February, 2024

Writing an OS Kernel from Scratch | 351: NIC — From PHY to Socket Abstract: The network card is the gateway for a computer to connect to the network. Data travels from the application socket all the way through the protocol stack, driver, bus, and reaches the PHY, finally becoming optical/electrical signals transmitted over the... » read more

# Writing an OS Kernel from Scratch – Part 35: TCP/IP Protocol Stack — Using socket to GET the Baidu Homepage! “The NIC driver is just the hardware interface; real networking capability lies in the protocol stack. Today, we implement a minimal TCP/IP stack and use a user-mode program to download the Baidu homepage!” In... » read more

# Writing an OS Kernel from Scratch – Part 13: sysfs — Exposing Kernel Information as Files “Kernel runtime state is hidden in registers and memory — how can users view it? Today, we implement sysfs, making CPU, memory, and process information readable like regular files!” In the previous article, we got standard streams (stdin/stdout/stderr)... » read more

Writing an OS Kernel from Scratch | Windows Boot Manager vs GRUB: A Complete Analysis of Two Boot Loaders From 360 to 362, we covered the BIOS/UEFI → MBR/GPT → GRUB boot chain. GRUB is the standard bootloader for Linux, but Windows uses a completely different system — BOOTMGR (Boot Manager) and BCD (Boot Configuration... » read more

Writing an OS Kernel from Scratch | 348: I2C Bus — The Blood Vessels of Embedded Systems Abstract: I2C is the most common low-speed bus in embedded systems. With just two wires, it can connect a large number of devices — sensors, EEPROMs, RTCs, touchscreen controllers… This article covers I2C protocol principles, master-slave architecture, and... » read more

A03 — Multi-threaded malloc: Arena Contention and Per-thread Arena Key Insight: In multi-threaded scenarios, every malloc is a potential contention point. ptmalloc uses arenas to solve this problem. The Problem with Multi-threaded malloc In single-threaded programs, malloc contention is rare (only one heap). But in multi-threaded programs, all threads share the same heap. Without special... » read more

Writing an OS Kernel from Scratch | Synchronization Primitives — spinlock and semaphore, How the OS Coordinates Concurrent Access Two processes write data to the same file simultaneously — process A writes the first 100 bytes, process B writes the next 100 bytes. If no coordination is done, what happens? Process A just read the... » read more