Linux Kernel Journey
This article walks through the step‑by‑step initialization of KVM's hyp mode memory mapping on ARM64, covering EL2 register setup, identity mapping, page‑table allocation, stack preparation, and code section mappings required for a functional hypervisor environment.
This article explains the evolution of file system architecture from kernel‑level VFS to userspace via FUSE, reviews the historical role of NFS, details JuiceFS's implementation on top of FUSE, and presents benchmark results that demonstrate its high throughput and practical limitations.
Last Branch Record (LBR) is a CPU‑level feature that records branch jumps; the Linux kernel’s bpf_get_branch_snapshot helper (since 5.16) enables eBPF programs to capture LBR data, and the bpflbr tool demonstrates how to trace kernel functions and bpf program execution, disassemble code, and output call stacks.
This article explains how to identify and resolve multithreaded deadlocks in Linux C++ programs by using shell utilities such as ps and top for initial diagnosis, then attaching GDB to inspect thread stacks and pinpoint the exact lock contention causing the freeze.
This article explains why Linux programs may exit unexpectedly, introduces the backtrace utility and its underlying call‑stack mechanism, and provides step‑by‑step instructions—including compilation flags, signal handling, and address‑to‑source mapping—to accurately locate the root cause of crashes.
This article explains why Linux processes need to communicate, describes the kernel‑mediated IPC framework, compares shared‑memory and message‑passing approaches, and provides detailed code examples for pipes, FIFOs, signals, files, semaphores, sockets, plus real‑world use cases and case studies.
The article explains how Linux kernel scheduling uses a hierarchical topology—balancing load and preserving cache affinity—by mapping real‑world multi‑core hardware structures such as sockets, dies, clusters, and NUMA nodes to sched_domain and sched_group, and shows how to inspect and tune this layout with CONFIG_SCHED_DEBUG and QEMU simulation.
The article explains how to add runtime‑configurable filtering of kernel function arguments in eBPF programs by parsing a C‑style expression, validating its AST, converting it to BPF instructions using BTF metadata, and injecting the generated code into the probe, with a complete example for skb filtering.
The article provides a detailed technical analysis of Linux 5.9 on arm64 KVM, explaining how Host and Guest OSes are distinguished at EL1, how HCR_EL2 flags control mode switching, and how the EL2 exception vector and related registers are initialized during Linux boot to enable KVM virtualization.
This article explains how CPU caches bridge the speed gap between the processor and main memory, describes cache hierarchy, locality principles, write policies, coherence protocols, and provides concrete C code examples and practical tips such as data alignment and loop restructuring to improve cache hit rates and overall program speed.
