dingusppc/cpu/ppc/ppcmmu.cpp

//DingusPPC
//Written by divingkatae and maximum
//(c)2018-20 (theweirdo)     spatium
//Please ask for permission
//if you want to distribute this.
//(divingkatae#1017 or powermax#2286 on Discord)

/** @file PowerPC Memory management unit emulation. */

/* TODO:
    - implement TLB
    - implement 601-style BATs
    - implement BAT access check
    - add proper error and exception handling
    - clarify what to do in the case of unaligned memory accesses
    - remove dependency on MPC106 (use generic memory controller interface instead)
 */

#include <iostream>
#include <cstdint>
#include <cinttypes>
#include <string>
#include <array>
#include "memreadwrite.h"
#include "ppcemu.h"
#include "ppcmmu.h"
#include "devices/memctrlbase.h"
#include "devices/mmiodevice.h"
#include "devices/mpc106.h"


/** PowerPC-style MMU BAT arrays (NULL initialization isn't prescribed). */
PPC_BAT_entry ibat_array[4] = {{0}};
PPC_BAT_entry dbat_array[4] = {{0}};

void ppc_set_cur_instruction(const uint8_t *ptr)
{
    ppc_cur_instruction = READ_DWORD_BE_A(ptr);
}

static inline void ppc_set_return_val(const uint8_t *ptr, int num_size)
{
    //Put the final result in return_value here
    //This is what gets put back into the register

    if (num_size == 1) { // BYTE
        return_value = ptr[0];
    }

    if (ppc_state.ppc_msr & 1) { /* little-endian byte ordering */
        if (num_size == 2) { // WORD
            return_value = READ_WORD_LE_A(ptr);
        }
        else if (num_size == 4) { // DWORD
            return_value = READ_DWORD_LE_A(ptr);
        }
    } else { /* big-endian byte ordering */
        if (num_size == 2) { // WORD
            return_value = READ_WORD_BE_A(ptr);
        }
        else if (num_size == 4) { // DWORD
            return_value = READ_DWORD_BE_A(ptr);
        }
    }
}

static inline void ppc_memstore_value(unsigned char *ptr, uint32_t value,
                                      uint32_t offset, int num_size)
{
    if (ppc_state.ppc_msr & 1) { /* little-endian byte ordering */
        if (num_size >= 1) { // BYTE
            ptr[offset] = value & 0xFF;
        }
        if (num_size >= 2) { // WORD
            ptr[offset+1] = (value >> 8) & 0xFF;
        }
        if (num_size == 4) { // DWORD
            ptr[offset+2] = (value >> 16) & 0xFF;
            ptr[offset+3] = (value >> 24) & 0xFF;
        }
    } else { /* big-endian byte ordering */
        if (num_size == 1) { // BYTE
            ptr[offset] = value & 0xFF;
        }
        else if (num_size == 2) { // WORD
            ptr[offset]   = (value >> 8) & 0xFF;
            ptr[offset+1] = value & 0xFF;
        }
        else if (num_size == 4) { // DWORD
            ptr[offset]   = (value >> 24) & 0xFF;
            ptr[offset+1] = (value >> 16) & 0xFF;
            ptr[offset+2] = (value >> 8)  & 0xFF;
            ptr[offset+3] = value & 0xFF;
        }
    }
}

void ibat_update(uint32_t bat_reg)
{
    int upper_reg_num;
    uint32_t bl, lo_mask;
    PPC_BAT_entry *bat_entry;

    upper_reg_num = bat_reg & 0xFFFFFFFE;

    if (ppc_state.ppc_spr[upper_reg_num] & 3) { // is that BAT pair valid?
        bat_entry = &ibat_array[(bat_reg - 528) >> 1];
        bl = (ppc_state.ppc_spr[upper_reg_num] >> 2) & 0x7FF;
        lo_mask = (bl << 17) | 0x1FFFF;

        bat_entry->access  = ppc_state.ppc_spr[upper_reg_num] & 3;
        bat_entry->prot    = ppc_state.ppc_spr[upper_reg_num + 1] & 3;
        bat_entry->lo_mask = lo_mask;
        bat_entry->phys_hi = ppc_state.ppc_spr[upper_reg_num + 1] & ~lo_mask;
        bat_entry->bepi    = ppc_state.ppc_spr[upper_reg_num] & ~lo_mask;
    }
}

void dbat_update(uint32_t bat_reg)
{
    int upper_reg_num;
    uint32_t bl, lo_mask;
    PPC_BAT_entry *bat_entry;

    upper_reg_num = bat_reg & 0xFFFFFFFE;

    if (ppc_state.ppc_spr[upper_reg_num] & 3) { // is that BAT pair valid?
        bat_entry = &dbat_array[(bat_reg - 536) >> 1];
        bl = (ppc_state.ppc_spr[upper_reg_num] >> 2) & 0x7FF;
        lo_mask = (bl << 17) | 0x1FFFF;

        bat_entry->access  = ppc_state.ppc_spr[upper_reg_num] & 3;
        bat_entry->prot    = ppc_state.ppc_spr[upper_reg_num + 1] & 3;
        bat_entry->lo_mask = lo_mask;
        bat_entry->phys_hi = ppc_state.ppc_spr[upper_reg_num + 1] & ~lo_mask;
        bat_entry->bepi    = ppc_state.ppc_spr[upper_reg_num] & ~lo_mask;
    }
}

/* remember page table memory region for quicker translation. */
uint32_t page_table_pa_start  = 0;
uint32_t page_table_pa_end    = 0;
unsigned char *page_table_ptr = 0;

static inline uint8_t *calc_pteg_addr(uint32_t hash)
{
    uint32_t sdr1_val, pteg_addr;

    sdr1_val = ppc_state.ppc_spr[25];

    pteg_addr = sdr1_val & 0xFE000000;
    pteg_addr |= (sdr1_val & 0x01FF0000) |
                    (((sdr1_val & 0x1FF) << 16) & ((hash & 0x7FC00) << 6));
    pteg_addr |= (hash & 0x3FF) << 6;

    if (pteg_addr >= page_table_pa_start && pteg_addr <= page_table_pa_end) {
        return page_table_ptr + (pteg_addr - page_table_pa_start);
    } else {
        AddressMapEntry *entry = mem_ctrl_instance->find_range(pteg_addr);
        if (entry && entry->type & (RT_ROM | RT_RAM)) {
            page_table_pa_start = entry->start;
            page_table_pa_end   = entry->end;
            page_table_ptr      = entry->mem_ptr;
            return page_table_ptr + (pteg_addr - page_table_pa_start);
        } else {
            printf("SOS: no page table region was found at %08X!\n", pteg_addr);
            exit(-1); // FIXME: ugly error handling, must be the proper exception!
        }
    }
}

static bool search_pteg(uint8_t *pteg_addr, uint8_t **ret_pte_addr,
                        uint32_t vsid, uint16_t page_index, uint8_t pteg_num)
{
    /* construct PTE matching word */
    uint32_t pte_check = 0x80000000 | (vsid << 7) | (pteg_num << 6) |
                        (page_index >> 10);

#ifdef MMU_INTEGRITY_CHECKS
    /* PTEG integrity check that ensures that all matching PTEs have
       identical RPN, WIMG and PP bits (PPC PEM 32-bit 7.6.2, rule 5). */
    uint32_t pte_word2_check;
    bool match_found = false;

    for (int i = 0; i < 8; i++, pteg_addr += 8) {
        if (pte_check == READ_DWORD_BE_A(pteg_addr)) {
            if (match_found) {
                if ((READ_DWORD_BE_A(pteg_addr) & 0xFFFFF07B) != pte_word2_check) {
                    printf("Multiple PTEs with different RPN/WIMG/PP found!\n");
                    exit(-1);
                }
            } else {
                /* isolate RPN, WIMG and PP fields */
                pte_word2_check = READ_DWORD_BE_A(pteg_addr) & 0xFFFFF07B;
                *ret_pte_addr = pteg_addr;
            }
        }
    }
#else
    for (int i = 0; i < 8; i++, pteg_addr += 8) {
        if (pte_check == READ_DWORD_BE_A(pteg_addr)) {
            *ret_pte_addr = pteg_addr;
            return true;
        }
    }
#endif

    return false;
}

static uint32_t page_address_translate(uint32_t la, bool is_instr_fetch,
                                       unsigned msr_pr, int is_write)
{
    uint32_t sr_val, page_index, pteg_hash1, vsid, pte_word2;
    unsigned key, pp;
    uint8_t *pte_addr;

    sr_val = ppc_state.ppc_sr[(la >> 28) & 0x0F];
    if (sr_val & 0x80000000) {
        printf("Direct-store segments not supported, LA=%0xX\n", la);
        exit(-1); // FIXME: ugly error handling, must be the proper exception!
    }

    /* instruction fetch from a no-execute segment will cause ISI exception */
    if ((sr_val & 0x10000000) && is_instr_fetch) {
        ppc_exception_handler(Except_Type::EXC_ISI, 0x10000000);
    }

    page_index = (la >> 12) & 0xFFFF;
    pteg_hash1 = (sr_val & 0x7FFFF) ^ page_index;
    vsid = sr_val & 0x0FFFFFF;

    if (!search_pteg(calc_pteg_addr(pteg_hash1), &pte_addr, vsid, page_index, 0)) {
        if (!search_pteg(calc_pteg_addr(~pteg_hash1), &pte_addr, vsid, page_index, 1)) {
            if (is_instr_fetch) {
                ppc_exception_handler(Except_Type::EXC_ISI, 0x40000000);
            } else {
                ppc_state.ppc_spr[18] = 0x40000000 | (is_write << 25);
                ppc_state.ppc_spr[19] = la;
                ppc_exception_handler(Except_Type::EXC_DSI, 0);
            }
        }
    }

    pte_word2 = READ_DWORD_BE_A(pte_addr + 4);

    key = (((sr_val >> 29) & 1) & msr_pr) | (((sr_val >> 30) & 1) & (msr_pr ^ 1));

    /* check page access */
    pp = pte_word2 & 3;

    // the following scenarios cause DSI/ISI exception:
    // any access with key = 1 and PP = %00
    // write access with key = 1 and PP = %01
    // write access with PP = %11
    if ((key && (!pp || (pp == 1 && is_write))) || (pp == 3 && is_write)) {
        if (is_instr_fetch) {
            ppc_exception_handler(Except_Type::EXC_ISI, 0x08000000);
        } else {
            ppc_state.ppc_spr[18] = 0x08000000 | (is_write << 25);
            ppc_state.ppc_spr[19] = la;
            ppc_exception_handler(Except_Type::EXC_DSI, 0);
        }
    }

    /* update R and C bits */
    /* For simplicity, R is set on each access, C is set only for writes */
    pte_addr[6] |= 0x01;
    if (is_write) {
        pte_addr[7] |= 0x80;
    }

    /* return physical address */
    return ((pte_word2 & 0xFFFFF000) | (la & 0x00000FFF));
}

/** PowerPC-style MMU instruction address translation. */
static uint32_t ppc_mmu_instr_translate(uint32_t la)
{
    uint32_t pa; /* translated physical address */

    bool bat_hit = false;
    unsigned msr_pr = !!(ppc_state.ppc_msr & 0x4000);

    // Format: %XY
    // X - supervisor access bit, Y - problem/user access bit
    // Those bits are mutually exclusive
    unsigned access_bits = (~msr_pr << 1) | msr_pr;

    for (int bat_index = 0; bat_index < 4; bat_index++){
        PPC_BAT_entry *bat_entry = &ibat_array[bat_index];

        if ((bat_entry->access & access_bits) &&
            ((la & ~bat_entry->lo_mask) == bat_entry->bepi)) {
            bat_hit = true;
            // TODO: check access

            // logical to physical translation
            pa = bat_entry->phys_hi | (la & bat_entry->lo_mask);
            break;
        }
    }

    /* page address translation */
    if (!bat_hit) {
        pa = page_address_translate(la, true, msr_pr, 0);
    }

    return pa;
}

/** PowerPC-style MMU data address translation. */
static uint32_t ppc_mmu_addr_translate(uint32_t la, int is_write)
{
#if PROFILER
    mmu_translations_num++;
#endif

    uint32_t pa; /* translated physical address */

    bool bat_hit = false;
    unsigned msr_pr = !!(ppc_state.ppc_msr & 0x4000);

    // Format: %XY
    // X - supervisor access bit, Y - problem/user access bit
    // Those bits are mutually exclusive
    unsigned access_bits = (~msr_pr << 1) | msr_pr;

    for (int bat_index = 0; bat_index < 4; bat_index++){
        PPC_BAT_entry *bat_entry = &dbat_array[bat_index];

        if ((bat_entry->access & access_bits) &&
            ((la & ~bat_entry->lo_mask) == bat_entry->bepi)) {
            bat_hit = true;
            // TODO: check access

            // logical to physical translation
            pa = bat_entry->phys_hi | (la & bat_entry->lo_mask);
            break;
        }
    }

    /* page address translation */
    if (!bat_hit) {
        pa = page_address_translate(la, false, msr_pr, is_write);
    }

    return pa;
}


uint32_t write_last_pa_start  = 0;
uint32_t write_last_pa_end    = 0;
unsigned char *write_last_ptr = 0;

void address_quickinsert_translate(uint32_t value, uint32_t addr, uint8_t num_bytes)
{
    /* data address translation if enabled */
    if (ppc_state.ppc_msr & 0x10) {
        addr = ppc_mmu_addr_translate(addr, 1);
    }

    if (addr >= write_last_pa_start && addr <= write_last_pa_end) {
        ppc_memstore_value(write_last_ptr, value, addr - write_last_pa_start, num_bytes);
    } else {
        AddressMapEntry *entry = mem_ctrl_instance->find_range(addr);
        if (entry) {
            if (entry->type & RT_RAM) {
                write_last_pa_start = entry->start;
                write_last_pa_end   = entry->end;
                write_last_ptr = entry->mem_ptr;
                ppc_memstore_value(write_last_ptr, value, addr - entry->start, num_bytes);
            } else if (entry->type & RT_MMIO) {
                entry->devobj->write(addr - entry->start, value, num_bytes);
            } else {
                printf("Please check your address map!\n");
            }
        } else {
            printf("WARNING: write attempt to unmapped memory at 0x%08X!\n", addr);
        }
    }
}


uint32_t read_last_pa_start  = 0;
uint32_t read_last_pa_end    = 0;
unsigned char *read_last_ptr = 0;

/** Grab a value from memory into a register */
void address_quickgrab_translate(uint32_t addr, uint8_t num_bytes)
{
    /* data address translation if enabled */
    if (ppc_state.ppc_msr & 0x10) {
        addr = ppc_mmu_addr_translate(addr, 0);
    }

    if (addr >= read_last_pa_start && addr <= read_last_pa_end) {
        ppc_set_return_val(read_last_ptr + (addr - read_last_pa_start), num_bytes);
    } else {
        AddressMapEntry *entry = mem_ctrl_instance->find_range(addr);
        if (entry) {
            if (entry->type & (RT_ROM | RT_RAM)) {
                read_last_pa_start = entry->start;
                read_last_pa_end   = entry->end;
                read_last_ptr = entry->mem_ptr;
                ppc_set_return_val(read_last_ptr + (addr - entry->start), num_bytes);
            } else if (entry->type & RT_MMIO) {
                return_value = entry->devobj->read(addr - entry->start, num_bytes);
            } else {
                printf("Please check your address map!\n");
            }
        } else {
            printf("WARNING: read attempt from unmapped memory at 0x%08X!\n", addr);

            /* reading from unmapped memory will return unmapped value */
            for (return_value = 0xFF; --num_bytes > 0;)
                return_value = (return_value << 8) | 0xFF;
        }
    }
}

/* remember recently used memory region for quicker translation. */
uint32_t exec_last_pa_start  = 0;
uint32_t exec_last_pa_end    = 0;
unsigned char *exec_last_ptr = 0;

uint8_t *quickinstruction_translate(uint32_t addr)
{
    uint8_t *real_addr;

    /* perform instruction address translation if enabled */
    if (ppc_state.ppc_msr & 0x20) {
        addr = ppc_mmu_instr_translate(addr);
    }

    if (addr >= exec_last_pa_start && addr <= exec_last_pa_end) {
        real_addr = exec_last_ptr + (addr - exec_last_pa_start);
        ppc_set_cur_instruction(real_addr);
    } else {
        AddressMapEntry *entry = mem_ctrl_instance->find_range(addr);
        if (entry && entry->type & (RT_ROM | RT_RAM)) {
            exec_last_pa_start = entry->start;
            exec_last_pa_end   = entry->end;
            exec_last_ptr = entry->mem_ptr;
            real_addr = exec_last_ptr + (addr - exec_last_pa_start);
            ppc_set_cur_instruction(real_addr);
        } else {
            printf("WARNING: attempt to execute code at %08X!\n", addr);
            exit(-1); // FIXME: ugly error handling, must be the proper exception!
        }
    }

    return real_addr;
}