# preempt_rt kernel compile

[EC-master blog post](https://www.acontis.com/zh/blog.html)
several realtime kernel setting, install

make sure your linux kernel version, and modify the relevent part in instruction below.
- [Building a Real-time Linux Kernel in Ubuntu with PREEMPT_RT](https://www.acontis.com/en/building-a-real-time-linux-kernel-in-ubuntu-preemptrt.html)
- [Linux RT补丁/分析/性能测试(@Ubuntu)](https://www.cnblogs.com/arnoldlu/p/9065912.html)
- 舊版 linux kernel 對 preempt 的 config 位置不同。

---

some `.config` need to modify

`*** 沒有規則可製作目標「debian/canonical-certs.pem」，由「certs/x509_certificate_list」 需求。 停止。`
[ Linux Kernel & 文件系统编译 ](https://blog.wjhwjhn.com/archives/811/)
[ Linux 内核编译，终于实践了 ](https://juejin.cn/post/7082548338431623176)

`sudo make -j8`

---

Finally, grub menu will help you enter specific kernel.
[如何開啟 GRUB 選單？](https://magiclen.org/grub-menu)

## example arm

First of all check your gcc version and path

which arm-linux-gnueabihf-gcc

> /usr/bin/arm-linux-gnueabihf-gcc

or you can prepare your own cross compiler

> CC=/home/morgana/x-tools/arm-cortexa9_neon-linux-gnueabihf/bin/arm-cortexa9_neon-linux-gnueabihf-gcc
CXX=/home/morgana/x-tools/arm-cortexa9_neon-linux-gnueabihf/bin/arm-cortexa9_neon-linux-gnueabihf-g++
LD=/home/morgana/x-tools/arm-cortexa9_neon-linux-gnueabihf/bin/arm-cortexa9_neon-linux-gnueabihf-ld

` wget https://mirrors.edge.kernel.org/pub/linux/kernel/v4.x/linux-4.4.19.tar.gz`

`wget https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.4/older/patch-4.4.19-rt27.patch.xz`

很奇怪的是，板子顯示的是 `4.4.19-rt25` ，但根本沒有 rt25 的 patch。

### am437x sdk

--> 要去官網下載對應版本的sdk，[Linux-RT Processor SDK for AM437x 03.01.00.06 (02 Oct 2016)](https://www.ti.com/tool/download/PROCESSOR-SDK-LINUX-RT-AM437X/03.01.00.06)
`cd ~/board-support/linux-rt-4.4.19+gitAUTOINC+f572d285f0-gf572d285f0`

ti_config_fragments/defconfig_builder.sh

         1. SDK_Debug_Defconfigs
         2. SDK_Release_Defconfigs

Please choose a defconfig type to build for or 'q' to exit: 2
Available SDK_Release_Defconfigs defconfig build options:

        1. ti_sdk_am3x_release
        2. ti_sdk_am4x_release
        3. ti_sdk_dra7x_release
        4. ti_sdk_omap2_release
        5. ti_sdk_k2g_release
        6. ti_sdk_keystone_release
        7. ti_sdk_am3x_rt_release
        8. ti_sdk_am4x_rt_release
        9. ti_sdk_dra7x_rt_release
        10. ti_sdk_omap2_rt_release
        11. ti_sdk_k2g_rt_release
        12. ti_sdk_keystone_rt_release

Please enter the number of the defconfig to build or 'q' to exit: 8
Creating defconfig file /home/morgana/board-support/linux-rt-4.4.19+gitAUTOINC+f572d285f0-gf572d285f0/arch/arm/configs/ti_sdk_am4x_rt_release_defconfig

[SDK Kernel Configuration](https://software-dl.ti.com/processor-sdk-linux/esd/docs/05_03_00_07/linux/Foundational_Components_Kernel_Users_Guide.html)

export CROSS_COMPILE=/home/morgana/x-tools/arm-cortexa9_neon-linux-gnueabihf/bin/arm-cortexa9_neon-linux-gnueabihf-
export ARCH=arm
ti_sdk_am4x_rt_release_defconfig
make

if you have previous build, plz `make clean` first.

#### bug

[解決"multiple definition of yylloc"問題](https://steward-fu.github.io/website/phone/pixel3axl/dd_fix_yylloc.htm)

---

can find this `.confing` file through

[Obtain Kernel Config from Currently Running Linux System](https://www.baeldung.com/linux/kernel-config)

---

cross compiler tool **prefix**?:`arm-linux-gnueabihf-`

or

`export CROSS_COMPILE=arm-none-linux-gnueabi-`
`export CROSS_COMPILE=/home/morgana/x-tools/arm-cortexa9_neon-linux-gnueabihf/bin/arm-cortexa9_neon-linux-gnueabihf-`

may need to `make clean` first

aware env variable is case sensitive and necessary.
`make ARCH=arm`

[几种linux内核文件的区别(vmlinux、zImage、bzImage、uImage、vmlinuz、initrd )](https://blog.csdn.net/hanxuefan/article/details/7454352), default create the `zImage`.

  CC      kernel/bounds.s
gcc: error: unrecognized argument in option ‘-mabi=aapcs-linux’
gcc: note: valid arguments to ‘-mabi=’ are: ms sysv
gcc: error: unrecognized command-line option ‘-mlittle-endian’
gcc: error: unrecognized command-line option ‘-mapcs’
gcc: error: unrecognized command-line option ‘-mno-sched-prolog’
gcc: error: unrecognized command-line option ‘-mno-thumb-interwork’
gcc: error: unrecognized command-line option ‘-mfpu=vfp’
make[1]: *** [Kbuild:45: kernel/bounds.s] Error 1
make: *** [Makefile:990: prepare0] Error 2

[kernel编译报错|/bin/sh: 1: bc: not found](https://blog.csdn.net/qq_28837389/article/details/118100687)

[解決"multiple definition of yylloc"問題](https://steward-fu.github.io/website/phone/pixel3axl/dd_fix_yylloc.htm)

成果都在 linux/arch/arm/boot