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strace.c
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/*
* Copyright (c) 1991, 1992 Paul Kranenburg <[email protected]>
* Copyright (c) 1993 Branko Lankester <[email protected]>
* Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <[email protected]>
* Copyright (c) 1996-1999 Wichert Akkerman <[email protected]>
* 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
#if defined(IA64)
# include <asm/ptrace_offsets.h>
#endif
/* 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
cflag_t cflag = CFLAG_NONE;
unsigned int followfork = 0;
unsigned int ptrace_setoptions = 0;
unsigned int xflag = 0;
bool need_fork_exec_workarounds = 0;
bool debug_flag = 0;
bool Tflag = 0;
bool iflag = 0;
bool count_wallclock = 0;
unsigned int qflag = 0;
/* Which WSTOPSIG(status) value marks syscall traps? */
static unsigned int syscall_trap_sig = SIGTRAP;
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\
-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 die(void) __attribute__ ((noreturn));
static void 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. */
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)
{
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;
if (tcp->flags & TCB_BPTSET)
clearbpt(tcp);
/*
* 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 (;;) {
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)
{
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];