Author: kib
Date: Fri Jan 2 01:05:08 2015
New Revision: 276523
URL: https://svnweb.freebsd.org/changeset/base/276523
Log:
Callers of pmap_kextract() cannot distinguish between failure and
physical address zero. Assume that the lowest page is always mapped
by direct map.
This restores access to the page at zero through /dev/mem after
r263475.
Reported and tested by: neel
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Modified:
head/sys/amd64/amd64/mem.c
Modified: head/sys/amd64/amd64/mem.c
==============================================================================
--- head/sys/amd64/amd64/mem.c Fri Jan 2 01:00:38 2015 (r276522)
+++ head/sys/amd64/amd64/mem.c Fri Jan 2 01:05:08 2015 (r276523)
@@ -77,7 +77,7 @@ int
memrw(struct cdev *dev, struct uio *uio, int flags)
{
struct iovec *iov;
- u_long c, v;
+ u_long c, v, vd;
int error, o, sflags;
vm_offset_t addr, eaddr;
@@ -98,15 +98,15 @@ memrw(struct cdev *dev, struct uio *uio,
kmemphys:
o = v & PAGE_MASK;
c = min(uio->uio_resid, (u_int)(PAGE_SIZE - o));
- v = PHYS_TO_DMAP(v);
- if (v < DMAP_MIN_ADDRESS ||
- (v > DMAP_MIN_ADDRESS + dmaplimit &&
- v <= DMAP_MAX_ADDRESS) ||
- pmap_kextract(v) == 0) {
+ vd = PHYS_TO_DMAP(v);
+ if (vd < DMAP_MIN_ADDRESS ||
+ (vd > DMAP_MIN_ADDRESS + dmaplimit &&
+ vd <= DMAP_MAX_ADDRESS) ||
+ (pmap_kextract(vd) == 0 && (v & PG_FRAME) != 0)) {
error = EFAULT;
goto ret;
}
- error = uiomove((void *)v, (int)c, uio);
+ error = uiomove((void *)vd, (int)c, uio);
continue;
} else if (dev2unit(dev) == CDEV_MINOR_KMEM) {
v = uio->uio_offset;
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