How do you configure the exception vector table in ARMv8-A architecture?

由人工智能和领英社区提供技术支持

In ARMv8-A architecture, exceptions are events that disrupt the normal execution of a program and require special handling by the processor. Exceptions can be caused by internal or external sources, such as interrupts, faults, errors, or system calls. To handle exceptions, the processor needs to know where to find the appropriate code to execute, which is called the exception handler. The exception vector table is a data structure that provides the addresses of the exception handlers for each type of exception. In this article, you will learn how to configure the exception vector table in ARMv8-A architecture and how it relates to the MMU and the EL levels.

此文章中的业界达人

由社区从 4 条内容中精选。了解更多

PRANJAL KHAPARKAR

Senior Engineer at IBM India System Development Lab (ISDL) | Ex Qualcomm
Austin Kim

Linux kernel Engineer | Author | RISC-V | Arm | 4x LinkedIn Top Voice ??
Rajini Kasala

1 Exception levels and modes

ARMv8-A architecture supports four exception levels (EL0 to EL3) and two modes (AArch64 and AArch32) that determine the privilege and execution state of the processor. Each exception level has its own set of registers, stack pointer, and exception vector table. The mode indicates whether the processor is executing 64-bit or 32-bit instructions. The exception level and mode are controlled by the current exception level (CurrentEL) register and the execution state (ES) bit. The processor can switch between exception levels and modes when an exception occurs or when a special instruction is executed.

添加您的观点

Cmdr (Dr.?) Reji Kurien Thomas , FRSA, MLE?

I Empower Sectors as a Global Tech & Business Transformation Leader| Stephen Hawking Award 2024| Harvard Leader | UK House of Lord's Awardee | Fellow Royal Society | CyberSec | CCISO CISM CCNP-S CEH
举报内容
Determine the Exception levels (EL0 to EL3) and modes (AArch32 or AArch64) your application requires Set up the vector table with addresses for each exception type – Synchronous, IRQ, FIQ, SError, and System Call Initialise the Vector Base Address Register (VBAR) with the base address of the table Ensure each vector entry points to the appropriate handler function for the exception level and mode Configure stack pointers and other relevant registers for each exception level Test the setup thoroughly to ensure proper exception handling and system stability

已翻译

赞

2 Exception vector table format

The exception vector table is a contiguous block of memory that contains the addresses of the exception handlers for each type of exception. The format of the exception vector table depends on the mode of the processor. In AArch64 mode, the exception vector table consists of 16 128-bit entries, each containing four 32-bit addresses for the synchronous, IRQ, FIQ, and SError exception types. The exception vector table base address is stored in the VBAR_ELx register, where x is the exception level. In AArch32 mode, the exception vector table consists of eight 32-bit entries, each containing one address for the reset, undefined instruction, SVC, prefetch abort, data abort, reserved, IRQ, and FIQ exception types. The exception vector table base address is stored in the VBAR register.

添加您的观点

3 MMU and exception handling

The MMU (memory management unit) is a hardware component that translates virtual addresses to physical addresses and controls the access permissions and attributes of memory regions. The MMU can generate exceptions when it encounters a translation fault, a permission fault, or an alignment fault. The MMU also supports features such as address space identifiers (ASIDs), translation table walks, and memory attributes indirection registers (MAIRs) that affect the exception handling. For example, the ASID allows the processor to distinguish between different virtual address spaces and avoid flushing the translation cache when switching between them. The translation table walks determine how the processor locates the translation table entries for a given virtual address and which exception level to use for the access. The MAIRs define the memory attributes for each memory region, such as cacheability, shareability, and ordering.

添加您的观点

Rajini Kasala
举报内容
MMU is a hardware component in a computer's architecture that converts virtual addresses into physical addresses in the system's RAM. Its primary functions include address translation, memory protection, virtual memory, and cache management. Exception handling is the process of responding to unexpected or exceptional events, such as interrupts or errors. In ARMv8-A architecture, exception handling involves addressing unexpected events through an Exception Vector Table (EVT), managing privilege levels across different exception levels, and handling interrupts and aborts through specific routines. The processor also handles context switching, saving the current execution context before transferring control to the exception handler.

已翻译

赞

4 Exception vector table configuration

To configure the exception vector table in ARMv8-A architecture, the first step is to determine the exception level and mode of the processor and select the corresponding VBAR_ELx or VBAR register. Additionally, you must allocate a block of memory that is aligned to 2 KB (for AArch64 mode) or 1 KB (for AArch32 mode) and contains enough space for the exception vector table entries. Once this is done, write the base address of the memory block to the VBAR_ELx or VBAR register using an instruction that ensures visibility to all observers, such as DSB or ISB. Then, write the addresses of the exception handlers to the memory block using 32-bit instructions (for AArch64 mode) or 8-bit instructions (for AArch32 mode). Finally, you can choose to use the SCTLR_ELx or SCTLR registers to enable or disable features such as vector table alignment checking, endianness selection, or MMU enablement. By following these steps, you can configure the exception vector table in ARMv8-A architecture and handle exceptions efficiently and securely.

添加您的观点

Austin Kim

Linux kernel Engineer | Author | RISC-V | Arm | 4x LinkedIn Top Voice ??
(已编辑)
举报内容
If you would like to see how exception vector is configured in Linux kernel(v6.1), you can refer to __secondary_switched'(arch/arm64/kernel/head.S) If you disassemble __secondary_switched, below code can be seen below; MX:FFFFFFC008C2D2FC|__secondary_switched: hint #0x22 ; #34 MX:FFFFFFC008C2D300| mov x0,x20 ... MX:FFFFFFC008C2D318| msr #0x3,#0x0,c12,c0,#0x0,x5 ; VBAR_EL1,x5 MX:FFFFFFC008C2D31C| isb sy When 'msr #0x3,#0x0,c12,c0,#0x0,x5' (msr VBAR_EL1,x5) instruction is performed, the address of vectors is saved into VBAR_EL1. In Linux kernel, vectors is entry address for exception handler(exception vector)

已翻译

赞

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

添加您的观点

PRANJAL KHAPARKAR

Senior Engineer at IBM India System Development Lab (ISDL) | Ex Qualcomm
举报内容
1. Define the vector table aligned to 2 KB. 2. Set VBAR_ELx to the vector table address for the target exception level. 3. Ensure memory attributes are configured to allow execution for the vector table region. 4. Use ISB(barrier) after setting VBAR_ELx to ensure immediate use of the updated table. 5. Handle exceptions by saving/restoring state using SPSR_ELx and ELR_ELx, and return using ERET.

已翻译

赞

ARM Architecture

+ 关注

给文章评分

我们借助人工智能创建了此文章。您认为这篇文章怎么样？

很棒不太好

举报此文章

查看全部

How do you configure the exception vector table in ARMv8-A architecture?

1

2

3

4

5

1 Exception levels and modes

2 Exception vector table format

3 MMU and exception handling

4 Exception vector table configuration

5 Here’s what else to consider

ARM Architecture

给文章评分

感谢您的反馈

更多ARM Architecture相关文章

更多相关阅读内容