Tag: AARCH64

The _start function uses a Global Offset Table (GOT) entry to load the address of main primarily because _start is defined in a pre-compiled object file (typically Scrt1.o) that was built with Position-Independent Code (PIC) enabled. Here is the detailed explanation of why this happens and why adrp + add isn't used by default: 1. _start is Pre-Compiled Generic Code The _start function is not compiled at the same time as your application's main.c. It is part of the C Runtime (CRT) startup files (specifically Scrt1.o for Position…

In AArch64 (ARMv8-A 64-bit architecture), Pre-indexing and Post-indexing are memory addressing modes used with Load (LDR) and Store (STR) instructions. Their primary purpose is to perform Writeback: they automatically update the base register (the pointer) with a new address as part of the instruction execution. This is extremely efficient for iterating through arrays or managing stacks because it eliminates the need for a separate ADD or SUB instruction to move the pointer. Here is the breakdown of how they work. 1. Pre-Indexed Addressing Syntax: [base, #offset]!Key Symbol: The…