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/* Fault-safe copy into or out of pager-backed memory.
Copyright (C) 1996,97,99,2000,2001 Free Software Foundation, Inc.
Written by Roland McGrath.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include "pager.h"
#include <sys/mman.h>
#include <hurd/sigpreempt.h>
#include <assert.h>
#include <string.h>
/* Try to copy *SIZE bytes between the region OTHER points to
and the region at OFFSET in the pager indicated by PAGER and MEMOBJ.
If PROT is VM_PROT_READ, copying is from the pager to OTHER;
if PROT contains VM_PROT_WRITE, copying is from OTHER into the pager.
*SIZE is always filled in the actual number of bytes successfully copied.
Returns an error code if the pager-backed memory faults;
if there is no fault, returns 0 and *SIZE will be unchanged. */
error_t
pager_memcpy (struct pager *pager, memory_object_t memobj,
vm_offset_t offset, void *other, size_t *size,
vm_prot_t prot)
{
vm_address_t window = 0;
vm_size_t windowsize = 8 * vm_page_size;
size_t to_copy = *size;
error_t err;
error_t copy (struct hurd_signal_preemptor *preemptor)
{
while (to_copy > 0)
{
size_t pageoff = offset & (vm_page_size - 1);
if (window)
/* Deallocate the old window. */
munmap ((caddr_t) window, windowsize);
/* Map in and copy a standard-sized window, unless that is
more than the total left to be copied. */
if (windowsize > pageoff + to_copy)
windowsize = pageoff + to_copy;
window = 0;
err = vm_map (mach_task_self (), &window, windowsize, 0, 1,
memobj, offset - pageoff, 0,
prot, prot, VM_INHERIT_NONE);
if (err)
return 0;
/* Realign the fault preemptor for the new mapping window. */
preemptor->first = window;
preemptor->last = window + windowsize;
if (prot == VM_PROT_READ)
memcpy (other, (const void *) window + pageoff,
windowsize - pageoff);
else
memcpy ((void *) window + pageoff, other, windowsize - pageoff);
offset += windowsize - pageoff;
other += windowsize - pageoff;
to_copy -= windowsize - pageoff;
}
return 0;
}
jmp_buf buf;
void fault (int signo, long int sigcode, struct sigcontext *scp)
{
assert (scp->sc_error == EKERN_MEMORY_ERROR);
err = pager_get_error (pager, sigcode - window + offset);
to_copy -= sigcode - window;
longjmp (buf, 1);
}
if (to_copy == 0)
/* Short-circuit return if nothing to do.
ERR would not be initialized by the copy loop in this case. */
return 0;
if (setjmp (buf) == 0)
hurd_catch_signal (sigmask (SIGSEGV) | sigmask (SIGBUS),
window, window + windowsize,
©, (sighandler_t) &fault);
if (window)
munmap ((caddr_t) window, windowsize);
*size -= to_copy;
return err;
}
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