154 lines
4.9 KiB
C
154 lines
4.9 KiB
C
/*
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* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
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* The President and Fellows of Harvard College.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <types.h>
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#include <lib.h>
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#include <vm.h>
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#include <mainbus.h>
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vaddr_t firstfree; /* first free virtual address; set by start.S */
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static paddr_t firstpaddr; /* address of first free physical page */
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static paddr_t lastpaddr; /* one past end of last free physical page */
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/*
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* Called very early in system boot to figure out how much physical
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* RAM is available.
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*/
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void
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ram_bootstrap(void)
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{
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size_t ramsize;
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/* Get size of RAM. */
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ramsize = mainbus_ramsize();
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/*
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* This is the same as the last physical address, as long as
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* we have less than 512 megabytes of memory. If we had more,
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* we wouldn't be able to access it all through kseg0 and
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* everything would get a lot more complicated. This is not a
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* case we are going to worry about.
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*/
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if (ramsize > 512*1024*1024) {
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ramsize = 512*1024*1024;
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}
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lastpaddr = ramsize;
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/*
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* Get first free virtual address from where start.S saved it.
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* Convert to physical address.
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*/
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firstpaddr = firstfree - MIPS_KSEG0;
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kprintf("%uk physical memory available\n",
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(lastpaddr-firstpaddr)/1024);
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}
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/*
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* This function is for allocating physical memory prior to VM
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* initialization.
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*
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* The pages it hands back will not be reported to the VM system when
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* the VM system calls ram_getsize(). If it's desired to free up these
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* pages later on after bootup is complete, some mechanism for adding
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* them to the VM system's page management must be implemented.
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* Alternatively, one can do enough VM initialization early so that
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* this function is never needed.
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*
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* Note: while the error return value of 0 is a legal physical address,
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* it's not a legal *allocatable* physical address, because it's the
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* page with the exception handlers on it.
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*
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* This function should not be called once the VM system is initialized,
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* so it is not synchronized.
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*/
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paddr_t
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ram_stealmem(unsigned long npages)
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{
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size_t size;
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paddr_t paddr;
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size = npages * PAGE_SIZE;
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if (firstpaddr + size > lastpaddr) {
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return 0;
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}
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paddr = firstpaddr;
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firstpaddr += size;
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return paddr;
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}
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/*
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* This function is intended to be called by the VM system when it
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* initializes in order to find out what memory it has available to
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* manage. Physical memory begins at physical address 0 and ends with
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* the address returned by this function. We assume that physical
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* memory is contiguous. This is not universally true, but is true on
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* the MIPS platforms we intend to run on.
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*
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* lastpaddr is constant once set by ram_bootstrap(), so this function
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* need not be synchronized.
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*
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* It is recommended, however, that this function be used only to
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* initialize the VM system, after which the VM system should take
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* charge of knowing what memory exists.
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*/
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paddr_t
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ram_getsize(void)
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{
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return lastpaddr;
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}
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/*
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* This function is intended to be called by the VM system when it
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* initializes in order to find out what memory it has available to
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* manage.
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*
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* It can only be called once, and once called ram_stealmem() will
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* no longer work, as that would invalidate the result it returned
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* and lead to multiple things using the same memory.
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*
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* This function should not be called once the VM system is initialized,
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* so it is not synchronized.
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*/
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paddr_t
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ram_getfirstfree(void)
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{
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paddr_t ret;
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ret = firstpaddr;
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firstpaddr = lastpaddr = 0;
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return ret;
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}
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