[src/trunk]: src/sys/kern Add support for PTRACE_FORK. NB: This does not (yet...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/6236e969eb81
branches:  trunk
changeset: 769189:6236e969eb81
user:      christos <christos%NetBSD.org@localhost>
date:      Fri Sep 02 20:06:29 2011 +0000

description:
Add support for PTRACE_FORK. NB: This does not (yet) work for vfork(), because:
1. When we vfork() PL_PPWAIT is set, and that makes us do regular disposition
   of the TRAP signal, and not indirect through the debugger.
2. The parent needs to keep running, so that the debugger can release it.
   Unfortunately, with vfork() we cannot release the parent because it will
   eventually core-dump since the parent and the child cannot run on the
   same address space.

diffstat:

 sys/kern/kern_fork.c |  46 ++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 44 insertions(+), 2 deletions(-)

diffs (88 lines):

diff -r 50a105fe9f00 -r 6236e969eb81 sys/kern/kern_fork.c
--- a/sys/kern/kern_fork.c      Fri Sep 02 20:01:20 2011 +0000
+++ b/sys/kern/kern_fork.c      Fri Sep 02 20:06:29 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_fork.c,v 1.185 2011/08/23 13:01:25 christos Exp $ */
+/*     $NetBSD: kern_fork.c,v 1.186 2011/09/02 20:06:29 christos Exp $ */
 
 /*-
  * Copyright (c) 1999, 2001, 2004, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.185 2011/08/23 13:01:25 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.186 2011/09/02 20:06:29 christos Exp $");
 
 #include "opt_ktrace.h"
 
@@ -92,6 +92,7 @@
 #include <sys/syscallargs.h>
 #include <sys/uidinfo.h>
 #include <sys/sdt.h>
+#include <sys/ptrace.h>
 
 #include <uvm/uvm_extern.h>
 
@@ -218,6 +219,7 @@
        int             count;
        vaddr_t         uaddr;
        int             tnprocs;
+       int             tracefork;
        int             error = 0;
 
        p1 = l1->l_proc;
@@ -458,6 +460,35 @@
        LIST_INSERT_HEAD(&parent->p_children, p2, p_sibling);
        p2->p_exitsig = exitsig;                /* signal for parent on exit */
 
+       tracefork = (p1->p_slflag & (PSL_TRACEFORK|PSL_TRACED)) ==
+           (PSL_TRACEFORK|PSL_TRACED);
+       if (tracefork) {
+               p2->p_slflag |= PSL_TRACED;
+               p2->p_opptr = p2->p_pptr;
+               if (p2->p_pptr != p1->p_pptr) {
+                       struct proc *parent1 = p2->p_pptr;
+
+                       if (parent1->p_lock < p2->p_lock) {
+                               if (!mutex_tryenter(parent1->p_lock)) {
+                                       mutex_exit(p2->p_lock);
+                                       mutex_enter(parent1->p_lock);
+                               }
+                       } else if (parent1->p_lock > p2->p_lock) {
+                               mutex_enter(parent1->p_lock);
+                       }
+                       parent1->p_slflag |= PSL_CHTRACED;
+                       proc_reparent(p2, p1->p_pptr);
+                       if (parent1->p_lock != p2->p_lock)
+                               mutex_exit(parent1->p_lock);
+               }
+
+               /*
+                * Set ptrace status.
+                */
+               p1->p_fpid = p2->p_pid;
+               p2->p_fpid = p1->p_pid;
+       }
+
        LIST_INSERT_AFTER(p1, p2, p_pglist);
        LIST_INSERT_HEAD(&allproc, p2, p_list);
 
@@ -538,6 +569,17 @@
        while (p2->p_lflag & PL_PPWAIT)
                cv_wait(&p1->p_waitcv, proc_lock);
 
+        /*      
+         * Let the parent know that we are tracing its child.
+         */     
+       if (tracefork) {
+               ksiginfo_t ksi;
+                KSI_INIT_EMPTY(&ksi);
+                ksi.ksi_signo = SIGTRAP;
+                ksi.ksi_lid = l1->l_lid; 
+                kpsignal(p1, &ksi, NULL);
+       }
+
        mutex_exit(proc_lock);
 
        /*