Why can't the kernel run init?

Question

I've downloaded the Raspbian image on this page. I'm trying to compile a kernel that can be used to boot the image within qemu.

I downloaded the Linux kernel source from kernel.org and ran:

make versatile_defconfig
make menuconfig

I then added the following features to the kernel:

• PCI support (CONFIG_PCI)
• SCSI Device Support (CONFIG_SCSI)
• SCSI Disk Support (CONFIG_BLK_DEV_SD)
• SYM53C8XX Version 2 SCSI Support (CONFIG_SCSI_SYM53C8XX_2)
• The Extended 3 (ext3) filesystem (CONFIG_EXT3_FS)
• The Extended 4 (ext4) filesystem (CONFIG_EXT4_FS)

I also loop mounted the disk image and:

• commented out /etc/ld.so.preload
• adjusted /etc/fstab to use /dev/sda1 and /dev/sda2

I then unmounted the image and attempted to start the machine with:

qemu-system-arm \
    -M versatilepb \
    -m 256 \
    -kernel linux-4.3/arch/arm/boot/zImage \
    -hda 2015-09-24-raspbian-jessie.img \
    -serial stdio \
    -append "root=/dev/sda2 rootfstype=ext4 rw console=ttyAMA0"

The kernel was able to mount the filesystem but it immediately ran into some trouble:

Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004

CPU: 0 PID: 1 Comm: init Not tainted 4.3.0 #1
Hardware name: ARM-Versatile PB
[<c001b5c0>] (unwind_backtrace) from [<c0017e18>] (show_stack+0x10/0x14)
[<c0017e18>] (show_stack) from [<c0069860>] (panic+0x84/0x1ec)
[<c0069860>] (panic) from [<c0025b98>] (do_exit+0x81c/0x850)
[<c0025b98>] (do_exit) from [<c0025c5c>] (do_group_exit+0x3c/0xb8)
[<c0025c5c>] (do_group_exit) from [<c002dfcc>] (get_signal+0x14c/0x59c)
[<c002dfcc>] (get_signal) from [<c001bf28>] (do_signal+0x84/0x3a0)
[<c001bf28>] (do_signal) from [<c0017a94>] (do_work_pending+0xb8/0xc8)
[<c0017a94>] (do_work_pending) from [<c0014f30>] (slow_work_pending+0xc/0x20)
---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004

At first, I wondered if this wasn't related to SELinux. I tried booting the kernel with:

selinux=0 enforcing=0

...but it made absolutely no difference.

What am I doing wrong? And what does this error mean?

Updates

I have also tried the following, with no luck:

• I tried compiling with and without CONFIG_VFP enabled
• I added CONFIG_DEVTMPFS and CONFIG_DEVTMPFS_MOUNT
• Applying this patch and enabling CPU_V6, CONFIG_MMC_BCM2835, & CONFIG_MMC_BCM2835_DMA
• Using the gcc-linaro-arm-linux-gnueabihf-raspbian toolchain

• Compiling a simple C program with the toolchain and then passing its path to the kernel via init= works - leading me to believe there's a discrepancy between binary formats

  • file <sample program>:

    ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, for GNU/Linux 2.6.26, BuildID[sha1]=e5ec8884499c51b248df60aedddfc9acf72cdbd4, not stripped
    

  • file <file from the image>:

    ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=3e92423821f3325f8cb0ec5d918a7a1c76bbd72c, stripped`
    

  • diff of ELF header

I compiled this simple C program with the toolchain:

<path>/arm-linux-gnueabihf-gcc --static simple.c -o simple

...and copied it to /root in the image, changing the init= boot parameter to /root/simple. This gives me the following when booting:

Starting bash...
Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004

It seems to be choking on the execv() call.

Answer 1

I've also tried booting ARM images with QEMU with no reliable success. I am sorry to say that you will have to use real hardware to work with a ARM OS, or wait patiently for developers to make a more reliable emulator for ARM.

Its Dec 2018, and still there are still issues with qemu-system-arm.

I was able to boot Raspbian Jessie on a QEMU emulator using a freshly installed Ubuntu 18 Bionic, however it was not stable for my work so I had to leave it for real hardware. It would freeze up frequently.

qemu-system-arm did not work on my OS, so I used Virtualbox to install Ubuntu Bionic and inside Bionic I installed Raspbian with QEMU.

I followed this tutorial: https://azeria-labs.com/emulate-raspberry-pi-with-qemu/

Good luck

Answer 2

I know it's a somewhat aged question, but since there are still no good answers for testing Raspberry Pi images with QEMU, allow me to contribute a partial answer.

I wanted to use the Ubuntu 16.04 raspi3 image with QEMU. Downloaded it, extracted it, mounted the boot partition, got the vmlinuz file and the initrd file, and ... qemu-system-arm -M blabla -cpu ... -kernel ... doesn't work. Black screen.

Then using a kernel-qemu-4.4.34-jessie from here with the xenial image/rootfs led to the same "init killed" problem you have.

But since I'm using a known good kernel, and since your simple statically linked C program works, it's likely the problem only surfaces when one uses the dynamic linker. (And the linker is not particularly sensitive to kernels, because the ld-2.24 from the latest debian9 (stretch) based raspbian works fine on a 4.4 debian8 (jessie) based kernel.)

Even after copying the files that do work on/with the "jessie" image into the ubuntu xenial image I only got a weird "calling preinit: KE" error.

Oh, and anyone looking at compiling a kernel for a Raspberry Pi, should check this site, which directly references the "official" docs/howto.

Answer 3

The linux kernel does not run init anymore instead it runs systemd which is like init but a bit more advanced features and extra multitasking capcbilities, although against unix philosophy systemd is useful.