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>
36 #include <sys/resource.h>
42 #include <sys/utsname.h>
44 # include <sys/prctl.h>
48 #include "printsiginfo.h"
50 /* In some libc, these aren't declared. Do it ourself: */
51 extern char **environ;
56 /* if this is true do the stack trace for every system call */
57 bool stack_trace_enabled = false;
60 #if defined __NR_tkill
61 # define my_tkill(tid, sig) syscall(__NR_tkill, (tid), (sig))
63 /* kill() may choose arbitrarily the target task of the process group
64 while we later wait on a that specific TID. PID process waits become
65 TID task specific waits for a process under ptrace(2). */
66 # warning "tkill(2) not available, risk of strace hangs!"
67 # define my_tkill(tid, sig) kill((tid), (sig))
70 /* Glue for systems without a MMU that cannot provide fork() */
71 #if !defined(HAVE_FORK)
73 # define NOMMU_SYSTEM 1
76 # define fork() vfork()
79 const unsigned int syscall_trap_sig = SIGTRAP | 0x80;
81 cflag_t cflag = CFLAG_NONE;
82 unsigned int followfork = 0;
83 unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC;
84 unsigned int xflag = 0;
88 bool count_wallclock = 0;
89 unsigned int qflag = 0;
90 static unsigned int tflag = 0;
91 static bool rflag = 0;
92 static bool print_pid_pfx = 0;
97 INTR_ANYWHERE = 1, /* don't block/ignore any signals */
98 INTR_WHILE_WAIT = 2, /* block fatal signals while decoding syscall. default */
99 INTR_NEVER = 3, /* block fatal signals. default if '-o FILE PROG' */
100 INTR_BLOCK_TSTP_TOO = 4, /* block fatal signals and SIGTSTP (^Z) */
104 /* We play with signal mask only if this mode is active: */
105 #define interactive (opt_intr == INTR_WHILE_WAIT)
108 * daemonized_tracer supports -D option.
109 * With this option, strace forks twice.
110 * Unlike normal case, with -D *grandparent* process exec's,
111 * becoming a traced process. Child exits (this prevents traced process
112 * from having children it doesn't expect to have), and grandchild
113 * attaches to grandparent similarly to strace -p PID.
114 * This allows for more transparent interaction in cases
115 * when process and its parent are communicating via signals,
116 * wait() etc. Without -D, strace process gets lodged in between,
117 * disrupting parent<->child link.
119 static bool daemonized_tracer = 0;
122 static int post_attach_sigstop = TCB_IGNORE_ONE_SIGSTOP;
123 # define use_seize (post_attach_sigstop == 0)
125 # define post_attach_sigstop TCB_IGNORE_ONE_SIGSTOP
129 /* Sometimes we want to print only succeeding syscalls. */
130 bool not_failing_only = 0;
132 /* Show path associated with fd arguments */
133 unsigned int show_fd_path = 0;
135 static bool detach_on_execve = 0;
136 /* Are we "strace PROG" and need to skip detach on first execve? */
137 static bool skip_one_b_execve = 0;
138 /* Are we "strace PROG" and need to hide everything until execve? */
139 bool hide_log_until_execve = 0;
141 static int exit_code = 0;
142 static int strace_child = 0;
143 static int strace_tracer_pid = 0;
145 static char *username = NULL;
146 static uid_t run_uid;
147 static gid_t run_gid;
149 unsigned int max_strlen = DEFAULT_STRLEN;
150 static int acolumn = DEFAULT_ACOLUMN;
151 static char *acolumn_spaces;
153 static char *outfname = NULL;
154 /* If -ff, points to stderr. Else, it's our common output log */
155 static FILE *shared_log;
157 struct tcb *printing_tcp = NULL;
158 static struct tcb *current_tcp;
160 static struct tcb **tcbtab;
161 static unsigned int nprocs, tcbtabsize;
162 static const char *progname;
164 unsigned os_release; /* generated from uname()'s u.release */
166 static void detach(struct tcb *tcp);
167 static void cleanup(void);
168 static void interrupt(int sig);
169 static sigset_t empty_set, blocked_set;
171 #ifdef HAVE_SIG_ATOMIC_T
172 static volatile sig_atomic_t interrupted;
174 static volatile int interrupted;
177 #ifndef HAVE_STRERROR
179 #if !HAVE_DECL_SYS_ERRLIST
181 extern char *sys_errlist[];
187 static char buf[sizeof("Unknown error %d") + sizeof(int)*3];
189 if (err_no < 1 || err_no >= sys_nerr) {
190 sprintf(buf, "Unknown error %d", err_no);
193 return sys_errlist[err_no];
196 #endif /* HAVE_STERRROR */
202 usage: strace [-CdffhiqrtttTvVwxxy] [-I n] [-e expr]...\n\
203 [-a column] [-o file] [-s strsize] [-P path]...\n\
204 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
205 or: strace -c[dfw] [-I n] [-e expr]... [-O overhead] [-S sortby]\n\
206 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
209 -a column alignment COLUMN for printing syscall results (default %d)\n\
210 -i print instruction pointer at time of syscall\n\
211 -o file send trace output to FILE instead of stderr\n\
212 -q suppress messages about attaching, detaching, etc.\n\
213 -r print relative timestamp\n\
214 -s strsize limit length of print strings to STRSIZE chars (default %d)\n\
215 -t print absolute timestamp\n\
216 -tt print absolute timestamp with usecs\n\
217 -T print time spent in each syscall\n\
218 -x print non-ascii strings in hex\n\
219 -xx print all strings in hex\n\
220 -y print paths associated with file descriptor arguments\n\
221 -yy print ip:port pairs associated with socket file descriptors\n\
224 -c count time, calls, and errors for each syscall and report summary\n\
225 -C like -c but also print regular output\n\
226 -O overhead set overhead for tracing syscalls to OVERHEAD usecs\n\
227 -S sortby sort syscall counts by: time, calls, name, nothing (default %s)\n\
228 -w summarise syscall latency (default is system time)\n\
231 -e expr a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
232 options: trace, abbrev, verbose, raw, signal, read, write\n\
233 -P path trace accesses to path\n\
236 -b execve detach on execve syscall\n\
237 -D run tracer process as a detached grandchild, not as parent\n\
239 -ff follow forks with output into separate files\n\
241 1: no signals are blocked\n\
242 2: fatal signals are blocked while decoding syscall (default)\n\
243 3: fatal signals are always blocked (default if '-o FILE PROG')\n\
244 4: fatal signals and SIGTSTP (^Z) are always blocked\n\
245 (useful to make 'strace -o FILE PROG' not stop on ^Z)\n\
248 -E var remove var from the environment for command\n\
249 -E var=val put var=val in the environment for command\n\
250 -p pid trace process with process id PID, may be repeated\n\
251 -u username run command as username handling setuid and/or setgid\n\
254 -d enable debug output to stderr\n\
255 -v verbose mode: print unabbreviated argv, stat, termios, etc. args\n\
256 -h print help message\n\
260 " -k obtain stack trace between each syscall (experimental)\n\
263 /* ancient, no one should use it
264 -F -- attempt to follow vforks (deprecated, use -f)\n\
266 /* this is broken, so don't document it
267 -z -- print only succeeding syscalls\n\
269 , DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
273 static void ATTRIBUTE_NORETURN
276 if (strace_tracer_pid == getpid()) {
283 static void verror_msg(int err_no, const char *fmt, va_list p)
289 /* We want to print entire message with single fprintf to ensure
290 * message integrity if stderr is shared with other programs.
291 * Thus we use vasprintf + single fprintf.
294 if (vasprintf(&msg, fmt, p) >= 0) {
296 fprintf(stderr, "%s: %s: %s\n", progname, msg, strerror(err_no));
298 fprintf(stderr, "%s: %s\n", progname, msg);
301 /* malloc in vasprintf failed, try it without malloc */
302 fprintf(stderr, "%s: ", progname);
303 vfprintf(stderr, fmt, p);
305 fprintf(stderr, ": %s\n", strerror(err_no));
309 /* We don't switch stderr to buffered, thus fprintf(stderr)
310 * always flushes its output and this is not necessary: */
311 /* fflush(stderr); */
314 void error_msg(const char *fmt, ...)
318 verror_msg(0, fmt, p);
322 void error_msg_and_die(const char *fmt, ...)
326 verror_msg(0, fmt, p);
330 void error_msg_and_help(const char *fmt, ...)
335 verror_msg(0, fmt, p);
337 fprintf(stderr, "Try '%s -h' for more information.\n", progname);
341 void perror_msg(const char *fmt, ...)
345 verror_msg(errno, fmt, p);
349 void perror_msg_and_die(const char *fmt, ...)
353 verror_msg(errno, fmt, p);
358 error_opt_arg(int opt, const char *arg)
360 error_msg_and_help("invalid -%c argument: '%s'", opt, arg);
365 ptrace_attach_or_seize(int pid)
369 return ptrace(PTRACE_ATTACH, pid, 0L, 0L);
370 r = ptrace(PTRACE_SEIZE, pid, 0L, (unsigned long) ptrace_setoptions);
373 r = ptrace(PTRACE_INTERRUPT, pid, 0L, 0L);
377 # define ptrace_attach_or_seize(pid) ptrace(PTRACE_ATTACH, (pid), 0, 0)
381 * Used when we want to unblock stopped traced process.
382 * Should be only used with PTRACE_CONT, PTRACE_DETACH and PTRACE_SYSCALL.
383 * Returns 0 on success or if error was ESRCH
384 * (presumably process was killed while we talk to it).
385 * Otherwise prints error message and returns -1.
388 ptrace_restart(int op, struct tcb *tcp, int sig)
394 ptrace(op, tcp->pid, (void *) 0, (long) sig);
400 if (op == PTRACE_CONT)
402 if (op == PTRACE_DETACH)
405 if (op == PTRACE_LISTEN)
409 * Why curcol != 0? Otherwise sometimes we get this:
411 * 10252 kill(10253, SIGKILL) = 0
412 * <ptrace(SYSCALL,10252):No such process>10253 ...next decode...
414 * 10252 died after we retrieved syscall exit data,
415 * but before we tried to restart it. Log looks ugly.
417 if (current_tcp && current_tcp->curcol != 0) {
418 tprintf(" <ptrace(%s):%s>\n", msg, strerror(err));
424 perror_msg("ptrace(PTRACE_%s,pid:%d,sig:%d)", msg, tcp->pid, sig);
429 set_cloexec_flag(int fd)
433 flags = fcntl(fd, F_GETFD);
435 /* Can happen only if fd is bad.
436 * Should never happen: if it does, we have a bug
437 * in the caller. Therefore we just abort
438 * instead of propagating the error.
440 perror_msg_and_die("fcntl(%d, F_GETFD)", fd);
443 newflags = flags | FD_CLOEXEC;
444 if (flags == newflags)
447 fcntl(fd, F_SETFD, newflags); /* never fails */
450 static void kill_save_errno(pid_t pid, int sig)
452 int saved_errno = errno;
454 (void) kill(pid, sig);
459 * When strace is setuid executable, we have to swap uids
460 * before and after filesystem and process management operations.
465 int euid = geteuid(), uid = getuid();
467 if (euid != uid && setreuid(euid, uid) < 0) {
468 perror_msg_and_die("setreuid");
472 #ifdef _LARGEFILE64_SOURCE
474 # define fopen_for_output fopen64
476 # define fopen_for_output fopen
478 # define struct_stat struct stat64
479 # define stat_file stat64
480 # define struct_dirent struct dirent64
481 # define read_dir readdir64
482 # define struct_rlimit struct rlimit64
483 # define set_rlimit setrlimit64
485 # define fopen_for_output fopen
486 # define struct_stat struct stat
487 # define stat_file stat
488 # define struct_dirent struct dirent
489 # define read_dir readdir
490 # define struct_rlimit struct rlimit
491 # define set_rlimit setrlimit
495 strace_fopen(const char *path)
500 fp = fopen_for_output(path, "w");
502 perror_msg_and_die("Can't fopen '%s'", path);
504 set_cloexec_flag(fileno(fp));
508 static int popen_pid = 0;
511 # define _PATH_BSHELL "/bin/sh"
515 * We cannot use standard popen(3) here because we have to distinguish
516 * popen child process from other processes we trace, and standard popen(3)
517 * does not export its child's pid.
520 strace_popen(const char *command)
528 perror_msg_and_die("pipe");
530 set_cloexec_flag(fds[1]); /* never fails */
534 perror_msg_and_die("vfork");
541 perror_msg_and_die("dup2");
544 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
545 perror_msg_and_die("Can't execute '%s'", _PATH_BSHELL);
552 fp = fdopen(fds[1], "w");
559 tprintf(const char *fmt, ...)
565 int n = strace_vfprintf(current_tcp->outf, fmt, args);
567 if (current_tcp->outf != stderr)
568 perror_msg("%s", outfname);
570 current_tcp->curcol += n;
575 #ifndef HAVE_FPUTS_UNLOCKED
576 # define fputs_unlocked fputs
580 tprints(const char *str)
583 int n = fputs_unlocked(str, current_tcp->outf);
585 current_tcp->curcol += strlen(str);
588 if (current_tcp->outf != stderr)
589 perror_msg("%s", outfname);
597 current_tcp->curcol = 0;
598 fflush(current_tcp->outf);
601 printing_tcp->curcol = 0;
607 printleader(struct tcb *tcp)
609 /* If -ff, "previous tcb we printed" is always the same as current,
610 * because we have per-tcb output files.
616 current_tcp = printing_tcp;
617 if (printing_tcp->curcol != 0 && (followfork < 2 || printing_tcp == tcp)) {
619 * case 1: we have a shared log (i.e. not -ff), and last line
620 * wasn't finished (same or different tcb, doesn't matter).
621 * case 2: split log, we are the same tcb, but our last line
622 * didn't finish ("SIGKILL nuked us after syscall entry" etc).
624 tprints(" <unfinished ...>\n");
625 printing_tcp->curcol = 0;
631 current_tcp->curcol = 0;
634 tprintf("%-5d ", tcp->pid);
635 else if (nprocs > 1 && !outfname)
636 tprintf("[pid %5u] ", tcp->pid);
639 char str[sizeof("HH:MM:SS")];
640 struct timeval tv, dtv;
641 static struct timeval otv;
643 gettimeofday(&tv, NULL);
647 tv_sub(&dtv, &tv, &otv);
648 tprintf("%6ld.%06ld ",
649 (long) dtv.tv_sec, (long) dtv.tv_usec);
652 else if (tflag > 2) {
653 tprintf("%ld.%06ld ",
654 (long) tv.tv_sec, (long) tv.tv_usec);
657 time_t local = tv.tv_sec;
658 strftime(str, sizeof(str), "%T", localtime(&local));
660 tprintf("%s.%06ld ", str, (long) tv.tv_usec);
672 if (current_tcp->curcol < acolumn)
673 tprints(acolumn_spaces + current_tcp->curcol);
676 /* Should be only called directly *after successful attach* to a tracee.
677 * Otherwise, "strace -oFILE -ff -p<nonexistant_pid>"
678 * may create bogus empty FILE.<nonexistant_pid>, and then die.
681 newoutf(struct tcb *tcp)
683 tcp->outf = shared_log; /* if not -ff mode, the same file is for all */
684 if (followfork >= 2) {
685 char name[520 + sizeof(int) * 3];
686 sprintf(name, "%.512s.%u", outfname, tcp->pid);
687 tcp->outf = strace_fopen(name);
694 /* Allocate some more TCBs and expand the table.
695 We don't want to relocate the TCBs because our
696 callers have pointers and it would be a pain.
697 So tcbtab is a table of pointers. Since we never
698 free the TCBs, we allocate a single chunk of many. */
699 unsigned int i = tcbtabsize;
700 struct tcb *newtcbs = xcalloc(tcbtabsize, sizeof(newtcbs[0]));
701 struct tcb **newtab = xreallocarray(tcbtab, tcbtabsize * 2,
705 while (i < tcbtabsize)
706 tcbtab[i++] = newtcbs++;
715 if (nprocs == tcbtabsize)
718 for (i = 0; i < tcbtabsize; i++) {
721 memset(tcp, 0, sizeof(*tcp));
723 #if SUPPORTED_PERSONALITIES > 1
724 tcp->currpers = current_personality;
728 if (stack_trace_enabled)
729 unwind_tcb_init(tcp);
734 error_msg("new tcb for pid %d, active tcbs:%d",
739 error_msg_and_die("bug in alloctcb");
743 droptcb(struct tcb *tcp)
749 if (stack_trace_enabled) {
756 error_msg("dropped tcb for pid %d, %d remain",
760 if (followfork >= 2) {
761 if (tcp->curcol != 0)
762 fprintf(tcp->outf, " <detached ...>\n");
765 if (printing_tcp == tcp && tcp->curcol != 0)
766 fprintf(tcp->outf, " <detached ...>\n");
771 if (current_tcp == tcp)
773 if (printing_tcp == tcp)
776 memset(tcp, 0, sizeof(*tcp));
779 /* Detach traced process.
780 * Never call DETACH twice on the same process as both unattached and
781 * attached-unstopped processes give the same ESRCH. For unattached process we
782 * would SIGSTOP it and wait for its SIGSTOP notification forever.
785 detach(struct tcb *tcp)
791 * Linux wrongly insists the child be stopped
792 * before detaching. Arghh. We go through hoops
793 * to make a clean break of things.
796 # undef PTRACE_DETACH
797 # define PTRACE_DETACH PTRACE_SUNDETACH
800 if (!(tcp->flags & TCB_ATTACHED))
803 /* We attached but possibly didn't see the expected SIGSTOP.
804 * We must catch exactly one as otherwise the detached process
805 * would be left stopped (process state T).
807 if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
810 error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
812 /* On a clear day, you can see forever. */
815 if (errno != ESRCH) {
816 /* Shouldn't happen. */
817 perror_msg("detach: ptrace(PTRACE_DETACH,%u)", tcp->pid);
820 /* ESRCH: process is either not stopped or doesn't exist. */
821 if (my_tkill(tcp->pid, 0) < 0) {
823 /* Shouldn't happen. */
824 perror_msg("detach: tkill(%u,0)", tcp->pid);
825 /* else: process doesn't exist. */
828 /* Process is not stopped, need to stop it. */
831 * With SEIZE, tracee can be in group-stop already.
832 * In this state sending it another SIGSTOP does nothing.
833 * Need to use INTERRUPT.
834 * Testcase: trying to ^C a "strace -p <stopped_process>".
836 error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
840 perror_msg("detach: ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
843 error = my_tkill(tcp->pid, SIGSTOP);
847 perror_msg("detach: tkill(%u,SIGSTOP)", tcp->pid);
849 /* Either process doesn't exist, or some weird error. */
853 /* We end up here in three cases:
854 * 1. We sent PTRACE_INTERRUPT (use_seize case)
855 * 2. We sent SIGSTOP (!use_seize)
856 * 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
860 if (waitpid(tcp->pid, &status, __WALL) < 0) {
864 * if (errno == ECHILD) break;
865 * ^^^ WRONG! We expect this PID to exist,
866 * and want to emit a message otherwise:
868 perror_msg("detach: waitpid(%u)", tcp->pid);
871 if (!WIFSTOPPED(status)) {
873 * Tracee exited or was killed by signal.
874 * We shouldn't normally reach this place:
875 * we don't want to consume exit status.
876 * Consider "strace -p PID" being ^C-ed:
877 * we want merely to detach from PID.
879 * However, we _can_ end up here if tracee
884 sig = WSTOPSIG(status);
886 error_msg("detach wait: event:%d sig:%d",
887 (unsigned)status >> 16, sig);
889 unsigned event = (unsigned)status >> 16;
890 if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
892 * sig == SIGTRAP: PTRACE_INTERRUPT stop.
893 * sig == other: process was already stopped
894 * with this stopping sig (see tests/detach-stopped).
895 * Looks like re-injecting this sig is not necessary
896 * in DETACH for the tracee to remain stopped.
901 * PTRACE_INTERRUPT is not guaranteed to produce
902 * the above event if other ptrace-stop is pending.
903 * See tests/detach-sleeping testcase:
904 * strace got SIGINT while tracee is sleeping.
905 * We sent PTRACE_INTERRUPT.
906 * We see syscall exit, not PTRACE_INTERRUPT stop.
907 * We won't get PTRACE_INTERRUPT stop
908 * if we would CONT now. Need to DETACH.
910 if (sig == syscall_trap_sig)
912 /* else: not sure in which case we can be here.
913 * Signal stop? Inject it while detaching.
915 ptrace_restart(PTRACE_DETACH, tcp, sig);
918 /* Note: this check has to be after use_seize check */
919 /* (else, in use_seize case SIGSTOP will be mistreated) */
920 if (sig == SIGSTOP) {
921 /* Detach, suppressing SIGSTOP */
922 ptrace_restart(PTRACE_DETACH, tcp, 0);
925 if (sig == syscall_trap_sig)
927 /* Can't detach just yet, may need to wait for SIGSTOP */
928 error = ptrace_restart(PTRACE_CONT, tcp, sig);
930 /* Should not happen.
931 * Note: ptrace_restart returns 0 on ESRCH, so it's not it.
932 * ptrace_restart already emitted error message.
939 if (!qflag && (tcp->flags & TCB_ATTACHED))
940 error_msg("Process %u detached", tcp->pid);
946 process_opt_p_list(char *opt)
950 * We accept -p PID,PID; -p "`pidof PROG`"; -p "`pgrep PROG`".
951 * pidof uses space as delim, pgrep uses newline. :(
954 char *delim = opt + strcspn(opt, ", \n\t");
958 pid = string_to_uint(opt);
960 error_msg_and_die("Invalid process id: '%s'", opt);
962 if (pid == strace_tracer_pid) {
963 error_msg_and_die("I'm sorry, I can't let you do that, Dave.");
976 pid_t parent_pid = strace_tracer_pid;
981 * Block user interruptions as we would leave the traced
982 * process stopped (process state T) if we would terminate in
983 * between PTRACE_ATTACH and wait4() on SIGSTOP.
984 * We rely on cleanup() from this point on.
987 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
989 if (daemonized_tracer) {
992 perror_msg_and_die("fork");
994 if (pid) { /* parent */
996 * Wait for grandchild to attach to straced process
997 * (grandparent). Grandchild SIGKILLs us after it attached.
998 * Grandparent's wait() is unblocked by our death,
999 * it proceeds to exec the straced program.
1002 _exit(0); /* paranoia */
1005 /* We will be the tracer process. Remember our new pid: */
1006 strace_tracer_pid = getpid();
1009 for (tcbi = 0; tcbi < tcbtabsize; tcbi++) {
1015 /* Is this a process we should attach to, but not yet attached? */
1016 if (tcp->flags & TCB_ATTACHED)
1017 continue; /* no, we already attached it */
1019 if (tcp->pid == parent_pid || tcp->pid == strace_tracer_pid) {
1021 perror_msg("attach: %d", tcp->pid);
1025 if (followfork && tcp->pid != strace_child) {
1026 char procdir[sizeof("/proc/%d/task") + sizeof(int) * 3];
1029 sprintf(procdir, "/proc/%d/task", tcp->pid);
1030 dir = opendir(procdir);
1032 unsigned int ntid = 0, nerr = 0;
1035 while ((de = read_dir(dir)) != NULL) {
1036 struct tcb *cur_tcp;
1039 if (de->d_fileno == 0)
1041 /* we trust /proc filesystem */
1042 tid = atoi(de->d_name);
1046 if (ptrace_attach_or_seize(tid) < 0) {
1049 error_msg("attach to pid %d failed", tid);
1053 error_msg("attach to pid %d succeeded", tid);
1055 if (tid != tcp->pid)
1056 cur_tcp = alloctcb(tid);
1057 cur_tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1062 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1065 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
1069 perror_msg("attach: ptrace(PTRACE_ATTACH, ...)");
1075 error_msg("Process %u attached"
1079 error_msg("Process %u attached",
1082 if (!(tcp->flags & TCB_ATTACHED)) {
1083 /* -p PID, we failed to attach to PID itself
1084 * but did attach to some of its sibling threads.
1090 } /* if (opendir worked) */
1092 if (ptrace_attach_or_seize(tcp->pid) < 0) {
1093 perror_msg("attach: ptrace(PTRACE_ATTACH, ...)");
1097 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1100 error_msg("attach to pid %d (main) succeeded", tcp->pid);
1103 error_msg("Process %u attached", tcp->pid);
1104 } /* for each tcbtab[] */
1106 if (daemonized_tracer) {
1108 * Make parent go away.
1109 * Also makes grandparent's wait() unblock.
1111 kill(parent_pid, SIGKILL);
1117 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1120 /* Stack-o-phobic exec helper, in the hope to work around
1121 * NOMMU + "daemonized tracer" difficulty.
1123 struct exec_params {
1130 static struct exec_params params_for_tracee;
1132 static void ATTRIBUTE_NOINLINE ATTRIBUTE_NORETURN
1135 struct exec_params *params = ¶ms_for_tracee;
1137 if (params->fd_to_close >= 0)
1138 close(params->fd_to_close);
1139 if (!daemonized_tracer && !use_seize) {
1140 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0) {
1141 perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
1145 if (username != NULL) {
1147 * It is important to set groups before we
1148 * lose privileges on setuid.
1150 if (initgroups(username, run_gid) < 0) {
1151 perror_msg_and_die("initgroups");
1153 if (setregid(run_gid, params->run_egid) < 0) {
1154 perror_msg_and_die("setregid");
1156 if (setreuid(run_uid, params->run_euid) < 0) {
1157 perror_msg_and_die("setreuid");
1160 else if (geteuid() != 0)
1161 if (setreuid(run_uid, run_uid) < 0) {
1162 perror_msg_and_die("setreuid");
1165 if (!daemonized_tracer) {
1167 * Induce a ptrace stop. Tracer (our parent)
1168 * will resume us with PTRACE_SYSCALL and display
1169 * the immediately following execve syscall.
1170 * Can't do this on NOMMU systems, we are after
1171 * vfork: parent is blocked, stopping would deadlock.
1174 kill(getpid(), SIGSTOP);
1177 /* we depend on SIGCHLD set to SIG_DFL by init code */
1178 /* if it happens to be SIG_IGN'ed, wait won't block */
1183 execv(params->pathname, params->argv);
1184 perror_msg_and_die("exec");
1188 open_dummy_desc(void)
1193 perror_msg_and_die("pipe");
1199 startup_child(char **argv)
1201 struct_stat statbuf;
1202 const char *filename;
1203 size_t filename_len;
1204 char pathname[PATH_MAX];
1209 filename_len = strlen(filename);
1211 if (filename_len > sizeof(pathname) - 1) {
1212 errno = ENAMETOOLONG;
1213 perror_msg_and_die("exec");
1215 if (strchr(filename, '/')) {
1216 strcpy(pathname, filename);
1218 #ifdef USE_DEBUGGING_EXEC
1220 * Debuggers customarily check the current directory
1221 * first regardless of the path but doing that gives
1222 * security geeks a panic attack.
1224 else if (stat_file(filename, &statbuf) == 0)
1225 strcpy(pathname, filename);
1226 #endif /* USE_DEBUGGING_EXEC */
1231 for (path = getenv("PATH"); path && *path; path += m) {
1232 const char *colon = strchr(path, ':');
1238 m = n = strlen(path);
1240 if (!getcwd(pathname, PATH_MAX))
1242 len = strlen(pathname);
1244 else if (n > sizeof pathname - 1)
1247 strncpy(pathname, path, n);
1250 if (len && pathname[len - 1] != '/')
1251 pathname[len++] = '/';
1252 if (filename_len + len > sizeof(pathname) - 1)
1254 strcpy(pathname + len, filename);
1255 if (stat_file(pathname, &statbuf) == 0 &&
1256 /* Accept only regular files
1257 with some execute bits set.
1258 XXX not perfect, might still fail */
1259 S_ISREG(statbuf.st_mode) &&
1260 (statbuf.st_mode & 0111))
1263 if (!path || !*path)
1266 if (stat_file(pathname, &statbuf) < 0) {
1267 perror_msg_and_die("Can't stat '%s'", filename);
1270 params_for_tracee.fd_to_close = (shared_log != stderr) ? fileno(shared_log) : -1;
1271 params_for_tracee.run_euid = (statbuf.st_mode & S_ISUID) ? statbuf.st_uid : run_uid;
1272 params_for_tracee.run_egid = (statbuf.st_mode & S_ISGID) ? statbuf.st_gid : run_gid;
1273 params_for_tracee.argv = argv;
1275 * On NOMMU, can be safely freed only after execve in tracee.
1276 * It's hard to know when that happens, so we just leak it.
1278 params_for_tracee.pathname = NOMMU_SYSTEM ? xstrdup(pathname) : pathname;
1280 #if defined HAVE_PRCTL && defined PR_SET_PTRACER && defined PR_SET_PTRACER_ANY
1281 if (daemonized_tracer)
1282 prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
1287 perror_msg_and_die("fork");
1289 if ((pid != 0 && daemonized_tracer)
1290 || (pid == 0 && !daemonized_tracer)
1292 /* We are to become the tracee. Two cases:
1294 * not -D: we are child
1299 /* We are the tracer */
1301 if (!daemonized_tracer) {
1304 /* child did PTRACE_TRACEME, nothing to do in parent */
1306 if (!NOMMU_SYSTEM) {
1307 /* Wait until child stopped itself */
1309 while (waitpid(pid, &status, WSTOPPED) < 0) {
1312 perror_msg_and_die("waitpid");
1314 if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGSTOP) {
1315 kill_save_errno(pid, SIGKILL);
1316 perror_msg_and_die("Unexpected wait status %x", status);
1319 /* Else: NOMMU case, we have no way to sync.
1320 * Just attach to it as soon as possible.
1321 * This means that we may miss a few first syscalls...
1324 if (ptrace_attach_or_seize(pid)) {
1325 kill_save_errno(pid, SIGKILL);
1326 perror_msg_and_die("Can't attach to %d", pid);
1331 tcp = alloctcb(pid);
1333 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1335 tcp->flags |= TCB_ATTACHED | TCB_STARTUP;
1339 /* With -D, we are *child* here, the tracee is our parent. */
1340 strace_child = strace_tracer_pid;
1341 strace_tracer_pid = getpid();
1342 alloctcb(strace_child);
1343 /* attaching will be done later, by startup_attach */
1344 /* note: we don't do newoutf(tcp) here either! */
1346 /* NOMMU BUG! -D mode is active, we (child) return,
1347 * and we will scribble over parent's stack!
1348 * When parent later unpauses, it segfaults.
1351 * (1) by declaring exec_or_die() NORETURN,
1352 * hopefully compiler will just jump to it
1353 * instead of call (won't push anything to stack),
1354 * (2) by trying very hard in exec_or_die()
1355 * to not use any stack,
1356 * (3) having a really big (PATH_MAX) stack object
1357 * in this function, which creates a "buffer" between
1358 * child's and parent's stack pointers.
1359 * This may save us if (1) and (2) failed
1360 * and compiler decided to use stack in exec_or_die() anyway
1361 * (happens on i386 because of stack parameter passing).
1363 * A cleaner solution is to use makecontext + setcontext
1364 * to create a genuine separate stack and execute on it.
1368 * A case where straced process is part of a pipe:
1369 * { sleep 1; yes | head -n99999; } | strace -o/dev/null sh -c 'exec <&-; sleep 9'
1370 * If strace won't close its fd#0, closing it in tracee is not enough:
1371 * the pipe is still open, it has a reader. Thus, "head" will not get its
1372 * SIGPIPE at once, on the first write.
1374 * Preventing it by closing strace's stdin/out.
1375 * (Don't leave fds 0 and 1 closed, this is bad practice: future opens
1376 * will reuse them, unexpectedly making a newly opened object "stdin").
1379 open_dummy_desc(); /* opens to fd#0 */
1382 /* A good idea too, but we sometimes need to print error messages */
1383 if (shared_log != stderr)
1390 test_ptrace_seize(void)
1394 /* Need fork for test. NOMMU has no forks */
1396 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1402 perror_msg_and_die("fork");
1409 /* PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After
1410 * attaching tracee continues to run unless a trap condition occurs.
1411 * PTRACE_SEIZE doesn't affect signal or group stop state.
1413 if (ptrace(PTRACE_SEIZE, pid, 0, 0) == 0) {
1414 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1415 } else if (debug_flag) {
1416 error_msg("PTRACE_SEIZE doesn't work");
1422 int status, tracee_pid;
1425 tracee_pid = waitpid(pid, &status, 0);
1426 if (tracee_pid <= 0) {
1429 perror_msg_and_die("%s: unexpected wait result %d",
1430 __func__, tracee_pid);
1432 if (WIFSIGNALED(status)) {
1435 error_msg_and_die("%s: unexpected wait status %x",
1439 #else /* !USE_SEIZE */
1440 # define test_ptrace_seize() ((void)0)
1444 get_os_release(void)
1450 perror_msg_and_die("uname");
1451 /* u.release has this form: "3.2.9[-some-garbage]" */
1455 if (!(*p >= '0' && *p <= '9'))
1456 error_msg_and_die("Bad OS release string: '%s'", u.release);
1457 /* Note: this open-codes KERNEL_VERSION(): */
1458 rel = (rel << 8) | atoi(p);
1459 if (rel >= KERNEL_VERSION(1,0,0))
1461 while (*p >= '0' && *p <= '9')
1464 if (rel >= KERNEL_VERSION(0,1,0)) {
1465 /* "X.Y-something" means "X.Y.0" */
1469 error_msg_and_die("Bad OS release string: '%s'", u.release);
1477 * Initialization part of main() was eating much stack (~0.5k),
1478 * which was unused after init.
1479 * We can reuse it if we move init code into a separate function.
1481 * Don't want main() to inline us and defeat the reason
1482 * we have a separate function.
1484 static void ATTRIBUTE_NOINLINE
1485 init(int argc, char *argv[])
1491 struct sigaction sa;
1493 progname = argv[0] ? argv[0] : "strace";
1495 /* Make sure SIGCHLD has the default action so that waitpid
1496 definitely works without losing track of children. The user
1497 should not have given us a bogus state to inherit, but he might
1498 have. Arguably we should detect SIG_IGN here and pass it on
1499 to children, but probably noone really needs that. */
1500 signal(SIGCHLD, SIG_DFL);
1502 strace_tracer_pid = getpid();
1504 os_release = get_os_release();
1506 /* Allocate the initial tcbtab. */
1507 tcbtabsize = argc; /* Surely enough for all -p args. */
1508 tcbtab = xcalloc(tcbtabsize, sizeof(tcbtab[0]));
1509 tcp = xcalloc(tcbtabsize, sizeof(*tcp));
1510 for (tcbi = 0; tcbi < tcbtabsize; tcbi++)
1511 tcbtab[tcbi] = tcp++;
1513 shared_log = stderr;
1514 set_sortby(DEFAULT_SORTBY);
1515 set_personality(DEFAULT_PERSONALITY);
1516 qualify("trace=all");
1517 qualify("abbrev=all");
1518 qualify("verbose=all");
1519 #if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
1520 # error Bug in DEFAULT_QUAL_FLAGS
1522 qualify("signal=all");
1523 while ((c = getopt(argc, argv,
1524 "+b:cCdfFhiqrtTvVwxyz"
1525 #ifdef USE_LIBUNWIND
1529 "a:e:o:O:p:s:S:u:E:P:I:")) != EOF) {
1532 if (strcmp(optarg, "execve") != 0)
1533 error_msg_and_die("Syscall '%s' for -b isn't supported",
1535 detach_on_execve = 1;
1538 if (cflag == CFLAG_BOTH) {
1539 error_msg_and_help("-c and -C are mutually exclusive");
1541 cflag = CFLAG_ONLY_STATS;
1544 if (cflag == CFLAG_ONLY_STATS) {
1545 error_msg_and_help("-c and -C are mutually exclusive");
1553 daemonized_tracer = 1;
1572 /* fall through to tflag++ */
1580 count_wallclock = 1;
1589 qualify("abbrev=none");
1592 printf("%s -- version %s\n", PACKAGE_NAME, VERSION);
1596 not_failing_only = 1;
1599 acolumn = string_to_uint(optarg);
1601 error_opt_arg(c, optarg);
1607 outfname = xstrdup(optarg);
1610 i = string_to_uint(optarg);
1612 error_opt_arg(c, optarg);
1616 process_opt_p_list(optarg);
1619 pathtrace_select(optarg);
1622 i = string_to_uint(optarg);
1624 error_opt_arg(c, optarg);
1631 username = xstrdup(optarg);
1633 #ifdef USE_LIBUNWIND
1635 stack_trace_enabled = true;
1639 if (putenv(optarg) < 0)
1640 die_out_of_memory();
1643 opt_intr = string_to_uint(optarg);
1644 if (opt_intr <= 0 || opt_intr >= NUM_INTR_OPTS)
1645 error_opt_arg(c, optarg);
1648 error_msg_and_help(NULL);
1653 /* argc -= optind; - no need, argc is not used below */
1655 acolumn_spaces = xmalloc(acolumn + 1);
1656 memset(acolumn_spaces, ' ', acolumn);
1657 acolumn_spaces[acolumn] = '\0';
1659 if (!argv[0] && !nprocs) {
1660 error_msg_and_help("must have PROG [ARGS] or -p PID");
1663 if (!argv[0] && daemonized_tracer) {
1664 error_msg_and_help("PROG [ARGS] must be specified with -D");
1670 if (followfork >= 2 && cflag) {
1671 error_msg_and_help("(-c or -C) and -ff are mutually exclusive");
1674 if (count_wallclock && !cflag) {
1675 error_msg_and_help("-w must be given with (-c or -C)");
1678 if (cflag == CFLAG_ONLY_STATS) {
1680 error_msg("-%c has no effect with -c", 'i');
1681 #ifdef USE_LIBUNWIND
1682 if (stack_trace_enabled)
1683 error_msg("-%c has no effect with -c", 'k');
1686 error_msg("-%c has no effect with -c", 'r');
1688 error_msg("-%c has no effect with -c", 't');
1690 error_msg("-%c has no effect with -c", 'T');
1692 error_msg("-%c has no effect with -c", 'y');
1695 #ifdef USE_LIBUNWIND
1696 if (stack_trace_enabled)
1700 /* See if they want to run as another user. */
1701 if (username != NULL) {
1702 struct passwd *pent;
1704 if (getuid() != 0 || geteuid() != 0) {
1705 error_msg_and_die("You must be root to use the -u option");
1707 pent = getpwnam(username);
1709 error_msg_and_die("Cannot find user '%s'", username);
1711 run_uid = pent->pw_uid;
1712 run_gid = pent->pw_gid;
1720 ptrace_setoptions |= PTRACE_O_TRACECLONE |
1721 PTRACE_O_TRACEFORK |
1722 PTRACE_O_TRACEVFORK;
1724 error_msg("ptrace_setoptions = %#x", ptrace_setoptions);
1725 test_ptrace_seize();
1727 if (fcntl(0, F_GETFD) == -1 || fcntl(1, F_GETFD) == -1) {
1729 * Something weird with our stdin and/or stdout -
1730 * for example, may be not open? In this case,
1731 * ensure that none of the future opens uses them.
1733 * This was seen in the wild when /proc/sys/kernel/core_pattern
1734 * was set to "|/bin/strace -o/tmp/LOG PROG":
1735 * kernel runs coredump helper with fd#0 open but fd#1 closed (!),
1736 * therefore LOG gets opened to fd#1, and fd#1 is closed by
1737 * "don't hold up stdin/out open" code soon after.
1739 int fd = open_dummy_desc();
1740 while (fd >= 0 && fd < 2)
1746 /* Check if they want to redirect the output. */
1748 /* See if they want to pipe the output. */
1749 if (outfname[0] == '|' || outfname[0] == '!') {
1751 * We can't do the <outfname>.PID funny business
1752 * when using popen, so prohibit it.
1754 if (followfork >= 2)
1755 error_msg_and_help("piping the output and -ff are mutually exclusive");
1756 shared_log = strace_popen(outfname + 1);
1758 else if (followfork < 2)
1759 shared_log = strace_fopen(outfname);
1761 /* -ff without -o FILE is the same as single -f */
1762 if (followfork >= 2)
1766 if (!outfname || outfname[0] == '|' || outfname[0] == '!') {
1767 char *buf = xmalloc(BUFSIZ);
1768 setvbuf(shared_log, buf, _IOLBF, BUFSIZ);
1770 if (outfname && argv[0]) {
1772 opt_intr = INTR_NEVER;
1777 opt_intr = INTR_WHILE_WAIT;
1779 /* argv[0] -pPID -oFILE Default interactive setting
1780 * yes * 0 INTR_WHILE_WAIT
1781 * no 1 0 INTR_WHILE_WAIT
1782 * yes * 1 INTR_NEVER
1783 * no 1 1 INTR_WHILE_WAIT
1786 sigemptyset(&empty_set);
1787 sigemptyset(&blocked_set);
1789 /* startup_child() must be called before the signal handlers get
1790 * installed below as they are inherited into the spawned process.
1791 * Also we do not need to be protected by them as during interruption
1792 * in the startup_child() mode we kill the spawned process anyway.
1795 if (!NOMMU_SYSTEM || daemonized_tracer)
1796 hide_log_until_execve = 1;
1797 skip_one_b_execve = 1;
1798 startup_child(argv);
1801 sa.sa_handler = SIG_IGN;
1802 sigemptyset(&sa.sa_mask);
1804 sigaction(SIGTTOU, &sa, NULL); /* SIG_IGN */
1805 sigaction(SIGTTIN, &sa, NULL); /* SIG_IGN */
1806 if (opt_intr != INTR_ANYWHERE) {
1807 if (opt_intr == INTR_BLOCK_TSTP_TOO)
1808 sigaction(SIGTSTP, &sa, NULL); /* SIG_IGN */
1810 * In interactive mode (if no -o OUTFILE, or -p PID is used),
1811 * fatal signals are blocked while syscall stop is processed,
1812 * and acted on in between, when waiting for new syscall stops.
1813 * In non-interactive mode, signals are ignored.
1815 if (opt_intr == INTR_WHILE_WAIT) {
1816 sigaddset(&blocked_set, SIGHUP);
1817 sigaddset(&blocked_set, SIGINT);
1818 sigaddset(&blocked_set, SIGQUIT);
1819 sigaddset(&blocked_set, SIGPIPE);
1820 sigaddset(&blocked_set, SIGTERM);
1821 sa.sa_handler = interrupt;
1823 /* SIG_IGN, or set handler for these */
1824 sigaction(SIGHUP, &sa, NULL);
1825 sigaction(SIGINT, &sa, NULL);
1826 sigaction(SIGQUIT, &sa, NULL);
1827 sigaction(SIGPIPE, &sa, NULL);
1828 sigaction(SIGTERM, &sa, NULL);
1830 if (nprocs != 0 || daemonized_tracer)
1833 /* Do we want pids printed in our -o OUTFILE?
1834 * -ff: no (every pid has its own file); or
1835 * -f: yes (there can be more pids in the future); or
1836 * -p PID1,PID2: yes (there are already more than one pid)
1838 print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
1849 for (i = 0; i < tcbtabsize; i++) {
1850 struct tcb *tcp = tcbtab[i];
1851 if (tcp->pid == pid)
1865 /* 'interrupted' is a volatile object, fetch it only once */
1866 fatal_sig = interrupted;
1868 fatal_sig = SIGTERM;
1870 for (i = 0; i < tcbtabsize; i++) {
1875 error_msg("cleanup: looking at pid %u", tcp->pid);
1876 if (tcp->pid == strace_child) {
1877 kill(tcp->pid, SIGCONT);
1878 kill(tcp->pid, fatal_sig);
1883 call_summary(shared_log);
1893 print_debug_info(const int pid, int status)
1895 const unsigned int event = (unsigned int) status >> 16;
1896 char buf[sizeof("WIFEXITED,exitcode=%u") + sizeof(int)*3 /*paranoia:*/ + 16];
1897 char evbuf[sizeof(",EVENT_VFORK_DONE (%u)") + sizeof(int)*3 /*paranoia:*/ + 16];
1900 if (WIFSIGNALED(status))
1902 sprintf(buf, "WIFSIGNALED,%ssig=%s",
1903 WCOREDUMP(status) ? "core," : "",
1904 signame(WTERMSIG(status)));
1906 sprintf(buf, "WIFSIGNALED,sig=%s",
1907 signame(WTERMSIG(status)));
1909 if (WIFEXITED(status))
1910 sprintf(buf, "WIFEXITED,exitcode=%u", WEXITSTATUS(status));
1911 if (WIFSTOPPED(status))
1912 sprintf(buf, "WIFSTOPPED,sig=%s", signame(WSTOPSIG(status)));
1914 /* Should never be seen */
1915 if (WIFCONTINUED(status))
1916 strcpy(buf, "WIFCONTINUED");
1920 static const char *const event_names[] = {
1921 [PTRACE_EVENT_CLONE] = "CLONE",
1922 [PTRACE_EVENT_FORK] = "FORK",
1923 [PTRACE_EVENT_VFORK] = "VFORK",
1924 [PTRACE_EVENT_VFORK_DONE] = "VFORK_DONE",
1925 [PTRACE_EVENT_EXEC] = "EXEC",
1926 [PTRACE_EVENT_EXIT] = "EXIT",
1927 /* [PTRACE_EVENT_STOP (=128)] would make biggish array */
1929 const char *e = "??";
1930 if (event < ARRAY_SIZE(event_names))
1931 e = event_names[event];
1932 else if (event == PTRACE_EVENT_STOP)
1934 sprintf(evbuf, ",EVENT_%s (%u)", e, event);
1936 error_msg("[wait(0x%06x) = %u] %s%s", status, pid, buf, evbuf);
1940 maybe_allocate_tcb(const int pid, int status)
1942 if (!WIFSTOPPED(status)) {
1943 if (detach_on_execve && pid == strace_child) {
1944 /* example: strace -bexecve sh -c 'exec true' */
1949 * This can happen if we inherited an unknown child.
1950 * Example: (sleep 1 & exec strace true)
1952 error_msg("Exit of unknown pid %u ignored", pid);
1956 /* We assume it's a fork/vfork/clone child */
1957 struct tcb *tcp = alloctcb(pid);
1958 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1961 error_msg("Process %d attached", pid);
1964 /* This can happen if a clone call used
1965 * CLONE_PTRACE itself.
1967 ptrace(PTRACE_CONT, pid, (char *) 0, 0);
1968 error_msg("Stop of unknown pid %u seen, PTRACE_CONTed it", pid);
1974 maybe_switch_tcbs(struct tcb *tcp, const int pid)
1977 struct tcb *execve_thread;
1980 if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, (long) &old_pid) < 0)
1982 /* Avoid truncation in pid2tcb() param passing */
1983 if (old_pid <= 0 || old_pid == pid)
1985 if ((unsigned long) old_pid > UINT_MAX)
1987 execve_thread = pid2tcb(old_pid);
1988 /* It should be !NULL, but I feel paranoid */
1992 if (execve_thread->curcol != 0) {
1994 * One case we are here is -ff:
1995 * try "strace -oLOG -ff test/threaded_execve"
1997 fprintf(execve_thread->outf, " <pid changed to %d ...>\n", pid);
1998 /*execve_thread->curcol = 0; - no need, see code below */
2000 /* Swap output FILEs (needed for -ff) */
2001 fp = execve_thread->outf;
2002 execve_thread->outf = tcp->outf;
2004 /* And their column positions */
2005 execve_thread->curcol = tcp->curcol;
2007 /* Drop leader, but close execve'd thread outfile (if -ff) */
2009 /* Switch to the thread, reusing leader's outfile and pid */
2010 tcp = execve_thread;
2012 if (cflag != CFLAG_ONLY_STATS) {
2014 tprintf("+++ superseded by execve in pid %lu +++\n", old_pid);
2016 tcp->flags |= TCB_REPRINT;
2023 print_signalled(struct tcb *tcp, const int pid, int status)
2025 if (pid == strace_child) {
2026 exit_code = 0x100 | WTERMSIG(status);
2030 if (cflag != CFLAG_ONLY_STATS
2031 && (qual_flags[WTERMSIG(status)] & QUAL_SIGNAL)
2035 tprintf("+++ killed by %s %s+++\n",
2036 signame(WTERMSIG(status)),
2037 WCOREDUMP(status) ? "(core dumped) " : "");
2039 tprintf("+++ killed by %s +++\n",
2040 signame(WTERMSIG(status)));
2047 print_exited(struct tcb *tcp, const int pid, int status)
2049 if (pid == strace_child) {
2050 exit_code = WEXITSTATUS(status);
2054 if (cflag != CFLAG_ONLY_STATS &&
2057 tprintf("+++ exited with %d +++\n", WEXITSTATUS(status));
2063 print_stopped(struct tcb *tcp, const siginfo_t *si, const unsigned int sig)
2065 if (cflag != CFLAG_ONLY_STATS
2066 && !hide_log_until_execve
2067 && (qual_flags[sig] & QUAL_SIGNAL)
2071 tprintf("--- %s ", signame(sig));
2072 printsiginfo(si, verbose(tcp));
2075 tprintf("--- stopped by %s ---\n", signame(sig));
2081 startup_tcb(struct tcb *tcp)
2084 error_msg("pid %d has TCB_STARTUP, initializing it", tcp->pid);
2086 tcp->flags &= ~TCB_STARTUP;
2090 error_msg("setting opts 0x%x on pid %d",
2091 ptrace_setoptions, tcp->pid);
2092 if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, ptrace_setoptions) < 0) {
2093 if (errno != ESRCH) {
2094 /* Should never happen, really */
2095 perror_msg_and_die("PTRACE_SETOPTIONS");
2101 /* Returns true iff the main trace loop has to continue. */
2118 * Used to exit simply when nprocs hits zero, but in this testcase:
2119 * int main() { _exit(!!fork()); }
2120 * under strace -f, parent sometimes (rarely) manages
2121 * to exit before we see the first stop of the child,
2122 * and we are losing track of it:
2123 * 19923 clone(...) = 19924
2124 * 19923 exit_group(1) = ?
2125 * 19923 +++ exited with 1 +++
2126 * Exiting only when wait() returns ECHILD works better.
2128 if (popen_pid != 0) {
2129 /* However, if -o|logger is in use, we can't do that.
2130 * Can work around that by double-forking the logger,
2131 * but that loses the ability to wait for its completion
2132 * on exit. Oh well...
2139 sigprocmask(SIG_SETMASK, &empty_set, NULL);
2140 pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
2143 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
2146 if (wait_errno == EINTR)
2148 if (nprocs == 0 && wait_errno == ECHILD)
2151 * If nprocs > 0, ECHILD is not expected,
2152 * treat it as any other error here:
2155 perror_msg_and_die("wait4(__WALL)");
2158 if (pid == popen_pid) {
2159 if (!WIFSTOPPED(status))
2165 print_debug_info(pid, status);
2167 /* Look up 'pid' in our table. */
2171 tcp = maybe_allocate_tcb(pid, status);
2176 if (WIFSTOPPED(status))
2181 event = (unsigned int) status >> 16;
2183 if (event == PTRACE_EVENT_EXEC) {
2185 * Under Linux, execve changes pid to thread leader's pid,
2186 * and we see this changed pid on EVENT_EXEC and later,
2187 * execve sysexit. Leader "disappears" without exit
2188 * notification. Let user know that, drop leader's tcb,
2189 * and fix up pid in execve thread's tcb.
2190 * Effectively, execve thread's tcb replaces leader's tcb.
2192 * BTW, leader is 'stuck undead' (doesn't report WIFEXITED
2193 * on exit syscall) in multithreaded programs exactly
2194 * in order to handle this case.
2196 * PTRACE_GETEVENTMSG returns old pid starting from Linux 3.0.
2197 * On 2.6 and earlier, it can return garbage.
2199 if (os_release >= KERNEL_VERSION(3,0,0))
2200 tcp = maybe_switch_tcbs(tcp, pid);
2202 if (detach_on_execve && !skip_one_b_execve) {
2203 detach(tcp); /* do "-b execve" thingy */
2206 skip_one_b_execve = 0;
2209 /* Set current output file */
2213 tv_sub(&tcp->dtime, &ru.ru_stime, &tcp->stime);
2214 tcp->stime = ru.ru_stime;
2217 if (WIFSIGNALED(status)) {
2218 print_signalled(tcp, pid, status);
2223 if (WIFEXITED(status)) {
2224 print_exited(tcp, pid, status);
2229 if (!WIFSTOPPED(status)) {
2231 * Neither signalled, exited or stopped.
2232 * How could that be?
2234 error_msg("pid %u not stopped!", pid);
2239 /* Is this the very first time we see this tracee stopped? */
2240 if (tcp->flags & TCB_STARTUP) {
2242 if (get_scno(tcp) == 1)
2243 tcp->s_prev_ent = tcp->s_ent;
2246 sig = WSTOPSIG(status);
2251 if (event == PTRACE_EVENT_STOP) {
2253 * PTRACE_INTERRUPT-stop or group-stop.
2254 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
2266 goto restart_tracee_with_sig_0;
2270 * Is this post-attach SIGSTOP?
2271 * Interestingly, the process may stop
2272 * with STOPSIG equal to some other signal
2273 * than SIGSTOP if we happend to attach
2274 * just before the process takes a signal.
2276 if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
2278 error_msg("ignored SIGSTOP on pid %d", tcp->pid);
2279 tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
2280 goto restart_tracee_with_sig_0;
2283 if (sig != syscall_trap_sig) {
2287 * True if tracee is stopped by signal
2288 * (as opposed to "tracee received signal").
2289 * TODO: shouldn't we check for errno == EINVAL too?
2290 * We can get ESRCH instead, you know...
2292 stopped = ptrace(PTRACE_GETSIGINFO, pid, 0, (long) &si) < 0;
2296 print_stopped(tcp, stopped ? NULL : &si, sig);
2299 /* It's signal-delivery-stop. Inject the signal */
2300 goto restart_tracee;
2302 /* It's group-stop */
2305 * This ends ptrace-stop, but does *not* end group-stop.
2306 * This makes stopping signals work properly on straced process
2307 * (that is, process really stops. It used to continue to run).
2309 if (ptrace_restart(PTRACE_LISTEN, tcp, 0) < 0) {
2310 /* Note: ptrace_restart emitted error message */
2316 /* We don't have PTRACE_LISTEN support... */
2317 goto restart_tracee;
2320 /* We handled quick cases, we are permitted to interrupt now. */
2325 * This should be syscall entry or exit.
2328 if (trace_syscall(tcp) < 0) {
2330 * ptrace() failed in trace_syscall().
2331 * Likely a result of process disappearing mid-flight.
2332 * Observed case: exit_group() or SIGKILL terminating
2333 * all processes in thread group.
2334 * We assume that ptrace error was caused by process death.
2335 * We used to detach(tcp) here, but since we no longer
2336 * implement "detach before death" policy/hack,
2337 * we can let this process to report its death to us
2338 * normally, via WIFEXITED or WIFSIGNALED wait status.
2343 restart_tracee_with_sig_0:
2347 if (ptrace_restart(PTRACE_SYSCALL, tcp, sig) < 0) {
2348 /* Note: ptrace_restart emitted error message */
2357 main(int argc, char *argv[])
2366 if (shared_log != stderr)
2369 while (waitpid(popen_pid, NULL, 0) < 0 && errno == EINTR)
2372 if (exit_code > 0xff) {
2373 /* Avoid potential core file clobbering. */
2374 struct_rlimit rlim = {0, 0};
2375 set_rlimit(RLIMIT_CORE, &rlim);
2377 /* Child was killed by a signal, mimic that. */
2379 signal(exit_code, SIG_DFL);
2381 /* Paranoia - what if this signal is not fatal?
2382 Exit with 128 + signo then. */