Add new mmap(2) flags to permit applications to request specific virtual

address alignment of mappings.
- MAP_ALIGNED(n) requests a mapping aligned on a boundary of (1 << n).
  Requests for n >= number of bits in a pointer or less than the size of
  a page fail with EINVAL.  This matches the API provided by NetBSD.
- MAP_ALIGNED_SUPER is a special case of MAP_ALIGNED.  It can be used
  to optimize the chances of using large pages.  By default it will align
  the mapping on a large page boundary (the system is free to choose any
  large page size to align to that seems best for the mapping request).
  However, if the object being mapped is already using large pages, then
  it will align the virtual mapping to match the existing large pages in
  the object instead.
- Internally, VMFS_ALIGNED_SPACE is now renamed to VMFS_SUPER_SPACE, and
  VMFS_ALIGNED_SPACE(n) is repurposed for specifying a specific alignment.
  MAP_ALIGNED(n) maps to using VMFS_ALIGNED_SPACE(n), while
  MAP_ALIGNED_SUPER maps to VMFS_SUPER_SPACE.
- mmap() of a device object now uses VMFS_OPTIMAL_SPACE rather than
  explicitly using VMFS_SUPER_SPACE.  All device objects are forced to
  use a specific color on creation, so VMFS_OPTIMAL_SPACE is effectively
  equivalent.

Reviewed by:	alc
MFC after:	1 month

1 files changed, 20 insertions, 8 deletions

diff --git a/sys/vm/vm_mmap.c b/sys/vm/vm_mmap.c
index 1b08097..53a7be5 100644
--- a/sys/vm/vm_mmap.c
+++ b/sys/vm/vm_mmap.c
@@ -201,7 +201,7 @@ sys_mmap(td, uap)
 	vm_prot_t cap_maxprot, prot, maxprot;
 	void *handle;
 	objtype_t handle_type;
-	int flags, error;
+	int align, error, flags;
 	off_t pos;
 	struct vmspace *vms = td->td_proc->p_vmspace;
 	cap_rights_t rights;
@@ -251,6 +251,13 @@ sys_mmap(td, uap)
 	size += pageoff;			/* low end... */
 	size = (vm_size_t) round_page(size);	/* hi end */
 
+	/* Ensure alignment is at least a page and fits in a pointer. */
+	align = flags & MAP_ALIGNMENT_MASK;
+	if (align != 0 && align != MAP_ALIGNED_SUPER &&
+	    (align >> MAP_ALIGNMENT_SHIFT >= sizeof(void *) * NBBY ||
+	    align >> MAP_ALIGNMENT_SHIFT < PAGE_SHIFT))
+		return (EINVAL);
+
 	/*
 	 * Check for illegal addresses.  Watch out for address wrap... Note
 	 * that VM_*_ADDRESS are not constants due to casts (argh).
@@ -1490,7 +1497,7 @@ vm_mmap(vm_map_t map, vm_offset_t *addr, vm_size_t size, vm_prot_t prot,
 	boolean_t fitit;
 	vm_object_t object = NULL;
 	struct thread *td = curthread;
-	int docow, error, rv;
+	int docow, error, findspace, rv;
 	boolean_t writecounted;
 
 	if (size == 0)
@@ -1605,12 +1612,17 @@ vm_mmap(vm_map_t map, vm_offset_t *addr, vm_size_t size, vm_prot_t prot,
 	if (flags & MAP_STACK)
 		rv = vm_map_stack(map, *addr, size, prot, maxprot,
 		    docow | MAP_STACK_GROWS_DOWN);
-	else if (fitit)
-		rv = vm_map_find(map, object, foff, addr, size,
-		    object != NULL && object->type == OBJT_DEVICE ?
-		    VMFS_ALIGNED_SPACE : VMFS_OPTIMAL_SPACE, prot, maxprot,
-		    docow);
-	else
+	else if (fitit) {
+		if ((flags & MAP_ALIGNMENT_MASK) == MAP_ALIGNED_SUPER)
+			findspace = VMFS_SUPER_SPACE;
+		else if ((flags & MAP_ALIGNMENT_MASK) != 0)
+			findspace = VMFS_ALIGNED_SPACE(flags >>
+			    MAP_ALIGNMENT_SHIFT);
+		else
+			findspace = VMFS_OPTIMAL_SPACE;
+		rv = vm_map_find(map, object, foff, addr, size, findspace,
+		    prot, maxprot, docow);
+	} else
 		rv = vm_map_fixed(map, object, foff, *addr, size,
 				 prot, maxprot, docow);