arm_simulator.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
/***************************************************************************
 *   Copyright (C) 2006 by Dominic Rath                                    *
 *   Dominic.Rath@gmx.de                                                   *
 *                                                                         *
 *   Copyright (C) 2008 by Hongtao Zheng                                   *
 *   hontor@126.com                                                        *
 ***************************************************************************/
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include "arm.h"
#include "armv4_5.h"
#include "arm_disassembler.h"
#include "arm_simulator.h"
#include <helper/binarybuffer.h>
#include "register.h"
#include <helper/log.h>
 
static uint32_t arm_shift(uint8_t shift, uint32_t rm,
    uint32_t shift_amount, uint8_t *carry)
{
    uint32_t return_value = 0;
    shift_amount &= 0xff;
 
    if (shift == 0x0) { /* LSL */
        if (shift_amount > 0 && shift_amount < 32) {
            return_value = rm << shift_amount;
            *carry = rm >> (32 - shift_amount);
        } else if (shift_amount == 32) {
            return_value = 0x0;
            *carry = rm & 0x1;
        } else if (shift_amount > 32) {
            return_value = 0x0;
            *carry = 0x0;
        } else /* (shift_amount == 0) */
            return_value = rm;
    } else if (shift == 0x1) {  /* LSR */
        if (shift_amount > 0 && shift_amount < 32) {
            return_value = rm >> shift_amount;
            *carry = (rm >> (shift_amount - 1)) & 1;
        } else if (shift_amount == 32) {
            return_value = 0x0;
            *carry = (rm >> 31) & 0x1;
        } else if (shift_amount > 32) {
            return_value = 0x0;
            *carry = 0x0;
        } else /* (shift_amount == 0) */
            return_value = rm;
    } else if (shift == 0x2) {  /* ASR */
        if (shift_amount > 0 && shift_amount < 32) {
            /* C right shifts of unsigned values are guaranteed to
             * be logical (shift in zeroes); simulate an arithmetic
             * shift (shift in signed-bit) by adding the sign bit
             * manually
             */
            return_value = rm >> shift_amount;
            if (rm & 0x80000000)
                return_value |= 0xffffffff << (32 - shift_amount);
        } else if (shift_amount >= 32) {
            if (rm & 0x80000000) {
                return_value = 0xffffffff;
                *carry = 0x1;
            } else {
                return_value = 0x0;
                *carry = 0x0;
            }
        } else /* (shift_amount == 0) */
            return_value = rm;
    } else if (shift == 0x3) {  /* ROR */
        if (shift_amount == 0)
            return_value = rm;
        else {
            shift_amount = shift_amount % 32;
            return_value = (rm >> shift_amount) | (rm << (32 - shift_amount));
            *carry = (return_value >> 31) & 0x1;
        }
    } else if (shift == 0x4) {  /* RRX */
        return_value = rm >> 1;
        if (*carry)
            rm |= 0x80000000;
        *carry = rm & 0x1;
    }
 
    return return_value;
}
 
 
static uint32_t arm_shifter_operand(struct arm_sim_interface *sim,
    int variant, union arm_shifter_operand shifter_operand,
    uint8_t *shifter_carry_out)
{
    uint32_t return_value;
    int instruction_size;
 
    if (sim->get_state(sim) == ARM_STATE_ARM)
        instruction_size = 4;
    else
        instruction_size = 2;
 
    *shifter_carry_out = sim->get_cpsr(sim, 29, 1);
 
    if (variant == 0) /* 32-bit immediate */
        return_value = shifter_operand.immediate.immediate;
    else if (variant == 1) {/* immediate shift */
        uint32_t rm = sim->get_reg_mode(sim, shifter_operand.immediate_shift.rm);
 
        /* adjust RM in case the PC is being read */
        if (shifter_operand.immediate_shift.rm == 15)
            rm += 2 * instruction_size;
 
        return_value = arm_shift(shifter_operand.immediate_shift.shift,
                rm, shifter_operand.immediate_shift.shift_imm,
                shifter_carry_out);
    } else if (variant == 2) {  /* register shift */
        uint32_t rm = sim->get_reg_mode(sim, shifter_operand.register_shift.rm);
        uint32_t rs = sim->get_reg_mode(sim, shifter_operand.register_shift.rs);
 
        /* adjust RM in case the PC is being read */
        if (shifter_operand.register_shift.rm == 15)
            rm += 2 * instruction_size;
 
        return_value = arm_shift(shifter_operand.immediate_shift.shift,
                rm, rs, shifter_carry_out);
    } else {
        LOG_ERROR("BUG: shifter_operand.variant not 0, 1 or 2");
        return_value = 0xffffffff;
    }
 
    return return_value;
}
 
static int pass_condition(uint32_t cpsr, uint32_t opcode)
{
    switch ((opcode & 0xf0000000) >> 28) {
    case 0x0:   /* EQ */
        if (cpsr & 0x40000000)
            return 1;
        else
            return 0;
    case 0x1:   /* NE */
        if (!(cpsr & 0x40000000))
            return 1;
        else
            return 0;
    case 0x2:   /* CS */
        if (cpsr & 0x20000000)
            return 1;
        else
            return 0;
    case 0x3:   /* CC */
        if (!(cpsr & 0x20000000))
            return 1;
        else
            return 0;
    case 0x4:   /* MI */
        if (cpsr & 0x80000000)
            return 1;
        else
            return 0;
    case 0x5:   /* PL */
        if (!(cpsr & 0x80000000))
            return 1;
        else
            return 0;
    case 0x6:   /* VS */
        if (cpsr & 0x10000000)
            return 1;
        else
            return 0;
    case 0x7:   /* VC */
        if (!(cpsr & 0x10000000))
            return 1;
        else
            return 0;
    case 0x8:   /* HI */
        if ((cpsr & 0x20000000) && !(cpsr & 0x40000000))
            return 1;
        else
            return 0;
    case 0x9:   /* LS */
        if (!(cpsr & 0x20000000) || (cpsr & 0x40000000))
            return 1;
        else
            return 0;
    case 0xa:   /* GE */
        if (((cpsr & 0x80000000) && (cpsr & 0x10000000))
            || (!(cpsr & 0x80000000) && !(cpsr & 0x10000000)))
            return 1;
        else
            return 0;
    case 0xb:   /* LT */
        if (((cpsr & 0x80000000) && !(cpsr & 0x10000000))
            || (!(cpsr & 0x80000000) && (cpsr & 0x10000000)))
            return 1;
        else
            return 0;
    case 0xc:   /* GT */
        if (!(cpsr & 0x40000000) &&
            (((cpsr & 0x80000000) && (cpsr & 0x10000000))
            || (!(cpsr & 0x80000000) && !(cpsr & 0x10000000))))
            return 1;
        else
            return 0;
    case 0xd:   /* LE */
        if ((cpsr & 0x40000000) ||
            ((cpsr & 0x80000000) && !(cpsr & 0x10000000))
            || (!(cpsr & 0x80000000) && (cpsr & 0x10000000)))
            return 1;
        else
            return 0;
    case 0xe:
    case 0xf:
        return 1;
    }
 
    LOG_ERROR("BUG: should never get here");
    return 0;
}
 
static int thumb_pass_branch_condition(uint32_t cpsr, uint16_t opcode)
{
    return pass_condition(cpsr, (opcode & 0x0f00) << 20);
}
 
/* simulate a single step (if possible)
 * if the dry_run_pc argument is provided, no state is changed,
 * but the new pc is stored in the variable pointed at by the argument
 */
static int arm_simulate_step_core(struct target *target,
    uint32_t *dry_run_pc, struct arm_sim_interface *sim)
{
    uint32_t current_pc = sim->get_reg(sim, 15);
    struct arm_instruction instruction;
    int instruction_size;
    int retval = ERROR_OK;
 
    if (sim->get_state(sim) == ARM_STATE_ARM) {
        uint32_t opcode;
 
        /* get current instruction, and identify it */
        retval = target_read_u32(target, current_pc, &opcode);
        if (retval != ERROR_OK)
            return retval;
        retval = arm_evaluate_opcode(opcode, current_pc, &instruction);
        if (retval != ERROR_OK)
            return retval;
        instruction_size = 4;
 
        /* check condition code (for all instructions) */
        if (!pass_condition(sim->get_cpsr(sim, 0, 32), opcode)) {
            if (dry_run_pc)
                *dry_run_pc = current_pc + instruction_size;
            else
                sim->set_reg(sim, 15, current_pc + instruction_size);
 
            return ERROR_OK;
        }
    } else {
        uint16_t opcode;
 
        retval = target_read_u16(target, current_pc, &opcode);
        if (retval != ERROR_OK)
            return retval;
        retval = thumb_evaluate_opcode(opcode, current_pc, &instruction);
        if (retval != ERROR_OK)
            return retval;
        instruction_size = 2;
 
        /* check condition code (only for branch (1) instructions) */
        if ((opcode & 0xf000) == 0xd000
            && !thumb_pass_branch_condition(
            sim->get_cpsr(sim, 0, 32), opcode)) {
            if (dry_run_pc)
                *dry_run_pc = current_pc + instruction_size;
            else
                sim->set_reg(sim, 15, current_pc + instruction_size);
 
            return ERROR_OK;
        }
 
        /* Deal with 32-bit BL/BLX */
        if ((opcode & 0xf800) == 0xf000) {
            uint32_t high = instruction.info.b_bl_bx_blx.target_address;
            retval = target_read_u16(target, current_pc+2, &opcode);
            if (retval != ERROR_OK)
                return retval;
            retval = thumb_evaluate_opcode(opcode, current_pc, &instruction);
            if (retval != ERROR_OK)
                return retval;
            instruction.info.b_bl_bx_blx.target_address += high;
        }
    }
 
    /* examine instruction type */
 
    /* branch instructions */
    if ((instruction.type >= ARM_B) && (instruction.type <= ARM_BLX)) {
        uint32_t target_address;
 
        if (instruction.info.b_bl_bx_blx.reg_operand == -1)
            target_address = instruction.info.b_bl_bx_blx.target_address;
        else {
            target_address = sim->get_reg_mode(sim,
                    instruction.info.b_bl_bx_blx.reg_operand);
            if (instruction.info.b_bl_bx_blx.reg_operand == 15)
                target_address += 2 * instruction_size;
        }
 
        if (dry_run_pc) {
            *dry_run_pc = target_address & ~1;
            return ERROR_OK;
        } else {
            if (instruction.type == ARM_B)
                sim->set_reg(sim, 15, target_address);
            else if (instruction.type == ARM_BL) {
                uint32_t old_pc = sim->get_reg(sim, 15);
                int t = (sim->get_state(sim) == ARM_STATE_THUMB);
                sim->set_reg_mode(sim, 14, old_pc + 4 + t);
                sim->set_reg(sim, 15, target_address);
            } else if (instruction.type == ARM_BX) {
                if (target_address & 0x1)
                    sim->set_state(sim, ARM_STATE_THUMB);
                else
                    sim->set_state(sim, ARM_STATE_ARM);
                sim->set_reg(sim, 15, target_address & 0xfffffffe);
            } else if (instruction.type == ARM_BLX) {
                uint32_t old_pc = sim->get_reg(sim, 15);
                int t = (sim->get_state(sim) == ARM_STATE_THUMB);
                sim->set_reg_mode(sim, 14, old_pc + 4 + t);
 
                if (target_address & 0x1)
                    sim->set_state(sim, ARM_STATE_THUMB);
                else
                    sim->set_state(sim, ARM_STATE_ARM);
                sim->set_reg(sim, 15, target_address & 0xfffffffe);
            }
 
            return ERROR_OK;
        }
    }
    /* data processing instructions, except compare instructions (CMP, CMN, TST, TEQ) */
    else if (((instruction.type >= ARM_AND) && (instruction.type <= ARM_RSC))
        || ((instruction.type >= ARM_ORR) && (instruction.type <= ARM_MVN))) {
        uint32_t rd, rn, shifter_operand;
        uint8_t c = sim->get_cpsr(sim, 29, 1);
        uint8_t carry_out;
 
        rd = 0x0;
        /* ARM_MOV and ARM_MVN does not use Rn */
        if ((instruction.type != ARM_MOV) && (instruction.type != ARM_MVN))
            rn = sim->get_reg_mode(sim, instruction.info.data_proc.rn);
        else
            rn = 0;
 
        shifter_operand = arm_shifter_operand(sim,
                instruction.info.data_proc.variant,
                instruction.info.data_proc.shifter_operand,
                &carry_out);
 
        /* adjust Rn in case the PC is being read */
        if (instruction.info.data_proc.rn == 15)
            rn += 2 * instruction_size;
 
        if (instruction.type == ARM_AND)
            rd = rn & shifter_operand;
        else if (instruction.type == ARM_EOR)
            rd = rn ^ shifter_operand;
        else if (instruction.type == ARM_SUB)
            rd = rn - shifter_operand;
        else if (instruction.type == ARM_RSB)
            rd = shifter_operand - rn;
        else if (instruction.type == ARM_ADD)
            rd = rn + shifter_operand;
        else if (instruction.type == ARM_ADC)
            rd = rn + shifter_operand + (c & 1);
        else if (instruction.type == ARM_SBC)
            rd = rn - shifter_operand - (c & 1) ? 0 : 1;
        else if (instruction.type == ARM_RSC)
            rd = shifter_operand - rn - (c & 1) ? 0 : 1;
        else if (instruction.type == ARM_ORR)
            rd = rn | shifter_operand;
        else if (instruction.type == ARM_BIC)
            rd = rn & ~(shifter_operand);
        else if (instruction.type == ARM_MOV)
            rd = shifter_operand;
        else if (instruction.type == ARM_MVN)
            rd = ~shifter_operand;
        else
            LOG_WARNING("unhandled instruction type");
 
        if (dry_run_pc) {
            if (instruction.info.data_proc.rd == 15)
                *dry_run_pc = rd & ~1;
            else
                *dry_run_pc = current_pc + instruction_size;
 
            return ERROR_OK;
        } else {
            if (instruction.info.data_proc.rd == 15) {
                sim->set_reg_mode(sim, 15, rd & ~1);
                if (rd & 1)
                    sim->set_state(sim, ARM_STATE_THUMB);
                else
                    sim->set_state(sim, ARM_STATE_ARM);
                return ERROR_OK;
            }
            sim->set_reg_mode(sim, instruction.info.data_proc.rd, rd);
            LOG_WARNING("no updating of flags yet");
        }
    }
    /* compare instructions (CMP, CMN, TST, TEQ) */
    else if ((instruction.type >= ARM_TST) && (instruction.type <= ARM_CMN)) {
        if (dry_run_pc) {
            *dry_run_pc = current_pc + instruction_size;
            return ERROR_OK;
        } else
            LOG_WARNING("no updating of flags yet");
    }
    /* load register instructions */
    else if ((instruction.type >= ARM_LDR) && (instruction.type <= ARM_LDRSH)) {
        uint32_t load_address = 0, modified_address = 0, load_value = 0;
        uint32_t rn = sim->get_reg_mode(sim, instruction.info.load_store.rn);
 
        /* adjust Rn in case the PC is being read */
        if (instruction.info.load_store.rn == 15)
            rn += 2 * instruction_size;
 
        if (instruction.info.load_store.offset_mode == 0) {
            if (instruction.info.load_store.u)
                modified_address = rn + instruction.info.load_store.offset.offset;
            else
                modified_address = rn - instruction.info.load_store.offset.offset;
        } else if (instruction.info.load_store.offset_mode == 1) {
            uint32_t offset;
            uint32_t rm = sim->get_reg_mode(sim,
                    instruction.info.load_store.offset.reg.rm);
            uint8_t shift = instruction.info.load_store.offset.reg.shift;
            uint8_t shift_imm = instruction.info.load_store.offset.reg.shift_imm;
            uint8_t carry = sim->get_cpsr(sim, 29, 1);
 
            offset = arm_shift(shift, rm, shift_imm, &carry);
 
            if (instruction.info.load_store.u)
                modified_address = rn + offset;
            else
                modified_address = rn - offset;
        } else
            LOG_ERROR("BUG: offset_mode neither 0 (offset) nor 1 (scaled register)");
 
        if (instruction.info.load_store.index_mode == 0) {
            /* offset mode
             * we load from the modified address, but don't change
             * the base address register
             */
            load_address = modified_address;
            modified_address = rn;
        } else if (instruction.info.load_store.index_mode == 1) {
            /* pre-indexed mode
             * we load from the modified address, and write it
             * back to the base address register
             */
            load_address = modified_address;
        } else if (instruction.info.load_store.index_mode == 2) {
            /* post-indexed mode
             * we load from the unmodified address, and write the
             * modified address back
             */
            load_address = rn;
        }
 
        if ((!dry_run_pc) || (instruction.info.load_store.rd == 15)) {
            retval = target_read_u32(target, load_address, &load_value);
            if (retval != ERROR_OK)
                return retval;
        }
 
        if (dry_run_pc) {
            if (instruction.info.load_store.rd == 15)
                *dry_run_pc = load_value & ~1;
            else
                *dry_run_pc = current_pc + instruction_size;
            return ERROR_OK;
        } else {
            if ((instruction.info.load_store.index_mode == 1) ||
                (instruction.info.load_store.index_mode == 2))
                sim->set_reg_mode(sim,
                    instruction.info.load_store.rn,
                    modified_address);
 
            if (instruction.info.load_store.rd == 15) {
                sim->set_reg_mode(sim, 15, load_value & ~1);
                if (load_value & 1)
                    sim->set_state(sim, ARM_STATE_THUMB);
                else
                    sim->set_state(sim, ARM_STATE_ARM);
                return ERROR_OK;
            }
            sim->set_reg_mode(sim, instruction.info.load_store.rd, load_value);
        }
    }
    /* load multiple instruction */
    else if (instruction.type == ARM_LDM) {
        int i;
        uint32_t rn = sim->get_reg_mode(sim, instruction.info.load_store_multiple.rn);
        uint32_t load_values[16];
        int bits_set = 0;
 
        for (i = 0; i < 16; i++) {
            if (instruction.info.load_store_multiple.register_list & (1 << i))
                bits_set++;
        }
 
        switch (instruction.info.load_store_multiple.addressing_mode) {
        case 0: /* Increment after */
            /* rn = rn; */
            break;
        case 1: /* Increment before */
            rn = rn + 4;
            break;
        case 2: /* Decrement after */
            rn = rn - (bits_set * 4) + 4;
            break;
        case 3: /* Decrement before */
            rn = rn - (bits_set * 4);
            break;
        }
 
        for (i = 0; i < 16; i++) {
            if (instruction.info.load_store_multiple.register_list & (1 << i)) {
                if ((!dry_run_pc) || (i == 15))
                    target_read_u32(target, rn, &load_values[i]);
                rn += 4;
            }
        }
 
        if (dry_run_pc) {
            if (instruction.info.load_store_multiple.register_list & 0x8000) {
                *dry_run_pc = load_values[15] & ~1;
                return ERROR_OK;
            }
        } else {
            int update_cpsr = 0;
 
            if (instruction.info.load_store_multiple.s) {
                if (instruction.info.load_store_multiple.register_list & 0x8000)
                    update_cpsr = 1;
            }
 
            for (i = 0; i < 16; i++) {
                if (instruction.info.load_store_multiple.register_list & (1 << i)) {
                    if (i == 15) {
                        uint32_t val = load_values[i];
                        sim->set_reg_mode(sim, i, val & ~1);
                        if (val & 1)
                            sim->set_state(sim, ARM_STATE_THUMB);
                        else
                            sim->set_state(sim, ARM_STATE_ARM);
                    } else
                        sim->set_reg_mode(sim, i, load_values[i]);
                }
            }
 
            if (update_cpsr) {
                uint32_t spsr = sim->get_reg_mode(sim, 16);
                sim->set_reg(sim, ARMV4_5_CPSR, spsr);
            }
 
            /* base register writeback */
            if (instruction.info.load_store_multiple.w)
                sim->set_reg_mode(sim, instruction.info.load_store_multiple.rn, rn);
 
 
            if (instruction.info.load_store_multiple.register_list & 0x8000)
                return ERROR_OK;
        }
    }
    /* store multiple instruction */
    else if (instruction.type == ARM_STM) {
        int i;
 
        if (dry_run_pc) {
            /* STM wont affect PC (advance by instruction size */
        } else {
            uint32_t rn = sim->get_reg_mode(sim,
                    instruction.info.load_store_multiple.rn);
            int bits_set = 0;
 
            for (i = 0; i < 16; i++) {
                if (instruction.info.load_store_multiple.register_list & (1 << i))
                    bits_set++;
            }
 
            switch (instruction.info.load_store_multiple.addressing_mode) {
            case 0: /* Increment after */
                /* rn = rn; */
                break;
            case 1: /* Increment before */
                rn = rn + 4;
                break;
            case 2: /* Decrement after */
                rn = rn - (bits_set * 4) + 4;
                break;
            case 3: /* Decrement before */
                rn = rn - (bits_set * 4);
                break;
            }
 
            for (i = 0; i < 16; i++) {
                if (instruction.info.load_store_multiple.register_list & (1 << i)) {
                    target_write_u32(target, rn, sim->get_reg_mode(sim, i));
                    rn += 4;
                }
            }
 
            /* base register writeback */
            if (instruction.info.load_store_multiple.w)
                sim->set_reg_mode(sim,
                    instruction.info.load_store_multiple.rn, rn);
 
        }
    } else if (!dry_run_pc) {
        /* the instruction wasn't handled, but we're supposed to simulate it
         */
        LOG_ERROR("Unimplemented instruction, could not simulate it.");
        return ERROR_FAIL;
    }
 
    if (dry_run_pc) {
        *dry_run_pc = current_pc + instruction_size;
        return ERROR_OK;
    } else {
        sim->set_reg(sim, 15, current_pc + instruction_size);
        return ERROR_OK;
    }
 
}
 
static uint32_t armv4_5_get_reg(struct arm_sim_interface *sim, int reg)
{
    struct arm *arm = (struct arm *)sim->user_data;
 
    return buf_get_u32(arm->core_cache->reg_list[reg].value, 0, 32);
}
 
static void armv4_5_set_reg(struct arm_sim_interface *sim, int reg, uint32_t value)
{
    struct arm *arm = (struct arm *)sim->user_data;
 
    buf_set_u32(arm->core_cache->reg_list[reg].value, 0, 32, value);
}
 
static uint32_t armv4_5_get_reg_mode(struct arm_sim_interface *sim, int reg)
{
    struct arm *arm = (struct arm *)sim->user_data;
 
    return buf_get_u32(ARMV4_5_CORE_REG_MODE(arm->core_cache,
            arm->core_mode, reg).value, 0, 32);
}
 
static void armv4_5_set_reg_mode(struct arm_sim_interface *sim, int reg, uint32_t value)
{
    struct arm *arm = (struct arm *)sim->user_data;
 
    buf_set_u32(ARMV4_5_CORE_REG_MODE(arm->core_cache,
        arm->core_mode, reg).value, 0, 32, value);
}
 
static uint32_t armv4_5_get_cpsr(struct arm_sim_interface *sim, int pos, int bits)
{
    struct arm *arm = (struct arm *)sim->user_data;
 
    return buf_get_u32(arm->cpsr->value, pos, bits);
}
 
static enum arm_state armv4_5_get_state(struct arm_sim_interface *sim)
{
    struct arm *arm = (struct arm *)sim->user_data;
 
    return arm->core_state;
}
 
static void armv4_5_set_state(struct arm_sim_interface *sim, enum arm_state mode)
{
    struct arm *arm = (struct arm *)sim->user_data;
 
    arm->core_state = mode;
}
 
static enum arm_mode armv4_5_get_mode(struct arm_sim_interface *sim)
{
    struct arm *arm = (struct arm *)sim->user_data;
 
    return arm->core_mode;
}
 
int arm_simulate_step(struct target *target, uint32_t *dry_run_pc)
{
    struct arm *arm = target_to_arm(target);
    struct arm_sim_interface sim;
 
    sim.user_data = arm;
    sim.get_reg = &armv4_5_get_reg;
    sim.set_reg = &armv4_5_set_reg;
    sim.get_reg_mode = &armv4_5_get_reg_mode;
    sim.set_reg_mode = &armv4_5_set_reg_mode;
    sim.get_cpsr = &armv4_5_get_cpsr;
    sim.get_mode = &armv4_5_get_mode;
    sim.get_state = &armv4_5_get_state;
    sim.set_state = &armv4_5_set_state;
 
    return arm_simulate_step_core(target, dry_run_pc, &sim);
}