[src/trunk]: src/sys PR# kern/45312: ptrace: PT_SETREGS can't alter system calls

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

details:   https://anonhg.NetBSD.org/src/rev/d359d66ee4b1
branches:  trunk
changeset: 769129:d359d66ee4b1
user:      jmcneill <jmcneill%NetBSD.org@localhost>
date:      Wed Aug 31 22:58:39 2011 +0000

description:
PR# kern/45312: ptrace: PT_SETREGS can't alter system calls

Add a new PT_SYSCALLEMU request that cancels the current syscall, for
use with PT_SYSCALL.

diffstat:

 sys/kern/kern_subr.c   |  16 ++++++++++++----
 sys/kern/sys_process.c |  15 +++++++++++++--
 sys/sys/proc.h         |   3 ++-
 sys/sys/ptrace.h       |   3 ++-
 4 files changed, 29 insertions(+), 8 deletions(-)

diffs (137 lines):

diff -r d647c5661a79 -r d359d66ee4b1 sys/kern/kern_subr.c
--- a/sys/kern/kern_subr.c      Wed Aug 31 22:43:19 2011 +0000
+++ b/sys/kern/kern_subr.c      Wed Aug 31 22:58:39 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_subr.c,v 1.209 2011/07/27 14:35:34 uebayasi Exp $ */
+/*     $NetBSD: kern_subr.c,v 1.210 2011/08/31 22:58:39 jmcneill Exp $ */
 
 /*-
  * Copyright (c) 1997, 1998, 1999, 2002, 2007, 2008 The NetBSD Foundation, Inc.
@@ -79,7 +79,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_subr.c,v 1.209 2011/07/27 14:35:34 uebayasi Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_subr.c,v 1.210 2011/08/31 22:58:39 jmcneill Exp $");
 
 #include "opt_ddb.h"
 #include "opt_md.h"
@@ -686,6 +686,8 @@
 int
 trace_enter(register_t code, const register_t *args, int narg)
 {
+       int error = 0;
+
 #ifdef SYSCALL_DEBUG
        scdebug_call(code, args);
 #endif /* SYSCALL_DEBUG */
@@ -694,10 +696,16 @@
 
 #ifdef PTRACE
        if ((curlwp->l_proc->p_slflag & (PSL_SYSCALL|PSL_TRACED)) ==
-           (PSL_SYSCALL|PSL_TRACED))
+           (PSL_SYSCALL|PSL_TRACED)) {
                process_stoptrace();
+               if (curlwp->l_proc->p_slflag & PSL_SYSCALLEMU) {
+                       /* tracer will emulate syscall for us */
+                       error = EJUSTRETURN;
+                       CLR(curlwp->l_proc->p_slflag, PSL_SYSCALLEMU);
+               }
+       }
 #endif
-       return 0;
+       return error;
 }
 
 /*
diff -r d647c5661a79 -r d359d66ee4b1 sys/kern/sys_process.c
--- a/sys/kern/sys_process.c    Wed Aug 31 22:43:19 2011 +0000
+++ b/sys/kern/sys_process.c    Wed Aug 31 22:58:39 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_process.c,v 1.159 2011/08/30 22:45:55 christos Exp $       */
+/*     $NetBSD: sys_process.c,v 1.160 2011/08/31 22:58:39 jmcneill Exp $       */
 
 /*-
  * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@@ -118,7 +118,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_process.c,v 1.159 2011/08/30 22:45:55 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_process.c,v 1.160 2011/08/31 22:58:39 jmcneill Exp $");
 
 #include "opt_ptrace.h"
 #include "opt_ktrace.h"
@@ -195,6 +195,7 @@
        case PT_DETACH:
        case PT_LWPINFO:
        case PT_SYSCALL:
+       case PT_SYSCALLEMU:
        case PT_DUMPCORE:
                result = KAUTH_RESULT_ALLOW;
                break;
@@ -370,6 +371,7 @@
        case  PT_DETACH:
        case  PT_LWPINFO:
        case  PT_SYSCALL:
+       case  PT_SYSCALLEMU:
        case  PT_DUMPCORE:
 #ifdef PT_STEP
        case  PT_STEP:
@@ -453,6 +455,7 @@
        case PT_DETACH:
        case PT_KILL:
        case PT_SYSCALL:
+       case PT_SYSCALLEMU:
        case PT_ATTACH:
        case PT_TRACE_ME:
                pheld = 1;
@@ -714,6 +717,14 @@
                }
                break;
 
+       case  PT_SYSCALLEMU:
+               if (!ISSET(t->p_slflag, PSL_SYSCALL) || t->p_stat != SSTOP) {
+                       error = EINVAL;
+                       break;
+               }
+               SET(t->p_slflag, PSL_SYSCALLEMU);
+               break;
+
        case  PT_KILL:
                /* just send the process a KILL signal. */
                signo = SIGKILL;
diff -r d647c5661a79 -r d359d66ee4b1 sys/sys/proc.h
--- a/sys/sys/proc.h    Wed Aug 31 22:43:19 2011 +0000
+++ b/sys/sys/proc.h    Wed Aug 31 22:58:39 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: proc.h,v 1.308 2011/07/27 13:20:07 uebayasi Exp $      */
+/*     $NetBSD: proc.h,v 1.309 2011/08/31 22:58:39 jmcneill Exp $      */
 
 /*-
  * Copyright (c) 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -378,6 +378,7 @@
 #define        PSL_FSTRACE     0x00010000 /* Debugger process being traced by procfs */
 #define        PSL_CHTRACED    0x00400000 /* Child has been traced & reparented */
 #define        PSL_SYSCALL     0x04000000 /* process has PT_SYSCALL enabled */
+#define        PSL_SYSCALLEMU  0x08000000 /* cancel in-progress syscall */
 
 /*
  * Kept in p_stflag and protected by p_stmutex.
diff -r d647c5661a79 -r d359d66ee4b1 sys/sys/ptrace.h
--- a/sys/sys/ptrace.h  Wed Aug 31 22:43:19 2011 +0000
+++ b/sys/sys/ptrace.h  Wed Aug 31 22:58:39 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ptrace.h,v 1.42 2009/12/14 00:48:35 matt Exp $ */
+/*     $NetBSD: ptrace.h,v 1.43 2011/08/31 22:58:39 jmcneill Exp $     */
 
 /*-
  * Copyright (c) 1984, 1993
@@ -47,6 +47,7 @@
 #define        PT_DUMPCORE     12      /* make the child generate a core dump */
 #define        PT_LWPINFO      13      /* get info about the LWP */
 #define        PT_SYSCALL      14      /* stop on syscall entry/exit */
+#define        PT_SYSCALLEMU   15      /* cancel syscall, tracer will emulate it */
 #define        PT_FIRSTMACH    32      /* for machine-specific requests */
 #include <machine/ptrace.h>    /* machine-specific requests, if any */