Do not deliver SIGTRAP on exec as the normal signal, use ptracestop() on

syscall exit path. Otherwise, if SIGTRAP is ignored, that tdsendsignal()
do not want to deliver the signal, and debugger never get a notification
of exec.

Found and tested by:	Anton Yuzhaninov <citrin citrin ru>
Discussed with:	jhb
MFC after:	2 weeks

2 files changed, 9 insertions, 11 deletions

diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index fe01142..4545848 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -777,16 +777,6 @@ interpret:
 	KNOTE_LOCKED(&p->p_klist, NOTE_EXEC);
 	p->p_flag &= ~P_INEXEC;
 
-	/*
-	 * If tracing the process, trap to the debugger so that
-	 * breakpoints can be set before the program executes.  We
-	 * have to use tdsignal() to deliver the signal to the current
-	 * thread since any other threads in this process will exit if
-	 * execve() succeeds.
-	 */
-	if (p->p_flag & P_TRACED)
-		tdsignal(td, SIGTRAP);
-
 	/* clear "fork but no exec" flag, as we _are_ execing */
 	p->p_acflag &= ~AFORK;
 
diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c
index cb0d929..bba4479 100644
--- a/sys/kern/subr_syscall.c
+++ b/sys/kern/subr_syscall.c
@@ -204,9 +204,17 @@ syscallret(struct thread *td, int error, struct syscall_args *sa __unused)
 	 * is not the case, this code will need to be revisited.
 	 */
 	STOPEVENT(p, S_SCX, sa->code);
-	PTRACESTOP_SC(p, td, S_PT_SCX);
 	if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) {
 		PROC_LOCK(p);
+		/*
+		 * If tracing the execed process, trap to the debugger
+		 * so that breakpoints can be set before the program
+		 * executes.  If debugger requested tracing of syscall
+		 * returns, do it now too.
+		 */
+		if (traced && ((td->td_dbgflags & TDB_EXEC) != 0 ||
+		    (p->p_stops & S_PT_SCX) != 0))
+			ptracestop(td, SIGTRAP);
 		td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
 		PROC_UNLOCK(p);
 	}