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/*
* Early initialization code for riscv virtual memory
*
* Copyright 2015 Google Inc.
*
* 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; version 2 of
* the License.
*
* 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.
*/
#include <vm.h>
#include <arch/encoding.h>
#include <atomic.h>
#include <stdint.h>
#include <console/console.h>
pte_t* root_page_table;
void walk_page_table(void) {
// TODO: implement a full walk to make sure memory was set up
//const size_t pte_per_page = RISCV_PGSIZE/sizeof(void*);
pte_t* t = root_page_table;
printk(BIOS_DEBUG, "root_page_table: %p\n", t);
}
void enter_supervisor(void) {
// enter supervisor mode
asm volatile("la t0, 1f; csrw mepc, t0; eret; 1:" ::: "t0");
}
void flush_tlb(void)
{
asm volatile("sfence.vm");
}
size_t pte_ppn(pte_t pte)
{
return pte >> PTE_PPN_SHIFT;
}
pte_t ptd_create(uintptr_t ppn)
{
return (ppn << PTE_PPN_SHIFT) | PTE_V | PTE_TYPE_TABLE;
}
pte_t pte_create(uintptr_t ppn, int prot, int user)
{
pte_t pte = (ppn << PTE_PPN_SHIFT) | PTE_V;
if (prot & PROT_WRITE) pte |= PTE_TYPE_URW_SRW;
if (prot & PROT_EXEC) pte |= PTE_TYPE_URX_SRX;
if (!user) pte |= PTE_TYPE_SR;
return pte;
}
void init_vm(uintptr_t virtMemStart, uintptr_t physMemStart, uintptr_t pageTableStart) {
pte_t* sbi_pt = (pte_t*) pageTableStart;
memset(sbi_pt, 0, RISCV_PGSIZE);
// need to leave room for sbi page
uintptr_t memorySize = 0x7F000000; // 0xFFF... - 0xFFFFFFFF81000000 - RISCV_PGSIZE
// middle page table
pte_t* middle_pt = (void*)sbi_pt + RISCV_PGSIZE;
size_t num_middle_pts = 2; // 3 level page table, 39 bit virtual address space for now
// root page table
pte_t* root_pt = (void*)middle_pt + num_middle_pts * RISCV_PGSIZE;
memset(middle_pt, 0, (num_middle_pts + 1) * RISCV_PGSIZE); // 0's out middle_pt and root_pt
for (size_t i = 0; i < num_middle_pts; i++)
root_pt[(1<<RISCV_PGLEVEL_BITS)-num_middle_pts+i] = ptd_create(((uintptr_t)middle_pt >> RISCV_PGSHIFT) + i);
// fill the middle page table
for (uintptr_t vaddr = virtMemStart, paddr = physMemStart; paddr < memorySize; vaddr += SUPERPAGE_SIZE, paddr += SUPERPAGE_SIZE) {
int l2_shift = RISCV_PGLEVEL_BITS + RISCV_PGSHIFT;
size_t l2_idx = (virtMemStart >> l2_shift) & ((1 << RISCV_PGLEVEL_BITS)-1);
l2_idx += ((vaddr - virtMemStart) >> l2_shift);
middle_pt[l2_idx] = pte_create(paddr >> RISCV_PGSHIFT, PROT_READ|PROT_WRITE|PROT_EXEC, 0);
}
// map SBI at top of vaddr space
uintptr_t num_sbi_pages = 1; // only need to map a single page for sbi interface
uintptr_t sbiStartAddress = 0x2000; // the start of the sbi mapping
uintptr_t sbiAddr = sbiStartAddress;
for (uintptr_t i = 0; i < num_sbi_pages; i++) {
uintptr_t idx = (1 << RISCV_PGLEVEL_BITS) - num_sbi_pages + i;
sbi_pt[idx] = pte_create(sbiAddr >> RISCV_PGSHIFT, PROT_READ|PROT_EXEC, 0);
sbiAddr += RISCV_PGSIZE;
}
pte_t* sbi_pte = middle_pt + ((num_middle_pts << RISCV_PGLEVEL_BITS)-1);
*sbi_pte = ptd_create((uintptr_t)sbi_pt >> RISCV_PGSHIFT);
mb();
root_page_table = root_pt;
write_csr(sptbr, root_pt);
}
void initVirtualMemory(void) {
printk(BIOS_DEBUG, "Initializing virtual memory...\n");
uintptr_t physicalStart = 0x1000000; // TODO: Figure out how to grab this from cbfs
uintptr_t virtualStart = 0xffffffff81000000;
uintptr_t pageTableStart = 0x1400000;
init_vm(virtualStart, physicalStart, pageTableStart);
mb();
printk(BIOS_DEBUG, "Finished initializing virtual memory, starting walk...\n");
walk_page_table();
}
void mstatus_init(void)
{
// supervisor support is required
uintptr_t ms = 0;
ms = INSERT_FIELD(ms, MSTATUS_PRV, PRV_M);
ms = INSERT_FIELD(ms, MSTATUS_PRV1, PRV_S);
ms = INSERT_FIELD(ms, MSTATUS_PRV2, PRV_U);
ms = INSERT_FIELD(ms, MSTATUS_IE2, 1);
ms = INSERT_FIELD(ms, MSTATUS_VM, VM_CHOICE);
ms = INSERT_FIELD(ms, MSTATUS_FS, 3);
ms = INSERT_FIELD(ms, MSTATUS_XS, 3);
write_csr(mstatus, ms);
ms = read_csr(mstatus);
if (EXTRACT_FIELD(ms, MSTATUS_VM) != VM_CHOICE) {
printk(BIOS_DEBUG, "we don't have virtual memory...\n");
} else {
printk(BIOS_DEBUG, "-----------------------------\n");
printk(BIOS_DEBUG, "virtual memory status enabled\n");
printk(BIOS_DEBUG, "-----------------------------\n");
}
clear_csr(mip, MIP_MSIP);
set_csr(mie, MIP_MSIP);
}
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