Sorry, not going to give you a straight-out example like you’re asking, because as you are already looking through the Linux source code, you have plenty of those to go around, and they don’t appear to help. No shame in that – every sane person is at least initially confused by memory access ordering issues … Read more
Register banking refers to providing multiple copies of a register at the same address. Taken from section 1.4.6 of the arm docs The term is referring to a solution for the problem that not all registers can be seen at once. There is a different register bank for each processor mode. The banked registers give … Read more
There are quite some difference between the two. Neon is a SIMD (Single Instruction Multiple Data) accelerator processor as part of the ARM core. It means that during the execution of one instruction the same operation will occur on up to 16 data sets in parallel. Since there is parallelism inside the Neon, you can … Read more
An ABI (Application Binary Interface) is a standard that defines a mapping between low-level concepts in high-level languages and the abilities of a specific hardware/OS platform’s machine code. That includes things like: how C/C++/Fortran/… data types are laid out in memory (data sizes / alignments) how nested function calls work (where and how the information … Read more
Currently, there are two exception models in the ARM architecture (reset is considered a kind of exception): The classic model, used in pre-Cortex chip and current Cortex-A/R chips. In it, the memory at 0 contains several exception handlers: Offset Handler =============== 00 Reset 04 Undefined Instruction 08 Supervisor Call (SVC) 0C Prefetch Abort 10 Data … Read more
The ARM processor has 2 instruction sets, the traditional ARM set, where the instructions are all 32-bit long, and the more condensed Thumb set, where most common instructions are 16-bit long (and some are 32-bit long). Which instruction set to run can be chosen by the developer, and only one set can be active (i.e. … Read more
Oh, ARM and their silly naming… It’s a common misconception, but officially there’s no such thing as a “Thumb-2 instruction set”. Ignoring ARMv8 (where everything is renamed and AArch64 complicates things), from ARMv4T to ARMv7-A there are two instruction sets: ARM and Thumb. They are both “32-bit” in the sense that they operate on up-to-32-bit-wide … Read more
ARM calls FIQ the fast interrupt, with the implication that IRQ is normal priority. In any real system, there will be many more sources of interrupts than just two devices and there will therefore be some external hardware interrupt controller which allows masking, prioritization etc. of these multiple sources and which drives the interrupt request … Read more
A Bin file is a pure binary file with no memory fix-ups or relocations, more than likely it has explicit instructions to be loaded at a specific memory address. Whereas…. ELF files are Executable Linkable Format which consists of a symbol look-ups and relocatable table, that is, it can be loaded at any memory address … Read more