2 * Copyright (c) 1991, 1992 Paul Kranenburg <pk@cs.few.eur.nl>
3 * Copyright (c) 1993 Branko Lankester <branko@hacktic.nl>
4 * Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <jrs@world.std.com>
5 * Copyright (c) 1996-1999 Wichert Akkerman <wichert@cistron.nl>
6 * Copyright (c) 1999-2018 The strace developers.
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. The name of the author may not be used to endorse or promote products
18 * derived from this software without specific prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
21 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
22 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
23 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
25 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
29 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
38 #include <sys/resource.h>
48 #include <sys/utsname.h>
50 # include <sys/prctl.h>
52 #include <asm/unistd.h>
54 #include "largefile_wrappers.h"
55 #include "mmap_cache.h"
56 #include "number_set.h"
58 #include "printsiginfo.h"
59 #include "trace_event.h"
63 /* In some libc, these aren't declared. Do it ourself: */
64 extern char **environ;
68 #ifdef ENABLE_STACKTRACE
69 /* if this is true do the stack trace for every system call */
70 bool stack_trace_enabled;
73 #define my_tkill(tid, sig) syscall(__NR_tkill, (tid), (sig))
75 /* Glue for systems without a MMU that cannot provide fork() */
76 #if !defined(HAVE_FORK)
78 # define NOMMU_SYSTEM 1
81 # define fork() vfork()
84 const unsigned int syscall_trap_sig = SIGTRAP | 0x80;
86 cflag_t cflag = CFLAG_NONE;
87 unsigned int followfork;
88 unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC
96 static unsigned int tflag;
98 static bool print_pid_pfx;
103 INTR_ANYWHERE = 1, /* don't block/ignore any signals */
104 INTR_WHILE_WAIT = 2, /* block fatal signals while decoding syscall. default */
105 INTR_NEVER = 3, /* block fatal signals. default if '-o FILE PROG' */
106 INTR_BLOCK_TSTP_TOO = 4, /* block fatal signals and SIGTSTP (^Z) */
110 /* We play with signal mask only if this mode is active: */
111 #define interactive (opt_intr == INTR_WHILE_WAIT)
114 * daemonized_tracer supports -D option.
115 * With this option, strace forks twice.
116 * Unlike normal case, with -D *grandparent* process exec's,
117 * becoming a traced process. Child exits (this prevents traced process
118 * from having children it doesn't expect to have), and grandchild
119 * attaches to grandparent similarly to strace -p PID.
120 * This allows for more transparent interaction in cases
121 * when process and its parent are communicating via signals,
122 * wait() etc. Without -D, strace process gets lodged in between,
123 * disrupting parent<->child link.
125 static bool daemonized_tracer;
127 static int post_attach_sigstop = TCB_IGNORE_ONE_SIGSTOP;
128 #define use_seize (post_attach_sigstop == 0)
130 /* Sometimes we want to print only succeeding syscalls. */
131 bool not_failing_only;
133 /* Show path associated with fd arguments */
134 unsigned int show_fd_path;
136 static bool detach_on_execve;
138 static int exit_code;
139 static int strace_child;
140 static int strace_tracer_pid;
142 static const char *username;
143 static uid_t run_uid;
144 static gid_t run_gid;
146 unsigned int max_strlen = DEFAULT_STRLEN;
147 static int acolumn = DEFAULT_ACOLUMN;
148 static char *acolumn_spaces;
150 /* Default output style for xlat entities */
151 enum xlat_style xlat_verbosity = XLAT_STYLE_ABBREV;
153 static const char *outfname;
154 /* If -ff, points to stderr. Else, it's our common output log */
155 static FILE *shared_log;
156 static bool open_append;
158 struct tcb *printing_tcp;
159 static struct tcb *current_tcp;
161 static struct tcb **tcbtab;
162 static unsigned int nprocs;
163 static size_t tcbtabsize;
165 #ifndef HAVE_PROGRAM_INVOCATION_NAME
166 char *program_invocation_name;
169 unsigned os_release; /* generated from uname()'s u.release */
171 static void detach(struct tcb *tcp);
172 static void cleanup(void);
173 static void interrupt(int sig);
175 #ifdef HAVE_SIG_ATOMIC_T
176 static volatile sig_atomic_t interrupted, restart_failed;
178 static volatile int interrupted, restart_failed;
181 static sigset_t timer_set;
182 static void timer_sighandler(int);
184 #ifndef HAVE_STRERROR
186 #if !HAVE_DECL_SYS_ERRLIST
188 extern char *sys_errlist[];
194 static char buf[sizeof("Unknown error %d") + sizeof(int)*3];
196 if (err_no < 1 || err_no >= sys_nerr) {
197 xsprintf(buf, "Unknown error %d", err_no);
200 return sys_errlist[err_no];
203 #endif /* HAVE_STERRROR */
208 static const char features[] =
209 #ifdef ENABLE_STACKTRACE
210 " stack-trace=" USE_UNWINDER
215 #if SUPPORTED_PERSONALITIES > 1
216 # if defined HAVE_M32_MPERS
221 #endif /* SUPPORTED_PERSONALITIES > 1 */
222 #if SUPPORTED_PERSONALITIES > 2
223 # if defined HAVE_MX32_MPERS
228 #endif /* SUPPORTED_PERSONALITIES > 2 */
231 printf("%s -- version %s\n"
232 "Copyright (c) 1991-%s The strace developers <%s>.\n"
233 "This is free software; see the source for copying conditions. There is NO\n"
234 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n",
235 PACKAGE_NAME, PACKAGE_VERSION, COPYRIGHT_YEAR, PACKAGE_URL);
236 printf("\nOptional features enabled:%s\n",
237 features[0] ? features : " (none)");
244 usage: strace [-CdffhiqrtttTvVwxxy] [-I n] [-e expr]...\n\
245 [-a column] [-o file] [-s strsize] [-P path]...\n\
246 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
247 or: strace -c[dfw] [-I n] [-e expr]... [-O overhead] [-S sortby]\n\
248 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
251 -a column alignment COLUMN for printing syscall results (default %d)\n\
252 -i print instruction pointer at time of syscall\n\
254 #ifdef ENABLE_STACKTRACE
256 -k obtain stack trace between each syscall\n\
260 -o file send trace output to FILE instead of stderr\n\
261 -q suppress messages about attaching, detaching, etc.\n\
262 -r print relative timestamp\n\
263 -s strsize limit length of print strings to STRSIZE chars (default %d)\n\
264 -t print absolute timestamp\n\
265 -tt print absolute timestamp with usecs\n\
266 -T print time spent in each syscall\n\
267 -x print non-ascii strings in hex\n\
268 -xx print all strings in hex\n\
269 -y print paths associated with file descriptor arguments\n\
270 -yy print protocol specific information associated with socket file descriptors\n\
273 -c count time, calls, and errors for each syscall and report summary\n\
274 -C like -c but also print regular output\n\
275 -O overhead set overhead for tracing syscalls to OVERHEAD usecs\n\
276 -S sortby sort syscall counts by: time, calls, name, nothing (default %s)\n\
277 -w summarise syscall latency (default is system time)\n\
280 -e expr a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
281 options: trace, abbrev, verbose, raw, signal, read, write, fault\n\
282 -P path trace accesses to path\n\
285 -b execve detach on execve syscall\n\
286 -D run tracer process as a detached grandchild, not as parent\n\
288 -ff follow forks with output into separate files\n\
290 1: no signals are blocked\n\
291 2: fatal signals are blocked while decoding syscall (default)\n\
292 3: fatal signals are always blocked (default if '-o FILE PROG')\n\
293 4: fatal signals and SIGTSTP (^Z) are always blocked\n\
294 (useful to make 'strace -o FILE PROG' not stop on ^Z)\n\
297 -E var remove var from the environment for command\n\
298 -E var=val put var=val in the environment for command\n\
299 -p pid trace process with process id PID, may be repeated\n\
300 -u username run command as username handling setuid and/or setgid\n\
303 -d enable debug output to stderr\n\
304 -v verbose mode: print unabbreviated argv, stat, termios, etc. args\n\
305 -h print help message\n\
308 /* ancient, no one should use it
309 -F -- attempt to follow vforks (deprecated, use -f)\n\
311 /* this is broken, so don't document it
312 -z -- print only succeeding syscalls\n\
314 , DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
318 void ATTRIBUTE_NORETURN
321 if (strace_tracer_pid == getpid()) {
331 error_opt_arg(int opt, const char *arg)
333 error_msg_and_help("invalid -%c argument: '%s'", opt, arg);
336 static const char *ptrace_attach_cmd;
339 ptrace_attach_or_seize(int pid)
343 return ptrace_attach_cmd = "PTRACE_ATTACH",
344 ptrace(PTRACE_ATTACH, pid, 0L, 0L);
345 r = ptrace(PTRACE_SEIZE, pid, 0L, (unsigned long) ptrace_setoptions);
347 return ptrace_attach_cmd = "PTRACE_SEIZE", r;
348 r = ptrace(PTRACE_INTERRUPT, pid, 0L, 0L);
349 return ptrace_attach_cmd = "PTRACE_INTERRUPT", r;
353 * Used when we want to unblock stopped traced process.
354 * Should be only used with PTRACE_CONT, PTRACE_DETACH and PTRACE_SYSCALL.
355 * Returns 0 on success or if error was ESRCH
356 * (presumably process was killed while we talk to it).
357 * Otherwise prints error message and returns -1.
360 ptrace_restart(const unsigned int op, struct tcb *const tcp, unsigned int sig)
366 ptrace(op, tcp->pid, 0L, (unsigned long) sig);
386 * Why curcol != 0? Otherwise sometimes we get this:
388 * 10252 kill(10253, SIGKILL) = 0
389 * <ptrace(SYSCALL,10252):No such process>10253 ...next decode...
391 * 10252 died after we retrieved syscall exit data,
392 * but before we tried to restart it. Log looks ugly.
394 if (current_tcp && current_tcp->curcol != 0) {
395 tprintf(" <ptrace(%s):%s>\n", msg, strerror(err));
401 perror_msg("ptrace(PTRACE_%s,pid:%d,sig:%u)", msg, tcp->pid, sig);
406 set_cloexec_flag(int fd)
410 flags = fcntl(fd, F_GETFD);
412 /* Can happen only if fd is bad.
413 * Should never happen: if it does, we have a bug
414 * in the caller. Therefore we just abort
415 * instead of propagating the error.
417 perror_msg_and_die("fcntl(%d, F_GETFD)", fd);
420 newflags = flags | FD_CLOEXEC;
421 if (flags == newflags)
424 if (fcntl(fd, F_SETFD, newflags)) /* never fails */
425 perror_msg_and_die("fcntl(%d, F_SETFD, %#x)", fd, newflags);
429 kill_save_errno(pid_t pid, int sig)
431 int saved_errno = errno;
433 (void) kill(pid, sig);
438 * When strace is setuid executable, we have to swap uids
439 * before and after filesystem and process management operations.
444 int euid = geteuid(), uid = getuid();
446 if (euid != uid && setreuid(euid, uid) < 0) {
447 perror_msg_and_die("setreuid");
452 strace_fopen(const char *path)
457 fp = fopen_stream(path, open_append ? "a" : "w");
459 perror_msg_and_die("Can't fopen '%s'", path);
461 set_cloexec_flag(fileno(fp));
465 static int popen_pid;
468 # define _PATH_BSHELL "/bin/sh"
472 * We cannot use standard popen(3) here because we have to distinguish
473 * popen child process from other processes we trace, and standard popen(3)
474 * does not export its child's pid.
477 strace_popen(const char *command)
485 perror_msg_and_die("pipe");
487 set_cloexec_flag(fds[1]); /* never fails */
491 perror_msg_and_die("vfork");
498 perror_msg_and_die("dup2");
501 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
502 perror_msg_and_die("Can't execute '%s'", _PATH_BSHELL);
509 fp = fdopen(fds[1], "w");
511 perror_msg_and_die("fdopen");
516 outf_perror(const struct tcb * const tcp)
518 if (tcp->outf == stderr)
521 /* This is ugly, but we don't store separate file names */
523 perror_msg("%s.%u", outfname, tcp->pid);
525 perror_msg("%s", outfname);
528 ATTRIBUTE_FORMAT((printf, 1, 0))
530 tvprintf(const char *const fmt, va_list args)
533 int n = vfprintf(current_tcp->outf, fmt, args);
535 /* very unlikely due to vfprintf buffering */
536 outf_perror(current_tcp);
538 current_tcp->curcol += n;
543 tprintf(const char *fmt, ...)
551 #ifndef HAVE_FPUTS_UNLOCKED
552 # define fputs_unlocked fputs
556 tprints(const char *str)
559 int n = fputs_unlocked(str, current_tcp->outf);
561 current_tcp->curcol += strlen(str);
564 /* very unlikely due to fputs_unlocked buffering */
565 outf_perror(current_tcp);
570 tprints_comment(const char *const str)
573 tprintf(" /* %s */", str);
577 tprintf_comment(const char *fmt, ...)
591 flush_tcp_output(const struct tcb *const tcp)
593 if (fflush(tcp->outf))
601 current_tcp->curcol = 0;
602 flush_tcp_output(current_tcp);
605 printing_tcp->curcol = 0;
611 set_current_tcp(const struct tcb *tcp)
613 current_tcp = (struct tcb *) tcp;
615 /* Sync current_personality and stuff */
617 set_personality(current_tcp->currpers);
621 printleader(struct tcb *tcp)
623 /* If -ff, "previous tcb we printed" is always the same as current,
624 * because we have per-tcb output files.
630 set_current_tcp(printing_tcp);
631 if (printing_tcp->curcol != 0 && (followfork < 2 || printing_tcp == tcp)) {
633 * case 1: we have a shared log (i.e. not -ff), and last line
634 * wasn't finished (same or different tcb, doesn't matter).
635 * case 2: split log, we are the same tcb, but our last line
636 * didn't finish ("SIGKILL nuked us after syscall entry" etc).
638 tprints(" <unfinished ...>\n");
639 printing_tcp->curcol = 0;
644 set_current_tcp(tcp);
645 current_tcp->curcol = 0;
648 tprintf("%-5d ", tcp->pid);
649 else if (nprocs > 1 && !outfname)
650 tprintf("[pid %5u] ", tcp->pid);
654 clock_gettime(CLOCK_REALTIME, &ts);
657 tprintf("%lld.%06ld ",
658 (long long) ts.tv_sec, (long) ts.tv_nsec / 1000);
660 time_t local = ts.tv_sec;
661 char str[MAX(sizeof("HH:MM:SS"), sizeof(ts.tv_sec) * 3)];
662 struct tm *tm = localtime(&local);
665 strftime(str, sizeof(str), "%T", tm);
667 xsprintf(str, "%lld", (long long) local);
670 str, (long) ts.tv_nsec / 1000);
678 clock_gettime(CLOCK_MONOTONIC, &ts);
680 static struct timespec ots;
685 ts_sub(&dts, &ts, &ots);
688 tprintf("%s%6ld.%06ld%s ",
690 (long) dts.tv_sec, (long) dts.tv_nsec / 1000,
701 if (current_tcp->curcol < acolumn)
702 tprints(acolumn_spaces + current_tcp->curcol);
705 /* Should be only called directly *after successful attach* to a tracee.
706 * Otherwise, "strace -oFILE -ff -p<nonexistant_pid>"
707 * may create bogus empty FILE.<nonexistant_pid>, and then die.
710 after_successful_attach(struct tcb *tcp, const unsigned int flags)
712 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | flags;
713 tcp->outf = shared_log; /* if not -ff mode, the same file is for all */
714 if (followfork >= 2) {
716 xsprintf(name, "%s.%u", outfname, tcp->pid);
717 tcp->outf = strace_fopen(name);
720 #ifdef ENABLE_STACKTRACE
721 if (stack_trace_enabled)
722 unwind_tcb_init(tcp);
729 /* Allocate some (more) TCBs (and expand the table).
730 We don't want to relocate the TCBs because our
731 callers have pointers and it would be a pain.
732 So tcbtab is a table of pointers. Since we never
733 free the TCBs, we allocate a single chunk of many. */
734 size_t old_tcbtabsize;
736 struct tcb **tcb_ptr;
738 old_tcbtabsize = tcbtabsize;
740 tcbtab = xgrowarray(tcbtab, &tcbtabsize, sizeof(tcbtab[0]));
741 newtcbs = xcalloc(tcbtabsize - old_tcbtabsize, sizeof(newtcbs[0]));
743 for (tcb_ptr = tcbtab + old_tcbtabsize;
744 tcb_ptr < tcbtab + tcbtabsize; tcb_ptr++, newtcbs++)
754 if (nprocs == tcbtabsize)
757 for (i = 0; i < tcbtabsize; i++) {
760 memset(tcp, 0, sizeof(*tcp));
762 #if SUPPORTED_PERSONALITIES > 1
763 tcp->currpers = current_personality;
766 debug_msg("new tcb for pid %d, active tcbs:%d",
771 error_msg_and_die("bug in alloctcb");
775 get_tcb_priv_data(const struct tcb *tcp)
777 return tcp->_priv_data;
781 set_tcb_priv_data(struct tcb *tcp, void *const priv_data,
782 void (*const free_priv_data)(void *))
787 tcp->_free_priv_data = free_priv_data;
788 tcp->_priv_data = priv_data;
794 free_tcb_priv_data(struct tcb *tcp)
796 if (tcp->_priv_data) {
797 if (tcp->_free_priv_data) {
798 tcp->_free_priv_data(tcp->_priv_data);
799 tcp->_free_priv_data = NULL;
801 tcp->_priv_data = NULL;
806 droptcb(struct tcb *tcp)
812 for (p = 0; p < SUPPORTED_PERSONALITIES; ++p)
813 free(tcp->inject_vec[p]);
815 free_tcb_priv_data(tcp);
817 #ifdef ENABLE_STACKTRACE
818 if (stack_trace_enabled)
823 tcp->mmap_cache->free_fn(tcp, __func__);
826 debug_msg("dropped tcb for pid %d, %d remain", tcp->pid, nprocs);
829 if (followfork >= 2) {
830 if (tcp->curcol != 0)
831 fprintf(tcp->outf, " <detached ...>\n");
834 if (printing_tcp == tcp && tcp->curcol != 0)
835 fprintf(tcp->outf, " <detached ...>\n");
836 flush_tcp_output(tcp);
840 if (current_tcp == tcp)
841 set_current_tcp(NULL);
842 if (printing_tcp == tcp)
845 memset(tcp, 0, sizeof(*tcp));
848 /* Detach traced process.
849 * Never call DETACH twice on the same process as both unattached and
850 * attached-unstopped processes give the same ESRCH. For unattached process we
851 * would SIGSTOP it and wait for its SIGSTOP notification forever.
854 detach(struct tcb *tcp)
860 * Linux wrongly insists the child be stopped
861 * before detaching. Arghh. We go through hoops
862 * to make a clean break of things.
865 if (!(tcp->flags & TCB_ATTACHED))
868 /* We attached but possibly didn't see the expected SIGSTOP.
869 * We must catch exactly one as otherwise the detached process
870 * would be left stopped (process state T).
872 if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
875 error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
877 /* On a clear day, you can see forever. */
880 if (errno != ESRCH) {
881 /* Shouldn't happen. */
882 perror_func_msg("ptrace(PTRACE_DETACH,%u)", tcp->pid);
885 /* ESRCH: process is either not stopped or doesn't exist. */
886 if (my_tkill(tcp->pid, 0) < 0) {
888 /* Shouldn't happen. */
889 perror_func_msg("tkill(%u,0)", tcp->pid);
890 /* else: process doesn't exist. */
893 /* Process is not stopped, need to stop it. */
896 * With SEIZE, tracee can be in group-stop already.
897 * In this state sending it another SIGSTOP does nothing.
898 * Need to use INTERRUPT.
899 * Testcase: trying to ^C a "strace -p <stopped_process>".
901 error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
905 perror_func_msg("ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
907 error = my_tkill(tcp->pid, SIGSTOP);
911 perror_func_msg("tkill(%u,SIGSTOP)", tcp->pid);
913 /* Either process doesn't exist, or some weird error. */
917 /* We end up here in three cases:
918 * 1. We sent PTRACE_INTERRUPT (use_seize case)
919 * 2. We sent SIGSTOP (!use_seize)
920 * 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
924 if (waitpid(tcp->pid, &status, __WALL) < 0) {
928 * if (errno == ECHILD) break;
929 * ^^^ WRONG! We expect this PID to exist,
930 * and want to emit a message otherwise:
932 perror_func_msg("waitpid(%u)", tcp->pid);
935 if (!WIFSTOPPED(status)) {
937 * Tracee exited or was killed by signal.
938 * We shouldn't normally reach this place:
939 * we don't want to consume exit status.
940 * Consider "strace -p PID" being ^C-ed:
941 * we want merely to detach from PID.
943 * However, we _can_ end up here if tracee
948 sig = WSTOPSIG(status);
949 debug_msg("detach wait: event:%d sig:%d",
950 (unsigned) status >> 16, sig);
952 unsigned event = (unsigned)status >> 16;
953 if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
955 * sig == SIGTRAP: PTRACE_INTERRUPT stop.
956 * sig == other: process was already stopped
957 * with this stopping sig (see tests/detach-stopped).
958 * Looks like re-injecting this sig is not necessary
959 * in DETACH for the tracee to remain stopped.
964 * PTRACE_INTERRUPT is not guaranteed to produce
965 * the above event if other ptrace-stop is pending.
966 * See tests/detach-sleeping testcase:
967 * strace got SIGINT while tracee is sleeping.
968 * We sent PTRACE_INTERRUPT.
969 * We see syscall exit, not PTRACE_INTERRUPT stop.
970 * We won't get PTRACE_INTERRUPT stop
971 * if we would CONT now. Need to DETACH.
973 if (sig == syscall_trap_sig)
975 /* else: not sure in which case we can be here.
976 * Signal stop? Inject it while detaching.
978 ptrace_restart(PTRACE_DETACH, tcp, sig);
981 /* Note: this check has to be after use_seize check */
982 /* (else, in use_seize case SIGSTOP will be mistreated) */
983 if (sig == SIGSTOP) {
984 /* Detach, suppressing SIGSTOP */
985 ptrace_restart(PTRACE_DETACH, tcp, 0);
988 if (sig == syscall_trap_sig)
990 /* Can't detach just yet, may need to wait for SIGSTOP */
991 error = ptrace_restart(PTRACE_CONT, tcp, sig);
993 /* Should not happen.
994 * Note: ptrace_restart returns 0 on ESRCH, so it's not it.
995 * ptrace_restart already emitted error message.
1002 if (!qflag && (tcp->flags & TCB_ATTACHED))
1003 error_msg("Process %u detached", tcp->pid);
1009 process_opt_p_list(char *opt)
1013 * We accept -p PID,PID; -p "`pidof PROG`"; -p "`pgrep PROG`".
1014 * pidof uses space as delim, pgrep uses newline. :(
1017 char *delim = opt + strcspn(opt, "\n\t ,");
1021 pid = string_to_uint(opt);
1023 error_msg_and_die("Invalid process id: '%s'", opt);
1025 if (pid == strace_tracer_pid) {
1026 error_msg_and_die("I'm sorry, I can't let you do that, Dave.");
1037 attach_tcb(struct tcb *const tcp)
1039 if (ptrace_attach_or_seize(tcp->pid) < 0) {
1040 perror_msg("attach: ptrace(%s, %d)",
1041 ptrace_attach_cmd, tcp->pid);
1046 after_successful_attach(tcp, TCB_GRABBED | post_attach_sigstop);
1047 debug_msg("attach to pid %d (main) succeeded", tcp->pid);
1049 static const char task_path[] = "/proc/%d/task";
1050 char procdir[sizeof(task_path) + sizeof(int) * 3];
1052 unsigned int ntid = 0, nerr = 0;
1054 if (followfork && tcp->pid != strace_child &&
1055 xsprintf(procdir, task_path, tcp->pid) > 0 &&
1056 (dir = opendir(procdir)) != NULL) {
1059 while ((de = read_dir(dir)) != NULL) {
1060 if (de->d_fileno == 0)
1063 int tid = string_to_uint(de->d_name);
1064 if (tid <= 0 || tid == tcp->pid)
1068 if (ptrace_attach_or_seize(tid) < 0) {
1070 debug_perror_msg("attach: ptrace(%s, %d)",
1071 ptrace_attach_cmd, tid);
1075 after_successful_attach(alloctcb(tid),
1076 TCB_GRABBED | post_attach_sigstop);
1077 debug_msg("attach to pid %d succeeded", tid);
1085 error_msg("Process %u attached"
1087 tcp->pid, ntid - nerr + 1);
1089 error_msg("Process %u attached",
1095 startup_attach(void)
1097 pid_t parent_pid = strace_tracer_pid;
1101 if (daemonized_tracer) {
1104 perror_func_msg_and_die("fork");
1106 if (pid) { /* parent */
1108 * Wait for grandchild to attach to straced process
1109 * (grandparent). Grandchild SIGKILLs us after it attached.
1110 * Grandparent's wait() is unblocked by our death,
1111 * it proceeds to exec the straced program.
1114 _exit(0); /* paranoia */
1117 /* We will be the tracer process. Remember our new pid: */
1118 strace_tracer_pid = getpid();
1121 for (tcbi = 0; tcbi < tcbtabsize; tcbi++) {
1127 /* Is this a process we should attach to, but not yet attached? */
1128 if (tcp->flags & TCB_ATTACHED)
1129 continue; /* no, we already attached it */
1131 if (tcp->pid == parent_pid || tcp->pid == strace_tracer_pid) {
1133 perror_msg("attach: pid %d", tcp->pid);
1142 } /* for each tcbtab[] */
1144 if (daemonized_tracer) {
1146 * Make parent go away.
1147 * Also makes grandparent's wait() unblock.
1149 kill(parent_pid, SIGKILL);
1154 /* Stack-o-phobic exec helper, in the hope to work around
1155 * NOMMU + "daemonized tracer" difficulty.
1157 struct exec_params {
1163 struct sigaction child_sa;
1165 static struct exec_params params_for_tracee;
1167 static void ATTRIBUTE_NOINLINE ATTRIBUTE_NORETURN
1170 struct exec_params *params = ¶ms_for_tracee;
1172 if (params->fd_to_close >= 0)
1173 close(params->fd_to_close);
1174 if (!daemonized_tracer && !use_seize) {
1175 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0) {
1176 perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
1180 if (username != NULL) {
1182 * It is important to set groups before we
1183 * lose privileges on setuid.
1185 if (initgroups(username, run_gid) < 0) {
1186 perror_msg_and_die("initgroups");
1188 if (setregid(run_gid, params->run_egid) < 0) {
1189 perror_msg_and_die("setregid");
1191 if (setreuid(run_uid, params->run_euid) < 0) {
1192 perror_msg_and_die("setreuid");
1194 } else if (geteuid() != 0)
1195 if (setreuid(run_uid, run_uid) < 0) {
1196 perror_msg_and_die("setreuid");
1199 if (!daemonized_tracer) {
1201 * Induce a ptrace stop. Tracer (our parent)
1202 * will resume us with PTRACE_SYSCALL and display
1203 * the immediately following execve syscall.
1204 * Can't do this on NOMMU systems, we are after
1205 * vfork: parent is blocked, stopping would deadlock.
1208 kill(getpid(), SIGSTOP);
1211 /* we depend on SIGCHLD set to SIG_DFL by init code */
1212 /* if it happens to be SIG_IGN'ed, wait won't block */
1217 if (params_for_tracee.child_sa.sa_handler != SIG_DFL)
1218 sigaction(SIGCHLD, ¶ms_for_tracee.child_sa, NULL);
1220 execv(params->pathname, params->argv);
1221 perror_msg_and_die("exec");
1225 * Open a dummy descriptor for use as a placeholder.
1226 * The descriptor is O_RDONLY with FD_CLOEXEC flag set.
1227 * A read attempt from such descriptor ends with EOF,
1228 * a write attempt is rejected with EBADF.
1231 open_dummy_desc(void)
1236 perror_func_msg_and_die("pipe");
1238 set_cloexec_flag(fds[0]);
1242 /* placeholder fds status for stdin and stdout */
1243 static bool fd_is_placeholder[2];
1246 * Ensure that all standard file descriptors are open by opening placeholder
1247 * file descriptors for those standard file descriptors that are not open.
1249 * The information which descriptors have been made open is saved
1250 * in fd_is_placeholder for later use.
1253 ensure_standard_fds_opened(void)
1257 while ((fd = open_dummy_desc()) <= 2) {
1260 fd_is_placeholder[fd] = true;
1268 * Redirect stdin and stdout unless they have been opened earlier
1269 * by ensure_standard_fds_opened as placeholders.
1272 redirect_standard_fds(void)
1277 * It might be a good idea to redirect stderr as well,
1278 * but we sometimes need to print error messages.
1280 for (i = 0; i <= 1; ++i) {
1281 if (!fd_is_placeholder[i]) {
1289 startup_child(char **argv)
1291 struct_stat statbuf;
1292 const char *filename;
1293 size_t filename_len;
1294 char pathname[PATH_MAX];
1299 filename_len = strlen(filename);
1301 if (filename_len > sizeof(pathname) - 1) {
1302 errno = ENAMETOOLONG;
1303 perror_msg_and_die("exec");
1305 if (strchr(filename, '/')) {
1306 strcpy(pathname, filename);
1308 #ifdef USE_DEBUGGING_EXEC
1310 * Debuggers customarily check the current directory
1311 * first regardless of the path but doing that gives
1312 * security geeks a panic attack.
1314 else if (stat_file(filename, &statbuf) == 0)
1315 strcpy(pathname, filename);
1316 #endif /* USE_DEBUGGING_EXEC */
1321 for (path = getenv("PATH"); path && *path; path += m) {
1322 const char *colon = strchr(path, ':');
1327 m = n = strlen(path);
1329 if (!getcwd(pathname, PATH_MAX))
1331 len = strlen(pathname);
1332 } else if (n > sizeof(pathname) - 1)
1335 strncpy(pathname, path, n);
1338 if (len && pathname[len - 1] != '/')
1339 pathname[len++] = '/';
1340 if (filename_len + len > sizeof(pathname) - 1)
1342 strcpy(pathname + len, filename);
1343 if (stat_file(pathname, &statbuf) == 0 &&
1344 /* Accept only regular files
1345 with some execute bits set.
1346 XXX not perfect, might still fail */
1347 S_ISREG(statbuf.st_mode) &&
1348 (statbuf.st_mode & 0111))
1351 if (!path || !*path)
1354 if (stat_file(pathname, &statbuf) < 0) {
1355 perror_msg_and_die("Can't stat '%s'", filename);
1358 params_for_tracee.fd_to_close = (shared_log != stderr) ? fileno(shared_log) : -1;
1359 params_for_tracee.run_euid = (statbuf.st_mode & S_ISUID) ? statbuf.st_uid : run_uid;
1360 params_for_tracee.run_egid = (statbuf.st_mode & S_ISGID) ? statbuf.st_gid : run_gid;
1361 params_for_tracee.argv = argv;
1363 * On NOMMU, can be safely freed only after execve in tracee.
1364 * It's hard to know when that happens, so we just leak it.
1366 params_for_tracee.pathname = NOMMU_SYSTEM ? xstrdup(pathname) : pathname;
1368 #if defined HAVE_PRCTL && defined PR_SET_PTRACER && defined PR_SET_PTRACER_ANY
1369 if (daemonized_tracer)
1370 prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
1375 perror_func_msg_and_die("fork");
1377 if ((pid != 0 && daemonized_tracer)
1378 || (pid == 0 && !daemonized_tracer)
1380 /* We are to become the tracee. Two cases:
1382 * not -D: we are child
1387 /* We are the tracer */
1389 if (!daemonized_tracer) {
1392 /* child did PTRACE_TRACEME, nothing to do in parent */
1394 if (!NOMMU_SYSTEM) {
1395 /* Wait until child stopped itself */
1397 while (waitpid(pid, &status, WSTOPPED) < 0) {
1400 perror_msg_and_die("waitpid");
1402 if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGSTOP) {
1403 kill_save_errno(pid, SIGKILL);
1404 perror_msg_and_die("Unexpected wait status %#x",
1408 /* Else: NOMMU case, we have no way to sync.
1409 * Just attach to it as soon as possible.
1410 * This means that we may miss a few first syscalls...
1413 if (ptrace_attach_or_seize(pid)) {
1414 kill_save_errno(pid, SIGKILL);
1415 perror_msg_and_die("attach: ptrace(%s, %d)",
1416 ptrace_attach_cmd, pid);
1421 tcp = alloctcb(pid);
1422 after_successful_attach(tcp, TCB_SKIP_DETACH_ON_FIRST_EXEC
1425 | post_attach_sigstop)));
1427 /* With -D, we are *child* here, the tracee is our parent. */
1428 strace_child = strace_tracer_pid;
1429 strace_tracer_pid = getpid();
1430 tcp = alloctcb(strace_child);
1431 tcp->flags |= TCB_SKIP_DETACH_ON_FIRST_EXEC | TCB_HIDE_LOG;
1433 * Attaching will be done later, by startup_attach.
1434 * Note: we don't do after_successful_attach() here either!
1437 /* NOMMU BUG! -D mode is active, we (child) return,
1438 * and we will scribble over parent's stack!
1439 * When parent later unpauses, it segfaults.
1442 * (1) by declaring exec_or_die() NORETURN,
1443 * hopefully compiler will just jump to it
1444 * instead of call (won't push anything to stack),
1445 * (2) by trying very hard in exec_or_die()
1446 * to not use any stack,
1447 * (3) having a really big (PATH_MAX) stack object
1448 * in this function, which creates a "buffer" between
1449 * child's and parent's stack pointers.
1450 * This may save us if (1) and (2) failed
1451 * and compiler decided to use stack in exec_or_die() anyway
1452 * (happens on i386 because of stack parameter passing).
1454 * A cleaner solution is to use makecontext + setcontext
1455 * to create a genuine separate stack and execute on it.
1459 * A case where straced process is part of a pipe:
1460 * { sleep 1; yes | head -n99999; } | strace -o/dev/null sh -c 'exec <&-; sleep 9'
1461 * If strace won't close its fd#0, closing it in tracee is not enough:
1462 * the pipe is still open, it has a reader. Thus, "head" will not get its
1463 * SIGPIPE at once, on the first write.
1465 * Preventing it by redirecting strace's stdin/out.
1466 * (Don't leave fds 0 and 1 closed, this is bad practice: future opens
1467 * will reuse them, unexpectedly making a newly opened object "stdin").
1469 redirect_standard_fds();
1473 test_ptrace_seize(void)
1477 /* Need fork for test. NOMMU has no forks */
1479 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1485 perror_func_msg_and_die("fork");
1492 /* PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After
1493 * attaching tracee continues to run unless a trap condition occurs.
1494 * PTRACE_SEIZE doesn't affect signal or group stop state.
1496 if (ptrace(PTRACE_SEIZE, pid, 0, 0) == 0) {
1497 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1499 debug_msg("PTRACE_SEIZE doesn't work");
1505 int status, tracee_pid;
1508 tracee_pid = waitpid(pid, &status, 0);
1509 if (tracee_pid <= 0) {
1512 perror_func_msg_and_die("unexpected wait result %d",
1515 if (WIFSIGNALED(status))
1518 error_func_msg_and_die("unexpected wait status %#x", status);
1523 get_os_release(void)
1529 perror_msg_and_die("uname");
1530 /* u.release has this form: "3.2.9[-some-garbage]" */
1534 if (!(*p >= '0' && *p <= '9'))
1535 error_msg_and_die("Bad OS release string: '%s'", u.release);
1536 /* Note: this open-codes KERNEL_VERSION(): */
1537 rel = (rel << 8) | atoi(p);
1538 if (rel >= KERNEL_VERSION(1, 0, 0))
1540 while (*p >= '0' && *p <= '9')
1543 if (rel >= KERNEL_VERSION(0, 1, 0)) {
1544 /* "X.Y-something" means "X.Y.0" */
1548 error_msg_and_die("Bad OS release string: '%s'", u.release);
1556 set_sighandler(int signo, void (*sighandler)(int), struct sigaction *oldact)
1558 const struct sigaction sa = { .sa_handler = sighandler };
1559 sigaction(signo, &sa, oldact);
1563 * Initialization part of main() was eating much stack (~0.5k),
1564 * which was unused after init.
1565 * We can reuse it if we move init code into a separate function.
1567 * Don't want main() to inline us and defeat the reason
1568 * we have a separate function.
1570 static void ATTRIBUTE_NOINLINE
1571 init(int argc, char *argv[])
1576 if (!program_invocation_name || !*program_invocation_name) {
1577 static char name[] = "strace";
1578 program_invocation_name =
1579 (argc > 0 && argv[0] && *argv[0]) ? argv[0] : name;
1582 strace_tracer_pid = getpid();
1584 os_release = get_os_release();
1586 shared_log = stderr;
1587 set_sortby(DEFAULT_SORTBY);
1588 set_personality(DEFAULT_PERSONALITY);
1589 qualify("trace=all");
1590 qualify("abbrev=all");
1591 qualify("verbose=all");
1592 #if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
1593 # error Bug in DEFAULT_QUAL_FLAGS
1595 qualify("signal=all");
1596 while ((c = getopt(argc, argv, "+"
1597 #ifdef ENABLE_STACKTRACE
1600 "a:Ab:cCdDe:E:fFhiI:o:O:p:P:qrs:S:tTu:vVwxX:yz")) != EOF) {
1603 acolumn = string_to_uint(optarg);
1605 error_opt_arg(c, optarg);
1611 if (strcmp(optarg, "execve") != 0)
1612 error_msg_and_die("Syscall '%s' for -b isn't supported",
1614 detach_on_execve = 1;
1617 if (cflag == CFLAG_BOTH) {
1618 error_msg_and_help("-c and -C are mutually exclusive");
1620 cflag = CFLAG_ONLY_STATS;
1623 if (cflag == CFLAG_ONLY_STATS) {
1624 error_msg_and_help("-c and -C are mutually exclusive");
1632 daemonized_tracer = 1;
1638 if (putenv(optarg) < 0)
1639 perror_msg_and_die("putenv");
1654 opt_intr = string_to_uint_upto(optarg, NUM_INTR_OPTS - 1);
1656 error_opt_arg(c, optarg);
1658 #ifdef ENABLE_STACKTRACE
1660 stack_trace_enabled = true;
1667 i = string_to_uint(optarg);
1669 error_opt_arg(c, optarg);
1673 process_opt_p_list(optarg);
1676 pathtrace_select(optarg);
1685 i = string_to_uint(optarg);
1686 if (i < 0 || (unsigned int) i > -1U / 4)
1687 error_opt_arg(c, optarg);
1703 qualify("abbrev=none");
1710 count_wallclock = 1;
1716 if (!strcmp(optarg, "raw"))
1717 xlat_verbosity = XLAT_STYLE_RAW;
1718 else if (!strcmp(optarg, "abbrev"))
1719 xlat_verbosity = XLAT_STYLE_ABBREV;
1720 else if (!strcmp(optarg, "verbose"))
1721 xlat_verbosity = XLAT_STYLE_VERBOSE;
1723 error_opt_arg(c, optarg);
1729 not_failing_only = 1;
1732 error_msg_and_help(NULL);
1740 if (argc < 0 || (!nprocs && !argc)) {
1741 error_msg_and_help("must have PROG [ARGS] or -p PID");
1744 if (!argc && daemonized_tracer) {
1745 error_msg_and_help("PROG [ARGS] must be specified with -D");
1750 error_msg("deprecated option -F ignored");
1752 error_msg("option -F is deprecated, "
1753 "please use -f instead");
1758 if (followfork >= 2 && cflag) {
1759 error_msg_and_help("(-c or -C) and -ff are mutually exclusive");
1762 if (count_wallclock && !cflag) {
1763 error_msg_and_help("-w must be given with (-c or -C)");
1766 if (cflag == CFLAG_ONLY_STATS) {
1768 error_msg("-%c has no effect with -c", 'i');
1769 #ifdef ENABLE_STACKTRACE
1770 if (stack_trace_enabled)
1771 error_msg("-%c has no effect with -c", 'k');
1774 error_msg("-%c has no effect with -c", 'r');
1776 error_msg("-%c has no effect with -c", 't');
1778 error_msg("-%c has no effect with -c", 'T');
1780 error_msg("-%c has no effect with -c", 'y');
1783 acolumn_spaces = xmalloc(acolumn + 1);
1784 memset(acolumn_spaces, ' ', acolumn);
1785 acolumn_spaces[acolumn] = '\0';
1787 set_sighandler(SIGCHLD, SIG_DFL, ¶ms_for_tracee.child_sa);
1789 #ifdef ENABLE_STACKTRACE
1790 if (stack_trace_enabled)
1794 /* See if they want to run as another user. */
1795 if (username != NULL) {
1796 struct passwd *pent;
1798 if (getuid() != 0 || geteuid() != 0) {
1799 error_msg_and_die("You must be root to use the -u option");
1801 pent = getpwnam(username);
1803 error_msg_and_die("Cannot find user '%s'", username);
1805 run_uid = pent->pw_uid;
1806 run_gid = pent->pw_gid;
1813 ptrace_setoptions |= PTRACE_O_TRACECLONE |
1814 PTRACE_O_TRACEFORK |
1815 PTRACE_O_TRACEVFORK;
1816 debug_msg("ptrace_setoptions = %#x", ptrace_setoptions);
1817 test_ptrace_seize();
1820 * Is something weird with our stdin and/or stdout -
1821 * for example, may they be not open? In this case,
1822 * ensure that none of the future opens uses them.
1824 * This was seen in the wild when /proc/sys/kernel/core_pattern
1825 * was set to "|/bin/strace -o/tmp/LOG PROG":
1826 * kernel runs coredump helper with fd#0 open but fd#1 closed (!),
1827 * therefore LOG gets opened to fd#1, and fd#1 is closed by
1828 * "don't hold up stdin/out open" code soon after.
1830 ensure_standard_fds_opened();
1832 /* Check if they want to redirect the output. */
1834 /* See if they want to pipe the output. */
1835 if (outfname[0] == '|' || outfname[0] == '!') {
1837 * We can't do the <outfname>.PID funny business
1838 * when using popen, so prohibit it.
1840 if (followfork >= 2)
1841 error_msg_and_help("piping the output and -ff "
1842 "are mutually exclusive");
1843 shared_log = strace_popen(outfname + 1);
1844 } else if (followfork < 2) {
1845 shared_log = strace_fopen(outfname);
1846 } else if (strlen(outfname) >= PATH_MAX - sizeof(int) * 3) {
1847 errno = ENAMETOOLONG;
1848 perror_msg_and_die("%s", outfname);
1851 /* -ff without -o FILE is the same as single -f */
1852 if (followfork >= 2)
1856 if (!outfname || outfname[0] == '|' || outfname[0] == '!') {
1857 setvbuf(shared_log, NULL, _IOLBF, 0);
1861 * argv[0] -pPID -oFILE Default interactive setting
1862 * yes * 0 INTR_WHILE_WAIT
1863 * no 1 0 INTR_WHILE_WAIT
1864 * yes * 1 INTR_NEVER
1865 * no 1 1 INTR_WHILE_WAIT
1868 if (outfname && argc) {
1870 opt_intr = INTR_NEVER;
1875 opt_intr = INTR_WHILE_WAIT;
1878 * startup_child() must be called before the signal handlers get
1879 * installed below as they are inherited into the spawned process.
1880 * Also we do not need to be protected by them as during interruption
1881 * in the startup_child() mode we kill the spawned process anyway.
1884 startup_child(argv);
1887 set_sighandler(SIGTTOU, SIG_IGN, NULL);
1888 set_sighandler(SIGTTIN, SIG_IGN, NULL);
1889 if (opt_intr != INTR_ANYWHERE) {
1890 if (opt_intr == INTR_BLOCK_TSTP_TOO)
1891 set_sighandler(SIGTSTP, SIG_IGN, NULL);
1893 * In interactive mode (if no -o OUTFILE, or -p PID is used),
1894 * fatal signals are handled asynchronously and acted
1895 * when waiting for process state changes.
1896 * In non-interactive mode these signals are ignored.
1898 set_sighandler(SIGHUP, interactive ? interrupt : SIG_IGN, NULL);
1899 set_sighandler(SIGINT, interactive ? interrupt : SIG_IGN, NULL);
1900 set_sighandler(SIGQUIT, interactive ? interrupt : SIG_IGN, NULL);
1901 set_sighandler(SIGPIPE, interactive ? interrupt : SIG_IGN, NULL);
1902 set_sighandler(SIGTERM, interactive ? interrupt : SIG_IGN, NULL);
1905 sigemptyset(&timer_set);
1906 sigaddset(&timer_set, SIGALRM);
1907 sigprocmask(SIG_BLOCK, &timer_set, NULL);
1908 set_sighandler(SIGALRM, timer_sighandler, NULL);
1910 if (nprocs != 0 || daemonized_tracer)
1913 /* Do we want pids printed in our -o OUTFILE?
1914 * -ff: no (every pid has its own file); or
1915 * -f: yes (there can be more pids in the future); or
1916 * -p PID1,PID2: yes (there are already more than one pid)
1918 print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
1922 pid2tcb(const int pid)
1927 #define PID2TCB_CACHE_SIZE 1024U
1928 #define PID2TCB_CACHE_MASK (PID2TCB_CACHE_SIZE - 1)
1930 static struct tcb *pid2tcb_cache[PID2TCB_CACHE_SIZE];
1931 struct tcb **const ptcp = &pid2tcb_cache[pid & PID2TCB_CACHE_MASK];
1932 struct tcb *tcp = *ptcp;
1934 if (tcp && tcp->pid == pid)
1937 for (unsigned int i = 0; i < tcbtabsize; ++i) {
1939 if (tcp->pid == pid)
1953 /* 'interrupted' is a volatile object, fetch it only once */
1954 fatal_sig = interrupted;
1956 fatal_sig = SIGTERM;
1958 for (i = 0; i < tcbtabsize; i++) {
1962 debug_func_msg("looking at pid %u", tcp->pid);
1963 if (tcp->pid == strace_child) {
1964 kill(tcp->pid, SIGCONT);
1965 kill(tcp->pid, fatal_sig);
1970 call_summary(shared_log);
1980 print_debug_info(const int pid, int status)
1982 const unsigned int event = (unsigned int) status >> 16;
1983 char buf[sizeof("WIFEXITED,exitcode=%u") + sizeof(int)*3 /*paranoia:*/ + 16];
1984 char evbuf[sizeof(",EVENT_VFORK_DONE (%u)") + sizeof(int)*3 /*paranoia:*/ + 16];
1987 if (WIFSIGNALED(status))
1989 xsprintf(buf, "WIFSIGNALED,%ssig=%s",
1990 WCOREDUMP(status) ? "core," : "",
1991 signame(WTERMSIG(status)));
1993 xsprintf(buf, "WIFSIGNALED,sig=%s",
1994 signame(WTERMSIG(status)));
1996 if (WIFEXITED(status))
1997 xsprintf(buf, "WIFEXITED,exitcode=%u", WEXITSTATUS(status));
1998 if (WIFSTOPPED(status))
1999 xsprintf(buf, "WIFSTOPPED,sig=%s", signame(WSTOPSIG(status)));
2002 static const char *const event_names[] = {
2003 [PTRACE_EVENT_CLONE] = "CLONE",
2004 [PTRACE_EVENT_FORK] = "FORK",
2005 [PTRACE_EVENT_VFORK] = "VFORK",
2006 [PTRACE_EVENT_VFORK_DONE] = "VFORK_DONE",
2007 [PTRACE_EVENT_EXEC] = "EXEC",
2008 [PTRACE_EVENT_EXIT] = "EXIT",
2009 /* [PTRACE_EVENT_STOP (=128)] would make biggish array */
2011 const char *e = "??";
2012 if (event < ARRAY_SIZE(event_names))
2013 e = event_names[event];
2014 else if (event == PTRACE_EVENT_STOP)
2016 xsprintf(evbuf, ",EVENT_%s (%u)", e, event);
2018 error_msg("[wait(0x%06x) = %u] %s%s", status, pid, buf, evbuf);
2022 maybe_allocate_tcb(const int pid, int status)
2024 if (!WIFSTOPPED(status)) {
2025 if (detach_on_execve && pid == strace_child) {
2026 /* example: strace -bexecve sh -c 'exec true' */
2031 * This can happen if we inherited an unknown child.
2032 * Example: (sleep 1 & exec strace true)
2034 error_msg("Exit of unknown pid %u ignored", pid);
2038 /* We assume it's a fork/vfork/clone child */
2039 struct tcb *tcp = alloctcb(pid);
2040 after_successful_attach(tcp, post_attach_sigstop);
2042 error_msg("Process %d attached", pid);
2046 * This can happen if a clone call misused CLONE_PTRACE itself.
2048 * There used to be a dance around possible re-injection of
2049 * WSTOPSIG(status), but it was later removed as the only
2050 * observable stop here is the initial ptrace-stop.
2052 ptrace(PTRACE_DETACH, pid, NULL, 0L);
2053 error_msg("Detached unknown pid %d", pid);
2059 maybe_switch_tcbs(struct tcb *tcp, const int pid)
2062 struct tcb *execve_thread;
2065 if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, &old_pid) < 0)
2067 /* Avoid truncation in pid2tcb() param passing */
2068 if (old_pid <= 0 || old_pid == pid)
2070 if ((unsigned long) old_pid > UINT_MAX)
2072 execve_thread = pid2tcb(old_pid);
2073 /* It should be !NULL, but I feel paranoid */
2077 if (execve_thread->curcol != 0) {
2079 * One case we are here is -ff:
2080 * try "strace -oLOG -ff test/threaded_execve"
2082 fprintf(execve_thread->outf, " <pid changed to %d ...>\n", pid);
2083 /*execve_thread->curcol = 0; - no need, see code below */
2085 /* Swap output FILEs (needed for -ff) */
2086 fp = execve_thread->outf;
2087 execve_thread->outf = tcp->outf;
2089 /* And their column positions */
2090 execve_thread->curcol = tcp->curcol;
2092 /* Drop leader, but close execve'd thread outfile (if -ff) */
2094 /* Switch to the thread, reusing leader's outfile and pid */
2095 tcp = execve_thread;
2097 if (cflag != CFLAG_ONLY_STATS) {
2099 tprintf("+++ superseded by execve in pid %lu +++\n", old_pid);
2101 tcp->flags |= TCB_REPRINT;
2108 print_signalled(struct tcb *tcp, const int pid, int status)
2110 if (pid == strace_child) {
2111 exit_code = 0x100 | WTERMSIG(status);
2115 if (cflag != CFLAG_ONLY_STATS
2116 && is_number_in_set(WTERMSIG(status), signal_set)) {
2119 tprintf("+++ killed by %s %s+++\n",
2120 signame(WTERMSIG(status)),
2121 WCOREDUMP(status) ? "(core dumped) " : "");
2123 tprintf("+++ killed by %s +++\n",
2124 signame(WTERMSIG(status)));
2131 print_exited(struct tcb *tcp, const int pid, int status)
2133 if (pid == strace_child) {
2134 exit_code = WEXITSTATUS(status);
2138 if (cflag != CFLAG_ONLY_STATS &&
2141 tprintf("+++ exited with %d +++\n", WEXITSTATUS(status));
2147 print_stopped(struct tcb *tcp, const siginfo_t *si, const unsigned int sig)
2149 if (cflag != CFLAG_ONLY_STATS
2151 && is_number_in_set(sig, signal_set)) {
2154 tprintf("--- %s ", signame(sig));
2158 tprintf("--- stopped by %s ---\n", signame(sig));
2164 startup_tcb(struct tcb *tcp)
2166 debug_msg("pid %d has TCB_STARTUP, initializing it", tcp->pid);
2168 tcp->flags &= ~TCB_STARTUP;
2171 debug_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");
2181 if ((tcp->flags & TCB_GRABBED) && (get_scno(tcp) == 1))
2182 tcp->s_prev_ent = tcp->s_ent;
2186 print_event_exit(struct tcb *tcp)
2188 if (entering(tcp) || filtered(tcp) || hide_log(tcp)
2189 || cflag == CFLAG_ONLY_STATS) {
2193 if (followfork < 2 && printing_tcp && printing_tcp != tcp
2194 && printing_tcp->curcol != 0) {
2195 set_current_tcp(printing_tcp);
2196 tprints(" <unfinished ...>\n");
2197 flush_tcp_output(printing_tcp);
2198 printing_tcp->curcol = 0;
2199 set_current_tcp(tcp);
2202 if ((followfork < 2 && printing_tcp != tcp)
2203 || (tcp->flags & TCB_REPRINT)) {
2204 tcp->flags &= ~TCB_REPRINT;
2206 tprintf("<... %s resumed>", tcp->s_ent->sys_name);
2209 if (!(tcp->sys_func_rval & RVAL_DECODED)) {
2211 * The decoder has probably decided to print something
2212 * on exiting syscall which is not going to happen.
2214 tprints(" <unfinished ...>");
2224 static enum trace_event
2225 next_event(int *pstatus, siginfo_t *si)
2236 * Used to exit simply when nprocs hits zero, but in this testcase:
2237 * int main(void) { _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...
2256 const bool unblock_delay_timer = is_delay_timer_armed();
2259 * The window of opportunity to handle expirations
2260 * of the delay timer opens here.
2262 * Unblock the signal handler for the delay timer
2263 * iff the delay timer is already created.
2265 if (unblock_delay_timer)
2266 sigprocmask(SIG_UNBLOCK, &timer_set, NULL);
2269 * If the delay timer has expired, then its expiration
2270 * has been handled already by the signal handler.
2272 * If the delay timer expires during wait4(),
2273 * then the system call will be interrupted and
2274 * the expiration will be handled by the signal handler.
2276 pid = wait4(-1, pstatus, __WALL, (cflag ? &ru : NULL));
2277 const int wait_errno = errno;
2280 * The window of opportunity to handle expirations
2281 * of the delay timer closes here.
2283 * Block the signal handler for the delay timer
2284 * iff it was unblocked earlier.
2286 if (unblock_delay_timer) {
2287 sigprocmask(SIG_BLOCK, &timer_set, NULL);
2294 if (wait_errno == EINTR)
2296 if (nprocs == 0 && wait_errno == ECHILD)
2299 * If nprocs > 0, ECHILD is not expected,
2300 * treat it as any other error here:
2303 perror_msg_and_die("wait4(__WALL)");
2308 if (pid == popen_pid) {
2309 if (!WIFSTOPPED(status))
2315 print_debug_info(pid, status);
2317 /* Look up 'pid' in our table. */
2321 tcp = maybe_allocate_tcb(pid, status);
2328 /* Set current output file */
2329 set_current_tcp(tcp);
2332 struct timespec stime = {
2333 .tv_sec = ru.ru_stime.tv_sec,
2334 .tv_nsec = ru.ru_stime.tv_usec * 1000
2336 ts_sub(&tcp->dtime, &stime, &tcp->stime);
2340 if (WIFSIGNALED(status))
2341 return TE_SIGNALLED;
2343 if (WIFEXITED(status))
2347 * As WCONTINUED flag has not been specified to wait4,
2348 * it cannot be WIFCONTINUED(status), so the only case
2349 * that remains is WIFSTOPPED(status).
2352 /* Is this the very first time we see this tracee stopped? */
2353 if (tcp->flags & TCB_STARTUP)
2356 const unsigned int sig = WSTOPSIG(status);
2357 const unsigned int event = (unsigned int) status >> 16;
2362 * Is this post-attach SIGSTOP?
2363 * Interestingly, the process may stop
2364 * with STOPSIG equal to some other signal
2365 * than SIGSTOP if we happened to attach
2366 * just before the process takes a signal.
2368 if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
2369 debug_func_msg("ignored SIGSTOP on pid %d", tcp->pid);
2370 tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
2372 } else if (sig == syscall_trap_sig) {
2373 return TE_SYSCALL_STOP;
2375 *si = (siginfo_t) {};
2377 * True if tracee is stopped by signal
2378 * (as opposed to "tracee received signal").
2379 * TODO: shouldn't we check for errno == EINVAL too?
2380 * We can get ESRCH instead, you know...
2382 bool stopped = ptrace(PTRACE_GETSIGINFO, pid, 0, si) < 0;
2383 return stopped ? TE_GROUP_STOP : TE_SIGNAL_DELIVERY_STOP;
2386 case PTRACE_EVENT_STOP:
2388 * PTRACE_INTERRUPT-stop or group-stop.
2389 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
2396 return TE_GROUP_STOP;
2399 case PTRACE_EVENT_EXEC:
2400 return TE_STOP_BEFORE_EXECVE;
2401 case PTRACE_EVENT_EXIT:
2402 return TE_STOP_BEFORE_EXIT;
2409 trace_syscall(struct tcb *tcp, unsigned int *sig)
2411 if (entering(tcp)) {
2412 int res = syscall_entering_decode(tcp);
2417 res = syscall_entering_trace(tcp, sig);
2419 syscall_entering_finish(tcp, res);
2422 struct timespec ts = {};
2423 int res = syscall_exiting_decode(tcp, &ts);
2425 res = syscall_exiting_trace(tcp, &ts, res);
2427 syscall_exiting_finish(tcp);
2432 /* Returns true iff the main trace loop has to continue. */
2434 dispatch_event(enum trace_event ret, int *pstatus, siginfo_t *si)
2436 unsigned int restart_op = PTRACE_SYSCALL;
2437 unsigned int restart_sig = 0;
2449 case TE_SYSCALL_STOP:
2450 if (trace_syscall(current_tcp, &restart_sig) < 0) {
2452 * ptrace() failed in trace_syscall().
2453 * Likely a result of process disappearing mid-flight.
2454 * Observed case: exit_group() or SIGKILL terminating
2455 * all processes in thread group.
2456 * We assume that ptrace error was caused by process death.
2457 * We used to detach(current_tcp) here, but since we no
2458 * longer implement "detach before death" policy/hack,
2459 * we can let this process to report its death to us
2460 * normally, via WIFEXITED or WIFSIGNALED wait status.
2466 case TE_SIGNAL_DELIVERY_STOP:
2467 restart_sig = WSTOPSIG(*pstatus);
2468 print_stopped(current_tcp, si, restart_sig);
2472 print_signalled(current_tcp, current_tcp->pid, *pstatus);
2473 droptcb(current_tcp);
2477 restart_sig = WSTOPSIG(*pstatus);
2478 print_stopped(current_tcp, NULL, restart_sig);
2481 * This ends ptrace-stop, but does *not* end group-stop.
2482 * This makes stopping signals work properly on straced
2483 * process (that is, process really stops. It used to
2486 restart_op = PTRACE_LISTEN;
2492 print_exited(current_tcp, current_tcp->pid, *pstatus);
2493 droptcb(current_tcp);
2496 case TE_STOP_BEFORE_EXECVE:
2498 * Check that we are inside syscall now (next event after
2499 * PTRACE_EVENT_EXEC should be for syscall exiting). If it is
2500 * not the case, we might have a situation when we attach to a
2501 * process and the first thing we see is a PTRACE_EVENT_EXEC
2502 * and all the following syscall state tracking is screwed up
2505 if (entering(current_tcp)) {
2508 error_msg("Stray PTRACE_EVENT_EXEC from pid %d"
2509 ", trying to recover...",
2512 current_tcp->flags |= TCB_RECOVERING;
2513 ret = trace_syscall(current_tcp, &restart_sig);
2514 current_tcp->flags &= ~TCB_RECOVERING;
2517 /* The reason is described in TE_SYSCALL_STOP */
2523 * Under Linux, execve changes pid to thread leader's pid,
2524 * and we see this changed pid on EVENT_EXEC and later,
2525 * execve sysexit. Leader "disappears" without exit
2526 * notification. Let user know that, drop leader's tcb,
2527 * and fix up pid in execve thread's tcb.
2528 * Effectively, execve thread's tcb replaces leader's tcb.
2530 * BTW, leader is 'stuck undead' (doesn't report WIFEXITED
2531 * on exit syscall) in multithreaded programs exactly
2532 * in order to handle this case.
2534 * PTRACE_GETEVENTMSG returns old pid starting from Linux 3.0.
2535 * On 2.6 and earlier, it can return garbage.
2537 if (os_release >= KERNEL_VERSION(3, 0, 0))
2538 set_current_tcp(maybe_switch_tcbs(current_tcp,
2541 if (detach_on_execve) {
2542 if (current_tcp->flags & TCB_SKIP_DETACH_ON_FIRST_EXEC) {
2543 current_tcp->flags &= ~TCB_SKIP_DETACH_ON_FIRST_EXEC;
2545 detach(current_tcp); /* do "-b execve" thingy */
2551 case TE_STOP_BEFORE_EXIT:
2552 print_event_exit(current_tcp);
2556 /* We handled quick cases, we are permitted to interrupt now. */
2560 /* If the process is being delayed, do not ptrace_restart just yet */
2561 if (syscall_delayed(current_tcp))
2564 if (ptrace_restart(restart_op, current_tcp, restart_sig) < 0) {
2565 /* Note: ptrace_restart emitted error message */
2573 restart_delayed_tcb(struct tcb *const tcp)
2575 debug_func_msg("pid %d", tcp->pid);
2577 tcp->flags &= ~TCB_DELAYED;
2579 struct tcb *const prev_tcp = current_tcp;
2581 bool ret = dispatch_event(TE_RESTART, NULL, NULL);
2582 current_tcp = prev_tcp;
2588 restart_delayed_tcbs(void)
2590 struct tcb *tcp_next = NULL;
2591 struct timespec ts_now;
2593 clock_gettime(CLOCK_MONOTONIC, &ts_now);
2595 for (size_t i = 0; i < tcbtabsize; i++) {
2596 struct tcb *tcp = tcbtab[i];
2598 if (tcp->pid && syscall_delayed(tcp)) {
2599 if (ts_cmp(&ts_now, &tcp->delay_expiration_time) > 0) {
2600 if (!restart_delayed_tcb(tcp))
2603 /* Check whether this tcb is the next. */
2605 ts_cmp(&tcp_next->delay_expiration_time,
2606 &tcp->delay_expiration_time) > 0) {
2614 arm_delay_timer(tcp_next);
2620 * As this signal handler does a lot of work that is not suitable
2621 * for signal handlers, extra care must be taken to ensure that
2622 * it is enabled only in those places where it's safe.
2625 timer_sighandler(int sig)
2627 delay_timer_expired();
2632 int saved_errno = errno;
2634 if (!restart_delayed_tcbs())
2637 errno = saved_errno;
2640 #ifdef ENABLE_COVERAGE_GCOV
2641 extern void __gcov_flush(void);
2644 static void ATTRIBUTE_NORETURN
2649 if (shared_log != stderr)
2652 while (waitpid(popen_pid, NULL, 0) < 0 && errno == EINTR)
2655 if (exit_code > 0xff) {
2656 /* Avoid potential core file clobbering. */
2657 struct_rlimit rlim = {0, 0};
2658 set_rlimit(RLIMIT_CORE, &rlim);
2660 /* Child was killed by a signal, mimic that. */
2662 signal(exit_code, SIG_DFL);
2663 #ifdef ENABLE_COVERAGE_GCOV
2668 /* Unblock the signal. */
2671 sigaddset(&mask, exit_code);
2672 #ifdef ENABLE_COVERAGE_GCOV
2675 sigprocmask(SIG_UNBLOCK, &mask, NULL);
2677 /* Paranoia - what if this signal is not fatal?
2678 Exit with 128 + signo then. */
2685 main(int argc, char *argv[])
2687 setlocale(LC_ALL, "");
2690 exit_code = !nprocs;
2694 while (dispatch_event(next_event(&status, &si), &status, &si))