/*      $NetBSD: uvm_device.c,v 1.80 2022/07/07 13:27:02 riastradh Exp $        */

/*
 * Copyright (c) 1997 Charles D. Cranor and Washington University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * from: Id: uvm_device.c,v 1.1.2.9 1998/02/06 05:11:47 chs Exp
 */

/*
 * uvm_device.c: the device pager.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_device.c,v 1.80 2022/07/07 13:27:02 riastradh Exp $");

#include "opt_uvmhist.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/proc.h>
#include <sys/kmem.h>

#include <uvm/uvm.h>
#include <uvm/uvm_device.h>
#include <uvm/uvm_pmap.h>

/*
 * private global data structure
 *
 * we keep a list of active device objects in the system.
 */

LIST_HEAD(udv_list_struct, uvm_device);
static struct udv_list_struct udv_list;
static kmutex_t udv_lock __cacheline_aligned;

/*
 * functions
 */

static void     udv_init(void);
static void     udv_reference(struct uvm_object *);
static void     udv_detach(struct uvm_object *);
static int      udv_fault(struct uvm_faultinfo *, vaddr_t,
                          struct vm_page **, int, int, vm_prot_t,
                          int);

/*
 * master pager structure
 */

const struct uvm_pagerops uvm_deviceops = {
        .pgo_init = udv_init,
        .pgo_reference = udv_reference,
        .pgo_detach = udv_detach,
        .pgo_fault = udv_fault,
};

/*
 * the ops!
 */

/*
 * udv_init
 *
 * init pager private data structures.
 */

static void
udv_init(void)
{
        LIST_INIT(&udv_list);
        mutex_init(&udv_lock, MUTEX_DEFAULT, IPL_NONE);
}

/*
 * udv_attach
 *
 * get a VM object that is associated with a device.   allocate a new
 * one if needed.
 *
 * => caller must _not_ already be holding the lock on the uvm_object.
 * => in fact, nothing should be locked so that we can sleep here.
 */

struct uvm_object *
udv_attach(dev_t device, vm_prot_t accessprot,
    voff_t off,         /* used only for access check */
    vsize_t size        /* used only for access check */)
{
        struct uvm_device *udv, *lcv;
        const struct cdevsw *cdev;
        dev_mmap_t *mapfn;

        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist, "(device=%#jx)", device,0,0,0);

        KASSERT(size > 0);

        /*
         * before we do anything, ensure this device supports mmap
         */

        cdev = cdevsw_lookup(device);
        if (cdev == NULL) {
                return NULL;
        }
        mapfn = cdev->d_mmap;
        if (mapfn == NULL || mapfn == nommap) {
                return NULL;
        }

        /*
         * Negative offsets on the object are not allowed, unless the
         * device has affirmatively set D_NEGOFFSAFE.
         */
        if ((cdev->d_flag & D_NEGOFFSAFE) == 0 && off != UVM_UNKNOWN_OFFSET) {
                if (off < 0)
                        return NULL;
#if SIZE_MAX > UINT32_MAX       /* XXX -Wtype-limits */
                if (size > __type_max(voff_t))
                        return NULL;
#endif
                if (off > __type_max(voff_t) - size)
                        return NULL;
        }

        /*
         * Check that the specified range of the device allows the
         * desired protection.
         *
         * XXX assumes VM_PROT_* == PROT_*
         * XXX clobbers off and size, but nothing else here needs them.
         */
        do {
                KASSERTMSG((off % PAGE_SIZE) == 0, "off=%jd", (intmax_t)off);
                KASSERTMSG(size >= PAGE_SIZE, "size=%"PRIuVSIZE, size);
                if (cdev_mmap(device, off, accessprot) == -1)
                        return NULL;
                KASSERT(off <= __type_max(voff_t) - PAGE_SIZE ||
                    (cdev->d_flag & D_NEGOFFSAFE) != 0);
                if (__predict_false(off > __type_max(voff_t) - PAGE_SIZE)) {
                        /*
                         * off += PAGE_SIZE, with two's-complement
                         * wraparound, or
                         *
                         *      off += PAGE_SIZE - 2*(VOFF_MAX + 1).
                         */
                        CTASSERT(MIN_PAGE_SIZE >= 2);
                        off -= __type_max(voff_t);
                        off += PAGE_SIZE - 2;
                        off -= __type_max(voff_t);
                } else {
                        off += PAGE_SIZE;
                }
                size -= PAGE_SIZE;
        } while (size != 0);

        /*
         * keep looping until we get it
         */

        for (;;) {

                /*
                 * first, attempt to find it on the main list
                 */

                mutex_enter(&udv_lock);
                LIST_FOREACH(lcv, &udv_list, u_list) {
                        if (device == lcv->u_device)
                                break;
                }

                /*
                 * got it on main list.  put a hold on it and unlock udv_lock.
                 */

                if (lcv) {

                        /*
                         * if someone else has a hold on it, sleep and start
                         * over again.
                         */

                        if (lcv->u_flags & UVM_DEVICE_HOLD) {
                                lcv->u_flags |= UVM_DEVICE_WANTED;
                                UVM_UNLOCK_AND_WAIT(lcv, &udv_lock, false,
                                    "udv_attach",0);
                                continue;
                        }

                        /* we are now holding it */
                        lcv->u_flags |= UVM_DEVICE_HOLD;
                        mutex_exit(&udv_lock);

                        /*
                         * bump reference count, unhold, return.
                         */

                        rw_enter(lcv->u_obj.vmobjlock, RW_WRITER);
                        lcv->u_obj.uo_refs++;
                        rw_exit(lcv->u_obj.vmobjlock);

                        mutex_enter(&udv_lock);
                        if (lcv->u_flags & UVM_DEVICE_WANTED)
                                wakeup(lcv);
                        lcv->u_flags &= ~(UVM_DEVICE_WANTED|UVM_DEVICE_HOLD);
                        mutex_exit(&udv_lock);
                        return &lcv->u_obj;
                }

                /*
                 * Did not find it on main list.  Need to allocate a new one.
                 */

                mutex_exit(&udv_lock);

                /* Note: both calls may allocate memory and sleep. */
                udv = kmem_alloc(sizeof(*udv), KM_SLEEP);
                uvm_obj_init(&udv->u_obj, &uvm_deviceops, true, 1);

                mutex_enter(&udv_lock);

                /*
                 * now we have to double check to make sure no one added it
                 * to the list while we were sleeping...
                 */

                LIST_FOREACH(lcv, &udv_list, u_list) {
                        if (device == lcv->u_device)
                                break;
                }

                /*
                 * did we lose a race to someone else?
                 * free our memory and retry.
                 */

                if (lcv) {
                        mutex_exit(&udv_lock);
                        uvm_obj_destroy(&udv->u_obj, true);
                        kmem_free(udv, sizeof(*udv));
                        continue;
                }

                /*
                 * we have it!   init the data structures, add to list
                 * and return.
                 */

                udv->u_flags = 0;
                udv->u_device = device;
                LIST_INSERT_HEAD(&udv_list, udv, u_list);
                mutex_exit(&udv_lock);
                return &udv->u_obj;
        }
        /*NOTREACHED*/
}

/*
 * udv_reference
 *
 * add a reference to a VM object.   Note that the reference count must
 * already be one (the passed in reference) so there is no chance of the
 * udv being released or locked out here.
 *
 * => caller must call with object unlocked.
 */

static void
udv_reference(struct uvm_object *uobj)
{
        UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);

        rw_enter(uobj->vmobjlock, RW_WRITER);
        uobj->uo_refs++;
        UVMHIST_LOG(maphist, "<- done (uobj=%#jx, ref = %jd)",
            (uintptr_t)uobj, uobj->uo_refs,0,0);
        rw_exit(uobj->vmobjlock);
}

/*
 * udv_detach
 *
 * remove a reference to a VM object.
 *
 * => caller must call with object unlocked and map locked.
 */

static void
udv_detach(struct uvm_object *uobj)
{
        struct uvm_device *udv = (struct uvm_device *)uobj;
        UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);

        /*
         * loop until done
         */
again:
        rw_enter(uobj->vmobjlock, RW_WRITER);
        if (uobj->uo_refs > 1) {
                uobj->uo_refs--;
                rw_exit(uobj->vmobjlock);
                UVMHIST_LOG(maphist," <- done, uobj=%#jx, ref=%jd",
                    (uintptr_t)uobj,uobj->uo_refs,0,0);
                return;
        }

        /*
         * is it being held?   if so, wait until others are done.
         */

        mutex_enter(&udv_lock);
        if (udv->u_flags & UVM_DEVICE_HOLD) {
                udv->u_flags |= UVM_DEVICE_WANTED;
                rw_exit(uobj->vmobjlock);
                UVM_UNLOCK_AND_WAIT(udv, &udv_lock, false, "udv_detach",0);
                goto again;
        }

        /*
         * got it!   nuke it now.
         */

        LIST_REMOVE(udv, u_list);
        if (udv->u_flags & UVM_DEVICE_WANTED)
                wakeup(udv);
        mutex_exit(&udv_lock);
        rw_exit(uobj->vmobjlock);

        uvm_obj_destroy(uobj, true);
        kmem_free(udv, sizeof(*udv));
        UVMHIST_LOG(maphist," <- done, freed uobj=%#jx", (uintptr_t)uobj,
            0, 0, 0);
}

/*
 * udv_fault: non-standard fault routine for device "pages"
 *
 * => rather than having a "get" function, we have a fault routine
 *      since we don't return vm_pages we need full control over the
 *      pmap_enter map in
 * => all the usual fault data structured are locked by the caller
 *      (i.e. maps(read), amap (if any), uobj)
 * => on return, we unlock all fault data structures
 * => flags: PGO_ALLPAGES: get all of the pages
 *           PGO_LOCKED: fault data structures are locked
 *    XXX: currently PGO_LOCKED is always required ... consider removing
 *      it as a flag
 * => NOTE: vaddr is the VA of pps[0] in ufi->entry, _NOT_ pps[centeridx]
 */

static int
udv_fault(struct uvm_faultinfo *ufi, vaddr_t vaddr, struct vm_page **pps,
    int npages, int centeridx, vm_prot_t access_type,
    int flags)
{
        struct vm_map_entry *entry = ufi->entry;
        struct uvm_object *uobj = entry->object.uvm_obj;
        struct uvm_device *udv = (struct uvm_device *)uobj;
        vaddr_t curr_va;
        off_t curr_offset;
        paddr_t paddr, mdpgno;
        u_int mmapflags;
        int lcv, retval;
        dev_t device;
        vm_prot_t mapprot;
        UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);
        UVMHIST_LOG(maphist,"  flags=%#jx", flags,0,0,0);

        /*
         * we do not allow device mappings to be mapped copy-on-write
         * so we kill any attempt to do so here.
         */

        if (UVM_ET_ISCOPYONWRITE(entry)) {
                UVMHIST_LOG(maphist, "<- failed -- COW entry (etype=%#jx)",
                    entry->etype, 0,0,0);
                uvmfault_unlockall(ufi, ufi->entry->aref.ar_amap, uobj);
                return EIO;
        }

        /*
         * get device map function.
         */

        device = udv->u_device;
        if (cdevsw_lookup(device) == NULL) {
                /* XXX This should not happen */
                uvmfault_unlockall(ufi, ufi->entry->aref.ar_amap, uobj);
                return EIO;
        }

        /*
         * now we must determine the offset in udv to use and the VA to
         * use for pmap_enter.  note that we always use orig_map's pmap
         * for pmap_enter (even if we have a submap).   since virtual
         * addresses in a submap must match the main map, this is ok.
         */

        /* udv offset = (offset from start of entry) + entry's offset */
        curr_offset = entry->offset + (vaddr - entry->start);
        /* pmap va = vaddr (virtual address of pps[0]) */
        curr_va = vaddr;

        /*
         * loop over the page range entering in as needed
         */

        retval = 0;
        for (lcv = 0 ; lcv < npages ; lcv++, curr_offset += PAGE_SIZE,
            curr_va += PAGE_SIZE) {
                if ((flags & PGO_ALLPAGES) == 0 && lcv != centeridx)
                        continue;

                if (pps[lcv] == PGO_DONTCARE)
                        continue;

                mdpgno = cdev_mmap(device, curr_offset, access_type);
                if (mdpgno == -1) {
                        retval = EIO;
                        break;
                }
                paddr = pmap_phys_address(mdpgno);
                mmapflags = pmap_mmap_flags(mdpgno);
                mapprot = ufi->entry->protection;
                UVMHIST_LOG(maphist,
                    "  MAPPING: device: pm=%#jx, va=%#jx, pa=%#jx, at=%jd",
                    (uintptr_t)ufi->orig_map->pmap, curr_va, paddr, mapprot);
                if (pmap_enter(ufi->orig_map->pmap, curr_va, paddr, mapprot,
                    PMAP_CANFAIL | mapprot | mmapflags) != 0) {
                        /*
                         * pmap_enter() didn't have the resource to
                         * enter this mapping.  Unlock everything,
                         * wait for the pagedaemon to free up some
                         * pages, and then tell uvm_fault() to start
                         * the fault again.
                         *
                         * XXX Needs some rethinking for the PGO_ALLPAGES
                         * XXX case.
                         */
                        pmap_update(ufi->orig_map->pmap);       /* sync what we have so far */
                        uvmfault_unlockall(ufi, ufi->entry->aref.ar_amap,
                            uobj);
                        return ENOMEM;
                }
        }

        pmap_update(ufi->orig_map->pmap);
        uvmfault_unlockall(ufi, ufi->entry->aref.ar_amap, uobj);
        return retval;
}