Out of Deep Respect: 1700 Years of Jewish Life

I was born German Jewish, and I am posting this out of deep respect for that heritage. It is humbling to reflect on 1700 years of Jewish life in German-speaking lands—a history that spans centuries of culture, community, and contribution. Learning about this legacy is a way of honoring those who came before and those who gave their lives.

1700 Years of Jewish Life in German-Speaking Lands

RK3588 ARM Inbetriebnahme: U-Boot, Kernel und Signalintegrität

Der RK3588 SoC verfügt über eine Quad-Core Arm Cortex-A76/A55 CPU, eine Mali-G610 GPU und eine hochflexible I/O-Architektur, die ihn ideal für eingebettete Linux SBCs wie den Radxa Rock 5B+ macht.

Ich habe die Inbetriebnahme dieser Plattform erforscht und dokumentiert, einschließlich meiner Beiträge zu u-boot und dem Linux-Kernel, der Entwicklung des Device Trees sowie der Werkzeuge für reproduzierbare Builds und die Validierung der Signalintegrität. Der Großteil dieser Arbeit befindet sich noch in der aktiven Entwicklungsphase und der frühen Vorbereitungsphase für die Veröffentlichung im Upstream-Projekt.

Ich veröffentliche hier meine Notizen, Messungen und Inbetriebnahme-Artefakte im Laufe der Arbeit, während die aktive u-boot- und Kernelentwicklung einschließlich Patch-Iteration, Test-Builds und Branch-Historie in separaten Arbeits-Repositories gepflegt wird:

Signalanalyse / Bring-Up-Repository: https://github.com/brhinton/signal-analysis

Das Repository umfasst derzeit (und es werden ständig weitere hinzugefügt):

• Device-Tree-Quellen und Rock 5B+ Board-Aktivierung
• UART-Signalintegritätsmessungen mit 1,5 Mbit/s am SoC-Pad
• Anleitung zum Erstellen von Kernel, Bootloader und Debugging-Setup
• Frühe Patch-Workflows und Upstream-Vorbereitungsnotizen

Zusätzliche Arbeiten an U-Boot und dem Linux-Kernel, einschließlich Mainline-Test-Builds, Funktionsentwicklung, Rebase-Updates und laufenden Patch-Serien, werden in separaten Arbeits-Repositories verwaltet. Dieses Repository dient als zentraler Ort für Messungen, Dokumentation und Inbetriebnahmehinweise auf Boardebene.

Dies ist ein fortlaufendes, noch in Entwicklung befindliches technisches Projekt, und ich werde die Repositories aktualisieren, sobald zusätzliche Messungen, Boards und für die Upstream-Entwicklung geeignete Änderungen vorbereitet sind.

arch linux uefi with dm-crypt and uki

Arch Linux is known for its high level of customization, and configuring LUKS2 and LVM is a straightforward process. This guide provides a set of instructions for setting up an Arch Linux system with the following features:

• Root file system encryption using LUKS2.
• Logical Volume Management (LVM) for flexible storage management.
• Unified Kernel Image (UKI) bootable via UEFI.
• Optional: Detached LUKS header on external media for enhanced security.

Prerequisites

• A bootable Arch Linux ISO.
• An NVMe drive (e.g., /dev/nvme0n1).
• (Optional) A microSD card or other external medium for the detached LUKS header.

Important Considerations

• Data Loss: The following procedure will erase all data on the target drive. Back up any important data before proceeding.
• Secure Boot: This guide assumes you may want to use hardware secure boot.
• Detached LUKS Header: Using a detached LUKS header on external media adds a significant layer of security. If you lose the external media, you will lose access to your encrypted data.
• Swap: This guide uses a swap file. You may also use a swap partition if desired.

Step-by-Step Instructions

1. Boot into the Arch Linux ISO:

   Boot your system from the Arch Linux installation media.

2. Set the System Clock:

   # timedatectl set-ntp true

3. Prepare the Disk:

   • Identify your NVMe drive (e.g., /dev/nvme0n1). Use lsblk to confirm.
   • Wipe the drive:

   # wipefs --all /dev/nvme0n1

   • Create an EFI System Partition (ESP):

   # sgdisk /dev/nvme0n1 -n 1::+512MiB -t 1:EF00

   • Create a partition for the encrypted volume:

   # sgdisk /dev/nvme0n1 -n 2 -t 2:8300

4. Set up LUKS2 Encryption:

   Encrypt the second partition using LUKS2. This example uses aes-xts-plain64 and serpent-xts-plain ciphers, and SHA512 for the hash. Adjust as needed.

   # cryptsetup luksFormat --cipher aes-xts-plain64 \
     --keyslot-cipher serpent-xts-plain --keyslot-key-size 512 \
     --use-random -S 0 -h sha512 -i 4000 /dev/nvme0n1p2

   • --cipher: Specifies the cipher for data encryption.
   • --keyslot-cipher: Specifies the cipher used to encrypt the key.
   • --keyslot-key-size: Specifies the size of the key slot.
   • -S 0: Disables sparse headers.
   • -h: Specifies the hash function.
   • -i: Specifies the number of iterations.

   Open the encrypted partition:

   # cryptsetup open /dev/nvme0n1p2 root

5. Create the File Systems and Mount:

   Create an ext4 file system on the decrypted volume:

   # mkfs.ext4 /dev/mapper/root

   Mount the root file system:

   # mount /dev/mapper/root /mnt

   Create and mount the EFI System Partition:

   # mkfs.fat -F32 /dev/nvme0n1p1
   # mount --mkdir /dev/nvme0n1p1 /mnt/efi

   Create and enable a swap file:

   # dd if=/dev/zero of=/mnt/swapfile bs=1M count=8000 status=progress
   # chmod 600 /mnt/swapfile
   # mkswap /mnt/swapfile
   # swapon /mnt/swapfile

6. Install the Base System:

   Use pacstrap to install the necessary packages:

   # pacstrap -K /mnt base base-devel linux linux-hardened \
     linux-hardened-headers linux-firmware apparmor mesa \
     xf86-video-intel vulkan-intel git vi vim ukify

7. Generate the fstab File:

   # genfstab -U /mnt >> /mnt/etc/fstab

8. Chroot into the New System:

   # arch-chroot /mnt

9. Configure the System:

   Set the timezone:

   # ln -sf /usr/share/zoneinfo/UTC /etc/localtime
   # hwclock --systohc

   Uncomment en_US.UTF-8 UTF-8 in /etc/locale.gen and generate the locale:

   # sed -i 's/#'"en_US.UTF-8"' UTF-8/'"en_US.UTF-8"' UTF-8/g' /etc/locale.gen
   # locale-gen
   # echo 'LANG=en_US.UTF-8' > /etc/locale.conf
   # echo "KEYMAP=us" > /etc/vconsole.conf

   Set the hostname:

   # echo myhostname > /etc/hostname
   # cat <<EOT >> /etc/hosts
   127.0.0.1 myhostname
   ::1 localhost
   127.0.1.1 myhostname.localdomain myhostname
   EOT

   Configure mkinitcpio.conf to include the encrypt hook:

   # sed -i 's/HOOKS.*/HOOKS=(base udev autodetect modconf kms \
     keyboard keymap consolefont block encrypt filesystems resume fsck)/' \
     /etc/mkinitcpio.conf

   Create the initial ramdisk:

   # mkinitcpio -P

   Install the bootloader:

   # bootctl install

   Set the root password:

   # passwd

   Install microcode and efibootmgr:

   # pacman -S intel-ucode efibootmgr

   Get the swap offset:

   # swapoffset=`filefrag -v /swapfile | awk '/\s+0:/ {print $4}' | \
     sed -e 's/\.\.$//'`

   Get the UUID of the encrypted partition:

   # blkid -s UUID -o value /dev/nvme0n1p2

   Create the EFI boot entry. Replace <UUID OF CRYPTDEVICE> with the actual UUID:

   # efibootmgr --disk /dev/nvme0n1p1 --part 1 --create --label "Linux" \
     --loader /vmlinuz-linux --unicode "cryptdevice=UUID=<UUID OF CRYPTDEVICE>:root \
     root=/dev/mapper/root resume=/dev/mapper/root resume_offset=$swapoffset \
     rw initrd=\intel-ucode.img initrd=\initramfs-linux.img" --verbose

   Configure the UKI presets:

   # cat <<EOT >> /etc/mkinitcpio.d/linux.preset
   ALL_kver="/boot/vmlinuz-linux"
   ALL_microcode=(/boot/*-ucode.img)
   PRESETS=('default' 'fallback')
   default_uki="/efi/EFI/Linux/arch-linux.efi"
   default_options="--splash /usr/share/systemd/bootctl/splash-arch.bmp"
   fallback_uki="/efi/EFI/Linux/arch-linux-fallback.efi"
   fallback_options="-S autodetect"
   EOT

   Create the UKI directory:

   # mkdir -p /efi/EFI/Linux

   Configure the kernel command line:

   # cat <<EOT >> /etc/kernel/cmdline
   cryptdevice=UUID=<UUID OF CRYPTDEVICE>:root root=/dev/mapper/root \
   resume=/dev/mapper/root resume_offset=51347456 rw
   EOT

   Build the UKIs:

   # mkinitcpio -p linux

   Configure the kernel install layout:

   # echo "layout=uki" >> /etc/kernel/install.conf

10. Configure Networking (Optional):

    Create a systemd-networkd network configuration file:

    # cat <<EOT >> /etc/systemd/network/nic0.network
    [Match]
    Name=nic0
    [Network]
    DHCP=yes
    EOT

11. Install a Desktop Environment (Optional):

    Install Xorg, Xfce, LightDM, and related packages:

    # pacman -Syu
    # pacman -S xorg xfce4 xfce4-goodies lightdm lightdm-gtk-greeter \
      libva-intel-driver mesa xorg-server xorg-xinit sudo
    # systemctl enable lightdm
    # systemctl start lightdm

12. Enable Network Services (Optional):

    # systemctl enable systemd-resolved.service
    # systemctl enable systemd-networkd.service
    # systemctl start systemd-resolved.service
    # systemctl start systemd-networkd.service

13. Create a User Account:

    Create a user account and add it to the wheel group:

    # useradd -m -g wheel -s /bin/bash myusername

14. Reboot:

    Exit the chroot environment and reboot your system:

    # exit
    # umount -R /mnt
    # reboot

Multidimensional arrays of function pointers in C

Embedded hardware typically includes an application processor and one or more adjacent processor(s) attached to the printed circuit board. The firmware that resides on the adjacent processor(s) responds to instructions or commands.  Different processors on the same board are often produced by different companies.  For the system to function properly, it is imperative that the processors communicate without any issues, and that the firmware can handle all types of possible errors.

Formal requirements for firmware related projects may include the validation and verification of the firmware on a co-processor via the application programming interface (API).  Co-processors typically run 8, 16, or 32-bit embedded operating systems.  If the co-processor manufacturer provides a development board for testing the firmware on a specific co-processor, then the development board may have it's own application processor. Familiarity with all of the applicable bus communication protocols including synchronous and asynchronous communication is important.  High-volume testing of firmware can be accomplished using function-like macros and arrays of function pointers.  Processor specific firmware is written in C and assembly - 8, 16, 32, or 64-bit.  Executing inline assembly from C is straightforward and often required.  Furthermore, handling time-constraints such as real-time execution on adjacent processors is easier to deal with in C and executing syscalls, low-level C functions, and userspace library functions, is often more efficient.  Timing analysis is often a key consideration when testing firmware, and executing compiled C code on a time-sliced OS, such as Linux, is already constrained.

To read tests based on a custom grammar, a scanner and parser in C can be used. Lex is ideal for building a computationally efficient lexical analyzer that outputs a sequence of tokens. For this case, the tokens comprise the function signatures and any associated function metadata such as expected execution time. Creating a context-free grammar and generating the associated syntax tree from the lexical input is straightforward.   Dynamic arrays of function pointers can then be allocated at run-time, and code within external object files or libraries can be executed in parallel using multiple processes or threads. The symbol table information from those files can be stored in multi-dimensional arrays. While C is a statically typed language, the above design can be used for executing generic, variadic functions at run-time from tokenized input, with constant time lookup, minimal overhead, and specific run-time expectations (stack return value, execution time, count, etc.).

At a high level, lists of pointers to type-independent, variadic functions and their associated parameters can be stored within multi-dimensional arrays.  The following C code uses arrays of function pointers to execute functions via their addresses.  The code uses list management functions from the Linux kernel which I ported to userspace.

https://github.com/brhinton/bcn

Concurrency, Parallelism, and Barrier Synchronization - Multiprocess and Multithreaded Programming

On preemptive, timed-sliced UNIX or Linux operating systems such as Solaris, AIX, Linux, BSD, and OS X, program code from one process executes on the processor for a time slice or quantum. After this time has elapsed, program code from another process executes for a time quantum. Linux divides CPU time into epochs, and each process has a specified time quantum within an epoch. The execution quantum is so small that the interleaved execution of independent, schedulable entities – often performing unrelated tasks – gives the appearance of multiple software applications running in parallel.

When the currently executing process relinquishes the processor, either voluntarily or involuntarily, another process can execute its program code. This event is known as a context switch, which facilitates interleaved execution. Time-sliced, interleaved execution of program code within an address space is known as concurrency.

The Linux kernel is fully preemptive, which means that it can force a context switch for a higher priority process. When a context switch occurs, the state of a process is saved to its process control block, and another process resumes execution on the processor.

A UNIX process is considered heavyweight because it has its own address space, file descriptors, register state, and program counter. In Linux, this information is stored in the task_struct. However, when a process context switch occurs, this information must be saved, which is a computationally expensive operation.

Concurrency applies to both threads and processes. A thread is an independent sequence of execution within a UNIX process, and it is also considered a schedulable entity. Both threads and processes are scheduled for execution on a processor core, but thread context switching is lighter in weight than process context switching.

In UNIX, processes often have multiple threads of execution that share the process's memory space. When multiple threads of execution are running inside a process, they typically perform related tasks. The Linux user-space APIs for process and thread management abstract many details. However, the concurrency level can be adjusted to influence the time quantum so that the system throughput is affected by shorter and longer durations of schedulable entity execution time.

While threads are typically lighter weight than processes, there have been different implementations across UNIX and Linux operating systems over the years. The three models that typically define the implementations across preemptive, time-sliced, multi-user UNIX and Linux operating systems are defined as follows - 1:1, 1:N, and M:N where 1:1 refers to the mapping of one user-space thread to one kernel thread, 1:N refers to the mapping of multiple user-space threads to a single kernel thread. M:N refers to the mapping of N user-space threads to M kernel threads.

In the 1:1 model, one user-space thread is mapped to one kernel thread. This allows for true parallelism, as each thread can run on a separate processor core. However, creating and managing a large number of kernel threads can be expensive.

In the 1:N model, multiple user-space threads are mapped to a single kernel thread. This is more lightweight, as there are fewer kernel threads to create and manage. However, it does not allow for true parallelism, as only one thread can execute on a processor core at a time.

In the M:N model, N user-space threads are mapped to M kernel threads. This provides a balance between the 1:1 and 1:N models, as it allows for both true parallelism and lightweight thread creation and management. However, it can be complex to implement and can lead to issues with load balancing and resource allocation.

Parallelism on a time-sliced, preemptive operating system means the simultaneous execution of multiple schedulable entities over a time quantum. Both processes and threads can execute in parallel across multiple cores or processors. Concurrency and parallelism are at play on a multi-user system with preemptive time-slicing and multiple processor cores. Affinity scheduling refers to scheduling processes and threads across multiple cores so that their concurrent and parallel execution is close to optimal.

It's worth noting that affinity scheduling refers to the practice of assigning processes or threads to specific processors or cores to optimize their execution and minimize unnecessary context switching. This can improve overall system performance by reducing cache misses and increasing cache hits, among other benefits. In contrast, non-affinity scheduling allows processes and threads to be executed on any available processor or core, which can result in more frequent context switching and lower performance.

Software applications are often designed to solve computationally complex problems. If the algorithm to solve a computationally complex problem can be parallelized, then multiple threads or processes can all run at the same time across multiple cores. Each process or thread executes by itself and does not contend for resources with other threads or processes working on the other parts of the problem to be solved. When each thread or process reaches the point where it can no longer contribute any more work to the solution of the problem, it waits at the barrier if a barrier has been implemented in software. When all threads or processes reach the barrier, their work output is synchronized and often aggregated by the primary process. Complex test frameworks often implement the barrier synchronization problem when certain types of tests can be run in parallel. Most individual software applications running on preemptive, time-sliced, multi-user Linux and UNIX operating systems are not designed with heavy, parallel thread or parallel, multiprocess execution in mind.

Minimizing lock granularity increases concurrency, throughput, and execution efficiency when designing multithreaded and multiprocess software programs. Multithreaded and multiprocess programs that do not correctly utilize synchronization primitives often require countless hours of debugging. The use of semaphores, mutex locks, and other synchronization primitives should be minimized to the maximum extent possible in computer programs that share resources between multiple threads or processes. Proper program design allows schedulable entities to run parallel or concurrently with high throughput and minimum resource contention. This is optimal for solving computationally complex problems on preemptive, time-sliced, multi-user operating systems without requiring hard, real-time scheduling.

A hardware design for variable output frequency using an n-bit counter

The DE1-SoC from Terasic is an excellent board for hardware design and prototyping. The following VHDL process is from a hardware design created for the Terasic DE1-SoC FPGA. The ten switches and four buttons on the FPGA are used as an n-bit counter with an adjustable multiplier to increase the output frequency of one or more output pins at a 50% duty cycle.

As the switches are moved or the buttons are pressed, the seven-segment display is updated to reflect the numeric output frequency, and the output pin(s) are driven at the desired frequency. The onboard clock runs at 50MHz, and the signal on the output pins is set on the rising edge of the clock input signal (positive edge-triggered). At 50MHz, the output pins can be toggled at a maximum rate of 50 million cycles per second or 25 million rising edges of the clock per second. An LED attached to one of the output pins would blink 25 million times per second, not recognizable to the human eye. The persistence of vision, which is the time the human eye retains an image after it disappears from view, is approximately 1/16th of a second. Therefore, an LED blinking at 25 million times per second would appear as a continuous light to the human eye.

scaler <= compute_prescaler((to_integer(unsigned( SW )))*scaler_mlt);
gpiopulse_process : process(CLOCK_50, KEY(0))
begin
    if (KEY(0) = '0') then  -- async reset
        count <= 0;
    elsif rising_edge(CLOCK_50) then
        if (count = scaler - 1) then
            state <= not state;
            count <= 0;
        elsif (count = clk50divider) then -- auto reset
            count <= 0;
        else
            count <= count + 1;
        end if;
    end if;
end process gpiopulse_process;

The scaler signal is calculated using the compute_prescaler function, which takes the value of a switch (SW) as an input, multiplies it with a multiplier (scaler_mlt), and then converts it to an integer using to_integer. This scaler signal is used to control the frequency of the pulse signal generated on the output pin.

The gpiopulse_process process is triggered by a rising edge of the CLOCK_50 signal and a push-button (KEY(0)) press. It includes an asynchronous reset when KEY(0) is pressed.

The count signal is incremented on each rising edge of the CLOCK_50 signal until it reaches the value of scaler - 1. When this happens, the state signal is inverted and count is reset to 0. If count reaches the value of clk50divider, it is also reset to 0.

Overall, this code generates a pulse signal with a frequency controlled by the value of a switch and a multiplier, which is generated on a specific output pin of the FPGA board. The pulse signal is toggled between two states at a frequency determined by the scaler signal.

It is important to note that concurrent statements within an architecture are executed concurrently, meaning that they are evaluated concurrently and in no particular order. However, the sequential statements within a process are executed sequentially, meaning that they are evaluated in order, one at a time. Processes themselves are executed concurrently with other processes, and each process has its own execution context.

Creating stronger keys for OpenSSH and GPG

Create Ed25519 SSH keypair (supported in OpenSSH 6.5+). Parameters are as follows:

-o save in new format
-a 128 for 128 kdf (key derivation function) rounds
-t ed25519 for type of key

ssh-keygen -o -a 128 -t ed25519 -f .ssh/ed25519-$(date '+%m-%d-%Y') -C ed25519-$(date '+%m-%d-%Y')

Create Ed448-Goldilocks GPG master key and sub keys.

# gpg --quick-generate-key ed448-master-key-$(date '+%m-%d-%Y') ed448 sign 0
# gpg --list-keys --with-colons "ed448-master-key-08-03-2021" | grep fpr
# gpg --quick-add-key "$fpr" cv448 encr 2y
# gpg --quick-add-key "$fpr" ed448 auth 2y
# gpg --quick-add-key "$fpr" ed448 sign 2y