/*      $OpenBSD: db_memrw.c,v 1.9 2024/02/23 18:19:02 cheloha Exp $    */
/*      $NetBSD: db_memrw.c,v 1.1 2003/04/26 18:39:27 fvdl Exp $        */

/*-
 * Copyright (c) 1996, 2000 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Gordon W. Ross and Jason R. Thorpe.
 *
 * 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``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 FOUNDATION OR CONTRIBUTORS
 * 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.
 */

/*
 * Interface to the debugger for virtual memory read/write.
 *
 * To write in the text segment, we have to first make
 * the page writable, do the write, then restore the PTE.
 * For writes outside the text segment, and all reads,
 * just do the access -- if it causes a fault, the debugger
 * will recover with a longjmp to an appropriate place.
 *
 * ALERT!  If you want to access device registers with a
 * specific size, then the read/write functions have to
 * make sure to do the correct sized pointer access.
 *
 * Modified for i386 from hp300 version by
 * Jason R. Thorpe <thorpej@zembu.com>.
 *
 * Basic copy to amd64 by fvdl.
 */

#include <sys/param.h>
#include <sys/systm.h>

#include <uvm/uvm_extern.h>

#include <machine/db_machdep.h>

/*
 * Read bytes from kernel address space for debugger.
 */
void
db_read_bytes(vaddr_t addr, size_t size, void *datap)
{
        char *data = datap, *src;

        src = (char *)addr;

        if (size == 8) {
                *((long *)data) = *((long *)src);
                return;
        }

        if (size == 4) {
                *((int *)data) = *((int *)src);
                return;
        }

        if (size == 2) {
                *((short *)data) = *((short *)src);
                return;
        }

        while (size-- > 0)
                *data++ = *src++;
}

/*
 * Write bytes somewhere in the kernel text.  Make the text
 * pages writable temporarily.
 */
static void
db_write_text(vaddr_t addr, size_t size, char *data)
{
        pt_entry_t *pte, oldpte, tmppte;
        vaddr_t pgva;
        size_t limit;
        char *dst;

        if (size == 0)
                return;

        dst = (char *)addr;

        do {
                /*
                 * Get the PTE for the page.
                 */
                pte = kvtopte(addr);
                oldpte = *pte;

                if ((oldpte & PG_V) == 0) {
                        printf(" address %p not a valid page\n", dst);
                        return;
                }

                /*
                 * Get the VA for the page.
                 */
                if (oldpte & PG_PS)
                        pgva = (vaddr_t)dst & PG_LGFRAME;
                else
                        pgva = trunc_page((vaddr_t)dst);

                /*
                 * Compute number of bytes that can be written
                 * with this mapping and subtract it from the
                 * total size.
                 */
                if (oldpte & PG_PS)
                        limit = NBPD_L2 - ((vaddr_t)dst & (NBPD_L2 - 1));
                else
                        limit = PAGE_SIZE - ((vaddr_t)dst & PGOFSET);
                if (limit > size)
                        limit = size;
                size -= limit;

                tmppte = (oldpte & ~PG_KR) | PG_KW;
                *pte = tmppte;
                pmap_update_pg(pgva);

                /*
                 * Page is now writable.  Do as much access as we
                 * can in this page.
                 */
                for (; limit > 0; limit--)
                        *dst++ = *data++;

                /*
                 * Restore the old PTE.
                 */
                *pte = oldpte;

                pmap_update_pg(pgva);
                
        } while (size != 0);
}

/*
 * Write bytes to kernel address space for debugger.
 */
void
db_write_bytes(vaddr_t addr, size_t size, void *datap)
{
        extern char etext;
        char *data = datap, *dst;

        /* If any part is in kernel text, use db_write_text() */
        if (addr >= KERNBASE && addr < (vaddr_t)&etext) {
                db_write_text(addr, size, data);
                return;
        }

        dst = (char *)addr;

        if (size == 8) {
                *((long *)dst) = *((long *)data);
                return;
        }

        if (size == 4) {
                *((int *)dst) = *((int *)data);
                return;
        }

        if (size == 2) {
                *((short *)dst) = *((short *)data);
                return;
        }

        while (size-- > 0)
                *dst++ = *data++;
}