semihost.cpp

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#include <cstdio>
#include "etiss/ETISS.h"
 
#include "SemihostingCalls.h"
 
extern "C"
{
#include "libsemihost.h"
}
 
// constant for SYS_ELAPSED and SYS_TICKFREQ
#define TICKER_FREQ 1000 // Hz
 
// constants for SYS_OPEN
const char *SYS_OPEN_MODES_STRS[] = { "r", "rb", "r+", "r+b", "w", "wb", "w+", "w+b", "a", "ab", "a+", "a+b" };
#define SYS_OPEN_MODES_TOTAL 12 // total number of modes
#define SYS_OPEN_MODES_IN_LIMIT 4
#define SYS_OPEN_MODES_OUT_LIMIT 8
 
#define PS_PER_CS 10000000000 // 10 * 10^9
 
// if var is negative set semihosting errno and return -1
#define CHECK_NEGATIVE_RETURN(var) \
    if ((var) < 0)                 \
    {                              \
        semihostingErrno = errno;  \
        return -1;                 \
    }
 
// For many semihosting calls parameter points to a data block, so this type of call is very common
#define FIELD(fieldNo) semihostReadStructField(etissSystem, XLEN / 8, parameter, fieldNo);
 
// forward declaration for use in extern block:
 
etiss_int64 semihostingCall(ETISS_CPU *const cpu, ETISS_System *const etissSystem, etiss_uint32 XLEN,
                            etiss_uint64 operationNumber, etiss_uint64 parameter);
 
extern "C"
{
    uint8_t etiss_semihost_enabled()
    {
        return etiss::cfg().get<bool>("arch.enable_semihosting", false);
    }
 
    int64_t etiss_semihost(ETISS_CPU *const cpu, ETISS_System *const etissSystem, void *const *const _, uint32_t XLEN,
                           uint64_t operation, uint64_t parameter)
    {
        return semihostingCall(cpu, etissSystem, XLEN, operation, parameter);
    }
}
 
etiss_uint64 semihostReadStructField(ETISS_System *etissSystem, etiss_uint32 numBytes, etiss_uint64 address,
                                     int fieldNo)
{
    if (numBytes == 8)
    {
        etiss_uint64 field = 0;
        etissSystem->dbg_read(etissSystem->handle, address + 8 * fieldNo, (etiss_uint8 *)&field, 8);
        return field;
    }
    else if (numBytes == 4)
    {
        etiss_uint32 field = 0;
        etissSystem->dbg_read(etissSystem->handle, address + 4 * fieldNo, (etiss_uint8 *)&field, 4);
        return field;
    }
    else if (numBytes == 2)
    {
        etiss_uint16 field = 0;
        etissSystem->dbg_read(etissSystem->handle, address + 2 * fieldNo, (etiss_uint8 *)&field, 2);
        return field;
    }
    else if (numBytes == 1)
    {
        etiss_uint8 field = 0;
        etissSystem->dbg_read(etissSystem->handle, address + 1 * fieldNo, &field, 1);
        return field;
    }
 
    etiss::log(etiss::ERROR, "semihostReadStructField called with numBytes != 1, 2, 4 or 8");
    return 0;
}
 
std::vector<etiss_uint8> semihostReadSystemMemory(ETISS_System *etissSystem, etiss_uint64 address, etiss_uint64 length)
{
    std::vector<etiss_uint8> buffer;
    buffer.resize(length);
    etissSystem->dbg_read(etissSystem->handle, address, buffer.data(), length);
    return buffer;
}
 
void semihostWriteSystemMemory(ETISS_System *etissSystem, etiss_uint64 address, std::vector<etiss_uint8> data)
{
    etissSystem->dbg_write(etissSystem->handle, address, data.data(), data.size());
}
 
std::string semihostReadString(ETISS_System *etissSystem, etiss_uint64 address, etiss_uint64 length)
{
    std::vector<etiss_uint8> buffer = semihostReadSystemMemory(etissSystem, address, length);
    std::string str(buffer.begin(), buffer.end());
    return str;
}
 
void semihostWriteString(ETISS_System *etissSystem, etiss_uint64 address, std::string str)
{
    etissSystem->dbg_write(etissSystem->handle, address, (etiss_uint8 *)str.c_str(), str.length() + 1);
}
 
bool is_std_in_out_err(FILE *file)
{
    return file == stdin || file == stdout || file == stderr;
}
 
etiss_int64 semihostingCall(ETISS_CPU *const cpu, ETISS_System *const etissSystem, etiss_uint32 XLEN,
                            etiss_uint64 operationNumber, etiss_uint64 parameter)
{
    // static variables to keep track of semihosting state
 
    static std::map<etiss_uint64, FILE *> openFiles;
    static etiss_uint64 nextFd = 0;
    static etiss_int64 semihostingErrno;
 
    switch (operationNumber)
    {
    // share code between all operations that have the
    // file descriptor as their first argument
    case SYS_CLOSE:
    case SYS_WRITE:
    case SYS_READ:
    case SYS_ISTTY:
    case SYS_SEEK:
    case SYS_FLEN:
    {
        etiss_uint64 fd = FIELD(0);
        if (openFiles.count(fd) == 0)
        {
            std::stringstream ss;
            ss << "Semihosting: invalid file descriptor " << fd << " for semihosting call 0x" << std::hex
               << std::setfill('0') << std::setw(2) << operationNumber;
            etiss::log(etiss::INFO, ss.str());
            semihostingErrno = EBADF;
            return -1;
        }
        auto file = openFiles[fd];
 
        switch (operationNumber)
        {
        case SYS_CLOSE:
        {
            std::stringstream ss;
            ss << "Semihosting: SYS_CLOSE fd " << fd;
            etiss::log(etiss::VERBOSE, ss.str());
 
            openFiles.erase(fd);
            // do not close stdin, stdout, stderr of host process
            if (!is_std_in_out_err(file))
                fclose(file);
            return 0;
        }
        case SYS_WRITE:
        {
            etiss_uint64 address = FIELD(1);
            etiss_uint64 count = FIELD(2);
 
            std::stringstream ss;
            ss << "Semihosting: SYS_WRITE fd " << fd;
            etiss::log(etiss::VERBOSE, ss.str());
 
            std::vector<etiss_uint8> buffer = semihostReadSystemMemory(etissSystem, address, count);
 
            size_t num_written = fwrite(buffer.data(), 1, count, file);
            return count - num_written;
        }
        case SYS_READ:
        {
            etiss_uint64 address = FIELD(1);
            etiss_uint64 count = FIELD(2);
 
            std::stringstream ss;
            ss << "Semihosting: SYS_READ fd " << fd << " count " << count;
            etiss::log(etiss::VERBOSE, ss.str());
 
            std::vector<etiss_uint8> buffer;
            buffer.resize(count);
 
            size_t num_read = 0;
            if (file == stdin)
            {
                // when reading from stdin: mimic behaviour from read syscall
                // and return on newline.
                while (num_read < count)
                {
                    char c = fgetc(file);
                    buffer[num_read] = c;
                    num_read++;
                    if (c == '\n')
                        break;
                }
            }
            else
            {
                num_read = fread(buffer.data(), 1, count, file);
            }
 
            buffer.resize(num_read);
            semihostWriteSystemMemory(etissSystem, address, buffer);
 
            return (etiss_int64)count - num_read;
        }
        case SYS_ISTTY:
        {
            std::stringstream ss;
            ss << "Semihosting: SYS_ISTTY fd " << fd;
            etiss::log(etiss::VERBOSE, ss.str());
 
            return is_std_in_out_err(file);
        }
        case SYS_SEEK:
        {
            etiss_uint64 position = FIELD(1);
 
            std::stringstream ss;
            ss << "Semihosting: SYS_SEEK fd " << fd << ": " << position;
            etiss::log(etiss::VERBOSE, ss.str());
 
            int retval = fseek(file, position, SEEK_SET);
            CHECK_NEGATIVE_RETURN(retval);
            return 0;
        }
        case SYS_FLEN:
        {
            std::stringstream ss;
            ss << "Semihosting: SYS_FLEN fd " << fd;
            etiss::log(etiss::VERBOSE, ss.str());
 
            size_t currentPos = ftell(file);
            CHECK_NEGATIVE_RETURN(currentPos);
            fseek(file, 0, SEEK_END);
            size_t length = ftell(file);
            fseek(file, currentPos, SEEK_SET);
            return (etiss_int64)length;
        }
        }
    }
    case SYS_OPEN:
    {
        etiss_uint64 path_str_addr = FIELD(0);
        etiss_uint64 mode = FIELD(1);
        etiss_uint64 path_str_len = FIELD(2);
 
        std::string path_str = semihostReadString(etissSystem, path_str_addr, path_str_len);
 
        std::stringstream ss;
        ss << "Semihosting: SYS_OPEN \"" << path_str << "\"";
        etiss::log(etiss::VERBOSE, ss.str());
 
        if (mode >= SYS_OPEN_MODES_TOTAL)
        {
            // invalid mode
            semihostingErrno = EINVAL;
            return -1;
        }
 
        FILE *file = nullptr;
        if (path_str == ":tt")
        {
            // special file path for opening stdin, stdout and stderr
            // open stdin, stdout or stderr depending on mode argument
            if (mode < SYS_OPEN_MODES_IN_LIMIT) // 0 <= mode <= 3
                file = stdin;
            else if (mode < SYS_OPEN_MODES_OUT_LIMIT) // 4 <= mode <= 7
                file = stdout;
            else // 8 <= mode <= 11
                file = stderr;
        }
        else
        {
            file = fopen(path_str.c_str(), SYS_OPEN_MODES_STRS[mode]);
            if (file == nullptr)
            {
                semihostingErrno = errno;
                return -1;
            }
        }
        etiss_uint64 fd = nextFd++;
        openFiles[fd] = file;
 
        return (etiss_int64)fd;
    }
    case SYS_WRITEC:
    {
        etiss_uint64 character = semihostReadStructField(etissSystem, 1, parameter, 0);
        putchar(character);
        return 0;
    }
    case SYS_WRITE0:
    {
        etiss_uint64 address = parameter;
        while (1)
        {
            etiss_uint64 character = semihostReadStructField(etissSystem, 1, address, 0);
            if (character == 0)
                break;
            putchar(character);
            address++;
        }
        return 0;
    }
    case SYS_READC:
    {
        return getchar();
    }
    case SYS_ISERROR:
    {
        etiss_uint64 value = FIELD(0);
        return value != 0;
    }
    case SYS_TMPNAM:
    {
        etiss_uint64 buffer_address = FIELD(0);
        etiss_uint64 identifier = FIELD(1);
        etiss_uint64 buffer_len = FIELD(2);
 
        if (identifier > 255)
            return -1;
 
        std::stringstream ss;
        ss << "etiss-tmp/file-" << std::setfill('0') << std::setw(3) << identifier;
        std::string filename = ss.str();
 
        if (buffer_len <= filename.length() + 1)
            return -1;
 
        semihostWriteString(etissSystem, buffer_address, filename);
        return 0;
    }
    case SYS_REMOVE:
    {
        etiss_uint64 path_str_addr = FIELD(0);
        etiss_uint64 path_str_len = FIELD(1);
 
        std::string path_str = semihostReadString(etissSystem, path_str_addr, path_str_len);
 
        std::stringstream ss;
        ss << "Semihosting: SYS_REMOVE \"" << path_str << "\"";
        etiss::log(etiss::VERBOSE, ss.str());
 
        if (remove(path_str.c_str()) < 0)
        {
            semihostingErrno = errno;
            return -1;
        }
        return 0;
    }
    case SYS_RENAME:
    {
        etiss_uint64 old_str_addr = FIELD(0);
        etiss_uint64 old_str_len = FIELD(1);
        etiss_uint64 new_str_addr = FIELD(2);
        etiss_uint64 new_str_len = FIELD(3);
 
        std::string old_str = semihostReadString(etissSystem, old_str_addr, old_str_len);
        std::string new_str = semihostReadString(etissSystem, new_str_addr, new_str_len);
 
        std::stringstream ss;
        ss << "Semihosting: SYS_RENAME \"" << old_str << "\" to \"" << new_str << "\"";
        etiss::log(etiss::VERBOSE, ss.str());
 
        return rename(old_str.c_str(), new_str.c_str());
    }
    case SYS_CLOCK:
    {
        // return centiseconds since some arbitrary start point
        return cpu->cpuTime_ps / PS_PER_CS;
    }
    case SYS_TIME:
    {
        etiss::log(etiss::VERBOSE, "Semihosting: SYS_TIME");
        etiss_int64 seconds_since_epoch = (etiss_int64)std::time(0);
        return seconds_since_epoch;
    }
    case SYS_ERRNO:
    {
        std::stringstream ss;
        ss << "Semihosting: SYS_ERRNO (" << semihostingErrno << ")";
        etiss::log(etiss::VERBOSE, ss.str());
        return semihostingErrno;
    }
    case SYS_EXIT:
    {
        etiss::log(etiss::VERBOSE, "Semihosting: SYS_EXIT -> exit simulator");
 
        cpu->exception = ETISS_RETURNCODE_CPUFINISHED;
        cpu->return_pending = 1;
        return 0;
    }
    case SYS_ELAPSED:
    {
        return cpu->cpuTime_ps / TICKER_FREQ;
    }
    case SYS_TICKFREQ:
    {
        return TICKER_FREQ;
    }
    case SYS_SYSTEM:
    case SYS_GET_CMDLINE:
    case SYS_HEAPINFO:
    case SYS_EXIT_EXTENDED:
    {
        std::stringstream ss;
        ss << "Semihosting: operation not implemented: " << operationNumber;
        etiss::log(etiss::WARNING, ss.str());
        return 0;
    }
    default:
    {
        std::stringstream ss;
        ss << "Semihosting: unknown operation number: " << operationNumber;
        etiss::log(etiss::WARNING, ss.str());
        return 0;
    }
    }
}