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/* Fault-safe copy into or out of pager-backed memory.
Copyright (C) 1996,97,99, 2000,01,02 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 "priv.h"
#include "pager.h"
#include <sys/mman.h>
#include <hurd/sigpreempt.h>
#include <assert.h>
#include <string.h>
/* Start using vm_copy over memcpy when we have that many page. This is
roughly the L1 cache size. (This value *cannot* be less than
vm_page_size.) */
#define VMCOPY_BETTER_THAN_MEMCPY (8*vm_page_size)
/* 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)
{
error_t err;
size_t n = *size;
#define VMCOPY_WINDOW_DEFAULT_SIZE (32 * vm_page_size)
#define MEMCPY_WINDOW_DEFAULT_SIZE (32 * vm_page_size)
vm_address_t window;
vm_size_t window_size;
error_t do_vm_copy (void)
{
assert ((offset & (vm_page_size - 1)) == 0);
assert (((vm_address_t) other & (vm_page_size - 1)) == 0);
assert (n >= vm_page_size);
do
{
window_size =
VMCOPY_WINDOW_DEFAULT_SIZE > n
? (n - (n & (vm_page_size - 1)))
: VMCOPY_WINDOW_DEFAULT_SIZE;
assert (window_size >= VMCOPY_BETTER_THAN_MEMCPY);
assert ((window_size & (vm_page_size - 1)) == 0);
window = 0;
err = vm_map (mach_task_self (), &window, window_size, 0, 1,
memobj, offset, 0, prot, prot, VM_INHERIT_NONE);
if (err)
return err;
if (prot == VM_PROT_READ)
err = vm_copy (mach_task_self (), window, window_size,
(vm_address_t) other);
else
err = vm_copy (mach_task_self (), (vm_address_t) other,
window_size, window);
vm_deallocate (mach_task_self (), window, window_size);
if (err)
return err;
other += window_size;
offset += window_size;
n -= window_size;
}
while (n >= VMCOPY_BETTER_THAN_MEMCPY);
return 0;
}
error_t do_copy (struct hurd_signal_preemptor *preemptor)
{
error_t do_memcpy (size_t to_copy)
{
window_size = MEMCPY_WINDOW_DEFAULT_SIZE;
do
{
size_t pageoff = offset & (vm_page_size - 1);
size_t copy_count = window_size - pageoff;
/* Map in and copy a standard-sized window, unless that is
more than the total left to be copied. */
if (window_size >= round_page (pageoff + to_copy))
{
copy_count = to_copy;
window_size = round_page (pageoff + to_copy);
}
window = 0;
err = vm_map (mach_task_self (), &window, window_size, 0, 1,
memobj, offset - pageoff, 0,
prot, prot, VM_INHERIT_NONE);
if (err)
return err;
/* Realign the fault preemptor for the new mapping window. */
preemptor->first = window;
preemptor->last = window + window_size;
if (prot == VM_PROT_READ)
memcpy (other, (const void *) window + pageoff, copy_count);
else
memcpy ((void *) window + pageoff, other, copy_count);
vm_deallocate (mach_task_self (), window, window_size);
offset += copy_count;
other += copy_count;
to_copy -= copy_count;
n -= copy_count;
assert (n >= 0);
assert (to_copy >= 0);
}
while (to_copy > 0);
return 0;
}
/* Can we use vm_copy? */
if ((((vm_address_t) other & (vm_page_size - 1))
== (offset & (vm_page_size - 1)))
&& (n >= (VMCOPY_BETTER_THAN_MEMCPY + vm_page_size
- ((vm_address_t) other & (vm_page_size - 1)))))
/* 1) other and offset are aligned with repect to each other;
and 2) we have at least VMCOPY_BETTER_THAN_MEMCPY fully
aligned pages. */
{
err = do_memcpy (vm_page_size
- ((vm_address_t) other & (vm_page_size - 1)));
if (err)
return err;
assert (n >= VMCOPY_BETTER_THAN_MEMCPY);
err = do_vm_copy ();
if (err || n == 0)
/* We failed or we finished. */
return err;
assert (n < VMCOPY_BETTER_THAN_MEMCPY);
}
return do_memcpy (n);
}
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);
n -= sigcode - window;
vm_deallocate (mach_task_self (), window, window_size);
longjmp (buf, 1);
}
if (n == 0)
/* Nothing to do. */
return 0;
if (((vm_address_t) other & (vm_page_size - 1)) == 0
&& (offset & (vm_page_size - 1)) == 0
&& n >= VMCOPY_BETTER_THAN_MEMCPY)
/* 1) the start address is page aligned; 2) the offset is page
aligned; and 3) we have more than VMCOPY_BETTER_THAN_MEMCPY
pages. */
{
err = do_vm_copy ();
if (err || n == 0)
/* We failed or we finished. */
{
*size -= n;
return err;
}
assert (n < VMCOPY_BETTER_THAN_MEMCPY);
}
/* Need to do it the hard way. */
window = 0;
window_size = 0;
if (setjmp (buf) == 0)
hurd_catch_signal (sigmask (SIGSEGV) | sigmask (SIGBUS),
window, window + window_size,
&do_copy, (sighandler_t) &fault);
if (! err)
assert (n == 0);
*size -= n;
return err;
}
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