Cleanups on top of "handle SIGTRAP properly" change,
based on Dmitry's comments.
* defs.h ([p]error_msg[_and_die]): Declare new functions.
* strace.c (SYSCALLTRAP): Rename to syscall_trap_sig.
([p]error_msg[_and_die]): Define new functions.
(strace_tracer_pid): New variable, it controls which pid will
do cleanup on exit via [p]error_msg_and_die.
(main): Set strace_tracer_pid to our initial pid.
(startup_attach): Change strace_tracer_pid if we are in -D mode.
(test_ptrace_setoptions_for_all): Minor changes to logic,
such as better diagnostic messages.
diff --git a/strace.c b/strace.c
index d83cbf6..16adba4 100644
--- a/strace.c
+++ b/strace.c
@@ -87,7 +87,7 @@
unsigned int ptrace_setoptions_followfork = 0;
unsigned int ptrace_setoptions_for_all = 0;
/* Which WSTOPSIG(status) value marks syscall traps? */
-static unsigned int SYSCALLTRAP = SIGTRAP;
+static unsigned int syscall_trap_sig = SIGTRAP;
int dtime = 0, xflag = 0, qflag = 0;
cflag_t cflag = CFLAG_NONE;
static int iflag = 0, interactive = 0, pflag_seen = 0, rflag = 0, tflag = 0;
@@ -116,6 +116,7 @@
static int exit_code = 0;
static int strace_child = 0;
+static int strace_tracer_pid = 0;
static char *username = NULL;
uid_t run_uid;
@@ -215,29 +216,62 @@
exit(exitval);
}
-static void error_msg_and_die(const char *fmt, ...)
-#if defined __GNUC__
- __attribute__ ((noreturn, format(printf, 1, 2)))
-#endif
-;
-static void error_msg_and_die(const char *fmt, ...)
+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;
- va_list p;
- va_start(p, fmt);
msg = NULL;
vasprintf(&msg, fmt, p);
if (msg) {
- fprintf(stderr, "%s: %s\n", progname, msg);
+ fflush(NULL);
+ if (err_no)
+ fprintf(stderr, "%s: %s: %s\n", progname, msg, strerror(err_no));
+ else
+ fprintf(stderr, "%s: %s\n", progname, msg);
free(msg);
}
- va_end(p);
+}
- /* TODO? cflag = 0; -- or else cleanup() may print summary */
- cleanup();
- fflush(NULL);
- _exit(1);
+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();
}
#ifdef SVR4
@@ -429,14 +463,17 @@
}
if (pid) { /* parent */
/*
- * Wait for child to attach to straced process
- * (our parent). Child SIGKILLs us after it attached.
- * Parent's wait() is unblocked by our death,
+ * 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++) {
@@ -613,8 +650,8 @@
cleanup();
exit(1);
}
- if ((pid != 0 && daemonized_tracer) /* parent: to become a traced process */
- || (pid == 0 && !daemonized_tracer) /* child: to become a traced process */
+ if ((pid != 0 && daemonized_tracer) /* -D: parent to become a traced process */
+ || (pid == 0 && !daemonized_tracer) /* not -D: child to become a traced process */
) {
pid = getpid();
#ifdef USE_PROCFS
@@ -710,6 +747,9 @@
}
/* We are the tracer. */
+ /* With -D, we are *child* here, IOW: different pid. Fetch it. */
+ strace_tracer_pid = getpid();
+
tcp = alloctcb(daemonized_tracer ? getppid() : pid);
if (daemonized_tracer) {
/* We want subsequent startup_attach() to attach to it. */
@@ -817,13 +857,13 @@
pid = fork();
if (pid < 0)
- error_msg_and_die("fork failed");
+ perror_msg_and_die("fork");
if (pid == 0) {
pid = getpid();
if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0)
- /* "parent, something is deeply wrong!" */
- kill(pid, SIGKILL);
+ /* Note: exits with exitcode 1 */
+ perror_msg_and_die("%s: PTRACE_TRACEME doesn't work", __func__);
kill(pid, SIGSTOP);
_exit(0); /* parent should see entry into this syscall */
}
@@ -837,10 +877,14 @@
if (errno == EINTR)
continue;
kill(pid, SIGKILL);
- error_msg_and_die("%s: unexpected wait result %d", __func__, tracee_pid);
+ perror_msg_and_die("%s: unexpected wait result %d", __func__, tracee_pid);
}
- if (WIFEXITED(status))
- break;
+ if (WIFEXITED(status)) {
+ if (WEXITSTATUS(status) == 0)
+ break;
+ /* PTRACE_TRACEME failed in child. This is fatal. */
+ exit(1);
+ }
if (!WIFSTOPPED(status)) {
kill(pid, SIGKILL);
error_msg_and_die("%s: unexpected wait status %x", __func__, status);
@@ -852,19 +896,21 @@
* and thus will decide to not use the option.
* IOW: the outcome of the test will be correct.
*/
- ptrace(PTRACE_SETOPTIONS, pid, 0L, test_options);
+ if (ptrace(PTRACE_SETOPTIONS, pid, 0L, test_options) < 0)
+ if (errno != EINVAL)
+ perror_msg("PTRACE_SETOPTIONS");
}
if (WSTOPSIG(status) == (SIGTRAP | 0x80)) {
it_worked = 1;
}
if (ptrace(PTRACE_SYSCALL, pid, 0L, 0L) < 0) {
kill(pid, SIGKILL);
- error_msg_and_die("PTRACE_SYSCALL doesn't work");
+ perror_msg_and_die("PTRACE_SYSCALL doesn't work");
}
}
if (it_worked) {
- SYSCALLTRAP = (SIGTRAP | 0x80);
+ syscall_trap_sig = (SIGTRAP | 0x80);
ptrace_setoptions_for_all = test_options;
if (debug)
fprintf(stderr, "ptrace_setoptions_for_all = %#x\n",
@@ -889,6 +935,8 @@
progname = argv[0] ? argv[0] : "strace";
+ strace_tracer_pid = getpid();
+
/* Allocate the initial tcbtab. */
tcbtabsize = argc; /* Surely enough for all -p args. */
if ((tcbtab = calloc(tcbtabsize, sizeof tcbtab[0])) == NULL) {
@@ -1000,7 +1048,7 @@
progname, optarg);
break;
}
- if (pid == getpid()) {
+ if (pid == strace_tracer_pid) {
fprintf(stderr, "%s: I'm sorry, I can't let you do that, Dave.\n", progname);
break;
}
@@ -1863,7 +1911,7 @@
break;
}
error = ptrace_restart(PTRACE_CONT, tcp,
- WSTOPSIG(status) == SYSCALLTRAP ? 0
+ WSTOPSIG(status) == syscall_trap_sig ? 0
: WSTOPSIG(status));
if (error < 0)
break;
@@ -2525,6 +2573,8 @@
fprintf(stderr, "PTRACE_EVENT_EXEC on pid %d (ignored)\n", tcp->pid);
return 0;
}
+ /* Some PTRACE_EVENT_foo we didn't ask for?! */
+ error_msg("Unexpected status %x on pid %d", status, tcp->pid);
return 1;
}
#endif
@@ -2756,7 +2806,7 @@
if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, options) < 0) {
if (errno != ESRCH) {
/* Should never happen, really */
- error_msg_and_die("PTRACE_SETOPTIONS");
+ perror_msg_and_die("PTRACE_SETOPTIONS");
}
}
}
@@ -2764,7 +2814,7 @@
goto tracing;
}
- if (WSTOPSIG(status) != SYSCALLTRAP) {
+ if (WSTOPSIG(status) != syscall_trap_sig) {
if (WSTOPSIG(status) == SIGSTOP &&
(tcp->flags & TCB_SIGTRAPPED)) {
/*