Author: kib
Date: Thu Aug 7 05:47:53 2014
New Revision: 269656
URL: http://svnweb.freebsd.org/changeset/base/269656
Log:
Correct the problems with the ptrace(2) making the debuggee an orphan.
One problem is inferior(9) looping due to the process tree becoming a
graph instead of tree if the parent is traced by child. Another issue
is due to the use of p_oppid to restore the original parent/child
relationship, because real parent could already exited and its pid
reused (noted by mjg).
Add the function proc_realparent(9), which calculates the parent for
given process. It uses the flag P_TREE_FIRST_ORPHAN to detect the head
element of the p_orphan list and than stepping back to its container
to find the parent process. If the parent has already exited, the
init(8) is returned.
Move the P_ORPHAN and the new helper flag from the p_flag* to new
p_treeflag field of struct proc, which is protected by proctree lock
instead of proc lock, since the orphans relationship is managed under
the proctree_lock already.
The remaining uses of p_oppid in ptrace(PT_DETACH) and process
reapping are replaced by proc_realparent(9).
Phabric: D417
Reviewed by: jhb
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Modified:
head/bin/ps/ps.1
head/sys/kern/kern_exit.c
head/sys/kern/kern_proc.c
head/sys/kern/sys_process.c
head/sys/sys/proc.h
Modified: head/bin/ps/ps.1
==============================================================================
--- head/bin/ps/ps.1 Thu Aug 7 03:50:30 2014 (r269655)
+++ head/bin/ps/ps.1 Thu Aug 7 05:47:53 2014 (r269656)
@@ -29,7 +29,7 @@
.\" @(#)ps.1 8.3 (Berkeley) 4/18/94
.\" $FreeBSD$
.\"
-.Dd June 6, 2014
+.Dd August 7, 2014
.Dt PS 1
.Os
.Sh NAME
@@ -332,7 +332,6 @@ the include file
.It Dv "P_SINGLE_BOUNDARY" Ta No "0x400000" Ta "Threads should suspend at user
boundary"
.It Dv "P_HWPMC" Ta No "0x800000" Ta "Process is using HWPMCs"
.It Dv "P_JAILED" Ta No "0x1000000" Ta "Process is in jail"
-.It Dv "P_ORPHAN" Ta No "0x2000000" Ta "Orphaned by original parent,
reparented to debugger"
.It Dv "P_INEXEC" Ta No "0x4000000" Ta "Process is in execve()"
.It Dv "P_STATCHILD" Ta No "0x8000000" Ta "Child process stopped or exited"
.It Dv "P_INMEM" Ta No "0x10000000" Ta "Loaded into memory"
Modified: head/sys/kern/kern_exit.c
==============================================================================
--- head/sys/kern/kern_exit.c Thu Aug 7 03:50:30 2014 (r269655)
+++ head/sys/kern/kern_exit.c Thu Aug 7 05:47:53 2014 (r269656)
@@ -97,16 +97,44 @@ SDT_PROBE_DEFINE1(proc, kernel, , exit,
/* Hook for NFS teardown procedure. */
void (*nlminfo_release_p)(struct proc *p);
+struct proc *
+proc_realparent(struct proc *child)
+{
+ struct proc *p, *parent;
+
+ sx_assert(&proctree_lock, SX_LOCKED);
+ if ((child->p_treeflag & P_TREE_ORPHANED) == 0) {
+ return (child->p_pptr->p_pid == child->p_oppid ?
+ child->p_pptr : initproc);
+ }
+ for (p = child; (p->p_treeflag & P_TREE_FIRST_ORPHAN) == 0;) {
+ /* Cannot use LIST_PREV(), since the list head is not known. */
+ p = __containerof(p->p_orphan.le_prev, struct proc,
+ p_orphan.le_next);
+ KASSERT((p->p_treeflag & P_TREE_ORPHANED) != 0,
+ ("missing P_ORPHAN %p", p));
+ }
+ parent = __containerof(p->p_orphan.le_prev, struct proc,
+ p_orphans.lh_first);
+ return (parent);
+}
+
static void
clear_orphan(struct proc *p)
{
+ struct proc *p1;
- PROC_LOCK_ASSERT(p, MA_OWNED);
-
- if (p->p_flag & P_ORPHAN) {
- LIST_REMOVE(p, p_orphan);
- p->p_flag &= ~P_ORPHAN;
+ sx_assert(&proctree_lock, SA_XLOCKED);
+ if ((p->p_treeflag & P_TREE_ORPHANED) == 0)
+ return;
+ if ((p->p_treeflag & P_TREE_FIRST_ORPHAN) != 0) {
+ p1 = LIST_NEXT(p, p_orphan);
+ if (p1 != NULL)
+ p1->p_treeflag |= P_TREE_FIRST_ORPHAN;
+ p->p_treeflag &= ~P_TREE_FIRST_ORPHAN;
}
+ LIST_REMOVE(p, p_orphan);
+ p->p_treeflag &= ~P_TREE_ORPHANED;
}
/*
@@ -772,7 +800,9 @@ proc_reap(struct thread *td, struct proc
* If we got the child via a ptrace 'attach', we need to give it back
* to the old parent.
*/
- if (p->p_oppid && (t = pfind(p->p_oppid)) != NULL) {
+ if (p->p_oppid != 0) {
+ t = proc_realparent(p);
+ PROC_LOCK(t);
PROC_LOCK(p);
proc_reparent(p, t);
p->p_oppid = 0;
@@ -1243,8 +1273,15 @@ proc_reparent(struct proc *child, struct
clear_orphan(child);
if (child->p_flag & P_TRACED) {
- LIST_INSERT_HEAD(&child->p_pptr->p_orphans, child, p_orphan);
- child->p_flag |= P_ORPHAN;
+ if (LIST_EMPTY(&child->p_pptr->p_orphans)) {
+ child->p_treeflag |= P_TREE_FIRST_ORPHAN;
+ LIST_INSERT_HEAD(&child->p_pptr->p_orphans, child,
+ p_orphan);
+ } else {
+ LIST_INSERT_AFTER(child,
+ LIST_FIRST(&child->p_pptr->p_orphans), p_orphan);
+ }
+ child->p_treeflag |= P_TREE_ORPHANED;
}
child->p_pptr = parent;
Modified: head/sys/kern/kern_proc.c
==============================================================================
--- head/sys/kern/kern_proc.c Thu Aug 7 03:50:30 2014 (r269655)
+++ head/sys/kern/kern_proc.c Thu Aug 7 05:47:53 2014 (r269656)
@@ -263,14 +263,15 @@ proc_fini(void *mem, int size)
* Is p an inferior of the current process?
*/
int
-inferior(p)
- register struct proc *p;
+inferior(struct proc *p)
{
sx_assert(&proctree_lock, SX_LOCKED);
- for (; p != curproc; p = p->p_pptr)
+ PROC_LOCK_ASSERT(p, MA_OWNED);
+ for (; p != curproc; p = proc_realparent(p)) {
if (p->p_pid == 0)
return (0);
+ }
return (1);
}
Modified: head/sys/kern/sys_process.c
==============================================================================
--- head/sys/kern/sys_process.c Thu Aug 7 03:50:30 2014 (r269655)
+++ head/sys/kern/sys_process.c Thu Aug 7 05:47:53 2014 (r269656)
@@ -917,19 +917,11 @@ kern_ptrace(struct thread *td, int req,
case PT_DETACH:
/* reset process parent */
if (p->p_oppid != p->p_pptr->p_pid) {
- struct proc *pp;
-
PROC_LOCK(p->p_pptr);
sigqueue_take(p->p_ksi);
PROC_UNLOCK(p->p_pptr);
- PROC_UNLOCK(p);
- pp = pfind(p->p_oppid);
- if (pp == NULL)
- pp = initproc;
- else
- PROC_UNLOCK(pp);
- PROC_LOCK(p);
+ pp = proc_realparent(p);
proc_reparent(p, pp);
if (pp == initproc)
p->p_sigparent = SIGCHLD;
Modified: head/sys/sys/proc.h
==============================================================================
--- head/sys/sys/proc.h Thu Aug 7 03:50:30 2014 (r269655)
+++ head/sys/sys/proc.h Thu Aug 7 05:47:53 2014 (r269656)
@@ -549,6 +549,7 @@ struct proc {
int p_pendingcnt; /* how many signals are pending */
struct itimers *p_itimers; /* (c) POSIX interval timers. */
struct procdesc *p_procdesc; /* (e) Process descriptor, if any. */
+ u_int p_treeflag; /* (e) P_TREE flags */
/* End area that is zeroed on creation. */
#define p_endzero p_magic
@@ -632,7 +633,7 @@ struct proc {
#define P_SINGLE_BOUNDARY 0x400000 /* Threads should suspend at user
boundary. */
#define P_HWPMC 0x800000 /* Process is using HWPMCs */
#define P_JAILED 0x1000000 /* Process is in jail. */
-#define P_ORPHAN 0x2000000 /* Orphaned. */
+#define P_UNUSED1 0x2000000
#define P_INEXEC 0x4000000 /* Process is in execve(). */
#define P_STATCHILD 0x8000000 /* Child process stopped or exited. */
#define P_INMEM 0x10000000 /* Loaded into memory. */
@@ -647,6 +648,11 @@ struct proc {
/* These flags are kept in p_flag2. */
#define P2_INHERIT_PROTECTED 0x00000001 /* New children get
P_PROTECTED. */
+/* Flags protected by proctree_lock, kept in p_treeflags. */
+#define P_TREE_ORPHANED 0x00000001 /* Reparented, on
orphan list */
+#define P_TREE_FIRST_ORPHAN 0x00000002 /* First element of
orphan
+ list */
+
/*
* These were process status values (p_stat), now they are only used in
* legacy conversion code.
@@ -887,6 +893,7 @@ int proc_getenvv(struct thread *td, stru
void procinit(void);
void proc_linkup0(struct proc *p, struct thread *td);
void proc_linkup(struct proc *p, struct thread *td);
+struct proc *proc_realparent(struct proc *child);
void proc_reap(struct thread *td, struct proc *p, int *status, int options);
void proc_reparent(struct proc *child, struct proc *newparent);
struct pstats *pstats_alloc(void);
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