From: Denys Vlasenko <dvlasenk@redhat.com>
Date: Tue, 14 May 2013 14:07:46 +0000 (+0200)
Subject: Hide startup syscalls.
X-Git-Tag: v4.8~14
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2a3d27552f17a5b378344620bec7d255bac65a8d;p=strace

Hide startup syscalls.

Tested with "./strace [-D] [-q] [-bexecve] env true",
all cases seem to work.

* defs.h: Declare new variable: bool hide_log_until_execve.
* strace.c: Define hide_log_until_execve.
Rename skip_startup_execve to skip_one_b_execve.
(startup_child): Do not set skip_one_b_execve = 1 here.
(init): If "strace PROG" case (as opposed to "strace -pPID"),
set skip_one_b_execve and hide_log_until_execve to 1.
(trace): Don't print signal messages if hide_log_until_execve == 1.
* syscall.c (trace_syscall_entering):
Skip syscall printing if hide_log_until_execve == 1.
Reset hide_log_until_execve if we enter execve syscall.
(trace_syscall_exiting): Skip syscall printing if hide_log_until_execve == 1.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
---

diff --git a/defs.h b/defs.h
index 58cdf999..3f07c4f3 100644
--- a/defs.h
+++ b/defs.h
@@ -542,6 +542,7 @@ extern bool Tflag;
 extern unsigned int qflag;
 extern bool not_failing_only;
 extern bool show_fd_path;
+extern bool hide_log_until_execve;
 /* are we filtering traces based on paths? */
 extern const char **paths_selected;
 #define tracing_paths (paths_selected != NULL)
diff --git a/strace.c b/strace.c
index f6f6e898..84a443c0 100644
--- a/strace.c
+++ b/strace.c
@@ -124,7 +124,10 @@ bool not_failing_only = 0;
 bool show_fd_path = 0;
 
 static bool detach_on_execve = 0;
-static bool skip_startup_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;
@@ -1163,7 +1166,6 @@ startup_child(char **argv)
 					kill_save_errno(pid, SIGKILL);
 					perror_msg_and_die("Unexpected wait status %x", status);
 				}
-				skip_startup_execve = 1;
 			}
 			/* Else: NOMMU case, we have no way to sync.
 			 * Just attach to it as soon as possible.
@@ -1192,7 +1194,6 @@ startup_child(char **argv)
 		alloctcb(pid);
 		/* attaching will be done later, by startup_attach */
 		/* note: we don't do newoutf(tcp) here either! */
-		skip_startup_execve = 1;
 
 		/* NOMMU BUG! -D mode is active, we (child) return,
 		 * and we will scribble over parent's stack!
@@ -1788,6 +1789,8 @@ init(int argc, char *argv[])
 	 * in the startup_child() mode we kill the spawned process anyway.
 	 */
 	if (argv[0]) {
+		hide_log_until_execve = 1;
+		skip_one_b_execve = 1;
 		startup_child(argv);
 	}
 
@@ -2074,11 +2077,10 @@ trace(void)
 		}
  dont_switch_tcbs:
 
-		if (event == PTRACE_EVENT_EXEC && detach_on_execve) {
-			if (!skip_startup_execve)
-				detach(tcp);
-			/* This was initial execve for "strace PROG". Skip. */
-			skip_startup_execve = 0;
+		if (event == PTRACE_EVENT_EXEC) {
+			if (detach_on_execve && !skip_one_b_execve)
+				detach(tcp); /* do "-b execve" thingy */
+			skip_one_b_execve = 0;
 		}
 
 		/* Set current output file */
@@ -2222,7 +2224,7 @@ trace(void)
 # define PC_FORMAT_STR	""
 # define PC_FORMAT_ARG	/* nothing */
 #endif
-				if (qflag < 2) {
+				if (qflag < 2 && !hide_log_until_execve) {
 					printleader(tcp);
 					if (!stopped) {
 						tprintf("--- %s ", signame(sig));
diff --git a/syscall.c b/syscall.c
index 833dacd3..7efee0e4 100644
--- a/syscall.c
+++ b/syscall.c
@@ -1985,6 +1985,14 @@ trace_syscall_entering(struct tcb *tcp)
 		goto ret;
 	}
 
+	if (   sys_execve == tcp->s_ent->sys_func
+# if defined(SPARC) || defined(SPARC64)
+	    || sys_execv == tcp->s_ent->sys_func
+# endif
+	   ) {
+		hide_log_until_execve = 0;
+	}
+
 #if defined(SYS_socket_subcall) || defined(SYS_ipc_subcall)
 	while (1) {
 # ifdef SYS_socket_subcall
@@ -2015,7 +2023,7 @@ trace_syscall_entering(struct tcb *tcp)
 
 	tcp->flags &= ~TCB_FILTERED;
 
-	if (cflag == CFLAG_ONLY_STATS) {
+	if (cflag == CFLAG_ONLY_STATS || hide_log_until_execve) {
 		res = 0;
 		goto ret;
 	}
@@ -2503,7 +2511,7 @@ trace_syscall_exiting(struct tcb *tcp)
 		get_error(tcp); /* never fails */
 		if (need_fork_exec_workarounds)
 			syscall_fixup_for_fork_exec(tcp);
-		if (filtered(tcp))
+		if (filtered(tcp) || hide_log_until_execve)
 			goto ret;
 	}