Minor tweaks in startup_child(). Logic isn't changed (but code is)
* strace.c (startup_attach): Tweak comment.
(startup_child): Move common code out of ifdef.
Indent nested ifdefs. Tweak comments. Remove two
unnecessary calls to getpid().
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
diff --git a/strace.c b/strace.c
index bdc2112..afb5d29 100644
--- a/strace.c
+++ b/strace.c
@@ -415,7 +415,7 @@
/*
* 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.
+ * between PTRACE_ATTACH and wait4() on SIGSTOP.
* We rely on cleanup() from this point on.
*/
if (interactive)
@@ -628,24 +628,22 @@
|| (pid == 0 && !daemonized_tracer) /* not -D: child to become a traced process */
) {
pid = getpid();
+ if (outf != stderr)
+ close(fileno(outf));
#ifdef USE_PROCFS
- if (outf != stderr) close(fileno(outf));
-#ifdef MIPS
+# ifdef MIPS
/* Kludge for SGI, see proc_open for details. */
sa.sa_handler = foobar;
sa.sa_flags = 0;
sigemptyset(&sa.sa_mask);
sigaction(SIGINT, &sa, NULL);
-#endif /* MIPS */
-#ifndef FREEBSD
+# endif
+# ifndef FREEBSD
pause();
-#else /* FREEBSD */
+# else
kill(pid, SIGSTOP); /* stop HERE */
-#endif /* FREEBSD */
+# endif
#else /* !USE_PROCFS */
- if (outf != stderr)
- close(fileno(outf));
-
if (!daemonized_tracer) {
if (ptrace(PTRACE_TRACEME, 0, (char *) 1, 0) < 0) {
perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
@@ -684,14 +682,14 @@
if (!daemonized_tracer) {
/*
- * Induce an immediate stop so that the parent
+ * Induce a ptrace stop. Tracer (our parent)
* will resume us with PTRACE_SYSCALL and display
- * this execve call normally.
- * Unless of course we're on a no-MMU system where
- * we vfork()-ed, so we cannot stop the child.
+ * the immediately following execve syscall.
+ * Can't do this on NOMMU systems, we are after
+ * vfork: parent is blocked, stopping would deadlock.
*/
if (!strace_vforked)
- kill(getpid(), SIGSTOP);
+ kill(pid, SIGSTOP);
} else {
struct sigaction sv_sigchld;
sigaction(SIGCHLD, NULL, &sv_sigchld);
@@ -715,20 +713,25 @@
perror_msg_and_die("exec");
}
- /* We are the tracer. */
- /* With -D, we are *child* here, IOW: different pid. Fetch it. */
- strace_tracer_pid = getpid();
+ /* We are the tracer */
- tcp = alloctcb(daemonized_tracer ? getppid() : pid);
- if (daemonized_tracer) {
- /* We want subsequent startup_attach() to attach to it. */
+ if (!daemonized_tracer) {
+ tcp = alloctcb(pid);
+ }
+ else {
+ /* With -D, *we* are child here, IOW: different pid. Fetch it: */
+ strace_tracer_pid = getpid();
+ /* The tracee is our parent: */
+ pid = getppid();
+ tcp = alloctcb(pid);
+ /* We want subsequent startup_attach() to attach to it: */
tcp->flags |= TCB_ATTACHED;
}
#ifdef USE_PROCFS
if (proc_open(tcp, 0) < 0) {
perror_msg_and_die("trouble opening proc file");
}
-#endif /* USE_PROCFS */
+#endif
}
#ifdef LINUX