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Initial Spring 2016 commit.

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This commit is contained in:
Geoffrey Challen
2015-12-23 00:50:04 +00:00
commit cafa9f5690
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433
kern/arch/mips/vm/dumbvm.c Normal file
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/*
* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
* The President and Fellows of Harvard College.
*
* 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.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY 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 UNIVERSITY 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.
*/
#include <types.h>
#include <kern/errno.h>
#include <lib.h>
#include <spl.h>
#include <cpu.h>
#include <spinlock.h>
#include <proc.h>
#include <current.h>
#include <mips/tlb.h>
#include <addrspace.h>
#include <vm.h>
/*
* Dumb MIPS-only "VM system" that is intended to only be just barely
* enough to struggle off the ground. You should replace all of this
* code while doing the VM assignment. In fact, starting in that
* assignment, this file is not included in your kernel!
*
* NOTE: it's been found over the years that students often begin on
* the VM assignment by copying dumbvm.c and trying to improve it.
* This is not recommended. dumbvm is (more or less intentionally) not
* a good design reference. The first recommendation would be: do not
* look at dumbvm at all. The second recommendation would be: if you
* do, be sure to review it from the perspective of comparing it to
* what a VM system is supposed to do, and understanding what corners
* it's cutting (there are many) and why, and more importantly, how.
*/
/* under dumbvm, always have 72k of user stack */
/* (this must be > 64K so argument blocks of size ARG_MAX will fit) */
#define DUMBVM_STACKPAGES 18
/*
* Wrap ram_stealmem in a spinlock.
*/
static struct spinlock stealmem_lock = SPINLOCK_INITIALIZER;
void
vm_bootstrap(void)
{
/* Do nothing. */
}
/*
* Check if we're in a context that can sleep. While most of the
* operations in dumbvm don't in fact sleep, in a real VM system many
* of them would. In those, assert that sleeping is ok. This helps
* avoid the situation where syscall-layer code that works ok with
* dumbvm starts blowing up during the VM assignment.
*/
static
void
dumbvm_can_sleep(void)
{
if (CURCPU_EXISTS()) {
/* must not hold spinlocks */
KASSERT(curcpu->c_spinlocks == 0);
/* must not be in an interrupt handler */
KASSERT(curthread->t_in_interrupt == 0);
}
}
static
paddr_t
getppages(unsigned long npages)
{
paddr_t addr;
spinlock_acquire(&stealmem_lock);
addr = ram_stealmem(npages);
spinlock_release(&stealmem_lock);
return addr;
}
/* Allocate/free some kernel-space virtual pages */
vaddr_t
alloc_kpages(unsigned npages)
{
paddr_t pa;
dumbvm_can_sleep();
pa = getppages(npages);
if (pa==0) {
return 0;
}
return PADDR_TO_KVADDR(pa);
}
void
free_kpages(vaddr_t addr)
{
/* nothing - leak the memory. */
(void)addr;
}
void
vm_tlbshootdown_all(void)
{
panic("dumbvm tried to do tlb shootdown?!\n");
}
void
vm_tlbshootdown(const struct tlbshootdown *ts)
{
(void)ts;
panic("dumbvm tried to do tlb shootdown?!\n");
}
int
vm_fault(int faulttype, vaddr_t faultaddress)
{
vaddr_t vbase1, vtop1, vbase2, vtop2, stackbase, stacktop;
paddr_t paddr;
int i;
uint32_t ehi, elo;
struct addrspace *as;
int spl;
faultaddress &= PAGE_FRAME;
DEBUG(DB_VM, "dumbvm: fault: 0x%x\n", faultaddress);
switch (faulttype) {
case VM_FAULT_READONLY:
/* We always create pages read-write, so we can't get this */
panic("dumbvm: got VM_FAULT_READONLY\n");
case VM_FAULT_READ:
case VM_FAULT_WRITE:
break;
default:
return EINVAL;
}
if (curproc == NULL) {
/*
* No process. This is probably a kernel fault early
* in boot. Return EFAULT so as to panic instead of
* getting into an infinite faulting loop.
*/
return EFAULT;
}
as = proc_getas();
if (as == NULL) {
/*
* No address space set up. This is probably also a
* kernel fault early in boot.
*/
return EFAULT;
}
/* Assert that the address space has been set up properly. */
KASSERT(as->as_vbase1 != 0);
KASSERT(as->as_pbase1 != 0);
KASSERT(as->as_npages1 != 0);
KASSERT(as->as_vbase2 != 0);
KASSERT(as->as_pbase2 != 0);
KASSERT(as->as_npages2 != 0);
KASSERT(as->as_stackpbase != 0);
KASSERT((as->as_vbase1 & PAGE_FRAME) == as->as_vbase1);
KASSERT((as->as_pbase1 & PAGE_FRAME) == as->as_pbase1);
KASSERT((as->as_vbase2 & PAGE_FRAME) == as->as_vbase2);
KASSERT((as->as_pbase2 & PAGE_FRAME) == as->as_pbase2);
KASSERT((as->as_stackpbase & PAGE_FRAME) == as->as_stackpbase);
vbase1 = as->as_vbase1;
vtop1 = vbase1 + as->as_npages1 * PAGE_SIZE;
vbase2 = as->as_vbase2;
vtop2 = vbase2 + as->as_npages2 * PAGE_SIZE;
stackbase = USERSTACK - DUMBVM_STACKPAGES * PAGE_SIZE;
stacktop = USERSTACK;
if (faultaddress >= vbase1 && faultaddress < vtop1) {
paddr = (faultaddress - vbase1) + as->as_pbase1;
}
else if (faultaddress >= vbase2 && faultaddress < vtop2) {
paddr = (faultaddress - vbase2) + as->as_pbase2;
}
else if (faultaddress >= stackbase && faultaddress < stacktop) {
paddr = (faultaddress - stackbase) + as->as_stackpbase;
}
else {
return EFAULT;
}
/* make sure it's page-aligned */
KASSERT((paddr & PAGE_FRAME) == paddr);
/* Disable interrupts on this CPU while frobbing the TLB. */
spl = splhigh();
for (i=0; i<NUM_TLB; i++) {
tlb_read(&ehi, &elo, i);
if (elo & TLBLO_VALID) {
continue;
}
ehi = faultaddress;
elo = paddr | TLBLO_DIRTY | TLBLO_VALID;
DEBUG(DB_VM, "dumbvm: 0x%x -> 0x%x\n", faultaddress, paddr);
tlb_write(ehi, elo, i);
splx(spl);
return 0;
}
kprintf("dumbvm: Ran out of TLB entries - cannot handle page fault\n");
splx(spl);
return EFAULT;
}
struct addrspace *
as_create(void)
{
struct addrspace *as = kmalloc(sizeof(struct addrspace));
if (as==NULL) {
return NULL;
}
as->as_vbase1 = 0;
as->as_pbase1 = 0;
as->as_npages1 = 0;
as->as_vbase2 = 0;
as->as_pbase2 = 0;
as->as_npages2 = 0;
as->as_stackpbase = 0;
return as;
}
void
as_destroy(struct addrspace *as)
{
dumbvm_can_sleep();
kfree(as);
}
void
as_activate(void)
{
int i, spl;
struct addrspace *as;
as = proc_getas();
if (as == NULL) {
return;
}
/* Disable interrupts on this CPU while frobbing the TLB. */
spl = splhigh();
for (i=0; i<NUM_TLB; i++) {
tlb_write(TLBHI_INVALID(i), TLBLO_INVALID(), i);
}
splx(spl);
}
void
as_deactivate(void)
{
/* nothing */
}
int
as_define_region(struct addrspace *as, vaddr_t vaddr, size_t sz,
int readable, int writeable, int executable)
{
size_t npages;
dumbvm_can_sleep();
/* Align the region. First, the base... */
sz += vaddr & ~(vaddr_t)PAGE_FRAME;
vaddr &= PAGE_FRAME;
/* ...and now the length. */
sz = (sz + PAGE_SIZE - 1) & PAGE_FRAME;
npages = sz / PAGE_SIZE;
/* We don't use these - all pages are read-write */
(void)readable;
(void)writeable;
(void)executable;
if (as->as_vbase1 == 0) {
as->as_vbase1 = vaddr;
as->as_npages1 = npages;
return 0;
}
if (as->as_vbase2 == 0) {
as->as_vbase2 = vaddr;
as->as_npages2 = npages;
return 0;
}
/*
* Support for more than two regions is not available.
*/
kprintf("dumbvm: Warning: too many regions\n");
return ENOSYS;
}
static
void
as_zero_region(paddr_t paddr, unsigned npages)
{
bzero((void *)PADDR_TO_KVADDR(paddr), npages * PAGE_SIZE);
}
int
as_prepare_load(struct addrspace *as)
{
KASSERT(as->as_pbase1 == 0);
KASSERT(as->as_pbase2 == 0);
KASSERT(as->as_stackpbase == 0);
dumbvm_can_sleep();
as->as_pbase1 = getppages(as->as_npages1);
if (as->as_pbase1 == 0) {
return ENOMEM;
}
as->as_pbase2 = getppages(as->as_npages2);
if (as->as_pbase2 == 0) {
return ENOMEM;
}
as->as_stackpbase = getppages(DUMBVM_STACKPAGES);
if (as->as_stackpbase == 0) {
return ENOMEM;
}
as_zero_region(as->as_pbase1, as->as_npages1);
as_zero_region(as->as_pbase2, as->as_npages2);
as_zero_region(as->as_stackpbase, DUMBVM_STACKPAGES);
return 0;
}
int
as_complete_load(struct addrspace *as)
{
dumbvm_can_sleep();
(void)as;
return 0;
}
int
as_define_stack(struct addrspace *as, vaddr_t *stackptr)
{
KASSERT(as->as_stackpbase != 0);
*stackptr = USERSTACK;
return 0;
}
int
as_copy(struct addrspace *old, struct addrspace **ret)
{
struct addrspace *new;
dumbvm_can_sleep();
new = as_create();
if (new==NULL) {
return ENOMEM;
}
new->as_vbase1 = old->as_vbase1;
new->as_npages1 = old->as_npages1;
new->as_vbase2 = old->as_vbase2;
new->as_npages2 = old->as_npages2;
/* (Mis)use as_prepare_load to allocate some physical memory. */
if (as_prepare_load(new)) {
as_destroy(new);
return ENOMEM;
}
KASSERT(new->as_pbase1 != 0);
KASSERT(new->as_pbase2 != 0);
KASSERT(new->as_stackpbase != 0);
memmove((void *)PADDR_TO_KVADDR(new->as_pbase1),
(const void *)PADDR_TO_KVADDR(old->as_pbase1),
old->as_npages1*PAGE_SIZE);
memmove((void *)PADDR_TO_KVADDR(new->as_pbase2),
(const void *)PADDR_TO_KVADDR(old->as_pbase2),
old->as_npages2*PAGE_SIZE);
memmove((void *)PADDR_TO_KVADDR(new->as_stackpbase),
(const void *)PADDR_TO_KVADDR(old->as_stackpbase),
DUMBVM_STACKPAGES*PAGE_SIZE);
*ret = new;
return 0;
}

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kern/arch/mips/vm/ram.c Normal file
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/*
* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
* The President and Fellows of Harvard College.
*
* 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.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY 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 UNIVERSITY 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.
*/
#include <types.h>
#include <lib.h>
#include <vm.h>
#include <mainbus.h>
vaddr_t firstfree; /* first free virtual address; set by start.S */
static paddr_t firstpaddr; /* address of first free physical page */
static paddr_t lastpaddr; /* one past end of last free physical page */
/*
* Called very early in system boot to figure out how much physical
* RAM is available.
*/
void
ram_bootstrap(void)
{
size_t ramsize;
/* Get size of RAM. */
ramsize = mainbus_ramsize();
/*
* This is the same as the last physical address, as long as
* we have less than 512 megabytes of memory. If we had more,
* we wouldn't be able to access it all through kseg0 and
* everything would get a lot more complicated. This is not a
* case we are going to worry about.
*/
if (ramsize > 512*1024*1024) {
ramsize = 512*1024*1024;
}
lastpaddr = ramsize;
/*
* Get first free virtual address from where start.S saved it.
* Convert to physical address.
*/
firstpaddr = firstfree - MIPS_KSEG0;
kprintf("%uk physical memory available\n",
(lastpaddr-firstpaddr)/1024);
}
/*
* This function is for allocating physical memory prior to VM
* initialization.
*
* The pages it hands back will not be reported to the VM system when
* the VM system calls ram_getsize(). If it's desired to free up these
* pages later on after bootup is complete, some mechanism for adding
* them to the VM system's page management must be implemented.
* Alternatively, one can do enough VM initialization early so that
* this function is never needed.
*
* Note: while the error return value of 0 is a legal physical address,
* it's not a legal *allocatable* physical address, because it's the
* page with the exception handlers on it.
*
* This function should not be called once the VM system is initialized,
* so it is not synchronized.
*/
paddr_t
ram_stealmem(unsigned long npages)
{
size_t size;
paddr_t paddr;
size = npages * PAGE_SIZE;
if (firstpaddr + size > lastpaddr) {
return 0;
}
paddr = firstpaddr;
firstpaddr += size;
return paddr;
}
/*
* This function is intended to be called by the VM system when it
* initializes in order to find out what memory it has available to
* manage. Physical memory begins at physical address 0 and ends with
* the address returned by this function. We assume that physical
* memory is contiguous. This is not universally true, but is true on
* the MIPS platforms we intend to run on.
*
* lastpaddr is constant once set by ram_bootstrap(), so this function
* need not be synchronized.
*
* It is recommended, however, that this function be used only to
* initialize the VM system, after which the VM system should take
* charge of knowing what memory exists.
*/
paddr_t
ram_getsize(void)
{
return lastpaddr;
}
/*
* This function is intended to be called by the VM system when it
* initializes in order to find out what memory it has available to
* manage.
*
* It can only be called once, and once called ram_stealmem() will
* no longer work, as that would invalidate the result it returned
* and lead to multiple things using the same memory.
*
* This function should not be called once the VM system is initialized,
* so it is not synchronized.
*/
paddr_t
ram_getfirstfree(void)
{
paddr_t ret;
ret = firstpaddr;
firstpaddr = lastpaddr = 0;
return ret;
}

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kern/arch/mips/vm/tlb-mips161.S Normal file
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/*
* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
* The President and Fellows of Harvard College.
*
* 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.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY 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 UNIVERSITY 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.
*/
#include <kern/mips/regdefs.h>
#include <mips/specialreg.h>
/*
* TLB handling for the MIPS-161.
*
* The MIPS-161 uses the simpler MIPS-1 (r2000/r3000) TLB rather
* than the paired-page TLB of later MIPS models.
*
* However, we handle MIPS32 pipeline hazards. If you want to run on
* a real MIPS-1, change the ssnops to plain nops and check where and
* how many you need in the matching processor docs.
*
* (ssnop means "superscalar nop"; it exists because the pipeline
* hazards require a fixed number of cycles, and a superscalar CPU can
* potentially issue arbitrarily many nops in one cycle.)
*/
.text
.set noreorder
.set mips32 /* so we can use ssnop */
/*
* tlb_random: use the "tlbwr" instruction to write a TLB entry
* into a (very pseudo-) random slot in the TLB.
*
* Pipeline hazard: must wait between setting entryhi/lo and
* doing the tlbwr. Use two cycles; some processors may vary.
*/
.globl tlb_random
.type tlb_random,@function
.ent tlb_random
tlb_random:
mtc0 a0, c0_entryhi /* store the passed entry into the */
mtc0 a1, c0_entrylo /* tlb entry registers */
ssnop /* wait for pipeline hazard */
ssnop
tlbwr /* do it */
j ra
nop
.end tlb_random
/*
* tlb_write: use the "tlbwi" instruction to write a TLB entry
* into a selected slot in the TLB.
*
* Pipeline hazard: must wait between setting entryhi/lo and
* doing the tlbwi. Use two cycles; some processors may vary.
*/
.text
.globl tlb_write
.type tlb_write,@function
.ent tlb_write
tlb_write:
mtc0 a0, c0_entryhi /* store the passed entry into the */
mtc0 a1, c0_entrylo /* tlb entry registers */
sll t0, a2, CIN_INDEXSHIFT /* shift the passed index into place */
mtc0 t0, c0_index /* store the shifted index into the index register */
ssnop /* wait for pipeline hazard */
ssnop
tlbwi /* do it */
j ra
nop
.end tlb_write
/*
* tlb_read: use the "tlbr" instruction to read a TLB entry
* from a selected slot in the TLB.
*
* Pipeline hazard: must wait between setting c0_index and
* doing the tlbr. Use two cycles; some processors may vary.
* Similarly, three more cycles before reading c0_entryhi/lo.
*/
.text
.globl tlb_read
.type tlb_read,@function
.ent tlb_read
tlb_read:
sll t0, a2, CIN_INDEXSHIFT /* shift the passed index into place */
mtc0 t0, c0_index /* store the shifted index into the index register */
ssnop /* wait for pipeline hazard */
ssnop
tlbr /* do it */
ssnop /* wait for pipeline hazard */
ssnop
ssnop
mfc0 t0, c0_entryhi /* get the tlb entry out of the */
mfc0 t1, c0_entrylo /* tlb entry registers */
sw t0, 0(a0) /* store through the passed pointer */
j ra
sw t1, 0(a1) /* store (in delay slot) */
.end tlb_read
/*
* tlb_probe: use the "tlbp" instruction to find the index in the
* TLB of a TLB entry matching the relevant parts of the one supplied.
*
* Pipeline hazard: must wait between setting c0_entryhi/lo and
* doing the tlbp. Use two cycles; some processors may vary.
* Similarly, two more cycles before reading c0_index.
*/
.text
.globl tlb_probe
.type tlb_probe,@function
.ent tlb_probe
tlb_probe:
mtc0 a0, c0_entryhi /* store the passed entry into the */
mtc0 a1, c0_entrylo /* tlb entry registers */
ssnop /* wait for pipeline hazard */
ssnop
tlbp /* do it */
ssnop /* wait for pipeline hazard */
ssnop
mfc0 t0, c0_index /* fetch the index back in t0 */
/*
* If the high bit (CIN_P) of c0_index is set, the probe failed.
* The high bit is not set <--> c0_index (now in t0) >= 0.
*/
bgez t0, 1f /* did probe succeed? if so, skip forward */
nop /* delay slot */
addi v0, z0, -1 /* set return value to -1 to indicate failure */
j ra /* done */
nop /* delay slot */
1:
/* succeeded - get the index field from the index register value */
andi t1, t0, CIN_INDEX /* mask off the field */
j ra /* done */
sra v0, t1, CIN_INDEXSHIFT /* shift it (in delay slot) */
.end tlb_probe
/*
* tlb_reset
*
* Initialize the TLB. At processor startup, the TLB state is completely
* undefined. So be sure to avoid creating any duplicates. Also make sure
* that the initialization entries don't duplicate the INVALID entries
* defined in tlb.h. (This way you can write the invalid entries in
* without having to use tlbp to find out if they're going to cause dups.)
*
* This function is not defined in tlb.h because it's only called from
* start.S.
*
* Pipeline hazards are as above.
*/
.text
.globl tlb_reset
.type tlb_reset,@function
.ent tlb_reset
tlb_reset:
li t0, 0 /* t0 <- tlb index number (shifted) */
li t1, 0x81000000 /* t1 <- tlb reset vaddr */
1:
mtc0 $0, c0_entrylo /* set up proposed tlb entry for reset */
mtc0 t1, c0_entryhi
ssnop /* wait for pipeline hazard */
ssnop
tlbp /* check if it already exists */
ssnop /* wait for pipeline hazard */
ssnop
mfc0 t2, c0_index
bgez t2, 1b /* if it does, loop back */
addiu t1, t1, 0x1000 /* next vaddr (in delay slot) */
mtc0 t0, c0_index /* doesn't exist, set index to write to */
ssnop /* wait for pipeline hazard */
ssnop
addiu t0, t0, 0x100 /* next tlb index (shifted) */
bne t0, 0x4000, 1b /* if it's not the last tlb index, loop */
tlbwi /* write tlb entry (in delay slot) */
j ra /* done */
nop /* delay slot */
.end tlb_reset