MFC 303001: Add PTRACE_VFORK to trace vfork events.

First, PL_FLAG_FORKED events now also set a PL_FLAG_VFORKED flag when
the new child was created via vfork() rather than fork().  Second, a
new PL_FLAG_VFORK_DONE event can now be enabled via the PTRACE_VFORK
event mask.  This new stop is reported after the vfork parent resumes
due to the child calling exit or exec.  Debuggers can use this stop to
reinsert breakpoints in the vfork parent process before it resumes.

5 files changed, 19 insertions, 2 deletions

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 4d96840..202ce25 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -728,6 +728,7 @@ do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
 	if (flags & RFPPWAIT) {
 		td->td_pflags |= TDP_RFPPWAIT;
 		td->td_rfppwait_p = p2;
+		td->td_dbgflags |= TDB_VFORK;
 	}
 	PROC_UNLOCK(p2);
 	if ((flags & RFSTOPPED) == 0) {
diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c
index f2b83f0..201d876 100644
--- a/sys/kern/subr_syscall.c
+++ b/sys/kern/subr_syscall.c
@@ -249,5 +249,13 @@ again:
 			cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz);
 		}
 		PROC_UNLOCK(p2);
+
+		if (td->td_dbgflags & TDB_VFORK) {
+			PROC_LOCK(p);
+			if (p->p_ptevents & PTRACE_VFORK)
+				ptracestop(td, SIGTRAP);
+			td->td_dbgflags &= ~TDB_VFORK;
+			PROC_UNLOCK(p);
+		}
 	}
 }
diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c
index c4533ce..5091abc 100644
--- a/sys/kern/sys_process.c
+++ b/sys/kern/sys_process.c
@@ -957,7 +957,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 		}
 		tmp = *(int *)addr;
 		if ((tmp & ~(PTRACE_EXEC | PTRACE_SCE | PTRACE_SCX |
-		    PTRACE_FORK | PTRACE_LWP)) != 0) {
+		    PTRACE_FORK | PTRACE_LWP | PTRACE_VFORK)) != 0) {
 			error = EINVAL;
 			break;
 		}
@@ -1296,7 +1296,11 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 		if (td2->td_dbgflags & TDB_FORK) {
 			pl->pl_flags |= PL_FLAG_FORKED;
 			pl->pl_child_pid = td2->td_dbg_forked;
-		}
+			if (td2->td_dbgflags & TDB_VFORK)
+				pl->pl_flags |= PL_FLAG_VFORKED;
+		} else if ((td2->td_dbgflags & (TDB_SCX | TDB_VFORK)) ==
+		    TDB_VFORK)
+			pl->pl_flags |= PL_FLAG_VFORK_DONE;
 		if (td2->td_dbgflags & TDB_CHILD)
 			pl->pl_flags |= PL_FLAG_CHILD;
 		if (td2->td_dbgflags & TDB_BORN)
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 1b8bda5..07b84db 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -398,6 +398,7 @@ do {									\
 #define	TDB_CHILD	0x00000100 /* New child indicator for ptrace() */
 #define	TDB_BORN	0x00000200 /* New LWP indicator for ptrace() */
 #define	TDB_EXIT	0x00000400 /* Exiting LWP indicator for ptrace() */
+#define	TDB_VFORK	0x00000800 /* vfork indicator for ptrace() */
 #define	TDB_FSTP	0x00001000 /* The thread is PT_ATTACH leader */
 
 /*
diff --git a/sys/sys/ptrace.h b/sys/sys/ptrace.h
index e2b6a5f..f5f1db2 100644
--- a/sys/sys/ptrace.h
+++ b/sys/sys/ptrace.h
@@ -89,6 +89,7 @@
 #define	PTRACE_SYSCALL	(PTRACE_SCE | PTRACE_SCX)
 #define	PTRACE_FORK	0x0008
 #define	PTRACE_LWP	0x0010
+#define	PTRACE_VFORK	0x0020
 
 #define	PTRACE_DEFAULT	(PTRACE_EXEC)
 
@@ -124,6 +125,8 @@ struct ptrace_lwpinfo {
 #define	PL_FLAG_CHILD	0x80	/* I am from child */
 #define	PL_FLAG_BORN	0x100	/* new LWP */
 #define	PL_FLAG_EXITED	0x200	/* exiting LWP */
+#define	PL_FLAG_VFORKED	0x400	/* new child via vfork */
+#define	PL_FLAG_VFORK_DONE 0x800 /* vfork parent has resumed */
 	sigset_t	pl_sigmask;	/* LWP signal mask */
 	sigset_t	pl_siglist;	/* LWP pending signal */
 	struct __siginfo pl_siginfo;	/* siginfo for signal */