How to Inspect Registers in ARM Debugger: Quick Guide

To inspect registers in an ARM debugger, use the info registers command to display all general-purpose registers and special registers. You can also view specific registers by typing print $register_name or use register read in some ARM debugging tools.

Syntax

The common commands to inspect registers in ARM debuggers are:

• info registers: Shows all general-purpose and special registers.
• print $register_name: Displays the value of a specific register (e.g., print $r0).
• register read: Reads and displays registers (used in some ARM-specific debuggers).

These commands let you check the current state of CPU registers during debugging.

bash

info registers
print $r0
register read

Example

This example shows how to inspect registers using gdb for an ARM target.

After stopping at a breakpoint, use info registers to see all registers, or print $pc to see the program counter.

gdb

(gdb) info registers
r0            0x1                 1
r1            0x0                 0
r2            0x7fff0000          2147418112
pc            0x8000abcd          0x8000abcd <main>

(gdb) print $pc
$1 = 0x8000abcd <main>

Output

r0            0x1                 1
r1            0x0                 0
r2            0x7fff0000          2147418112
pc            0x8000abcd          0x8000abcd <main>

$1 = 0x8000abcd <main>

Common Pitfalls

Common mistakes when inspecting registers include:

• Using incorrect register names (e.g., r16 does not exist on ARM).
• Not stopping the program before inspecting registers, which shows stale or invalid data.
• Confusing register values with memory contents; registers hold CPU data, not memory directly.

Always ensure the program is paused and use correct register names like r0 to r15, pc, sp, and lr.

gdb

(gdb) print $r16
No symbol "r16" in current context.

# Correct usage:
(gdb) print $r0
$1 = 0x1

Output

No symbol "r16" in current context.

$1 = 0x1

Quick Reference

Command	Description
info registers	Display all CPU registers and their values
print $register_name	Show value of a specific register (e.g., $r0, $pc)
register read	Read and display registers (ARM-specific debuggers)
continue	Resume program execution after inspection
break	Set breakpoint to pause program and inspect registers

Key Takeaways

Use info registers to view all ARM CPU registers at once.

Inspect specific registers with print $register_name for focused debugging.

Always pause the program before checking registers to get accurate values.

Use correct ARM register names like r0-r15, pc, sp, and lr to avoid errors.

Refer to debugger-specific commands as some tools may differ slightly.