PID" being ^C-ed:
952 * we want merely to detach from PID.
953 *
954 * However, we _can_ end up here if tracee
955 * was SIGKILLed.
956 */
957 break;
958 }
959 sig = WSTOPSIG(status);
960 debug_msg("detach wait: event:%d sig:%d",
961 (unsigned) status >> 16, sig);
962 if (use_seize) {
963 unsigned event = (unsigned)status >> 16;
964 if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
965 /*
966 * sig == SIGTRAP: PTRACE_INTERRUPT stop.
967 * sig == other: process was already stopped
968 * with this stopping sig (see tests/detach-stopped).
969 * Looks like re-injecting this sig is not necessary
970 * in DETACH for the tracee to remain stopped.
971 */
972 sig = 0;
973 }
974 /*
975 * PTRACE_INTERRUPT is not guaranteed to produce
976 * the above event if other ptrace-stop is pending.
977 * See tests/detach-sleeping testcase:
978 * strace got SIGINT while tracee is sleeping.
979 * We sent PTRACE_INTERRUPT.
980 * We see syscall exit, not PTRACE_INTERRUPT stop.
981 * We won't get PTRACE_INTERRUPT stop
982 * if we would CONT now. Need to DETACH.
983 */
984 if (sig == syscall_trap_sig)
985 sig = 0;
986 /* else: not sure in which case we can be here.
987 * Signal stop? Inject it while detaching.
988 */
989 ptrace_restart(PTRACE_DETACH, tcp, sig);
990 break;
991 }
992 /* Note: this check has to be after use_seize check */
993 /* (else, in use_seize case SIGSTOP will be mistreated) */
994 if (sig == SIGSTOP) {
995 /* Detach, suppressing SIGSTOP */
996 ptrace_restart(PTRACE_DETACH, tcp, 0);
997 break;
998 }
999 if (sig == syscall_trap_sig)
1000 sig = 0;
1001 /* Can't detach just yet, may need to wait for SIGSTOP */
1002 error = ptrace_restart(PTRACE_CONT, tcp, sig);
1003 if (error < 0) {
1004 /* Should not happen.
1005 * Note: ptrace_restart returns 0 on ESRCH, so it's not it.
1006 * ptrace_restart already emitted error message.
1007 */
1008 break;
1009 }
1010 }
1011
1012 drop:
1013 if (!qflag && (tcp->flags & TCB_ATTACHED))
1014 error_msg("Process %u detached", tcp->pid);
1015
1016 droptcb(tcp);
1017 }
1018
1019 static void
process_opt_p_list(char * opt)1020 process_opt_p_list(char *opt)
1021 {
1022 while (*opt) {
1023 /*
1024 * We accept -p PID,PID; -p "`pidof PROG`"; -p "`pgrep PROG`".
1025 * pidof uses space as delim, pgrep uses newline. :(
1026 */
1027 int pid;
1028 char *delim = opt + strcspn(opt, "\n\t ,");
1029 char c = *delim;
1030
1031 *delim = '\0';
1032 pid = string_to_uint(opt);
1033 if (pid <= 0) {
1034 error_msg_and_die("Invalid process id: '%s'", opt);
1035 }
1036 if (pid == strace_tracer_pid) {
1037 error_msg_and_die("I'm sorry, I can't let you do that, Dave.");
1038 }
1039 *delim = c;
1040 alloctcb(pid);
1041 if (c == '\0')
1042 break;
1043 opt = delim + 1;
1044 }
1045 }
1046
1047 static void
attach_tcb(struct tcb * const tcp)1048 attach_tcb(struct tcb *const tcp)
1049 {
1050 if (ptrace_attach_or_seize(tcp->pid) < 0) {
1051 perror_msg("attach: ptrace(%s, %d)",
1052 ptrace_attach_cmd, tcp->pid);
1053 droptcb(tcp);
1054 return;
1055 }
1056
1057 after_successful_attach(tcp, TCB_GRABBED | post_attach_sigstop);
1058 debug_msg("attach to pid %d (main) succeeded", tcp->pid);
1059
1060 static const char task_path[] = "/proc/%d/task";
1061 char procdir[sizeof(task_path) + sizeof(int) * 3];
1062 DIR *dir;
1063 unsigned int ntid = 0, nerr = 0;
1064
1065 if (followfork && tcp->pid != strace_child &&
1066 xsprintf(procdir, task_path, tcp->pid) > 0 &&
1067 (dir = opendir(procdir)) != NULL) {
1068 struct_dirent *de;
1069
1070 while ((de = read_dir(dir)) != NULL) {
1071 if (de->d_fileno == 0)
1072 continue;
1073
1074 int tid = string_to_uint(de->d_name);
1075 if (tid <= 0 || tid == tcp->pid)
1076 continue;
1077
1078 ++ntid;
1079 if (ptrace_attach_or_seize(tid) < 0) {
1080 ++nerr;
1081 debug_perror_msg("attach: ptrace(%s, %d)",
1082 ptrace_attach_cmd, tid);
1083 continue;
1084 }
1085
1086 after_successful_attach(alloctcb(tid),
1087 TCB_GRABBED | post_attach_sigstop);
1088 debug_msg("attach to pid %d succeeded", tid);
1089 }
1090
1091 closedir(dir);
1092 }
1093
1094 if (!qflag) {
1095 if (ntid > nerr)
1096 error_msg("Process %u attached"
1097 " with %u threads",
1098 tcp->pid, ntid - nerr + 1);
1099 else
1100 error_msg("Process %u attached",
1101 tcp->pid);
1102 }
1103 }
1104
1105 static void
startup_attach(void)1106 startup_attach(void)
1107 {
1108 pid_t parent_pid = strace_tracer_pid;
1109 unsigned int tcbi;
1110 struct tcb *tcp;
1111
1112 if (daemonized_tracer) {
1113 pid_t pid = fork();
1114 if (pid < 0)
1115 perror_func_msg_and_die("fork");
1116
1117 if (pid) { /* parent */
1118 /*
1119 * Wait for grandchild to attach to straced process
1120 * (grandparent). Grandchild SIGKILLs us after it attached.
1121 * Grandparent's wait() is unblocked by our death,
1122 * it proceeds to exec the straced program.
1123 */
1124 pause();
1125 _exit(0); /* paranoia */
1126 }
1127 /* grandchild */
1128 /* We will be the tracer process. Remember our new pid: */
1129 strace_tracer_pid = getpid();
1130 }
1131
1132 for (tcbi = 0; tcbi < tcbtabsize; tcbi++) {
1133 tcp = tcbtab[tcbi];
1134
1135 if (!tcp->pid)
1136 continue;
1137
1138 /* Is this a process we should attach to, but not yet attached? */
1139 if (tcp->flags & TCB_ATTACHED)
1140 continue; /* no, we already attached it */
1141
1142 if (tcp->pid == parent_pid || tcp->pid == strace_tracer_pid) {
1143 errno = EPERM;
1144 perror_msg("attach: pid %d", tcp->pid);
1145 droptcb(tcp);
1146 continue;
1147 }
1148
1149 attach_tcb(tcp);
1150
1151 if (interrupted)
1152 return;
1153 } /* for each tcbtab[] */
1154
1155 if (daemonized_tracer) {
1156 /*
1157 * Make parent go away.
1158 * Also makes grandparent's wait() unblock.
1159 */
1160 kill(parent_pid, SIGKILL);
1161 strace_child = 0;
1162 }
1163 }
1164
1165 /* Stack-o-phobic exec helper, in the hope to work around
1166 * NOMMU + "daemonized tracer" difficulty.
1167 */
1168 struct exec_params {
1169 int fd_to_close;
1170 uid_t run_euid;
1171 gid_t run_egid;
1172 char **argv;
1173 char *pathname;
1174 struct sigaction child_sa;
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 } else if (geteuid() != 0)
1206 if (setreuid(run_uid, run_uid) < 0) {
1207 perror_msg_and_die("setreuid");
1208 }
1209
1210 if (!daemonized_tracer) {
1211 /*
1212 * Induce a ptrace stop. Tracer (our parent)
1213 * will resume us with PTRACE_SYSCALL and display
1214 * the immediately following execve syscall.
1215 * Can't do this on NOMMU systems, we are after
1216 * vfork: parent is blocked, stopping would deadlock.
1217 */
1218 if (!NOMMU_SYSTEM)
1219 kill(getpid(), SIGSTOP);
1220 } else {
1221 alarm(3);
1222 /* we depend on SIGCHLD set to SIG_DFL by init code */
1223 /* if it happens to be SIG_IGN'ed, wait won't block */
1224 wait(NULL);
1225 alarm(0);
1226 }
1227
1228 if (params_for_tracee.child_sa.sa_handler != SIG_DFL)
1229 sigaction(SIGCHLD, ¶ms_for_tracee.child_sa, NULL);
1230
1231 execv(params->pathname, params->argv);
1232 perror_msg_and_die("exec");
1233 }
1234
1235 /*
1236 * Open a dummy descriptor for use as a placeholder.
1237 * The descriptor is O_RDONLY with FD_CLOEXEC flag set.
1238 * A read attempt from such descriptor ends with EOF,
1239 * a write attempt is rejected with EBADF.
1240 */
1241 static int
open_dummy_desc(void)1242 open_dummy_desc(void)
1243 {
1244 int fds[2];
1245
1246 if (pipe(fds))
1247 perror_func_msg_and_die("pipe");
1248 close(fds[1]);
1249 set_cloexec_flag(fds[0]);
1250 return fds[0];
1251 }
1252
1253 /* placeholder fds status for stdin and stdout */
1254 static bool fd_is_placeholder[2];
1255
1256 /*
1257 * Ensure that all standard file descriptors are open by opening placeholder
1258 * file descriptors for those standard file descriptors that are not open.
1259 *
1260 * The information which descriptors have been made open is saved
1261 * in fd_is_placeholder for later use.
1262 */
1263 static void
ensure_standard_fds_opened(void)1264 ensure_standard_fds_opened(void)
1265 {
1266 int fd;
1267
1268 while ((fd = open_dummy_desc()) <= 2) {
1269 if (fd == 2)
1270 break;
1271 fd_is_placeholder[fd] = true;
1272 }
1273
1274 if (fd > 2)
1275 close(fd);
1276 }
1277
1278 /*
1279 * Redirect stdin and stdout unless they have been opened earlier
1280 * by ensure_standard_fds_opened as placeholders.
1281 */
1282 static void
redirect_standard_fds(void)1283 redirect_standard_fds(void)
1284 {
1285 int i;
1286
1287 /*
1288 * It might be a good idea to redirect stderr as well,
1289 * but we sometimes need to print error messages.
1290 */
1291 for (i = 0; i <= 1; ++i) {
1292 if (!fd_is_placeholder[i]) {
1293 close(i);
1294 open_dummy_desc();
1295 }
1296 }
1297 }
1298
1299 static void
startup_child(char ** argv)1300 startup_child(char **argv)
1301 {
1302 struct_stat statbuf;
1303 const char *filename;
1304 size_t filename_len;
1305 char pathname[PATH_MAX];
1306 int pid;
1307 struct tcb *tcp;
1308
1309 filename = argv[0];
1310 filename_len = strlen(filename);
1311
1312 if (filename_len > sizeof(pathname) - 1) {
1313 errno = ENAMETOOLONG;
1314 perror_msg_and_die("exec");
1315 }
1316 if (strchr(filename, '/')) {
1317 strcpy(pathname, filename);
1318 }
1319 #ifdef USE_DEBUGGING_EXEC
1320 /*
1321 * Debuggers customarily check the current directory
1322 * first regardless of the path but doing that gives
1323 * security geeks a panic attack.
1324 */
1325 else if (stat_file(filename, &statbuf) == 0)
1326 strcpy(pathname, filename);
1327 #endif /* USE_DEBUGGING_EXEC */
1328 else {
1329 const char *path;
1330 size_t m, n, len;
1331
1332 for (path = getenv("PATH"); path && *path; path += m) {
1333 const char *colon = strchr(path, ':');
1334 if (colon) {
1335 n = colon - path;
1336 m = n + 1;
1337 } else
1338 m = n = strlen(path);
1339 if (n == 0) {
1340 if (!getcwd(pathname, PATH_MAX))
1341 continue;
1342 len = strlen(pathname);
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_func_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 after_successful_attach(tcp, TCB_SKIP_DETACH_ON_FIRST_EXEC
1434 | (NOMMU_SYSTEM ? 0
1435 : (TCB_HIDE_LOG
1436 | post_attach_sigstop)));
1437 } else {
1438 /* With -D, we are *child* here, the tracee is our parent. */
1439 strace_child = strace_tracer_pid;
1440 strace_tracer_pid = getpid();
1441 tcp = alloctcb(strace_child);
1442 tcp->flags |= TCB_SKIP_DETACH_ON_FIRST_EXEC | TCB_HIDE_LOG;
1443 /*
1444 * Attaching will be done later, by startup_attach.
1445 * Note: we don't do after_successful_attach() here either!
1446 */
1447
1448 /* NOMMU BUG! -D mode is active, we (child) return,
1449 * and we will scribble over parent's stack!
1450 * When parent later unpauses, it segfaults.
1451 *
1452 * We work around it
1453 * (1) by declaring exec_or_die() NORETURN,
1454 * hopefully compiler will just jump to it
1455 * instead of call (won't push anything to stack),
1456 * (2) by trying very hard in exec_or_die()
1457 * to not use any stack,
1458 * (3) having a really big (PATH_MAX) stack object
1459 * in this function, which creates a "buffer" between
1460 * child's and parent's stack pointers.
1461 * This may save us if (1) and (2) failed
1462 * and compiler decided to use stack in exec_or_die() anyway
1463 * (happens on i386 because of stack parameter passing).
1464 *
1465 * A cleaner solution is to use makecontext + setcontext
1466 * to create a genuine separate stack and execute on it.
1467 */
1468 }
1469 /*
1470 * A case where straced process is part of a pipe:
1471 * { sleep 1; yes | head -n99999; } | strace -o/dev/null sh -c 'exec <&-; sleep 9'
1472 * If strace won't close its fd#0, closing it in tracee is not enough:
1473 * the pipe is still open, it has a reader. Thus, "head" will not get its
1474 * SIGPIPE at once, on the first write.
1475 *
1476 * Preventing it by redirecting strace's stdin/out.
1477 * (Don't leave fds 0 and 1 closed, this is bad practice: future opens
1478 * will reuse them, unexpectedly making a newly opened object "stdin").
1479 */
1480 redirect_standard_fds();
1481 }
1482
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_func_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 {
1510 debug_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_func_msg_and_die("unexpected wait result %d",
1524 tracee_pid);
1525 }
1526 if (WIFSIGNALED(status))
1527 return;
1528
1529 error_func_msg_and_die("unexpected wait status %#x", status);
1530 }
1531 }
1532
1533 static unsigned
get_os_release(void)1534 get_os_release(void)
1535 {
1536 unsigned rel;
1537 const char *p;
1538 struct utsname u;
1539 if (uname(&u) < 0)
1540 perror_msg_and_die("uname");
1541 /* u.release has this form: "3.2.9[-some-garbage]" */
1542 rel = 0;
1543 p = u.release;
1544 for (;;) {
1545 if (!(*p >= '0' && *p <= '9'))
1546 error_msg_and_die("Bad OS release string: '%s'", u.release);
1547 /* Note: this open-codes KERNEL_VERSION(): */
1548 rel = (rel << 8) | atoi(p);
1549 if (rel >= KERNEL_VERSION(1, 0, 0))
1550 break;
1551 while (*p >= '0' && *p <= '9')
1552 p++;
1553 if (*p != '.') {
1554 if (rel >= KERNEL_VERSION(0, 1, 0)) {
1555 /* "X.Y-something" means "X.Y.0" */
1556 rel <<= 8;
1557 break;
1558 }
1559 error_msg_and_die("Bad OS release string: '%s'", u.release);
1560 }
1561 p++;
1562 }
1563 return rel;
1564 }
1565
1566 static void
set_sighandler(int signo,void (* sighandler)(int),struct sigaction * oldact)1567 set_sighandler(int signo, void (*sighandler)(int), struct sigaction *oldact)
1568 {
1569 const struct sigaction sa = { .sa_handler = sighandler };
1570 sigaction(signo, &sa, oldact);
1571 }
1572
1573 /*
1574 * Initialization part of main() was eating much stack (~0.5k),
1575 * which was unused after init.
1576 * We can reuse it if we move init code into a separate function.
1577 *
1578 * Don't want main() to inline us and defeat the reason
1579 * we have a separate function.
1580 */
1581 static void ATTRIBUTE_NOINLINE
init(int argc,char * argv[])1582 init(int argc, char *argv[])
1583 {
1584 int c, i;
1585 int optF = 0;
1586
1587 if (!program_invocation_name || !*program_invocation_name) {
1588 static char name[] = "strace";
1589 program_invocation_name =
1590 (argc > 0 && argv[0] && *argv[0]) ? argv[0] : name;
1591 }
1592
1593 strace_tracer_pid = getpid();
1594
1595 os_release = get_os_release();
1596
1597 shared_log = stderr;
1598 set_sortby(DEFAULT_SORTBY);
1599 set_personality(DEFAULT_PERSONALITY);
1600 qualify("trace=all");
1601 qualify("abbrev=all");
1602 qualify("verbose=all");
1603 #if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
1604 # error Bug in DEFAULT_QUAL_FLAGS
1605 #endif
1606 qualify("signal=all");
1607 while ((c = getopt(argc, argv, "+"
1608 #ifdef ENABLE_STACKTRACE
1609 "k"
1610 #endif
1611 "a:Ab:cCdDe:E:fFhiI:o:O:p:P:qrs:S:tTu:vVwxX:yz")) != EOF) {
1612 switch (c) {
1613 case 'a':
1614 acolumn = string_to_uint(optarg);
1615 if (acolumn < 0)
1616 error_opt_arg(c, optarg);
1617 break;
1618 case 'A':
1619 open_append = true;
1620 break;
1621 case 'b':
1622 if (strcmp(optarg, "execve") != 0)
1623 error_msg_and_die("Syscall '%s' for -b isn't supported",
1624 optarg);
1625 detach_on_execve = 1;
1626 break;
1627 case 'c':
1628 if (cflag == CFLAG_BOTH) {
1629 error_msg_and_help("-c and -C are mutually exclusive");
1630 }
1631 cflag = CFLAG_ONLY_STATS;
1632 break;
1633 case 'C':
1634 if (cflag == CFLAG_ONLY_STATS) {
1635 error_msg_and_help("-c and -C are mutually exclusive");
1636 }
1637 cflag = CFLAG_BOTH;
1638 break;
1639 case 'd':
1640 debug_flag = 1;
1641 break;
1642 case 'D':
1643 daemonized_tracer = 1;
1644 break;
1645 case 'e':
1646 qualify(optarg);
1647 break;
1648 case 'E':
1649 if (putenv(optarg) < 0)
1650 perror_msg_and_die("putenv");
1651 break;
1652 case 'f':
1653 followfork++;
1654 break;
1655 case 'F':
1656 optF = 1;
1657 break;
1658 case 'h':
1659 usage();
1660 break;
1661 case 'i':
1662 iflag = 1;
1663 break;
1664 case 'I':
1665 opt_intr = string_to_uint_upto(optarg, NUM_INTR_OPTS - 1);
1666 if (opt_intr <= 0)
1667 error_opt_arg(c, optarg);
1668 break;
1669 #ifdef ENABLE_STACKTRACE
1670 case 'k':
1671 stack_trace_enabled = true;
1672 break;
1673 #endif
1674 case 'o':
1675 outfname = optarg;
1676 break;
1677 case 'O':
1678 i = string_to_uint(optarg);
1679 if (i < 0)
1680 error_opt_arg(c, optarg);
1681 set_overhead(i);
1682 break;
1683 case 'p':
1684 process_opt_p_list(optarg);
1685 break;
1686 case 'P':
1687 pathtrace_select(optarg);
1688 break;
1689 case 'q':
1690 qflag++;
1691 break;
1692 case 'r':
1693 rflag = 1;
1694 break;
1695 case 's':
1696 i = string_to_uint(optarg);
1697 if (i < 0 || (unsigned int) i > -1U / 4)
1698 error_opt_arg(c, optarg);
1699 max_strlen = i;
1700 break;
1701 case 'S':
1702 set_sortby(optarg);
1703 break;
1704 case 't':
1705 tflag++;
1706 break;
1707 case 'T':
1708 Tflag = 1;
1709 break;
1710 case 'u':
1711 username = optarg;
1712 break;
1713 case 'v':
1714 qualify("abbrev=none");
1715 break;
1716 case 'V':
1717 print_version();
1718 exit(0);
1719 break;
1720 case 'w':
1721 count_wallclock = 1;
1722 break;
1723 case 'x':
1724 xflag++;
1725 break;
1726 case 'X':
1727 if (!strcmp(optarg, "raw"))
1728 xlat_verbosity = XLAT_STYLE_RAW;
1729 else if (!strcmp(optarg, "abbrev"))
1730 xlat_verbosity = XLAT_STYLE_ABBREV;
1731 else if (!strcmp(optarg, "verbose"))
1732 xlat_verbosity = XLAT_STYLE_VERBOSE;
1733 else
1734 error_opt_arg(c, optarg);
1735 break;
1736 case 'y':
1737 show_fd_path++;
1738 break;
1739 case 'z':
1740 not_failing_only = 1;
1741 break;
1742 default:
1743 error_msg_and_help(NULL);
1744 break;
1745 }
1746 }
1747
1748 argv += optind;
1749 argc -= optind;
1750
1751 if (argc < 0 || (!nprocs && !argc)) {
1752 error_msg_and_help("must have PROG [ARGS] or -p PID");
1753 }
1754
1755 if (!argc && daemonized_tracer) {
1756 error_msg_and_help("PROG [ARGS] must be specified with -D");
1757 }
1758
1759 if (optF) {
1760 if (followfork) {
1761 error_msg("deprecated option -F ignored");
1762 } else {
1763 error_msg("option -F is deprecated, "
1764 "please use -f instead");
1765 followfork = optF;
1766 }
1767 }
1768
1769 if (followfork >= 2 && cflag) {
1770 error_msg_and_help("(-c or -C) and -ff are mutually exclusive");
1771 }
1772
1773 if (count_wallclock && !cflag) {
1774 error_msg_and_help("-w must be given with (-c or -C)");
1775 }
1776
1777 if (cflag == CFLAG_ONLY_STATS) {
1778 if (iflag)
1779 error_msg("-%c has no effect with -c", 'i');
1780 #ifdef ENABLE_STACKTRACE
1781 if (stack_trace_enabled)
1782 error_msg("-%c has no effect with -c", 'k');
1783 #endif
1784 if (rflag)
1785 error_msg("-%c has no effect with -c", 'r');
1786 if (tflag)
1787 error_msg("-%c has no effect with -c", 't');
1788 if (Tflag)
1789 error_msg("-%c has no effect with -c", 'T');
1790 if (show_fd_path)
1791 error_msg("-%c has no effect with -c", 'y');
1792 }
1793
1794 acolumn_spaces = xmalloc(acolumn + 1);
1795 memset(acolumn_spaces, ' ', acolumn);
1796 acolumn_spaces[acolumn] = '\0';
1797
1798 set_sighandler(SIGCHLD, SIG_DFL, ¶ms_for_tracee.child_sa);
1799
1800 #ifdef ENABLE_STACKTRACE
1801 if (stack_trace_enabled)
1802 unwind_init();
1803 #endif
1804
1805 /* See if they want to run as another user. */
1806 if (username != NULL) {
1807 struct passwd *pent;
1808
1809 if (getuid() != 0 || geteuid() != 0) {
1810 error_msg_and_die("You must be root to use the -u option");
1811 }
1812 pent = getpwnam(username);
1813 if (pent == NULL) {
1814 error_msg_and_die("Cannot find user '%s'", username);
1815 }
1816 run_uid = pent->pw_uid;
1817 run_gid = pent->pw_gid;
1818 } else {
1819 run_uid = getuid();
1820 run_gid = getgid();
1821 }
1822
1823 if (followfork)
1824 ptrace_setoptions |= PTRACE_O_TRACECLONE |
1825 PTRACE_O_TRACEFORK |
1826 PTRACE_O_TRACEVFORK;
1827 debug_msg("ptrace_setoptions = %#x", ptrace_setoptions);
1828 test_ptrace_seize();
1829
1830 /*
1831 * Is something weird with our stdin and/or stdout -
1832 * for example, may they be not open? In this case,
1833 * ensure that none of the future opens uses them.
1834 *
1835 * This was seen in the wild when /proc/sys/kernel/core_pattern
1836 * was set to "|/bin/strace -o/tmp/LOG PROG":
1837 * kernel runs coredump helper with fd#0 open but fd#1 closed (!),
1838 * therefore LOG gets opened to fd#1, and fd#1 is closed by
1839 * "don't hold up stdin/out open" code soon after.
1840 */
1841 ensure_standard_fds_opened();
1842
1843 /* Check if they want to redirect the output. */
1844 if (outfname) {
1845 /* See if they want to pipe the output. */
1846 if (outfname[0] == '|' || outfname[0] == '!') {
1847 /*
1848 * We can't do the <outfname>.PID funny business
1849 * when using popen, so prohibit it.
1850 */
1851 if (followfork >= 2)
1852 error_msg_and_help("piping the output and -ff "
1853 "are mutually exclusive");
1854 shared_log = strace_popen(outfname + 1);
1855 } else if (followfork < 2) {
1856 shared_log = strace_fopen(outfname);
1857 } else if (strlen(outfname) >= PATH_MAX - sizeof(int) * 3) {
1858 errno = ENAMETOOLONG;
1859 perror_msg_and_die("%s", outfname);
1860 }
1861 } else {
1862 /* -ff without -o FILE is the same as single -f */
1863 if (followfork >= 2)
1864 followfork = 1;
1865 }
1866
1867 if (!outfname || outfname[0] == '|' || outfname[0] == '!') {
1868 setvbuf(shared_log, NULL, _IOLBF, 0);
1869 }
1870
1871 /*
1872 * argv[0] -pPID -oFILE Default interactive setting
1873 * yes * 0 INTR_WHILE_WAIT
1874 * no 1 0 INTR_WHILE_WAIT
1875 * yes * 1 INTR_NEVER
1876 * no 1 1 INTR_WHILE_WAIT
1877 */
1878
1879 if (outfname && argc) {
1880 if (!opt_intr)
1881 opt_intr = INTR_NEVER;
1882 if (!qflag)
1883 qflag = 1;
1884 }
1885 if (!opt_intr)
1886 opt_intr = INTR_WHILE_WAIT;
1887
1888 /*
1889 * startup_child() must be called before the signal handlers get
1890 * installed below as they are inherited into the spawned process.
1891 * Also we do not need to be protected by them as during interruption
1892 * in the startup_child() mode we kill the spawned process anyway.
1893 */
1894 if (argc) {
1895 startup_child(argv);
1896 }
1897
1898 set_sighandler(SIGTTOU, SIG_IGN, NULL);
1899 set_sighandler(SIGTTIN, SIG_IGN, NULL);
1900 if (opt_intr != INTR_ANYWHERE) {
1901 if (opt_intr == INTR_BLOCK_TSTP_TOO)
1902 set_sighandler(SIGTSTP, SIG_IGN, NULL);
1903 /*
1904 * In interactive mode (if no -o OUTFILE, or -p PID is used),
1905 * fatal signals are handled asynchronously and acted
1906 * when waiting for process state changes.
1907 * In non-interactive mode these signals are ignored.
1908 */
1909 set_sighandler(SIGHUP, interactive ? interrupt : SIG_IGN, NULL);
1910 set_sighandler(SIGINT, interactive ? interrupt : SIG_IGN, NULL);
1911 set_sighandler(SIGQUIT, interactive ? interrupt : SIG_IGN, NULL);
1912 set_sighandler(SIGPIPE, interactive ? interrupt : SIG_IGN, NULL);
1913 set_sighandler(SIGTERM, interactive ? interrupt : SIG_IGN, NULL);
1914 }
1915
1916 sigemptyset(&timer_set);
1917 sigaddset(&timer_set, SIGALRM);
1918 sigprocmask(SIG_BLOCK, &timer_set, NULL);
1919 set_sighandler(SIGALRM, timer_sighandler, NULL);
1920
1921 if (nprocs != 0 || daemonized_tracer)
1922 startup_attach();
1923
1924 /* Do we want pids printed in our -o OUTFILE?
1925 * -ff: no (every pid has its own file); or
1926 * -f: yes (there can be more pids in the future); or
1927 * -p PID1,PID2: yes (there are already more than one pid)
1928 */
1929 print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
1930 }
1931
1932 static struct tcb *
pid2tcb(const int pid)1933 pid2tcb(const int pid)
1934 {
1935 if (pid <= 0)
1936 return NULL;
1937
1938 #define PID2TCB_CACHE_SIZE 1024U
1939 #define PID2TCB_CACHE_MASK (PID2TCB_CACHE_SIZE - 1)
1940
1941 static struct tcb *pid2tcb_cache[PID2TCB_CACHE_SIZE];
1942 struct tcb **const ptcp = &pid2tcb_cache[pid & PID2TCB_CACHE_MASK];
1943 struct tcb *tcp = *ptcp;
1944
1945 if (tcp && tcp->pid == pid)
1946 return tcp;
1947
1948 for (unsigned int i = 0; i < tcbtabsize; ++i) {
1949 tcp = tcbtab[i];
1950 if (tcp->pid == pid)
1951 return *ptcp = tcp;
1952 }
1953
1954 return NULL;
1955 }
1956
1957 static void
cleanup(void)1958 cleanup(void)
1959 {
1960 unsigned int i;
1961 struct tcb *tcp;
1962 int fatal_sig;
1963
1964 /* 'interrupted' is a volatile object, fetch it only once */
1965 fatal_sig = interrupted;
1966 if (!fatal_sig)
1967 fatal_sig = SIGTERM;
1968
1969 for (i = 0; i < tcbtabsize; i++) {
1970 tcp = tcbtab[i];
1971 if (!tcp->pid)
1972 continue;
1973 debug_func_msg("looking at pid %u", tcp->pid);
1974 if (tcp->pid == strace_child) {
1975 kill(tcp->pid, SIGCONT);
1976 kill(tcp->pid, fatal_sig);
1977 }
1978 detach(tcp);
1979 }
1980 if (cflag)
1981 call_summary(shared_log);
1982 }
1983
1984 static void
interrupt(int sig)1985 interrupt(int sig)
1986 {
1987 interrupted = sig;
1988 }
1989
1990 static void
print_debug_info(const int pid,int status)1991 print_debug_info(const int pid, int status)
1992 {
1993 const unsigned int event = (unsigned int) status >> 16;
1994 char buf[sizeof("WIFEXITED,exitcode=%u") + sizeof(int)*3 /*paranoia:*/ + 16];
1995 char evbuf[sizeof(",EVENT_VFORK_DONE (%u)") + sizeof(int)*3 /*paranoia:*/ + 16];
1996
1997 strcpy(buf, "???");
1998 if (WIFSIGNALED(status))
1999 #ifdef WCOREDUMP
2000 xsprintf(buf, "WIFSIGNALED,%ssig=%s",
2001 WCOREDUMP(status) ? "core," : "",
2002 signame(WTERMSIG(status)));
2003 #else
2004 xsprintf(buf, "WIFSIGNALED,sig=%s",
2005 signame(WTERMSIG(status)));
2006 #endif
2007 if (WIFEXITED(status))
2008 xsprintf(buf, "WIFEXITED,exitcode=%u", WEXITSTATUS(status));
2009 if (WIFSTOPPED(status))
2010 xsprintf(buf, "WIFSTOPPED,sig=%s", signame(WSTOPSIG(status)));
2011 evbuf[0] = '\0';
2012 if (event != 0) {
2013 static const char *const event_names[] = {
2014 [PTRACE_EVENT_CLONE] = "CLONE",
2015 [PTRACE_EVENT_FORK] = "FORK",
2016 [PTRACE_EVENT_VFORK] = "VFORK",
2017 [PTRACE_EVENT_VFORK_DONE] = "VFORK_DONE",
2018 [PTRACE_EVENT_EXEC] = "EXEC",
2019 [PTRACE_EVENT_EXIT] = "EXIT",
2020 /* [PTRACE_EVENT_STOP (=128)] would make biggish array */
2021 };
2022 const char *e = "??";
2023 if (event < ARRAY_SIZE(event_names))
2024 e = event_names[event];
2025 else if (event == PTRACE_EVENT_STOP)
2026 e = "STOP";
2027 xsprintf(evbuf, ",EVENT_%s (%u)", e, event);
2028 }
2029 error_msg("[wait(0x%06x) = %u] %s%s", status, pid, buf, evbuf);
2030 }
2031
2032 static struct tcb *
maybe_allocate_tcb(const int pid,int status)2033 maybe_allocate_tcb(const int pid, int status)
2034 {
2035 if (!WIFSTOPPED(status)) {
2036 if (detach_on_execve && pid == strace_child) {
2037 /* example: strace -bexecve sh -c 'exec true' */
2038 strace_child = 0;
2039 return NULL;
2040 }
2041 /*
2042 * This can happen if we inherited an unknown child.
2043 * Example: (sleep 1 & exec strace true)
2044 */
2045 error_msg("Exit of unknown pid %u ignored", pid);
2046 return NULL;
2047 }
2048 if (followfork) {
2049 /* We assume it's a fork/vfork/clone child */
2050 struct tcb *tcp = alloctcb(pid);
2051 after_successful_attach(tcp, post_attach_sigstop);
2052 if (!qflag)
2053 error_msg("Process %d attached", pid);
2054 return tcp;
2055 } else {
2056 /*
2057 * This can happen if a clone call misused CLONE_PTRACE itself.
2058 *
2059 * There used to be a dance around possible re-injection of
2060 * WSTOPSIG(status), but it was later removed as the only
2061 * observable stop here is the initial ptrace-stop.
2062 */
2063 ptrace(PTRACE_DETACH, pid, NULL, 0L);
2064 error_msg("Detached unknown pid %d", pid);
2065 return NULL;
2066 }
2067 }
2068
2069 static struct tcb *
maybe_switch_tcbs(struct tcb * tcp,const int pid)2070 maybe_switch_tcbs(struct tcb *tcp, const int pid)
2071 {
2072 FILE *fp;
2073 struct tcb *execve_thread;
2074 long old_pid = 0;
2075
2076 if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, &old_pid) < 0)
2077 return tcp;
2078 /* Avoid truncation in pid2tcb() param passing */
2079 if (old_pid <= 0 || old_pid == pid)
2080 return tcp;
2081 if ((unsigned long) old_pid > UINT_MAX)
2082 return tcp;
2083 execve_thread = pid2tcb(old_pid);
2084 /* It should be !NULL, but I feel paranoid */
2085 if (!execve_thread)
2086 return tcp;
2087
2088 if (execve_thread->curcol != 0) {
2089 /*
2090 * One case we are here is -ff:
2091 * try "strace -oLOG -ff test/threaded_execve"
2092 */
2093 fprintf(execve_thread->outf, " <pid changed to %d ...>\n", pid);
2094 /*execve_thread->curcol = 0; - no need, see code below */
2095 }
2096 /* Swap output FILEs (needed for -ff) */
2097 fp = execve_thread->outf;
2098 execve_thread->outf = tcp->outf;
2099 tcp->outf = fp;
2100 /* And their column positions */
2101 execve_thread->curcol = tcp->curcol;
2102 tcp->curcol = 0;
2103 /* Drop leader, but close execve'd thread outfile (if -ff) */
2104 droptcb(tcp);
2105 /* Switch to the thread, reusing leader's outfile and pid */
2106 tcp = execve_thread;
2107 tcp->pid = pid;
2108 if (cflag != CFLAG_ONLY_STATS) {
2109 printleader(tcp);
2110 tprintf("+++ superseded by execve in pid %lu +++\n", old_pid);
2111 line_ended();
2112 tcp->flags |= TCB_REPRINT;
2113 }
2114
2115 return tcp;
2116 }
2117
2118 static void
print_signalled(struct tcb * tcp,const int pid,int status)2119 print_signalled(struct tcb *tcp, const int pid, int status)
2120 {
2121 if (pid == strace_child) {
2122 exit_code = 0x100 | WTERMSIG(status);
2123 strace_child = 0;
2124 }
2125
2126 if (cflag != CFLAG_ONLY_STATS
2127 && is_number_in_set(WTERMSIG(status), signal_set)) {
2128 printleader(tcp);
2129 #ifdef WCOREDUMP
2130 tprintf("+++ killed by %s %s+++\n",
2131 signame(WTERMSIG(status)),
2132 WCOREDUMP(status) ? "(core dumped) " : "");
2133 #else
2134 tprintf("+++ killed by %s +++\n",
2135 signame(WTERMSIG(status)));
2136 #endif
2137 line_ended();
2138 }
2139 }
2140
2141 static void
print_exited(struct tcb * tcp,const int pid,int status)2142 print_exited(struct tcb *tcp, const int pid, int status)
2143 {
2144 if (pid == strace_child) {
2145 exit_code = WEXITSTATUS(status);
2146 strace_child = 0;
2147 }
2148
2149 if (cflag != CFLAG_ONLY_STATS &&
2150 qflag < 2) {
2151 printleader(tcp);
2152 tprintf("+++ exited with %d +++\n", WEXITSTATUS(status));
2153 line_ended();
2154 }
2155 }
2156
2157 static void
print_stopped(struct tcb * tcp,const siginfo_t * si,const unsigned int sig)2158 print_stopped(struct tcb *tcp, const siginfo_t *si, const unsigned int sig)
2159 {
2160 if (cflag != CFLAG_ONLY_STATS
2161 && !hide_log(tcp)
2162 && is_number_in_set(sig, signal_set)) {
2163 printleader(tcp);
2164 if (si) {
2165 tprintf("--- %s ", signame(sig));
2166 printsiginfo(si);
2167 tprints(" ---\n");
2168 } else
2169 tprintf("--- stopped by %s ---\n", signame(sig));
2170 line_ended();
2171
2172 #ifdef ENABLE_STACKTRACE
2173 if (stack_trace_enabled)
2174 unwind_tcb_print(tcp);
2175 #endif
2176 }
2177 }
2178
2179 static void
startup_tcb(struct tcb * tcp)2180 startup_tcb(struct tcb *tcp)
2181 {
2182 debug_msg("pid %d has TCB_STARTUP, initializing it", tcp->pid);
2183
2184 tcp->flags &= ~TCB_STARTUP;
2185
2186 if (!use_seize) {
2187 debug_msg("setting opts 0x%x on pid %d",
2188 ptrace_setoptions, tcp->pid);
2189 if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, ptrace_setoptions) < 0) {
2190 if (errno != ESRCH) {
2191 /* Should never happen, really */
2192 perror_msg_and_die("PTRACE_SETOPTIONS");
2193 }
2194 }
2195 }
2196
2197 if ((tcp->flags & TCB_GRABBED) && (get_scno(tcp) == 1))
2198 tcp->s_prev_ent = tcp->s_ent;
2199 }
2200
2201 static void
print_event_exit(struct tcb * tcp)2202 print_event_exit(struct tcb *tcp)
2203 {
2204 if (entering(tcp) || filtered(tcp) || hide_log(tcp)
2205 || cflag == CFLAG_ONLY_STATS) {
2206 return;
2207 }
2208
2209 if (followfork < 2 && printing_tcp && printing_tcp != tcp
2210 && printing_tcp->curcol != 0) {
2211 set_current_tcp(printing_tcp);
2212 tprints(" <unfinished ...>\n");
2213 flush_tcp_output(printing_tcp);
2214 printing_tcp->curcol = 0;
2215 set_current_tcp(tcp);
2216 }
2217
2218 if ((followfork < 2 && printing_tcp != tcp)
2219 || (tcp->flags & TCB_REPRINT)) {
2220 tcp->flags &= ~TCB_REPRINT;
2221 printleader(tcp);
2222 tprintf("<... %s resumed>", tcp->s_ent->sys_name);
2223 }
2224
2225 if (!(tcp->sys_func_rval & RVAL_DECODED)) {
2226 /*
2227 * The decoder has probably decided to print something
2228 * on exiting syscall which is not going to happen.
2229 */
2230 tprints(" <unfinished ...>");
2231 }
2232
2233 printing_tcp = tcp;
2234 tprints(") ");
2235 tabto();
2236 tprints("= ?\n");
2237 line_ended();
2238 }
2239
2240 static const struct tcb_wait_data *
next_event(void)2241 next_event(void)
2242 {
2243 static struct tcb_wait_data wait_data;
2244
2245 int pid;
2246 int status;
2247 struct tcb *tcp;
2248 struct tcb_wait_data *wd = &wait_data;
2249 struct rusage ru;
2250
2251 if (interrupted)
2252 return NULL;
2253
2254 /*
2255 * Used to exit simply when nprocs hits zero, but in this testcase:
2256 * int main(void) { _exit(!!fork()); }
2257 * under strace -f, parent sometimes (rarely) manages
2258 * to exit before we see the first stop of the child,
2259 * and we are losing track of it:
2260 * 19923 clone(...) = 19924
2261 * 19923 exit_group(1) = ?
2262 * 19923 +++ exited with 1 +++
2263 * Exiting only when wait() returns ECHILD works better.
2264 */
2265 if (popen_pid != 0) {
2266 /* However, if -o|logger is in use, we can't do that.
2267 * Can work around that by double-forking the logger,
2268 * but that loses the ability to wait for its completion
2269 * on exit. Oh well...
2270 */
2271 if (nprocs == 0)
2272 return NULL;
2273 }
2274
2275 const bool unblock_delay_timer = is_delay_timer_armed();
2276
2277 /*
2278 * The window of opportunity to handle expirations
2279 * of the delay timer opens here.
2280 *
2281 * Unblock the signal handler for the delay timer
2282 * iff the delay timer is already created.
2283 */
2284 if (unblock_delay_timer)
2285 sigprocmask(SIG_UNBLOCK, &timer_set, NULL);
2286
2287 /*
2288 * If the delay timer has expired, then its expiration
2289 * has been handled already by the signal handler.
2290 *
2291 * If the delay timer expires during wait4(),
2292 * then the system call will be interrupted and
2293 * the expiration will be handled by the signal handler.
2294 */
2295 pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
2296 const int wait_errno = errno;
2297
2298 /*
2299 * The window of opportunity to handle expirations
2300 * of the delay timer closes here.
2301 *
2302 * Block the signal handler for the delay timer
2303 * iff it was unblocked earlier.
2304 */
2305 if (unblock_delay_timer) {
2306 sigprocmask(SIG_BLOCK, &timer_set, NULL);
2307
2308 if (restart_failed)
2309 return NULL;
2310 }
2311
2312 if (pid < 0) {
2313 if (wait_errno == EINTR) {
2314 wd->te = TE_NEXT;
2315 return wd;
2316 }
2317 if (nprocs == 0 && wait_errno == ECHILD)
2318 return NULL;
2319 /*
2320 * If nprocs > 0, ECHILD is not expected,
2321 * treat it as any other error here:
2322 */
2323 errno = wait_errno;
2324 perror_msg_and_die("wait4(__WALL)");
2325 }
2326
2327 wd->status = status;
2328
2329 if (pid == popen_pid) {
2330 if (!WIFSTOPPED(status))
2331 popen_pid = 0;
2332 wd->te = TE_NEXT;
2333 return wd;
2334 }
2335
2336 if (debug_flag)
2337 print_debug_info(pid, status);
2338
2339 /* Look up 'pid' in our table. */
2340 tcp = pid2tcb(pid);
2341
2342 if (!tcp) {
2343 tcp = maybe_allocate_tcb(pid, status);
2344 if (!tcp) {
2345 wd->te = TE_NEXT;
2346 return wd;
2347 }
2348 }
2349
2350 clear_regs(tcp);
2351
2352 /* Set current output file */
2353 set_current_tcp(tcp);
2354
2355 if (cflag) {
2356 struct timespec stime = {
2357 .tv_sec = ru.ru_stime.tv_sec,
2358 .tv_nsec = ru.ru_stime.tv_usec * 1000
2359 };
2360 ts_sub(&tcp->dtime, &stime, &tcp->stime);
2361 tcp->stime = stime;
2362 }
2363
2364 if (WIFSIGNALED(status)) {
2365 wd->te = TE_SIGNALLED;
2366 return wd;
2367 }
2368
2369 if (WIFEXITED(status)) {
2370 wd->te = TE_EXITED;
2371 return wd;
2372 }
2373
2374 /*
2375 * As WCONTINUED flag has not been specified to wait4,
2376 * it cannot be WIFCONTINUED(status), so the only case
2377 * that remains is WIFSTOPPED(status).
2378 */
2379
2380 /* Is this the very first time we see this tracee stopped? */
2381 if (tcp->flags & TCB_STARTUP)
2382 startup_tcb(tcp);
2383
2384 const unsigned int sig = WSTOPSIG(status);
2385 const unsigned int event = (unsigned int) status >> 16;
2386
2387 switch (event) {
2388 case 0:
2389 /*
2390 * Is this post-attach SIGSTOP?
2391 * Interestingly, the process may stop
2392 * with STOPSIG equal to some other signal
2393 * than SIGSTOP if we happened to attach
2394 * just before the process takes a signal.
2395 */
2396 if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
2397 debug_func_msg("ignored SIGSTOP on pid %d", tcp->pid);
2398 tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
2399 wd->te = TE_RESTART;
2400 } else if (sig == syscall_trap_sig) {
2401 wd->te = TE_SYSCALL_STOP;
2402 } else {
2403 memset(&wd->si, 0, sizeof(wd->si));
2404 /*
2405 * True if tracee is stopped by signal
2406 * (as opposed to "tracee received signal").
2407 * TODO: shouldn't we check for errno == EINVAL too?
2408 * We can get ESRCH instead, you know...
2409 */
2410 bool stopped = ptrace(PTRACE_GETSIGINFO, pid, 0, &wd->si) < 0;
2411 wd->te = stopped ? TE_GROUP_STOP : TE_SIGNAL_DELIVERY_STOP;
2412 }
2413 break;
2414 case PTRACE_EVENT_STOP:
2415 /*
2416 * PTRACE_INTERRUPT-stop or group-stop.
2417 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
2418 */
2419 switch (sig) {
2420 case SIGSTOP:
2421 case SIGTSTP:
2422 case SIGTTIN:
2423 case SIGTTOU:
2424 wd->te = TE_GROUP_STOP;
2425 break;
2426 default:
2427 wd->te = TE_RESTART;
2428 }
2429 break;
2430 case PTRACE_EVENT_EXEC:
2431 wd->te = TE_STOP_BEFORE_EXECVE;
2432 break;
2433 case PTRACE_EVENT_EXIT:
2434 wd->te = TE_STOP_BEFORE_EXIT;
2435 break;
2436 default:
2437 wd->te = TE_RESTART;
2438 }
2439
2440 return wd;
2441 }
2442
2443 static int
trace_syscall(struct tcb * tcp,unsigned int * sig)2444 trace_syscall(struct tcb *tcp, unsigned int *sig)
2445 {
2446 if (entering(tcp)) {
2447 int res = syscall_entering_decode(tcp);
2448 switch (res) {
2449 case 0:
2450 return 0;
2451 case 1:
2452 res = syscall_entering_trace(tcp, sig);
2453 }
2454 syscall_entering_finish(tcp, res);
2455 return res;
2456 } else {
2457 struct timespec ts = {};
2458 int res = syscall_exiting_decode(tcp, &ts);
2459 if (res != 0) {
2460 res = syscall_exiting_trace(tcp, &ts, res);
2461 }
2462 syscall_exiting_finish(tcp);
2463 return res;
2464 }
2465 }
2466
2467 /* Returns true iff the main trace loop has to continue. */
2468 static bool
dispatch_event(const struct tcb_wait_data * wd)2469 dispatch_event(const struct tcb_wait_data *wd)
2470 {
2471 unsigned int restart_op = PTRACE_SYSCALL;
2472 unsigned int restart_sig = 0;
2473 enum trace_event te = wd ? wd->te : TE_BREAK;
2474 /*
2475 * Copy wd->status to a non-const variable to workaround glibc bugs
2476 * around union wait fixed by glibc commit glibc-2.24~391
2477 */
2478 int status = wd ? wd->status : 0;
2479
2480 switch (te) {
2481 case TE_BREAK:
2482 return false;
2483
2484 case TE_NEXT:
2485 return true;
2486
2487 case TE_RESTART:
2488 break;
2489
2490 case TE_SYSCALL_STOP:
2491 if (trace_syscall(current_tcp, &restart_sig) < 0) {
2492 /*
2493 * ptrace() failed in trace_syscall().
2494 * Likely a result of process disappearing mid-flight.
2495 * Observed case: exit_group() or SIGKILL terminating
2496 * all processes in thread group.
2497 * We assume that ptrace error was caused by process death.
2498 * We used to detach(current_tcp) here, but since we no
2499 * longer implement "detach before death" policy/hack,
2500 * we can let this process to report its death to us
2501 * normally, via WIFEXITED or WIFSIGNALED wait status.
2502 */
2503 return true;
2504 }
2505 break;
2506
2507 case TE_SIGNAL_DELIVERY_STOP:
2508 restart_sig = WSTOPSIG(status);
2509 print_stopped(current_tcp, &wd->si, restart_sig);
2510 break;
2511
2512 case TE_SIGNALLED:
2513 print_signalled(current_tcp, current_tcp->pid, status);
2514 droptcb(current_tcp);
2515 return true;
2516
2517 case TE_GROUP_STOP:
2518 restart_sig = WSTOPSIG(status);
2519 print_stopped(current_tcp, NULL, restart_sig);
2520 if (use_seize) {
2521 /*
2522 * This ends ptrace-stop, but does *not* end group-stop.
2523 * This makes stopping signals work properly on straced
2524 * process (that is, process really stops. It used to
2525 * continue to run).
2526 */
2527 restart_op = PTRACE_LISTEN;
2528 restart_sig = 0;
2529 }
2530 break;
2531
2532 case TE_EXITED:
2533 print_exited(current_tcp, current_tcp->pid, status);
2534 droptcb(current_tcp);
2535 return true;
2536
2537 case TE_STOP_BEFORE_EXECVE:
2538 /*
2539 * Check that we are inside syscall now (next event after
2540 * PTRACE_EVENT_EXEC should be for syscall exiting). If it is
2541 * not the case, we might have a situation when we attach to a
2542 * process and the first thing we see is a PTRACE_EVENT_EXEC
2543 * and all the following syscall state tracking is screwed up
2544 * otherwise.
2545 */
2546 if (entering(current_tcp)) {
2547 int ret;
2548
2549 error_msg("Stray PTRACE_EVENT_EXEC from pid %d"
2550 ", trying to recover...",
2551 current_tcp->pid);
2552
2553 current_tcp->flags |= TCB_RECOVERING;
2554 ret = trace_syscall(current_tcp, &restart_sig);
2555 current_tcp->flags &= ~TCB_RECOVERING;
2556
2557 if (ret < 0) {
2558 /* The reason is described in TE_SYSCALL_STOP */
2559 return true;
2560 }
2561 }
2562
2563 /*
2564 * Under Linux, execve changes pid to thread leader's pid,
2565 * and we see this changed pid on EVENT_EXEC and later,
2566 * execve sysexit. Leader "disappears" without exit
2567 * notification. Let user know that, drop leader's tcb,
2568 * and fix up pid in execve thread's tcb.
2569 * Effectively, execve thread's tcb replaces leader's tcb.
2570 *
2571 * BTW, leader is 'stuck undead' (doesn't report WIFEXITED
2572 * on exit syscall) in multithreaded programs exactly
2573 * in order to handle this case.
2574 *
2575 * PTRACE_GETEVENTMSG returns old pid starting from Linux 3.0.
2576 * On 2.6 and earlier, it can return garbage.
2577 */
2578 if (os_release >= KERNEL_VERSION(3, 0, 0))
2579 set_current_tcp(maybe_switch_tcbs(current_tcp,
2580 current_tcp->pid));
2581
2582 if (detach_on_execve) {
2583 if (current_tcp->flags & TCB_SKIP_DETACH_ON_FIRST_EXEC) {
2584 current_tcp->flags &= ~TCB_SKIP_DETACH_ON_FIRST_EXEC;
2585 } else {
2586 detach(current_tcp); /* do "-b execve" thingy */
2587 return true;
2588 }
2589 }
2590 break;
2591
2592 case TE_STOP_BEFORE_EXIT:
2593 print_event_exit(current_tcp);
2594 break;
2595 }
2596
2597 /* We handled quick cases, we are permitted to interrupt now. */
2598 if (interrupted)
2599 return false;
2600
2601 /* If the process is being delayed, do not ptrace_restart just yet */
2602 if (syscall_delayed(current_tcp))
2603 return true;
2604
2605 if (ptrace_restart(restart_op, current_tcp, restart_sig) < 0) {
2606 /* Note: ptrace_restart emitted error message */
2607 exit_code = 1;
2608 return false;
2609 }
2610 return true;
2611 }
2612
2613 static bool
restart_delayed_tcb(struct tcb * const tcp)2614 restart_delayed_tcb(struct tcb *const tcp)
2615 {
2616 const struct tcb_wait_data wd = { .te = TE_RESTART };
2617
2618 debug_func_msg("pid %d", tcp->pid);
2619
2620 tcp->flags &= ~TCB_DELAYED;
2621
2622 struct tcb *const prev_tcp = current_tcp;
2623 current_tcp = tcp;
2624 bool ret = dispatch_event(&wd);
2625 current_tcp = prev_tcp;
2626
2627 return ret;
2628 }
2629
2630 static bool
restart_delayed_tcbs(void)2631 restart_delayed_tcbs(void)
2632 {
2633 struct tcb *tcp_next = NULL;
2634 struct timespec ts_now;
2635
2636 clock_gettime(CLOCK_MONOTONIC, &ts_now);
2637
2638 for (size_t i = 0; i < tcbtabsize; i++) {
2639 struct tcb *tcp = tcbtab[i];
2640
2641 if (tcp->pid && syscall_delayed(tcp)) {
2642 if (ts_cmp(&ts_now, &tcp->delay_expiration_time) > 0) {
2643 if (!restart_delayed_tcb(tcp))
2644 return false;
2645 } else {
2646 /* Check whether this tcb is the next. */
2647 if (!tcp_next ||
2648 ts_cmp(&tcp_next->delay_expiration_time,
2649 &tcp->delay_expiration_time) > 0) {
2650 tcp_next = tcp;
2651 }
2652 }
2653 }
2654 }
2655
2656 if (tcp_next)
2657 arm_delay_timer(tcp_next);
2658
2659 return true;
2660 }
2661
2662 /*
2663 * As this signal handler does a lot of work that is not suitable
2664 * for signal handlers, extra care must be taken to ensure that
2665 * it is enabled only in those places where it's safe.
2666 */
2667 static void
timer_sighandler(int sig)2668 timer_sighandler(int sig)
2669 {
2670 delay_timer_expired();
2671
2672 if (restart_failed)
2673 return;
2674
2675 int saved_errno = errno;
2676
2677 if (!restart_delayed_tcbs())
2678 restart_failed = 1;
2679
2680 errno = saved_errno;
2681 }
2682
2683 #ifdef ENABLE_COVERAGE_GCOV
2684 extern void __gcov_flush(void);
2685 #endif
2686
2687 static void ATTRIBUTE_NORETURN
terminate(void)2688 terminate(void)
2689 {
2690 cleanup();
2691 fflush(NULL);
2692 if (shared_log != stderr)
2693 fclose(shared_log);
2694 if (popen_pid) {
2695 while (waitpid(popen_pid, NULL, 0) < 0 && errno == EINTR)
2696 ;
2697 }
2698 if (exit_code > 0xff) {
2699 /* Avoid potential core file clobbering. */
2700 struct_rlimit rlim = {0, 0};
2701 set_rlimit(RLIMIT_CORE, &rlim);
2702
2703 /* Child was killed by a signal, mimic that. */
2704 exit_code &= 0xff;
2705 signal(exit_code, SIG_DFL);
2706 #ifdef ENABLE_COVERAGE_GCOV
2707 __gcov_flush();
2708 #endif
2709 raise(exit_code);
2710
2711 /* Unblock the signal. */
2712 sigset_t mask;
2713 sigemptyset(&mask);
2714 sigaddset(&mask, exit_code);
2715 #ifdef ENABLE_COVERAGE_GCOV
2716 __gcov_flush();
2717 #endif
2718 sigprocmask(SIG_UNBLOCK, &mask, NULL);
2719
2720 /* Paranoia - what if this signal is not fatal?
2721 Exit with 128 + signo then. */
2722 exit_code += 128;
2723 }
2724 exit(exit_code);
2725 }
2726
2727 int
main(int argc,char * argv[])2728 main(int argc, char *argv[])
2729 {
2730 setlocale(LC_ALL, "");
2731 init(argc, argv);
2732
2733 exit_code = !nprocs;
2734
2735 while (dispatch_event(next_event()))
2736 ;
2737 terminate();
2738 }
2739