时间轴

2025-12-31

init

环境

OS

使用wsl的archlinux

环境

compiler

ARM目前总共发布了8种架构：ARMv1、ARMv2、ARMv3、ARMv4、ARMv5、ARMv6、ARMv7、ARMv8。

针对于Cortex-A5x处理器可以使用aarch64-linux-gnu-gcc -march=armv8-a命令编译代码，ARM GNU编译器可通过下面的链接下载

Arm GNU Toolchain Downloads

https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads

我使用的是archlinux上通过pacman下载的aarch64-linux-gnu-gcc版本是15.1.0

aarch64-linux-gnu-gcc

编译内核

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git clone --branch rpi-5.10.y --single-branch https://github.com/raspberrypi/linux.git
make mrproper
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- bcm2711_defconfig
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- modules_prepare
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- Image modules dtbs -j$(nproc)

# 这一步安装驱动，拷贝到根文件系统
make modules_install INSTALL_MOD_PATH=/home/zhaohang/repository/linux/busybox-1.37.0/_install/

mkdir -p ~/tftp/raspi4b
cp arch/arm64/boot/Image ~/tftp/raspi4b
cp arch/arm64/boot/dts/broadcom/bcm2711-rpi-4-b.dtb ~/tftp/raspi4b

输出：

  • arch/arm64/boot/Image
  • arch/arm64/boot/dts/broadcom/bcm2711-rpi-4-b.dtb

编译根文件系统

busybox

参考：

最小Linux系统编译运行

https://even629.com/posts/42869

buildroot

Archlinux默认工具链及AUR提供的交叉工具链都是无法复制使用的，Buildroot在构建时会将工具链复制到工作目录执行，因此我们需要选择Portable的工具链二进制或者选择crosstool-NG编译工具链。

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wget https://buildroot.org/downloads/buildroot-2025.11.tar.gz
# WSL下PATH含有空格，临时重新设置
export PATH=/home/zhaohang/.nvm/versions/node/v20.19.4/bin:/home/zhaohang/.cargo/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/usr/lib/wsl/lib

tar xvf buildroot-2025.11.tar.gz

make menucofig

TODO

Yocto

TODO

内核模块

内核模块示例

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#include <linux/init.h>
#include <linux/module.h>

static int __init hello_world_init(void){
        printk(KERN_INFO "hello world!\n");
        return 0;
}

static void __exit hello_world_exit(void){
        pr_info("hello world module exit\n");
}
module_init(hello_world_init);
module_exit(hello_world_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("even629");
MODULE_DESCRIPTION("hello world!");

external module

Makefile

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DRIVER_NAME := hello_world

obj-m += $(DRIVER_NAME).o
KERNEL_SRC:=/home/zhaohang/repository/linux/linux-5.10.y-raspi

PWD ?=$(shell pwd)
ARCH = arm64
CROSS_COMPILE = aarch64-linux-gnu-


all: build

build:
	$(MAKE) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) -C $(KERNEL_SRC) M=$(PWD) modules

clean:
	$(MAKE) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) -C $(KERNEL_SRC) M=$(PWD) modules clean
	rm -rf *.ko *.o *.mod.o *.mod.c *.symvers *.order .tmp*

.PHONY: all deploy qemu
deploy:
	cp $(DRIVER_NAME).ko /home/zhaohang/repository/linux/busybox-1.37.0/_install
	/bin/bash /home/zhaohang/repository/linux/busybox-1.37.0/deploy.sh

qemu:
	qemu-system-aarch64 \
		-M raspi4b \
		-cpu cortex-a72 \
		-m 2G \
		-nographic \
		-kernel /home/zhaohang/tftp/raspi4b/Image \
		-dtb /home/zhaohang/tftp/raspi4b/bcm2711-rpi-4-b.dtb \
		-initrd /home/zhaohang/tftp/initramfs.cpio.gz \
		-append "console=ttyAMA0 earlycon=pl011,0xfe201000 rdinit=/linuxrc"

其中打包根文件系统的脚本deploy.sh如下：

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#!/bin/bash

INSTALL_PATH=/home/zhaohang/repository/linux/busybox-1.37.0/_install

cd "$INSTALL_PATH" || exit 1

rm -rf ../initramfs.cpio.gz ~/tftp/initramfs.cpio.gz

find . | cpio -o -H newc | gzip -c > ../initramfs.cpio.gz

cp ../initramfs.cpio.gz ~/tftp

echo "cp initramfs.cpio.gz ~/tftp"

遇到一个问题是 aarch64-linux-gnu-gcc 编译时没 print 目前没找到解决办法，在 stackoverflow 上详细描述了具体问题：

No gcc compiling log CC [M] showing up

https://stackoverflow.com/questions/79858012/

built-in module

在drivers/char(以字符驱动为例)创建文件夹helloworld，然后将驱动源代码放入，然后创建Kconfig文件

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config HELLO_WORLD
  bool "helloworld support"
  default y
  help
      helloworld

更改drivers

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emacs ../Kconfig
# 添加
source "drivers/char/helloworld/Kconfig"

在驱动源码里创建Makefile

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obj-$(CONFIG_helloworld) += helloworld.o

然后在上一级的Makefile中添加：

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emacs ../Makefile
# 添加
obj-y += helloworld/

然后编译内核即可

启动

直接指定内核启动

qemu 运行

qemu版本

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$ qemu-system-aarch64 --version
QEMU emulator version 10.1.2
Copyright (c) 2003-2025 Fabrice Bellard and the QEMU Project developers

运行

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qemu-system-aarch64 \
  -M raspi4b \
  -cpu cortex-a72 \
  -m 2G \
  -nographic \
  -kernel /home/zhaohang/tftp/raspi4b/Image \
  -dtb /home/zhaohang/tftp/raspi4b/bcm2711-rpi-4-b.dtb \
  -initrd /home/zhaohang/tftp/initramfs.cpio.gz \
  -append "console=ttyAMA0 earlycon=pl011,0xfe201000 rdinit=/linuxrc"

结果：

按command + a, 然后按 x 可以退出qemu

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$ qemu-system-aarch64 \
  -M raspi4b \
  -cpu cortex-a72 \
  -m 2G \
  -nographic \
  -kernel /home/zhaohang/tftp/raspi4b/Image \
  -dtb /home/zhaohang/tftp/raspi4b/bcm2711-rpi-4-b.dtb \
  -initrd /home/zhaohang/tftp/initramfs.cpio.gz \
  -append "console=ttyAMA0 earlycon=pl011,0xfe201000 rdinit=/linuxrc"

qemu-system-aarch64: warning: bcm2711 dtc: brcm,bcm2711-pcie has been disabled!
qemu-system-aarch64: warning: bcm2711 dtc: brcm,bcm2711-rng200 has been disabled!
qemu-system-aarch64: warning: bcm2711 dtc: brcm,bcm2711-thermal has been disabled!
qemu-system-aarch64: warning: bcm2711 dtc: brcm,bcm2711-genet-v5 has been disabled!
[    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd083]
[    0.000000] Linux version 5.10.110-v8+ (zhaohang@cyberboy) (aarch64-linux-gnu-gcc (GCC) 15.1.0, GNU ld (GNU Binutils) 2.44) #1 SMP PREEMPT Wed Dec 31 13:58:35 CST 2025
[    0.000000] Machine model: Raspberry Pi 4 Model B
[    0.000000] earlycon: pl11 at MMIO 0x00000000fe201000 (options '')
[    0.000000] printk: bootconsole [pl11] enabled
[    0.000000] efi: UEFI not found.
[    0.000000] Reserved memory: created CMA memory pool at 0x000000002c000000, size 64 MiB
[    0.000000] OF: reserved mem: initialized node linux,cma, compatible id shared-dma-pool
[    0.000000] Zone ranges:
[    0.000000]   DMA      [mem 0x0000000000000000-0x000000003bffffff]
[    0.000000]   DMA32    empty
[    0.000000]   Normal   empty
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000000000000-0x000000003bffffff]
[    0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x000000003bffffff]
[    0.000000] percpu: Embedded 32 pages/cpu s91416 r8192 d31464 u131072
[    0.000000] Detected PIPT I-cache on CPU0
[    0.000000] CPU features: detected: Spectre-v2
[    0.000000] CPU features: detected: Spectre-v4
[    0.000000] CPU features: detected: ARM errata 1165522, 1319367, or 1530923
[    0.000000] CPU features: detected: Spectre-BHB
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 241920
[    0.000000] Kernel command line: console=ttyAMA0 earlycon=pl011,0xfe201000 rdinit=/linuxrc
[    0.000000] Dentry cache hash table entries: 131072 (order: 8, 1048576 bytes, linear)
[    0.000000] Inode-cache hash table entries: 65536 (order: 7, 524288 bytes, linear)
[    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[    0.000000] Memory: 871688K/983040K available (11456K kernel code, 1948K rwdata, 3968K rodata, 3648K init, 1255K bss, 45816K reserved, 65536K cma-reserved)
[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
[    0.000000] ftrace: allocating 35594 entries in 140 pages
[    0.000000] ftrace: allocated 140 pages with 3 groups
[    0.000000] rcu: Preemptible hierarchical RCU implementation.
[    0.000000] rcu: 	RCU event tracing is enabled.
[    0.000000] rcu: 	RCU restricting CPUs from NR_CPUS=256 to nr_cpu_ids=4.
[    0.000000] 	Trampoline variant of Tasks RCU enabled.
[    0.000000] 	Rude variant of Tasks RCU enabled.
[    0.000000] 	Tracing variant of Tasks RCU enabled.
[    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
[    0.000000] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=4
[    0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
[    0.000000] GIC: Using split EOI/Deactivate mode
[    0.000000] random: get_random_bytes called from start_kernel+0x3c0/0x59c with crng_init=0
[    0.000000] arch_timer: cp15 timer(s) running at 62.50MHz (phys).
[    0.000000] clocksource: arch_sys_counter: mask: 0xffffffffffffff max_cycles: 0x1cd42e208c, max_idle_ns: 881590405314 ns
[    0.000193] sched_clock: 56 bits at 62MHz, resolution 16ns, wraps every 4398046511096ns
[    0.010464] Console: colour dummy device 80x25
[    0.012840] Calibrating delay loop (skipped), value calculated using timer frequency.. 125.00 BogoMIPS (lpj=250000)
[    0.014064] pid_max: default: 32768 minimum: 301
[    0.016215] LSM: Security Framework initializing
[    0.020951] Mount-cache hash table entries: 2048 (order: 2, 16384 bytes, linear)
[    0.021396] Mountpoint-cache hash table entries: 2048 (order: 2, 16384 bytes, linear)
[    0.045807] cgroup: Disabling memory control group subsystem
[    0.083754] rcu: Hierarchical SRCU implementation.
[    0.090257] EFI services will not be available.
[    0.096869] smp: Bringing up secondary CPUs ...
[    0.102608] Detected PIPT I-cache on CPU1
[    0.103412] CPU1: Booted secondary processor 0x0000000001 [0x410fd083]
[    0.109872] Detected PIPT I-cache on CPU2
[    0.110218] CPU2: Booted secondary processor 0x0000000002 [0x410fd083]
[    0.114286] Detected PIPT I-cache on CPU3
[    0.114544] CPU3: Booted secondary processor 0x0000000003 [0x410fd083]
[    0.115437] smp: Brought up 1 node, 4 CPUs
[    0.117473] SMP: Total of 4 processors activated.
[    0.117813] CPU features: detected: 32-bit EL0 Support
[    0.118151] CPU features: detected: CRC32 instructions
[    0.118532] CPU features: detected: 32-bit EL1 Support
[    0.578725] CPU: All CPU(s) started at EL2
[    0.579912] alternatives: patching kernel code
[    0.598893] devtmpfs: initialized
[    0.622587] Enabled cp15_barrier support
[    0.623314] Enabled setend support
[    0.625268] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
[    0.626042] futex hash table entries: 1024 (order: 4, 65536 bytes, linear)
[    0.633888] pinctrl core: initialized pinctrl subsystem
[    0.646644] DMI not present or invalid.
[    0.649138] NET: Registered protocol family 16
[    0.666179] DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
[    0.668378] DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA pool for atomic allocations
[    0.669231] DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA32 pool for atomic allocations
[    0.670265] audit: initializing netlink subsys (disabled)
[    0.672976] audit: type=2000 audit(0.636:1): state=initialized audit_enabled=0 res=1
[    0.676692] thermal_sys: Registered thermal governor 'step_wise'
[    0.679732] cpuidle: using governor menu
[    0.681470] hw-breakpoint: found 6 breakpoint and 4 watchpoint registers.
[    0.683105] ASID allocator initialised with 65536 entries
[    0.685145] Serial: AMBA PL011 UART driver
[    0.732159] bcm2835-mbox fe00b880.mailbox: mailbox enabled
[    0.745081] raspberrypi-firmware soc:firmware: Attached to firmware from 1970-01-05T00:12:17, variant unknown
[    0.748848] raspberrypi-firmware soc:firmware: Firmware hash is ffffffc01076a644ffffffc00208f410ffffff80
[    0.822131] bcm2835-dma fe007000.dma: DMA legacy API manager, dmachans=0x1
[    0.837203] vgaarb: loaded
[    0.839372] SCSI subsystem initialized
[    0.840912] usbcore: registered new interface driver usbfs
[    0.841539] usbcore: registered new interface driver hub
[    0.843435] usbcore: registered new device driver usb
[    0.845401] usb_phy_generic phy: supply vcc not found, using dummy regulator
[    0.861298] clocksource: Switched to clocksource arch_sys_counter
[    1.389615] VFS: Disk quotas dquot_6.6.0
[    1.390036] VFS: Dquot-cache hash table entries: 512 (order 0, 4096 bytes)
[    1.391320] FS-Cache: Loaded
[    1.392956] CacheFiles: Loaded
[    1.430221] NET: Registered protocol family 2
[    1.432440] IP idents hash table entries: 16384 (order: 5, 131072 bytes, linear)
[    1.441074] tcp_listen_portaddr_hash hash table entries: 512 (order: 1, 8192 bytes, linear)
[    1.442094] TCP established hash table entries: 8192 (order: 4, 65536 bytes, linear)
[    1.442942] TCP bind hash table entries: 8192 (order: 5, 131072 bytes, linear)
[    1.443407] TCP: Hash tables configured (established 8192 bind 8192)
[    1.446113] UDP hash table entries: 512 (order: 2, 16384 bytes, linear)
[    1.446615] UDP-Lite hash table entries: 512 (order: 2, 16384 bytes, linear)
[    1.448824] NET: Registered protocol family 1
[    1.454548] RPC: Registered named UNIX socket transport module.
[    1.454926] RPC: Registered udp transport module.
[    1.455348] RPC: Registered tcp transport module.
[    1.455688] RPC: Registered tcp NFSv4.1 backchannel transport module.
[    1.456251] PCI: CLS 0 bytes, default 64
[    1.462406] Trying to unpack rootfs image as initramfs...
[    1.613750] Freeing initrd memory: 2620K
[    1.622022] hw perfevents: enabled with armv8_cortex_a72 PMU driver, 7 counters available
[    1.623833] kvm [1]: IPA Size Limit: 44 bits
[    1.630628] kvm [1]: vgic interrupt IRQ9
[    1.633763] kvm [1]: Hyp mode initialized successfully
[    1.640641] Initialise system trusted keyrings
[    1.643688] workingset: timestamp_bits=46 max_order=18 bucket_order=0
[    1.654869] zbud: loaded
[    1.662206] FS-Cache: Netfs 'nfs' registered for caching
[    1.665400] NFS: Registering the id_resolver key type
[    1.666028] Key type id_resolver registered
[    1.666374] Key type id_legacy registered
[    1.667309] nfs4filelayout_init: NFSv4 File Layout Driver Registering...
[    1.667733] nfs4flexfilelayout_init: NFSv4 Flexfile Layout Driver Registering...
[    1.672284] Key type asymmetric registered
[    1.672591] Asymmetric key parser 'x509' registered
[    1.673460] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 249)
[    1.675599] io scheduler mq-deadline registered
[    1.675906] io scheduler kyber registered
[    1.686720] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 0 config (0 80)
[    1.687615] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 1 config (0 81)
[    1.688402] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 2 config (0 82)
[    1.689028] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 3 config (0 83)
[    1.690019] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 4 config (0 84)
[    1.691028] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 5 config (0 85)
[    1.691837] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 6 config (0 86)
[    1.692510] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 7 config (0 87)
[    1.695839] bcm2708_fb soc:fb: FB found 1 display(s)
[    1.718250] Console: switching to colour frame buffer device 100x30
[    1.722108] bcm2708_fb soc:fb: Registered framebuffer for display 0, size 800x480
[    1.734253] bcm2835-aux-uart fe215040.serial: there is not valid maps for state default
[    1.739449] vc-mem: phys_addr:0x00000000 mem_base=0x00000000 mem_size:0x00000000(0 MiB)
[    1.744011] gpiomem-bcm2835 fe200000.gpiomem: Initialised: Registers at 0xfe200000
[    1.795533] brd: module loaded
[    1.827118] loop: module loaded
[    1.830068] bcm2835-power bcm2835-power: ASB register ID returned 0x00000000
[    1.834080] Loading iSCSI transport class v2.0-870.
[    1.847058] usbcore: registered new interface driver r8152
[    1.847425] usbcore: registered new interface driver lan78xx
[    1.848003] usbcore: registered new interface driver smsc95xx
[    1.849618] dwc_otg: version 3.00a 10-AUG-2012 (platform bus)
[    1.853436] usbcore: registered new interface driver uas
[    1.854435] usbcore: registered new interface driver usb-storage
[    1.855744] mousedev: PS/2 mouse device common for all mice
[    1.863346] bcm2835-wdt bcm2835-wdt: Broadcom BCM2835 watchdog timer
[    1.875392] sdhci: Secure Digital Host Controller Interface driver
[    1.875688] sdhci: Copyright(c) Pierre Ossman
[    1.880324] mmc-bcm2835 fe300000.mmcnr: could not get clk, deferring probe
[    1.883910] sdhci-pltfm: SDHCI platform and OF driver helper
[    1.891370] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 2 config (0 82)
[    1.892339] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 2 state (0 82)
[    1.895277] leds-gpio: probe of leds failed with error -5
[    1.898076] ledtrig-cpu: registered to indicate activity on CPUs
[    1.899717] hid: raw HID events driver (C) Jiri Kosina
[    1.900620] usbcore: registered new interface driver usbhid
[    1.900923] usbhid: USB HID core driver
[    1.902099] ashmem: initialized
[    1.914219] Initializing XFRM netlink socket
[    1.914676] NET: Registered protocol family 17
[    1.916084] Key type dns_resolver registered
[    1.918003] registered taskstats version 1
[    1.918337] Loading compiled-in X.509 certificates
[    1.921669] Key type ._fscrypt registered
[    1.921956] Key type .fscrypt registered
[    1.922228] Key type fscrypt-provisioning registered
[    1.946131] uart-pl011 fe201000.serial: there is not valid maps for state default
[    1.947582] uart-pl011 fe201000.serial: cts_event_workaround enabled
[    1.948980] fe201000.serial: ttyAMA0 at MMIO 0xfe201000 (irq = 21, base_baud = 0) is a PL011 rev2
[    1.951840] printk: console [ttyAMA0] enabled
[    1.951840] printk: console [ttyAMA0] enabled
[    1.952714] printk: bootconsole [pl11] disabled
[    1.952714] printk: bootconsole [pl11] disabled
[    1.956755] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 6 config (0 86)
[    1.958798] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 6 config (0 86)
[    1.959403] reg-fixed-voltage: probe of sd_vcc_reg failed with error -5
[    1.962175] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 5 config (0 85)
[    1.963390] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 5 config (0 85)
[    1.963832] reg-fixed-voltage: probe of cam1_regulator failed with error -5
[    1.965762] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 4 config (0 84)
[    1.967667] raspberrypi-exp-gpio soc:firmware:gpio: Failed to get GPIO 4 config (0 84)
[    1.968063] gpio-regulator: probe of sd_io_1v8_reg failed with error -5
[    1.971127] bcm2835-aux-uart fe215040.serial: there is not valid maps for state default
[    1.972594] bcm2835-aux-uart fe215040.serial: error -ENOSPC: unable to register 8250 port
[    1.973450] bcm2835-aux-uart: probe of fe215040.serial failed with error -28
[    1.976078] mmc-bcm2835 fe300000.mmcnr: mmc_debug:0 mmc_debug2:0
[    1.976376] mmc-bcm2835 fe300000.mmcnr: DMA channel allocated
[    2.011143] of_cfs_init
[    2.014686] of_cfs_init: OK
[    2.022747] uart-pl011 fe201000.serial: no DMA platform data
[    2.068740] Freeing unused kernel memory: 3648K
[    2.072213] Run /linuxrc as init process

Please press Enter to activate this console.
~ # insmod my_driver.ko
[   19.030715] my_driver: loading out-of-tree module taints kernel.
[   19.040713] alloc_chrdev_region ok
[   19.041036] major allocated: 241
[   19.041063] minor allocated: 0
[   19.041707] cdev_add ok
[   19.043310] my_driver: Module loaded
~ # rmmod my_driver.ko
[   24.994821] unregister_chrdev_region ok
[   24.995218] my_driver: Module unloaded
~ #

u-boot启动

这种方法暂时启动不起来，不知道为什么

编译u-boot

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git clone https://github.com/u-boot/u-boot.git
make clean
make ARCH=arm CROSS_COMPILE=aarch64-linux-gnu- rpi_4_defconfig

make ARCH=arm CROSS_COMPILE=aarch64-linux-gnu- -j$(nproc)
cp u-boot.bin ~/tftp/raspi4b/u-boot.bin
cp u-boot ~/tftp/raspi4b/u-boot

最终编译生成ELF格式的可执行文件 u-boot 和纯二进制文件u-boot.bin，其中 QEMU 可以启动的为ELF格式的可执行文件 u-boot。

制作SD卡镜像

制作sd卡镜像，并将它格式化成fat格式

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dd if=/dev/zero of=/home/zhaohang/tftp/raspi4b/sd.img bs=1M count=256

sudo pacman -S dosfstools
sudo fdisk /home/zhaohang/tftp/raspi4b/sd.img
# n	新建分区
# p	主分区
# 1	分区号 1
#（enter）	默认起始(通常是2048)
# +128M	大小 128MB
# t          # 修改分区类型
# 1          # 选择分区 1
# b          # 设置为 W95 FAT32

# n	新建第二个分区
# p	主分区
# 2	分区号 2
# (enter)	默认起始
# (enter)	默认终止
# t          # 修改分区类型
# 2          # 选择分区 1
# 83          # 设置为 Linux
# p
Command (m for help): p
Disk /home/zhaohang/tftp/raspi4b/sd.img: 256 MiB, 268435456 bytes, 524288 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x8cf943ea

Device                              Boot  Start    End Sectors  Size Id Type
/home/zhaohang/tftp/raspi4b/sd.img1        2048 264191  262144  128M  b W95 FAT32
/home/zhaohang/tftp/raspi4b/sd.img2      264192 524287  260096  127M 83 Linux
# w	写入并退出

把编译好的kernel Image和DTB文件拷贝到sd.img中

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$ sudo losetup -Pf --show /home/zhaohang/tftp/raspi4b/sd.img
/dev/loop0
$ lsblk
NAME      MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0       7:0    0   256M  0 loop
├─loop0p1 259:0    0   128M  0 part
└─loop0p2 259:1    0   127M  0 part
sda         8:0    0 388.6M  1 disk
sdb         8:16   0   186M  1 disk
sdc         8:32   0     1G  0 disk [SWAP]
sdd         8:48   0     1T  0 disk /mnt/wslg/distro

# 格式化第一个分区为 FAT32（boot 分区）
$ sudo mkfs.vfat /dev/loop0p1
# 格式化第二个分区为 ext4（rootfs 分区）
$ sudo mkfs.ext4 /dev/loop0p2

# 挂载 boot 分区（FAT32）
$ sudo mount /dev/loop0p1 /mnt/
# 拷贝内核和设备树,uboot
$ sudo cp ~/tftp/raspi4b/Image /mnt/
$ sudo cp ~/tftp/raspi4b/bcm2711-rpi-4-b.dtb /mnt/
$ sudo cp ~/tftp/raspi4b/u-boot.bin /mnt/
$ sudo umount /dev/loop0p1

# 挂载 rootfs 分区（ext4）
$ sudo mount /dev/loop0p2 /mnt
# 拷贝rootfs
$ sudo cp ~/tftp/initramfs.cpio.gz /mnt
$ cd /mnt
# 解压 initramfs.cpio.gz 到当前目录（即 rootfs 根）
$ sudo gunzip -c ~/tftp/initramfs.cpio.gz | sudo cpio -idmv
$ sudo rm initramfs.cpio.gz
$ cd ~
$ sudo umount /dev/loop0p2

$ sudo losetup -d /dev/loop0

qemu运行

QEMU可以模拟sd卡等外设。我们就把编译好的固件放在一个模拟的sd卡上，让QEMU从这张模拟的sd卡上启动Linux系统。

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qemu-system-aarch64 \
  -M raspi4b \
  -cpu cortex-a72 \
  -m 2G \
  -nographic \
  -kernel /home/zhaohang/tftp/raspi4b/u-boot
  -sd /home/zhaohang/tftp/raspi4b/sd.img

参考

[1]
在QEMU中启动U-Boot和内核
[2]
Arch Linux下使用预装工具链配置Buildroot的解决方案