OABIbased

OABIbased refers to software, toolchains, or systems that are built to run on ARM architecture using the Old ARM Application Binary Interface (OABI). The OABI was an early ARM ABI used in many Linux ports and early ARM devices, and it was superseded by the ARM EABI (the new ABI). The term indicates compatibility with the older conventions for how functions receive arguments, return values, and how data is laid out in memory, rather than with modern ARM conventions.

Key characteristics of OABI include its distinct calling conventions, stack frame layout, and binary interfaces that differ from the later EABI. Because the two ABIs define different binary interfaces, OABI-based binaries typically require OABI-compatible libraries and kernel interfaces. They are not generally compatible with EABI-based userspace binaries and libraries without recompilation or special compatibility layers. As a result, software built for OABI cannot reliably run on systems exclusively using EABI, and vice versa, without appropriate tooling or emulation.

Historically, OABI was common in ARM Linux distributions during the 1990s and early 2000s. Over time, the ARM EABI became standard, leading to broad migration away from OABI. Today, OABI support is largely obsolete in mainstream distributions, and modern ARM software targets EABI with optional hard-float or soft-float variants depending on floating-point support. Some niche or legacy embedded environments may still reference OABI-based tooling, but they are increasingly rare.

Identification often involves the toolchain or binary tags used during compilation. If a system or package is described as OABIbased, it signals legacy ABI compatibility requirements that may necessitate using older kernels, libraries, or compilers. In general, new ARM software is designed for EABI.