Add a facility to disable processing page faults. When activated,

uiomove generates EFAULT if any accessed address is not mapped, as
opposed to handling the fault.

Sponsored by:	The FreeBSD Foundation
Reviewed by:	alc (previous version)

2 files changed, 18 insertions, 0 deletions

diff --git a/sys/vm/vm_extern.h b/sys/vm/vm_extern.h
index ae8e578..548cdb4 100644
--- a/sys/vm/vm_extern.h
+++ b/sys/vm/vm_extern.h
@@ -61,6 +61,8 @@ int useracc(void *, int, int);
 int vm_fault(vm_map_t, vm_offset_t, vm_prot_t, int);
 void vm_fault_copy_entry(vm_map_t, vm_map_t, vm_map_entry_t, vm_map_entry_t,
     vm_ooffset_t *);
+int vm_fault_disable_pagefaults(void);
+void vm_fault_enable_pagefaults(int save);
 int vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
     int fault_flags, vm_page_t *m_hold);
 int vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index 55abe86..eeb10a4 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -209,6 +209,8 @@ vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
     int fault_flags)
 {
 
+	if ((curthread->td_pflags & TDP_NOFAULTING) != 0)
+		return (KERN_PROTECTION_FAILURE);
 	return (vm_fault_hold(map, vaddr, fault_type, fault_flags, NULL));
 }
 
@@ -1475,3 +1477,17 @@ vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
 	/* return number of pages */
 	return i;
 }
+
+int
+vm_fault_disable_pagefaults(void)
+{
+
+	return (curthread_pflags_set(TDP_NOFAULTING));
+}
+
+void
+vm_fault_enable_pagefaults(int save)
+{
+
+	curthread_pflags_restore(save);
+}