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Ensure that _tmppt KVA is used exclusively by providing exclusive sx

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lock around the mapping and uiomove().  Before r277643, it was
partially protected by Giant (but potential sleeping in fault from
uiomove() would still allow other thread to reuse the mapping).

Noted by:	ian
Reviewed by:	alc, ian
Sponsored by:	The FreeBSD Foundation
MFC after:	3 weeks
This commit is contained in:
Konstantin Belousov 2015-01-26 10:11:55 +00:00
parent 7fdb2b7a8d
commit ad87de1c87
1 changed files with 6 additions and 0 deletions
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6
sys/arm/arm/mem.c
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@ -55,6 +55,7 @@ __FBSDID("$FreeBSD$");
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/signalvar.h>
#include <sys/sx.h>
#include <sys/systm.h>
#include <sys/uio.h>
@ -72,6 +73,9 @@ MALLOC_DEFINE(M_MEMDESC, "memdesc", "memory range descriptors");
struct mem_range_softc mem_range_softc;
static struct sx tmppt_lock;
SX_SYSINIT(tmppt, &tmppt_lock, "mem4map");
/* ARGSUSED */
int
memrw(struct cdev *dev, struct uio *uio, int flags)
@ -107,6 +111,7 @@ memrw(struct cdev *dev, struct uio *uio, int flags)
}
if (!address_valid)
return (EINVAL);
sx_xlock(&tmppt_lock);
pmap_kenter((vm_offset_t)_tmppt, v);
o = (int)uio->uio_offset & PAGE_MASK;
c = (u_int)(PAGE_SIZE - ((int)iov->iov_base & PAGE_MASK));
@ -114,6 +119,7 @@ memrw(struct cdev *dev, struct uio *uio, int flags)
c = min(c, (u_int)iov->iov_len);
error = uiomove((caddr_t)&_tmppt[o], (int)c, uio);
pmap_qremove((vm_offset_t)_tmppt, 1);
sx_xunlock(&tmppt_lock);
continue;
}
else if (dev2unit(dev) == CDEV_MINOR_KMEM) {