[patch] Fix Hurd's kill(pgid, sig)

[Guillem Jover]

Hi,

Long time ago, while porting sysvinit I found that kill(-1, SIGTERM),
was making the system die painfuly. The problem is that kill sends a
signal to all processes in the system, and that includes proc, auth,
and the root fs, also init itself and the kernel. POSIX states that
when calling kill with a pid == 0 or negative you can exclude system
processes from being sent the signal.

Marcus wrote an entry on Savannah's task tracker (3731). And I've done
an implementation now (although, I've not built or tested it).

So before getting the hurd, glibc and the hurd built again, I'd like
to know if this is an acceptable solution (given that it adds a new
interface! ;), and we most probably would include it in Debian for
mass testing.

regards,
guillem


2006-02-10  Guillem Jover  <guillem@hadrons.org>

        * hurd/process.defs (proc_mark_essential): New routine definition.
        * hurd/process_request.defs (proc_mark_essential_request): New
        simpleroutine definition.
        * init/init.c (launch_core_servers): Mark auth, proc and fs servers
        as essential.
        (frob_kernel_process): Mark the kernel as essential.
        * proc/mgt.c (create_startup_proc): Mark init as essential.
        * proc/pgrp.c (S_proc_getpgrppids): Exclude essential system processes.
        (S_proc_mark_essential): New function.
        * proc/proc.h (struct proc): Add p_essential member.


Index: hurd/process.defs
===================================================================
RCS file: /sources/hurd/hurd/hurd/process.defs,v
retrieving revision 1.28
diff -u -r1.28 process.defs
--- hurd/process.defs   21 May 2002 23:07:16 -0000      1.28
+++ hurd/process.defs   10 Feb 2006 02:04:46 -0000
@@ -1,5 +1,5 @@
 /* Definitions for process server interface
-   Copyright (C) 1992,93,94,95,96,97,2001 Free Software Foundation
+   Copyright (C) 1992,93,94,95,96,97,2001,06 Free Software Foundation
 
 This file is part of the GNU Hurd.
 
@@ -364,3 +364,7 @@
        calling_process: process_t;
        target_process: pid_t;
        out tty: mach_port_send_t);
+
+/* Inform the process server that the process is essential.  */
+routine proc_mark_essential (
+       process: process_t);
Index: hurd/process_request.defs
===================================================================
RCS file: /sources/hurd/hurd/hurd/process_request.defs,v
retrieving revision 1.3
diff -u -r1.3 process_request.defs
--- hurd/process_request.defs   24 Jul 1998 23:39:10 -0000      1.3
+++ hurd/process_request.defs   10 Feb 2006 02:04:46 -0000
@@ -1,6 +1,6 @@
 /* Definitions for process server interface (request-only version)
 
-   Copyright (C) 1992, 93, 94, 95, 96, 98 Free Software Foundation, Inc.
+   Copyright (C) 1992, 93, 94, 95, 96, 98, 2006 Free Software Foundation, Inc.
 
 This file is part of the GNU Hurd.
 
@@ -365,3 +365,8 @@
        process: process_t;
        ureplyport reply: reply_port_t;
        pid: pid_t);
+
+/* Inform the process server that the process is essential.  */
+simpleroutine proc_mark_essential_request (
+       process: process_t;
+       ureplyport reply: reply_port_t);
Index: init/init.c
===================================================================
RCS file: /sources/hurd/hurd/init/init.c,v
retrieving revision 1.130
diff -u -r1.130 init.c
--- init/init.c 24 Feb 2005 01:48:44 -0000      1.130
+++ init/init.c 10 Feb 2006 02:04:46 -0000
@@ -1,6 +1,6 @@
 /* Start and maintain hurd core servers and system run state
 
-   Copyright (C) 1993,94,95,96,97,98,99,2000,01,02
+   Copyright (C) 1993,94,95,96,97,98,99,2000,01,02,06
        Free Software Foundation, Inc.
    This file is part of the GNU Hurd.
 
@@ -649,6 +649,7 @@
   proc_child (procserver, authtask);
 
   proc_task2proc (procserver, authtask, &authproc);
+  proc_mark_essential (authproc);
   proc_mark_exec (authproc);
   startup_authinit_reply (authreply, authreplytype, 0, authproc,
                          MACH_MSG_TYPE_COPY_SEND);
@@ -671,6 +672,7 @@
   err = proc_task2proc (procserver, proctask, &procproc);
   if (!err)
     {
+      proc_mark_essential (procproc);
       proc_mark_exec (procproc);
       mach_port_deallocate (mach_task_self (), procproc);
     }
@@ -680,6 +682,7 @@
   /* Get the bootstrap filesystem's proc server port.
      We must do this before calling proc_setmsgport below.  */
   proc_task2proc (procserver, fstask, &fsproc);
+  proc_mark_essential (fsproc);
   proc_mark_exec (fsproc);
 
 #if 0
@@ -784,8 +787,10 @@
       return;
     }
 
-  /* Mark the kernel task as an essential task so that we never
-     want to task_terminate it.  */
+  /* Mark the kernel task as an essential task so that we or the proc server
+     never want to task_terminate it.  */
+  proc_mark_essential (proc);
+
   err = record_essential_task ("kernel", task);
   assert_perror (err);
 
Index: proc/mgt.c
===================================================================
RCS file: /sources/hurd/hurd/proc/mgt.c,v
retrieving revision 1.67
diff -u -r1.67 mgt.c
--- proc/mgt.c  16 Aug 2003 22:19:37 -0000      1.67
+++ proc/mgt.c  10 Feb 2006 02:04:47 -0000
@@ -1,5 +1,6 @@
 /* Process management
-   Copyright (C) 1992,93,94,95,96,99,2000,01,02 Free Software Foundation, Inc.
+   Copyright (C) 1992,93,94,95,96,99,2000,01,02,06
+       Free Software Foundation, Inc.
 
 This file is part of the GNU Hurd.
 
@@ -592,6 +593,8 @@
 
   p->p_deadmsg = 1;            /* Force initial "re-"fetch of msgport.  */
 
+  p->p_essential = 1;
+
   p->p_noowner = 0;
   p->p_id = make_ids (&zero, 1);
   assert (p->p_id);
Index: proc/pgrp.c
===================================================================
RCS file: /sources/hurd/hurd/proc/pgrp.c,v
retrieving revision 1.23
diff -u -r1.23 pgrp.c
--- proc/pgrp.c 8 May 2002 09:24:52 -0000       1.23
+++ proc/pgrp.c 10 Feb 2006 02:04:47 -0000
@@ -1,5 +1,5 @@
 /* Session and process group manipulation
-   Copyright (C) 1992,93,94,95,96,99,2001,02 Free Software Foundation, Inc.
+   Copyright (C) 1992,93,94,95,96,99,2001,02,06 Free Software Foundation, Inc.
 
 This file is part of the GNU Hurd.
 
@@ -265,7 +265,7 @@
 
   count = 0;
   for (p = pg->pg_plist; p; p = p->p_gnext)
-    if (++count <= npids)
+    if (++count <= npids && !p->p_essential)
       *pp++ = p->p_pid;
 
   if (count > npids)
@@ -278,7 +278,8 @@
 
       pp = *pids;
       for (p = pg->pg_plist; p; p = p->p_gnext)
-       *pp++ = p->p_pid;
+       if (!p->p_essential)
+         *pp++ = p->p_pid;
       /* Dealloc ? XXX */
     }
   *npidsp = count;
@@ -380,6 +381,16 @@
   return 0;
 }
 
+/* Implement proc_mark_essential as described in <hurd/process.defs>. */
+kern_return_t
+S_proc_mark_essential (struct proc *p)
+{
+  if (!p)
+    return EOPNOTSUPP;
+  p->p_essential = 1;
+  return 0;
+}
+
 /* Make process P no longer a member of its process group.
    Note that every process is always a member of some process group;
    this must be followed by setting P->p_pgrp and then calling
Index: proc/proc.h
===================================================================
RCS file: /sources/hurd/hurd/proc/proc.h,v
retrieving revision 1.28
diff -u -r1.28 proc.h
--- proc/proc.h 1 Mar 2004 09:58:44 -0000       1.28
+++ proc/proc.h 10 Feb 2006 02:04:47 -0000
@@ -1,5 +1,5 @@
 /* Process server definitions
-   Copyright (C) 1992,93,94,95,96,99,2000,01 Free Software Foundation, Inc.
+   Copyright (C) 1992,93,94,95,96,99,2000,01,06 Free Software Foundation, Inc.
 
 This file is part of the GNU Hurd.
 
@@ -84,6 +84,7 @@
   unsigned int p_noowner:1;    /* has no owner known */
   unsigned int p_loginleader:1;        /* leader of login collection */
   unsigned int p_dead:1;       /* process is dead */
+  unsigned int p_essential:1;  /* has called proc_mark_essential */
 };
 
 typedef struct proc *pstruct_t;