ptrace(2) following fork(2)

ok miod@

lib/libc/sys/ptrace.2

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: ptrace.2,v 1.19 2005/07/20 21:51:36 miod Exp $
+.\"	$OpenBSD: ptrace.2,v 1.20 2005/09/14 20:55:59 kettenis Exp $
 .\"	$NetBSD: ptrace.2,v 1.3 1996/02/23 01:39:41 jtc Exp $
 .\"
 .\" This file is in the public domain.
@@ -232,6 +232,69 @@ will return
 .Li -1
 and set
 .Va errno .
+.It Dv PT_SET_EVENT_MASK
+This request can be used to specify which events in the traced process
+should be reported to the tracing process.
+These events are specified in a
+.Dq Li "struct ptrace_event"
+defined as:
+.Bd -literal -offset indent
+typedef struct ptrace_event {
+	int	pe_set_event;
+} ptrace_event_t;
+.Ed
+Where
+.Fa pe_set_event
+is the set of events to be reported.
+This set is formed by OR'ing together the following values:
+.Bl -tag -width 18n
+.It PTRACE_FORK
+Report
+.Xr fork 2 .
+.El
+.Pp
+A pointer to this structure is passed in
+.Fa addr .
+The
+.Fa data
+argument should be set to
+.Li sizeof(struct ptrace_event) .
+.It Dv PT_GET_EVENT_MASK
+This request can be used to determine which events in the traced
+process will be reported.
+The information is read into the
+.Dq Li struct ptrace_event
+pointed to by
+.Fa addr .
+The
+.Fa data
+argument should be set to
+.Li sizeof(struct ptrace_event) .
+.It Dv PT_GET_PROCESS_STATE
+This request reads the state information associated with the event
+that stopped the traced process.
+The information is reported in a
+.Dq Li "struct ptrace_state"
+defined as:
+.Bd -literal -offset indent
+typedef struct ptrace_state {
+	int	pe_report_event;
+	pid_t	pe_other_pid;
+} ptrace_state_t;
+.Ed
+Where
+.Fa pe_report_event
+is the event being reported.
+If the event being reported is
+.Dv PTRACE_FORK ,
+.Fa pe_other_pid
+will be set to the process ID of the other end of the fork.
+A pointer to this structure is passed in
+.Fa addr .
+The
+.Fa data
+argument should be set to
+.Li sizeof(struct ptrace_state) .
 .El
 .Pp
 Additionally, machine-specific requests can exist.

sys/kern/kern_exit.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_exit.c,v 1.54 2004/12/26 21:22:13 miod Exp $	*/
+/*	$OpenBSD: kern_exit.c,v 1.55 2005/09/14 20:55:59 kettenis Exp $	*/
 /*	$NetBSD: kern_exit.c,v 1.39 1996/04/22 01:38:25 christos Exp $	*/
 
 /*
@@ -540,6 +540,8 @@ void
 proc_zap(struct proc *p)
 {
 	pool_put(&rusage_pool, p->p_ru);
+	if (p->p_ptstat)
+		free(p->p_ptstat, M_SUBPROC);
 
 	/*
 	 * Finally finished with old proc entry.

sys/kern/kern_fork.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_fork.c,v 1.76 2005/05/29 03:20:41 deraadt Exp $	*/
+/*	$OpenBSD: kern_fork.c,v 1.77 2005/09/14 20:55:59 kettenis Exp $	*/
 /*	$NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $	*/
 
 /*
@@ -55,6 +55,7 @@
 #include <dev/rndvar.h>
 #include <sys/pool.h>
 #include <sys/mman.h>
+#include <sys/ptrace.h>
 
 #include <sys/syscallargs.h>
 
@@ -69,14 +70,31 @@ int	randompid;		/* when set to 1, pid's go random */
 pid_t	lastpid;
 struct	forkstat forkstat;
 
+void fork_return(void *);
 int pidtaken(pid_t);
 
+void
+fork_return(void *arg)
+{
+	struct proc *p = (struct proc *)arg;
+
+	if (p->p_flag & P_TRACED)
+		psignal(p, SIGTRAP);
+
+	child_return(p);
+}
+
 /*ARGSUSED*/
 int
 sys_fork(struct proc *p, void *v, register_t *retval)
 {
-	return (fork1(p, SIGCHLD, FORK_FORK, NULL, 0, NULL,
-	    NULL, retval, NULL));
+	int flags;
+
+	flags = FORK_FORK;
+	if (p->p_ptmask & PTRACE_FORK)
+		flags |= FORK_PTRACE;
+	return (fork1(p, SIGCHLD, flags, NULL, 0,
+	    fork_return, NULL, retval, NULL));
 }
 
 /*ARGSUSED*/
@@ -220,6 +238,8 @@ fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize,
 	if (p1->p_flag & P_PROFIL)
 		startprofclock(p2);
 	p2->p_flag |= (p1->p_flag & (P_SUGID | P_SUGIDEXEC));
+	if (flags & FORK_PTRACE)
+		p2->p_flag |= (p1->p_flag & P_TRACED);
 	p2->p_cred = pool_get(&pcred_pool, PR_WAITOK);
 	bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred));
 	p2->p_cred->p_refcnt = 1;
@@ -329,6 +349,23 @@ fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize,
 		lastpid = 1 + (randompid ? arc4random() : lastpid) % PID_MAX;
 	} while (pidtaken(lastpid));
 	p2->p_pid = lastpid;
+	if (p2->p_flag & P_TRACED) {
+		p2->p_oppid = p1->p_pid;
+		if (p2->p_pptr != p1->p_pptr)
+			proc_reparent(p2, p1->p_pptr);
+
+		/*
+		 * Set ptrace status.
+		 */
+		if (flags & FORK_FORK) {
+			p2->p_ptstat = malloc(sizeof(*p2->p_ptstat),
+			    M_SUBPROC, M_WAITOK);
+			p1->p_ptstat->pe_report_event = PTRACE_FORK;
+			p2->p_ptstat->pe_report_event = PTRACE_FORK;
+			p1->p_ptstat->pe_other_pid = p2->p_pid;
+			p2->p_ptstat->pe_other_pid = p1->p_pid;
+		}
+	}
 
 	LIST_INSERT_HEAD(&allproc, p2, p_list);
 	LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
@@ -385,6 +422,12 @@ fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize,
 		while (p2->p_flag & P_PPWAIT)
 			tsleep(p1, PWAIT, "ppwait", 0);
 
+	/*
+	 * If we're tracing the child, alert the parent too.
+	 */
+	if ((flags & FORK_PTRACE) && (p1->p_flag & P_TRACED))
+		psignal(p1, SIGTRAP);
+
 	/*
 	 * Return child pid to parent process,
 	 * marking us as parent via retval[1].

sys/kern/sys_process.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: sys_process.c,v 1.31 2005/08/02 18:04:07 kettenis Exp $	*/
+/*	$OpenBSD: sys_process.c,v 1.32 2005/09/14 20:55:59 kettenis Exp $	*/
 /*	$NetBSD: sys_process.c,v 1.55 1996/05/15 06:17:47 tls Exp $	*/
 
 /*-
@@ -88,6 +88,7 @@ sys_ptrace(p, v, retval)
 	struct uio uio;
 	struct iovec iov;
 	struct ptrace_io_desc piod;
+	struct ptrace_event pe;
 	struct reg *regs;
 #if defined (PT_SETFPREGS) || defined (PT_GETFPREGS)
 	struct fpreg *fpregs;
@@ -179,6 +180,9 @@ sys_ptrace(p, v, retval)
 #ifdef PT_STEP
 	case  PT_STEP:
 #endif
+	case  PT_SET_EVENT_MASK:
+	case  PT_GET_EVENT_MASK:
+	case  PT_GET_PROCESS_STATE:
 	case  PT_GETREGS:
 	case  PT_SETREGS:
 #ifdef PT_GETFPREGS
@@ -232,6 +236,10 @@ sys_ptrace(p, v, retval)
 		/* Just set the trace flag. */
 		SET(t->p_flag, P_TRACED);
 		t->p_oppid = t->p_pptr->p_pid;
+		if (t->p_ptstat == NULL)
+			t->p_ptstat = malloc(sizeof(*t->p_ptstat),
+			    M_SUBPROC, M_WAITOK);
+		bzero(t->p_ptstat, sizeof(*t->p_ptstat));
 		return (0);
 
 	case  PT_WRITE_I:		/* XXX no separate I and D spaces */
@@ -366,6 +374,8 @@ sys_ptrace(p, v, retval)
 		CLR(t->p_flag, P_TRACED|P_WAITED);
 
 	sendsig:
+		bzero(t->p_ptstat, sizeof(*t->p_ptstat));
+
 		/* Finally, deliver the requested signal (or none). */
 		if (t->p_stat == SSTOP) {
 			t->p_xstat = SCARG(uap, data);
@@ -401,9 +411,32 @@ sys_ptrace(p, v, retval)
 		t->p_oppid = t->p_pptr->p_pid;
 		if (t->p_pptr != p)
 			proc_reparent(t, p);
+		if (t->p_ptstat == NULL)
+			t->p_ptstat = malloc(sizeof(*t->p_ptstat),
+			    M_SUBPROC, M_WAITOK);
 		SCARG(uap, data) = SIGSTOP;
 		goto sendsig;
 
+	case  PT_GET_EVENT_MASK:
+		if (SCARG(uap, data) != sizeof(pe))
+			return (EINVAL);
+		bzero(&pe, sizeof(pe));
+		pe.pe_set_event = t->p_ptmask;
+		return (copyout(&pe, SCARG(uap, addr), sizeof(pe)));
+	case  PT_SET_EVENT_MASK:
+		if (SCARG(uap, data) != sizeof(pe))
+			return (EINVAL);
+		if ((error = copyin(SCARG(uap, addr), &pe, sizeof(pe))))
+			return (error);
+		t->p_ptmask = pe.pe_set_event;
+		return (0);
+
+	case  PT_GET_PROCESS_STATE:
+		if (SCARG(uap, data) != sizeof(*t->p_ptstat))
+			return (EINVAL);
+		return (copyout(t->p_ptstat, SCARG(uap, addr),
+		    sizeof(*t->p_ptstat)));
+
 	case  PT_SETREGS:
 		KASSERT((p->p_flag & P_SYSTEM) == 0);
 		if ((error = procfs_checkioperm(p, t)) != 0)

sys/sys/proc.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: proc.h,v 1.79 2005/05/29 03:20:42 deraadt Exp $	*/
+/*	$OpenBSD: proc.h,v 1.80 2005/09/14 20:55:59 kettenis Exp $	*/
 /*	$NetBSD: proc.h,v 1.44 1996/04/22 01:23:21 christos Exp $	*/
 
 /*-
@@ -186,6 +186,9 @@ struct	proc {
 
 	void	*p_systrace;		/* Back pointer to systrace */
 
+	int	p_ptmask;		/* Ptrace event mask */
+	struct	ptrace_state *p_ptstat;	/* Ptrace state */
+
 	int	p_siglist;		/* Signals arrived but not delivered. */
 
 	struct	vnode *p_textvp;	/* Vnode of executable. */
@@ -357,6 +360,7 @@ struct uidinfo *uid_find(uid_t);
 #define FORK_NOZOMBIE	0x00000040
 #define FORK_SHAREVM	0x00000080
 #define FORK_SIGHAND	0x00000200
+#define FORK_PTRACE	0x00000400
 
 #define	PIDHASH(pid)	(&pidhashtbl[(pid) & pidhash])
 extern LIST_HEAD(pidhashhead, proc) *pidhashtbl;

sys/sys/ptrace.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ptrace.h,v 1.8 2003/06/02 23:28:21 millert Exp $	*/
+/*	$OpenBSD: ptrace.h,v 1.9 2005/09/14 20:55:59 kettenis Exp $	*/
 /*	$NetBSD: ptrace.h,v 1.21 1996/02/09 18:25:26 christos Exp $	*/
 
 /*-
@@ -61,6 +61,22 @@ struct ptrace_io_desc {
 #define PIOD_READ_I	3	/* Read from I space */
 #define PIOD_WRITE_I	4	/* Write to I space */
 
+#define PT_SET_EVENT_MASK	12
+#define PT_GET_EVENT_MASK	13
+
+typedef struct ptrace_event {
+	int	pe_set_event;
+} ptrace_event_t;
+
+#define PTRACE_FORK	0x0002	/* Report forks */
+
+#define PT_GET_PROCESS_STATE	14
+
+typedef struct ptrace_state {
+	int	pe_report_event;
+	pid_t	pe_other_pid;
+} ptrace_state_t;
+
 #define	PT_FIRSTMACH	32	/* for machine-specific requests */
 #include <machine/ptrace.h>	/* machine-specific requests, if any */