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Fix race conditions.

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Tested by:	kris@
MFC after:      3 days
This commit is contained in:
Stephan Uphoff 2006-01-23 15:46:09 +00:00
parent 2eff8c6814
commit 3753c2c3f1
1 changed files with 57 additions and 33 deletions
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90
sys/i386/i386/mem.c
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@ -53,6 +53,7 @@ __FBSDID("$FreeBSD$");
#include <sys/memrange.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/sx.h>
#include <sys/proc.h>
#include <sys/signalvar.h>
#include <sys/systm.h>
@ -71,18 +72,37 @@ __FBSDID("$FreeBSD$");
*/
MALLOC_DEFINE(M_MEMDESC, "memdesc", "memory range descriptors");
static struct sx memsxlock;
SX_SYSINIT(memsxlockinit, &memsxlock, "/dev/mem lock");
/* ARGSUSED */
int
memrw(struct cdev *dev, struct uio *uio, int flags)
{
int o;
u_int c = 0, v;
u_int c = 0;
vm_paddr_t pa;
struct iovec *iov;
int error = 0;
vm_offset_t addr, eaddr;
vm_offset_t addr;
/* XXX UPS Why ? */
GIANT_REQUIRED;
if (minor(dev) != CDEV_MINOR_MEM && minor(dev) != CDEV_MINOR_KMEM)
return EIO;
if ( minor(dev) == CDEV_MINOR_KMEM && uio->uio_resid > 0) {
if (uio->uio_offset < (vm_offset_t)VADDR(PTDPTDI, 0))
return (EFAULT);
if (!kernacc((caddr_t)(int)uio->uio_offset, uio->uio_resid,
uio->uio_rw == UIO_READ ? VM_PROT_READ : VM_PROT_WRITE))
return (EFAULT);
}
while (uio->uio_resid > 0 && error == 0) {
iov = uio->uio_iov;
if (iov->iov_len == 0) {
@ -93,43 +113,47 @@ memrw(struct cdev *dev, struct uio *uio, int flags)
continue;
}
if (minor(dev) == CDEV_MINOR_MEM) {
v = uio->uio_offset;
v &= ~PAGE_MASK;
pmap_kenter((vm_offset_t)ptvmmap, v);
o = (int)uio->uio_offset & PAGE_MASK;
c = (u_int)(PAGE_SIZE - ((int)iov->iov_base & PAGE_MASK));
c = min(c, (u_int)(PAGE_SIZE - o));
c = min(c, (u_int)iov->iov_len);
error = uiomove((caddr_t)&ptvmmap[o], (int)c, uio);
pmap_qremove((vm_offset_t)ptvmmap, 1);
continue;
}
else if (minor(dev) == CDEV_MINOR_KMEM) {
c = iov->iov_len;
pa = uio->uio_offset;
pa &= ~PAGE_MASK;
} else {
/*
* Make sure that all of the pages are currently
* resident so that we don't create any zero-fill
* pages.
* Extract the physical page since the mapping may
* change at any time. This avoids panics on page
* fault in this case but will cause reading/writing
* to the wrong page.
* Hopefully an application will notice the wrong
* data on read access and refrain from writing.
* This should be replaced by a special uiomove
* type function that just returns an error if there
* is a page fault on a kernel page.
*/
addr = trunc_page(uio->uio_offset);
eaddr = round_page(uio->uio_offset + c);
pa = pmap_extract(kernel_pmap, addr);
if (pa == 0)
return EFAULT;
if (addr < (vm_offset_t)VADDR(PTDPTDI, 0))
return (EFAULT);
for (; addr < eaddr; addr += PAGE_SIZE)
if (pmap_extract(kernel_pmap, addr) == 0)
return (EFAULT);
if (!kernacc((caddr_t)(int)uio->uio_offset, c,
uio->uio_rw == UIO_READ ?
VM_PROT_READ : VM_PROT_WRITE))
return (EFAULT);
error = uiomove((caddr_t)(int)uio->uio_offset, (int)c, uio);
continue;
}
/* else panic! */
/*
* XXX UPS This should just use sf_buf_alloc.
* Unfortunately sf_buf_alloc needs a vm_page
* and we may want to look at memory not covered
* by the page array.
*/
sx_xlock(&memsxlock);
pmap_kenter((vm_offset_t)ptvmmap, pa);
pmap_invalidate_page(kernel_pmap,(vm_offset_t)ptvmmap);
o = (int)uio->uio_offset & PAGE_MASK;
c = PAGE_SIZE - o;
c = min(c, (u_int)iov->iov_len);
error = uiomove((caddr_t)&ptvmmap[o], (int)c, uio);
pmap_qremove((vm_offset_t)ptvmmap, 1);
sx_xunlock(&memsxlock);
}
return (error);
}