From: David van Moolenbroek <david@minix3.org>
Date: Sat, 11 Jul 2009 13:22:56 +0000 (+0000)
Subject: PM: fix ptrace(T_EXIT) 'exit_proc: not idle' race condition.
X-Git-Tag: v3.1.5~220
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/zpipe.c?a=commitdiff_plain;h=1a9e07b0e514e6e6fa20c6fa7690e88e7449b74a;p=minix.git

PM: fix ptrace(T_EXIT) 'exit_proc: not idle' race condition.
---

diff --git a/include/minix/com.h b/include/minix/com.h
index 267c18734..b640c046d 100755
--- a/include/minix/com.h
+++ b/include/minix/com.h
@@ -711,9 +711,6 @@
 #define		PM_CORE_PROC		m1_i1
 #define		PM_CORE_SEGPTR		m1_p1
 #define PM_UNPAUSE_TR	(PM_BASE + 15)	/* interrupted process (for tracing) */
-#define PM_EXIT_TR	(PM_BASE + 16)	/* Tell FS about the exiting process
-					 * (for tracing)
-					 */
 
 /* Replies */
 #define PM_EXIT_REPLY	(PM_BASE + 20)	/* Reply from FS */
@@ -724,7 +721,6 @@
 #define PM_CORE_REPLY	(PM_BASE + 23)	/* Reply from FS */
 		/* PM_CORE_PROC m1_i1 */
 #define		PM_CORE_STATUS m1_i2	/* OK or failure */
-#define PM_EXIT_REPLY_TR (PM_BASE + 24)	/* Reply from FS */
 
 /* Parameters for the EXEC_NEWMEM call */
 #define EXC_NM_PROC	m1_i1		/* process that needs new map */
diff --git a/servers/pm/exec.c b/servers/pm/exec.c
index 7e7ff087a..5d702bca1 100644
--- a/servers/pm/exec.c
+++ b/servers/pm/exec.c
@@ -162,7 +162,7 @@ int result;
 
 			/* Use SIGILL signal that something went wrong */
 			rmp->mp_sigstatus = SIGILL;
-			exit_proc(rmp, 0, PM_EXIT);
+			exit_proc(rmp, 0, FALSE /*dump_core*/);
 			return;
 		}
 		setreply(rmp-mproc, result);
diff --git a/servers/pm/forkexit.c b/servers/pm/forkexit.c
index 26ddebb84..11a96061d 100644
--- a/servers/pm/forkexit.c
+++ b/servers/pm/forkexit.c
@@ -183,17 +183,17 @@ PUBLIC int do_exit()
 /* Perform the exit(status) system call. The real work is done by exit_proc(),
  * which is also called when a process is killed by a signal.
  */
-  exit_proc(mp, m_in.status, PM_EXIT);
+  exit_proc(mp, m_in.status, FALSE /*dump_core*/);
   return(SUSPEND);		/* can't communicate from beyond the grave */
 }
 
 /*===========================================================================*
  *				exit_proc				     *
  *===========================================================================*/
-PUBLIC void exit_proc(rmp, exit_status, exit_type)
+PUBLIC void exit_proc(rmp, exit_status, dump_core)
 register struct mproc *rmp;	/* pointer to the process to be terminated */
 int exit_status;		/* the process' exit status (for parent) */
-int exit_type;			/* one of PM_EXIT, PM_EXIT_TR, PM_DUMPCORE */
+int dump_core;			/* flag indicating whether to dump core */
 {
 /* A process is done.  Release most of the process' possessions.  If its
  * parent is waiting, release the rest, else keep the process slot and
@@ -206,14 +206,14 @@ int exit_type;			/* one of PM_EXIT, PM_EXIT_TR, PM_DUMPCORE */
   clock_t user_time, sys_time;
 
   /* Do not create core files for set uid execution */
-  if (exit_type == PM_DUMPCORE && rmp->mp_realuid != rmp->mp_effuid)
-	exit_type = PM_EXIT;
+  if (dump_core && rmp->mp_realuid != rmp->mp_effuid)
+	dump_core = FALSE;
 
   /* System processes are destroyed before informing FS, meaning that FS can
    * not get their CPU state, so we can't generate a coredump for them either.
    */
-  if (exit_type == PM_DUMPCORE && (rmp->mp_flags & PRIV_PROC))
-	exit_type = PM_EXIT;
+  if (dump_core && (rmp->mp_flags & PRIV_PROC))
+	dump_core = FALSE;
 
   proc_nr = (int) (rmp - mproc);	/* get process slot number */
   proc_nr_e = rmp->mp_endpoint;
@@ -254,7 +254,7 @@ int exit_type;			/* one of PM_EXIT, PM_EXIT_TR, PM_DUMPCORE */
 	/* Tell FS about the exiting process. */
 	if (rmp->mp_fs_call != PM_IDLE)
 		panic(__FILE__, "exit_proc: not idle", rmp->mp_fs_call);
-	rmp->mp_fs_call= exit_type;
+	rmp->mp_fs_call= dump_core ? PM_DUMPCORE : PM_EXIT;
 	r= notify(FS_PROC_NR);
 	if (r != OK) panic(__FILE__, "exit_proc: unable to notify FS", r);
 
@@ -289,7 +289,7 @@ int exit_type;			/* one of PM_EXIT, PM_EXIT_TR, PM_DUMPCORE */
   /* For normal exits, try to notify the parent as soon as possible.
    * For core dumps, notify the parent only once the core dump has been made.
    */
-  if (exit_type != PM_DUMPCORE)
+  if (!dump_core)
 	zombify(rmp);
 
   /* If the process has children, disinherit them.  INIT is the new parent. */
@@ -314,9 +314,9 @@ int exit_type;			/* one of PM_EXIT, PM_EXIT_TR, PM_DUMPCORE */
 /*===========================================================================*
  *				exit_restart				     *
  *===========================================================================*/
-PUBLIC void exit_restart(rmp, reply_type)
+PUBLIC void exit_restart(rmp, dump_core)
 struct mproc *rmp;		/* pointer to the process being terminated */
-int reply_type;			/* one of PM_EXIT_REPLY(_TR), PM_CORE_REPLY */
+int dump_core;			/* flag indicating whether to dump core */
 {
 /* FS replied to our exit or coredump request. Perform the second half of the
  * exit code.
@@ -324,7 +324,7 @@ int reply_type;			/* one of PM_EXIT_REPLY(_TR), PM_CORE_REPLY */
   int r;
 
   /* For core dumps, now is the right time to try to contact the parent. */
-  if (reply_type == PM_CORE_REPLY)
+  if (dump_core)
 	zombify(rmp);
 
   if (!(rmp->mp_flags & PRIV_PROC))
@@ -339,7 +339,7 @@ int reply_type;			/* one of PM_EXIT_REPLY(_TR), PM_CORE_REPLY */
   	panic(__FILE__, "exit_restart: vm_exit failed", r);
   }
 
-  if (reply_type == PM_EXIT_REPLY_TR && rmp->mp_parent != INIT_PROC_NR)
+  if ((rmp->mp_flags & TRACE_EXIT) && rmp->mp_parent != INIT_PROC_NR)
   {
 	/* Wake up the parent, completing the ptrace(T_EXIT) call */
 	mproc[rmp->mp_parent].mp_reply.reply_trace = 0;
@@ -434,7 +434,7 @@ struct mproc *rmp;
   if (rmp->mp_flags & ZOMBIE)
 	panic(__FILE__, "zombify: process was already a zombie", NO_NUM);
 
-  rmp->mp_flags &= (IN_USE|PRIV_PROC|EXITING);
+  rmp->mp_flags &= (IN_USE|PRIV_PROC|EXITING|TRACE_EXIT);
   rmp->mp_flags |= ZOMBIE;
 
   p_mp = &mproc[rmp->mp_parent];
diff --git a/servers/pm/main.c b/servers/pm/main.c
index bd083e532..508a469e9 100644
--- a/servers/pm/main.c
+++ b/servers/pm/main.c
@@ -44,6 +44,7 @@ FORWARD _PROTOTYPE( void pm_init, (void)				);
 FORWARD _PROTOTYPE( int get_nice_value, (int queue)			);
 FORWARD _PROTOTYPE( void send_work, (void)				);
 FORWARD _PROTOTYPE( void handle_fs_reply, (message *m_ptr)		);
+FORWARD _PROTOTYPE( void restart_sigs, (struct mproc *rmp)		);
 
 #define click_to_round_k(n) \
 	((unsigned) ((((unsigned long) (n) << CLICK_SHIFT) + 512) / 1024))
@@ -91,7 +92,6 @@ PUBLIC int main()
 	case PM_REBOOT_REPLY:
 	case PM_EXEC_REPLY:
 	case PM_CORE_REPLY:
-	case PM_EXIT_REPLY_TR:
 		if (who_e == FS_PROC_NR)
 		{
 			handle_fs_reply(&m_in);
@@ -379,9 +379,9 @@ void checkme(char *str, int line)
 	}
 }
 
-/*=========================================================================*
- *				send_work				   *
- *=========================================================================*/
+/*===========================================================================*
+ *				send_work				     *
+ *===========================================================================*/
 PRIVATE void send_work()
 {
 	int r, call;
@@ -460,7 +460,6 @@ PRIVATE void send_work()
 		}
 
 		case PM_EXIT:
-		case PM_EXIT_TR:
 			m.m_type= call;
 			m.PM_EXIT_PROC= rmp->mp_endpoint;
 
@@ -552,18 +551,7 @@ PRIVATE void send_work()
 	}
 	if (m.m_type != PM_IDLE)
 	{
-		if (rmp->mp_fs_call == PM_IDLE &&
-			rmp->mp_fs_call2 == PM_IDLE &&
-			(rmp->mp_flags & PM_SIG_PENDING))
-		{
-			rmp->mp_flags &= ~PM_SIG_PENDING;
-			check_pending(rmp);
-			if (!(rmp->mp_flags & PM_SIG_PENDING))
-			{
-				/* Allow the process to be scheduled */
-				sys_nice(rmp->mp_endpoint, rmp->mp_nice);
-			}
-		}
+		restart_sigs(rmp);
 	}
 	else if (report_reboot)
 	{
@@ -574,6 +562,9 @@ PRIVATE void send_work()
 	if (r != OK) panic("pm", "send_work: send failed", r);
 }
 
+/*===========================================================================*
+ *				handle_fs_reply				     *
+ *===========================================================================*/
 PRIVATE void handle_fs_reply(m_ptr)
 message *m_ptr;
 {
@@ -583,7 +574,6 @@ message *m_ptr;
 	switch(m_ptr->m_type)
 	{
 	case PM_EXIT_REPLY:
-	case PM_EXIT_REPLY_TR:
 		proc_e= m_ptr->PM_EXIT_PROC;
 		if (pm_isokendpt(proc_e, &proc_n) != OK)
 		{
@@ -596,7 +586,7 @@ message *m_ptr;
 		/* Call is finished */
 		rmp->mp_fs_call= PM_IDLE;
 
-		exit_restart(rmp, m_ptr->m_type);
+		exit_restart(rmp, FALSE /*dump_core*/);
 
 		break;
 
@@ -630,20 +620,8 @@ message *m_ptr;
 
 		exec_restart(rmp, m_ptr->PM_EXEC_STATUS);
 
-		if (rmp->mp_flags & PM_SIG_PENDING)
-		{
-			printf("handle_fs_reply: restarting signals\n");
-			rmp->mp_flags &= ~PM_SIG_PENDING;
-			check_pending(rmp);
-			if (!(rmp->mp_flags & PM_SIG_PENDING))
-			{
-				printf("handle_fs_reply: calling sys_nice\n");
-				/* Allow the process to be scheduled */
-				sys_nice(rmp->mp_endpoint, rmp->mp_nice);
-			}
-			else
-				printf("handle_fs_reply: more signals\n");
-		}
+		restart_sigs(rmp);
+
 		break;
 
 	case PM_CORE_REPLY:
@@ -663,7 +641,7 @@ message *m_ptr;
 		/* Call is finished */
 		rmp->mp_fs_call= PM_IDLE;
 
-		exit_restart(rmp, m_ptr->m_type);
+		exit_restart(rmp, TRUE /*dump_core*/);
 
 		break;
 	}
@@ -675,3 +653,25 @@ message *m_ptr;
 
 }
 
+/*===========================================================================*
+ *				restart_sigs				     *
+ *===========================================================================*/
+PRIVATE void restart_sigs(rmp)
+struct mproc *rmp;
+{
+
+	if (rmp->mp_fs_call != PM_IDLE || rmp->mp_fs_call2 != PM_IDLE)
+		return;
+
+	if (rmp->mp_flags & TRACE_EXIT) {
+		exit_proc(rmp, rmp->mp_exitstatus, FALSE /*dump_core*/);
+	}
+	else if (rmp->mp_flags & PM_SIG_PENDING) {
+		rmp->mp_flags &= ~PM_SIG_PENDING;
+		check_pending(rmp);
+		if (!(rmp->mp_flags & PM_SIG_PENDING)) {
+			/* Allow the process to be scheduled */
+			sys_nice(rmp->mp_endpoint, rmp->mp_nice);
+		}
+	}
+}
diff --git a/servers/pm/mproc.h b/servers/pm/mproc.h
index 2dce02e02..a9d536220 100644
--- a/servers/pm/mproc.h
+++ b/servers/pm/mproc.h
@@ -77,6 +77,7 @@ EXTERN struct mproc {
 #define PARTIAL_EXEC   0x8000	/* Process got a new map but no content */
 #define TOLD_PARENT   0x10000	/* Parent wait() completed, ZOMBIE off */
 #define EXITING       0x20000	/* set by EXIT, process is now exiting */
+#define TRACE_EXIT    0x40000	/* tracer is forcing this process to exit */
 
 #define NIL_MPROC ((struct mproc *) 0)
 
diff --git a/servers/pm/proto.h b/servers/pm/proto.h
index 8504b0076..ceaeccfc1 100644
--- a/servers/pm/proto.h
+++ b/servers/pm/proto.h
@@ -36,8 +36,8 @@ _PROTOTYPE( int do_fork_nb, (void)					);
 _PROTOTYPE( int do_exit, (void)						);
 _PROTOTYPE( int do_waitpid, (void)					);
 _PROTOTYPE( void exit_proc, (struct mproc *rmp, int exit_status,
-	int exit_type)							);
-_PROTOTYPE( void exit_restart, (struct mproc *rmp, int reply_type)	);
+	int dump_core)							);
+_PROTOTYPE( void exit_restart, (struct mproc *rmp, int dump_core)	);
 
 /* getset.c */
 _PROTOTYPE( int do_getset, (void)					);
diff --git a/servers/pm/signal.c b/servers/pm/signal.c
index 21d8d31c6..f3a49baf8 100644
--- a/servers/pm/signal.c
+++ b/servers/pm/signal.c
@@ -421,7 +421,6 @@ int signo;			/* signal to send to process (1 to _NSIG) */
   int s;
   int slot;
   int sigflags;
-  int exit_type;
 
   slot = (int) (rmp - mproc);
   if ((rmp->mp_flags & (IN_USE | EXITING)) != IN_USE) {
@@ -518,14 +517,16 @@ doterminate:
 	return;
   }
 
+  /* Terminate process */
   rmp->mp_sigstatus = (char) signo;
-  exit_type = PM_EXIT;
   if (sigismember(&core_sset, signo) && slot != FS_PROC_NR) {
 	printf("PM: coredump signal %d for %d / %s\n", signo, rmp->mp_pid,
 		rmp->mp_name);
-	exit_type = PM_DUMPCORE;
+	exit_proc(rmp, 0, TRUE /*dump_core*/);
+  }
+  else {
+  	exit_proc(rmp, 0, FALSE /*dump_core*/);
   }
-  exit_proc(rmp, 0, exit_type);		/* terminate process */
 }
 
 /*===========================================================================*
diff --git a/servers/pm/trace.c b/servers/pm/trace.c
index 3a0e1c7a2..fb3fc656d 100644
--- a/servers/pm/trace.c
+++ b/servers/pm/trace.c
@@ -112,7 +112,14 @@ PUBLIC int do_trace()
 
   switch (m_in.request) {
   case T_EXIT:		/* exit */
-	exit_proc(child, (int) m_in.data, PM_EXIT_TR);
+	child->mp_flags |= TRACE_EXIT;
+
+	/* Defer the exit if the traced process has an FS call pending. */
+	if (child->mp_fs_call != PM_IDLE || child->mp_fs_call2 != PM_IDLE)
+		child->mp_exitstatus = (int) m_in.data;	/* save for later */
+	else
+		exit_proc(child, (int) m_in.data, FALSE /*dump_core*/);
+
 	/* Do not reply to the caller until FS has processed the exit
 	 * request.
 	 */
diff --git a/servers/vfs/main.c b/servers/vfs/main.c
index 43912b6cc..49bb67408 100644
--- a/servers/vfs/main.c
+++ b/servers/vfs/main.c
@@ -533,12 +533,10 @@ PRIVATE void service_pm()
 			break;
 
 		case PM_EXIT:
-		case PM_EXIT_TR:
 			pm_exit(m.PM_EXIT_PROC);
 
 			/* Reply dummy status to PM for synchronization */
-			m.m_type= (call == PM_EXIT_TR ? PM_EXIT_REPLY_TR :
-				PM_EXIT_REPLY);
+			m.m_type= PM_EXIT_REPLY;
 			/* Keep m.PM_EXIT_PROC */
 
 			r= send(PM_PROC_NR, &m);