加多一個debug protocol去qemu是可能的

加多一個debug protocol去qemu是可能的, 只要重寫gdbstub.c裏的gdb_handle_packet(), socket方面很容易搞, 照抄gdbserver就行


static int gdb_handle_packet(GDBState *s, const char *line_buf)
{
	printf("gdb_handle_packet=%s\n", line_buf);
    CPUArchState *env;
    const char *p;
    uint32_t thread;
    int ch, reg_size, type, res;
    char buf[MAX_PACKET_LENGTH];
    uint8_t mem_buf[MAX_PACKET_LENGTH];
    uint8_t *registers;
    target_ulong addr, len;

#ifdef DEBUG_GDB
    printf("command='%s'\n", line_buf);
#endif
    p = line_buf;
    ch = *p++;
    switch(ch) {
    case '?':
        /* TODO: Make this return the correct value for user-mode.  */
        snprintf(buf, sizeof(buf), "T%02xthread:%02x;", GDB_SIGNAL_TRAP,
                 cpu_index(s->c_cpu));
        put_packet(s, buf);
        /* Remove all the breakpoints when this query is issued,
         * because gdb is doing and initial connect and the state
         * should be cleaned up.
         */
        gdb_breakpoint_remove_all();
        break;
    case 'c':
        if (*p != '\0') {
            addr = strtoull(p, (char **)&p, 16);
            gdb_set_cpu_pc(s, addr);
        }
        s->signal = 0;
        gdb_continue(s);
	return RS_IDLE;
    case 'C':
        s->signal = gdb_signal_to_target (strtoul(p, (char **)&p, 16));
        if (s->signal == -1)
            s->signal = 0;
        gdb_continue(s);
        return RS_IDLE;
    case 'v':
        if (strncmp(p, "Cont", 4) == 0) {
            int res_signal, res_thread;

            p += 4;
            if (*p == '?') {
                put_packet(s, "vCont;c;C;s;S");
                break;
            }
            res = 0;
            res_signal = 0;
            res_thread = 0;
            while (*p) {
                int action, signal;

                if (*p++ != ';') {
                    res = 0;
                    break;
                }
                action = *p++;
                signal = 0;
                if (action == 'C' || action == 'S') {
                    signal = strtoul(p, (char **)&p, 16);
                } else if (action != 'c' && action != 's') {
                    res = 0;
                    break;
                }
                thread = 0;
                if (*p == ':') {
                    thread = strtoull(p+1, (char **)&p, 16);
                }
                action = tolower(action);
                if (res == 0 || (res == 'c' && action == 's')) {
                    res = action;
                    res_signal = signal;
                    res_thread = thread;
                }
            }
            if (res) {
                if (res_thread != -1 && res_thread != 0) {
                    env = find_cpu(res_thread);
                    if (env == NULL) {
                        put_packet(s, "E22");
                        break;
                    }
                    s->c_cpu = env;
                }
                if (res == 's') {
                    cpu_single_step(s->c_cpu, sstep_flags);
                }
                s->signal = res_signal;
                gdb_continue(s);
                return RS_IDLE;
            }
            break;
        } else {
            goto unknown_command;
        }
    case 'k':
#ifdef CONFIG_USER_ONLY
        /* Kill the target */
        fprintf(stderr, "\nQEMU: Terminated via GDBstub\n");
        exit(0);
#endif
    case 'D':
        /* Detach packet */
        gdb_breakpoint_remove_all();
        gdb_syscall_mode = GDB_SYS_DISABLED;
        gdb_continue(s);
        put_packet(s, "OK");
        break;
    case 's':
        if (*p != '\0') {
            addr = strtoull(p, (char **)&p, 16);
            gdb_set_cpu_pc(s, addr);
        }
        cpu_single_step(s->c_cpu, sstep_flags);
        gdb_continue(s);
	return RS_IDLE;
    case 'F':
        {
            target_ulong ret;
            target_ulong err;

            ret = strtoull(p, (char **)&p, 16);
            if (*p == ',') {
                p++;
                err = strtoull(p, (char **)&p, 16);
            } else {
                err = 0;
            }
            if (*p == ',')
                p++;
            type = *p;
            if (s->current_syscall_cb) {
                s->current_syscall_cb(s->c_cpu, ret, err);
                s->current_syscall_cb = NULL;
            }
            if (type == 'C') {
                put_packet(s, "T02");
            } else {
                gdb_continue(s);
            }
        }
        break;
    case 'g':
        cpu_synchronize_state(s->g_cpu);
        env = s->g_cpu;
        len = 0;
        for (addr = 0; addr < num_g_regs; addr++) {
            reg_size = gdb_read_register(s->g_cpu, mem_buf + len, addr);
            len += reg_size;
        }
        memtohex(buf, mem_buf, len);
        put_packet(s, buf);
        break;
    case 'G':
        cpu_synchronize_state(s->g_cpu);
        env = s->g_cpu;
        registers = mem_buf;
        len = strlen(p) / 2;
        hextomem((uint8_t *)registers, p, len);
        for (addr = 0; addr < num_g_regs && len > 0; addr++) {
            reg_size = gdb_write_register(s->g_cpu, registers, addr);
            len -= reg_size;
            registers += reg_size;
        }
        put_packet(s, "OK");
        break;
    case 'm':
        addr = strtoull(p, (char **)&p, 16);
        if (*p == ',')
            p++;
        len = strtoull(p, NULL, 16);
        if (target_memory_rw_debug(s->g_cpu, addr, mem_buf, len, 0) != 0) {
            put_packet (s, "E14");
        } else {
            memtohex(buf, mem_buf, len);
            put_packet(s, buf);
        }
        break;
    case 'M':
        addr = strtoull(p, (char **)&p, 16);
        if (*p == ',')
            p++;
        len = strtoull(p, (char **)&p, 16);
        if (*p == ':')
            p++;
        hextomem(mem_buf, p, len);
        if (target_memory_rw_debug(s->g_cpu, addr, mem_buf, len, 1) != 0) {
            put_packet(s, "E14");
        } else {
            put_packet(s, "OK");
        }
        break;
    case 'p':
        /* Older gdb are really dumb, and don't use 'g' if 'p' is avaialable.
           This works, but can be very slow.  Anything new enough to
           understand XML also knows how to use this properly.  */
        if (!gdb_has_xml)
            goto unknown_command;
        addr = strtoull(p, (char **)&p, 16);
        reg_size = gdb_read_register(s->g_cpu, mem_buf, addr);
        if (reg_size) {
            memtohex(buf, mem_buf, reg_size);
            put_packet(s, buf);
        } else {
            put_packet(s, "E14");
        }
        break;
    case 'P':
        if (!gdb_has_xml)
            goto unknown_command;
        addr = strtoull(p, (char **)&p, 16);
        if (*p == '=')
            p++;
        reg_size = strlen(p) / 2;
        hextomem(mem_buf, p, reg_size);
        gdb_write_register(s->g_cpu, mem_buf, addr);
        put_packet(s, "OK");
        break;
    case 'Z':
    case 'z':
        type = strtoul(p, (char **)&p, 16);
        if (*p == ',')
            p++;
        addr = strtoull(p, (char **)&p, 16);
        if (*p == ',')
            p++;
        len = strtoull(p, (char **)&p, 16);
        if (ch == 'Z')
            res = gdb_breakpoint_insert(addr, len, type);
        else
            res = gdb_breakpoint_remove(addr, len, type);
        if (res >= 0)
             put_packet(s, "OK");
        else if (res == -ENOSYS)
            put_packet(s, "");
        else
            put_packet(s, "E22");
        break;
    case 'H':
        type = *p++;
        thread = strtoull(p, (char **)&p, 16);
        if (thread == -1 || thread == 0) {
            put_packet(s, "OK");
            break;
        }
        env = find_cpu(thread);
        if (env == NULL) {
            put_packet(s, "E22");
            break;
        }
        switch (type) {
        case 'c':
            s->c_cpu = env;
            put_packet(s, "OK");
            break;
        case 'g':
            s->g_cpu = env;
            put_packet(s, "OK");
            break;
        default:
             put_packet(s, "E22");
             break;
        }
        break;
    case 'T':
        thread = strtoull(p, (char **)&p, 16);
        env = find_cpu(thread);

        if (env != NULL) {
            put_packet(s, "OK");
        } else {
            put_packet(s, "E22");
        }
        break;
    case 'q':
    case 'Q':
        /* parse any 'q' packets here */
        if (!strcmp(p,"qemu.sstepbits")) {
            /* Query Breakpoint bit definitions */
            snprintf(buf, sizeof(buf), "ENABLE=%x,NOIRQ=%x,NOTIMER=%x",
                     SSTEP_ENABLE,
                     SSTEP_NOIRQ,
                     SSTEP_NOTIMER);
            put_packet(s, buf);
            break;
        } else if (strncmp(p,"qemu.sstep",10) == 0) {
            /* Display or change the sstep_flags */
            p += 10;
            if (*p != '=') {
                /* Display current setting */
                snprintf(buf, sizeof(buf), "0x%x", sstep_flags);
                put_packet(s, buf);
                break;
            }
            p++;
            type = strtoul(p, (char **)&p, 16);
            sstep_flags = type;
            put_packet(s, "OK");
            break;
        } else if (strcmp(p,"C") == 0) {
            /* "Current thread" remains vague in the spec, so always return
             *  the first CPU (gdb returns the first thread). */
            put_packet(s, "QC1");
            break;
        } else if (strcmp(p,"fThreadInfo") == 0) {
            s->query_cpu = first_cpu;
            goto report_cpuinfo;
        } else if (strcmp(p,"sThreadInfo") == 0) {
        report_cpuinfo:
            if (s->query_cpu) {
                snprintf(buf, sizeof(buf), "m%x", cpu_index(s->query_cpu));
                put_packet(s, buf);
                s->query_cpu = s->query_cpu->next_cpu;
            } else
                put_packet(s, "l");
            break;
        } else if (strncmp(p,"ThreadExtraInfo,", 16) == 0) {
            thread = strtoull(p+16, (char **)&p, 16);
            env = find_cpu(thread);
            if (env != NULL) {
                cpu_synchronize_state(env);
                len = snprintf((char *)mem_buf, sizeof(mem_buf),
                               "CPU#%d [%s]", env->cpu_index,
                               env->halted ? "halted " : "running");
                memtohex(buf, mem_buf, len);
                put_packet(s, buf);
            }
            break;
        }
#ifdef CONFIG_USER_ONLY
        else if (strncmp(p, "Offsets", 7) == 0) {
            TaskState *ts = s->c_cpu->opaque;

            snprintf(buf, sizeof(buf),
                     "Text=" TARGET_ABI_FMT_lx ";Data=" TARGET_ABI_FMT_lx
                     ";Bss=" TARGET_ABI_FMT_lx,
                     ts->info->code_offset,
                     ts->info->data_offset,
                     ts->info->data_offset);
            put_packet(s, buf);
            break;
        }
#else /* !CONFIG_USER_ONLY */
        else if (strncmp(p, "Rcmd,", 5) == 0) {
            int len = strlen(p + 5);

            if ((len % 2) != 0) {
                put_packet(s, "E01");
                break;
            }
            hextomem(mem_buf, p + 5, len);
            len = len / 2;
            mem_buf[len++] = 0;
            qemu_chr_be_write(s->mon_chr, mem_buf, len);
            put_packet(s, "OK");
            break;
        }
#endif /* !CONFIG_USER_ONLY */
        if (strncmp(p, "Supported", 9) == 0) {
            snprintf(buf, sizeof(buf), "PacketSize=%x", MAX_PACKET_LENGTH);
#ifdef GDB_CORE_XML
            pstrcat(buf, sizeof(buf), ";qXfer:features:read+");
#endif
            put_packet(s, buf);
            break;
        }
#ifdef GDB_CORE_XML
        if (strncmp(p, "Xfer:features:read:", 19) == 0) {
            const char *xml;
            target_ulong total_len;

            gdb_has_xml = 1;
            p += 19;
            xml = get_feature_xml(p, &p);
            if (!xml) {
                snprintf(buf, sizeof(buf), "E00");
                put_packet(s, buf);
                break;
            }

            if (*p == ':')
                p++;
            addr = strtoul(p, (char **)&p, 16);
            if (*p == ',')
                p++;
            len = strtoul(p, (char **)&p, 16);

            total_len = strlen(xml);
            if (addr > total_len) {
                snprintf(buf, sizeof(buf), "E00");
                put_packet(s, buf);
                break;
            }
            if (len > (MAX_PACKET_LENGTH - 5) / 2)
                len = (MAX_PACKET_LENGTH - 5) / 2;
            if (len < total_len - addr) {
                buf[0] = 'm';
                len = memtox(buf + 1, xml + addr, len);
            } else {
                buf[0] = 'l';
                len = memtox(buf + 1, xml + addr, total_len - addr);
            }
            put_packet_binary(s, buf, len + 1);
            break;
        }
#endif
        /* Unrecognised 'q' command.  */
        goto unknown_command;

    default:
    unknown_command:
        /* put empty packet */
        buf[0] = '\0';
        put_packet(s, buf);
        break;
    }
    return RS_IDLE;
}

void gdb_set_stop_cpu(CPUArchState *env)
{
    gdbserver_state->c_cpu = env;
    gdbserver_state->g_cpu = env;
}

#ifndef CONFIG_USER_ONLY
static void gdb_vm_state_change(void *opaque, int running, RunState state)
{
    GDBState *s = gdbserver_state;
    CPUArchState *env = s->c_cpu;
    char buf[256];
    const char *type;
    int ret;

    if (running || s->state == RS_INACTIVE) {
        return;
    }
    /* Is there a GDB syscall waiting to be sent?  */
    if (s->current_syscall_cb) {
        put_packet(s, s->syscall_buf);
        return;
    }
    switch (state) {
    case RUN_STATE_DEBUG:
        if (env->watchpoint_hit) {
            switch (env->watchpoint_hit->flags & BP_MEM_ACCESS) {
            case BP_MEM_READ:
                type = "r";
                break;
            case BP_MEM_ACCESS:
                type = "a";
                break;
            default:
                type = "";
                break;
            }
            snprintf(buf, sizeof(buf),
                     "T%02xthread:%02x;%swatch:" TARGET_FMT_lx ";",
                     GDB_SIGNAL_TRAP, cpu_index(env), type,
                     env->watchpoint_hit->vaddr);
            env->watchpoint_hit = NULL;
            goto send_packet;
        }
        tb_flush(env);
        ret = GDB_SIGNAL_TRAP;
        break;
    case RUN_STATE_PAUSED:
        ret = GDB_SIGNAL_INT;
        break;
    case RUN_STATE_SHUTDOWN:
        ret = GDB_SIGNAL_QUIT;
        break;
    case RUN_STATE_IO_ERROR:
        ret = GDB_SIGNAL_IO;
        break;
    case RUN_STATE_WATCHDOG:
        ret = GDB_SIGNAL_ALRM;
        break;
    case RUN_STATE_INTERNAL_ERROR:
        ret = GDB_SIGNAL_ABRT;
        break;
    case RUN_STATE_SAVE_VM:
    case RUN_STATE_RESTORE_VM:
        return;
    case RUN_STATE_FINISH_MIGRATE:
        ret = GDB_SIGNAL_XCPU;
        break;
    default:
        ret = GDB_SIGNAL_UNKNOWN;
        break;
    }
    snprintf(buf, sizeof(buf), "T%02xthread:%02x;", ret, cpu_index(env));

send_packet:
    put_packet(s, buf);

    /* disable single step if it was enabled */
    cpu_single_step(env, 0);
}


### QEMU 虚拟机搭建与配置 #### 安装依赖包 为了安装并运行 QEMU,需先确保操作系统已更新至最新状态,并安装必要的软件包。对于基于 Debian 的系统而言: ```bash sudo apt-get update && sudo apt-get upgrade -y sudo apt-get install qemu-kvm libvirt-daemon-system libvirt-clients bridge-utils virtinst cpu-checker -y ``` 以上命令不仅会下载所需的工具集还会设置好基础环境[^1]。 #### 创建桥接网络适配器 创建名为 `virbr0` 或其他名称的桥接设备用于连接物理网卡和虚拟机内部网卡。编辑 `/etc/network/interfaces.d/bridge-br0.cfg` 文件加入如下内容: ```plaintext auto br0 iface br0 inet dhcp bridge_ports eth0 bridge_stp off bridge_fd 0 bridge_maxwait 0 ``` 此操作使得宿主机上的特定网口能够共享给 VM 使用从而达到内外联通的效果[^2]。 #### 启动服务并验证功能正常 完成上述更改之后重启计算机或者手动激活新建立起来的服务单元文件: ```bash sudo systemctl restart networking.service sudo service libvirtd start ``` 此时应该可以查看到新的桥梁接口已经处于工作当中了。 #### 下载镜像准备启动实例 前往官方站点或者其他可信资源处选取适合版本的操作系统 ISO 映像作为初始加载项;接着利用图形界面管理程序如 Virt-manager 来简化整个过程或是编写 XML 描述文档定义硬件参数进而调用命令行实用程序来进行部署活动。 ```xml <domain type='kvm'> <name>TestVM</name> ... <!-- 更多配置 --> ... </domain> ``` 最后一步就是执行实际开机指令让新建好的 Guest OS 开始运作啦! ```bash virt-install --import \ --name test-vm \ --ram=2048 \ --disk path=/var/lib/libvirt/images/test.img,size=10 \ --vcpus=2 \ --os-type linux \ --network bridge=virbr0,model=virtio \ --graphics none \ --console pty,target_type=serial \ --location 'http://archive.ubuntu.com/ubuntu/dists/focal/main/installer-amd64/' \ --extra-args 'console=ttyS0,115200n8 serial' ``` 该段脚本指定了内存大小、磁盘容量以及 CPU 数量等重要属性的同时还特别强调采用 virto 方式的 NIC 绑定方式以便获得更好的性能表现。 #### 自动化网络配置保存 为了避免每次重新引导时都要重复相同的设定动作可以在目标系统的 rc.local 中追加对应条目实现自动生效的目的。例如针对 CentOS/RHEL 类型发行版来说就是在 /etc/rc.d/rc.local 加入下面这几句语句即可达成目的: ```bash echo "ifconfig eth0 up" >> /etc/rc.d/rc.local chmod +x /etc/rc.d/rc.local ``` 而对于 Ubuntu 用户则建议修改 netplan 配置文件来持久化 IP 地址分配策略。
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