利用buildroot(內置qemu)和vscode開發調試linux

我的其他博客有關於buildroot怎么用的介紹。

 

　　比如 buildroot-2020.11.1/configs/qemu_arm_vexpress_defconfig 這個配置。

make qemu_arm_vexpress_defconfig
make

　　就能得到：

  ./start-qemu.sh 是運行qemu的shell腳本，同時加載kernel(zImage)，dtb，rootfs。

用vscode調試：

buildroot：　

 

buildroot默認不下載編譯gdb，需要 make menuconfig勾選：
　　Toolchain  --->     [*] Build cross gdb for the host


buildroot里面的linux，默認配置一般也是關閉了debug，直接 make linux-menuconfig 去勾選：

　　 Kernel hacking  --->      [*] Kernel debugging 
 Compile-time checks and compiler options  --->   [*] Compile the kernel with debug info  

可以用這條命令，驗證kernel的編譯輸出里，有沒有debug info：
readelf -e /home/mmm/buildroot-2020.11.1/output/build/linux-rel_imx_5.4.24_2.1.0/vmlinux

有這樣的段就對了：

[32] .debug_line PROGBITS 00000000 d1fe36 f1d5ed 00 0 0 1
[33] .debug_info PROGBITS 00000000 1c3d423 7b50e92 00 0 0 1
[34] .debug_abbrev PROGBITS 00000000 978e2b5 46824b 00 0 0 1
[35] .debug_aranges PROGBITS 00000000 9bf6500 015e70 00 0 0 8
[36] .debug_str PROGBITS 00000000 9c0c370 2727f8 01 MS 0 0 1
[37] .debug_ranges PROGBITS 00000000 9e7eb68 4c78e0 00 0 0 8
[38] .debug_frame PROGBITS 00000000 a346448 16279c 00 0 0 4
[39] .debug_loc PROGBITS 00000000 a4a8be4 5b328b 00 0 0 1

 

qemu：

 

export PATH="/home/mmm/buildroot-2020.11.1/output/host/bin:${PATH}"

# dtc -I dtb -O dts vexpress-v2p-ca9.dtb -o vexpress-v2p-ca9-all.dts

qemu-system-arm \
-M vexpress-a9 \
-smp 1 \
-m 256 \
-kernel ${IMAGE_DIR}/zImage \
-dtb ${IMAGE_DIR}/vexpress-v2p-ca9.dtb \
-drive file=${IMAGE_DIR}/rootfs.ext2,if=sd,format=raw \
-append "console=ttyAMA0,115200 rootwait root=/dev/mmcblk0"  \
-nographic \
-gdb tcp::12451 \
-S \

 

-gdb tcp::12451  //從qemu里引出gdb server到宿主機的 tcp::12451端口

-S                       //在第一條指令處暫停，等待gdb連接
-smp 1               //我在調試單核CPU，調試多核的linux（SMP）要改這個地方

 

 

 

vscode：自帶gdb插件，操作方法自己搜，關鍵是這個文件

 

buildroot-2020.11.1/output/build/linux-5.4.58/.vscode/launch.json

 

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "(gdb) Launch",
            "type": "cppdbg",
            "request": "launch",
            "program": "/home/mmm/buildroot-2020.11.1/output/build/linux-5.4.58/vmlinux",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "miDebuggerServerAddress": "localhost:12451",
            "miDebuggerPath": "/home/mmm/buildroot-2020.11.1/output/host/bin/arm-buildroot-linux-uclibcgnueabihf-gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ]
        }
    ]
}

　　

另外：configs下的其他配置也可以用qemu跑，只是外設等可能沒有。

比如 imx6-sabresd_defconfig：

#!/bin/sh
IMAGE_DIR="${0%/*}/"

# if [ "${1}" = "serial-only" ]; then
#     EXTRA_ARGS='-nographic'
# else
#     EXTRA_ARGS='-serial stdio'
# fi

export PATH="/home/mmm/buildroot-2020.11.1/output/host/bin:${PATH}"
# dtc -I dtb -O dts imx6dl-sabresd.dtb -o dec.dts
# qemu-img resize -f raw --shrink ${IMAGE_DIR}/rootfs.ext2 32M

qemu-system-arm \
-M sabrelite \
-smp 1 \
-m 1G \
-nographic \
-kernel ${IMAGE_DIR}/zImage \
-dtb ${IMAGE_DIR}/imx6dl-sabresd.dtb \
-drive file=${IMAGE_DIR}/rootfs.ext2,format=raw,id=mysdcard \
-device sd-card,drive=mysdcard \
-append "console=ttymxc0 rootfstype=ext2 rootwait root=/dev/mmcblk3"  \
-gdb tcp::12451 \
-S \

 

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "(gdb) Launch",
            "type": "cppdbg",
            "request": "launch",
            "program": "/home/mmm/buildroot-2020.11.1/output/build/linux-rel_imx_5.4.24_2.1.0/vmlinux",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "miDebuggerServerAddress": "localhost:12451",
            "miDebuggerPath": "/home/mmm/buildroot-2020.11.1/output/host/bin/arm-buildroot-linux-uclibcgnueabihf-gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ]
        }
    ]
}

 

樹莓派也可以這么做，qemu對樹莓派的支持很好。

查看qemu對外設的支持可以在編譯完成后。看這個文件夾：buildroot-2020.11.1/output/build/host-qemu-5.1.0/hw/arm/vexpress.c