汇编、链接与运行工具链

You write assembly in mnemonics like MOV and ADD, but the CPU only speaks binary machine code. The toolchain bridges that gap.

Step 1: the assembler translates each mnemonic into its machine-instruction bytes, producing an object file (.o or .obj).

An object file holds machine code plus metadata — symbols, sections, relocations. It isn't runnable yet because addresses aren't final.

Code and data live in named sections: .text for instructions, .data for initialized data, .bss for uninitialized data.

Step 2: the linker combines object files, resolves the symbol references between them, and assigns final addresses to build the executable.

When code calls a label defined elsewhere, the assembler leaves a placeholder. The linker fills in the real address during relocation.

Step 3: when you run it, the OS loader maps the sections into memory, sets up the stack, and jumps to the entry point.

Execution begins at a start symbol — typically _start for raw Linux assembly, or main when you link with the C runtime.

Static linking copies library code into the binary; dynamic linking loads shared libraries at run time, keeping the executable smaller.

Inspect each stage: objdump disassembles, readelf shows headers and sections, and nm lists the symbols.

The full flow: assembler turns .asm into objects, the linker joins objects into an executable, and the loader runs it as a process.

Test your understanding of the toolchain.

You learned the toolchain: assembler makes objects, the linker resolves symbols into an executable, and the loader turns it into a running process.