linux-user/semihost.c

/*
 * ARM Compatible Semihosting Console Support.
 *
 * Copyright (c) 2019 Linaro Ltd
 *
 * Currently ARM and RISC-V are unique in having support for
 * semihosting support in linux-user. So for now we implement the
 * common console API but just for arm and risc-v linux-user.
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "qemu/osdep.h"
#include "cpu.h"
#include "hw/semihosting/console.h"
#include "qemu.h"
#include <termios.h>

int qemu_semihosting_console_outs(CPUArchState *env, target_ulong addr)
{
    int len = target_strlen(addr);
    void *s;
    if (len < 0){
       qemu_log_mask(LOG_GUEST_ERROR,
                     "%s: passed inaccessible address " TARGET_FMT_lx,
                     __func__, addr);
       return 0;
    }
    s = lock_user(VERIFY_READ, addr, (long)(len + 1), 1);
    g_assert(s);  /* target_strlen has already verified this will work */
    len = write(STDERR_FILENO, s, len);
    unlock_user(s, addr, 0);
    return len;
}

void qemu_semihosting_console_outc(CPUArchState *env, target_ulong addr)
{
    char c;

    if (get_user_u8(c, addr)) {
        qemu_log_mask(LOG_GUEST_ERROR,
                      "%s: passed inaccessible address " TARGET_FMT_lx,
                      __func__, addr);
    } else {
        if (write(STDERR_FILENO, &c, 1) != 1) {
            qemu_log_mask(LOG_UNIMP, "%s: unexpected write to stdout failure",
                          __func__);
        }
    }
}

/*
 * For linux-user we can safely block. However as we want to return as
 * soon as a character is read we need to tweak the termio to disable
 * line buffering. We restore the old mode afterwards in case the
 * program is expecting more normal behaviour. This is slow but
 * nothing using semihosting console reading is expecting to be fast.
 */
target_ulong qemu_semihosting_console_inc(CPUArchState *env)
{
    uint8_t c;
    struct termios old_tio, new_tio;

    /* Disable line-buffering and echo */
    tcgetattr(STDIN_FILENO, &old_tio);
    new_tio = old_tio;
    new_tio.c_lflag &= (~ICANON & ~ECHO);
    tcsetattr(STDIN_FILENO, TCSANOW, &new_tio);

    c = getchar();

    /* restore config */
    tcsetattr(STDIN_FILENO, TCSANOW, &old_tio);

    return (target_ulong) c;
}