I am building my Embedded Linux system using Yocto warrior on Ubuntu 18.04. I have my own core image recipe and an initramfs image recipe.
I've been reading the docs ( https://www.yoctoproject.org/docs/current/mega-manual/mega-manual.html#var-INITRAMFS_IMAGE ) and various posts on the internet in order to come up with the following in my local.conf:
# Use the INITRAMFS bundled in kernel
#KERNEL_IMAGETYPE = "Image-initramfs-jetson-nano.bin"
#KERNEL_IMAGE_BASE_NAME = "Image-initramfs-jetson-nano.bin"
#INITRAMFS_LINK_NAME = ""
INITRAMFS_NAME = "Initramfs"
INITRAMFS_IMAGE = "tegra-minimal-initramfs"
INITRAMFS_IMAGE_BUNDLE = "1"
These lines do in fact create an initramfs built in version of my Kernel and puts it in the deploy directory by the name Image-Initramfs.bin. It is slightly larger than the Image kernel file that successfully boots. So Yocto ends up building 2 kernels, one with initramfs, and one without.
ubuntu#ip:~/Desktop/jetson-yocto/build$ du -sh tmp/deploy/images/jetson-nano/Image-Initramfs.bin
36M tmp/deploy/images/jetson-nano/Image-Initramfs.bin
ubuntu#ip:~/Desktop/jetson-yocto/build$ du -sh tmp/deploy/images/jetson-nano/Image--4.9+git0+3c02a65d91-r0-jetson-nano-20190729195650.bin
33M tmp/deploy/images/jetson-nano/Image--4.9+git0+3c02a65d91-r0-jetson-nano-20190729195650.bin
The docs say this is accomplished with a secondary compilation path:
Controls whether or not the image recipe specified by INITRAMFS_IMAGE is run through an extra pass (do_bundle_initramfs) during kernel compilation in order to build a single binary that contains both the kernel image and the initial RAM filesystem (initramfs) image. This makes use of the CONFIG_INITRAMFS_SOURCE kernel feature.
Note
Using an extra compilation pass to bundle the initramfs avoids a circular dependency between the kernel recipe and the initramfs recipe should the initramfs include kernel modules. Should that be the case, the initramfs recipe depends on the kernel for the kernel modules, and the kernel depends on the initramfs recipe since the initramfs is bundled inside the kernel image.
The problem is that this initramfs Kernel is not installed by Yocto into the final SD Card image. Only the non-initramfs Kernel is installed. I have not been able to find a Yocto directive/setting on how to make it install the initramfs version instead of the non-initramfs one.
How can I do this?
If you are using wic tool to generate the SD card image then you can add something like below in local.conf
`IMAGE_BOOT_FILES_append = " Image-Initramfs.bin;${KERNEL_IMAGETYPE}"`
however if you are using custom script then you have to provide more information
and customize the SD card generation script.
Related
I want to enable tc command that comes in iproute2 on my linux kernel. My kernel is built using yocto and bitbake.
So, I copied the iproute recipes and whole directory from the following link to try --
https://git.yoctoproject.org/cgit.cgi/poky/plain/meta/recipes-connectivity/iproute2
And included in my yocto build. That picked up recipe and built it all well. But I tc command is still not available on the built kernel.
Question:
What am I missing and how to enable tc in the kernel of a linux image built using Yocto recipes?
You shouldn't need to copy the whole recipe, poky should be in your sources directory. So just reference the recipe in your image. You need both iproute2 and iproute2-tc.
IMAGE_INSTALL += "iproute2 \
iproute2-tc"
Additionally you may need to enable some kernel modules that tc make use of, depending on your needs:
CONFIG_NET_SCHED
CONFIG_NET_SCH_CBQ
CONFIG_NET_SCH_HTB
CONFIG_NET_SCH_HFSC
CONFIG_NET_SCH_ATM
CONFIG_NET_SCH_PRIO
CONFIG_NET_SCH_MULTIQ
CONFIG_NET_SCH_RED
CONFIG_NET_SCH_SFQ
CONFIG_NET_SCH_TEQL
CONFIG_NET_SCH_TBF
CONFIG_NET_SCH_GRED
CONFIG_NET_SCH_DSMARK
CONFIG_NET_SCH_NETEM
CONFIG_NET_SCH_INGRESS
How do I extract the kernel configuration from a kernel image file?
The kernel image file type is:
/boot/kernel7.img: Linux kernel ARM boot executable zImage (little-endian)
The kernel has been compiled with CONFIG_IKCONFIG enabled. However,
scripts/extract-ikconfig /boot/kernel7.img
returns
extract-ikconfig: Cannot find kernel config.
Note: I am trying the get the config without booting the kernel.
If the kernel has been compiled with CONFIG_IKCONFIG=m (note the m), the configuration in stored in a module (configs.ko) and not in the kernel itself. That's the reason why running extract-ikconfig on the kernel image fails.
In this case, we can extract the config from the configuration module:
/usr/src/$(uname -r)/scripts/extract-ikconfig \
/lib/modules/$(uname -r)/kernel/kernel/configs.ko
I like to play around with a pre-emptive linux kernel and Yocto.
As hardware the SAMA5D3x Evalboard + SAMA5D35-CM module is used.
Atmel is providing a meta-atmel layer, which includes the "at91-linux_*.bb" recipe. This recipe builds the kernel for the SAMA5D3x machines.
For using the realtime kernel I should insert the realtime patches and activate them at the kernel config.
I did not found a tutorial how to do this with an existing kernel. My question is:
How/where to modify a given kernel recipe to make it a realtime kernel(preempt-rt)?
My test project is located at the
project dir "/home/user/yocto". It has following content:
"/yocto git clone" ==> Yocto system
"/meta-openembedded" ==> meta embedded recipes
"/meta-atmel" ==> atmels yocto layer
"/meta-atmel/recipes-kernel/linux/linux-at91_4.4.bb" ==> the kernel recipe
"/meta-atmel/conf/machine/sama5d3xek.conf" ==> the machine that run the kernel
"/myTest" ==> my test project
"/myTest/recipes-kernel/linux-at91_%.bbappend" ==> replace the kernel config + add own device tree
"/myTest/recipes-kernel/linux/linux-at91/sama5d3xek/defconfig" ==> my own kernel config
/myTest/recipes-kernel/linux/linux-at91/sama5d3xek/myDev.dts ==> my own device tree
Any ideas/tutorials how to manage to activate the RT-Kernel in Yocto?
In general:
in .../source/poky/recipes-kernel/linux you should find a linux-yocto-rt_X.XX.bb recipe to compile a full preemptive RT kernel.
For meta-atmel you should do:
Download the correct RT patch for your kernel version and apply it using a .bbappend file to your current linux kernel recipe. You could find the patch HERE
Add the patch to your bbappend file (stored in your own layer in the one of accepted direcotries). p.e.: SRC_URI += "file://0001-linux-rt.patch"
Activate preemptive kernel. Manually set CONFIG_PREEMPT=y at defconfig at your layer. Alternativly you can use bitbake virtual/kernel -c menuconfig
Pitfalls at meta-atmel:
the linux-at91_4.4.bb recipe does not care about patch and sublevel of the kernel (p.e. 4.4.66 -> ..). if there is a new version at at91-linux it will go after some time to the meta-atmel layer.
the RT branch of the linux kernel is not provided for every new sublevel
this means constant breaks of your own meta-layer
I'm compiling linux for an ARM board. I need to make some customized changes into an existing driver code present in the kernel repository and reload the driver.
I was expecting to find a ".ko" file in the driver directory after doing the make, but no such file exists. Apparently uImage/device tree image compilation doesn't work that way.
Do I need to write my own Makefile for standalone device driver compilation?
It may be a silly question, but sorry I'm pretty new to kernel/device drivers.
EDIT:
I followed the process outlined here: http://odroid.com/dokuwiki/doku.php?id=en:c1_building_kernel
After git checkout and installing the cross-compiler(arm-linux-gnueabihf-gcc 4.9.2), I issue the basic make comands
$ make odroidc_defconfig
$ make -j4
$ make -j4 modules
$ make uImage
All the steps are successful. The last few lines of log look like
KSYM .tmp_kallsyms1.o
KSYM .tmp_kallsyms2.o
LD vmlinux
SORTEX vmlinux
SYSMAP System.map
OBJCOPY arch/arm/boot/ccImage
Kernel: arch/arm/boot/ccImage is ready
Image arch/arm/boot/ccImage.lzo is ready
UIMAGE arch/arm/boot/uImage
Image Name: Linux-3.10.72
Created: Sat Mar 28 22:44:45 2015
Image Type: ARM Linux Kernel Image (lzo compressed)
Data Size: 5459649 Bytes = 5331.69 kB = 5.21 MB
Load Address: 00208000
Entry Point: 00208000
Image arch/arm/boot/uImage is ready
EDIT 2: Path to the driver code
https://github.com/hardkernel/linux/tree/odroidc-3.10.y/drivers/amlogic/efuse
Examining your Makefile
#
# Makefile for eFuse.
#
obj-$(CONFIG_EFUSE) += efuse_bch_8.o efuse_version.o efuse_hw.o efuse.o
We learn that the code can be built as either a loadable module, or permanently linked into the kernel itself.
Examining odroidc_defconfig from branch odroidc-3.10.y-android mentioned in your instructions we find
#
# EFUSE Support
#
CONFIG_EFUSE=y
With the "y" indicating that the code is to be linked into the driver. Had it instead said "m" it would be built as a module.
It's possible you could change that in the kernel config, but it might also cause problems if there's nothing setup to load the module before it is needed.
Likely simply installing the newly built kernel with the code already linked inside (ie, forgetting about the module idea) will work.
Not sure if you are still looking for the answers to this question.
But looking at the Kconfig file in your code, show that -
config EFUSE
bool "EFUSE Driver"
And since all your driver files are compiled with this config, the above config description allows the CONFIG_EFUSE to be 'n' or 'y'. So you can only build static modules (build-in) with this.
All you need to do is change the above description to:
config EFUSE
**tristate** "EFUSE Driver"
and also change the other configs in Kconfig to tristate.
This will allow your driver to be compiled as module once you select the driver as 'M' in your kernel config. Then you should be able to see the ".ko" file corresponding to the driver.
Also do make sure to use EXPORT_SYMBOL(foo) when building the driver as module so that any dependencies are taken care of when loading module symbols.
I'm trying to compile a kernel (altered version of 2.6.32.9, found here https://github.com/rabeeh/linux-2.6.32.9). I am doing the compilation on a emulated ARM system (qemu) (yes, I should probably cross-compile, but that's a different topic) running Ubuntu Core (https://wiki.ubuntu.com/Core) and the kernel (vmlinuz) from Ubuntu 11.04 (downloaded from http://ports.ubuntu.com/ubuntu-ports/dists/natty/main/installer-armel/current/images/versatile/netboot/vmlinuz).
After running make bzImage, I look in the arch/arm/boot folder, and find only a file called zImage. I tried using this zImage instead of the vmlinuz I downloaded from ubuntu.com in qemu, but that doesn't work, just shows a black screen. I guess zImage is not the same as bzImage, which is what I think vmlinuz (judging from different articles on the internet) is.
So, a few questions:
Why doesn't make bzImage produce a bzImage/vmlinuz?
Can I convert a vmlinux to a vmlinuz using for example mkimage (there are lots of guides on the opposite...)?
Thanks
The bzImage filename and make target was originally x86-specific (big zImage). Many of the bootloaders on architectures that are not equal to baremetal-x86 (SPARC, PPC, IA64, etc. and also Xen on *) directly take vmlinux (or one of its compressed forms, for example vmlinux.gz, aka zImage). I guess some maintainers just added bzImage as a make target name because they wanted to have the x86 madness on their arch as well.
I get the result you describe by asking qemu to emulate a different cpu than arm926ej-s. But booting versatilepb with the default cpu works. I've cross-compiled my kernel, and I compiled all the drivers into it (so I don't use initrd).
Just download 100MB arm-eabi toolchain from http://www.mentor.com/embedded-software/sourcery-tools/sourcery-codebench/editions/lite-edition/ (it's free but they want your email, like the x86 Intel compiler). It has an installer, just say "next" until it's done, like on Windows. Then add the bin directory to your path:
export PATH=~/CodeSourcery/Sourcery_CodeBench_Lite_for_ARM_EABI/bin/:$PATH
Then go back to your kernel source dir and do
make ARCH=arm CROSS_COMPILE=arm-none-eabi- menuconfig
make ARCH=arm CROSS_COMPILE=arm-none-eabi- zImage modules
You can do
sudo make ARCH=arm CROSS_COMPILE=arm-none-eabi- INSTALL_MOD_PATH=path_to_arm_root modules_install
if you can reach your ARM filesystem from the host. If you're using NFS root it's trivial, but if you're using a disk image you need to either:
use a raw disk image and kpartx (depends on your host kernel having dm-multipath) or
qemu-nbd which supports qcow (and depends on host kernel having network block device support)
To boot in qemu with disk you need the right drivers (SYM53C8XX SCSI). The versatile defconfig doesn't select those.