244 lines
9.7 KiB
Markdown
244 lines
9.7 KiB
Markdown
# Deshab 兼容层设计文档
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> Linux程序兼容层（双内核park-and-resume）与PE/EXE兼容层（UTSM内置加载器），以及Pacman生态方案。
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---
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## 1. 概述
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Deshab无Linux syscall/动态链接器/Windows API，兼容走两条路线：
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| 兼容层 | 目标 | 路线 | 类比 |
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|--------|------|------|------|
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| Linux兼容层 | Linux x86-64 ELF | UTSM作VMM运行Linux 6.6 guest，Deshab经IPC委托执行取回结果 | WSL |
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| PE/EXE兼容层 | PE32+/PE32 | UTSM内置PE加载器+API shim+x86-32解释器，Ring0直接执行 | 极简Wine |
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核心判断：pacman装的软件是Linux动态链接ELF，不可能在Deshab原生跑。正确模式：Linux guest内Arch+pacman→Deshab通过IPC委托Linux执行→结果显示回Deshab。
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---
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## 2. 双内核架构
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### 2.1 park-and-resume模型
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UTSM作VMM(VMX root)，Linux 6.6 LTS作guest(VMX non-root)常驻内存。
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```text
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UTSM(Ring0) → linux_compat_service.exec() → 写EXEC_REQUEST到utsm_to_linux ring
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→ linux_resume() → vmresume → Linux guest(daemon: RECV_MSG→fork+exec→pipe捕获输出
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→ SEND_MSG STDOUT/STDERR/EXIT → ioctl(PARK)→HLT→VM-Exit)
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← VM-Exit(HLT) → host推进RIP → 从linux_to_utsm ring读输出
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```
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- **park**：guest HLT→VM-Exit→host推进RIP+exit-to-host（`g_guest_parked=1`）
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- **resume**：`linux_resume()`经vmresume唤醒parked guest
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- guest cmdline须含`nohlt idle=poll`：防止内核idle的HLT误触发park
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### 2.2 组件清单
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| 组件 | 文件 |
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|------|------|
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| VMM | `vmm.c/vmx.c/ept.c`, `vmexit.c/vmexit_asm.S` |
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| Linux装载 | `linux_loader.c/linux_boot.c` |
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| 唤醒 | `linux_resume.c` |
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| 兼容服务 | `linux_compat.c`+`linux_compat.h` |
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| IPC | `CODE/utsm-ipc/ipc_proto.h` |
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| virtio后端 | `virtio_mmio.c/virtio_blk.c/virtio_net.c` |
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| Linux侧驱动 | `CODE/linux/patches/utsm_hcall.c` |
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| exec daemon | `CODE/linux/initramfs/bin/utsm_exec_daemon.c` |
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### 2.3 guest构建产物
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| 产物 | 位置 | 说明 |
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|------|------|------|
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| bzImage | `SYSTEM/boot/linux-bzImage` | Limine boot module |
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| initramfs | `SYSTEM/boot/linux-initrd.img` | phase-1最小用户态(init+daemon) |
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| Arch rootfs | `SYSTEM/boot/linux-rootfs.img` | virtio-blk /dev/vdb，含pacman+国内镜像 |
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---
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## 3. Guest GPA内存布局
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定义于`CODE/UTSM/include/utsm/linux_loader.h`：
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| GPA范围 | 用途 |
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|----------|------|
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| 0x00000000–0x003FFFFF | UTSM保留 |
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| 0x00400000 | boot_params(4KB) |
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| 0x00500000 | 内核cmdline(≤4096B) |
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| 0x00600000/0x00700000/0x00800000 | guest GDT/页表/栈 |
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| 0x01000000–0x02FFFFFF | Linux内核镜像(2MB对齐) |
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| 0x03000000–0x03FFFFFF | initrd |
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| **0x04000000–0x040FFFFF** | **IPC共享内存(1MB)** |
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| 0x05000000+ | Linux通用RAM |
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| 0xF4000000/0xF4001000/0xF4002000 | virtio-mmio blk(IRQ5)/net(IRQ6)/rootfs(IRQ7) |
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virtio-mmio设备区EPT故意不映射→EPT violation→vmexit路由到后端模拟。guest经cmdline `virtio_mmio.device=4K@<gpa>:<irq>`发现设备。
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guest cmdline：`console=ttyS0,115200 earlyprintk=serial nokaslr no_timer_check loglevel=7 nohlt idle=poll noapic nolapic nosmp virtio_mmio.device=4K@0xF4000000:5 virtio_mmio.device=4K@0xF4001000:6 virtio_mmio.device=4K@0xF4002000:7`
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---
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## 4. VMCS与VM-Exit处理
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- VMCS不保存guest GPR，`vmexit_asm.S`保存16个GPR到`g_guest_regs`，vmresume前恢复
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- VMCALL约定：a0=rdi, a1=rsi, a2=rdx，返回值写g_guest_regs.rax
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- host恢复点：`g_saved_host_rsp/g_saved_return_rip/g_guest_terminated/g_last_exit_reason`（须非static全局变量）
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已处理退出原因：
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| Exit reason | 处理 |
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|-------------|------|
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| HLT | Linux→park(推进RIP)；自检→terminate |
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| EPT_VIOLATION | GPA在virtio-mmio区→模拟；否则EPT动态映射 |
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| CPUID | 直通+屏蔽VMX/hypervisor位 |
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| IO_INSTRUCTION | 端口I/O模拟 |
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| INTERRUPT_WINDOW | 注入待决虚拟IRQ |
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| VMX_PREEMPTION_TIMER | 周期调virtio_net_poll()填充RX buffer |
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| VMCALL | hypercall分发 |
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---
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## 5. IPC协议
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唯一定义在`CODE/utsm-ipc/ipc_proto.h`（`__UTSM_KERNEL__`/`__KERNEL__`条件包含）。
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### 5.1 共享内存布局(GPA 0x04000000, 1MB, packed)
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```text
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0x04000000 utsm_ipc_shm_header 64B(magic "UTSMHC\0\0"+version+握手位)
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0x04000040 utsm_to_linux ring 16400B(UTSM写，Linux读)
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0x04004050 linux_to_utsm ring 16400B(Linux写，UTSM读)
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0x04008060 payload_pool 1015712B(批量数据缓冲)
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```
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每ring：64槽×256B消息(16B头+240B inline data)。单生产者单消费者，head/tail volatile+内存屏障。
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### 5.2 三条通信通道
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1. 共享内存ring（异步双向）
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2. VMCALL hypercall（同步请求/响应）
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3. IPI通知（UTSM→Linux经guest IRQ注入）
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### 5.3 消息类型
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| 类型 | 值 | 方向/说明 |
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|------|----|-----------|
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| HELLO/HELLO_ACK | 1/2 | 握手 |
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| PING/PONG | 3/4 | 连通性 |
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| EXEC_REQUEST | 16 | UTSM→Linux: ipc_exec_request{argc,flags,path[128],argv_blob[96]} |
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| EXEC_STDOUT/STDERR | 17/18 | Linux→UTSM: 裸字节流分块 |
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| EXEC_EXIT | 19 | Linux→UTSM: exit_code |
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| EXEC_READY | 20 | Linux→UTSM: daemon就绪 |
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| FILE_LIST/READ/WRITE_REQUEST | 24/25/27 | UTSM→Linux: 文件操作 |
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| FILE_RESPONSE | 26 | Linux→UTSM: status+data_len+total_size |
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### 5.4 hypercall操作
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| op | 值 | 说明 |
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|----|----|------|
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| PING/HELLO | 0x0001/0x0002 | 连通性 |
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| SHM_INFO | 0x0010 | 查询共享内存GPA+size |
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| CAP_VALIDATE | 0x0020 | capability校验 |
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| UTRW_READ/WRITE | 0x0030/0x0031 | 封缄内存读写 |
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| DRR_CHECKPOINT | 0x0040 | 触发checkpoint |
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| CONSOLE_WRITE/READ | 0x0050/0x0051 | 串口控制台 |
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| **FILE_READ** | 0x0060 | 读UTSM FAT32文件到payload_pool(a0=文件名GPA,a1=偏移,a2=最大字节;RAX低20位=暂存字节,高位=总大小) |
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| **FILE_WRITE** | 0x0061 | payload_pool写为FAT32文件(整文件替换) |
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单文件≤256KB；payload_pool为单写者通道，禁止并发。
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### 5.5 文件传输协议
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- 读/列目录：UTSM写请求→linux_resume→daemon opendir/readdir或open/pread→数据写进payload_pool→FILE_RESPONSE→HLT park
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- 写：UTSM预摆数据进payload_pool→daemon读出pwrite（offset 0以O_TRUNC打开）
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- payload_pool≈1MB，单次往返最多~1MB，更大文件按递增file_offset循环
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- 状态码：OK=0, NOENT, IO, NOTDIR, ISDIR, PERM, INVAL, NOSPC
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---
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## 6. virtio-mmio设备模拟
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Virtio Spec 1.1 §4.2，32位寄存器。框架`virtio_mmio.c`，后端`virtio_blk.c`/`virtio_net.c`。
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- guest访问设备GPA→EPT violation→handle_virtio_mmio_access→按GPA定位设备+按偏移模拟寄存器
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- 后端注册表`struct virtio_backend{device_id,gpa_base,irq,num_queues,queue_size,device_features,config_len,read_config,queue_notify,reset}`
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- virtqueue split ring(desc 16B/avail/used)
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- `virtio_gpa_to_host()`：EPT翻译GPA→HPA+HHDM offset
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- 中断：置INTERRUPT_STATUS bit0+注入虚拟IRQ(blk→5,net→6,rootfs→7, vector=0x30+irq)
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- net RX异步路径：VMX preemption timer周期调virtio_net_poll()填充guest RX buffer+注入IRQ
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- blk后端已支撑guest挂载Arch rootfs(/dev/vdb)
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---
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## 7. Linux兼容层服务接口
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`linux_compat_service`(magic "LNXCOMP\0")经`dsk_boot_context.reserved[5]`暴露：
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| 接口 | 说明 |
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|------|------|
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| is_available() | guest已park+IPC就绪 |
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| exec(path,argc,argv,stdout_buf,cap,len,exit_code) | 执行Linux程序取回stdout/exit_code |
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| file_list/read/write(path,...) | 列目录/分块读/分块写Linux文件 |
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| file_pull/push(linux_path,fat32_name,...) | Linux文件↔UTSM FAT32根目录(≤256KB) |
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| status(buf,cap) | guest状态字符串 |
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shell命令：`dsl <prog> [args]`(Tab可补全Linux程序名)、`dsl push/pull`、`dsl ls [path]`、`dsl cat <path>`
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---
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## 8. Linux guest侧组件
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**utsm_hcall驱动**：VMCALL发起hypercall；/dev/utsm ioctl: RECV_MSG/SEND_MSG/PARK/GET_READY/WRITE_POOL/READ_POOL
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**exec daemon**(PID 2)：启动→发EXEC_READY→ioctl(PARK)→HLT；循环：vmresume唤醒→RECV_MSG→处理(EXEC_REQUEST:fork+exec+pipe; FILE_*:opendir/open/pread/pwrite)→ioctl(PARK)
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---
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## 9. PE/EXE兼容层
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四组件经`dsk_boot_context.reserved[4]`暴露`pe_service`(magic "PESVC\0\0"，接口load/run/unload)：
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| 组件 | 职责 |
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|------|------|
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| pe_loader.c | DOS/NT头校验+节区映射+重定位+import表解析 |
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| pe_shim.c | Windows API shim(ms_abi包装)+IAT填充 |
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| x86emu32.c | x86-32解释器(PE32执行引擎) |
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| pe_service.c | 服务装配+执行策略 |
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执行策略：
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- **PE32+**：重定位加载→IAT填ms_abi shim→Ring0原生执行；ExitProcess经__builtin_longjmp跳回
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- **PE32**：preferred_base直接加载(64KB栈+256KB堆)+IAT填合成地址(0x00010000|shim_idx)→x86emu32解释执行。约束：镜像≤64MB, preferred_base≤0x10000000, IAT≤256项
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安全方向：PE shim白名单+IAT拦截审计。
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---
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## 10. Pacman五阶段方案
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| 阶段 | 内容 | 状态 |
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|------|------|------|
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| 1. Linux guest跑起来 | virtio-blk/net+initramfs/rootfs+EPT动态映射 | ✅ |
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| 2. guest内Arch+pacman | Arch bootstrap rootfs+国内mirrorlist | ✅(网络下载待联网验证) |
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| 3. UTSM↔Linux文件传输IPC | FILE_READ/WRITE hypercall+ring分块+shell接入 | ✅(代码全链路就绪) |
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| 4. shell命令委托执行 | IPC exec(16–20)+daemon fork/exec | ✅(全链路已验证) |
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| 5. desktop集成 | app_descriptor.linux_cmd+LINUXAPP.CNF | ✅ |
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**最大遗留项：VMX实机验证**（需嵌套虚拟化环境）。WHPX不支持嵌套VMX，已通过vmx_truly_available()检测+QEMU -cpu qemu64,-vmx规避，无VMX时linux命令优雅降级。
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---
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## 11. 实现状态总览
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| 能力 | 状态 |
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|------|------|
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| VMM(VMX/EPT/VMCS/VM-Exit) | ✅ |
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| Linux guest装载与启动 | ✅ |
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| park-and-resume | ✅ |
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| IPC(ring+hypercall+payload_pool) | ✅ |
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| virtio-mmio blk/rootfs | ✅ |
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| virtio-mmio net | 🔶(后端框架+RX poll) |
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| linux_compat_service | ✅ |
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| PE32+/PE32执行 | ✅ |
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| VMX实机验证 | ❌ |
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