EABI

Embedded Application Binary Interface (EABI) is a family of application binary interfaces for the ARM architecture that defines the conventions used when code, libraries, and runtime environments interact. It specifies how binaries are linked, how data types are sized and aligned, how functions receive arguments and return values, and how exceptions and interrupts are handled. EABI was introduced to replace the older OABI and to provide a consistent, cross‑platform ABI across ARM-compatible systems and toolchains. It is closely aligned with the ARM Architecture Procedure Call Standard (AAPCS) and the ELF object file format.

Core elements of the EABI include a standardized calling convention, stack frame layout, and register usage, along with the chosen object file format. In 32-bit ARM EABI, arguments are typically passed in registers r0–r3, with r0 used for return values; r4–r11 are callee‑saved, and the stack grows downward with a defined alignment. The interface also defines floating-point handling, which exists in soft-float and hard-float variants. In hard-float ABIs, floating-point arguments and results may be passed in VFP/NEON registers; in soft-float ABIs they are passed in general-purpose registers and computed in software.

Adoption and usage: ARM Linux, Android, and many bare-metal toolchains support ARM EABI. Target triplets include arm-eabi for bare-metal environments and arm-linux-gnueabi or arm-linux-gnueabihf for Linux systems. The EABI is a practical implementation of the ARM calling standard and related ARM ABI specifications, with extensions such as AAPCS-VFP to cover floating-point support.