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>
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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.
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.
33 #include <sys/param.h>
35 #include <sys/resource.h>
41 #include <sys/utsname.h>
43 # include <sys/prctl.h>
48 /* In some libc, these aren't declared. Do it ourself: */
49 extern char **environ;
54 /* if this is true do the stack trace for every system call */
55 bool stack_trace_enabled = false;
58 #if defined __NR_tkill
59 # define my_tkill(tid, sig) syscall(__NR_tkill, (tid), (sig))
61 /* kill() may choose arbitrarily the target task of the process group
62 while we later wait on a that specific TID. PID process waits become
63 TID task specific waits for a process under ptrace(2). */
64 # warning "tkill(2) not available, risk of strace hangs!"
65 # define my_tkill(tid, sig) kill((tid), (sig))
68 /* Glue for systems without a MMU that cannot provide fork() */
69 #if !defined(HAVE_FORK)
71 # define NOMMU_SYSTEM 1
74 # define fork() vfork()
77 const unsigned int syscall_trap_sig = SIGTRAP | 0x80;
79 cflag_t cflag = CFLAG_NONE;
80 unsigned int followfork = 0;
81 unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC;
82 unsigned int xflag = 0;
86 bool count_wallclock = 0;
87 unsigned int qflag = 0;
88 static unsigned int tflag = 0;
89 static bool rflag = 0;
90 static bool print_pid_pfx = 0;
95 INTR_ANYWHERE = 1, /* don't block/ignore any signals */
96 INTR_WHILE_WAIT = 2, /* block fatal signals while decoding syscall. default */
97 INTR_NEVER = 3, /* block fatal signals. default if '-o FILE PROG' */
98 INTR_BLOCK_TSTP_TOO = 4, /* block fatal signals and SIGTSTP (^Z) */
102 /* We play with signal mask only if this mode is active: */
103 #define interactive (opt_intr == INTR_WHILE_WAIT)
106 * daemonized_tracer supports -D option.
107 * With this option, strace forks twice.
108 * Unlike normal case, with -D *grandparent* process exec's,
109 * becoming a traced process. Child exits (this prevents traced process
110 * from having children it doesn't expect to have), and grandchild
111 * attaches to grandparent similarly to strace -p PID.
112 * This allows for more transparent interaction in cases
113 * when process and its parent are communicating via signals,
114 * wait() etc. Without -D, strace process gets lodged in between,
115 * disrupting parent<->child link.
117 static bool daemonized_tracer = 0;
120 static int post_attach_sigstop = TCB_IGNORE_ONE_SIGSTOP;
121 # define use_seize (post_attach_sigstop == 0)
123 # define post_attach_sigstop TCB_IGNORE_ONE_SIGSTOP
127 /* Sometimes we want to print only succeeding syscalls. */
128 bool not_failing_only = 0;
130 /* Show path associated with fd arguments */
131 unsigned int show_fd_path = 0;
133 static bool detach_on_execve = 0;
134 /* Are we "strace PROG" and need to skip detach on first execve? */
135 static bool skip_one_b_execve = 0;
136 /* Are we "strace PROG" and need to hide everything until execve? */
137 bool hide_log_until_execve = 0;
139 static int exit_code = 0;
140 static int strace_child = 0;
141 static int strace_tracer_pid = 0;
143 static char *username = NULL;
144 static uid_t run_uid;
145 static gid_t run_gid;
147 unsigned int max_strlen = DEFAULT_STRLEN;
148 static int acolumn = DEFAULT_ACOLUMN;
149 static char *acolumn_spaces;
151 static char *outfname = NULL;
152 /* If -ff, points to stderr. Else, it's our common output log */
153 static FILE *shared_log;
155 struct tcb *printing_tcp = NULL;
156 static struct tcb *current_tcp;
158 static struct tcb **tcbtab;
159 static unsigned int nprocs, tcbtabsize;
160 static const char *progname;
162 unsigned os_release; /* generated from uname()'s u.release */
164 static void detach(struct tcb *tcp);
165 static void cleanup(void);
166 static void interrupt(int sig);
167 static sigset_t empty_set, blocked_set;
169 #ifdef HAVE_SIG_ATOMIC_T
170 static volatile sig_atomic_t interrupted;
172 static volatile int interrupted;
175 #ifndef HAVE_STRERROR
177 #if !HAVE_DECL_SYS_ERRLIST
179 extern char *sys_errlist[];
185 static char buf[sizeof("Unknown error %d") + sizeof(int)*3];
187 if (err_no < 1 || err_no >= sys_nerr) {
188 sprintf(buf, "Unknown error %d", err_no);
191 return sys_errlist[err_no];
194 #endif /* HAVE_STERRROR */
197 usage(FILE *ofp, int exitval)
200 usage: strace [-CdffhiqrtttTvVxxy] [-I n] [-e expr]...\n\
201 [-a column] [-o file] [-s strsize] [-P path]...\n\
202 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
203 or: strace -c[df] [-I n] [-e expr]... [-O overhead] [-S sortby]\n\
204 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
205 -c -- count time, calls, and errors for each syscall and report summary\n\
206 -C -- like -c but also print regular output\n\
207 -w -- summarise syscall latency (default is system time)\n\
208 -d -- enable debug output to stderr\n\
209 -D -- run tracer process as a detached grandchild, not as parent\n\
210 -f -- follow forks, -ff -- with output into separate files\n\
211 -i -- print instruction pointer at time of syscall\n\
212 -q -- suppress messages about attaching, detaching, etc.\n\
213 -r -- print relative timestamp, -t -- absolute timestamp, -tt -- with usecs\n\
214 -T -- print time spent in each syscall\n\
215 -v -- verbose mode: print unabbreviated argv, stat, termios, etc. args\n\
216 -x -- print non-ascii strings in hex, -xx -- print all strings in hex\n\
217 -y -- print paths associated with file descriptor arguments\n\
218 -yy -- print ip:port pairs associated with socket file descriptors\n\
219 -h -- print help message, -V -- print version\n\
220 -a column -- alignment COLUMN for printing syscall results (default %d)\n\
221 -b execve -- detach on this syscall\n\
222 -e expr -- a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
223 options: trace, abbrev, verbose, raw, signal, read, write\n\
224 -I interruptible --\n\
225 1: no signals are blocked\n\
226 2: fatal signals are blocked while decoding syscall (default)\n\
227 3: fatal signals are always blocked (default if '-o FILE PROG')\n\
228 4: fatal signals and SIGTSTP (^Z) are always blocked\n\
229 (useful to make 'strace -o FILE PROG' not stop on ^Z)\n\
230 -o file -- send trace output to FILE instead of stderr\n\
231 -O overhead -- set overhead for tracing syscalls to OVERHEAD usecs\n\
232 -p pid -- trace process with process id PID, may be repeated\n\
233 -s strsize -- limit length of print strings to STRSIZE chars (default %d)\n\
234 -S sortby -- sort syscall counts by: time, calls, name, nothing (default %s)\n\
235 -u username -- run command as username handling setuid and/or setgid\n\
236 -E var=val -- put var=val in the environment for command\n\
237 -E var -- remove var from the environment for command\n\
238 -P path -- trace accesses to path\n\
241 "-k obtain stack trace between each syscall (experimental)\n\
244 /* ancient, no one should use it
245 -F -- attempt to follow vforks (deprecated, use -f)\n\
247 /* this is broken, so don't document it
248 -z -- print only succeeding syscalls\n\
250 , DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
254 static void ATTRIBUTE_NORETURN
257 if (strace_tracer_pid == getpid()) {
264 static void verror_msg(int err_no, const char *fmt, va_list p)
270 /* We want to print entire message with single fprintf to ensure
271 * message integrity if stderr is shared with other programs.
272 * Thus we use vasprintf + single fprintf.
275 if (vasprintf(&msg, fmt, p) >= 0) {
277 fprintf(stderr, "%s: %s: %s\n", progname, msg, strerror(err_no));
279 fprintf(stderr, "%s: %s\n", progname, msg);
282 /* malloc in vasprintf failed, try it without malloc */
283 fprintf(stderr, "%s: ", progname);
284 vfprintf(stderr, fmt, p);
286 fprintf(stderr, ": %s\n", strerror(err_no));
290 /* We don't switch stderr to buffered, thus fprintf(stderr)
291 * always flushes its output and this is not necessary: */
292 /* fflush(stderr); */
295 void error_msg(const char *fmt, ...)
299 verror_msg(0, fmt, p);
303 void error_msg_and_die(const char *fmt, ...)
307 verror_msg(0, fmt, p);
311 void perror_msg(const char *fmt, ...)
315 verror_msg(errno, fmt, p);
319 void perror_msg_and_die(const char *fmt, ...)
323 verror_msg(errno, fmt, p);
328 error_opt_arg(int opt, const char *arg)
330 error_msg_and_die("Invalid -%c argument: '%s'", opt, arg);
335 ptrace_attach_or_seize(int pid)
339 return ptrace(PTRACE_ATTACH, pid, 0L, 0L);
340 r = ptrace(PTRACE_SEIZE, pid, 0L, (unsigned long) ptrace_setoptions);
343 r = ptrace(PTRACE_INTERRUPT, pid, 0L, 0L);
347 # define ptrace_attach_or_seize(pid) ptrace(PTRACE_ATTACH, (pid), 0, 0)
351 * Used when we want to unblock stopped traced process.
352 * Should be only used with PTRACE_CONT, PTRACE_DETACH and PTRACE_SYSCALL.
353 * Returns 0 on success or if error was ESRCH
354 * (presumably process was killed while we talk to it).
355 * Otherwise prints error message and returns -1.
358 ptrace_restart(int op, struct tcb *tcp, int sig)
364 ptrace(op, tcp->pid, (void *) 0, (long) sig);
370 if (op == PTRACE_CONT)
372 if (op == PTRACE_DETACH)
375 if (op == PTRACE_LISTEN)
379 * Why curcol != 0? Otherwise sometimes we get this:
381 * 10252 kill(10253, SIGKILL) = 0
382 * <ptrace(SYSCALL,10252):No such process>10253 ...next decode...
384 * 10252 died after we retrieved syscall exit data,
385 * but before we tried to restart it. Log looks ugly.
387 if (current_tcp && current_tcp->curcol != 0) {
388 tprintf(" <ptrace(%s):%s>\n", msg, strerror(err));
394 perror_msg("ptrace(PTRACE_%s,pid:%d,sig:%d)", msg, tcp->pid, sig);
399 set_cloexec_flag(int fd)
403 flags = fcntl(fd, F_GETFD);
405 /* Can happen only if fd is bad.
406 * Should never happen: if it does, we have a bug
407 * in the caller. Therefore we just abort
408 * instead of propagating the error.
410 perror_msg_and_die("fcntl(%d, F_GETFD)", fd);
413 newflags = flags | FD_CLOEXEC;
414 if (flags == newflags)
417 fcntl(fd, F_SETFD, newflags); /* never fails */
420 static void kill_save_errno(pid_t pid, int sig)
422 int saved_errno = errno;
424 (void) kill(pid, sig);
429 * When strace is setuid executable, we have to swap uids
430 * before and after filesystem and process management operations.
435 int euid = geteuid(), uid = getuid();
437 if (euid != uid && setreuid(euid, uid) < 0) {
438 perror_msg_and_die("setreuid");
442 #ifdef _LARGEFILE64_SOURCE
444 # define fopen_for_output fopen64
446 # define fopen_for_output fopen
448 # define struct_stat struct stat64
449 # define stat_file stat64
450 # define struct_dirent struct dirent64
451 # define read_dir readdir64
452 # define struct_rlimit struct rlimit64
453 # define set_rlimit setrlimit64
455 # define fopen_for_output fopen
456 # define struct_stat struct stat
457 # define stat_file stat
458 # define struct_dirent struct dirent
459 # define read_dir readdir
460 # define struct_rlimit struct rlimit
461 # define set_rlimit setrlimit
465 strace_fopen(const char *path)
470 fp = fopen_for_output(path, "w");
472 perror_msg_and_die("Can't fopen '%s'", path);
474 set_cloexec_flag(fileno(fp));
478 static int popen_pid = 0;
481 # define _PATH_BSHELL "/bin/sh"
485 * We cannot use standard popen(3) here because we have to distinguish
486 * popen child process from other processes we trace, and standard popen(3)
487 * does not export its child's pid.
490 strace_popen(const char *command)
498 perror_msg_and_die("pipe");
500 set_cloexec_flag(fds[1]); /* never fails */
504 perror_msg_and_die("vfork");
511 perror_msg_and_die("dup2");
514 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
515 perror_msg_and_die("Can't execute '%s'", _PATH_BSHELL);
522 fp = fdopen(fds[1], "w");
529 tprintf(const char *fmt, ...)
535 int n = strace_vfprintf(current_tcp->outf, fmt, args);
537 if (current_tcp->outf != stderr)
538 perror_msg("%s", outfname);
540 current_tcp->curcol += n;
545 #ifndef HAVE_FPUTS_UNLOCKED
546 # define fputs_unlocked fputs
550 tprints(const char *str)
553 int n = fputs_unlocked(str, current_tcp->outf);
555 current_tcp->curcol += strlen(str);
558 if (current_tcp->outf != stderr)
559 perror_msg("%s", outfname);
567 current_tcp->curcol = 0;
568 fflush(current_tcp->outf);
571 printing_tcp->curcol = 0;
577 printleader(struct tcb *tcp)
579 /* If -ff, "previous tcb we printed" is always the same as current,
580 * because we have per-tcb output files.
586 current_tcp = printing_tcp;
587 if (printing_tcp->curcol != 0 && (followfork < 2 || printing_tcp == tcp)) {
589 * case 1: we have a shared log (i.e. not -ff), and last line
590 * wasn't finished (same or different tcb, doesn't matter).
591 * case 2: split log, we are the same tcb, but our last line
592 * didn't finish ("SIGKILL nuked us after syscall entry" etc).
594 tprints(" <unfinished ...>\n");
595 printing_tcp->curcol = 0;
601 current_tcp->curcol = 0;
604 tprintf("%-5d ", tcp->pid);
605 else if (nprocs > 1 && !outfname)
606 tprintf("[pid %5u] ", tcp->pid);
609 char str[sizeof("HH:MM:SS")];
610 struct timeval tv, dtv;
611 static struct timeval otv;
613 gettimeofday(&tv, NULL);
617 tv_sub(&dtv, &tv, &otv);
618 tprintf("%6ld.%06ld ",
619 (long) dtv.tv_sec, (long) dtv.tv_usec);
622 else if (tflag > 2) {
623 tprintf("%ld.%06ld ",
624 (long) tv.tv_sec, (long) tv.tv_usec);
627 time_t local = tv.tv_sec;
628 strftime(str, sizeof(str), "%T", localtime(&local));
630 tprintf("%s.%06ld ", str, (long) tv.tv_usec);
642 if (current_tcp->curcol < acolumn)
643 tprints(acolumn_spaces + current_tcp->curcol);
646 /* Should be only called directly *after successful attach* to a tracee.
647 * Otherwise, "strace -oFILE -ff -p<nonexistant_pid>"
648 * may create bogus empty FILE.<nonexistant_pid>, and then die.
651 newoutf(struct tcb *tcp)
653 tcp->outf = shared_log; /* if not -ff mode, the same file is for all */
654 if (followfork >= 2) {
655 char name[520 + sizeof(int) * 3];
656 sprintf(name, "%.512s.%u", outfname, tcp->pid);
657 tcp->outf = strace_fopen(name);
664 /* Allocate some more TCBs and expand the table.
665 We don't want to relocate the TCBs because our
666 callers have pointers and it would be a pain.
667 So tcbtab is a table of pointers. Since we never
668 free the TCBs, we allocate a single chunk of many. */
669 unsigned int i = tcbtabsize;
670 struct tcb *newtcbs = xcalloc(tcbtabsize, sizeof(newtcbs[0]));
671 struct tcb **newtab = xreallocarray(tcbtab, tcbtabsize * 2,
675 while (i < tcbtabsize)
676 tcbtab[i++] = newtcbs++;
685 if (nprocs == tcbtabsize)
688 for (i = 0; i < tcbtabsize; i++) {
691 memset(tcp, 0, sizeof(*tcp));
693 #if SUPPORTED_PERSONALITIES > 1
694 tcp->currpers = current_personality;
698 if (stack_trace_enabled)
699 unwind_tcb_init(tcp);
704 error_msg("new tcb for pid %d, active tcbs:%d",
709 error_msg_and_die("bug in alloctcb");
713 droptcb(struct tcb *tcp)
719 if (stack_trace_enabled) {
726 error_msg("dropped tcb for pid %d, %d remain",
730 if (followfork >= 2) {
731 if (tcp->curcol != 0)
732 fprintf(tcp->outf, " <detached ...>\n");
735 if (printing_tcp == tcp && tcp->curcol != 0)
736 fprintf(tcp->outf, " <detached ...>\n");
741 if (current_tcp == tcp)
743 if (printing_tcp == tcp)
746 memset(tcp, 0, sizeof(*tcp));
749 /* Detach traced process.
750 * Never call DETACH twice on the same process as both unattached and
751 * attached-unstopped processes give the same ESRCH. For unattached process we
752 * would SIGSTOP it and wait for its SIGSTOP notification forever.
755 detach(struct tcb *tcp)
761 * Linux wrongly insists the child be stopped
762 * before detaching. Arghh. We go through hoops
763 * to make a clean break of things.
766 # undef PTRACE_DETACH
767 # define PTRACE_DETACH PTRACE_SUNDETACH
770 if (!(tcp->flags & TCB_ATTACHED))
773 /* We attached but possibly didn't see the expected SIGSTOP.
774 * We must catch exactly one as otherwise the detached process
775 * would be left stopped (process state T).
777 if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
780 error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
782 /* On a clear day, you can see forever. */
785 if (errno != ESRCH) {
786 /* Shouldn't happen. */
787 perror_msg("detach: ptrace(PTRACE_DETACH,%u)", tcp->pid);
790 /* ESRCH: process is either not stopped or doesn't exist. */
791 if (my_tkill(tcp->pid, 0) < 0) {
793 /* Shouldn't happen. */
794 perror_msg("detach: tkill(%u,0)", tcp->pid);
795 /* else: process doesn't exist. */
798 /* Process is not stopped, need to stop it. */
801 * With SEIZE, tracee can be in group-stop already.
802 * In this state sending it another SIGSTOP does nothing.
803 * Need to use INTERRUPT.
804 * Testcase: trying to ^C a "strace -p <stopped_process>".
806 error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
810 perror_msg("detach: ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
813 error = my_tkill(tcp->pid, SIGSTOP);
817 perror_msg("detach: tkill(%u,SIGSTOP)", tcp->pid);
819 /* Either process doesn't exist, or some weird error. */
823 /* We end up here in three cases:
824 * 1. We sent PTRACE_INTERRUPT (use_seize case)
825 * 2. We sent SIGSTOP (!use_seize)
826 * 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
830 if (waitpid(tcp->pid, &status, __WALL) < 0) {
834 * if (errno == ECHILD) break;
835 * ^^^ WRONG! We expect this PID to exist,
836 * and want to emit a message otherwise:
838 perror_msg("detach: waitpid(%u)", tcp->pid);
841 if (!WIFSTOPPED(status)) {
843 * Tracee exited or was killed by signal.
844 * We shouldn't normally reach this place:
845 * we don't want to consume exit status.
846 * Consider "strace -p PID" being ^C-ed:
847 * we want merely to detach from PID.
849 * However, we _can_ end up here if tracee
854 sig = WSTOPSIG(status);
856 error_msg("detach wait: event:%d sig:%d",
857 (unsigned)status >> 16, sig);
859 unsigned event = (unsigned)status >> 16;
860 if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
862 * sig == SIGTRAP: PTRACE_INTERRUPT stop.
863 * sig == other: process was already stopped
864 * with this stopping sig (see tests/detach-stopped).
865 * Looks like re-injecting this sig is not necessary
866 * in DETACH for the tracee to remain stopped.
871 * PTRACE_INTERRUPT is not guaranteed to produce
872 * the above event if other ptrace-stop is pending.
873 * See tests/detach-sleeping testcase:
874 * strace got SIGINT while tracee is sleeping.
875 * We sent PTRACE_INTERRUPT.
876 * We see syscall exit, not PTRACE_INTERRUPT stop.
877 * We won't get PTRACE_INTERRUPT stop
878 * if we would CONT now. Need to DETACH.
880 if (sig == syscall_trap_sig)
882 /* else: not sure in which case we can be here.
883 * Signal stop? Inject it while detaching.
885 ptrace_restart(PTRACE_DETACH, tcp, sig);
888 /* Note: this check has to be after use_seize check */
889 /* (else, in use_seize case SIGSTOP will be mistreated) */
890 if (sig == SIGSTOP) {
891 /* Detach, suppressing SIGSTOP */
892 ptrace_restart(PTRACE_DETACH, tcp, 0);
895 if (sig == syscall_trap_sig)
897 /* Can't detach just yet, may need to wait for SIGSTOP */
898 error = ptrace_restart(PTRACE_CONT, tcp, sig);
900 /* Should not happen.
901 * Note: ptrace_restart returns 0 on ESRCH, so it's not it.
902 * ptrace_restart already emitted error message.
909 if (!qflag && (tcp->flags & TCB_ATTACHED))
910 error_msg("Process %u detached", tcp->pid);
916 process_opt_p_list(char *opt)
920 * We accept -p PID,PID; -p "`pidof PROG`"; -p "`pgrep PROG`".
921 * pidof uses space as delim, pgrep uses newline. :(
924 char *delim = opt + strcspn(opt, ", \n\t");
928 pid = string_to_uint(opt);
930 error_msg_and_die("Invalid process id: '%s'", opt);
932 if (pid == strace_tracer_pid) {
933 error_msg_and_die("I'm sorry, I can't let you do that, Dave.");
950 * Block user interruptions as we would leave the traced
951 * process stopped (process state T) if we would terminate in
952 * between PTRACE_ATTACH and wait4() on SIGSTOP.
953 * We rely on cleanup() from this point on.
956 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
958 if (daemonized_tracer) {
961 perror_msg_and_die("fork");
963 if (pid) { /* parent */
965 * Wait for grandchild to attach to straced process
966 * (grandparent). Grandchild SIGKILLs us after it attached.
967 * Grandparent's wait() is unblocked by our death,
968 * it proceeds to exec the straced program.
971 _exit(0); /* paranoia */
974 /* We will be the tracer process. Remember our new pid: */
975 strace_tracer_pid = getpid();
978 for (tcbi = 0; tcbi < tcbtabsize; tcbi++) {
984 /* Is this a process we should attach to, but not yet attached? */
985 if (tcp->flags & TCB_ATTACHED)
986 continue; /* no, we already attached it */
988 if (followfork && !daemonized_tracer) {
989 char procdir[sizeof("/proc/%d/task") + sizeof(int) * 3];
992 sprintf(procdir, "/proc/%d/task", tcp->pid);
993 dir = opendir(procdir);
995 unsigned int ntid = 0, nerr = 0;
998 while ((de = read_dir(dir)) != NULL) {
1002 if (de->d_fileno == 0)
1004 /* we trust /proc filesystem */
1005 tid = atoi(de->d_name);
1009 if (ptrace_attach_or_seize(tid) < 0) {
1012 error_msg("attach to pid %d failed", tid);
1016 error_msg("attach to pid %d succeeded", tid);
1018 if (tid != tcp->pid)
1019 cur_tcp = alloctcb(tid);
1020 cur_tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1025 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1028 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
1032 perror_msg("attach: ptrace(PTRACE_ATTACH, ...)");
1038 ? "Process %u attached with %u threads"
1039 : "Process %u attached",
1042 if (!(tcp->flags & TCB_ATTACHED)) {
1043 /* -p PID, we failed to attach to PID itself
1044 * but did attach to some of its sibling threads.
1050 } /* if (opendir worked) */
1052 if (ptrace_attach_or_seize(tcp->pid) < 0) {
1053 perror_msg("attach: ptrace(PTRACE_ATTACH, ...)");
1057 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1060 error_msg("attach to pid %d (main) succeeded", tcp->pid);
1062 if (daemonized_tracer) {
1064 * Make parent go away.
1065 * Also makes grandparent's wait() unblock.
1067 kill(getppid(), SIGKILL);
1071 error_msg("Process %u attached", tcp->pid);
1072 } /* for each tcbtab[] */
1076 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1079 /* Stack-o-phobic exec helper, in the hope to work around
1080 * NOMMU + "daemonized tracer" difficulty.
1082 struct exec_params {
1089 static struct exec_params params_for_tracee;
1091 static void ATTRIBUTE_NOINLINE ATTRIBUTE_NORETURN
1094 struct exec_params *params = ¶ms_for_tracee;
1096 if (params->fd_to_close >= 0)
1097 close(params->fd_to_close);
1098 if (!daemonized_tracer && !use_seize) {
1099 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0) {
1100 perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
1104 if (username != NULL) {
1106 * It is important to set groups before we
1107 * lose privileges on setuid.
1109 if (initgroups(username, run_gid) < 0) {
1110 perror_msg_and_die("initgroups");
1112 if (setregid(run_gid, params->run_egid) < 0) {
1113 perror_msg_and_die("setregid");
1115 if (setreuid(run_uid, params->run_euid) < 0) {
1116 perror_msg_and_die("setreuid");
1119 else if (geteuid() != 0)
1120 if (setreuid(run_uid, run_uid) < 0) {
1121 perror_msg_and_die("setreuid");
1124 if (!daemonized_tracer) {
1126 * Induce a ptrace stop. Tracer (our parent)
1127 * will resume us with PTRACE_SYSCALL and display
1128 * the immediately following execve syscall.
1129 * Can't do this on NOMMU systems, we are after
1130 * vfork: parent is blocked, stopping would deadlock.
1133 kill(getpid(), SIGSTOP);
1136 /* we depend on SIGCHLD set to SIG_DFL by init code */
1137 /* if it happens to be SIG_IGN'ed, wait won't block */
1142 execv(params->pathname, params->argv);
1143 perror_msg_and_die("exec");
1147 startup_child(char **argv)
1149 struct_stat statbuf;
1150 const char *filename;
1151 size_t filename_len;
1152 char pathname[PATH_MAX];
1157 filename_len = strlen(filename);
1159 if (filename_len > sizeof(pathname) - 1) {
1160 errno = ENAMETOOLONG;
1161 perror_msg_and_die("exec");
1163 if (strchr(filename, '/')) {
1164 strcpy(pathname, filename);
1166 #ifdef USE_DEBUGGING_EXEC
1168 * Debuggers customarily check the current directory
1169 * first regardless of the path but doing that gives
1170 * security geeks a panic attack.
1172 else if (stat_file(filename, &statbuf) == 0)
1173 strcpy(pathname, filename);
1174 #endif /* USE_DEBUGGING_EXEC */
1179 for (path = getenv("PATH"); path && *path; path += m) {
1180 const char *colon = strchr(path, ':');
1186 m = n = strlen(path);
1188 if (!getcwd(pathname, PATH_MAX))
1190 len = strlen(pathname);
1192 else if (n > sizeof pathname - 1)
1195 strncpy(pathname, path, n);
1198 if (len && pathname[len - 1] != '/')
1199 pathname[len++] = '/';
1200 if (filename_len + len > sizeof(pathname) - 1)
1202 strcpy(pathname + len, filename);
1203 if (stat_file(pathname, &statbuf) == 0 &&
1204 /* Accept only regular files
1205 with some execute bits set.
1206 XXX not perfect, might still fail */
1207 S_ISREG(statbuf.st_mode) &&
1208 (statbuf.st_mode & 0111))
1211 if (!path || !*path)
1214 if (stat_file(pathname, &statbuf) < 0) {
1215 perror_msg_and_die("Can't stat '%s'", filename);
1218 params_for_tracee.fd_to_close = (shared_log != stderr) ? fileno(shared_log) : -1;
1219 params_for_tracee.run_euid = (statbuf.st_mode & S_ISUID) ? statbuf.st_uid : run_uid;
1220 params_for_tracee.run_egid = (statbuf.st_mode & S_ISGID) ? statbuf.st_gid : run_gid;
1221 params_for_tracee.argv = argv;
1223 * On NOMMU, can be safely freed only after execve in tracee.
1224 * It's hard to know when that happens, so we just leak it.
1226 params_for_tracee.pathname = NOMMU_SYSTEM ? xstrdup(pathname) : pathname;
1228 #if defined HAVE_PRCTL && defined PR_SET_PTRACER && defined PR_SET_PTRACER_ANY
1229 if (daemonized_tracer)
1230 prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
1235 perror_msg_and_die("fork");
1237 if ((pid != 0 && daemonized_tracer)
1238 || (pid == 0 && !daemonized_tracer)
1240 /* We are to become the tracee. Two cases:
1242 * not -D: we are child
1247 /* We are the tracer */
1249 if (!daemonized_tracer) {
1252 /* child did PTRACE_TRACEME, nothing to do in parent */
1254 if (!NOMMU_SYSTEM) {
1255 /* Wait until child stopped itself */
1257 while (waitpid(pid, &status, WSTOPPED) < 0) {
1260 perror_msg_and_die("waitpid");
1262 if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGSTOP) {
1263 kill_save_errno(pid, SIGKILL);
1264 perror_msg_and_die("Unexpected wait status %x", status);
1267 /* Else: NOMMU case, we have no way to sync.
1268 * Just attach to it as soon as possible.
1269 * This means that we may miss a few first syscalls...
1272 if (ptrace_attach_or_seize(pid)) {
1273 kill_save_errno(pid, SIGKILL);
1274 perror_msg_and_die("Can't attach to %d", pid);
1279 tcp = alloctcb(pid);
1281 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1283 tcp->flags |= TCB_ATTACHED | TCB_STARTUP;
1287 /* With -D, we are *child* here, IOW: different pid. Fetch it: */
1288 strace_tracer_pid = getpid();
1289 /* The tracee is our parent: */
1292 /* attaching will be done later, by startup_attach */
1293 /* note: we don't do newoutf(tcp) here either! */
1295 /* NOMMU BUG! -D mode is active, we (child) return,
1296 * and we will scribble over parent's stack!
1297 * When parent later unpauses, it segfaults.
1300 * (1) by declaring exec_or_die() NORETURN,
1301 * hopefully compiler will just jump to it
1302 * instead of call (won't push anything to stack),
1303 * (2) by trying very hard in exec_or_die()
1304 * to not use any stack,
1305 * (3) having a really big (PATH_MAX) stack object
1306 * in this function, which creates a "buffer" between
1307 * child's and parent's stack pointers.
1308 * This may save us if (1) and (2) failed
1309 * and compiler decided to use stack in exec_or_die() anyway
1310 * (happens on i386 because of stack parameter passing).
1312 * A cleaner solution is to use makecontext + setcontext
1313 * to create a genuine separate stack and execute on it.
1320 test_ptrace_seize(void)
1324 /* Need fork for test. NOMMU has no forks */
1326 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1332 perror_msg_and_die("fork");
1339 /* PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After
1340 * attaching tracee continues to run unless a trap condition occurs.
1341 * PTRACE_SEIZE doesn't affect signal or group stop state.
1343 if (ptrace(PTRACE_SEIZE, pid, 0, 0) == 0) {
1344 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1345 } else if (debug_flag) {
1346 error_msg("PTRACE_SEIZE doesn't work");
1352 int status, tracee_pid;
1355 tracee_pid = waitpid(pid, &status, 0);
1356 if (tracee_pid <= 0) {
1359 perror_msg_and_die("%s: unexpected wait result %d",
1360 __func__, tracee_pid);
1362 if (WIFSIGNALED(status)) {
1365 error_msg_and_die("%s: unexpected wait status %x",
1369 #else /* !USE_SEIZE */
1370 # define test_ptrace_seize() ((void)0)
1374 get_os_release(void)
1380 perror_msg_and_die("uname");
1381 /* u.release has this form: "3.2.9[-some-garbage]" */
1385 if (!(*p >= '0' && *p <= '9'))
1386 error_msg_and_die("Bad OS release string: '%s'", u.release);
1387 /* Note: this open-codes KERNEL_VERSION(): */
1388 rel = (rel << 8) | atoi(p);
1389 if (rel >= KERNEL_VERSION(1,0,0))
1391 while (*p >= '0' && *p <= '9')
1394 if (rel >= KERNEL_VERSION(0,1,0)) {
1395 /* "X.Y-something" means "X.Y.0" */
1399 error_msg_and_die("Bad OS release string: '%s'", u.release);
1407 * Initialization part of main() was eating much stack (~0.5k),
1408 * which was unused after init.
1409 * We can reuse it if we move init code into a separate function.
1411 * Don't want main() to inline us and defeat the reason
1412 * we have a separate function.
1414 static void ATTRIBUTE_NOINLINE
1415 init(int argc, char *argv[])
1421 struct sigaction sa;
1423 progname = argv[0] ? argv[0] : "strace";
1425 /* Make sure SIGCHLD has the default action so that waitpid
1426 definitely works without losing track of children. The user
1427 should not have given us a bogus state to inherit, but he might
1428 have. Arguably we should detect SIG_IGN here and pass it on
1429 to children, but probably noone really needs that. */
1430 signal(SIGCHLD, SIG_DFL);
1432 strace_tracer_pid = getpid();
1434 os_release = get_os_release();
1436 /* Allocate the initial tcbtab. */
1437 tcbtabsize = argc; /* Surely enough for all -p args. */
1438 tcbtab = xcalloc(tcbtabsize, sizeof(tcbtab[0]));
1439 tcp = xcalloc(tcbtabsize, sizeof(*tcp));
1440 for (tcbi = 0; tcbi < tcbtabsize; tcbi++)
1441 tcbtab[tcbi] = tcp++;
1443 shared_log = stderr;
1444 set_sortby(DEFAULT_SORTBY);
1445 set_personality(DEFAULT_PERSONALITY);
1446 qualify("trace=all");
1447 qualify("abbrev=all");
1448 qualify("verbose=all");
1449 #if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
1450 # error Bug in DEFAULT_QUAL_FLAGS
1452 qualify("signal=all");
1453 while ((c = getopt(argc, argv,
1454 "+b:cCdfFhiqrtTvVwxyz"
1455 #ifdef USE_LIBUNWIND
1459 "a:e:o:O:p:s:S:u:E:P:I:")) != EOF) {
1462 if (strcmp(optarg, "execve") != 0)
1463 error_msg_and_die("Syscall '%s' for -b isn't supported",
1465 detach_on_execve = 1;
1468 if (cflag == CFLAG_BOTH) {
1469 error_msg_and_die("-c and -C are mutually exclusive");
1471 cflag = CFLAG_ONLY_STATS;
1474 if (cflag == CFLAG_ONLY_STATS) {
1475 error_msg_and_die("-c and -C are mutually exclusive");
1483 daemonized_tracer = 1;
1502 /* fall through to tflag++ */
1510 count_wallclock = 1;
1519 qualify("abbrev=none");
1522 printf("%s -- version %s\n", PACKAGE_NAME, VERSION);
1526 not_failing_only = 1;
1529 acolumn = string_to_uint(optarg);
1531 error_opt_arg(c, optarg);
1537 outfname = xstrdup(optarg);
1540 i = string_to_uint(optarg);
1542 error_opt_arg(c, optarg);
1546 process_opt_p_list(optarg);
1549 pathtrace_select(optarg);
1552 i = string_to_uint(optarg);
1554 error_opt_arg(c, optarg);
1561 username = xstrdup(optarg);
1563 #ifdef USE_LIBUNWIND
1565 stack_trace_enabled = true;
1569 if (putenv(optarg) < 0)
1570 die_out_of_memory();
1573 opt_intr = string_to_uint(optarg);
1574 if (opt_intr <= 0 || opt_intr >= NUM_INTR_OPTS)
1575 error_opt_arg(c, optarg);
1583 /* argc -= optind; - no need, argc is not used below */
1585 acolumn_spaces = xmalloc(acolumn + 1);
1586 memset(acolumn_spaces, ' ', acolumn);
1587 acolumn_spaces[acolumn] = '\0';
1589 /* Must have PROG [ARGS], or -p PID. Not both. */
1590 if (!argv[0] == !nprocs)
1593 if (nprocs != 0 && daemonized_tracer) {
1594 error_msg_and_die("-D and -p are mutually exclusive");
1600 if (followfork >= 2 && cflag) {
1601 error_msg_and_die("(-c or -C) and -ff are mutually exclusive");
1604 if (count_wallclock && !cflag) {
1605 error_msg_and_die("-w must be given with (-c or -C)");
1608 if (cflag == CFLAG_ONLY_STATS) {
1610 error_msg("-%c has no effect with -c", 'i');
1611 #ifdef USE_LIBUNWIND
1612 if (stack_trace_enabled)
1613 error_msg("-%c has no effect with -c", 'k');
1616 error_msg("-%c has no effect with -c", 'r');
1618 error_msg("-%c has no effect with -c", 't');
1620 error_msg("-%c has no effect with -c", 'T');
1622 error_msg("-%c has no effect with -c", 'y');
1625 #ifdef USE_LIBUNWIND
1626 if (stack_trace_enabled)
1630 /* See if they want to run as another user. */
1631 if (username != NULL) {
1632 struct passwd *pent;
1634 if (getuid() != 0 || geteuid() != 0) {
1635 error_msg_and_die("You must be root to use the -u option");
1637 pent = getpwnam(username);
1639 error_msg_and_die("Cannot find user '%s'", username);
1641 run_uid = pent->pw_uid;
1642 run_gid = pent->pw_gid;
1650 ptrace_setoptions |= PTRACE_O_TRACECLONE |
1651 PTRACE_O_TRACEFORK |
1652 PTRACE_O_TRACEVFORK;
1654 error_msg("ptrace_setoptions = %#x", ptrace_setoptions);
1655 test_ptrace_seize();
1657 /* Check if they want to redirect the output. */
1659 /* See if they want to pipe the output. */
1660 if (outfname[0] == '|' || outfname[0] == '!') {
1662 * We can't do the <outfname>.PID funny business
1663 * when using popen, so prohibit it.
1665 if (followfork >= 2)
1666 error_msg_and_die("Piping the output and -ff are mutually exclusive");
1667 shared_log = strace_popen(outfname + 1);
1669 else if (followfork < 2)
1670 shared_log = strace_fopen(outfname);
1672 /* -ff without -o FILE is the same as single -f */
1673 if (followfork >= 2)
1677 if (!outfname || outfname[0] == '|' || outfname[0] == '!') {
1678 char *buf = xmalloc(BUFSIZ);
1679 setvbuf(shared_log, buf, _IOLBF, BUFSIZ);
1681 if (outfname && argv[0]) {
1683 opt_intr = INTR_NEVER;
1687 opt_intr = INTR_WHILE_WAIT;
1689 /* argv[0] -pPID -oFILE Default interactive setting
1690 * yes 0 0 INTR_WHILE_WAIT
1691 * no 1 0 INTR_WHILE_WAIT
1692 * yes 0 1 INTR_NEVER
1693 * no 1 1 INTR_WHILE_WAIT
1696 sigemptyset(&empty_set);
1697 sigemptyset(&blocked_set);
1699 /* startup_child() must be called before the signal handlers get
1700 * installed below as they are inherited into the spawned process.
1701 * Also we do not need to be protected by them as during interruption
1702 * in the startup_child() mode we kill the spawned process anyway.
1705 if (!NOMMU_SYSTEM || daemonized_tracer)
1706 hide_log_until_execve = 1;
1707 skip_one_b_execve = 1;
1708 startup_child(argv);
1711 sa.sa_handler = SIG_IGN;
1712 sigemptyset(&sa.sa_mask);
1714 sigaction(SIGTTOU, &sa, NULL); /* SIG_IGN */
1715 sigaction(SIGTTIN, &sa, NULL); /* SIG_IGN */
1716 if (opt_intr != INTR_ANYWHERE) {
1717 if (opt_intr == INTR_BLOCK_TSTP_TOO)
1718 sigaction(SIGTSTP, &sa, NULL); /* SIG_IGN */
1720 * In interactive mode (if no -o OUTFILE, or -p PID is used),
1721 * fatal signals are blocked while syscall stop is processed,
1722 * and acted on in between, when waiting for new syscall stops.
1723 * In non-interactive mode, signals are ignored.
1725 if (opt_intr == INTR_WHILE_WAIT) {
1726 sigaddset(&blocked_set, SIGHUP);
1727 sigaddset(&blocked_set, SIGINT);
1728 sigaddset(&blocked_set, SIGQUIT);
1729 sigaddset(&blocked_set, SIGPIPE);
1730 sigaddset(&blocked_set, SIGTERM);
1731 sa.sa_handler = interrupt;
1733 /* SIG_IGN, or set handler for these */
1734 sigaction(SIGHUP, &sa, NULL);
1735 sigaction(SIGINT, &sa, NULL);
1736 sigaction(SIGQUIT, &sa, NULL);
1737 sigaction(SIGPIPE, &sa, NULL);
1738 sigaction(SIGTERM, &sa, NULL);
1740 if (nprocs != 0 || daemonized_tracer)
1743 /* Do we want pids printed in our -o OUTFILE?
1744 * -ff: no (every pid has its own file); or
1745 * -f: yes (there can be more pids in the future); or
1746 * -p PID1,PID2: yes (there are already more than one pid)
1748 print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
1759 for (i = 0; i < tcbtabsize; i++) {
1760 struct tcb *tcp = tcbtab[i];
1761 if (tcp->pid == pid)
1775 /* 'interrupted' is a volatile object, fetch it only once */
1776 fatal_sig = interrupted;
1778 fatal_sig = SIGTERM;
1780 for (i = 0; i < tcbtabsize; i++) {
1785 error_msg("cleanup: looking at pid %u", tcp->pid);
1786 if (tcp->pid == strace_child) {
1787 kill(tcp->pid, SIGCONT);
1788 kill(tcp->pid, fatal_sig);
1793 call_summary(shared_log);
1803 print_debug_info(const int pid, int status)
1805 const unsigned int event = (unsigned int) status >> 16;
1806 char buf[sizeof("WIFEXITED,exitcode=%u") + sizeof(int)*3 /*paranoia:*/ + 16];
1807 char evbuf[sizeof(",EVENT_VFORK_DONE (%u)") + sizeof(int)*3 /*paranoia:*/ + 16];
1810 if (WIFSIGNALED(status))
1812 sprintf(buf, "WIFSIGNALED,%ssig=%s",
1813 WCOREDUMP(status) ? "core," : "",
1814 signame(WTERMSIG(status)));
1816 sprintf(buf, "WIFSIGNALED,sig=%s",
1817 signame(WTERMSIG(status)));
1819 if (WIFEXITED(status))
1820 sprintf(buf, "WIFEXITED,exitcode=%u", WEXITSTATUS(status));
1821 if (WIFSTOPPED(status))
1822 sprintf(buf, "WIFSTOPPED,sig=%s", signame(WSTOPSIG(status)));
1824 /* Should never be seen */
1825 if (WIFCONTINUED(status))
1826 strcpy(buf, "WIFCONTINUED");
1830 static const char *const event_names[] = {
1831 [PTRACE_EVENT_CLONE] = "CLONE",
1832 [PTRACE_EVENT_FORK] = "FORK",
1833 [PTRACE_EVENT_VFORK] = "VFORK",
1834 [PTRACE_EVENT_VFORK_DONE] = "VFORK_DONE",
1835 [PTRACE_EVENT_EXEC] = "EXEC",
1836 [PTRACE_EVENT_EXIT] = "EXIT",
1837 /* [PTRACE_EVENT_STOP (=128)] would make biggish array */
1839 const char *e = "??";
1840 if (event < ARRAY_SIZE(event_names))
1841 e = event_names[event];
1842 else if (event == PTRACE_EVENT_STOP)
1844 sprintf(evbuf, ",EVENT_%s (%u)", e, event);
1846 error_msg("[wait(0x%06x) = %u] %s%s", status, pid, buf, evbuf);
1850 maybe_allocate_tcb(const int pid, int status)
1852 if (!WIFSTOPPED(status)) {
1853 if (detach_on_execve && pid == strace_child) {
1854 /* example: strace -bexecve sh -c 'exec true' */
1859 * This can happen if we inherited an unknown child.
1860 * Example: (sleep 1 & exec strace true)
1862 error_msg("Exit of unknown pid %u ignored", pid);
1866 /* We assume it's a fork/vfork/clone child */
1867 struct tcb *tcp = alloctcb(pid);
1868 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1871 error_msg("Process %d attached", pid);
1874 /* This can happen if a clone call used
1875 * CLONE_PTRACE itself.
1877 ptrace(PTRACE_CONT, pid, (char *) 0, 0);
1878 error_msg("Stop of unknown pid %u seen, PTRACE_CONTed it", pid);
1884 maybe_switch_tcbs(struct tcb *tcp, const int pid)
1887 struct tcb *execve_thread;
1890 if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, (long) &old_pid) < 0)
1892 /* Avoid truncation in pid2tcb() param passing */
1893 if (old_pid <= 0 || old_pid == pid)
1895 if ((unsigned long) old_pid > UINT_MAX)
1897 execve_thread = pid2tcb(old_pid);
1898 /* It should be !NULL, but I feel paranoid */
1902 if (execve_thread->curcol != 0) {
1904 * One case we are here is -ff:
1905 * try "strace -oLOG -ff test/threaded_execve"
1907 fprintf(execve_thread->outf, " <pid changed to %d ...>\n", pid);
1908 /*execve_thread->curcol = 0; - no need, see code below */
1910 /* Swap output FILEs (needed for -ff) */
1911 fp = execve_thread->outf;
1912 execve_thread->outf = tcp->outf;
1914 /* And their column positions */
1915 execve_thread->curcol = tcp->curcol;
1917 /* Drop leader, but close execve'd thread outfile (if -ff) */
1919 /* Switch to the thread, reusing leader's outfile and pid */
1920 tcp = execve_thread;
1922 if (cflag != CFLAG_ONLY_STATS) {
1924 tprintf("+++ superseded by execve in pid %lu +++\n", old_pid);
1926 tcp->flags |= TCB_REPRINT;
1933 print_signalled(struct tcb *tcp, const int pid, int status)
1935 if (pid == strace_child) {
1936 exit_code = 0x100 | WTERMSIG(status);
1940 if (cflag != CFLAG_ONLY_STATS
1941 && (qual_flags[WTERMSIG(status)] & QUAL_SIGNAL)
1945 tprintf("+++ killed by %s %s+++\n",
1946 signame(WTERMSIG(status)),
1947 WCOREDUMP(status) ? "(core dumped) " : "");
1949 tprintf("+++ killed by %s +++\n",
1950 signame(WTERMSIG(status)));
1957 print_exited(struct tcb *tcp, const int pid, int status)
1959 if (pid == strace_child) {
1960 exit_code = WEXITSTATUS(status);
1964 if (cflag != CFLAG_ONLY_STATS &&
1967 tprintf("+++ exited with %d +++\n", WEXITSTATUS(status));
1973 print_stopped(struct tcb *tcp, const siginfo_t *si, const unsigned int sig)
1975 if (cflag != CFLAG_ONLY_STATS
1976 && !hide_log_until_execve
1977 && (qual_flags[sig] & QUAL_SIGNAL)
1981 tprintf("--- %s ", signame(sig));
1982 printsiginfo(si, verbose(tcp));
1985 tprintf("--- stopped by %s ---\n", signame(sig));
1991 startup_tcb(struct tcb *tcp)
1994 error_msg("pid %d has TCB_STARTUP, initializing it", tcp->pid);
1996 tcp->flags &= ~TCB_STARTUP;
2000 error_msg("setting opts 0x%x on pid %d",
2001 ptrace_setoptions, tcp->pid);
2002 if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, ptrace_setoptions) < 0) {
2003 if (errno != ESRCH) {
2004 /* Should never happen, really */
2005 perror_msg_and_die("PTRACE_SETOPTIONS");
2011 /* Returns true iff the main trace loop has to continue. */
2028 * Used to exit simply when nprocs hits zero, but in this testcase:
2029 * int main() { _exit(!!fork()); }
2030 * under strace -f, parent sometimes (rarely) manages
2031 * to exit before we see the first stop of the child,
2032 * and we are losing track of it:
2033 * 19923 clone(...) = 19924
2034 * 19923 exit_group(1) = ?
2035 * 19923 +++ exited with 1 +++
2036 * Exiting only when wait() returns ECHILD works better.
2038 if (popen_pid != 0) {
2039 /* However, if -o|logger is in use, we can't do that.
2040 * Can work around that by double-forking the logger,
2041 * but that loses the ability to wait for its completion
2042 * on exit. Oh well...
2049 sigprocmask(SIG_SETMASK, &empty_set, NULL);
2050 pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
2053 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
2056 if (wait_errno == EINTR)
2058 if (nprocs == 0 && wait_errno == ECHILD)
2061 * If nprocs > 0, ECHILD is not expected,
2062 * treat it as any other error here:
2065 perror_msg_and_die("wait4(__WALL)");
2068 if (pid == popen_pid) {
2069 if (!WIFSTOPPED(status))
2075 print_debug_info(pid, status);
2077 /* Look up 'pid' in our table. */
2081 tcp = maybe_allocate_tcb(pid, status);
2086 if (WIFSTOPPED(status))
2091 event = (unsigned int) status >> 16;
2093 if (event == PTRACE_EVENT_EXEC) {
2095 * Under Linux, execve changes pid to thread leader's pid,
2096 * and we see this changed pid on EVENT_EXEC and later,
2097 * execve sysexit. Leader "disappears" without exit
2098 * notification. Let user know that, drop leader's tcb,
2099 * and fix up pid in execve thread's tcb.
2100 * Effectively, execve thread's tcb replaces leader's tcb.
2102 * BTW, leader is 'stuck undead' (doesn't report WIFEXITED
2103 * on exit syscall) in multithreaded programs exactly
2104 * in order to handle this case.
2106 * PTRACE_GETEVENTMSG returns old pid starting from Linux 3.0.
2107 * On 2.6 and earlier, it can return garbage.
2109 if (os_release >= KERNEL_VERSION(3,0,0))
2110 tcp = maybe_switch_tcbs(tcp, pid);
2112 if (detach_on_execve && !skip_one_b_execve) {
2113 detach(tcp); /* do "-b execve" thingy */
2116 skip_one_b_execve = 0;
2119 /* Set current output file */
2123 tv_sub(&tcp->dtime, &ru.ru_stime, &tcp->stime);
2124 tcp->stime = ru.ru_stime;
2127 if (WIFSIGNALED(status)) {
2128 print_signalled(tcp, pid, status);
2133 if (WIFEXITED(status)) {
2134 print_exited(tcp, pid, status);
2139 if (!WIFSTOPPED(status)) {
2141 * Neither signalled, exited or stopped.
2142 * How could that be?
2144 error_msg("pid %u not stopped!", pid);
2149 /* Is this the very first time we see this tracee stopped? */
2150 if (tcp->flags & TCB_STARTUP) {
2152 if (get_scno(tcp) == 1)
2153 tcp->s_prev_ent = tcp->s_ent;
2156 sig = WSTOPSIG(status);
2161 if (event == PTRACE_EVENT_STOP) {
2163 * PTRACE_INTERRUPT-stop or group-stop.
2164 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
2176 goto restart_tracee_with_sig_0;
2180 * Is this post-attach SIGSTOP?
2181 * Interestingly, the process may stop
2182 * with STOPSIG equal to some other signal
2183 * than SIGSTOP if we happend to attach
2184 * just before the process takes a signal.
2186 if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
2188 error_msg("ignored SIGSTOP on pid %d", tcp->pid);
2189 tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
2190 goto restart_tracee_with_sig_0;
2193 if (sig != syscall_trap_sig) {
2197 * True if tracee is stopped by signal
2198 * (as opposed to "tracee received signal").
2199 * TODO: shouldn't we check for errno == EINVAL too?
2200 * We can get ESRCH instead, you know...
2202 stopped = ptrace(PTRACE_GETSIGINFO, pid, 0, (long) &si) < 0;
2206 print_stopped(tcp, stopped ? NULL : &si, sig);
2209 /* It's signal-delivery-stop. Inject the signal */
2210 goto restart_tracee;
2212 /* It's group-stop */
2215 * This ends ptrace-stop, but does *not* end group-stop.
2216 * This makes stopping signals work properly on straced process
2217 * (that is, process really stops. It used to continue to run).
2219 if (ptrace_restart(PTRACE_LISTEN, tcp, 0) < 0) {
2220 /* Note: ptrace_restart emitted error message */
2226 /* We don't have PTRACE_LISTEN support... */
2227 goto restart_tracee;
2230 /* We handled quick cases, we are permitted to interrupt now. */
2235 * This should be syscall entry or exit.
2238 if (trace_syscall(tcp) < 0) {
2240 * ptrace() failed in trace_syscall().
2241 * Likely a result of process disappearing mid-flight.
2242 * Observed case: exit_group() or SIGKILL terminating
2243 * all processes in thread group.
2244 * We assume that ptrace error was caused by process death.
2245 * We used to detach(tcp) here, but since we no longer
2246 * implement "detach before death" policy/hack,
2247 * we can let this process to report its death to us
2248 * normally, via WIFEXITED or WIFSIGNALED wait status.
2253 restart_tracee_with_sig_0:
2257 if (ptrace_restart(PTRACE_SYSCALL, tcp, sig) < 0) {
2258 /* Note: ptrace_restart emitted error message */
2267 main(int argc, char *argv[])
2276 if (shared_log != stderr)
2279 while (waitpid(popen_pid, NULL, 0) < 0 && errno == EINTR)
2282 if (exit_code > 0xff) {
2283 /* Avoid potential core file clobbering. */
2284 struct_rlimit rlim = {0, 0};
2285 set_rlimit(RLIMIT_CORE, &rlim);
2287 /* Child was killed by a signal, mimic that. */
2289 signal(exit_code, SIG_DFL);
2291 /* Paranoia - what if this signal is not fatal?
2292 Exit with 128 + signo then. */