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uvm(9): Fix 19-year-old bug in assertion about mmap hint. 

Previously this would _first_ remember the original hint, and _then_
clamp the hint to the VM map's range:

	orig_hint = hint;
	if (hint < vm_map_min(map)) {	/* check ranges ... */
		if (flags & UVM_FLAG_FIXED) {
			UVMHIST_LOG(maphist,"<- VA below map range",0,0,0,0);
			return (NULL);
		}
		hint = vm_map_min(map);
	...
	KASSERTMSG(!topdown || hint <= orig_hint, "hint: %#jx, orig_hint: %#jx",
	    (uintmax_t)hint, (uintmax_t)orig_hint);

Even if nothing else happens in the ellipsis, taking the branch
guarantees the assertion will fail in the topdown case.
This commit is contained in:
riastradh 2022-06-04 20:54:24 +00:00
parent f8a9f49a15
commit 22753e6166
1 changed files with 13 additions and 7 deletions
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20
sys/uvm/uvm_map.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: uvm_map.c,v 1.394 2022/04/10 09:50:46 andvar Exp $ */
/* $NetBSD: uvm_map.c,v 1.395 2022/06/04 20:54:24 riastradh Exp $ */
/*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
@ -66,7 +66,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_map.c,v 1.394 2022/04/10 09:50:46 andvar Exp $");
__KERNEL_RCSID(0, "$NetBSD: uvm_map.c,v 1.395 2022/06/04 20:54:24 riastradh Exp $");
#include "opt_ddb.h"
#include "opt_pax.h"
@ -1813,12 +1813,17 @@ uvm_map_findspace(struct vm_map *map, vaddr_t hint, vsize_t length,
uvm_map_check(map, "map_findspace entry");
/*
* remember the original hint. if we are aligning, then we
* may have to try again with no alignment constraint if
* we fail the first time.
* Clamp the hint to the VM map's min/max address, and remmeber
* the clamped original hint. Remember the original hint,
* clamped to the min/max address. If we are aligning, then we
* may have to try again with no alignment constraint if we
* fail the first time.
*
* We use the original hint to verify later that the search has
* been monotonic -- that is, nonincreasing or nondecreasing,
* according to topdown or !topdown respectively. But the
* clamping is not monotonic.
*/
orig_hint = hint;
if (hint < vm_map_min(map)) { /* check ranges ... */
if (flags & UVM_FLAG_FIXED) {
UVMHIST_LOG(maphist,"<- VA below map range",0,0,0,0);
@ -1831,6 +1836,7 @@ uvm_map_findspace(struct vm_map *map, vaddr_t hint, vsize_t length,
hint, vm_map_min(map), vm_map_max(map), 0);
return (NULL);
}
orig_hint = hint;
UVMHIST_LOG(maphist,"<- VA %#jx vs range [%#jx->%#jx]",
hint, vm_map_min(map), vm_map_max(map), 0);