/*
* Copyright (c) 1991, 1992 Paul Kranenburg <pk@cs.few.eur.nl>
* Copyright (c) 1993 Branko Lankester <branko@hacktic.nl>
* Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <jrs@world.std.com>
* Copyright (c) 1996-1999 Wichert Akkerman <wichert@cistron.nl>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "defs.h"
#include <stdarg.h>
#include <sys/param.h>
#include <fcntl.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <pwd.h>
#include <grp.h>
#include <dirent.h>
#include <sys/utsname.h>
#ifdef HAVE_PRCTL
# include <sys/prctl.h>
#endif
#include "ptrace.h"
/* In some libc, these aren't declared. Do it ourself: */
extern char **environ;
extern int optind;
extern char *optarg;
#ifdef USE_LIBUNWIND
/* if this is true do the stack trace for every system call */
bool stack_trace_enabled = false;
#endif
#if defined __NR_tkill
# define my_tkill(tid, sig) syscall(__NR_tkill, (tid), (sig))
#else
/* kill() may choose arbitrarily the target task of the process group
while we later wait on a that specific TID. PID process waits become
TID task specific waits for a process under ptrace(2). */
# warning "tkill(2) not available, risk of strace hangs!"
# define my_tkill(tid, sig) kill((tid), (sig))
#endif
/* Glue for systems without a MMU that cannot provide fork() */
#if !defined(HAVE_FORK)
# undef NOMMU_SYSTEM
# define NOMMU_SYSTEM 1
#endif
#if NOMMU_SYSTEM
# define fork() vfork()
#endif
const unsigned int syscall_trap_sig = SIGTRAP | 0x80;
cflag_t cflag = CFLAG_NONE;
unsigned int followfork = 0;
unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC;
unsigned int xflag = 0;
bool debug_flag = 0;
bool Tflag = 0;
bool iflag = 0;
bool count_wallclock = 0;
unsigned int qflag = 0;
static unsigned int tflag = 0;
static bool rflag = 0;
static bool print_pid_pfx = 0;
/* -I n */
enum {
INTR_NOT_SET = 0,
INTR_ANYWHERE = 1, /* don't block/ignore any signals */
INTR_WHILE_WAIT = 2, /* block fatal signals while decoding syscall. default */
INTR_NEVER = 3, /* block fatal signals. default if '-o FILE PROG' */
INTR_BLOCK_TSTP_TOO = 4, /* block fatal signals and SIGTSTP (^Z) */
NUM_INTR_OPTS
};
static int opt_intr;
/* We play with signal mask only if this mode is active: */
#define interactive (opt_intr == INTR_WHILE_WAIT)
/*
* daemonized_tracer supports -D option.
* With this option, strace forks twice.
* Unlike normal case, with -D *grandparent* process exec's,
* becoming a traced process. Child exits (this prevents traced process
* from having children it doesn't expect to have), and grandchild
* attaches to grandparent similarly to strace -p PID.
* This allows for more transparent interaction in cases
* when process and its parent are communicating via signals,
* wait() etc. Without -D, strace process gets lodged in between,
* disrupting parent<->child link.
*/
static bool daemonized_tracer = 0;
#if USE_SEIZE
static int post_attach_sigstop = TCB_IGNORE_ONE_SIGSTOP;
# define use_seize (post_attach_sigstop == 0)
#else
# define post_attach_sigstop TCB_IGNORE_ONE_SIGSTOP
# define use_seize 0
#endif
/* Sometimes we want to print only succeeding syscalls. */
bool not_failing_only = 0;
/* Show path associated with fd arguments */
unsigned int show_fd_path = 0;
static bool detach_on_execve = 0;
/* Are we "strace PROG" and need to skip detach on first execve? */
static bool skip_one_b_execve = 0;
/* Are we "strace PROG" and need to hide everything until execve? */
bool hide_log_until_execve = 0;
static int exit_code = 0;
static int strace_child = 0;
static int strace_tracer_pid = 0;
static char *username = NULL;
static uid_t run_uid;
static gid_t run_gid;
unsigned int max_strlen = DEFAULT_STRLEN;
static int acolumn = DEFAULT_ACOLUMN;
static char *acolumn_spaces;
static char *outfname = NULL;
/* If -ff, points to stderr. Else, it's our common output log */
static FILE *shared_log;
struct tcb *printing_tcp = NULL;
static struct tcb *current_tcp;
static struct tcb **tcbtab;
static unsigned int nprocs, tcbtabsize;
static const char *progname;
unsigned os_release; /* generated from uname()'s u.release */
static void detach(struct tcb *tcp);
static void cleanup(void);
static void interrupt(int sig);
static sigset_t empty_set, blocked_set;
#ifdef HAVE_SIG_ATOMIC_T
static volatile sig_atomic_t interrupted;
#else
static volatile int interrupted;
#endif
#ifndef HAVE_STRERROR
#if !HAVE_DECL_SYS_ERRLIST
extern int sys_nerr;
extern char *sys_errlist[];
#endif
const char *
strerror(int err_no)
{
static char buf[sizeof("Unknown error %d") + sizeof(int)*3];
if (err_no < 1 || err_no >= sys_nerr) {
sprintf(buf, "Unknown error %d", err_no);
return buf;
}
return sys_errlist[err_no];
}
#endif /* HAVE_STERRROR */
static void
usage(FILE *ofp, int exitval)
{
fprintf(ofp, "\
usage: strace [-CdffhiqrtttTvVxxy] [-I n] [-e expr]...\n\
[-a column] [-o file] [-s strsize] [-P path]...\n\
-p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
or: strace -c[df] [-I n] [-e expr]... [-O overhead] [-S sortby]\n\
-p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]\n\
-c -- count time, calls, and errors for each syscall and report summary\n\
-C -- like -c but also print regular output\n\
-w -- summarise syscall latency (default is system time)\n\
-d -- enable debug output to stderr\n\
-D -- run tracer process as a detached grandchild, not as parent\n\
-f -- follow forks, -ff -- with output into separate files\n\
-i -- print instruction pointer at time of syscall\n\
-q -- suppress messages about attaching, detaching, etc.\n\
-r -- print relative timestamp, -t -- absolute timestamp, -tt -- with usecs\n\
-T -- print time spent in each syscall\n\
-v -- verbose mode: print unabbreviated argv, stat, termios, etc. args\n\
-x -- print non-ascii strings in hex, -xx -- print all strings in hex\n\
-y -- print paths associated with file descriptor arguments\n\
-yy -- print ip:port pairs associated with socket file descriptors\n\
-h -- print help message, -V -- print version\n\
-a column -- alignment COLUMN for printing syscall results (default %d)\n\
-b execve -- detach on this syscall\n\
-e expr -- a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
options: trace, abbrev, verbose, raw, signal, read, write\n\
-I interruptible --\n\
1: no signals are blocked\n\
2: fatal signals are blocked while decoding syscall (default)\n\
3: fatal signals are always blocked (default if '-o FILE PROG')\n\
4: fatal signals and SIGTSTP (^Z) are always blocked\n\
(useful to make 'strace -o FILE PROG' not stop on ^Z)\n\
-o file -- send trace output to FILE instead of stderr\n\
-O overhead -- set overhead for tracing syscalls to OVERHEAD usecs\n\
-p pid -- trace process with process id PID, may be repeated\n\
-s strsize -- limit length of print strings to STRSIZE chars (default %d)\n\
-S sortby -- sort syscall counts by: time, calls, name, nothing (default %s)\n\
-u username -- run command as username handling setuid and/or setgid\n\
-E var=val -- put var=val in the environment for command\n\
-E var -- remove var from the environment for command\n\
-P path -- trace accesses to path\n\
"
#ifdef USE_LIBUNWIND
"-k obtain stack trace between each syscall (experimental)\n\
"
#endif
/* ancient, no one should use it
-F -- attempt to follow vforks (deprecated, use -f)\n\
*/
/* this is broken, so don't document it
-z -- print only succeeding syscalls\n\
*/
, DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
exit(exitval);
}
static void ATTRIBUTE_NORETURN
die(void)
{
if (strace_tracer_pid == getpid()) {
cflag = 0;
cleanup();
}
exit(1);
}
static void verror_msg(int err_no, const char *fmt, va_list p)
{
char *msg;
fflush(NULL);
/* We want to print entire message with single fprintf to ensure
* message integrity if stderr is shared with other programs.
* Thus we use vasprintf + single fprintf.
*/
msg = NULL;
if (vasprintf(&msg, fmt, p) >= 0) {
if (err_no)
fprintf(stderr, "%s: %s: %s\n", progname, msg, strerror(err_no));
else
fprintf(stderr, "%s: %s\n", progname, msg);
free(msg);
} else {
/* malloc in vasprintf failed, try it without malloc */
fprintf(stderr, "%s: ", progname);
vfprintf(stderr, fmt, p);
if (err_no)
fprintf(stderr, ": %s\n", strerror(err_no));
else
putc('\n', stderr);
}
/* We don't switch stderr to buffered, thus fprintf(stderr)
* always flushes its output and this is not necessary: */
/* fflush(stderr); */
}
void error_msg(const char *fmt, ...)
{
va_list p;
va_start(p, fmt);
verror_msg(0, fmt, p);
va_end(p);
}
void error_msg_and_die(const char *fmt, ...)
{
va_list p;
va_start(p, fmt);
verror_msg(0, fmt, p);
die();
}
void perror_msg(const char *fmt, ...)
{
va_list p;
va_start(p, fmt);
verror_msg(errno, fmt, p);
va_end(p);
}
void perror_msg_and_die(const char *fmt, ...)
{
va_list p;
va_start(p, fmt);
verror_msg(errno, fmt, p);
die();
}
void die_out_of_memory(void)
{
static bool recursed = 0;
if (recursed)
exit(1);
recursed = 1;
error_msg_and_die("Out of memory");
}
static void
error_opt_arg(int opt, const char *arg)
{
error_msg_and_die("Invalid -%c argument: '%s'", opt, arg);
}
#if USE_SEIZE
static int
ptrace_attach_or_seize(int pid)
{
int r;
if (!use_seize)
return ptrace(PTRACE_ATTACH, pid, 0L, 0L);
r = ptrace(PTRACE_SEIZE, pid, 0L, (unsigned long) ptrace_setoptions);
if (r)
return r;
r = ptrace(PTRACE_INTERRUPT, pid, 0L, 0L);
return r;
}
#else
# define ptrace_attach_or_seize(pid) ptrace(PTRACE_ATTACH, (pid), 0, 0)
#endif
/*
* Used when we want to unblock stopped traced process.
* Should be only used with PTRACE_CONT, PTRACE_DETACH and PTRACE_SYSCALL.
* Returns 0 on success or if error was ESRCH
* (presumably process was killed while we talk to it).
* Otherwise prints error message and returns -1.
*/
static int
ptrace_restart(int op, struct tcb *tcp, int sig)
{
int err;
const char *msg;
errno = 0;
ptrace(op, tcp->pid, (void *) 0, (long) sig);
err = errno;
if (!err)
return 0;
msg = "SYSCALL";
if (op == PTRACE_CONT)
msg = "CONT";
if (op == PTRACE_DETACH)
msg = "DETACH";
#ifdef PTRACE_LISTEN
if (op == PTRACE_LISTEN)
msg = "LISTEN";
#endif
/*
* Why curcol != 0? Otherwise sometimes we get this:
*
* 10252 kill(10253, SIGKILL) = 0
* <ptrace(SYSCALL,10252):No such process>10253 ...next decode...
*
* 10252 died after we retrieved syscall exit data,
* but before we tried to restart it. Log looks ugly.
*/
if (current_tcp && current_tcp->curcol != 0) {
tprintf(" <ptrace(%s):%s>\n", msg, strerror(err));
line_ended();
}
if (err == ESRCH)
return 0;
errno = err;
perror_msg("ptrace(PTRACE_%s,pid:%d,sig:%d)", msg, tcp->pid, sig);
return -1;
}
static void
set_cloexec_flag(int fd)
{
int flags, newflags;
flags = fcntl(fd, F_GETFD);
if (flags < 0) {
/* Can happen only if fd is bad.
* Should never happen: if it does, we have a bug
* in the caller. Therefore we just abort
* instead of propagating the error.
*/
perror_msg_and_die("fcntl(%d, F_GETFD)", fd);
}
newflags = flags | FD_CLOEXEC;
if (flags == newflags)
return;
fcntl(fd, F_SETFD, newflags); /* never fails */
}
static void kill_save_errno(pid_t pid, int sig)
{
int saved_errno = errno;
(void) kill(pid, sig);
errno = saved_errno;
}
/*
* When strace is setuid executable, we have to swap uids
* before and after filesystem and process management operations.
*/
static void
swap_uid(void)
{
int euid = geteuid(), uid = getuid();
if (euid != uid && setreuid(euid, uid) < 0) {
perror_msg_and_die("setreuid");
}
}
#ifdef _LARGEFILE64_SOURCE
# ifdef HAVE_FOPEN64
# define fopen_for_output fopen64
# else
# define fopen_for_output fopen
# endif
# define struct_stat struct stat64
# define stat_file stat64
# define struct_dirent struct dirent64
# define read_dir readdir64
# define struct_rlimit struct rlimit64
# define set_rlimit setrlimit64
#else
# define fopen_for_output fopen
# define struct_stat struct stat
# define stat_file stat
# define struct_dirent struct dirent
# define read_dir readdir
# define struct_rlimit struct rlimit
# define set_rlimit setrlimit
#endif
static FILE *
strace_fopen(const char *path)
{
FILE *fp;
swap_uid();
fp = fopen_for_output(path, "w");
if (!fp)
perror_msg_and_die("Can't fopen '%s'", path);
swap_uid();
set_cloexec_flag(fileno(fp));
return fp;
}
static int popen_pid = 0;
#ifndef _PATH_BSHELL
# define _PATH_BSHELL "/bin/sh"
#endif
/*
* We cannot use standard popen(3) here because we have to distinguish
* popen child process from other processes we trace, and standard popen(3)
* does not export its child's pid.
*/
static FILE *
strace_popen(const char *command)
{
FILE *fp;
int pid;
int fds[2];
swap_uid();
if (pipe(fds) < 0)
perror_msg_and_die("pipe");
set_cloexec_flag(fds[1]); /* never fails */
pid = vfork();
if (pid < 0)
perror_msg_and_die("vfork");
if (pid == 0) {
/* child */
close(fds[1]);
if (fds[0] != 0) {
if (dup2(fds[0], 0))
perror_msg_and_die("dup2");
close(fds[0]);
}
execl(_PATH_BSHELL, "sh", "-c", command, NULL);
perror_msg_and_die("Can't execute '%s'", _PATH_BSHELL);
}
/* parent */
popen_pid = pid;
close(fds[0]);
swap_uid();
fp = fdopen(fds[1], "w");
if (!fp)
die_out_of_memory();
return fp;
}
void
tprintf(const char *fmt, ...)
{
va_list args;
va_start(args, fmt);
if (current_tcp) {
int n = strace_vfprintf(current_tcp->outf, fmt, args);
if (n < 0) {
if (current_tcp->outf != stderr)
perror_msg("%s", outfname);
} else
current_tcp->curcol += n;
}
va_end(args);
}
#ifndef HAVE_FPUTS_UNLOCKED
# define fputs_unlocked fputs
#endif
void
tprints(const char *str)
{
if (current_tcp) {
int n = fputs_unlocked(str, current_tcp->outf);
if (n >= 0) {
current_tcp->curcol += strlen(str);
return;
}
if (current_tcp->outf != stderr)
perror_msg("%s", outfname);
}
}
void
line_ended(void)
{
if (current_tcp) {
current_tcp->curcol = 0;
fflush(current_tcp->outf);
}
if (printing_tcp) {
printing_tcp->curcol = 0;
printing_tcp = NULL;
}
}
void
printleader(struct tcb *tcp)
{
/* If -ff, "previous tcb we printed" is always the same as current,
* because we have per-tcb output files.
*/
if (followfork >= 2)
printing_tcp = tcp;
if (printing_tcp) {
current_tcp = printing_tcp;
if (printing_tcp->curcol != 0 && (followfork < 2 || printing_tcp == tcp)) {
/*
* case 1: we have a shared log (i.e. not -ff), and last line
* wasn't finished (same or different tcb, doesn't matter).
* case 2: split log, we are the same tcb, but our last line
* didn't finish ("SIGKILL nuked us after syscall entry" etc).
*/
tprints(" <unfinished ...>\n");
printing_tcp->curcol = 0;
}
}
printing_tcp = tcp;
current_tcp = tcp;
current_tcp->curcol = 0;
if (print_pid_pfx)
tprintf("%-5d ", tcp->pid);
else if (nprocs > 1 && !outfname)
tprintf("[pid %5u] ", tcp->pid);
if (tflag) {
char str[sizeof("HH:MM:SS")];
struct timeval tv, dtv;
static struct timeval otv;
gettimeofday(&tv, NULL);
if (rflag) {
if (otv.tv_sec == 0)
otv = tv;
tv_sub(&dtv, &tv, &otv);
tprintf("%6ld.%06ld ",
(long) dtv.tv_sec, (long) dtv.tv_usec);
otv = tv;
}
else if (tflag > 2) {
tprintf("%ld.%06ld ",
(long) tv.tv_sec, (long) tv.tv_usec);
}
else {
time_t local = tv.tv_sec;
strftime(str, sizeof(str), "%T", localtime(&local));
if (tflag > 1)
tprintf("%s.%06ld ", str, (long) tv.tv_usec);
else
tprintf("%s ", str);
}
}
if (iflag)
print_pc(tcp);
}
void
tabto(void)
{
if (current_tcp->curcol < acolumn)
tprints(acolumn_spaces + current_tcp->curcol);
}
/* Should be only called directly *after successful attach* to a tracee.
* Otherwise, "strace -oFILE -ff -p<nonexistant_pid>"
* may create bogus empty FILE.<nonexistant_pid>, and then die.
*/
static void
newoutf(struct tcb *tcp)
{
tcp->outf = shared_log; /* if not -ff mode, the same file is for all */
if (followfork >= 2) {
char name[520 + sizeof(int) * 3];
sprintf(name, "%.512s.%u", outfname, tcp->pid);
tcp->outf = strace_fopen(name);
}
}
static void
expand_tcbtab(void)
{
/* Allocate some more TCBs and expand the table.
We don't want to relocate the TCBs because our
callers have pointers and it would be a pain.
So tcbtab is a table of pointers. Since we never
free the TCBs, we allocate a single chunk of many. */
unsigned int i = tcbtabsize;
struct tcb *newtcbs = calloc(tcbtabsize, sizeof(newtcbs[0]));
struct tcb **newtab = realloc(tcbtab, tcbtabsize * 2 * sizeof(tcbtab[0]));
if (!newtab || !newtcbs)
die_out_of_memory();
tcbtabsize *= 2;
tcbtab = newtab;
while (i < tcbtabsize)
tcbtab[i++] = newtcbs++;
}
static struct tcb *
alloctcb(int pid)
{
unsigned int i;
struct tcb *tcp;
if (nprocs == tcbtabsize)
expand_tcbtab();
for (i = 0; i < tcbtabsize; i++) {
tcp = tcbtab[i];
if (!tcp->pid) {
memset(tcp, 0, sizeof(*tcp));
tcp->pid = pid;
#if SUPPORTED_PERSONALITIES > 1
tcp->currpers = current_personality;
#endif
#ifdef USE_LIBUNWIND
if (stack_trace_enabled)
unwind_tcb_init(tcp);
#endif
nprocs++;
if (debug_flag)
fprintf(stderr, "new tcb for pid %d, active tcbs:%d\n", tcp->pid, nprocs);
return tcp;
}
}
error_msg_and_die("bug in alloctcb");
}
static void
droptcb(struct tcb *tcp)
{
if (tcp->pid == 0)
return;
#ifdef USE_LIBUNWIND
if (stack_trace_enabled) {
unwind_tcb_fin(tcp);
}
#endif
nprocs--;
if (debug_flag)
fprintf(stderr, "dropped tcb for pid %d, %d remain\n", tcp->pid, nprocs);
if (tcp->outf) {
if (followfork >= 2) {
if (tcp->curcol != 0)
fprintf(tcp->outf, " <detached ...>\n");
fclose(tcp->outf);
} else {
if (printing_tcp == tcp && tcp->curcol != 0)
fprintf(tcp->outf, " <detached ...>\n");
fflush(tcp->outf);
}
}
if (current_tcp == tcp)
current_tcp = NULL;
if (printing_tcp == tcp)
printing_tcp = NULL;
memset(tcp, 0, sizeof(*tcp));
}
/* Detach traced process.
* Never call DETACH twice on the same process as both unattached and
* attached-unstopped processes give the same ESRCH. For unattached process we
* would SIGSTOP it and wait for its SIGSTOP notification forever.
*/
static void
detach(struct tcb *tcp)
{
int error;
int status;
/*
* Linux wrongly insists the child be stopped
* before detaching. Arghh. We go through hoops
* to make a clean break of things.
*/
#if defined(SPARC)
# undef PTRACE_DETACH
# define PTRACE_DETACH PTRACE_SUNDETACH
#endif
if (!(tcp->flags & TCB_ATTACHED))
goto drop;
/* We attached but possibly didn't see the expected SIGSTOP.
* We must catch exactly one as otherwise the detached process
* would be left stopped (process state T).
*/
if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
goto wait_loop;
error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
if (!error) {
/* On a clear day, you can see forever. */
goto drop;
}
if (errno != ESRCH) {
/* Shouldn't happen. */
perror_msg("detach: ptrace(PTRACE_DETACH,%u)", tcp->pid);
goto drop;
}
/* ESRCH: process is either not stopped or doesn't exist. */
if (my_tkill(tcp->pid, 0) < 0) {
if (errno != ESRCH)
/* Shouldn't happen. */
perror_msg("detach: tkill(%u,0)", tcp->pid);
/* else: process doesn't exist. */
goto drop;
}
/* Process is not stopped, need to stop it. */
if (use_seize) {
/*
* With SEIZE, tracee can be in group-stop already.
* In this state sending it another SIGSTOP does nothing.
* Need to use INTERRUPT.
* Testcase: trying to ^C a "strace -p <stopped_process>".
*/
error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
if (!error)
goto wait_loop;
if (errno != ESRCH)
perror_msg("detach: ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
}
else {
error = my_tkill(tcp->pid, SIGSTOP);
if (!error)
goto wait_loop;
if (errno != ESRCH)
perror_msg("detach: tkill(%u,SIGSTOP)", tcp->pid);
}
/* Either process doesn't exist, or some weird error. */
goto drop;
wait_loop:
/* We end up here in three cases:
* 1. We sent PTRACE_INTERRUPT (use_seize case)
* 2. We sent SIGSTOP (!use_seize)
* 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
*/
for (;;) {
unsigned int sig;
if (waitpid(tcp->pid, &status, __WALL) < 0) {
if (errno == EINTR)
continue;
/*
* if (errno == ECHILD) break;
* ^^^ WRONG! We expect this PID to exist,
* and want to emit a message otherwise:
*/
perror_msg("detach: waitpid(%u)", tcp->pid);
break;
}
if (!WIFSTOPPED(status)) {
/*
* Tracee exited or was killed by signal.
* We shouldn't normally reach this place:
* we don't want to consume exit status.
* Consider "strace -p PID" being ^C-ed:
* we want merely to detach from PID.
*
* However, we _can_ end up here if tracee
* was SIGKILLed.
*/
break;
}
sig = WSTOPSIG(status);
if (debug_flag)
fprintf(stderr, "detach wait: event:%d sig:%d\n",
(unsigned)status >> 16, sig);
if (use_seize) {
unsigned event = (unsigned)status >> 16;
if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
/*
* sig == SIGTRAP: PTRACE_INTERRUPT stop.
* sig == other: process was already stopped
* with this stopping sig (see tests/detach-stopped).
* Looks like re-injecting this sig is not necessary
* in DETACH for the tracee to remain stopped.
*/
sig = 0;
}
/*
* PTRACE_INTERRUPT is not guaranteed to produce
* the above event if other ptrace-stop is pending.
* See tests/detach-sleeping testcase:
* strace got SIGINT while tracee is sleeping.
* We sent PTRACE_INTERRUPT.
* We see syscall exit, not PTRACE_INTERRUPT stop.
* We won't get PTRACE_INTERRUPT stop
* if we would CONT now. Need to DETACH.
*/
if (sig == syscall_trap_sig)
sig = 0;
/* else: not sure in which case we can be here.
* Signal stop? Inject it while detaching.
*/
ptrace_restart(PTRACE_DETACH, tcp, sig);
break;
}
/* Note: this check has to be after use_seize check */
/* (else, in use_seize case SIGSTOP will be mistreated) */
if (sig == SIGSTOP) {
/* Detach, suppressing SIGSTOP */
ptrace_restart(PTRACE_DETACH, tcp, 0);
break;
}
if (sig == syscall_trap_sig)
sig = 0;
/* Can't detach just yet, may need to wait for SIGSTOP */
error = ptrace_restart(PTRACE_CONT, tcp, sig);
if (error < 0) {
/* Should not happen.
* Note: ptrace_restart returns 0 on ESRCH, so it's not it.
* ptrace_restart already emitted error message.
*/
break;
}
}
drop:
if (!qflag && (tcp->flags & TCB_ATTACHED))
fprintf(stderr, "Process %u detached\n", tcp->pid);
droptcb(tcp);
}
static void
process_opt_p_list(char *opt)
{
while (*opt) {
/*
* We accept -p PID,PID; -p "`pidof PROG`"; -p "`pgrep PROG`".
* pidof uses space as delim, pgrep uses newline. :(
*/
int pid;
char *delim = opt + strcspn(opt, ", \n\t");
char c = *delim;
*delim = '\0';
pid = string_to_uint(opt);
if (pid <= 0) {
error_msg_and_die("Invalid process id: '%s'", opt);
}
if (pid == strace_tracer_pid) {
error_msg_and_die("I'm sorry, I can't let you do that, Dave.");
}
*delim = c;
alloctcb(pid);
if (c == '\0')
break;
opt = delim + 1;
}
}
static void
startup_attach(void)
{
unsigned int tcbi;
struct tcb *tcp;
/*
* Block user interruptions as we would leave the traced
* process stopped (process state T) if we would terminate in
* between PTRACE_ATTACH and wait4() on SIGSTOP.
* We rely on cleanup() from this point on.
*/
if (interactive)
sigprocmask(SIG_BLOCK, &blocked_set, NULL);
if (daemonized_tracer) {
pid_t pid = fork();
if (pid < 0) {
perror_msg_and_die("fork");
}
if (pid) { /* parent */
/*
* Wait for grandchild to attach to straced process
* (grandparent). Grandchild SIGKILLs us after it attached.
* Grandparent's wait() is unblocked by our death,
* it proceeds to exec the straced program.
*/
pause();
_exit(0); /* paranoia */
}
/* grandchild */
/* We will be the tracer process. Remember our new pid: */
strace_tracer_pid = getpid();
}
for (tcbi = 0; tcbi < tcbtabsize; tcbi++) {
tcp = tcbtab[tcbi];
if (!tcp->pid)
continue;
/* Is this a process we should attach to, but not yet attached? */
if (tcp->flags & TCB_ATTACHED)
continue; /* no, we already attached it */
if (followfork && !daemonized_tracer) {
char procdir[sizeof("/proc/%d/task") + sizeof(int) * 3];
DIR *dir;
sprintf(procdir, "/proc/%d/task", tcp->pid);
dir = opendir(procdir);
if (dir != NULL) {
unsigned int ntid = 0, nerr = 0;
struct_dirent *de;
while ((de = read_dir(dir)) != NULL) {
struct tcb *cur_tcp;
int tid;
if (de->d_fileno == 0)
continue;
/* we trust /proc filesystem */
tid = atoi(de->d_name);
if (tid <= 0)
continue;
++ntid;
if (ptrace_attach_or_seize(tid) < 0) {
++nerr;
if (debug_flag)
fprintf(stderr, "attach to pid %d failed\n", tid);
continue;
}
if (debug_flag)
fprintf(stderr, "attach to pid %d succeeded\n", tid);
cur_tcp = tcp;
if (tid != tcp->pid)
cur_tcp = alloctcb(tid);
cur_tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
newoutf(cur_tcp);
}
closedir(dir);
if (interactive) {
sigprocmask(SIG_SETMASK, &empty_set, NULL);
if (interrupted)
goto ret;
sigprocmask(SIG_BLOCK, &blocked_set, NULL);
}
ntid -= nerr;
if (ntid == 0) {
perror_msg("attach: ptrace(PTRACE_ATTACH, ...)");
droptcb(tcp);
continue;
}
if (!qflag) {
fprintf(stderr, ntid > 1
? "Process %u attached with %u threads\n"
: "Process %u attached\n",
tcp->pid, ntid);
}
if (!(tcp->flags & TCB_ATTACHED)) {
/* -p PID, we failed to attach to PID itself
* but did attach to some of its sibling threads.
* Drop PID's tcp.
*/
droptcb(tcp);
}
continue;
} /* if (opendir worked) */
} /* if (-f) */
if (ptrace_attach_or_seize(tcp->pid) < 0) {
perror_msg("attach: ptrace(PTRACE_ATTACH, ...)");
droptcb(tcp);
continue;
}
tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
newoutf(tcp);
if (debug_flag)
fprintf(stderr, "attach to pid %d (main) succeeded\n", tcp->pid);
if (daemonized_tracer) {
/*
* Make parent go away.
* Also makes grandparent's wait() unblock.
*/
kill(getppid(), SIGKILL);
}
if (!qflag)
fprintf(stderr,
"Process %u attached\n",
tcp->pid);
} /* for each tcbtab[] */
ret:
if (interactive)
sigprocmask(SIG_SETMASK, &empty_set, NULL);
}
/* Stack-o-phobic exec helper, in the hope to work around
* NOMMU + "daemonized tracer" difficulty.
*/
struct exec_params {
int fd_to_close;
uid_t run_euid;
gid_t run_egid;
char **argv;
char *pathname;
};
static struct exec_params params_for_tracee;
static void ATTRIBUTE_NOINLINE ATTRIBUTE_NORETURN
exec_or_die(void)
{
struct exec_params *params = ¶ms_for_tracee;
if (params->fd_to_close >= 0)
close(params->fd_to_close);
if (!daemonized_tracer && !use_seize) {
if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0) {
perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
}
}
if (username != NULL) {
/*
* It is important to set groups before we
* lose privileges on setuid.
*/
if (initgroups(username, run_gid) < 0) {
perror_msg_and_die("initgroups");
}
if (setregid(run_gid, params->run_egid) < 0) {
perror_msg_and_die("setregid");
}
if (setreuid(run_uid, params->run_euid) < 0) {
perror_msg_and_die("setreuid");
}
}
else if (geteuid() != 0)
if (setreuid(run_uid, run_uid) < 0) {
perror_msg_and_die("setreuid");
}
if (!daemonized_tracer) {
/*
* Induce a ptrace stop. Tracer (our parent)
* will resume us with PTRACE_SYSCALL and display
* the immediately following execve syscall.
* Can't do this on NOMMU systems, we are after
* vfork: parent is blocked, stopping would deadlock.
*/
if (!NOMMU_SYSTEM)
kill(getpid(), SIGSTOP);
} else {
alarm(3);
/* we depend on SIGCHLD set to SIG_DFL by init code */
/* if it happens to be SIG_IGN'ed, wait won't block */
wait(NULL);
alarm(0);
}
execv(params->pathname, params->argv);
perror_msg_and_die("exec");
}
static void
startup_child(char **argv)
{
struct_stat statbuf;
const char *filename;
size_t filename_len;
char pathname[PATH_MAX];
int pid;
struct tcb *tcp;
filename = argv[0];
filename_len = strlen(filename);
if (filename_len > sizeof(pathname) - 1) {
errno = ENAMETOOLONG;
perror_msg_and_die("exec");
}
if (strchr(filename, '/')) {
strcpy(pathname, filename);
}
#ifdef USE_DEBUGGING_EXEC
/*
* Debuggers customarily check the current directory
* first regardless of the path but doing that gives
* security geeks a panic attack.
*/
else if (stat_file(filename, &statbuf) == 0)
strcpy(pathname, filename);
#endif /* USE_DEBUGGING_EXEC */
else {
const char *path;
size_t m, n, len;
for (path = getenv("PATH"); path && *path; path += m) {
const char *colon = strchr(path, ':');
if (colon) {
n = colon - path;
m = n + 1;
}
else
m = n = strlen(path);
if (n == 0) {
if (!getcwd(pathname, PATH_MAX))
continue;
len = strlen(pathname);
}
else if (n > sizeof pathname - 1)
continue;
else {
strncpy(pathname, path, n);
len = n;
}
if (len && pathname[len - 1] != '/')
pathname[len++] = '/';
if (filename_len + len > sizeof(pathname) - 1)
continue;
strcpy(pathname + len, filename);
if (stat_file(pathname, &statbuf) == 0 &&
/* Accept only regular files
with some execute bits set.
XXX not perfect, might still fail */
S_ISREG(statbuf.st_mode) &&
(statbuf.st_mode & 0111))
break;
}
if (!path || !*path)
pathname[0] = '\0';
}
if (stat_file(pathname, &statbuf) < 0) {
perror_msg_and_die("Can't stat '%s'", filename);
}
params_for_tracee.fd_to_close = (shared_log != stderr) ? fileno(shared_log) : -1;
params_for_tracee.run_euid = (statbuf.st_mode & S_ISUID) ? statbuf.st_uid : run_uid;
params_for_tracee.run_egid = (statbuf.st_mode & S_ISGID) ? statbuf.st_gid : run_gid;
params_for_tracee.argv = argv;
/*
* On NOMMU, can be safely freed only after execve in tracee.
* It's hard to know when that happens, so we just leak it.
*/
params_for_tracee.pathname = NOMMU_SYSTEM ? strdup(pathname) : pathname;
#if defined HAVE_PRCTL && defined PR_SET_PTRACER && defined PR_SET_PTRACER_ANY
if (daemonized_tracer)
prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
#endif
pid = fork();
if (pid < 0) {
perror_msg_and_die("fork");
}
if ((pid != 0 && daemonized_tracer)
|| (pid == 0 && !daemonized_tracer)
) {
/* We are to become the tracee. Two cases:
* -D: we are parent
* not -D: we are child
*/
exec_or_die();
}
/* We are the tracer */
if (!daemonized_tracer) {
strace_child = pid;
if (!use_seize) {
/* child did PTRACE_TRACEME, nothing to do in parent */
} else {
if (!NOMMU_SYSTEM) {
/* Wait until child stopped itself */
int status;
while (waitpid(pid, &status, WSTOPPED) < 0) {
if (errno == EINTR)
continue;
perror_msg_and_die("waitpid");
}
if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGSTOP) {
kill_save_errno(pid, SIGKILL);
perror_msg_and_die("Unexpected wait status %x", status);
}
}
/* Else: NOMMU case, we have no way to sync.
* Just attach to it as soon as possible.
* This means that we may miss a few first syscalls...
*/
if (ptrace_attach_or_seize(pid)) {
kill_save_errno(pid, SIGKILL);
perror_msg_and_die("Can't attach to %d", pid);
}
if (!NOMMU_SYSTEM)
kill(pid, SIGCONT);
}
tcp = alloctcb(pid);
if (!NOMMU_SYSTEM)
tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
else
tcp->flags |= TCB_ATTACHED | TCB_STARTUP;
newoutf(tcp);
}
else {
/* With -D, we are *child* here, IOW: different pid. Fetch it: */
strace_tracer_pid = getpid();
/* The tracee is our parent: */
pid = getppid();
alloctcb(pid);
/* attaching will be done later, by startup_attach */
/* note: we don't do newoutf(tcp) here either! */
/* NOMMU BUG! -D mode is active, we (child) return,
* and we will scribble over parent's stack!
* When parent later unpauses, it segfaults.
*
* We work around it
* (1) by declaring exec_or_die() NORETURN,
* hopefully compiler will just jump to it
* instead of call (won't push anything to stack),
* (2) by trying very hard in exec_or_die()
* to not use any stack,
* (3) having a really big (PATH_MAX) stack object
* in this function, which creates a "buffer" between
* child's and parent's stack pointers.
* This may save us if (1) and (2) failed
* and compiler decided to use stack in exec_or_die() anyway
* (happens on i386 because of stack parameter passing).
*
* A cleaner solution is to use makecontext + setcontext
* to create a genuine separate stack and execute on it.
*/
}
}
#if USE_SEIZE
static void
test_ptrace_seize(void)
{
int pid;
/* Need fork for test. NOMMU has no forks */
if (NOMMU_SYSTEM) {
post_attach_sigstop = 0; /* this sets use_seize to 1 */
return;
}
pid = fork();
if (pid < 0)
perror_msg_and_die("fork");
if (pid == 0) {
pause();
_exit(0);
}
/* PTRACE_SEIZE, unlike ATTACH, doesn't force tracee to trap. After
* attaching tracee continues to run unless a trap condition occurs.
* PTRACE_SEIZE doesn't affect signal or group stop state.
*/
if (ptrace(PTRACE_SEIZE, pid, 0, 0) == 0) {
post_attach_sigstop = 0; /* this sets use_seize to 1 */
} else if (debug_flag) {
fprintf(stderr, "PTRACE_SEIZE doesn't work\n");
}
kill(pid, SIGKILL);
while (1) {
int status, tracee_pid;
errno = 0;
tracee_pid = waitpid(pid, &status, 0);
if (tracee_pid <= 0) {
if (errno == EINTR)
continue;
perror_msg_and_die("%s: unexpected wait result %d",
__func__, tracee_pid);
}
if (WIFSIGNALED(status)) {
return;
}
error_msg_and_die("%s: unexpected wait status %x",
__func__, status);
}
}
#else /* !USE_SEIZE */
# define test_ptrace_seize() ((void)0)
#endif
static unsigned
get_os_release(void)
{
unsigned rel;
const char *p;
struct utsname u;
if (uname(&u) < 0)
perror_msg_and_die("uname");
/* u.release has this form: "3.2.9[-some-garbage]" */
rel = 0;
p = u.release;
for (;;) {
if (!(*p >= '0' && *p <= '9'))
error_msg_and_die("Bad OS release string: '%s'", u.release);
/* Note: this open-codes KERNEL_VERSION(): */
rel = (rel << 8) | atoi(p);
if (rel >= KERNEL_VERSION(1,0,0))
break;
while (*p >= '0' && *p <= '9')
p++;
if (*p != '.') {
if (rel >= KERNEL_VERSION(0,1,0)) {
/* "X.Y-something" means "X.Y.0" */
rel <<= 8;
break;
}
error_msg_and_die("Bad OS release string: '%s'", u.release);
}
p++;
}
return rel;
}
/*
* Initialization part of main() was eating much stack (~0.5k),
* which was unused after init.
* We can reuse it if we move init code into a separate function.
*
* Don't want main() to inline us and defeat the reason
* we have a separate function.
*/
static void ATTRIBUTE_NOINLINE
init(int argc, char *argv[])
{
struct tcb *tcp;
int c, i;
int optF = 0;
unsigned int tcbi;
struct sigaction sa;
progname = argv[0] ? argv[0] : "strace";
/* Make sure SIGCHLD has the default action so that waitpid
definitely works without losing track of children. The user
should not have given us a bogus state to inherit, but he might
have. Arguably we should detect SIG_IGN here and pass it on
to children, but probably noone really needs that. */
signal(SIGCHLD, SIG_DFL);
strace_tracer_pid = getpid();
os_release = get_os_release();
/* Allocate the initial tcbtab. */
tcbtabsize = argc; /* Surely enough for all -p args. */
tcbtab = calloc(tcbtabsize, sizeof(tcbtab[0]));
if (!tcbtab)
die_out_of_memory();
tcp = calloc(tcbtabsize, sizeof(*tcp));
if (!tcp)
die_out_of_memory();
for (tcbi = 0; tcbi < tcbtabsize; tcbi++)
tcbtab[tcbi] = tcp++;
shared_log = stderr;
set_sortby(DEFAULT_SORTBY);
set_personality(DEFAULT_PERSONALITY);
qualify("trace=all");
qualify("abbrev=all");
qualify("verbose=all");
#if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
# error Bug in DEFAULT_QUAL_FLAGS
#endif
qualify("signal=all");
while ((c = getopt(argc, argv,
"+b:cCdfFhiqrtTvVwxyz"
#ifdef USE_LIBUNWIND
"k"
#endif
"D"
"a:e:o:O:p:s:S:u:E:P:I:")) != EOF) {
switch (c) {
case 'b':
if (strcmp(optarg, "execve") != 0)
error_msg_and_die("Syscall '%s' for -b isn't supported",
optarg);
detach_on_execve = 1;
break;
case 'c':
if (cflag == CFLAG_BOTH) {
error_msg_and_die("-c and -C are mutually exclusive");
}
cflag = CFLAG_ONLY_STATS;
break;
case 'C':
if (cflag == CFLAG_ONLY_STATS) {
error_msg_and_die("-c and -C are mutually exclusive");
}
cflag = CFLAG_BOTH;
break;
case 'd':
debug_flag = 1;
break;
case 'D':
daemonized_tracer = 1;
break;
case 'F':
optF = 1;
break;
case 'f':
followfork++;
break;
case 'h':
usage(stdout, 0);
break;
case 'i':
iflag = 1;
break;
case 'q':
qflag++;
break;
case 'r':
rflag = 1;
/* fall through to tflag++ */
case 't':
tflag++;
break;
case 'T':
Tflag = 1;
break;
case 'w':
count_wallclock = 1;
break;
case 'x':
xflag++;
break;
case 'y':
show_fd_path++;
break;
case 'v':
qualify("abbrev=none");
break;
case 'V':
printf("%s -- version %s\n", PACKAGE_NAME, VERSION);
exit(0);
break;
case 'z':
not_failing_only = 1;
break;
case 'a':
acolumn = string_to_uint(optarg);
if (acolumn < 0)
error_opt_arg(c, optarg);
break;
case 'e':
qualify(optarg);
break;
case 'o':
outfname = strdup(optarg);
break;
case 'O':
i = string_to_uint(optarg);
if (i < 0)
error_opt_arg(c, optarg);
set_overhead(i);
break;
case 'p':
process_opt_p_list(optarg);
break;
case 'P':
pathtrace_select(optarg);
break;
case 's':
i = string_to_uint(optarg);
if (i < 0)
error_opt_arg(c, optarg);
max_strlen = i;
break;
case 'S':
set_sortby(optarg);
break;
case 'u':
username = strdup(optarg);
break;
#ifdef USE_LIBUNWIND
case 'k':
stack_trace_enabled = true;
break;
#endif
case 'E':
if (putenv(optarg) < 0)
die_out_of_memory();
break;
case 'I':
opt_intr = string_to_uint(optarg);
if (opt_intr <= 0 || opt_intr >= NUM_INTR_OPTS)
error_opt_arg(c, optarg);
break;
default:
usage(stderr, 1);
break;
}
}
argv += optind;
/* argc -= optind; - no need, argc is not used below */
acolumn_spaces = malloc(acolumn + 1);
if (!acolumn_spaces)
die_out_of_memory();
memset(acolumn_spaces, ' ', acolumn);
acolumn_spaces[acolumn] = '\0';
/* Must have PROG [ARGS], or -p PID. Not both. */
if (!argv[0] == !nprocs)
usage(stderr, 1);
if (nprocs != 0 && daemonized_tracer) {
error_msg_and_die("-D and -p are mutually exclusive");
}
if (!followfork)
followfork = optF;
if (followfork >= 2 && cflag) {
error_msg_and_die("(-c or -C) and -ff are mutually exclusive");
}
if (count_wallclock && !cflag) {
error_msg_and_die("-w must be given with (-c or -C)");
}
if (cflag == CFLAG_ONLY_STATS) {
if (iflag)
error_msg("-%c has no effect with -c", 'i');
#ifdef USE_LIBUNWIND
if (stack_trace_enabled)
error_msg("-%c has no effect with -c", 'k');
#endif
if (rflag)
error_msg("-%c has no effect with -c", 'r');
if (tflag)
error_msg("-%c has no effect with -c", 't');
if (Tflag)
error_msg("-%c has no effect with -c", 'T');
if (show_fd_path)
error_msg("-%c has no effect with -c", 'y');
}
#ifdef USE_LIBUNWIND
if (stack_trace_enabled)
unwind_init();
#endif
/* See if they want to run as another user. */
if (username != NULL) {
struct passwd *pent;
if (getuid() != 0 || geteuid() != 0) {
error_msg_and_die("You must be root to use the -u option");
}
pent = getpwnam(username);
if (pent == NULL) {
error_msg_and_die("Cannot find user '%s'", username);
}
run_uid = pent->pw_uid;
run_gid = pent->pw_gid;
}
else {
run_uid = getuid();
run_gid = getgid();
}
if (followfork)
ptrace_setoptions |= PTRACE_O_TRACECLONE |
PTRACE_O_TRACEFORK |
PTRACE_O_TRACEVFORK;
if (debug_flag)
fprintf(stderr, "ptrace_setoptions = %#x\n", ptrace_setoptions);
test_ptrace_seize();
/* Check if they want to redirect the output. */
if (outfname) {
/* See if they want to pipe the output. */
if (outfname[0] == '|' || outfname[0] == '!') {
/*
* We can't do the <outfname>.PID funny business
* when using popen, so prohibit it.
*/
if (followfork >= 2)
error_msg_and_die("Piping the output and -ff are mutually exclusive");
shared_log = strace_popen(outfname + 1);
}
else if (followfork < 2)
shared_log = strace_fopen(outfname);
} else {
/* -ff without -o FILE is the same as single -f */
if (followfork >= 2)
followfork = 1;
}
if (!outfname || outfname[0] == '|' || outfname[0] == '!') {
char *buf = malloc(BUFSIZ);
if (!buf)
die_out_of_memory();
setvbuf(shared_log, buf, _IOLBF, BUFSIZ);
}
if (outfname && argv[0]) {
if (!opt_intr)
opt_intr = INTR_NEVER;
qflag = 1;
}
if (!opt_intr)
opt_intr = INTR_WHILE_WAIT;
/* argv[0] -pPID -oFILE Default interactive setting
* yes 0 0 INTR_WHILE_WAIT
* no 1 0 INTR_WHILE_WAIT
* yes 0 1 INTR_NEVER
* no 1 1 INTR_WHILE_WAIT
*/
sigemptyset(&empty_set);
sigemptyset(&blocked_set);
/* startup_child() must be called before the signal handlers get
* installed below as they are inherited into the spawned process.
* Also we do not need to be protected by them as during interruption
* in the startup_child() mode we kill the spawned process anyway.
*/
if (argv[0]) {
if (!NOMMU_SYSTEM || daemonized_tracer)
hide_log_until_execve = 1;
skip_one_b_execve = 1;
startup_child(argv);
}
sa.sa_handler = SIG_IGN;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sigaction(SIGTTOU, &sa, NULL); /* SIG_IGN */
sigaction(SIGTTIN, &sa, NULL); /* SIG_IGN */
if (opt_intr != INTR_ANYWHERE) {
if (opt_intr == INTR_BLOCK_TSTP_TOO)
sigaction(SIGTSTP, &sa, NULL); /* SIG_IGN */
/*
* In interactive mode (if no -o OUTFILE, or -p PID is used),
* fatal signals are blocked while syscall stop is processed,
* and acted on in between, when waiting for new syscall stops.
* In non-interactive mode, signals are ignored.
*/
if (opt_intr == INTR_WHILE_WAIT) {
sigaddset(&blocked_set, SIGHUP);
sigaddset(&blocked_set, SIGINT);
sigaddset(&blocked_set, SIGQUIT);
sigaddset(&blocked_set, SIGPIPE);
sigaddset(&blocked_set, SIGTERM);
sa.sa_handler = interrupt;
}
/* SIG_IGN, or set handler for these */
sigaction(SIGHUP, &sa, NULL);
sigaction(SIGINT, &sa, NULL);
sigaction(SIGQUIT, &sa, NULL);
sigaction(SIGPIPE, &sa, NULL);
sigaction(SIGTERM, &sa, NULL);
}
if (nprocs != 0 || daemonized_tracer)
startup_attach();
/* Do we want pids printed in our -o OUTFILE?
* -ff: no (every pid has its own file); or
* -f: yes (there can be more pids in the future); or
* -p PID1,PID2: yes (there are already more than one pid)
*/
print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
}
static struct tcb *
pid2tcb(int pid)
{
unsigned int i;
if (pid <= 0)
return NULL;
for (i = 0; i < tcbtabsize; i++) {
struct tcb *tcp = tcbtab[i];
if (tcp->pid == pid)
return tcp;
}
return NULL;
}
static void
cleanup(void)
{
unsigned int i;
struct tcb *tcp;
int fatal_sig;
/* 'interrupted' is a volatile object, fetch it only once */
fatal_sig = interrupted;
if (!fatal_sig)
fatal_sig = SIGTERM;
for (i = 0; i < tcbtabsize; i++) {
tcp = tcbtab[i];
if (!tcp->pid)
continue;
if (debug_flag)
fprintf(stderr,
"cleanup: looking at pid %u\n", tcp->pid);
if (tcp->pid == strace_child) {
kill(tcp->pid, SIGCONT);
kill(tcp->pid, fatal_sig);
}
detach(tcp);
}
if (cflag)
call_summary(shared_log);
}
static void
interrupt(int sig)
{
interrupted = sig;
}
static void
print_debug_info(const int pid, int status)
{
const unsigned int event = (unsigned int) status >> 16;
char buf[sizeof("WIFEXITED,exitcode=%u") + sizeof(int)*3 /*paranoia:*/ + 16];
char evbuf[sizeof(",EVENT_VFORK_DONE (%u)") + sizeof(int)*3 /*paranoia:*/ + 16];
strcpy(buf, "???");
if (WIFSIGNALED(status))
#ifdef WCOREDUMP
sprintf(buf, "WIFSIGNALED,%ssig=%s",
WCOREDUMP(status) ? "core," : "",
signame(WTERMSIG(status)));
#else
sprintf(buf, "WIFSIGNALED,sig=%s",
signame(WTERMSIG(status)));
#endif
if (WIFEXITED(status))
sprintf(buf, "WIFEXITED,exitcode=%u", WEXITSTATUS(status));
if (WIFSTOPPED(status))
sprintf(buf, "WIFSTOPPED,sig=%s", signame(WSTOPSIG(status)));
#ifdef WIFCONTINUED
/* Should never be seen */
if (WIFCONTINUED(status))
strcpy(buf, "WIFCONTINUED");
#endif
evbuf[0] = '\0';
if (event != 0) {
static const char *const event_names[] = {
[PTRACE_EVENT_CLONE] = "CLONE",
[PTRACE_EVENT_FORK] = "FORK",
[PTRACE_EVENT_VFORK] = "VFORK",
[PTRACE_EVENT_VFORK_DONE] = "VFORK_DONE",
[PTRACE_EVENT_EXEC] = "EXEC",
[PTRACE_EVENT_EXIT] = "EXIT",
/* [PTRACE_EVENT_STOP (=128)] would make biggish array */
};
const char *e = "??";
if (event < ARRAY_SIZE(event_names))
e = event_names[event];
else if (event == PTRACE_EVENT_STOP)
e = "STOP";
sprintf(evbuf, ",EVENT_%s (%u)", e, event);
}
fprintf(stderr, " [wait(0x%06x) = %u] %s%s\n", status, pid, buf, evbuf);
}
static struct tcb *
maybe_allocate_tcb(const int pid, int status)
{
if (!WIFSTOPPED(status)) {
if (detach_on_execve && pid == strace_child) {
/* example: strace -bexecve sh -c 'exec true' */
strace_child = 0;
return NULL;
}
/*
* This can happen if we inherited an unknown child.
* Example: (sleep 1 & exec strace true)
*/
error_msg("Exit of unknown pid %u ignored", pid);
return NULL;
}
if (followfork) {
/* We assume it's a fork/vfork/clone child */
struct tcb *tcp = alloctcb(pid);
tcp->flags |= TCB_ATTACHED | TCB_STARTUP | post_attach_sigstop;
newoutf(tcp);
if (!qflag)
fprintf(stderr, "Process %d attached\n", pid);
return tcp;
} else {
/* This can happen if a clone call used
* CLONE_PTRACE itself.
*/
ptrace(PTRACE_CONT, pid, (char *) 0, 0);
error_msg("Stop of unknown pid %u seen, PTRACE_CONTed it", pid);
return NULL;
}
}
static struct tcb *
maybe_switch_tcbs(struct tcb *tcp, const int pid)
{
FILE *fp;
struct tcb *execve_thread;
long old_pid = 0;
if (ptrace(PTRACE_GETEVENTMSG, pid, NULL, (long) &old_pid) < 0)
return tcp;
/* Avoid truncation in pid2tcb() param passing */
if (old_pid <= 0 || old_pid == pid)
return tcp;
if ((unsigned long) old_pid > UINT_MAX)
return tcp;
execve_thread = pid2tcb(old_pid);
/* It should be !NULL, but I feel paranoid */
if (!execve_thread)
return tcp;
if (execve_thread->curcol != 0) {
/*
* One case we are here is -ff:
* try "strace -oLOG -ff test/threaded_execve"
*/
fprintf(execve_thread->outf, " <pid changed to %d ...>\n", pid);
/*execve_thread->curcol = 0; - no need, see code below */
}
/* Swap output FILEs (needed for -ff) */
fp = execve_thread->outf;
execve_thread->outf = tcp->outf;
tcp->outf = fp;
/* And their column positions */
execve_thread->curcol = tcp->curcol;
tcp->curcol = 0;
/* Drop leader, but close execve'd thread outfile (if -ff) */
droptcb(tcp);
/* Switch to the thread, reusing leader's outfile and pid */
tcp = execve_thread;
tcp->pid = pid;
if (cflag != CFLAG_ONLY_STATS) {
printleader(tcp);
tprintf("+++ superseded by execve in pid %lu +++\n", old_pid);
line_ended();
tcp->flags |= TCB_REPRINT;
}
return tcp;
}
static void
print_signalled(struct tcb *tcp, const int pid, int status)
{
if (pid == strace_child) {
exit_code = 0x100 | WTERMSIG(status);
strace_child = 0;
}
if (cflag != CFLAG_ONLY_STATS
&& (qual_flags[WTERMSIG(status)] & QUAL_SIGNAL)
) {
printleader(tcp);
#ifdef WCOREDUMP
tprintf("+++ killed by %s %s+++\n",
signame(WTERMSIG(status)),
WCOREDUMP(status) ? "(core dumped) " : "");
#else
tprintf("+++ killed by %s +++\n",
signame(WTERMSIG(status)));
#endif
line_ended();
}
}
static void
print_exited(struct tcb *tcp, const int pid, int status)
{
if (pid == strace_child) {
exit_code = WEXITSTATUS(status);
strace_child = 0;
}
if (cflag != CFLAG_ONLY_STATS &&
qflag < 2) {
printleader(tcp);
tprintf("+++ exited with %d +++\n", WEXITSTATUS(status));
line_ended();
}
}
static void
print_stopped(struct tcb *tcp, const siginfo_t *si, const unsigned int sig)
{
if (cflag != CFLAG_ONLY_STATS
&& !hide_log_until_execve
&& (qual_flags[sig] & QUAL_SIGNAL)
) {
printleader(tcp);
if (si) {
tprintf("--- %s ", signame(sig));
printsiginfo(si, verbose(tcp));
tprints(" ---\n");
} else
tprintf("--- stopped by %s ---\n", signame(sig));
line_ended();
}
}
static void
startup_tcb(struct tcb *tcp)
{
if (debug_flag)
fprintf(stderr, "pid %d has TCB_STARTUP, initializing it\n",
tcp->pid);
tcp->flags &= ~TCB_STARTUP;
if (!use_seize) {
if (debug_flag)
fprintf(stderr, "setting opts 0x%x on pid %d\n",
ptrace_setoptions, tcp->pid);
if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, ptrace_setoptions) < 0) {
if (errno != ESRCH) {
/* Should never happen, really */
perror_msg_and_die("PTRACE_SETOPTIONS");
}
}
}
}
/* Returns true iff the main trace loop has to continue. */
static bool
trace(void)
{
int pid;
int wait_errno;
int status;
bool stopped;
unsigned int sig;
unsigned int event;
struct tcb *tcp;
struct rusage ru;
if (interrupted)
return false;
/*
* Used to exit simply when nprocs hits zero, but in this testcase:
* int main() { _exit(!!fork()); }
* under strace -f, parent sometimes (rarely) manages
* to exit before we see the first stop of the child,
* and we are losing track of it:
* 19923 clone(...) = 19924
* 19923 exit_group(1) = ?
* 19923 +++ exited with 1 +++
* Exiting only when wait() returns ECHILD works better.
*/
if (popen_pid != 0) {
/* However, if -o|logger is in use, we can't do that.
* Can work around that by double-forking the logger,
* but that loses the ability to wait for its completion
* on exit. Oh well...
*/
if (nprocs == 0)
return false;
}
if (interactive)
sigprocmask(SIG_SETMASK, &empty_set, NULL);
pid = wait4(-1, &status, __WALL, (cflag ? &ru : NULL));
wait_errno = errno;
if (interactive)
sigprocmask(SIG_BLOCK, &blocked_set, NULL);
if (pid < 0) {
if (wait_errno == EINTR)
return true;
if (nprocs == 0 && wait_errno == ECHILD)
return false;
/*
* If nprocs > 0, ECHILD is not expected,
* treat it as any other error here:
*/
errno = wait_errno;
perror_msg_and_die("wait4(__WALL)");
}
if (pid == popen_pid) {
if (!WIFSTOPPED(status))
popen_pid = 0;
return true;
}
if (debug_flag)
print_debug_info(pid, status);
/* Look up 'pid' in our table. */
tcp = pid2tcb(pid);
if (!tcp) {
tcp = maybe_allocate_tcb(pid, status);
if (!tcp)
return true;
}
if (WIFSTOPPED(status))
get_regs(pid);
else
clear_regs();
event = (unsigned int) status >> 16;
if (event == PTRACE_EVENT_EXEC) {
/*
* Under Linux, execve changes pid to thread leader's pid,
* and we see this changed pid on EVENT_EXEC and later,
* execve sysexit. Leader "disappears" without exit
* notification. Let user know that, drop leader's tcb,
* and fix up pid in execve thread's tcb.
* Effectively, execve thread's tcb replaces leader's tcb.
*
* BTW, leader is 'stuck undead' (doesn't report WIFEXITED
* on exit syscall) in multithreaded programs exactly
* in order to handle this case.
*
* PTRACE_GETEVENTMSG returns old pid starting from Linux 3.0.
* On 2.6 and earlier, it can return garbage.
*/
if (os_release >= KERNEL_VERSION(3,0,0))
tcp = maybe_switch_tcbs(tcp, pid);
if (detach_on_execve && !skip_one_b_execve) {
detach(tcp); /* do "-b execve" thingy */
return true;
}
skip_one_b_execve = 0;
}
/* Set current output file */
current_tcp = tcp;
if (cflag) {
tv_sub(&tcp->dtime, &ru.ru_stime, &tcp->stime);
tcp->stime = ru.ru_stime;
}
if (WIFSIGNALED(status)) {
print_signalled(tcp, pid, status);
droptcb(tcp);
return true;
}
if (WIFEXITED(status)) {
print_exited(tcp, pid, status);
droptcb(tcp);
return true;
}
if (!WIFSTOPPED(status)) {
/*
* Neither signalled, exited or stopped.
* How could that be?
*/
error_msg("pid %u not stopped!", pid);
droptcb(tcp);
return true;
}
/* Is this the very first time we see this tracee stopped? */
if (tcp->flags & TCB_STARTUP) {
startup_tcb(tcp);
if (get_scno(tcp) == 1)
tcp->s_prev_ent = tcp->s_ent;
}
sig = WSTOPSIG(status);
if (event != 0) {
/* Ptrace event */
#if USE_SEIZE
if (event == PTRACE_EVENT_STOP) {
/*
* PTRACE_INTERRUPT-stop or group-stop.
* PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
*/
switch (sig) {
case SIGSTOP:
case SIGTSTP:
case SIGTTIN:
case SIGTTOU:
stopped = true;
goto show_stopsig;
}
}
#endif
goto restart_tracee_with_sig_0;
}
/*
* Is this post-attach SIGSTOP?
* Interestingly, the process may stop
* with STOPSIG equal to some other signal
* than SIGSTOP if we happend to attach
* just before the process takes a signal.
*/
if (sig == SIGSTOP && (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)) {
if (debug_flag)
fprintf(stderr, "ignored SIGSTOP on pid %d\n", tcp->pid);
tcp->flags &= ~TCB_IGNORE_ONE_SIGSTOP;
goto restart_tracee_with_sig_0;
}
if (sig != syscall_trap_sig) {
siginfo_t si;
/*
* True if tracee is stopped by signal
* (as opposed to "tracee received signal").
* TODO: shouldn't we check for errno == EINVAL too?
* We can get ESRCH instead, you know...
*/
stopped = ptrace(PTRACE_GETSIGINFO, pid, 0, (long) &si) < 0;
#if USE_SEIZE
show_stopsig:
#endif
print_stopped(tcp, stopped ? NULL : &si, sig);
if (!stopped)
/* It's signal-delivery-stop. Inject the signal */
goto restart_tracee;
/* It's group-stop */
if (use_seize) {
/*
* This ends ptrace-stop, but does *not* end group-stop.
* This makes stopping signals work properly on straced process
* (that is, process really stops. It used to continue to run).
*/
if (ptrace_restart(PTRACE_LISTEN, tcp, 0) < 0) {
/* Note: ptrace_restart emitted error message */
exit_code = 1;
return false;
}
return true;
}
/* We don't have PTRACE_LISTEN support... */
goto restart_tracee;
}
/* We handled quick cases, we are permitted to interrupt now. */
if (interrupted)
return false;
/*
* This should be syscall entry or exit.
* Handle it.
*/
if (trace_syscall(tcp) < 0) {
/*
* ptrace() failed in trace_syscall().
* Likely a result of process disappearing mid-flight.
* Observed case: exit_group() or SIGKILL terminating
* all processes in thread group.
* We assume that ptrace error was caused by process death.
* We used to detach(tcp) here, but since we no longer
* implement "detach before death" policy/hack,
* we can let this process to report its death to us
* normally, via WIFEXITED or WIFSIGNALED wait status.
*/
return true;
}
restart_tracee_with_sig_0:
sig = 0;
restart_tracee:
if (ptrace_restart(PTRACE_SYSCALL, tcp, sig) < 0) {
/* Note: ptrace_restart emitted error message */
exit_code = 1;
return false;
}
return true;
}
int
main(int argc, char *argv[])
{
init(argc, argv);
while (trace())
;
cleanup();
fflush(NULL);
if (shared_log != stderr)
fclose(shared_log);
if (popen_pid) {
while (waitpid(popen_pid, NULL, 0) < 0 && errno == EINTR)
;
}
if (exit_code > 0xff) {
/* Avoid potential core file clobbering. */
struct_rlimit rlim = {0, 0};
set_rlimit(RLIMIT_CORE, &rlim);
/* Child was killed by a signal, mimic that. */
exit_code &= 0xff;
signal(exit_code, SIG_DFL);
raise(exit_code);
/* Paranoia - what if this signal is not fatal?
Exit with 128 + signo then. */
exit_code += 128;
}
return exit_code;
}