/*

 * A system pager implementation residing in the same task as a program.

 *

 * Copyright (C) 2022, 2023 Paul Boddie <paul@boddie.org.uk>

 *

 * 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 of

 * the License, 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., 51 Franklin Street, Fifth Floor,

 * Boston, MA  02110-1301, USA

 */

#include <l4/re/env.h>

#include <l4/re/c/dataspace.h>

#include <l4/re/c/rm.h>

#include <l4/util/util.h>

#include <ipc/cap_alloc.h>

#include <mem/memory_utils.h>

#include <systypes/base.h>

#include <stdio.h>

#include "dataspace_client.h"

#include "internal_pager.h"

#include "mapped_region.h"

#include "pager_object_server.h"

#define DEBUG 0

/* A simple system pager also acting as a region mapper. */

InternalPager::InternalPager(address_t start, address_t end)

: ExecPager(start, end)

{

}

ipc_server_default_config_type InternalPager::config()

{

  return config_PagerObject;

}

/* Close the pager. */

void InternalPager::close()

{

#if DEBUG

  printf("Internal pager closing...\n");

#endif

}

/* Handle a general exception. */

long InternalPager::exception(l4_exc_regs_t regs, l4_snd_fpage_t *region)

{

  (void) region;

  printf("InternalPager::exception(...) -> pfa = %lx, pc = %lx\n", l4_utcb_exc_pfa(&regs), l4_utcb_exc_pc(&regs));

  while (1)

    l4_sleep_forever();

  return L4_EOK;

}

/* Handle a page fault using any configured regions. */

long InternalPager::page_fault(l4_umword_t pfa, l4_umword_t pc, l4_snd_fpage_t *region)

{

  l4_umword_t addr = pfa & ~7UL, flags = pfa & 7;

#if DEBUG

  printf("page_fault(%lx, %lx) -> %lx (%lx) -> ", pfa, pc, addr, flags);

  l4_thread_regs_t *regs = l4_utcb_tcr();

  printf("regs = %p\n; regs->user[0] = %lx\n", regs, regs->user[0]);

#endif

  /* Obtain a region supporting the fault address. */

  MemoryArea *r, *parent;

  long err = _area.find(addr, &r, &parent);

  if (!err)

  {

    address_t window_size = L4_PAGESIZE;

    address_t window_base = trunc(addr, window_size);

    address_t offset = addr - r->area_start();

    address_t page_addr = trunc(addr, L4_PAGESIZE);

    address_t hot_spot = page_addr - window_base;

    /* Interact with the region's dataspace, specifying a receive window for a

       map operation. Here, a single page is specified. */

    client_Dataspace dataspace(r->dataspace());

    l4_snd_fpage_t rw_region = {0, l4_fpage(window_base, L4_PAGESHIFT, 0)};

    map_flags_t map_flags = map_flags_for_fault(flags);

#if DEBUG

    printf("window_base = %lx; window_size = %lx\n", window_base, window_size);

    printf("region = {%lx, {%lx, %d}}\n", rw_region.snd_base, l4_fpage_memaddr(rw_region.fpage), l4_fpage_size(rw_region.fpage));

    printf("map(%lx, %lx, %lx) -> %lx\n", offset, hot_spot, map_flags, r->dataspace());

#endif

    err = dataspace.map(offset, hot_spot, map_flags & r->flags(), &rw_region);

    /* Indicate an unspecified result, since the mapping should have taken

       place. */

    *region = {0, l4_fpage_invalid()};

    return err;

  }

  printf("InternalPager: not mapped at %lx for pc %lx\n", addr, pc);

  return err;

}

/* Attach a region for provision when page faults occur. This is required in

   the initialisation of a program by the C library which requires a region

   mapper. */

long InternalPager::attach(address_t *start, address_t size, map_flags_t flags,

                           l4_cap_idx_t ds, address_t offset,

                           unsigned char align)

{

  /* NOTE: The offset apparently indicates the offset within the dataspace of

           the start of the region. */

  (void) offset;

  MemoryArea *area;

  long err = ExecPager::find(start, &size, flags, align, &area);

  if (!err)

  {

    MappedRegion r(*start, *start + size, flags & L4RE_DS_F_RIGHTS_MASK, ds);

    area->add(r);

  }

  else

    ipc_cap_free_um(ds);

  return err;

}

long InternalPager::detach(address_t addr, address_t size, map_flags_t flags,

                           address_t *start, address_t *rsize, l4_cap_idx_t *ds)

{

  (void) size; (void) flags;

  /* Obtain the region supporting the given address.

     NOTE: All regions within the given range should be detached. */

  MemoryArea *r, *parent;

  long err = _area.find(addr, &r, &parent);

  if (!err)

  {

    *start = r->area_start();

    *rsize = r->area_end() - r->area_start();

    *ds = r->dataspace();

    parent->remove(*r);

  }

  return err;

}

long InternalPager::reserve_area(address_t *start, address_t size,

                                 map_flags_t flags, unsigned char align)

{

  MemoryArea *area;

  long err = ExecPager::find(start, &size, flags, align, &area);

  if (!err)

  {

    /* Add an object acting like a region but without any associated

       dataspace. */

    if (flags & L4RE_RM_F_RESERVED)

    {

      ReservedMemoryArea r(*start, *start + size);

      area->add(r);

    }

    /* Add an object permitting regions to be added within it. */

    else

    {

      AvailableMemoryArea r(*start, *start + size);

      area->add(r);

    }

  }

  return err;

}

/* vim: tabstop=2 expandtab shiftwidth=2

*/