[PATCH] Do not trace children created with CLONE_UNTRACED flag

[Wang Chao]

If clone is called with flag CLONE_UNTRACED, I think we should
not set CLONE_PTRACE flag in its arguments.

* defs.h [LINUX]: New flag to indicate that the clone is called
  with CLONE_UNTRACED, and we do not setbpt on it.
* util.c [LINUX]: Define CLONE_UNTRACED.
  [LINUX] (setbpt): Check it.
* process.c [LINUX] (internal_fork): Check for TCB_CLONE_UNTRACED.

Signed-off-by: Wang Chao <wang.chao at cn.fujitsu.com>
---
 defs.h    |    1 +
 process.c |    7 +++++++
 util.c    |    7 +++++++
 3 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/defs.h b/defs.h
index 4b9c29e..cee8551 100644
--- a/defs.h
+++ b/defs.h
@@ -383,6 +383,7 @@ struct tcb {
 # endif
 # define TCB_CLONE_THREAD  010000 /* CLONE_THREAD set in creating syscall */
 # define TCB_GROUP_EXITING 020000 /* TCB_EXITING was exit_group, not _exit */
+# define TCB_CLONE_UNTRACED 040000 /* clone a new child with CLONE_UNTRACED */
 # include <sys/syscall.h>
 # ifndef __NR_exit_group
 # /* Hack: Most headers around are too old to have __NR_exit_group.  */
diff --git a/process.c b/process.c
index 8af960a..f3f0901 100644
--- a/process.c
+++ b/process.c
@@ -809,6 +809,13 @@ internal_fork(struct tcb *tcp)
 		if (!(tcp->flags & TCB_FOLLOWFORK))
 			return 0;
 
+		if (tcp->flags & TCB_CLONE_UNTRACED) {
+			tcp->flags &= ~TCB_CLONE_UNTRACED;
+			if (!(tcp->nchildren > 0))
+				tcp->flags &= ~TCB_FOLLOWFORK;
+			return 0;
+		}
+
 		bpt = tcp->flags & TCB_BPTSET;
 
 		if (syserror(tcp)) {
diff --git a/util.c b/util.c
index 07cbfde..380c16d 100644
--- a/util.c
+++ b/util.c
@@ -1271,6 +1271,9 @@ printcall(struct tcb *tcp)
 #  ifndef CLONE_STOPPED
 #   define CLONE_STOPPED   0x02000000
 #  endif
+#  ifndef CLONE_UNTRACED
+#   define CLONE_UNTRACED  0x00800000
+#  endif
 
 #  ifdef IA64
 
@@ -1537,6 +1540,10 @@ setbpt(struct tcb *tcp)
 		   clear also CLONE_VM but only in the CLONE_VFORK case as
 		   otherwise we would break pthread_create.  */
 
+		if (tcp->u_arg[arg0_index] & CLONE_UNTRACED) {
+			tcp->flags |= TCB_CLONE_UNTRACED;
+			return 0;
+		}
 		if ((arg_setup (tcp, &state) < 0
 		    || set_arg0 (tcp, &state,
 				 (tcp->u_arg[arg0_index] | CLONE_PTRACE)
-- 
1.6.5.2