PERFORCE change 68938 for review

[John Baldwin]

http://perforce.freebsd.org/chv.cgi?CH=68938

Change 68938 by jhb at jhb_slimer on 2005/01/13 21:06:03

	cpu_exit() cleaning inspired by sparc64 use-after-free bug:
	- Remove stale comment (alpha, powerpc)
	- Drop redundant dbregs drop (i386, amd64)
	- Note that fp state should probably be per thread (alpha, ia64)

Affected files ...

.. //depot/projects/smpng/sys/alpha/alpha/vm_machdep.c#37 edit
.. //depot/projects/smpng/sys/amd64/amd64/vm_machdep.c#22 edit
.. //depot/projects/smpng/sys/i386/i386/vm_machdep.c#59 edit
.. //depot/projects/smpng/sys/ia64/ia64/vm_machdep.c#44 edit
.. //depot/projects/smpng/sys/powerpc/powerpc/vm_machdep.c#40 edit

Differences ...

==== //depot/projects/smpng/sys/alpha/alpha/vm_machdep.c#37 (text+ko) ====

@@ -224,17 +224,15 @@
 	td->td_pcb->pcb_context[2] = (u_long) arg;
 }
 
-/*
- * cpu_exit is called as the last action during exit.
- * We release the address space of the process, block interrupts,
- * and call switch_exit.  switch_exit switches to proc0's PCB and stack,
- * then jumps into the middle of cpu_switch, as if it were switching
- * from proc0.
- */
 void
 cpu_exit(struct thread *td)
 {
 
+	/*
+	 * XXX: Should this be in thread_exit instead?  If so,
+	 * alpha_fpstate_save() should be in cpu_set_upcall()
+	 * as well.
+	 */
 	alpha_fpstate_drop(td);
 }
 

==== //depot/projects/smpng/sys/amd64/amd64/vm_machdep.c#22 (text+ko) ====

@@ -185,13 +185,6 @@
 void
 cpu_exit(struct thread *td)
 {
-	struct pcb *pcb = td->td_pcb;
-
-	if (pcb->pcb_flags & PCB_DBREGS) {
-		/* disable all hardware breakpoints */
-		reset_dbregs();
-		pcb->pcb_flags &= ~PCB_DBREGS;
-	}
 }
 
 void

==== //depot/projects/smpng/sys/i386/i386/vm_machdep.c#59 (text+ko) ====

@@ -295,8 +295,6 @@
 cpu_exit(struct thread *td)
 {
 	struct mdproc *mdp;
-	struct pcb *pcb = td->td_pcb; 
-
 
 	/* Reset pc->pcb_gs and %gs before possibly invalidating it. */
 	mdp = &td->td_proc->p_md;
@@ -307,18 +305,13 @@
 		user_ldt_free(td);
 	} else
 		mtx_unlock_spin(&sched_lock);
-
-	if (pcb->pcb_flags & PCB_DBREGS) {
-		/* disable all hardware breakpoints */
-		reset_dbregs();
-		pcb->pcb_flags &= ~PCB_DBREGS;
-	}
 }
 
 void
 cpu_thread_exit(struct thread *td)
 {
 	struct pcb *pcb = td->td_pcb; 
+
 #ifdef DEV_NPX
 	if (td == PCPU_GET(fpcurthread))
 		npxdrop();

==== //depot/projects/smpng/sys/ia64/ia64/vm_machdep.c#44 (text+ko) ====

@@ -297,6 +297,7 @@
 cpu_exit(struct thread *td)
 {
 
+	/* XXX: Should this be in cpu_thread_exit() instead? */
 	/* Throw away the high FP registers. */
 	ia64_highfp_drop(td);
 }

==== //depot/projects/smpng/sys/powerpc/powerpc/vm_machdep.c#40 (text+ko) ====

@@ -182,13 +182,6 @@
 	cf->cf_arg0 = (register_t)arg;
 }
 
-/*
- * cpu_exit is called as the last action during exit.
- * We release the address space of the process, block interrupts,
- * and call switch_exit.  switch_exit switches to proc0's PCB and stack,
- * then jumps into the middle of cpu_switch, as if it were switching
- * from proc0.
- */
 void
 cpu_exit(td)
 	register struct thread *td;