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| title: 2024秋冬季开源操作系统训练营第四阶段总结-hbuxiaofei | ||
| date: 2024-12-21 22:00:35 | ||
| tags: | ||
| --- | ||
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| ## x86 架构 hypervisor SeaBIOS 引导与 Linux 启动实现 | ||
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| ### 1. seabios 工作流程 | ||
| ``` | ||
| (1) POST( Power On Self Test)：上电自检，BIOS 对计算机硬件（CPU、主板、内存等）的检测。 | ||
| (2) POST 之后的初始化与启动相关硬件（磁盘、键盘控制器等）。 | ||
| (3) 为 OS 创建一些参数，如 ACPI、E820 表等。 | ||
| (4) 选择引导设备，从设备中加载 BootLoader，进而启动操作系统。 | ||
| ``` | ||
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| ### 2. qemu 加载seabios过程 | ||
| ``` | ||
| (1) qemu加载 seabios 在地址的 4G 最顶端的 LOW_MMIO 区，以及低 1M 区域各有一份。 | ||
| (2) cpu 的第一条取指地址为 0xFFFFFFF0，该地址指向贴近 4G 的 BIOS 的最后 16 个字节，这也是 BIOS 的第一条指令。 | ||
| (3) BIOS 最后 16 个字节处，是一个长跳转指令，目的就是换到低 1M 段空间去执行 entry_post ( ORG 0xe05b ) | ||
| ``` | ||
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| ### 3. kbuild 使用方法 | ||
| ``` | ||
| 参考: https://github.com/Starry-OS/Starry | ||
| # To download the tool | ||
| $ cargo install kbuild | ||
| $ mkdir crates | ||
| $ kbuild patch add axstarry | ||
| $ kbuild patch remove axstarry | ||
| $ kbuild patch list | ||
| ``` | ||
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| ### 4. seabios 编译方法 | ||
| ``` | ||
| cat > .config << EOF | ||
| # for qemu machine types 2.0 + newer | ||
| CONFIG_QEMU=y | ||
| CONFIG_ROM_SIZE=256 | ||
| CONFIG_ATA_DMA=n | ||
| CONFIG_XEN=n | ||
| CONFIG_DEBUG_LEVEL=9 | ||
| CONFIG_DEBUG_SERIAL=y | ||
| EOF | ||
| echo "CONFIG_DEBUG_LEVEL=9" >> .config | ||
| make PYTHON=python3 oldnoconfig | ||
| make | ||
| ``` | ||
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| ### 5. seabios 反汇编 | ||
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| ``` | ||
| objdump -D -b binary -m i8086 bios.bin | ||
| objdump -D -b binary -m i8086 romlayout.o | ||
| -M intel : 指定intel格式 | ||
| ``` | ||
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| ### 6. kvm 中所有 port IO | ||
| 所谓端口Port IO, x86上使用in out指令进行访问, 和内存的地址空间完全隔离.(ARM上没有PIO) Guest以Linux为例: `cat /proc/ioports`查看当前OS的所有的ioports : | ||
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| ``` | ||
| 0000-0cf7 : PCI Bus 0000:00 | ||
| 0000-001f : dma1 | ||
| 0020-0021 : pic1 | ||
| 0040-0043 : timer0 | ||
| 0050-0053 : timer1 | ||
| 0060-0060 : keyboard | ||
| 0064-0064 : keyboard | ||
| 0070-0077 : rtc0 | ||
| 0080-008f : dma page reg | ||
| 00a0-00a1 : pic2 | ||
| 00c0-00df : dma2 | ||
| 00f0-00ff : fpu | ||
| 03c0-03df : vga+ | ||
| 03f8-03ff : serial | ||
| 0510-051b : QEMU0002:00 | ||
| 0510-051b : fw_cfg_io | ||
| 0600-067f : 0000:00:1f.0 | ||
| 0600-0603 : ACPI PM1a_EVT_BLK | ||
| 0604-0605 : ACPI PM1a_CNT_BLK | ||
| 0608-060b : ACPI PM_TMR | ||
| 0620-062f : ACPI GPE0_BLK | ||
| 0630-0633 : iTCO_wdt.0.auto | ||
| 0630-0633 : iTCO_wdt | ||
| 0660-067f : iTCO_wdt.0.auto | ||
| 0660-067f : iTCO_wdt | ||
| 0700-073f : 0000:00:1f.3 | ||
| 0700-073f : i801_smbus | ||
| 0cf8-0cff : PCI conf1 | ||
| 0d00-ffff : PCI Bus 0000:00 | ||
| 1000-1fff : PCI Bus 0000:01 | ||
| 2000-2fff : PCI Bus 0000:02 | ||
| 3000-3fff : PCI Bus 0000:03 | ||
| 4000-4fff : PCI Bus 0000:04 | ||
| 5000-5fff : PCI Bus 0000:05 | ||
| 6000-6fff : PCI Bus 0000:06 | ||
| 7000-7fff : PCI Bus 0000:07 | ||
| c040-c05f : 0000:00:1f.2 | ||
| c040-c05f : ahci | ||
| ``` | ||
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| ### 7. 项目实现总结 | ||
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| 项目刚开始, 我把seabios当作 kernel，写了个简单的 bios 来引导 seabios ，seabios成功运行 | ||
| ```asm | ||
| .section .text | ||
| .code16 | ||
| .global entry16 | ||
| entry16: | ||
| cli | ||
| cld | ||
| xor ax, ax | ||
| mov ds, ax | ||
| mov es, ax | ||
| ljmp 0xf000, 0xe05b | ||
| ``` | ||
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| 后面通过学习vmcs的使用方法，增加了CS寄存器的设置后，seabios 可以自启动成功。 | ||
| ```rust | ||
| VmcsGuestNW::RIP.write(entry.as_usize() & 0xffff)?; | ||
| VmcsGuest16::CS_SELECTOR.write(((entry.as_usize() >> 4) & 0xf000) as u16)?; | ||
| // On Intel requires 'base' to be 'selector * 16' in real mode. | ||
| VmcsGuestNW::CS_BASE.write(entry.as_usize() & 0xf0000)?; | ||
| ``` | ||
| 对应的linux.tmol修改为 | ||
| ```toml | ||
| cpu_num = 1 | ||
| phys_cpu_sets = [1] | ||
| entry_point = 0xf_e05b | ||
| bios_path = "bios-256k.bin" | ||
| bios_load_addr = 0xc_0000 | ||
| kernel_path = "arceos-x86_64.bin" | ||
| kernel_load_addr = 0x100_0000 | ||
| # ramdisk_path = "" | ||
| # ramdisk_load_addr = 0 | ||
| # disk_path = "disk.img" | ||
| # Memory regions with format (`base_paddr`, `size`, `flags`). | ||
| memory_regions = [ | ||
| [0x0000_0000, 0x1_0000, 0x13], # IO Port 64K 0b10011 | ||
| [0x0001_0000, 0x400_0000, 0x7], # Low RAM 64M 0b111 | ||
| [0xfec0_0000, 0x1000, 0x17], # IO APIC 4K 0b10111 | ||
| [0xfee0_0000, 0x1000, 0x17], # Local APIC 4K 0b10111 | ||
| [0xfed0_0000, 0x1000, 0x17], # HPET 4K 0b10111 | ||
| ] | ||
| # Emu_devices | ||
| # Name Base-Ipa Ipa_len Alloc-Irq Emu-Type EmuConfig | ||
| emu_devices = [ | ||
| ] | ||
| ``` | ||
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| Seabios 加载内核流程，seabios加载内核是通过 fw_cfg 的 file 接口，读取 multiboo.bin 当作 rom 来加载的，这个 multiboo.bin是linux内核封装过的带有 0x55aa 标记的可以引导的 rom，seabios读取到 rom后，加载到内存中然后执行。整理需要实现内容如下(“对号” 为截至此笔记已完成的): | ||
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| - [x] 1. seabios第一条指令地址为: 0xf000:0xe05b, 支持设置primary vcpu第一条指令地址 entry_point. | ||
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| ``` | ||
| 1. 目前实模式下还不支设置超过0xffff的地址 | ||
| 2. 考虑设置代码段 CS 寄存器 | ||
| ``` | ||
| - [x] 2. 设置虚拟化需要截获的io端口 | ||
| ``` | ||
| 有些端口需要进行截获, 否则会透传到宿主机, 获取宿主机的信息, 例如pci信息, 内存大小信息等 | ||
| ``` | ||
| - [ ] 3. dma 实现支持 | ||
| ``` | ||
| 很多数据的传输需要通过 dma 传输 | ||
| ``` | ||
| - [ ] 4. 实现fw_cfg设备模拟 | ||
| - [x] fw_cfg 实现 pio, 设备地址 [0x510, 0x511] | ||
| ``` | ||
| 告诉seabios, 虚拟化环境为 “QEMU” | ||
| ``` | ||
| - [ ] fw_cfg 实现 dma, 设备地址 [0x514] | ||
| ``` | ||
| 用于传输数据, 例如内核data数据等 | ||
| ``` | ||
| - [x] 5. 实现rtc设备模拟, 设备地址 [0x70, 0x71] | ||
| ``` | ||
| 在虚拟化环境中, seabios 通过 rtc 几个保留的寄存器获取内存大小信息 | ||
| ``` | ||
| - [ ] 6. multiboot 实现 | ||
| ``` | ||
| seabios通过内核启动是通过multiboot协议启动的, 需要将内核文件进行重新封装 | ||
| ``` | ||
| - [ ] 其他 ... | ||
| **修改链接如下:** | ||
| https://github.com/hbuxiaofei/arceos-umhv/tree/support-seabios | ||
| https://github.com/hbuxiaofei/axvcpu/tree/support-seabios | ||
| https://github.com/hbuxiaofei/x86_vcpu/tree/support-seabios | ||
| https://github.com/hbuxiaofei/axvm/tree/support-seabios | ||
| https://github.com/hbuxiaofei/axdevice/tree/support-seabios | ||
| **运行日志：** | ||
| ``` | ||
| [ 0.307806 0:2 axvm::vm:230] Booting VM[1] | ||
| [ 0.308076 0:2 arceos_vmm::vmm:40] VM[1] boot success | ||
| [ 0.308390 0:2 axtask::run_queue:393] task block: Task(2, "main") | ||
| [ 0.308757 0:3 axtask::task:471] task drop: Task(4, "") | ||
| [ 0.309079 0:3 axtask::run_queue:393] task block: Task(3, "gc") | ||
| [ 0.309436 0:5 arceos_vmm::vmm::vcpus:240] VM[1] Vcpu[0] waiting for running | ||
| [ 0.309852 0:5 arceos_vmm::vmm::vcpus:243] VM[1] Vcpu[0] running... | ||
| [ 0.310227 0:5 x86_vcpu::vmx::vcpu:118] VmxVcpu bind to current processor vmcs @ PA:0x5b2000 | ||
| [ 0.310751 0:5 axvm::vm:258] >>>>> exit_reason IoWrite { | ||
| port: 0x70, | ||
| width: Byte, | ||
| data: 0x8f, | ||
| } | ||
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| [ 0.311332 0:5 axvm::vm:289] IoWrite: 0x70 Byte 0x8f | ||
| [ 0.311646 0:5 axdevice::device:96] emu: GPA:0x70..GPA:0x72 handler write port:GPA:0x70 width:1 val:0x8f | ||
| [ 0.312180 0:5 axdevice::rtc:54] Rtc select 0xf | ||
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| [ 0.312482 0:5 axvm::vm:258] >>>>> exit_reason IoRead { | ||
| port: 0x71, | ||
| width: Byte, | ||
| } | ||
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| [ 0.312984 0:5 axvm::vm:278] IoRead: 0x71 Byte | ||
| [ 0.313268 0:5 axdevice::device:79] emu: GPA:0x70..GPA:0x72 handler read port:GPA:0x71 width:1 | ||
| [ 0.313758 0:5 axdevice::rtc:81] Rtc read addr: GPA:0x71 GPA:0x71 | ||
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| [ 0.314130 0:5 axdevice::rtc:62] Rtc get index: 0xf | ||
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| [ 0.314454 0:5 axvm::vm:258] >>>>> exit_reason Nothing | ||
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| [ 0.314787 0:5 x86_vcpu::vmx::vcpu:131] VmxVcpu unbind from current processor vmcs @ PA:0x5b2000 | ||
| [ 0.315285 0:5 x86_vcpu::vmx::vcpu:118] VmxVcpu bind to current processor vmcs @ PA:0x5b2000 | ||
| SeaBIOS (version 1.16.0-20241104_115553-centos83-dev) | ||
| BUILD: gcc: (GCC) 8.5.0 20210514 (Red Hat 8.5.0-4) binutils: version 2.30-108.el8_5.1 | ||
| enabling shadow ram | ||
| [ 0.316631 0:5 axvm::vm:258] >>>>> exit_reason IoWrite { | ||
| port: 0xcf8, | ||
| width: Dword, | ||
| data: 0x80000000, | ||
| } | ||
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| [ 0.317243 0:5 axvm::vm:289] IoWrite: 0xcf8 Dword 0x80000000 | ||
| [ 0.317586 0:5 axdevice::device:96] emu: GPA:0xcf8..GPA:0xd00 handler write port:GPA:0xcf8 width:4 val:0x80000000 | ||
| [ 0.318159 0:5 axdevice::pci:210] >>> axdevice pci write GPA:0xcf8 0x80000000... | ||
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| [ 0.318592 0:5 axdevice::pci:87] >>> set address 0x0 : device:0x0 : 0x0 : 0x0 | ||
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| [ 0.319020 0:5 axvm::vm:258] >>>>> exit_reason IoRead { | ||
| port: 0xcfc, | ||
| width: Word, | ||
| } | ||
| read QEMU_CFG_SIGNATURE 85(U) | ||
| Found QEMU fw_cfg | ||
| >>> qemu_cfg_read_entry start ... | ||
| >>> cfg read qemu_cfg_read over | ||
| >>> qemu_cfg_read_entry over ... | ||
| QEMU fw_cfg: 956659(0xe98f3) 0x2 | ||
| QEMU fw_cfg DMA interface supported | ||
| >>> qemu_early_e820 call qemu_cfg_read_entry, port:0x19 | ||
| >>> qemu_cfg_read_entry start ... | ||
| >>> cfg read qemu_cfg_dma_transfer 0x6f80 4 | ||
| >>> dma outl: 0x518 0x806f000000000000 | ||
| [ 0.508528 0:5 axvm::vm:258] >>>>> exit_reason IoWrite { | ||
| port: 0x518, | ||
| width: Dword, | ||
| data: 0x206f0000, | ||
| } | ||
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| [ 0.509263 0:5 axvm::vm:289] IoWrite: 0x518 Dword 0x206f0000 | ||
| [ 0.509671 0:5 axdevice::device:96] emu: GPA:0x510..GPA:0x522 handler write port:GPA:0x518 width:4 val:0x206f0000 | ||
| [ 0.510356 0:5 axdevice::fwcfg:238] >>> do_write GPA:0x518 4 0x206f0000 | ||
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| [ 0.510837 0:5 axdevice::fwcfg:226] dma_write: GPA:0x518 0x206f0000 | ||
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| >>> dma outl over: 0x518 0x806f000000000000 | ||
| QEMU: Terminated | ||
| ``` | ||
| --- | ||
| **参考文档:** | ||
| [SeaBIOS实现简单分析](https://www.cnblogs.com/gnuemacs/p/14287120.html) | ||
| [浅度剖析 SeaBIOS 之 QEMU 初始化](https://zhuanlan.zhihu.com/p/678576761) | ||
| <<Qemu/kvm源码解析与应用>> - 李强 |