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 * SPDX-License-Identifier: LGPL-2.1-or-later
18 #include <sys/resource.h>
27 #include <sys/utsname.h>
29 # include <sys/prctl.h>
31 #include <asm/unistd.h>
33 #include "kill_save_errno.h"
34 #include "largefile_wrappers.h"
35 #include "mmap_cache.h"
36 #include "number_set.h"
37 #include "ptrace_syscall_info.h"
39 #include "printsiginfo.h"
40 #include "trace_event.h"
45 /* In some libc, these aren't declared. Do it ourself: */
46 extern char **environ;
50 #ifdef ENABLE_STACKTRACE
51 /* if this is true do the stack trace for every system call */
52 bool stack_trace_enabled;
55 #define my_tkill(tid, sig) syscall(__NR_tkill, (tid), (sig))
57 /* Glue for systems without a MMU that cannot provide fork() */
58 #if !defined(HAVE_FORK)
60 # define NOMMU_SYSTEM 1
63 # define fork() vfork()
66 const unsigned int syscall_trap_sig = SIGTRAP | 0x80;
68 cflag_t cflag = CFLAG_NONE;
69 unsigned int followfork;
70 unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC
78 static unsigned int tflag;
80 static bool print_pid_pfx;
85 INTR_ANYWHERE = 1, /* don't block/ignore any signals */
86 INTR_WHILE_WAIT = 2, /* block fatal signals while decoding syscall. default */
87 INTR_NEVER = 3, /* block fatal signals. default if '-o FILE PROG' */
88 INTR_BLOCK_TSTP_TOO = 4, /* block fatal signals and SIGTSTP (^Z) */
92 /* We play with signal mask only if this mode is active: */
93 #define interactive (opt_intr == INTR_WHILE_WAIT)
96 * daemonized_tracer supports -D option.
97 * With this option, strace forks twice.
98 * Unlike normal case, with -D *grandparent* process exec's,
99 * becoming a traced process. Child exits (this prevents traced process
100 * from having children it doesn't expect to have), and grandchild
101 * attaches to grandparent similarly to strace -p PID.
102 * This allows for more transparent interaction in cases
103 * when process and its parent are communicating via signals,
104 * wait() etc. Without -D, strace process gets lodged in between,
105 * disrupting parent<->child link.
107 static bool daemonized_tracer;
109 static int post_attach_sigstop = TCB_IGNORE_ONE_SIGSTOP;
110 #define use_seize (post_attach_sigstop == 0)
112 /* Sometimes we want to print only succeeding syscalls. */
113 bool not_failing_only;
115 /* Show path associated with fd arguments */
116 unsigned int show_fd_path;
118 static bool detach_on_execve;
120 static int exit_code;
121 static int strace_child;
122 static int strace_tracer_pid;
124 static const char *username;
125 static uid_t run_uid;
126 static gid_t run_gid;
128 unsigned int max_strlen = DEFAULT_STRLEN;
129 static int acolumn = DEFAULT_ACOLUMN;
130 static char *acolumn_spaces;
132 /* Default output style for xlat entities */
133 enum xlat_style xlat_verbosity = XLAT_STYLE_ABBREV;
135 static const char *outfname;
136 /* If -ff, points to stderr. Else, it's our common output log */
137 static FILE *shared_log;
138 static bool open_append;
140 struct tcb *printing_tcp;
141 static struct tcb *current_tcp;
143 struct tcb_wait_data {
144 enum trace_event te; /**< Event passed to dispatch_event() */
145 int status; /**< status, returned by wait4() */
146 siginfo_t si; /**< siginfo, returned by PTRACE_GETSIGINFO */
149 static struct tcb **tcbtab;
150 static unsigned int nprocs;
151 static size_t tcbtabsize;
153 #ifndef HAVE_PROGRAM_INVOCATION_NAME
154 char *program_invocation_name;
157 unsigned os_release; /* generated from uname()'s u.release */
159 static void detach(struct tcb *tcp);
160 static void cleanup(void);
161 static void interrupt(int sig);
163 #ifdef HAVE_SIG_ATOMIC_T
164 static volatile sig_atomic_t interrupted, restart_failed;
166 static volatile int interrupted, restart_failed;
169 static sigset_t timer_set;
170 static void timer_sighandler(int);
172 #ifndef HAVE_STRERROR
174 # if !HAVE_DECL_SYS_ERRLIST
176 extern char *sys_errlist[];
182 static char buf[sizeof("Unknown error %d") + sizeof(int)*3];
184 if (err_no < 1 || err_no >= sys_nerr) {
185 xsprintf(buf, "Unknown error %d", err_no);
188 return sys_errlist[err_no];
191 #endif /* HAVE_STERRROR */
196 static const char features[] =
197 #ifdef ENABLE_STACKTRACE
198 " stack-trace=" USE_UNWINDER
203 #if SUPPORTED_PERSONALITIES > 1
204 # if defined HAVE_M32_MPERS
209 #endif /* SUPPORTED_PERSONALITIES > 1 */
210 #if SUPPORTED_PERSONALITIES > 2
211 # if defined HAVE_MX32_MPERS
216 #endif /* SUPPORTED_PERSONALITIES > 2 */
219 printf("%s -- version %s\n"
220 "Copyright (c) 1991-%s The strace developers <%s>.\n"
221 "This is free software; see the source for copying conditions. There is NO\n"
222 "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n",
223 PACKAGE_NAME, PACKAGE_VERSION, COPYRIGHT_YEAR, PACKAGE_URL);
224 printf("\nOptional features enabled:%s\n",
225 features[0] ? features : " (none)");
232 usage: strace [-CdffhiqrtttTvVwxxy] [-I n] [-e expr]...\n\
233 [-a column] [-o file] [-s strsize] [-P path]...\n\
234 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
235 or: strace -c[dfw] [-I n] [-e expr]... [-O overhead] [-S sortby]\n\
236 -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
239 -a column alignment COLUMN for printing syscall results (default %d)\n\
240 -i print instruction pointer at time of syscall\n\
242 #ifdef ENABLE_STACKTRACE
244 -k obtain stack trace between each syscall\n\
248 -o file send trace output to FILE instead of stderr\n\
249 -q suppress messages about attaching, detaching, etc.\n\
250 -r print relative timestamp\n\
251 -s strsize limit length of print strings to STRSIZE chars (default %d)\n\
252 -t print absolute timestamp\n\
253 -tt print absolute timestamp with usecs\n\
254 -T print time spent in each syscall\n\
255 -x print non-ascii strings in hex\n\
256 -xx print all strings in hex\n\
257 -X format set the format for printing of named constants and flags\n\
258 -y print paths associated with file descriptor arguments\n\
259 -yy print protocol specific information associated with socket file descriptors\n\
262 -c count time, calls, and errors for each syscall and report summary\n\
263 -C like -c but also print regular output\n\
264 -O overhead set overhead for tracing syscalls to OVERHEAD usecs\n\
265 -S sortby sort syscall counts by: time, calls, name, nothing (default %s)\n\
266 -w summarise syscall latency (default is system time)\n\
269 -e expr a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
270 options: trace, abbrev, verbose, raw, signal, read, write, fault, inject, kvm"
272 -P path trace accesses to path\n\
275 -b execve detach on execve syscall\n\
276 -D run tracer process as a detached grandchild, not as parent\n\
278 -ff follow forks with output into separate files\n\
280 1: no signals are blocked\n\
281 2: fatal signals are blocked while decoding syscall (default)\n\
282 3: fatal signals are always blocked (default if '-o FILE PROG')\n\
283 4: fatal signals and SIGTSTP (^Z) are always blocked\n\
284 (useful to make 'strace -o FILE PROG' not stop on ^Z)\n\
287 -E var remove var from the environment for command\n\
288 -E var=val put var=val in the environment for command\n\
289 -p pid trace process with process id PID, may be repeated\n\
290 -u username run command as username handling setuid and/or setgid\n\
293 -d enable debug output to stderr\n\
294 -v verbose mode: print unabbreviated argv, stat, termios, etc. args\n\
295 -h print help message\n\
298 /* ancient, no one should use it
299 -F -- attempt to follow vforks (deprecated, use -f)\n\
301 /* this is broken, so don't document it
302 -z -- print only succeeding syscalls\n\
304 , DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
308 void ATTRIBUTE_NORETURN
311 if (strace_tracer_pid == getpid()) {
321 error_opt_arg(int opt, const char *arg)
323 error_msg_and_help("invalid -%c argument: '%s'", opt, arg);
326 static const char *ptrace_attach_cmd;
329 ptrace_attach_or_seize(int pid)
333 return ptrace_attach_cmd = "PTRACE_ATTACH",
334 ptrace(PTRACE_ATTACH, pid, 0L, 0L);
335 r = ptrace(PTRACE_SEIZE, pid, 0L, (unsigned long) ptrace_setoptions);
337 return ptrace_attach_cmd = "PTRACE_SEIZE", r;
338 r = ptrace(PTRACE_INTERRUPT, pid, 0L, 0L);
339 return ptrace_attach_cmd = "PTRACE_INTERRUPT", r;
343 ptrace_op_str(unsigned int op)
345 const char *str = xlookup(ptrace_cmds, op);
349 static char buf[sizeof(op) * 3];
350 xsprintf(buf, "%u", op);
355 * Used when we want to unblock stopped traced process.
356 * Should be only used with PTRACE_CONT, PTRACE_DETACH and PTRACE_SYSCALL.
357 * Returns 0 on success or if error was ESRCH
358 * (presumably process was killed while we talk to it).
359 * Otherwise prints error message and returns -1.
362 ptrace_restart(const unsigned int op, struct tcb *const tcp, unsigned int sig)
367 ptrace(op, tcp->pid, 0L, (unsigned long) sig);
369 if (!err || err == ESRCH)
373 * Why curcol != 0? Otherwise sometimes we get this:
375 * 10252 kill(10253, SIGKILL) = 0
376 * <ptrace(SYSCALL,10252):No such process>10253 ...next decode...
378 * 10252 died after we retrieved syscall exit data,
379 * but before we tried to restart it. Log looks ugly.
381 if (current_tcp && current_tcp->curcol != 0) {
382 tprintf(" <Cannot restart pid %d with ptrace(%s): %s>\n",
383 tcp->pid, ptrace_op_str(op), strerror(err));
387 perror_msg("ptrace(%s,pid:%d,sig:%u)",
388 ptrace_op_str(op), tcp->pid, sig);
393 set_cloexec_flag(int fd)
397 flags = fcntl(fd, F_GETFD);
399 /* Can happen only if fd is bad.
400 * Should never happen: if it does, we have a bug
401 * in the caller. Therefore we just abort
402 * instead of propagating the error.
404 perror_msg_and_die("fcntl(%d, F_GETFD)", fd);
407 newflags = flags | FD_CLOEXEC;
408 if (flags == newflags)
411 if (fcntl(fd, F_SETFD, newflags)) /* never fails */
412 perror_msg_and_die("fcntl(%d, F_SETFD, %#x)", fd, newflags);
416 * When strace is setuid executable, we have to swap uids
417 * before and after filesystem and process management operations.
422 int euid = geteuid(), uid = getuid();
424 if (euid != uid && setreuid(euid, uid) < 0) {
425 perror_msg_and_die("setreuid");
430 strace_fopen(const char *path)
435 fp = fopen_stream(path, open_append ? "a" : "w");
437 perror_msg_and_die("Can't fopen '%s'", path);
439 set_cloexec_flag(fileno(fp));
443 static int popen_pid;
446 # define _PATH_BSHELL "/bin/sh"
450 * We cannot use standard popen(3) here because we have to distinguish
451 * popen child process from other processes we trace, and standard popen(3)
452 * does not export its child's pid.
455 strace_popen(const char *command)
463 perror_msg_and_die("pipe");
465 set_cloexec_flag(fds[1]); /* never fails */
469 perror_msg_and_die("vfork");
476 perror_msg_and_die("dup2");
479 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
480 perror_msg_and_die("Can't execute '%s'", _PATH_BSHELL);
487 fp = fdopen(fds[1], "w");
489 perror_msg_and_die("fdopen");
494 outf_perror(const struct tcb * const tcp)
496 if (tcp->outf == stderr)
499 /* This is ugly, but we don't store separate file names */
501 perror_msg("%s.%u", outfname, tcp->pid);
503 perror_msg("%s", outfname);
506 ATTRIBUTE_FORMAT((printf, 1, 0))
508 tvprintf(const char *const fmt, va_list args)
511 int n = vfprintf(current_tcp->outf, fmt, args);
513 /* very unlikely due to vfprintf buffering */
514 outf_perror(current_tcp);
516 current_tcp->curcol += n;
521 tprintf(const char *fmt, ...)
529 #ifndef HAVE_FPUTS_UNLOCKED
530 # define fputs_unlocked fputs
534 tprints(const char *str)
537 int n = fputs_unlocked(str, current_tcp->outf);
539 current_tcp->curcol += strlen(str);
542 /* very unlikely due to fputs_unlocked buffering */
543 outf_perror(current_tcp);
548 tprints_comment(const char *const str)
551 tprintf(" /* %s */", str);
555 tprintf_comment(const char *fmt, ...)
569 flush_tcp_output(const struct tcb *const tcp)
571 if (fflush(tcp->outf))
579 current_tcp->curcol = 0;
580 flush_tcp_output(current_tcp);
583 printing_tcp->curcol = 0;
589 set_current_tcp(const struct tcb *tcp)
591 current_tcp = (struct tcb *) tcp;
593 /* Sync current_personality and stuff */
595 set_personality(current_tcp->currpers);
599 printleader(struct tcb *tcp)
601 /* If -ff, "previous tcb we printed" is always the same as current,
602 * because we have per-tcb output files.
608 set_current_tcp(printing_tcp);
609 if (printing_tcp->curcol != 0 && (followfork < 2 || printing_tcp == tcp)) {
611 * case 1: we have a shared log (i.e. not -ff), and last line
612 * wasn't finished (same or different tcb, doesn't matter).
613 * case 2: split log, we are the same tcb, but our last line
614 * didn't finish ("SIGKILL nuked us after syscall entry" etc).
616 tprints(" <unfinished ...>\n");
617 printing_tcp->curcol = 0;
622 set_current_tcp(tcp);
623 current_tcp->curcol = 0;
626 tprintf("%-5d ", tcp->pid);
627 else if (nprocs > 1 && !outfname)
628 tprintf("[pid %5u] ", tcp->pid);
632 clock_gettime(CLOCK_REALTIME, &ts);
635 tprintf("%lld.%06ld ",
636 (long long) ts.tv_sec, (long) ts.tv_nsec / 1000);
638 time_t local = ts.tv_sec;
639 char str[MAX(sizeof("HH:MM:SS"), sizeof(ts.tv_sec) * 3)];
640 struct tm *tm = localtime(&local);
643 strftime(str, sizeof(str), "%T", tm);
645 xsprintf(str, "%lld", (long long) local);
648 str, (long) ts.tv_nsec / 1000);
656 clock_gettime(CLOCK_MONOTONIC, &ts);
658 static struct timespec ots;
663 ts_sub(&dts, &ts, &ots);
666 tprintf("%s%6ld.%06ld%s ",
668 (long) dts.tv_sec, (long) dts.tv_nsec / 1000,
673 print_instruction_pointer(tcp);
679 if (current_tcp->curcol < acolumn)
680 tprints(acolumn_spaces + current_tcp->curcol);
683 /* Should be only called directly *after successful attach* to a tracee.
684 * Otherwise, "strace -oFILE -ff -p<nonexistant_pid>"
685 * may create bogus empty FILE.<nonexistant_pid>, and then die.
688 after_successful_attach(struct tcb *tcp, const unsigned int flags)
690 tcp->flags |= TCB_ATTACHED | TCB_STARTUP | flags;
691 tcp->outf = shared_log; /* if not -ff mode, the same file is for all */
692 if (followfork >= 2) {
694 xsprintf(name, "%s.%u", outfname, tcp->pid);
695 tcp->outf = strace_fopen(name);
698 #ifdef ENABLE_STACKTRACE
699 if (stack_trace_enabled)
700 unwind_tcb_init(tcp);
707 /* Allocate some (more) TCBs (and expand the table).
708 We don't want to relocate the TCBs because our
709 callers have pointers and it would be a pain.
710 So tcbtab is a table of pointers. Since we never
711 free the TCBs, we allocate a single chunk of many. */
712 size_t old_tcbtabsize;
714 struct tcb **tcb_ptr;
716 old_tcbtabsize = tcbtabsize;
718 tcbtab = xgrowarray(tcbtab, &tcbtabsize, sizeof(tcbtab[0]));
719 newtcbs = xcalloc(tcbtabsize - old_tcbtabsize, sizeof(newtcbs[0]));
721 for (tcb_ptr = tcbtab + old_tcbtabsize;
722 tcb_ptr < tcbtab + tcbtabsize; tcb_ptr++, 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;
744 debug_msg("new tcb for pid %d, active tcbs:%d",
749 error_msg_and_die("bug in alloctcb");
753 get_tcb_priv_data(const struct tcb *tcp)
755 return tcp->_priv_data;
759 set_tcb_priv_data(struct tcb *tcp, void *const priv_data,
760 void (*const free_priv_data)(void *))
765 tcp->_free_priv_data = free_priv_data;
766 tcp->_priv_data = priv_data;
772 free_tcb_priv_data(struct tcb *tcp)
774 if (tcp->_priv_data) {
775 if (tcp->_free_priv_data) {
776 tcp->_free_priv_data(tcp->_priv_data);
777 tcp->_free_priv_data = NULL;
779 tcp->_priv_data = NULL;
784 droptcb(struct tcb *tcp)
790 for (p = 0; p < SUPPORTED_PERSONALITIES; ++p)
791 free(tcp->inject_vec[p]);
793 free_tcb_priv_data(tcp);
795 #ifdef ENABLE_STACKTRACE
796 if (stack_trace_enabled)
800 #ifdef HAVE_LINUX_KVM_H
801 kvm_vcpu_info_free(tcp);
805 tcp->mmap_cache->free_fn(tcp, __func__);
808 debug_msg("dropped tcb for pid %d, %d remain", tcp->pid, nprocs);
811 if (followfork >= 2) {
812 if (tcp->curcol != 0)
813 fprintf(tcp->outf, " <detached ...>\n");
816 if (printing_tcp == tcp && tcp->curcol != 0)
817 fprintf(tcp->outf, " <detached ...>\n");
818 flush_tcp_output(tcp);
822 if (current_tcp == tcp)
823 set_current_tcp(NULL);
824 if (printing_tcp == tcp)
827 memset(tcp, 0, sizeof(*tcp));
830 /* Detach traced process.
831 * Never call DETACH twice on the same process as both unattached and
832 * attached-unstopped processes give the same ESRCH. For unattached process we
833 * would SIGSTOP it and wait for its SIGSTOP notification forever.
836 detach(struct tcb *tcp)
842 * Linux wrongly insists the child be stopped
843 * before detaching. Arghh. We go through hoops
844 * to make a clean break of things.
847 if (!(tcp->flags & TCB_ATTACHED))
850 /* We attached but possibly didn't see the expected SIGSTOP.
851 * We must catch exactly one as otherwise the detached process
852 * would be left stopped (process state T).
854 if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
857 error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
859 /* On a clear day, you can see forever. */
862 if (errno != ESRCH) {
863 /* Shouldn't happen. */
864 perror_func_msg("ptrace(PTRACE_DETACH,%u)", tcp->pid);
867 /* ESRCH: process is either not stopped or doesn't exist. */
868 if (my_tkill(tcp->pid, 0) < 0) {
870 /* Shouldn't happen. */
871 perror_func_msg("tkill(%u,0)", tcp->pid);
872 /* else: process doesn't exist. */
875 /* Process is not stopped, need to stop it. */
878 * With SEIZE, tracee can be in group-stop already.
879 * In this state sending it another SIGSTOP does nothing.
880 * Need to use INTERRUPT.
881 * Testcase: trying to ^C a "strace -p <stopped_process>".
883 error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
887 perror_func_msg("ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
889 error = my_tkill(tcp->pid, SIGSTOP);
893 perror_func_msg("tkill(%u,SIGSTOP)", tcp->pid);
895 /* Either process doesn't exist, or some weird error. */
899 /* We end up here in three cases:
900 * 1. We sent PTRACE_INTERRUPT (use_seize case)
901 * 2. We sent SIGSTOP (!use_seize)
902 * 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
906 if (waitpid(tcp->pid, &status, __WALL) < 0) {
910 * if (errno == ECHILD) break;
911 * ^^^ WRONG! We expect this PID to exist,
912 * and want to emit a message otherwise:
914 perror_func_msg("waitpid(%u)", tcp->pid);
917 if (!WIFSTOPPED(status)) {
919 * Tracee exited or was killed by signal.
920 * We shouldn't normally reach this place:
921 * we don't want to consume exit status.
922 * Consider "strace -p PID" being ^C-ed:
923 * we want merely to detach from PID.
925 * However, we _can_ end up here if tracee
930 sig = WSTOPSIG(status);
931 debug_msg("detach wait: event:%d sig:%d",
932 (unsigned) status >> 16, sig);
934 unsigned event = (unsigned)status >> 16;
935 if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
937 * sig == SIGTRAP: PTRACE_INTERRUPT stop.
938 * sig == other: process was already stopped
939 * with this stopping sig (see tests/detach-stopped).
940 * Looks like re-injecting this sig is not necessary
941 * in DETACH for the tracee to remain stopped.
946 * PTRACE_INTERRUPT is not guaranteed to produce
947 * the above event if other ptrace-stop is pending.
948 * See tests/detach-sleeping testcase:
949 * strace got SIGINT while tracee is sleeping.
950 * We sent PTRACE_INTERRUPT.
951 * We see syscall exit, not PTRACE_INTERRUPT stop.
952 * We won't get PTRACE_INTERRUPT stop
953 * if we would CONT now. Need to DETACH.
955 if (sig == syscall_trap_sig)
957 /* else: not sure in which case we can be here.
958 * Signal stop? Inject it while detaching.
960 ptrace_restart(PTRACE_DETACH, tcp, sig);
963 /* Note: this check has to be after use_seize check */
964 /* (else, in use_seize case SIGSTOP will be mistreated) */
965 if (sig == SIGSTOP) {
966 /* Detach, suppressing SIGSTOP */
967 ptrace_restart(PTRACE_DETACH, tcp, 0);
970 if (sig == syscall_trap_sig)
972 /* Can't detach just yet, may need to wait for SIGSTOP */
973 error = ptrace_restart(PTRACE_CONT, tcp, sig);
975 /* Should not happen.
976 * Note: ptrace_restart returns 0 on ESRCH, so it's not it.
977 * ptrace_restart already emitted error message.
984 if (!qflag && (tcp->flags & TCB_ATTACHED))
985 error_msg("Process %u detached", tcp->pid);
991 process_opt_p_list(char *opt)
995 * We accept -p PID,PID; -p "`pidof PROG`"; -p "`pgrep PROG`".
996 * pidof uses space as delim, pgrep uses newline. :(
999 char *delim = opt + strcspn(opt, "\n\t ,");
1003 pid = string_to_uint(opt);
1005 error_msg_and_die("Invalid process id: '%s'", opt);
1007 if (pid == strace_tracer_pid) {
1008 error_msg_and_die("I'm sorry, I can't let you do that, Dave.");
1019 attach_tcb(struct tcb *const tcp)
1021 if (ptrace_attach_or_seize(tcp->pid) < 0) {
1022 perror_msg("attach: ptrace(%s, %d)",
1023 ptrace_attach_cmd, tcp->pid);
1028 after_successful_attach(tcp, TCB_GRABBED | post_attach_sigstop);
1029 debug_msg("attach to pid %d (main) succeeded", tcp->pid);
1031 static const char task_path[] = "/proc/%d/task";
1032 char procdir[sizeof(task_path) + sizeof(int) * 3];
1034 unsigned int ntid = 0, nerr = 0;
1036 if (followfork && tcp->pid != strace_child &&
1037 xsprintf(procdir, task_path, tcp->pid) > 0 &&
1038 (dir = opendir(procdir)) != NULL) {
1041 while ((de = read_dir(dir)) != NULL) {
1042 if (de->d_fileno == 0)
1045 int tid = string_to_uint(de->d_name);
1046 if (tid <= 0 || tid == tcp->pid)
1050 if (ptrace_attach_or_seize(tid) < 0) {
1052 debug_perror_msg("attach: ptrace(%s, %d)",
1053 ptrace_attach_cmd, tid);
1057 after_successful_attach(alloctcb(tid),
1058 TCB_GRABBED | post_attach_sigstop);
1059 debug_msg("attach to pid %d succeeded", tid);
1067 error_msg("Process %u attached"
1069 tcp->pid, ntid - nerr + 1);
1071 error_msg("Process %u attached",
1077 startup_attach(void)
1079 pid_t parent_pid = strace_tracer_pid;
1083 if (daemonized_tracer) {
1086 perror_func_msg_and_die("fork");
1088 if (pid) { /* parent */
1090 * Wait for grandchild to attach to straced process
1091 * (grandparent). Grandchild SIGKILLs us after it attached.
1092 * Grandparent's wait() is unblocked by our death,
1093 * it proceeds to exec the straced program.
1096 _exit(0); /* paranoia */
1099 /* We will be the tracer process. Remember our new pid: */
1100 strace_tracer_pid = getpid();
1103 for (tcbi = 0; tcbi < tcbtabsize; tcbi++) {
1109 /* Is this a process we should attach to, but not yet attached? */
1110 if (tcp->flags & TCB_ATTACHED)
1111 continue; /* no, we already attached it */
1113 if (tcp->pid == parent_pid || tcp->pid == strace_tracer_pid) {
1115 perror_msg("attach: pid %d", tcp->pid);
1124 } /* for each tcbtab[] */
1126 if (daemonized_tracer) {
1128 * Make parent go away.
1129 * Also makes grandparent's wait() unblock.
1131 kill(parent_pid, SIGKILL);
1136 /* Stack-o-phobic exec helper, in the hope to work around
1137 * NOMMU + "daemonized tracer" difficulty.
1139 struct exec_params {
1145 struct sigaction child_sa;
1147 static struct exec_params params_for_tracee;
1149 static void ATTRIBUTE_NOINLINE ATTRIBUTE_NORETURN
1152 struct exec_params *params = ¶ms_for_tracee;
1154 if (params->fd_to_close >= 0)
1155 close(params->fd_to_close);
1156 if (!daemonized_tracer && !use_seize) {
1157 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0) {
1158 perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
1162 if (username != NULL) {
1164 * It is important to set groups before we
1165 * lose privileges on setuid.
1167 if (initgroups(username, run_gid) < 0) {
1168 perror_msg_and_die("initgroups");
1170 if (setregid(run_gid, params->run_egid) < 0) {
1171 perror_msg_and_die("setregid");
1173 if (setreuid(run_uid, params->run_euid) < 0) {
1174 perror_msg_and_die("setreuid");
1176 } else if (geteuid() != 0)
1177 if (setreuid(run_uid, run_uid) < 0) {
1178 perror_msg_and_die("setreuid");
1181 if (!daemonized_tracer) {
1183 * Induce a ptrace stop. Tracer (our parent)
1184 * will resume us with PTRACE_SYSCALL and display
1185 * the immediately following execve syscall.
1186 * Can't do this on NOMMU systems, we are after
1187 * vfork: parent is blocked, stopping would deadlock.
1190 kill(getpid(), SIGSTOP);
1193 /* we depend on SIGCHLD set to SIG_DFL by init code */
1194 /* if it happens to be SIG_IGN'ed, wait won't block */
1199 if (params_for_tracee.child_sa.sa_handler != SIG_DFL)
1200 sigaction(SIGCHLD, ¶ms_for_tracee.child_sa, NULL);
1202 execv(params->pathname, params->argv);
1203 perror_msg_and_die("exec");
1207 * Open a dummy descriptor for use as a placeholder.
1208 * The descriptor is O_RDONLY with FD_CLOEXEC flag set.
1209 * A read attempt from such descriptor ends with EOF,
1210 * a write attempt is rejected with EBADF.
1213 open_dummy_desc(void)
1218 perror_func_msg_and_die("pipe");
1220 set_cloexec_flag(fds[0]);
1224 /* placeholder fds status for stdin and stdout */
1225 static bool fd_is_placeholder[2];
1228 * Ensure that all standard file descriptors are open by opening placeholder
1229 * file descriptors for those standard file descriptors that are not open.
1231 * The information which descriptors have been made open is saved
1232 * in fd_is_placeholder for later use.
1235 ensure_standard_fds_opened(void)
1239 while ((fd = open_dummy_desc()) <= 2) {
1242 fd_is_placeholder[fd] = true;
1250 * Redirect stdin and stdout unless they have been opened earlier
1251 * by ensure_standard_fds_opened as placeholders.
1254 redirect_standard_fds(void)
1259 * It might be a good idea to redirect stderr as well,
1260 * but we sometimes need to print error messages.
1262 for (i = 0; i <= 1; ++i) {
1263 if (!fd_is_placeholder[i]) {
1271 startup_child(char **argv)
1273 struct_stat statbuf;
1274 const char *filename;
1275 size_t filename_len;
1276 char pathname[PATH_MAX];
1281 filename_len = strlen(filename);
1283 if (filename_len > sizeof(pathname) - 1) {
1284 errno = ENAMETOOLONG;
1285 perror_msg_and_die("exec");
1287 if (strchr(filename, '/')) {
1288 strcpy(pathname, filename);
1290 #ifdef USE_DEBUGGING_EXEC
1292 * Debuggers customarily check the current directory
1293 * first regardless of the path but doing that gives
1294 * security geeks a panic attack.
1296 else if (stat_file(filename, &statbuf) == 0)
1297 strcpy(pathname, filename);
1298 #endif /* USE_DEBUGGING_EXEC */
1303 for (path = getenv("PATH"); path && *path; path += m) {
1304 const char *colon = strchr(path, ':');
1309 m = n = strlen(path);
1311 if (!getcwd(pathname, PATH_MAX))
1313 len = strlen(pathname);
1314 } else if (n > sizeof(pathname) - 1)
1317 strncpy(pathname, path, n);
1320 if (len && pathname[len - 1] != '/')
1321 pathname[len++] = '/';
1322 if (filename_len + len > sizeof(pathname) - 1)
1324 strcpy(pathname + len, filename);
1325 if (stat_file(pathname, &statbuf) == 0 &&
1326 /* Accept only regular files
1327 with some execute bits set.
1328 XXX not perfect, might still fail */
1329 S_ISREG(statbuf.st_mode) &&
1330 (statbuf.st_mode & 0111))
1333 if (!path || !*path)
1336 if (stat_file(pathname, &statbuf) < 0) {
1337 perror_msg_and_die("Can't stat '%s'", filename);
1340 params_for_tracee.fd_to_close = (shared_log != stderr) ? fileno(shared_log) : -1;
1341 params_for_tracee.run_euid = (statbuf.st_mode & S_ISUID) ? statbuf.st_uid : run_uid;
1342 params_for_tracee.run_egid = (statbuf.st_mode & S_ISGID) ? statbuf.st_gid : run_gid;
1343 params_for_tracee.argv = argv;
1345 * On NOMMU, can be safely freed only after execve in tracee.
1346 * It's hard to know when that happens, so we just leak it.
1348 params_for_tracee.pathname = NOMMU_SYSTEM ? xstrdup(pathname) : pathname;
1350 #if defined HAVE_PRCTL && defined PR_SET_PTRACER && defined PR_SET_PTRACER_ANY
1351 if (daemonized_tracer)
1352 prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
1357 perror_func_msg_and_die("fork");
1359 if ((pid != 0 && daemonized_tracer)
1360 || (pid == 0 && !daemonized_tracer)
1362 /* We are to become the tracee. Two cases:
1364 * not -D: we are child
1369 /* We are the tracer */
1371 if (!daemonized_tracer) {
1374 /* child did PTRACE_TRACEME, nothing to do in parent */
1376 if (!NOMMU_SYSTEM) {
1377 /* Wait until child stopped itself */
1379 while (waitpid(pid, &status, WSTOPPED) < 0) {
1382 perror_msg_and_die("waitpid");
1384 if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGSTOP) {
1385 kill_save_errno(pid, SIGKILL);
1386 perror_msg_and_die("Unexpected wait status %#x",
1390 /* Else: NOMMU case, we have no way to sync.
1391 * Just attach to it as soon as possible.
1392 * This means that we may miss a few first syscalls...
1395 if (ptrace_attach_or_seize(pid)) {
1396 kill_save_errno(pid, SIGKILL);
1397 perror_msg_and_die("attach: ptrace(%s, %d)",
1398 ptrace_attach_cmd, pid);
1403 tcp = alloctcb(pid);
1404 after_successful_attach(tcp, TCB_SKIP_DETACH_ON_FIRST_EXEC
1407 | post_attach_sigstop)));
1409 /* With -D, we are *child* here, the tracee is our parent. */
1410 strace_child = strace_tracer_pid;
1411 strace_tracer_pid = getpid();
1412 tcp = alloctcb(strace_child);
1413 tcp->flags |= TCB_SKIP_DETACH_ON_FIRST_EXEC | TCB_HIDE_LOG;
1415 * Attaching will be done later, by startup_attach.
1416 * Note: we don't do after_successful_attach() here either!
1419 /* NOMMU BUG! -D mode is active, we (child) return,
1420 * and we will scribble over parent's stack!
1421 * When parent later unpauses, it segfaults.
1424 * (1) by declaring exec_or_die() NORETURN,
1425 * hopefully compiler will just jump to it
1426 * instead of call (won't push anything to stack),
1427 * (2) by trying very hard in exec_or_die()
1428 * to not use any stack,
1429 * (3) having a really big (PATH_MAX) stack object
1430 * in this function, which creates a "buffer" between
1431 * child's and parent's stack pointers.
1432 * This may save us if (1) and (2) failed
1433 * and compiler decided to use stack in exec_or_die() anyway
1434 * (happens on i386 because of stack parameter passing).
1436 * A cleaner solution is to use makecontext + setcontext
1437 * to create a genuine separate stack and execute on it.
1441 * A case where straced process is part of a pipe:
1442 * { sleep 1; yes | head -n99999; } | strace -o/dev/null sh -c 'exec <&-; sleep 9'
1443 * If strace won't close its fd#0, closing it in tracee is not enough:
1444 * the pipe is still open, it has a reader. Thus, "head" will not get its
1445 * SIGPIPE at once, on the first write.
1447 * Preventing it by redirecting strace's stdin/out.
1448 * (Don't leave fds 0 and 1 closed, this is bad practice: future opens
1449 * will reuse them, unexpectedly making a newly opened object "stdin").
1451 redirect_standard_fds();
1455 test_ptrace_seize(void)
1459 /* Need fork for test. NOMMU has no forks */
1461 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1467 perror_func_msg_and_die("fork");
1474 /* PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After
1475 * attaching tracee continues to run unless a trap condition occurs.
1476 * PTRACE_SEIZE doesn't affect signal or group stop state.
1478 if (ptrace(PTRACE_SEIZE, pid, 0, 0) == 0) {
1479 post_attach_sigstop = 0; /* this sets use_seize to 1 */
1481 debug_msg("PTRACE_SEIZE doesn't work");
1487 int status, tracee_pid;
1490 tracee_pid = waitpid(pid, &status, 0);
1491 if (tracee_pid <= 0) {
1494 perror_func_msg_and_die("unexpected wait result %d",
1497 if (WIFSIGNALED(status))
1500 error_func_msg_and_die("unexpected wait status %#x", status);
1505 get_os_release(void)
1511 perror_msg_and_die("uname");
1512 /* u.release has this form: "3.2.9[-some-garbage]" */
1516 if (!(*p >= '0' && *p <= '9'))
1517 error_msg_and_die("Bad OS release string: '%s'", u.release);
1518 /* Note: this open-codes KERNEL_VERSION(): */
1519 rel = (rel << 8) | atoi(p);
1520 if (rel >= KERNEL_VERSION(1, 0, 0))
1522 while (*p >= '0' && *p <= '9')
1525 if (rel >= KERNEL_VERSION(0, 1, 0)) {
1526 /* "X.Y-something" means "X.Y.0" */
1530 error_msg_and_die("Bad OS release string: '%s'", u.release);
1538 set_sighandler(int signo, void (*sighandler)(int), struct sigaction *oldact)
1540 const struct sigaction sa = { .sa_handler = sighandler };
1541 sigaction(signo, &sa, oldact);
1545 * Initialization part of main() was eating much stack (~0.5k),
1546 * which was unused after init.
1547 * We can reuse it if we move init code into a separate function.
1549 * Don't want main() to inline us and defeat the reason
1550 * we have a separate function.
1552 static void ATTRIBUTE_NOINLINE
1553 init(int argc, char *argv[])
1558 if (!program_invocation_name || !*program_invocation_name) {
1559 static char name[] = "strace";
1560 program_invocation_name =
1561 (argc > 0 && argv[0] && *argv[0]) ? argv[0] : name;
1564 strace_tracer_pid = getpid();
1566 os_release = get_os_release();
1568 shared_log = stderr;
1569 set_sortby(DEFAULT_SORTBY);
1570 set_personality(DEFAULT_PERSONALITY);
1571 qualify("trace=all");
1572 qualify("abbrev=all");
1573 qualify("verbose=all");
1574 #if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
1575 # error Bug in DEFAULT_QUAL_FLAGS
1577 qualify("signal=all");
1578 while ((c = getopt(argc, argv, "+"
1579 #ifdef ENABLE_STACKTRACE
1582 "a:Ab:cCdDe:E:fFhiI:o:O:p:P:qrs:S:tTu:vVwxX:yz")) != EOF) {
1585 acolumn = string_to_uint(optarg);
1587 error_opt_arg(c, optarg);
1593 if (strcmp(optarg, "execve") != 0)
1594 error_msg_and_die("Syscall '%s' for -b isn't supported",
1596 detach_on_execve = 1;
1599 if (cflag == CFLAG_BOTH) {
1600 error_msg_and_help("-c and -C are mutually exclusive");
1602 cflag = CFLAG_ONLY_STATS;
1605 if (cflag == CFLAG_ONLY_STATS) {
1606 error_msg_and_help("-c and -C are mutually exclusive");
1614 daemonized_tracer = 1;
1620 if (putenv(optarg) < 0)
1621 perror_msg_and_die("putenv");
1636 opt_intr = string_to_uint_upto(optarg, NUM_INTR_OPTS - 1);
1638 error_opt_arg(c, optarg);
1640 #ifdef ENABLE_STACKTRACE
1642 stack_trace_enabled = true;
1649 i = string_to_uint(optarg);
1651 error_opt_arg(c, optarg);
1655 process_opt_p_list(optarg);
1658 pathtrace_select(optarg);
1667 i = string_to_uint(optarg);
1668 if (i < 0 || (unsigned int) i > -1U / 4)
1669 error_opt_arg(c, optarg);
1685 qualify("abbrev=none");
1692 count_wallclock = 1;
1698 if (!strcmp(optarg, "raw"))
1699 xlat_verbosity = XLAT_STYLE_RAW;
1700 else if (!strcmp(optarg, "abbrev"))
1701 xlat_verbosity = XLAT_STYLE_ABBREV;
1702 else if (!strcmp(optarg, "verbose"))
1703 xlat_verbosity = XLAT_STYLE_VERBOSE;
1705 error_opt_arg(c, optarg);
1711 not_failing_only = 1;
1714 error_msg_and_help(NULL);
1722 if (argc < 0 || (!nprocs && !argc)) {
1723 error_msg_and_help("must have PROG [ARGS] or -p PID");
1726 if (!argc && daemonized_tracer) {
1727 error_msg_and_help("PROG [ARGS] must be specified with -D");
1732 error_msg("deprecated option -F ignored");
1734 error_msg("option -F is deprecated, "
1735 "please use -f instead");
1740 if (followfork >= 2 && cflag) {
1741 error_msg_and_help("(-c or -C) and -ff are mutually exclusive");
1744 if (count_wallclock && !cflag) {
1745 error_msg_and_help("-w must be given with (-c or -C)");
1748 if (cflag == CFLAG_ONLY_STATS) {
1750 error_msg("-%c has no effect with -c", 'i');
1751 if (stack_trace_enabled)
1752 error_msg("-%c has no effect with -c", 'k');
1754 error_msg("-%c has no effect with -c", 'r');
1756 error_msg("-%c has no effect with -c", 't');
1758 error_msg("-%c has no effect with -c", 'T');
1760 error_msg("-%c has no effect with -c", 'y');
1763 acolumn_spaces = xmalloc(acolumn + 1);
1764 memset(acolumn_spaces, ' ', acolumn);
1765 acolumn_spaces[acolumn] = '\0';
1767 set_sighandler(SIGCHLD, SIG_DFL, ¶ms_for_tracee.child_sa);
1769 #ifdef ENABLE_STACKTRACE
1770 if (stack_trace_enabled)
1774 /* See if they want to run as another user. */
1775 if (username != NULL) {
1776 struct passwd *pent;
1778 if (getuid() != 0 || geteuid() != 0) {
1779 error_msg_and_die("You must be root to use the -u option");
1781 pent = getpwnam(username);
1783 error_msg_and_die("Cannot find user '%s'", username);
1785 run_uid = pent->pw_uid;
1786 run_gid = pent->pw_gid;
1793 ptrace_setoptions |= PTRACE_O_TRACECLONE |
1794 PTRACE_O_TRACEFORK |
1795 PTRACE_O_TRACEVFORK;
1796 debug_msg("ptrace_setoptions = %#x", ptrace_setoptions);
1797 test_ptrace_seize();
1798 test_ptrace_get_syscall_info();
1801 * Is something weird with our stdin and/or stdout -
1802 * for example, may they be not open? In this case,
1803 * ensure that none of the future opens uses them.
1805 * This was seen in the wild when /proc/sys/kernel/core_pattern
1806 * was set to "|/bin/strace -o/tmp/LOG PROG":
1807 * kernel runs coredump helper with fd#0 open but fd#1 closed (!),
1808 * therefore LOG gets opened to fd#1, and fd#1 is closed by
1809 * "don't hold up stdin/out open" code soon after.
1811 ensure_standard_fds_opened();
1813 /* Check if they want to redirect the output. */
1815 /* See if they want to pipe the output. */
1816 if (outfname[0] == '|' || outfname[0] == '!') {
1818 * We can't do the <outfname>.PID funny business
1819 * when using popen, so prohibit it.
1821 if (followfork >= 2)
1822 error_msg_and_help("piping the output and -ff "
1823 "are mutually exclusive");
1824 shared_log = strace_popen(outfname + 1);
1825 } else if (followfork < 2) {
1826 shared_log = strace_fopen(outfname);
1827 } else if (strlen(outfname) >= PATH_MAX - sizeof(int) * 3) {
1828 errno = ENAMETOOLONG;
1829 perror_msg_and_die("%s", outfname);
1832 /* -ff without -o FILE is the same as single -f */
1833 if (followfork >= 2)
1837 if (!outfname || outfname[0] == '|' || outfname[0] == '!') {
1838 setvbuf(shared_log, NULL, _IOLBF, 0);
1842 * argv[0] -pPID -oFILE Default interactive setting
1843 * yes * 0 INTR_WHILE_WAIT
1844 * no 1 0 INTR_WHILE_WAIT
1845 * yes * 1 INTR_NEVER
1846 * no 1 1 INTR_WHILE_WAIT
1849 if (outfname && argc) {
1851 opt_intr = INTR_NEVER;
1856 opt_intr = INTR_WHILE_WAIT;
1859 * startup_child() must be called before the signal handlers get
1860 * installed below as they are inherited into the spawned process.
1861 * Also we do not need to be protected by them as during interruption
1862 * in the startup_child() mode we kill the spawned process anyway.
1865 startup_child(argv);
1868 set_sighandler(SIGTTOU, SIG_IGN, NULL);
1869 set_sighandler(SIGTTIN, SIG_IGN, NULL);
1870 if (opt_intr != INTR_ANYWHERE) {
1871 if (opt_intr == INTR_BLOCK_TSTP_TOO)
1872 set_sighandler(SIGTSTP, SIG_IGN, NULL);
1874 * In interactive mode (if no -o OUTFILE, or -p PID is used),
1875 * fatal signals are handled asynchronously and acted
1876 * when waiting for process state changes.
1877 * In non-interactive mode these signals are ignored.
1879 set_sighandler(SIGHUP, interactive ? interrupt : SIG_IGN, NULL);
1880 set_sighandler(SIGINT, interactive ? interrupt : SIG_IGN, NULL);
1881 set_sighandler(SIGQUIT, interactive ? interrupt : SIG_IGN, NULL);
1882 set_sighandler(SIGPIPE, interactive ? interrupt : SIG_IGN, NULL);
1883 set_sighandler(SIGTERM, interactive ? interrupt : SIG_IGN, NULL);
1886 sigemptyset(&timer_set);
1887 sigaddset(&timer_set, SIGALRM);
1888 sigprocmask(SIG_BLOCK, &timer_set, NULL);
1889 set_sighandler(SIGALRM, timer_sighandler, NULL);
1891 if (nprocs != 0 || daemonized_tracer)
1894 /* Do we want pids printed in our -o OUTFILE?
1895 * -ff: no (every pid has its own file); or
1896 * -f: yes (there can be more pids in the future); or
1897 * -p PID1,PID2: yes (there are already more than one pid)
1899 print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
1903 pid2tcb(const int pid)
1908 #define PID2TCB_CACHE_SIZE 1024U
1909 #define PID2TCB_CACHE_MASK (PID2TCB_CACHE_SIZE - 1)
1911 static struct tcb *pid2tcb_cache[PID2TCB_CACHE_SIZE];
1912 struct tcb **const ptcp = &pid2tcb_cache[pid & PID2TCB_CACHE_MASK];
1913 struct tcb *tcp = *ptcp;
1915 if (tcp && tcp->pid == pid)
1918 for (unsigned int i = 0; i < tcbtabsize; ++i) {
1920 if (tcp->pid == pid)
1934 /* 'interrupted' is a volatile object, fetch it only once */
1935 fatal_sig = interrupted;
1937 fatal_sig = SIGTERM;
1939 for (i = 0; i < tcbtabsize; i++) {
1943 debug_func_msg("looking at pid %u", tcp->pid);
1944 if (tcp->pid == strace_child) {
1945 kill(tcp->pid, SIGCONT);
1946 kill(tcp->pid, fatal_sig);
1951 call_summary(shared_log);
1961 print_debug_info(const int pid, int status)
1963 const unsigned int event = (unsigned int) status >> 16;
1964 char buf[sizeof("WIFEXITED,exitcode=%u") + sizeof(int)*3 /*paranoia:*/ + 16];
1965 char evbuf[sizeof(",EVENT_VFORK_DONE (%u)") + sizeof(int)*3 /*paranoia:*/ + 16];
1968 if (WIFSIGNALED(status))
1969 xsprintf(buf, "WIFSIGNALED,%ssig=%s",
1970 WCOREDUMP(status) ? "core," : "",
1971 sprintsigname(WTERMSIG(status)));
1972 if (WIFEXITED(status))
1973 xsprintf(buf, "WIFEXITED,exitcode=%u", WEXITSTATUS(status));
1974 if (WIFSTOPPED(status))
1975 xsprintf(buf, "WIFSTOPPED,sig=%s",
1976 sprintsigname(WSTOPSIG(status)));
1979 static const char *const event_names[] = {
1980 [PTRACE_EVENT_CLONE] = "CLONE",
1981 [PTRACE_EVENT_FORK] = "FORK",
1982 [PTRACE_EVENT_VFORK] = "VFORK",
1983 [PTRACE_EVENT_VFORK_DONE] = "VFORK_DONE",
1984 [PTRACE_EVENT_EXEC] = "EXEC",
1985 [PTRACE_EVENT_EXIT] = "EXIT",
1986 /* [PTRACE_EVENT_STOP (=128)] would make biggish array */
1988 const char *e = "??";
1989 if (event < ARRAY_SIZE(event_names))
1990 e = event_names[event];
1991 else if (event == PTRACE_EVENT_STOP)
1993 xsprintf(evbuf, ",EVENT_%s (%u)", e, event);
1995 error_msg("[wait(0x%06x) = %u] %s%s", status, pid, buf, evbuf);
1999 maybe_allocate_tcb(const int pid, int status)
2001 if (!WIFSTOPPED(status)) {
2002 if (detach_on_execve && pid == strace_child) {
2003 /* example: strace -bexecve sh -c 'exec true' */
2008 * This can happen if we inherited an unknown child.
2009 * Example: (sleep 1 & exec strace true)
2011 error_msg("Exit of unknown pid %u ignored", pid);
2015 /* We assume it's a fork/vfork/clone child */
2016 struct tcb *tcp = alloctcb(pid);
2017 after_successful_attach(tcp, post_attach_sigstop);
2019 error_msg("Process %d attached", pid);
2023 * This can happen if a clone call misused CLONE_PTRACE itself.
2025 * There used to be a dance around possible re-injection of
2026 * WSTOPSIG(status), but it was later removed as the only
2027 * observable stop here is the initial ptrace-stop.
2029 ptrace(PTRACE_DETACH, pid, NULL, 0L);
2030 error_msg("Detached unknown pid %d", pid);
2036 maybe_switch_tcbs(struct tcb *tcp, const int pid)
2039 struct tcb *execve_thread;
2042 if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, &old_pid) < 0)
2044 /* Avoid truncation in pid2tcb() param passing */
2045 if (old_pid <= 0 || old_pid == pid)
2047 if ((unsigned long) old_pid > UINT_MAX)
2049 execve_thread = pid2tcb(old_pid);
2050 /* It should be !NULL, but I feel paranoid */
2054 if (execve_thread->curcol != 0) {
2056 * One case we are here is -ff:
2057 * try "strace -oLOG -ff test/threaded_execve"
2059 fprintf(execve_thread->outf, " <pid changed to %d ...>\n", pid);
2060 /*execve_thread->curcol = 0; - no need, see code below */
2062 /* Swap output FILEs (needed for -ff) */
2063 fp = execve_thread->outf;
2064 execve_thread->outf = tcp->outf;
2066 /* And their column positions */
2067 execve_thread->curcol = tcp->curcol;
2069 /* Drop leader, but close execve'd thread outfile (if -ff) */
2071 /* Switch to the thread, reusing leader's outfile and pid */
2072 tcp = execve_thread;
2074 if (cflag != CFLAG_ONLY_STATS) {
2076 tprintf("+++ superseded by execve in pid %lu +++\n", old_pid);
2078 tcp->flags |= TCB_REPRINT;
2085 print_signalled(struct tcb *tcp, const int pid, int status)
2087 if (pid == strace_child) {
2088 exit_code = 0x100 | WTERMSIG(status);
2092 if (cflag != CFLAG_ONLY_STATS
2093 && is_number_in_set(WTERMSIG(status), signal_set)) {
2095 tprintf("+++ killed by %s %s+++\n",
2096 sprintsigname(WTERMSIG(status)),
2097 WCOREDUMP(status) ? "(core dumped) " : "");
2103 print_exited(struct tcb *tcp, const int pid, int status)
2105 if (pid == strace_child) {
2106 exit_code = WEXITSTATUS(status);
2110 if (cflag != CFLAG_ONLY_STATS &&
2113 tprintf("+++ exited with %d +++\n", WEXITSTATUS(status));
2119 print_stopped(struct tcb *tcp, const siginfo_t *si, const unsigned int sig)
2121 if (cflag != CFLAG_ONLY_STATS
2123 && is_number_in_set(sig, signal_set)) {
2126 tprintf("--- %s ", sprintsigname(sig));
2130 tprintf("--- stopped by %s ---\n", sprintsigname(sig));
2133 #ifdef ENABLE_STACKTRACE
2134 if (stack_trace_enabled)
2135 unwind_tcb_print(tcp);
2141 startup_tcb(struct tcb *tcp)
2143 debug_msg("pid %d has TCB_STARTUP, initializing it", tcp->pid);
2145 tcp->flags &= ~TCB_STARTUP;
2148 debug_msg("setting opts 0x%x on pid %d",
2149 ptrace_setoptions, tcp->pid);
2150 if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, ptrace_setoptions) < 0) {
2151 if (errno != ESRCH) {
2152 /* Should never happen, really */
2153 perror_msg_and_die("PTRACE_SETOPTIONS");
2158 if ((tcp->flags & TCB_GRABBED) && (get_scno(tcp) == 1))
2159 tcp->s_prev_ent = tcp->s_ent;
2163 print_event_exit(struct tcb *tcp)
2165 if (entering(tcp) || filtered(tcp) || hide_log(tcp)
2166 || cflag == CFLAG_ONLY_STATS) {
2170 if (followfork < 2 && printing_tcp && printing_tcp != tcp
2171 && printing_tcp->curcol != 0) {
2172 set_current_tcp(printing_tcp);
2173 tprints(" <unfinished ...>\n");
2174 flush_tcp_output(printing_tcp);
2175 printing_tcp->curcol = 0;
2176 set_current_tcp(tcp);
2179 print_syscall_resume(tcp);
2181 if (!(tcp->sys_func_rval & RVAL_DECODED)) {
2183 * The decoder has probably decided to print something
2184 * on exiting syscall which is not going to happen.
2186 tprints(" <unfinished ...>");
2196 static const struct tcb_wait_data *
2199 static struct tcb_wait_data wait_data;
2204 struct tcb_wait_data *wd = &wait_data;
2211 * Used to exit simply when nprocs hits zero, but in this testcase:
2212 * int main(void) { _exit(!!fork()); }
2213 * under strace -f, parent sometimes (rarely) manages
2214 * to exit before we see the first stop of the child,
2215 * and we are losing track of it:
2216 * 19923 clone(...) = 19924
2217 * 19923 exit_group(1) = ?
2218 * 19923 +++ exited with 1 +++
2219 * Exiting only when wait() returns ECHILD works better.
2221 if (popen_pid != 0) {
2222 /* However, if -o|logger is in use, we can't do that.
2223 * Can work around that by double-forking the logger,
2224 * but that loses the ability to wait for its completion
2225 * on exit. Oh well...
2231 const bool unblock_delay_timer = is_delay_timer_armed();
2234 * The window of opportunity to handle expirations
2235 * of the delay timer opens here.
2237 * Unblock the signal handler for the delay timer
2238 * iff the delay timer is already created.
2240 if (unblock_delay_timer)
2241 sigprocmask(SIG_UNBLOCK, &timer_set, NULL);
2244 * If the delay timer has expired, then its expiration
2245 * has been handled already by the signal handler.
2247 * If the delay timer expires during wait4(),
2248 * then the system call will be interrupted and
2249 * the expiration will be handled by the signal handler.
2251 pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
2252 const int wait_errno = errno;
2255 * The window of opportunity to handle expirations
2256 * of the delay timer closes here.
2258 * Block the signal handler for the delay timer
2259 * iff it was unblocked earlier.
2261 if (unblock_delay_timer) {
2262 sigprocmask(SIG_BLOCK, &timer_set, NULL);
2269 if (wait_errno == EINTR) {
2273 if (nprocs == 0 && wait_errno == ECHILD)
2276 * If nprocs > 0, ECHILD is not expected,
2277 * treat it as any other error here:
2280 perror_msg_and_die("wait4(__WALL)");
2283 wd->status = status;
2285 if (pid == popen_pid) {
2286 if (!WIFSTOPPED(status))
2293 print_debug_info(pid, status);
2295 /* Look up 'pid' in our table. */
2299 tcp = maybe_allocate_tcb(pid, status);
2308 /* Set current output file */
2309 set_current_tcp(tcp);
2312 struct timespec stime = {
2313 .tv_sec = ru.ru_stime.tv_sec,
2314 .tv_nsec = ru.ru_stime.tv_usec * 1000
2316 ts_sub(&tcp->dtime, &stime, &tcp->stime);
2320 if (WIFSIGNALED(status)) {
2321 wd->te = TE_SIGNALLED;
2325 if (WIFEXITED(status)) {
2331 * As WCONTINUED flag has not been specified to wait4,
2332 * it cannot be WIFCONTINUED(status), so the only case
2333 * that remains is WIFSTOPPED(status).
2336 /* Is this the very first time we see this tracee stopped? */
2337 if (tcp->flags & TCB_STARTUP)
2340 const unsigned int sig = WSTOPSIG(status);
2341 const unsigned int event = (unsigned int) status >> 16;
2346 * Is this post-attach SIGSTOP?
2347 * Interestingly, the process may stop
2348 * with STOPSIG equal to some other signal
2349 * than SIGSTOP if we happened to attach
2350 * just before the process takes a signal.
2352 if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
2353 debug_func_msg("ignored SIGSTOP on pid %d", tcp->pid);
2354 tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
2355 wd->te = TE_RESTART;
2356 } else if (sig == syscall_trap_sig) {
2357 wd->te = TE_SYSCALL_STOP;
2359 memset(&wd->si, 0, sizeof(wd->si));
2361 * True if tracee is stopped by signal
2362 * (as opposed to "tracee received signal").
2363 * TODO: shouldn't we check for errno == EINVAL too?
2364 * We can get ESRCH instead, you know...
2366 bool stopped = ptrace(PTRACE_GETSIGINFO, pid, 0, &wd->si) < 0;
2367 wd->te = stopped ? TE_GROUP_STOP : TE_SIGNAL_DELIVERY_STOP;
2370 case PTRACE_EVENT_STOP:
2372 * PTRACE_INTERRUPT-stop or group-stop.
2373 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
2380 wd->te = TE_GROUP_STOP;
2383 wd->te = TE_RESTART;
2386 case PTRACE_EVENT_EXEC:
2387 wd->te = TE_STOP_BEFORE_EXECVE;
2389 case PTRACE_EVENT_EXIT:
2390 wd->te = TE_STOP_BEFORE_EXIT;
2393 wd->te = TE_RESTART;
2400 trace_syscall(struct tcb *tcp, unsigned int *sig)
2402 if (entering(tcp)) {
2403 int res = syscall_entering_decode(tcp);
2408 res = syscall_entering_trace(tcp, sig);
2410 syscall_entering_finish(tcp, res);
2413 struct timespec ts = {};
2414 int res = syscall_exiting_decode(tcp, &ts);
2416 res = syscall_exiting_trace(tcp, &ts, res);
2418 syscall_exiting_finish(tcp);
2423 /* Returns true iff the main trace loop has to continue. */
2425 dispatch_event(const struct tcb_wait_data *wd)
2427 unsigned int restart_op = PTRACE_SYSCALL;
2428 unsigned int restart_sig = 0;
2429 enum trace_event te = wd ? wd->te : TE_BREAK;
2431 * Copy wd->status to a non-const variable to workaround glibc bugs
2432 * around union wait fixed by glibc commit glibc-2.24~391
2434 int status = wd ? wd->status : 0;
2446 case TE_SYSCALL_STOP:
2447 if (trace_syscall(current_tcp, &restart_sig) < 0) {
2449 * ptrace() failed in trace_syscall().
2450 * Likely a result of process disappearing mid-flight.
2451 * Observed case: exit_group() or SIGKILL terminating
2452 * all processes in thread group.
2453 * We assume that ptrace error was caused by process death.
2454 * We used to detach(current_tcp) here, but since we no
2455 * longer implement "detach before death" policy/hack,
2456 * we can let this process to report its death to us
2457 * normally, via WIFEXITED or WIFSIGNALED wait status.
2463 case TE_SIGNAL_DELIVERY_STOP:
2464 restart_sig = WSTOPSIG(status);
2465 print_stopped(current_tcp, &wd->si, restart_sig);
2469 print_signalled(current_tcp, current_tcp->pid, status);
2470 droptcb(current_tcp);
2474 restart_sig = WSTOPSIG(status);
2475 print_stopped(current_tcp, NULL, restart_sig);
2478 * This ends ptrace-stop, but does *not* end group-stop.
2479 * This makes stopping signals work properly on straced
2480 * process (that is, process really stops. It used to
2483 restart_op = PTRACE_LISTEN;
2489 print_exited(current_tcp, current_tcp->pid, status);
2490 droptcb(current_tcp);
2493 case TE_STOP_BEFORE_EXECVE:
2494 /* The syscall succeeded, clear the flag. */
2495 current_tcp->flags &= ~TCB_CHECK_EXEC_SYSCALL;
2497 * Check that we are inside syscall now (next event after
2498 * PTRACE_EVENT_EXEC should be for syscall exiting). If it is
2499 * not the case, we might have a situation when we attach to a
2500 * process and the first thing we see is a PTRACE_EVENT_EXEC
2501 * and all the following syscall state tracking is screwed up
2504 if (entering(current_tcp)) {
2507 error_msg("Stray PTRACE_EVENT_EXEC from pid %d"
2508 ", trying to recover...",
2511 current_tcp->flags |= TCB_RECOVERING;
2512 ret = trace_syscall(current_tcp, &restart_sig);
2513 current_tcp->flags &= ~TCB_RECOVERING;
2516 /* The reason is described in TE_SYSCALL_STOP */
2522 * Under Linux, execve changes pid to thread leader's pid,
2523 * and we see this changed pid on EVENT_EXEC and later,
2524 * execve sysexit. Leader "disappears" without exit
2525 * notification. Let user know that, drop leader's tcb,
2526 * and fix up pid in execve thread's tcb.
2527 * Effectively, execve thread's tcb replaces leader's tcb.
2529 * BTW, leader is 'stuck undead' (doesn't report WIFEXITED
2530 * on exit syscall) in multithreaded programs exactly
2531 * in order to handle this case.
2533 * PTRACE_GETEVENTMSG returns old pid starting from Linux 3.0.
2534 * On 2.6 and earlier, it can return garbage.
2536 if (os_release >= KERNEL_VERSION(3, 0, 0))
2537 set_current_tcp(maybe_switch_tcbs(current_tcp,
2540 if (detach_on_execve) {
2541 if (current_tcp->flags & TCB_SKIP_DETACH_ON_FIRST_EXEC) {
2542 current_tcp->flags &= ~TCB_SKIP_DETACH_ON_FIRST_EXEC;
2544 detach(current_tcp); /* do "-b execve" thingy */
2550 case TE_STOP_BEFORE_EXIT:
2551 print_event_exit(current_tcp);
2555 /* We handled quick cases, we are permitted to interrupt now. */
2559 /* If the process is being delayed, do not ptrace_restart just yet */
2560 if (syscall_delayed(current_tcp))
2563 if (ptrace_restart(restart_op, current_tcp, restart_sig) < 0) {
2564 /* Note: ptrace_restart emitted error message */
2572 restart_delayed_tcb(struct tcb *const tcp)
2574 const struct tcb_wait_data wd = { .te = TE_RESTART };
2576 debug_func_msg("pid %d", tcp->pid);
2578 tcp->flags &= ~TCB_DELAYED;
2580 struct tcb *const prev_tcp = current_tcp;
2582 bool ret = dispatch_event(&wd);
2583 current_tcp = prev_tcp;
2589 restart_delayed_tcbs(void)
2591 struct tcb *tcp_next = NULL;
2592 struct timespec ts_now;
2594 clock_gettime(CLOCK_MONOTONIC, &ts_now);
2596 for (size_t i = 0; i < tcbtabsize; i++) {
2597 struct tcb *tcp = tcbtab[i];
2599 if (tcp->pid && syscall_delayed(tcp)) {
2600 if (ts_cmp(&ts_now, &tcp->delay_expiration_time) > 0) {
2601 if (!restart_delayed_tcb(tcp))
2604 /* Check whether this tcb is the next. */
2606 ts_cmp(&tcp_next->delay_expiration_time,
2607 &tcp->delay_expiration_time) > 0) {
2615 arm_delay_timer(tcp_next);
2621 * As this signal handler does a lot of work that is not suitable
2622 * for signal handlers, extra care must be taken to ensure that
2623 * it is enabled only in those places where it's safe.
2626 timer_sighandler(int sig)
2628 delay_timer_expired();
2633 int saved_errno = errno;
2635 if (!restart_delayed_tcbs())
2638 errno = saved_errno;
2641 #ifdef ENABLE_COVERAGE_GCOV
2642 extern void __gcov_flush(void);
2645 static void ATTRIBUTE_NORETURN
2650 if (shared_log != stderr)
2653 while (waitpid(popen_pid, NULL, 0) < 0 && errno == EINTR)
2657 exit_code = 0x100 | interrupted;
2659 if (exit_code > 0xff) {
2660 /* Avoid potential core file clobbering. */
2661 struct_rlimit rlim = {0, 0};
2662 set_rlimit(RLIMIT_CORE, &rlim);
2664 /* Child was killed by a signal, mimic that. */
2666 signal(exit_code, SIG_DFL);
2667 #ifdef ENABLE_COVERAGE_GCOV
2672 /* Unblock the signal. */
2675 sigaddset(&mask, exit_code);
2676 #ifdef ENABLE_COVERAGE_GCOV
2679 sigprocmask(SIG_UNBLOCK, &mask, NULL);
2681 /* Paranoia - what if this signal is not fatal?
2682 Exit with 128 + signo then. */
2689 main(int argc, char *argv[])
2691 setlocale(LC_ALL, "");
2694 exit_code = !nprocs;
2696 while (dispatch_event(next_event()))