Bootloader

RustDesk High-Risk Alert: Botnet Scans Continue, New Wave of Critical Vulnerabilities Arrives If you’re using RustDesk, 2026 might be the year you need to pay the most attention to security. In the first half of the year, botnets were scanning the entire internet for RustDesk IDs, launching automated attacks. Before the second half even began,... » read more

Copy Fail (CVE-2026-31431) Diagnosis & Fix Guide: Is Your Server Compromised? The previous article covered how serious this vulnerability is. Now let’s get practical — how to check if your system is affected, how to fix it, and what to do in an emergency. One thing upfront: If your server is shared by multiple users... » read more

CVE-2026-31431 (Copy Fail): Root with a Single Python Script — A 9-Year Linux Kernel Blight On April 29, 2026, the security research team Theori disclosed a Linux kernel vulnerability codenamed Copy Fail, numbered CVE-2026-31431, with a CVSS score of 7.8 (High). But what makes this vulnerability truly unsettling isn’t the score — it’s three facts:... » read more

B02 — The ID Card of RAM: What’s Actually Stored in the SPD Chip Key insight: RAM without SPD is like a person without ID — the system doesn’t know who it is. SPD Chip Basics Every DDR memory module has an SPD (Serial Presence Detect) chip, a 256-byte (or 512-byte for DDR5) EEPROM. SPD... » read more

B07 — From e820 to Memory Management Initialization: The memblock Allocator Key insight: The kernel’s first step at boot is to figure out how much memory it has to manage. How the Kernel Gets Memory Info At boot, the kernel obtains physical memory info through two methods: Directly from BIOS (legacy): via INT 15h E820h... » read more

B03 — The Complete Boot Flow: From Pressing Power to Handing Control to the Kernel Key Insight: Every boot is a precision relay race. Every handoff must be flawless. Overview of the Complete Boot Flow After pressing the power button, the computer goes through a series of stages before finally handing control to the OS... » read more

B04 — From Real Mode to Protected Mode: GDT and CR0 Setup Key Insight: Protected mode doesn’t “protect” memory. It allows the CPU to manage more complex memory access rules. Limitations of Real Mode After reset, the CPU defaults to Real Mode, the operating mode from the 8086 era. Real Mode has two severe limitations:... » read more

B08 — Memory Layout of Kernel Space and User Space: vmalloc vs kmalloc Key Insight: The division of virtual address space is one of the most important OS design decisions. x86-64 Virtual Address Space Layout Modern Linux uses a 48-bit virtual address space. User space and kernel space each have separate regions: x86-64 虚拟地址空间布局： 0x0000000000000000... » read more

B11 — Modern Computer Memory Layout: Complete Virtual to Physical Address Mapping Key Insight: Understanding memory layout is the key to understanding system design. Evolution from Physical to Virtual Addressing Early computers (before the 80286) had no MMU. They directly used physical addresses. Later, segmentation was introduced, then paging, making memory layouts increasingly complex. 内存布局的演进：... » read more

B10 — Why fork is Fast: The Copy-On-Write Mechanism Key Insight: Don’t copy, just share. Until it’s actually needed. The Traditional Problem with fork: Massive Memory Copying The fork system call creates a new process. The traditional implementation copies the entire memory space of the parent process: 传统 fork 的问题： 父进程内存：假设 1GB fork() 执行时： -... » read more

B01 — BIOS’s First Map for the OS: The e820 Memory Map Key Insight: When the computer starts, the first problem the OS must solve is: how much memory is there and where is it? The OS’s First Question After Power-On After power-on, BIOS (UEFI) first completes hardware initialization. Then the OS starts booting. The... » read more

B09 — What Happens When Memory Runs Low: kswapd and Page Frame Reclaim Key Insight: When memory runs tight, the system quietly moves infrequently used data to disk. This is swapping. Sources of Memory Pressure Linux always starts tidying up when memory approaches full. It swaps out infrequently used pages to disk, making room for... » read more

B06 — The Manager of Physical Memory: The Buddy System Key Insight: Grouping memory into “buddies” makes both allocation and reclamation efficient. Why Do We Need the Buddy System The OS needs to manage physical memory allocation and reclamation. The simplest approach is bitmap management, but it is inefficient for allocating large blocks. 位图管理的问题： 假设用... » read more

B05 — How the MMU Translates Virtual Addresses to Physical Addresses Key Insight: Behind every virtual address is a complex translation process. And you never perceive it. What is an MMU The MMU is a hardware unit on the CPU chip. It translates Virtual Addresses (VA) to Physical Addresses (PA). MMU 在系统中的位置： CPU Core Memory... » read more