Blog#

Jun 17, 2023
in elf
3 min read

Program Compilation Process

The compilation is the process of converting the source code of the C language into machine code. As C is a mid-level language, it needs a compiler to convert it into an executable code so that the program can be run on our machine.

In computing, a compiler is a computer program that translates computer code written in one programming language (the source language) into another language (the target language). The name "compiler" is primarily used for programs that translate source code from a high-level programming language to a low-level programming language (e.g. assembly language, object code, or machine code) to create an executable program.

In C and C++ programming language terminology, a translation unit (or more casually a compilation unit) is the ultimate input to a C or C++ compiler from which an object file is generated. A translation unit roughly consists of a source file after it has been processed by the C preprocessor, meaning that header files listed in #include directives are literally included, sections of code within #ifndef may be included, and macros have been expanded.

Jun 16, 2023
in elf
9 min read

ELF layout

The Executable and Linkable Format (ELF), is a common standard file format for executable files, object code, shared libraries, and core dumps.

Jun 15, 2023
in arm, toolchain
9 min read

GNU Assembler Directives

Directives are used mainly to define symbols, allocate storage, and control the behavior of the assembler. Directives allow the programmer to control how the assembler does its job.

Jun 15, 2023
in arm
18 min read

ARM64 PCS - calling convention and stack layout

Previously, we've introduced the basic concepts associated with AAPCS (AArch64 Procedure Call Standard).

In this article we'll have a closer look at the ARM64 PCS, with demonstrations of the call conventions and stack layout.

Jun 15, 2023
in arm
7 min read

ARM64 PCS - Procedure Call Standard

In this article we'll introduce the basic concepts of AAPCS (AArch64 PCS), including program flow, function/subroutine and the Procedure Call Standard.

Jun 14, 2023
in arm
5 min read

ARM Conditional Execution

In this article, we'll explore ARM program flow based on conditional execution.

Jun 14, 2023
in arm
13 min read

ARM Push/Pop Stack Modes

In this article, we'll explore the stack modes, activities and accesses in ARM(A32/A64).

Jun 13, 2023
in arm
6 min read

ARM Load/Store Addressing Modes

In this article, we'll comb through the Load/Store addressing modes based on offset and index in ARM(A32/A64).

There are three fundamental addressing modes in AArch64 instructions: register offset, immediate offset, and literal.

For information about addressing modes, see Load/Store addressing modes.

Jun 12, 2023
in arm, linux
6 min read

ADRP & LDR in arm64/kernel primary switch

In linux arm64 kernel, the transition of the PC from the physical address space to the real virtual address space is completed with the last three instructions of head.S after MMU enabled.

    ldr     x8, =__primary_switched
    adrp    x0, KERNEL_START        // __pa(KERNEL_START)
    br      x8                      // executed with the MMU enabled

Jun 10, 2023
in arm
4 min read

ARM ADR vs. LDR

Since both the LDR pseudo-instruction and the ADRP instruction can load the address of a label, and the LDR pseudo-instruction can address the 64-bit address space, and the addressing range of the ADRP instruction is the current PC address ±4GB, then what is the necessity of having an ADRP instruction when there's already an LDR pseudo-instruction?