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>
46 #include <asm/unistd.h>
50 #include "printsiginfo.h"
52 /* In some libc, these aren't declared. Do it ourself: */
53 extern char **environ;
58 /* if this is true do the stack trace for every system call */
59 bool stack_trace_enabled = false;
62 #define my_tkill(tid, sig) syscall(__NR_tkill, (tid), (sig))
64 /* Glue for systems without a MMU that cannot provide fork() */
65 #if !defined(HAVE_FORK)
67 # define NOMMU_SYSTEM 1
70 # define fork() vfork()
73 const unsigned int syscall_trap_sig = SIGTRAP | 0x80;
75 cflag_t cflag = CFLAG_NONE;
76 unsigned int followfork = 0;
77 unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC
79 unsigned int xflag = 0;
83 bool count_wallclock = 0;
84 unsigned int qflag = 0;
85 static unsigned int tflag = 0;
86 static bool rflag = 0;
87 static bool print_pid_pfx = 0;
92 INTR_ANYWHERE = 1, /* don't block/ignore any signals */
93 INTR_WHILE_WAIT = 2, /* block fatal signals while decoding syscall. default */
94 INTR_NEVER = 3, /* block fatal signals. default if '-o FILE PROG' */
95 INTR_BLOCK_TSTP_TOO = 4, /* block fatal signals and SIGTSTP (^Z) */
99 /* We play with signal mask only if this mode is active: */
100 #define interactive (opt_intr == INTR_WHILE_WAIT)
103 * daemonized_tracer supports -D option.
104 * With this option, strace forks twice.
105 * Unlike normal case, with -D *grandparent* process exec's,
106 * becoming a traced process. Child exits (this prevents traced process
107 * from having children it doesn't expect to have), and grandchild
108 * attaches to grandparent similarly to strace -p PID.
109 * This allows for more transparent interaction in cases
110 * when process and its parent are communicating via signals,
111 * wait() etc. Without -D, strace process gets lodged in between,
112 * disrupting parent<->child link.
114 static bool daemonized_tracer = 0;
117 static int post_attach_sigstop = TCB_IGNORE_ONE_SIGSTOP;
118 # define use_seize (post_attach_sigstop == 0)
120 # define post_attach_sigstop TCB_IGNORE_ONE_SIGSTOP
124 /* Sometimes we want to print only succeeding syscalls. */
125 bool not_failing_only = 0;
127 /* Show path associated with fd arguments */
128 unsigned int show_fd_path = 0;
130 static bool detach_on_execve = 0;
132 static int exit_code;
133 static int strace_child = 0;
134 static int strace_tracer_pid = 0;
136 static char *username = NULL;
137 static uid_t run_uid;
138 static gid_t run_gid;
140 unsigned int max_strlen = DEFAULT_STRLEN;
141 static int acolumn = DEFAULT_ACOLUMN;
142 static char *acolumn_spaces;
144 static char *outfname = NULL;
145 /* If -ff, points to stderr. Else, it's our common output log */
146 static FILE *shared_log;
148 struct tcb *printing_tcp = NULL;
149 static struct tcb *current_tcp;
151 static struct tcb **tcbtab;
152 static unsigned int nprocs, tcbtabsize;
153 static const char *progname;
155 unsigned os_release; /* generated from uname()'s u.release */
157 static void detach(struct tcb *tcp);
158 static void cleanup(void);
159 static void interrupt(int sig);
160 static sigset_t empty_set, blocked_set;
162 #ifdef HAVE_SIG_ATOMIC_T
163 static volatile sig_atomic_t interrupted;
165 static volatile int interrupted;
168 #ifndef HAVE_STRERROR
170 #if !HAVE_DECL_SYS_ERRLIST
172 extern char *sys_errlist[];
178 static char buf[sizeof("Unknown error %d") + sizeof(int)*3];
180 if (err_no < 1 || err_no >= sys_nerr) {
181 sprintf(buf, "Unknown error %d", err_no);
184 return sys_errlist[err_no];
187 #endif /* HAVE_STERRROR */
192 printf("%s -- version %s\n"
193 "Copyright (C) %s The strace developers <%s>.\n"
194 "This is free software; see the source for copying conditions. There is NO\n"
195 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n",
196 PACKAGE_NAME, PACKAGE_VERSION, "1991-2017", PACKAGE_URL);
203 usage: strace [-CdffhiqrtttTvVwxxy] [-I n] [-e expr]...\n\
204 [-a column] [-o file] [-s strsize] [-P path]...\n\
205 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
206 or: strace -c[dfw] [-I n] [-e expr]... [-O overhead] [-S sortby]\n\
207 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
210 -a column alignment COLUMN for printing syscall results (default %d)\n\
211 -i print instruction pointer at time of syscall\n\
212 -o file send trace output to FILE instead of stderr\n\
213 -q suppress messages about attaching, detaching, etc.\n\
214 -r print relative timestamp\n\
215 -s strsize limit length of print strings to STRSIZE chars (default %d)\n\
216 -t print absolute timestamp\n\
217 -tt print absolute timestamp with usecs\n\
218 -T print time spent in each syscall\n\
219 -x print non-ascii strings in hex\n\
220 -xx print all strings in hex\n\
221 -y print paths associated with file descriptor arguments\n\
222 -yy print protocol specific information associated with socket file descriptors\n\
225 -c count time, calls, and errors for each syscall and report summary\n\
226 -C like -c but also print regular output\n\
227 -O overhead set overhead for tracing syscalls to OVERHEAD usecs\n\
228 -S sortby sort syscall counts by: time, calls, name, nothing (default %s)\n\
229 -w summarise syscall latency (default is system time)\n\
232 -e expr a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
233 options: trace, abbrev, verbose, raw, signal, read, write, fault\n\
234 -P path trace accesses to path\n\
237 -b execve detach on execve syscall\n\
238 -D run tracer process as a detached grandchild, not as parent\n\
240 -ff follow forks with output into separate files\n\
242 1: no signals are blocked\n\
243 2: fatal signals are blocked while decoding syscall (default)\n\
244 3: fatal signals are always blocked (default if '-o FILE PROG')\n\
245 4: fatal signals and SIGTSTP (^Z) are always blocked\n\
246 (useful to make 'strace -o FILE PROG' not stop on ^Z)\n\
249 -E var remove var from the environment for command\n\
250 -E var=val put var=val in the environment for command\n\
251 -p pid trace process with process id PID, may be repeated\n\
252 -u username run command as username handling setuid and/or setgid\n\
255 -d enable debug output to stderr\n\
256 -v verbose mode: print unabbreviated argv, stat, termios, etc. args\n\
257 -h print help message\n\
261 " -k obtain stack trace between each syscall (experimental)\n\
264 /* ancient, no one should use it
265 -F -- attempt to follow vforks (deprecated, use -f)\n\
267 /* this is broken, so don't document it
268 -z -- print only succeeding syscalls\n\
270 , DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
274 static void ATTRIBUTE_NORETURN
277 if (strace_tracer_pid == getpid()) {
284 static void verror_msg(int err_no, const char *fmt, va_list p)
290 /* We want to print entire message with single fprintf to ensure
291 * message integrity if stderr is shared with other programs.
292 * Thus we use vasprintf + single fprintf.
295 if (vasprintf(&msg, fmt, p) >= 0) {
297 fprintf(stderr, "%s: %s: %s\n", progname, msg, strerror(err_no));
299 fprintf(stderr, "%s: %s\n", progname, msg);
302 /* malloc in vasprintf failed, try it without malloc */
303 fprintf(stderr, "%s: ", progname);
304 vfprintf(stderr, fmt, p);
306 fprintf(stderr, ": %s\n", strerror(err_no));
310 /* We don't switch stderr to buffered, thus fprintf(stderr)
311 * always flushes its output and this is not necessary: */
312 /* fflush(stderr); */
315 void error_msg(const char *fmt, ...)
319 verror_msg(0, fmt, p);
323 void error_msg_and_die(const char *fmt, ...)
327 verror_msg(0, fmt, p);
331 void error_msg_and_help(const char *fmt, ...)
336 verror_msg(0, fmt, p);
338 fprintf(stderr, "Try '%s -h' for more information.\n", progname);
342 void perror_msg(const char *fmt, ...)
346 verror_msg(errno, fmt, p);
350 void perror_msg_and_die(const char *fmt, ...)
354 verror_msg(errno, fmt, p);
359 error_opt_arg(int opt, const char *arg)
361 error_msg_and_help("invalid -%c argument: '%s'", opt, arg);
364 static const char *ptrace_attach_cmd;
367 ptrace_attach_or_seize(int pid)
372 return ptrace_attach_cmd = "PTRACE_ATTACH",
373 ptrace(PTRACE_ATTACH, pid, 0L, 0L);
374 r = ptrace(PTRACE_SEIZE, pid, 0L, (unsigned long) ptrace_setoptions);
376 return ptrace_attach_cmd = "PTRACE_SEIZE", r;
377 r = ptrace(PTRACE_INTERRUPT, pid, 0L, 0L);
378 return ptrace_attach_cmd = "PTRACE_INTERRUPT", r;
380 return ptrace_attach_cmd = "PTRACE_ATTACH",
381 ptrace(PTRACE_ATTACH, pid, 0L, 0L);
386 * Used when we want to unblock stopped traced process.
387 * Should be only used with PTRACE_CONT, PTRACE_DETACH and PTRACE_SYSCALL.
388 * Returns 0 on success or if error was ESRCH
389 * (presumably process was killed while we talk to it).
390 * Otherwise prints error message and returns -1.
393 ptrace_restart(const unsigned int op, struct tcb *const tcp, unsigned int sig)
399 ptrace(op, tcp->pid, 0L, (unsigned long) sig);
419 * Why curcol != 0? Otherwise sometimes we get this:
421 * 10252 kill(10253, SIGKILL) = 0
422 * <ptrace(SYSCALL,10252):No such process>10253 ...next decode...
424 * 10252 died after we retrieved syscall exit data,
425 * but before we tried to restart it. Log looks ugly.
427 if (current_tcp && current_tcp->curcol != 0) {
428 tprintf(" <ptrace(%s):%s>\n", msg, strerror(err));
434 perror_msg("ptrace(PTRACE_%s,pid:%d,sig:%u)", msg, tcp->pid, sig);
439 set_cloexec_flag(int fd)
443 flags = fcntl(fd, F_GETFD);
445 /* Can happen only if fd is bad.
446 * Should never happen: if it does, we have a bug
447 * in the caller. Therefore we just abort
448 * instead of propagating the error.
450 perror_msg_and_die("fcntl(%d, F_GETFD)", fd);
453 newflags = flags | FD_CLOEXEC;
454 if (flags == newflags)
457 fcntl(fd, F_SETFD, newflags); /* never fails */
461 kill_save_errno(pid_t pid, int sig)
463 int saved_errno = errno;
465 (void) kill(pid, sig);
470 * When strace is setuid executable, we have to swap uids
471 * before and after filesystem and process management operations.
476 int euid = geteuid(), uid = getuid();
478 if (euid != uid && setreuid(euid, uid) < 0) {
479 perror_msg_and_die("setreuid");
483 #ifdef _LARGEFILE64_SOURCE
485 # define fopen_for_output fopen64
487 # define fopen_for_output fopen
489 # define struct_stat struct stat64
490 # define stat_file stat64
491 # define struct_dirent struct dirent64
492 # define read_dir readdir64
493 # define struct_rlimit struct rlimit64
494 # define set_rlimit setrlimit64
496 # define fopen_for_output fopen
497 # define struct_stat struct stat
498 # define stat_file stat
499 # define struct_dirent struct dirent
500 # define read_dir readdir
501 # define struct_rlimit struct rlimit
502 # define set_rlimit setrlimit
506 strace_fopen(const char *path)
511 fp = fopen_for_output(path, "w");
513 perror_msg_and_die("Can't fopen '%s'", path);
515 set_cloexec_flag(fileno(fp));
519 static int popen_pid = 0;
522 # define _PATH_BSHELL "/bin/sh"
526 * We cannot use standard popen(3) here because we have to distinguish
527 * popen child process from other processes we trace, and standard popen(3)
528 * does not export its child's pid.
531 strace_popen(const char *command)
539 perror_msg_and_die("pipe");
541 set_cloexec_flag(fds[1]); /* never fails */
545 perror_msg_and_die("vfork");
552 perror_msg_and_die("dup2");
555 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
556 perror_msg_and_die("Can't execute '%s'", _PATH_BSHELL);
563 fp = fdopen(fds[1], "w");
570 tprintf(const char *fmt, ...)
576 int n = strace_vfprintf(current_tcp->outf, fmt, args);
578 if (current_tcp->outf != stderr)
579 perror_msg("%s", outfname);
581 current_tcp->curcol += n;
586 #ifndef HAVE_FPUTS_UNLOCKED
587 # define fputs_unlocked fputs
591 tprints(const char *str)
594 int n = fputs_unlocked(str, current_tcp->outf);
596 current_tcp->curcol += strlen(str);
599 if (current_tcp->outf != stderr)
600 perror_msg("%s", outfname);
608 current_tcp->curcol = 0;
609 fflush(current_tcp->outf);
612 printing_tcp->curcol = 0;
618 printleader(struct tcb *tcp)
620 /* If -ff, "previous tcb we printed" is always the same as current,
621 * because we have per-tcb output files.
627 current_tcp = printing_tcp;
628 if (printing_tcp->curcol != 0 && (followfork < 2 || printing_tcp == tcp)) {
630 * case 1: we have a shared log (i.e. not -ff), and last line
631 * wasn't finished (same or different tcb, doesn't matter).
632 * case 2: split log, we are the same tcb, but our last line
633 * didn't finish ("SIGKILL nuked us after syscall entry" etc).
635 tprints(" <unfinished ...>\n");
636 printing_tcp->curcol = 0;
642 current_tcp->curcol = 0;
645 tprintf("%-5d ", tcp->pid);
646 else if (nprocs > 1 && !outfname)
647 tprintf("[pid %5u] ", tcp->pid);
650 char str[sizeof("HH:MM:SS")];
651 struct timeval tv, dtv;
652 static struct timeval otv;
654 gettimeofday(&tv, NULL);
658 tv_sub(&dtv, &tv, &otv);
659 tprintf("%6ld.%06ld ",
660 (long) dtv.tv_sec, (long) dtv.tv_usec);
663 else if (tflag > 2) {
664 tprintf("%ld.%06ld ",
665 (long) tv.tv_sec, (long) tv.tv_usec);
668 time_t local = tv.tv_sec;
669 strftime(str, sizeof(str), "%T", localtime(&local));
671 tprintf("%s.%06ld ", str, (long) tv.tv_usec);
683 if (current_tcp->curcol < acolumn)
684 tprints(acolumn_spaces + current_tcp->curcol);
687 /* Should be only called directly *after successful attach* to a tracee.
688 * Otherwise, "strace -oFILE -ff -p<nonexistant_pid>"
689 * may create bogus empty FILE.<nonexistant_pid>, and then die.
692 newoutf(struct tcb *tcp)
694 tcp->outf = shared_log; /* if not -ff mode, the same file is for all */
695 if (followfork >= 2) {
696 char name[520 + sizeof(int) * 3];
697 sprintf(name, "%.512s.%u", outfname, tcp->pid);
698 tcp->outf = strace_fopen(name);
705 /* Allocate some (more) TCBs (and expand the table).
706 We don't want to relocate the TCBs because our
707 callers have pointers and it would be a pain.
708 So tcbtab is a table of pointers. Since we never
709 free the TCBs, we allocate a single chunk of many. */
710 unsigned int new_tcbtabsize, alloc_tcbtabsize;
714 alloc_tcbtabsize = tcbtabsize;
715 new_tcbtabsize = tcbtabsize * 2;
717 new_tcbtabsize = alloc_tcbtabsize = 1;
720 newtcbs = xcalloc(alloc_tcbtabsize, sizeof(newtcbs[0]));
721 tcbtab = xreallocarray(tcbtab, new_tcbtabsize, sizeof(tcbtab[0]));
722 while (tcbtabsize < new_tcbtabsize)
723 tcbtab[tcbtabsize++] = newtcbs++;
732 if (nprocs == tcbtabsize)
735 for (i = 0; i < tcbtabsize; i++) {
738 memset(tcp, 0, sizeof(*tcp));
740 #if SUPPORTED_PERSONALITIES > 1
741 tcp->currpers = current_personality;
745 if (stack_trace_enabled)
746 unwind_tcb_init(tcp);
751 error_msg("new tcb for pid %d, active tcbs:%d",
756 error_msg_and_die("bug in alloctcb");
760 get_tcb_priv_data(const struct tcb *tcp)
762 return tcp->_priv_data;
766 set_tcb_priv_data(struct tcb *tcp, void *const priv_data,
767 void (*const free_priv_data)(void *))
772 tcp->_free_priv_data = free_priv_data;
773 tcp->_priv_data = priv_data;
779 free_tcb_priv_data(struct tcb *tcp)
781 if (tcp->_priv_data) {
782 if (tcp->_free_priv_data) {
783 tcp->_free_priv_data(tcp->_priv_data);
784 tcp->_free_priv_data = NULL;
786 tcp->_priv_data = NULL;
791 droptcb(struct tcb *tcp)
797 for (p = 0; p < SUPPORTED_PERSONALITIES; ++p)
798 free(tcp->fault_vec[p]);
800 free_tcb_priv_data(tcp);
803 if (stack_trace_enabled) {
810 error_msg("dropped tcb for pid %d, %d remain",
814 if (followfork >= 2) {
815 if (tcp->curcol != 0)
816 fprintf(tcp->outf, " <detached ...>\n");
819 if (printing_tcp == tcp && tcp->curcol != 0)
820 fprintf(tcp->outf, " <detached ...>\n");
825 if (current_tcp == tcp)
827 if (printing_tcp == tcp)
830 memset(tcp, 0, sizeof(*tcp));
833 /* Detach traced process.
834 * Never call DETACH twice on the same process as both unattached and
835 * attached-unstopped processes give the same ESRCH. For unattached process we
836 * would SIGSTOP it and wait for its SIGSTOP notification forever.
839 detach(struct tcb *tcp)
845 * Linux wrongly insists the child be stopped
846 * before detaching. Arghh. We go through hoops
847 * to make a clean break of things.
850 if (!(tcp->flags & TCB_ATTACHED))
853 /* We attached but possibly didn't see the expected SIGSTOP.
854 * We must catch exactly one as otherwise the detached process
855 * would be left stopped (process state T).
857 if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
860 error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
862 /* On a clear day, you can see forever. */
865 if (errno != ESRCH) {
866 /* Shouldn't happen. */
867 perror_msg("detach: ptrace(PTRACE_DETACH,%u)", tcp->pid);
870 /* ESRCH: process is either not stopped or doesn't exist. */
871 if (my_tkill(tcp->pid, 0) < 0) {
873 /* Shouldn't happen. */
874 perror_msg("detach: tkill(%u,0)", tcp->pid);
875 /* else: process doesn't exist. */
878 /* Process is not stopped, need to stop it. */
881 * With SEIZE, tracee can be in group-stop already.
882 * In this state sending it another SIGSTOP does nothing.
883 * Need to use INTERRUPT.
884 * Testcase: trying to ^C a "strace -p <stopped_process>".
886 error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
890 perror_msg("detach: ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
893 error = my_tkill(tcp->pid, SIGSTOP);
897 perror_msg("detach: tkill(%u,SIGSTOP)", tcp->pid);
899 /* Either process doesn't exist, or some weird error. */
903 /* We end up here in three cases:
904 * 1. We sent PTRACE_INTERRUPT (use_seize case)
905 * 2. We sent SIGSTOP (!use_seize)
906 * 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
910 if (waitpid(tcp->pid, &status, __WALL) < 0) {
914 * if (errno == ECHILD) break;
915 * ^^^ WRONG! We expect this PID to exist,
916 * and want to emit a message otherwise:
918 perror_msg("detach: waitpid(%u)", tcp->pid);
921 if (!WIFSTOPPED(status)) {
923 * Tracee exited or was killed by signal.
924 * We shouldn't normally reach this place:
925 * we don't want to consume exit status.
926 * Consider "strace -p PID" being ^C-ed:
927 * we want merely to detach from PID.
929 * However, we _can_ end up here if tracee
934 sig = WSTOPSIG(status);
936 error_msg("detach wait: event:%d sig:%d",
937 (unsigned)status >> 16, sig);
939 unsigned event = (unsigned)status >> 16;
940 if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
942 * sig == SIGTRAP: PTRACE_INTERRUPT stop.
943 * sig == other: process was already stopped
944 * with this stopping sig (see tests/detach-stopped).
945 * Looks like re-injecting this sig is not necessary
946 * in DETACH for the tracee to remain stopped.
951 * PTRACE_INTERRUPT is not guaranteed to produce
952 * the above event if other ptrace-stop is pending.
953 * See tests/detach-sleeping testcase:
954 * strace got SIGINT while tracee is sleeping.
955 * We sent PTRACE_INTERRUPT.
956 * We see syscall exit, not PTRACE_INTERRUPT stop.
957 * We won't get PTRACE_INTERRUPT stop
958 * if we would CONT now. Need to DETACH.
960 if (sig == syscall_trap_sig)
962 /* else: not sure in which case we can be here.
963 * Signal stop? Inject it while detaching.
965 ptrace_restart(PTRACE_DETACH, tcp, sig);
968 /* Note: this check has to be after use_seize check */
969 /* (else, in use_seize case SIGSTOP will be mistreated) */
970 if (sig == SIGSTOP) {
971 /* Detach, suppressing SIGSTOP */
972 ptrace_restart(PTRACE_DETACH, tcp, 0);
975 if (sig == syscall_trap_sig)
977 /* Can't detach just yet, may need to wait for SIGSTOP */
978 error = ptrace_restart(PTRACE_CONT, tcp, sig);
980 /* Should not happen.
981 * Note: ptrace_restart returns 0 on ESRCH, so it's not it.
982 * ptrace_restart already emitted error message.
989 if (!qflag && (tcp->flags & TCB_ATTACHED))
990 error_msg("Process %u detached", tcp->pid);
996 process_opt_p_list(char *opt)
1000 * We accept -p PID,PID; -p "`pidof PROG`"; -p "`pgrep PROG`".
1001 * pidof uses space as delim, pgrep uses newline. :(
1004 char *delim = opt + strcspn(opt, ", \n\t");
1008 pid = string_to_uint(opt);
1010 error_msg_and_die("Invalid process id: '%s'", opt);
1012 if (pid == strace_tracer_pid) {
1013 error_msg_and_die("I'm sorry, I can't let you do that, Dave.");
1024 attach_tcb(struct tcb *const tcp)
1026 if (ptrace_attach_or_seize(tcp->pid) < 0) {
1027 perror_msg("attach: ptrace(%s, %d)",
1028 ptrace_attach_cmd, tcp->pid);
1033 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
1036 error_msg("attach to pid %d (main) succeeded", tcp->pid);
1038 char procdir[sizeof("/proc/%d/task") + sizeof(int) * 3];
1040 unsigned int ntid = 0, nerr = 0;
1042 if (followfork && tcp->pid != strace_child &&
1043 sprintf(procdir, "/proc/%d/task", tcp->pid) > 0 &&
1044 (dir = opendir(procdir)) != NULL) {
1047 while ((de = read_dir(dir)) != NULL) {
1048 if (de->d_fileno == 0)
1051 int tid = string_to_uint(de->d_name);
1052 if (tid <= 0 || tid == tcp->pid)
1056 if (ptrace_attach_or_seize(tid) < 0) {
1059 perror_msg("attach: ptrace(%s, %d)",
1060 ptrace_attach_cmd, tid);
1064 error_msg("attach to pid %d succeeded", tid);
1066 struct tcb *tid_tcp = alloctcb(tid);
1067 tid_tcp->flags |= TCB_ATTACHED | TCB_STARTUP |
1068 post_attach_sigstop;
1077 error_msg("Process %u attached"
1079 tcp->pid, ntid - nerr + 1);
1081 error_msg("Process %u attached",
1087 startup_attach(void)
1089 pid_t parent_pid = strace_tracer_pid;
1094 * Block user interruptions as we would leave the traced
1095 * process stopped (process state T) if we would terminate in
1096 * between PTRACE_ATTACH and wait4() on SIGSTOP.
1097 * We rely on cleanup() from this point on.
1100 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
1102 if (daemonized_tracer) {
1105 perror_msg_and_die("fork");
1107 if (pid) { /* parent */
1109 * Wait for grandchild to attach to straced process
1110 * (grandparent). Grandchild SIGKILLs us after it attached.
1111 * Grandparent's wait() is unblocked by our death,
1112 * it proceeds to exec the straced program.
1115 _exit(0); /* paranoia */
1118 /* We will be the tracer process. Remember our new pid: */
1119 strace_tracer_pid = getpid();
1122 for (tcbi = 0; tcbi < tcbtabsize; tcbi++) {
1128 /* Is this a process we should attach to, but not yet attached? */
1129 if (tcp->flags & TCB_ATTACHED)
1130 continue; /* no, we already attached it */
1132 if (tcp->pid == parent_pid || tcp->pid == strace_tracer_pid) {
1134 perror_msg("attach: pid %d", tcp->pid);
1142 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1145 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
1147 } /* for each tcbtab[] */
1149 if (daemonized_tracer) {
1151 * Make parent go away.
1152 * Also makes grandparent's wait() unblock.
1154 kill(parent_pid, SIGKILL);
1160 sigprocmask(SIG_SETMASK, &empty_set, NULL);
1163 /* Stack-o-phobic exec helper, in the hope to work around
1164 * NOMMU + "daemonized tracer" difficulty.
1166 struct exec_params {
1173 static struct exec_params params_for_tracee;
1175 static void ATTRIBUTE_NOINLINE ATTRIBUTE_NORETURN
1178 struct exec_params *params = ¶ms_for_tracee;
1180 if (params->fd_to_close >= 0)
1181 close(params->fd_to_close);
1182 if (!daemonized_tracer && !use_seize) {
1183 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0) {
1184 perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
1188 if (username != NULL) {
1190 * It is important to set groups before we
1191 * lose privileges on setuid.
1193 if (initgroups(username, run_gid) < 0) {
1194 perror_msg_and_die("initgroups");
1196 if (setregid(run_gid, params->run_egid) < 0) {
1197 perror_msg_and_die("setregid");
1199 if (setreuid(run_uid, params->run_euid) < 0) {
1200 perror_msg_and_die("setreuid");
1203 else if (geteuid() != 0)
1204 if (setreuid(run_uid, run_uid) < 0) {
1205 perror_msg_and_die("setreuid");
1208 if (!daemonized_tracer) {
1210 * Induce a ptrace stop. Tracer (our parent)
1211 * will resume us with PTRACE_SYSCALL and display
1212 * the immediately following execve syscall.
1213 * Can't do this on NOMMU systems, we are after
1214 * vfork: parent is blocked, stopping would deadlock.
1217 kill(getpid(), SIGSTOP);
1220 /* we depend on SIGCHLD set to SIG_DFL by init code */
1221 /* if it happens to be SIG_IGN'ed, wait won't block */
1226 execv(params->pathname, params->argv);
1227 perror_msg_and_die("exec");
1231 * Open a dummy descriptor for use as a placeholder.
1232 * The descriptor is O_RDONLY with FD_CLOEXEC flag set.
1233 * A read attempt from such descriptor ends with EOF,
1234 * a write attempt is rejected with EBADF.
1237 open_dummy_desc(void)
1242 perror_msg_and_die("pipe");
1244 set_cloexec_flag(fds[0]);
1248 /* placeholder fds status for stdin and stdout */
1249 static bool fd_is_placeholder[2];
1252 * Ensure that all standard file descriptors are open by opening placeholder
1253 * file descriptors for those standard file descriptors that are not open.
1255 * The information which descriptors have been made open is saved
1256 * in fd_is_placeholder for later use.
1259 ensure_standard_fds_opened(void)
1263 while ((fd = open_dummy_desc()) <= 2) {
1266 fd_is_placeholder[fd] = true;
1274 * Redirect stdin and stdout unless they have been opened earlier
1275 * by ensure_standard_fds_opened as placeholders.
1278 redirect_standard_fds(void)
1283 * It might be a good idea to redirect stderr as well,
1284 * but we sometimes need to print error messages.
1286 for (i = 0; i <= 1; ++i) {
1287 if (!fd_is_placeholder[i]) {
1295 startup_child(char **argv)
1297 struct_stat statbuf;
1298 const char *filename;
1299 size_t filename_len;
1300 char pathname[PATH_MAX];
1305 filename_len = strlen(filename);
1307 if (filename_len > sizeof(pathname) - 1) {
1308 errno = ENAMETOOLONG;
1309 perror_msg_and_die("exec");
1311 if (strchr(filename, '/')) {
1312 strcpy(pathname, filename);
1314 #ifdef USE_DEBUGGING_EXEC
1316 * Debuggers customarily check the current directory
1317 * first regardless of the path but doing that gives
1318 * security geeks a panic attack.
1320 else if (stat_file(filename, &statbuf) == 0)
1321 strcpy(pathname, filename);
1322 #endif /* USE_DEBUGGING_EXEC */
1327 for (path = getenv("PATH"); path && *path; path += m) {
1328 const char *colon = strchr(path, ':');
1334 m = n = strlen(path);
1336 if (!getcwd(pathname, PATH_MAX))
1338 len = strlen(pathname);
1340 else if (n > sizeof pathname - 1)
1343 strncpy(pathname, path, n);
1346 if (len && pathname[len - 1] != '/')
1347 pathname[len++] = '/';
1348 if (filename_len + len > sizeof(pathname) - 1)
1350 strcpy(pathname + len, filename);
1351 if (stat_file(pathname, &statbuf) == 0 &&
1352 /* Accept only regular files
1353 with some execute bits set.
1354 XXX not perfect, might still fail */
1355 S_ISREG(statbuf.st_mode) &&
1356 (statbuf.st_mode & 0111))
1359 if (!path || !*path)
1362 if (stat_file(pathname, &statbuf) < 0) {
1363 perror_msg_and_die("Can't stat '%s'", filename);
1366 params_for_tracee.fd_to_close = (shared_log != stderr) ? fileno(shared_log) : -1;
1367 params_for_tracee.run_euid = (statbuf.st_mode & S_ISUID) ? statbuf.st_uid : run_uid;
1368 params_for_tracee.run_egid = (statbuf.st_mode & S_ISGID) ? statbuf.st_gid : run_gid;
1369 params_for_tracee.argv = argv;
1371 * On NOMMU, can be safely freed only after execve in tracee.
1372 * It's hard to know when that happens, so we just leak it.
1374 params_for_tracee.pathname = NOMMU_SYSTEM ? xstrdup(pathname) : pathname;
1376 #if defined HAVE_PRCTL && defined PR_SET_PTRACER && defined PR_SET_PTRACER_ANY
1377 if (daemonized_tracer)
1378 prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
1383 perror_msg_and_die("fork");
1385 if ((pid != 0 && daemonized_tracer)
1386 || (pid == 0 && !daemonized_tracer)
1388 /* We are to become the tracee. Two cases:
1390 * not -D: we are child
1395 /* We are the tracer */
1397 if (!daemonized_tracer) {
1400 /* child did PTRACE_TRACEME, nothing to do in parent */
1402 if (!NOMMU_SYSTEM) {
1403 /* Wait until child stopped itself */
1405 while (waitpid(pid, &status, WSTOPPED) < 0) {
1408 perror_msg_and_die("waitpid");
1410 if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGSTOP) {
1411 kill_save_errno(pid, SIGKILL);
1412 perror_msg_and_die("Unexpected wait status %x", status);
1415 /* Else: NOMMU case, we have no way to sync.
1416 * Just attach to it as soon as possible.
1417 * This means that we may miss a few first syscalls...
1420 if (ptrace_attach_or_seize(pid)) {
1421 kill_save_errno(pid, SIGKILL);
1422 perror_msg_and_die("attach: ptrace(%s, %d)",
1423 ptrace_attach_cmd, pid);
1428 tcp = alloctcb(pid);
1429 tcp->flags |= TCB_ATTACHED | TCB_STARTUP
1430 | TCB_SKIP_DETACH_ON_FIRST_EXEC
1431 | (NOMMU_SYSTEM ? 0 : (TCB_HIDE_LOG | post_attach_sigstop));
1435 /* With -D, we are *child* here, the tracee is our parent. */
1436 strace_child = strace_tracer_pid;
1437 strace_tracer_pid = getpid();
1438 tcp = alloctcb(strace_child);
1439 tcp->flags |= TCB_SKIP_DETACH_ON_FIRST_EXEC | TCB_HIDE_LOG;
1440 /* attaching will be done later, by startup_attach */
1441 /* note: we don't do newoutf(tcp) here either! */
1443 /* NOMMU BUG! -D mode is active, we (child) return,
1444 * and we will scribble over parent's stack!
1445 * When parent later unpauses, it segfaults.
1448 * (1) by declaring exec_or_die() NORETURN,
1449 * hopefully compiler will just jump to it
1450 * instead of call (won't push anything to stack),
1451 * (2) by trying very hard in exec_or_die()
1452 * to not use any stack,
1453 * (3) having a really big (PATH_MAX) stack object
1454 * in this function, which creates a "buffer" between
1455 * child's and parent's stack pointers.
1456 * This may save us if (1) and (2) failed
1457 * and compiler decided to use stack in exec_or_die() anyway
1458 * (happens on i386 because of stack parameter passing).
1460 * A cleaner solution is to use makecontext + setcontext
1461 * to create a genuine separate stack and execute on it.
1465 * A case where straced process is part of a pipe:
1466 * { sleep 1; yes | head -n99999; } | strace -o/dev/null sh -c 'exec <&-; sleep 9'
1467 * If strace won't close its fd#0, closing it in tracee is not enough:
1468 * the pipe is still open, it has a reader. Thus, "head" will not get its
1469 * SIGPIPE at once, on the first write.
1471 * Preventing it by redirecting strace's stdin/out.
1472 * (Don't leave fds 0 and 1 closed, this is bad practice: future opens
1473 * will reuse them, unexpectedly making a newly opened object "stdin").
1475 redirect_standard_fds();
1480 test_ptrace_seize(void)
1484 /* Need fork for test. NOMMU has no forks */
1486 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1492 perror_msg_and_die("fork");
1499 /* PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After
1500 * attaching tracee continues to run unless a trap condition occurs.
1501 * PTRACE_SEIZE doesn't affect signal or group stop state.
1503 if (ptrace(PTRACE_SEIZE, pid, 0, 0) == 0) {
1504 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1505 } else if (debug_flag) {
1506 error_msg("PTRACE_SEIZE doesn't work");
1512 int status, tracee_pid;
1515 tracee_pid = waitpid(pid, &status, 0);
1516 if (tracee_pid <= 0) {
1519 perror_msg_and_die("%s: unexpected wait result %d",
1520 __func__, tracee_pid);
1522 if (WIFSIGNALED(status)) {
1525 error_msg_and_die("%s: unexpected wait status %x",
1529 #else /* !USE_SEIZE */
1530 # define test_ptrace_seize() ((void)0)
1534 get_os_release(void)
1540 perror_msg_and_die("uname");
1541 /* u.release has this form: "3.2.9[-some-garbage]" */
1545 if (!(*p >= '0' && *p <= '9'))
1546 error_msg_and_die("Bad OS release string: '%s'", u.release);
1547 /* Note: this open-codes KERNEL_VERSION(): */
1548 rel = (rel << 8) | atoi(p);
1549 if (rel >= KERNEL_VERSION(1,0,0))
1551 while (*p >= '0' && *p <= '9')
1554 if (rel >= KERNEL_VERSION(0,1,0)) {
1555 /* "X.Y-something" means "X.Y.0" */
1559 error_msg_and_die("Bad OS release string: '%s'", u.release);
1567 * Initialization part of main() was eating much stack (~0.5k),
1568 * which was unused after init.
1569 * We can reuse it if we move init code into a separate function.
1571 * Don't want main() to inline us and defeat the reason
1572 * we have a separate function.
1574 static void ATTRIBUTE_NOINLINE
1575 init(int argc, char *argv[])
1579 struct sigaction sa;
1581 progname = argv[0] ? argv[0] : "strace";
1583 /* Make sure SIGCHLD has the default action so that waitpid
1584 definitely works without losing track of children. The user
1585 should not have given us a bogus state to inherit, but he might
1586 have. Arguably we should detect SIG_IGN here and pass it on
1587 to children, but probably noone really needs that. */
1588 signal(SIGCHLD, SIG_DFL);
1590 strace_tracer_pid = getpid();
1592 os_release = get_os_release();
1594 shared_log = stderr;
1595 set_sortby(DEFAULT_SORTBY);
1596 set_personality(DEFAULT_PERSONALITY);
1597 qualify("trace=all");
1598 qualify("abbrev=all");
1599 qualify("verbose=all");
1600 #if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
1601 # error Bug in DEFAULT_QUAL_FLAGS
1603 qualify("signal=all");
1604 while ((c = getopt(argc, argv,
1605 "+b:cCdfFhiqrtTvVwxyz"
1606 #ifdef USE_LIBUNWIND
1610 "a:e:o:O:p:s:S:u:E:P:I:")) != EOF) {
1613 if (strcmp(optarg, "execve") != 0)
1614 error_msg_and_die("Syscall '%s' for -b isn't supported",
1616 detach_on_execve = 1;
1619 if (cflag == CFLAG_BOTH) {
1620 error_msg_and_help("-c and -C are mutually exclusive");
1622 cflag = CFLAG_ONLY_STATS;
1625 if (cflag == CFLAG_ONLY_STATS) {
1626 error_msg_and_help("-c and -C are mutually exclusive");
1634 daemonized_tracer = 1;
1661 count_wallclock = 1;
1670 qualify("abbrev=none");
1677 not_failing_only = 1;
1680 acolumn = string_to_uint(optarg);
1682 error_opt_arg(c, optarg);
1688 outfname = xstrdup(optarg);
1691 i = string_to_uint(optarg);
1693 error_opt_arg(c, optarg);
1697 process_opt_p_list(optarg);
1700 pathtrace_select(optarg);
1703 i = string_to_uint(optarg);
1705 error_opt_arg(c, optarg);
1712 username = xstrdup(optarg);
1714 #ifdef USE_LIBUNWIND
1716 stack_trace_enabled = true;
1720 if (putenv(optarg) < 0)
1721 die_out_of_memory();
1724 opt_intr = string_to_uint_upto(optarg, NUM_INTR_OPTS - 1);
1726 error_opt_arg(c, optarg);
1729 error_msg_and_help(NULL);
1734 /* argc -= optind; - no need, argc is not used below */
1736 acolumn_spaces = xmalloc(acolumn + 1);
1737 memset(acolumn_spaces, ' ', acolumn);
1738 acolumn_spaces[acolumn] = '\0';
1740 if (!argv[0] && !nprocs) {
1741 error_msg_and_help("must have PROG [ARGS] or -p PID");
1744 if (!argv[0] && daemonized_tracer) {
1745 error_msg_and_help("PROG [ARGS] must be specified with -D");
1751 if (followfork >= 2 && cflag) {
1752 error_msg_and_help("(-c or -C) and -ff are mutually exclusive");
1755 if (count_wallclock && !cflag) {
1756 error_msg_and_help("-w must be given with (-c or -C)");
1759 if (cflag == CFLAG_ONLY_STATS) {
1761 error_msg("-%c has no effect with -c", 'i');
1762 #ifdef USE_LIBUNWIND
1763 if (stack_trace_enabled)
1764 error_msg("-%c has no effect with -c", 'k');
1767 error_msg("-%c has no effect with -c", 'r');
1769 error_msg("-%c has no effect with -c", 't');
1771 error_msg("-%c has no effect with -c", 'T');
1773 error_msg("-%c has no effect with -c", 'y');
1778 error_msg("-tt has no effect with -r");
1782 #ifdef USE_LIBUNWIND
1783 if (stack_trace_enabled) {
1787 for (tcbi = 0; tcbi < tcbtabsize; ++tcbi) {
1788 unwind_tcb_init(tcbtab[tcbi]);
1793 /* See if they want to run as another user. */
1794 if (username != NULL) {
1795 struct passwd *pent;
1797 if (getuid() != 0 || geteuid() != 0) {
1798 error_msg_and_die("You must be root to use the -u option");
1800 pent = getpwnam(username);
1802 error_msg_and_die("Cannot find user '%s'", username);
1804 run_uid = pent->pw_uid;
1805 run_gid = pent->pw_gid;
1813 ptrace_setoptions |= PTRACE_O_TRACECLONE |
1814 PTRACE_O_TRACEFORK |
1815 PTRACE_O_TRACEVFORK;
1817 error_msg("ptrace_setoptions = %#x", ptrace_setoptions);
1818 test_ptrace_seize();
1821 * Is something weird with our stdin and/or stdout -
1822 * for example, may they be not open? In this case,
1823 * ensure that none of the future opens uses them.
1825 * This was seen in the wild when /proc/sys/kernel/core_pattern
1826 * was set to "|/bin/strace -o/tmp/LOG PROG":
1827 * kernel runs coredump helper with fd#0 open but fd#1 closed (!),
1828 * therefore LOG gets opened to fd#1, and fd#1 is closed by
1829 * "don't hold up stdin/out open" code soon after.
1831 ensure_standard_fds_opened();
1833 /* Check if they want to redirect the output. */
1835 /* See if they want to pipe the output. */
1836 if (outfname[0] == '|' || outfname[0] == '!') {
1838 * We can't do the <outfname>.PID funny business
1839 * when using popen, so prohibit it.
1841 if (followfork >= 2)
1842 error_msg_and_help("piping the output and -ff are mutually exclusive");
1843 shared_log = strace_popen(outfname + 1);
1845 else if (followfork < 2)
1846 shared_log = strace_fopen(outfname);
1848 /* -ff without -o FILE is the same as single -f */
1849 if (followfork >= 2)
1853 if (!outfname || outfname[0] == '|' || outfname[0] == '!') {
1854 setvbuf(shared_log, NULL, _IOLBF, 0);
1856 if (outfname && argv[0]) {
1858 opt_intr = INTR_NEVER;
1863 opt_intr = INTR_WHILE_WAIT;
1865 /* argv[0] -pPID -oFILE Default interactive setting
1866 * yes * 0 INTR_WHILE_WAIT
1867 * no 1 0 INTR_WHILE_WAIT
1868 * yes * 1 INTR_NEVER
1869 * no 1 1 INTR_WHILE_WAIT
1872 sigemptyset(&empty_set);
1873 sigemptyset(&blocked_set);
1875 /* startup_child() must be called before the signal handlers get
1876 * installed below as they are inherited into the spawned process.
1877 * Also we do not need to be protected by them as during interruption
1878 * in the startup_child() mode we kill the spawned process anyway.
1881 startup_child(argv);
1884 sa.sa_handler = SIG_IGN;
1885 sigemptyset(&sa.sa_mask);
1887 sigaction(SIGTTOU, &sa, NULL); /* SIG_IGN */
1888 sigaction(SIGTTIN, &sa, NULL); /* SIG_IGN */
1889 if (opt_intr != INTR_ANYWHERE) {
1890 if (opt_intr == INTR_BLOCK_TSTP_TOO)
1891 sigaction(SIGTSTP, &sa, NULL); /* SIG_IGN */
1893 * In interactive mode (if no -o OUTFILE, or -p PID is used),
1894 * fatal signals are blocked while syscall stop is processed,
1895 * and acted on in between, when waiting for new syscall stops.
1896 * In non-interactive mode, signals are ignored.
1898 if (opt_intr == INTR_WHILE_WAIT) {
1899 sigaddset(&blocked_set, SIGHUP);
1900 sigaddset(&blocked_set, SIGINT);
1901 sigaddset(&blocked_set, SIGQUIT);
1902 sigaddset(&blocked_set, SIGPIPE);
1903 sigaddset(&blocked_set, SIGTERM);
1904 sa.sa_handler = interrupt;
1906 /* SIG_IGN, or set handler for these */
1907 sigaction(SIGHUP, &sa, NULL);
1908 sigaction(SIGINT, &sa, NULL);
1909 sigaction(SIGQUIT, &sa, NULL);
1910 sigaction(SIGPIPE, &sa, NULL);
1911 sigaction(SIGTERM, &sa, NULL);
1913 if (nprocs != 0 || daemonized_tracer)
1916 /* Do we want pids printed in our -o OUTFILE?
1917 * -ff: no (every pid has its own file); or
1918 * -f: yes (there can be more pids in the future); or
1919 * -p PID1,PID2: yes (there are already more than one pid)
1921 print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
1932 for (i = 0; i < tcbtabsize; i++) {
1933 struct tcb *tcp = tcbtab[i];
1934 if (tcp->pid == pid)
1948 /* 'interrupted' is a volatile object, fetch it only once */
1949 fatal_sig = interrupted;
1951 fatal_sig = SIGTERM;
1953 for (i = 0; i < tcbtabsize; i++) {
1958 error_msg("cleanup: looking at pid %u", tcp->pid);
1959 if (tcp->pid == strace_child) {
1960 kill(tcp->pid, SIGCONT);
1961 kill(tcp->pid, fatal_sig);
1966 call_summary(shared_log);
1976 print_debug_info(const int pid, int status)
1978 const unsigned int event = (unsigned int) status >> 16;
1979 char buf[sizeof("WIFEXITED,exitcode=%u") + sizeof(int)*3 /*paranoia:*/ + 16];
1980 char evbuf[sizeof(",EVENT_VFORK_DONE (%u)") + sizeof(int)*3 /*paranoia:*/ + 16];
1983 if (WIFSIGNALED(status))
1985 sprintf(buf, "WIFSIGNALED,%ssig=%s",
1986 WCOREDUMP(status) ? "core," : "",
1987 signame(WTERMSIG(status)));
1989 sprintf(buf, "WIFSIGNALED,sig=%s",
1990 signame(WTERMSIG(status)));
1992 if (WIFEXITED(status))
1993 sprintf(buf, "WIFEXITED,exitcode=%u", WEXITSTATUS(status));
1994 if (WIFSTOPPED(status))
1995 sprintf(buf, "WIFSTOPPED,sig=%s", signame(WSTOPSIG(status)));
1997 /* Should never be seen */
1998 if (WIFCONTINUED(status))
1999 strcpy(buf, "WIFCONTINUED");
2003 static const char *const event_names[] = {
2004 [PTRACE_EVENT_CLONE] = "CLONE",
2005 [PTRACE_EVENT_FORK] = "FORK",
2006 [PTRACE_EVENT_VFORK] = "VFORK",
2007 [PTRACE_EVENT_VFORK_DONE] = "VFORK_DONE",
2008 [PTRACE_EVENT_EXEC] = "EXEC",
2009 [PTRACE_EVENT_EXIT] = "EXIT",
2010 /* [PTRACE_EVENT_STOP (=128)] would make biggish array */
2012 const char *e = "??";
2013 if (event < ARRAY_SIZE(event_names))
2014 e = event_names[event];
2015 else if (event == PTRACE_EVENT_STOP)
2017 sprintf(evbuf, ",EVENT_%s (%u)", e, event);
2019 error_msg("[wait(0x%06x) = %u] %s%s", status, pid, buf, evbuf);
2023 maybe_allocate_tcb(const int pid, int status)
2025 if (!WIFSTOPPED(status)) {
2026 if (detach_on_execve && pid == strace_child) {
2027 /* example: strace -bexecve sh -c 'exec true' */
2032 * This can happen if we inherited an unknown child.
2033 * Example: (sleep 1 & exec strace true)
2035 error_msg("Exit of unknown pid %u ignored", pid);
2039 /* We assume it's a fork/vfork/clone child */
2040 struct tcb *tcp = alloctcb(pid);
2041 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
2044 error_msg("Process %d attached", pid);
2047 /* This can happen if a clone call used
2048 * CLONE_PTRACE itself.
2050 ptrace(PTRACE_CONT, pid, NULL, 0);
2051 error_msg("Stop of unknown pid %u seen, PTRACE_CONTed it", pid);
2057 maybe_switch_tcbs(struct tcb *tcp, const int pid)
2060 struct tcb *execve_thread;
2063 if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, &old_pid) < 0)
2065 /* Avoid truncation in pid2tcb() param passing */
2066 if (old_pid <= 0 || old_pid == pid)
2068 if ((unsigned long) old_pid > UINT_MAX)
2070 execve_thread = pid2tcb(old_pid);
2071 /* It should be !NULL, but I feel paranoid */
2075 if (execve_thread->curcol != 0) {
2077 * One case we are here is -ff:
2078 * try "strace -oLOG -ff test/threaded_execve"
2080 fprintf(execve_thread->outf, " <pid changed to %d ...>\n", pid);
2081 /*execve_thread->curcol = 0; - no need, see code below */
2083 /* Swap output FILEs (needed for -ff) */
2084 fp = execve_thread->outf;
2085 execve_thread->outf = tcp->outf;
2087 /* And their column positions */
2088 execve_thread->curcol = tcp->curcol;
2090 /* Drop leader, but close execve'd thread outfile (if -ff) */
2092 /* Switch to the thread, reusing leader's outfile and pid */
2093 tcp = execve_thread;
2095 if (cflag != CFLAG_ONLY_STATS) {
2097 tprintf("+++ superseded by execve in pid %lu +++\n", old_pid);
2099 tcp->flags |= TCB_REPRINT;
2106 print_signalled(struct tcb *tcp, const int pid, int status)
2108 if (pid == strace_child) {
2109 exit_code = 0x100 | WTERMSIG(status);
2113 if (cflag != CFLAG_ONLY_STATS
2114 && is_number_in_set(WTERMSIG(status), &signal_set)) {
2117 tprintf("+++ killed by %s %s+++\n",
2118 signame(WTERMSIG(status)),
2119 WCOREDUMP(status) ? "(core dumped) " : "");
2121 tprintf("+++ killed by %s +++\n",
2122 signame(WTERMSIG(status)));
2129 print_exited(struct tcb *tcp, const int pid, int status)
2131 if (pid == strace_child) {
2132 exit_code = WEXITSTATUS(status);
2136 if (cflag != CFLAG_ONLY_STATS &&
2139 tprintf("+++ exited with %d +++\n", WEXITSTATUS(status));
2145 print_stopped(struct tcb *tcp, const siginfo_t *si, const unsigned int sig)
2147 if (cflag != CFLAG_ONLY_STATS
2149 && is_number_in_set(sig, &signal_set)) {
2152 tprintf("--- %s ", signame(sig));
2156 tprintf("--- stopped by %s ---\n", signame(sig));
2162 startup_tcb(struct tcb *tcp)
2165 error_msg("pid %d has TCB_STARTUP, initializing it", tcp->pid);
2167 tcp->flags &= ~TCB_STARTUP;
2171 error_msg("setting opts 0x%x on pid %d",
2172 ptrace_setoptions, tcp->pid);
2173 if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, ptrace_setoptions) < 0) {
2174 if (errno != ESRCH) {
2175 /* Should never happen, really */
2176 perror_msg_and_die("PTRACE_SETOPTIONS");
2183 print_event_exit(struct tcb *tcp)
2185 if (entering(tcp) || filtered(tcp) || hide_log(tcp)
2186 || cflag == CFLAG_ONLY_STATS) {
2190 if (followfork < 2 && printing_tcp && printing_tcp != tcp
2191 && printing_tcp->curcol != 0) {
2192 current_tcp = printing_tcp;
2193 tprints(" <unfinished ...>\n");
2194 fflush(printing_tcp->outf);
2195 printing_tcp->curcol = 0;
2199 if ((followfork < 2 && printing_tcp != tcp)
2200 || (tcp->flags & TCB_REPRINT)) {
2201 tcp->flags &= ~TCB_REPRINT;
2203 tprintf("<... %s resumed>", tcp->s_ent->sys_name);
2206 if (!(tcp->sys_func_rval & RVAL_DECODED)) {
2208 * The decoder has probably decided to print something
2209 * on exiting syscall which is not going to happen.
2211 tprints(" <unfinished ...>");
2219 /* Returns true iff the main trace loop has to continue. */
2236 * Used to exit simply when nprocs hits zero, but in this testcase:
2237 * int main() { _exit(!!fork()); }
2238 * under strace -f, parent sometimes (rarely) manages
2239 * to exit before we see the first stop of the child,
2240 * and we are losing track of it:
2241 * 19923 clone(...) = 19924
2242 * 19923 exit_group(1) = ?
2243 * 19923 +++ exited with 1 +++
2244 * Exiting only when wait() returns ECHILD works better.
2246 if (popen_pid != 0) {
2247 /* However, if -o|logger is in use, we can't do that.
2248 * Can work around that by double-forking the logger,
2249 * but that loses the ability to wait for its completion
2250 * on exit. Oh well...
2257 sigprocmask(SIG_SETMASK, &empty_set, NULL);
2258 pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
2261 sigprocmask(SIG_BLOCK, &blocked_set, NULL);
2264 if (wait_errno == EINTR)
2266 if (nprocs == 0 && wait_errno == ECHILD)
2269 * If nprocs > 0, ECHILD is not expected,
2270 * treat it as any other error here:
2273 perror_msg_and_die("wait4(__WALL)");
2276 if (pid == popen_pid) {
2277 if (!WIFSTOPPED(status))
2283 print_debug_info(pid, status);
2285 /* Look up 'pid' in our table. */
2289 tcp = maybe_allocate_tcb(pid, status);
2294 if (WIFSTOPPED(status))
2299 event = (unsigned int) status >> 16;
2301 if (event == PTRACE_EVENT_EXEC) {
2303 * Under Linux, execve changes pid to thread leader's pid,
2304 * and we see this changed pid on EVENT_EXEC and later,
2305 * execve sysexit. Leader "disappears" without exit
2306 * notification. Let user know that, drop leader's tcb,
2307 * and fix up pid in execve thread's tcb.
2308 * Effectively, execve thread's tcb replaces leader's tcb.
2310 * BTW, leader is 'stuck undead' (doesn't report WIFEXITED
2311 * on exit syscall) in multithreaded programs exactly
2312 * in order to handle this case.
2314 * PTRACE_GETEVENTMSG returns old pid starting from Linux 3.0.
2315 * On 2.6 and earlier, it can return garbage.
2317 if (os_release >= KERNEL_VERSION(3,0,0))
2318 tcp = maybe_switch_tcbs(tcp, pid);
2320 if (detach_on_execve) {
2321 if (tcp->flags & TCB_SKIP_DETACH_ON_FIRST_EXEC) {
2322 tcp->flags &= ~TCB_SKIP_DETACH_ON_FIRST_EXEC;
2324 detach(tcp); /* do "-b execve" thingy */
2330 /* Set current output file */
2334 tv_sub(&tcp->dtime, &ru.ru_stime, &tcp->stime);
2335 tcp->stime = ru.ru_stime;
2338 if (WIFSIGNALED(status)) {
2339 print_signalled(tcp, pid, status);
2344 if (WIFEXITED(status)) {
2345 print_exited(tcp, pid, status);
2350 if (!WIFSTOPPED(status)) {
2352 * Neither signalled, exited or stopped.
2353 * How could that be?
2355 error_msg("pid %u not stopped!", pid);
2360 /* Is this the very first time we see this tracee stopped? */
2361 if (tcp->flags & TCB_STARTUP) {
2363 if (get_scno(tcp) == 1)
2364 tcp->s_prev_ent = tcp->s_ent;
2367 sig = WSTOPSIG(status);
2372 case PTRACE_EVENT_EXIT:
2373 print_event_exit(tcp);
2374 goto restart_tracee_with_sig_0;
2376 case PTRACE_EVENT_STOP:
2378 * PTRACE_INTERRUPT-stop or group-stop.
2379 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
2392 goto restart_tracee_with_sig_0;
2396 * Is this post-attach SIGSTOP?
2397 * Interestingly, the process may stop
2398 * with STOPSIG equal to some other signal
2399 * than SIGSTOP if we happend to attach
2400 * just before the process takes a signal.
2402 if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
2404 error_msg("ignored SIGSTOP on pid %d", tcp->pid);
2405 tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
2406 goto restart_tracee_with_sig_0;
2409 if (sig != syscall_trap_sig) {
2413 * True if tracee is stopped by signal
2414 * (as opposed to "tracee received signal").
2415 * TODO: shouldn't we check for errno == EINVAL too?
2416 * We can get ESRCH instead, you know...
2418 stopped = ptrace(PTRACE_GETSIGINFO, pid, 0, &si) < 0;
2422 print_stopped(tcp, stopped ? NULL : &si, sig);
2425 /* It's signal-delivery-stop. Inject the signal */
2426 goto restart_tracee;
2428 /* It's group-stop */
2431 * This ends ptrace-stop, but does *not* end group-stop.
2432 * This makes stopping signals work properly on straced process
2433 * (that is, process really stops. It used to continue to run).
2435 if (ptrace_restart(PTRACE_LISTEN, tcp, 0) < 0) {
2436 /* Note: ptrace_restart emitted error message */
2442 /* We don't have PTRACE_LISTEN support... */
2443 goto restart_tracee;
2446 /* We handled quick cases, we are permitted to interrupt now. */
2451 * This should be syscall entry or exit.
2455 if (trace_syscall(tcp, &sig) < 0) {
2457 * ptrace() failed in trace_syscall().
2458 * Likely a result of process disappearing mid-flight.
2459 * Observed case: exit_group() or SIGKILL terminating
2460 * all processes in thread group.
2461 * We assume that ptrace error was caused by process death.
2462 * We used to detach(tcp) here, but since we no longer
2463 * implement "detach before death" policy/hack,
2464 * we can let this process to report its death to us
2465 * normally, via WIFEXITED or WIFSIGNALED wait status.
2469 goto restart_tracee;
2471 restart_tracee_with_sig_0:
2475 if (ptrace_restart(PTRACE_SYSCALL, tcp, sig) < 0) {
2476 /* Note: ptrace_restart emitted error message */
2485 main(int argc, char *argv[])
2489 exit_code = !nprocs;
2496 if (shared_log != stderr)
2499 while (waitpid(popen_pid, NULL, 0) < 0 && errno == EINTR)
2502 if (exit_code > 0xff) {
2503 /* Avoid potential core file clobbering. */
2504 struct_rlimit rlim = {0, 0};
2505 set_rlimit(RLIMIT_CORE, &rlim);
2507 /* Child was killed by a signal, mimic that. */
2509 signal(exit_code, SIG_DFL);
2511 /* Paranoia - what if this signal is not fatal?
2512 Exit with 128 + signo then. */