[src/trunk]: src/sys/uvm use maximum-size fixed size array instead of variabl...

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

details:   https://anonhg.NetBSD.org/src/rev/e8cf415e5283
branches:  trunk
changeset: 935121:e8cf415e5283
user:      jdolecek <jdolecek%NetBSD.org@localhost>
date:      Thu Jun 25 09:58:44 2020 +0000

description:
use maximum-size fixed size array instead of variable-length array
in uvm_aio_aiodone() so that the stack usage can be determined and
checked in compile time; this is not called recursively not
particularly deep in call stack, so there is no need to save every
last drop of stack space here

diffstat:

 sys/uvm/uvm_pager.c |  12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diffs (41 lines):

diff -r 435f53571871 -r e8cf415e5283 sys/uvm/uvm_pager.c
--- a/sys/uvm/uvm_pager.c       Thu Jun 25 09:48:29 2020 +0000
+++ b/sys/uvm/uvm_pager.c       Thu Jun 25 09:58:44 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_pager.c,v 1.125 2020/04/19 21:53:38 ad Exp $       */
+/*     $NetBSD: uvm_pager.c,v 1.126 2020/06/25 09:58:44 jdolecek Exp $ */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_pager.c,v 1.125 2020/04/19 21:53:38 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_pager.c,v 1.126 2020/06/25 09:58:44 jdolecek Exp $");
 
 #include "opt_uvmhist.h"
 #include "opt_readahead.h"
@@ -516,17 +516,19 @@
  * uvm_aio_aiodone: do iodone processing for async i/os.
  * this should be called in thread context, not interrupt context.
  */
-
 void
 uvm_aio_aiodone(struct buf *bp)
 {
-       int npages = bp->b_bufsize >> PAGE_SHIFT;
-       struct vm_page *pgs[npages];
+       const int npages = bp->b_bufsize >> PAGE_SHIFT;
+       struct vm_page *pgs[howmany(MAXPHYS, MIN_PAGE_SIZE)];
        int i, error;
        bool write;
        UVMHIST_FUNC("uvm_aio_aiodone"); UVMHIST_CALLED(ubchist);
        UVMHIST_LOG(ubchist, "bp %#jx", (uintptr_t)bp, 0,0,0);
 
+       KASSERT(bp->b_bufsize <= MAXPHYS);
+       KASSERT(npages <= __arraycount(pgs));
+
        error = bp->b_error;
        write = (bp->b_flags & B_READ) == 0;