ACPI AML Runtime Debugger in Ubuntu 18.04 (x64)

Alex Hung

Alex Hung

on 14 February 2019

Ubuntu AML debugging

ACPICA is an open-source project that provides an operating system (OS)-independent reference implementation. It also contains a list of utilities such as ASL compiler (iasl), acpiexec (an AML emulator). However, AML debugging on Linux in run-time wasn’t provided in ACPICA until Linux Kernel 4.13.

Enabling AML Debugging

The aml-debugger.txt is the instruction for enabling AML run-time debugger. This document is available at Documentation/acpi/ in Linux kernel source code. In short, two things are required for AML run-time debugging

  • Enable AML debugging (CONFIG_ACPI_DEBUGGER=y & CONFIG_ACPI_DEBUGGER_USER=m) when compiling Linux kernel
  • Compile an utility, acpidbg from Linux kernel (I uploaded a copy here)

While compiling a custom-build kernel is nothing new to kernel developers, it is often inconvenient for system firmware / BIOS developers. Fortunately, Ubuntu 18.04 (x64) and later enable these config by default. One can simply execute acpidbg on Ubuntu 18.04 – even on Ubuntu Live from USB too!

Running AML Debugging

Executing acpidbg on Ubuntu 18.04 (x64) is straight-forward

$ sudo ./acpidbg 

and “help” shows a list supported commands

- help

General-Purpose Commands:            
Namespace Access Commands:
Control Method Execution Commands: 


acpidbg is particularly handy when one needs to evaluate any ACPI AML objects during run-time – especially ones that change under different conditions. This may be explained by some examples below:

Example 1 – To determine AC power status in run-time.

  1. Find _PSR objects
  2. Evaluate _PSR when AC is disconnected
  3. Evaluate _PSR when AC is connected
- find _PSR
        \_SB.PCI0.LPC.EC.AC._PSR Method       00000000c53d0a47 01 Args 0 Len 0023 Aml 00000000eab88cb2

- execute \_SB.PCI0.LPC.EC.AC._PSR
Evaluating \_SB.PCI0.LPC.EC.AC._PSR
Evaluation of \_SB.PCI0.LPC.EC.AC._PSR returned object 00000000c46fa555, external buffer length 18
 [Integer] = 0000000000000000

- execute \_SB.PCI0.LPC.EC.AC._PSR
Evaluating \_SB.PCI0.LPC.EC.AC._PSR
Evaluation of \_SB.PCI0.LPC.EC.AC._PSR returned object 00000000c46fa555, external buffer length 18
 [Integer] = 0000000000000001

acpidbg also works with complex objects such as packages.

Example 2 – To determine battery information and status

  1. Find _BIF and _BST objects
  2. Evaluate _BIF and _BST objects (note _BST changes dynamically).
- find _BIF
      \_SB.PCI0.LPC.EC.BAT0._BIF Method       00000000817541c3 01 Args 0 Len 0040 Aml 000000009abb252e

- execute \_SB.PCI0.LPC.EC.BAT0._BIF
Evaluating \_SB.PCI0.LPC.EC.BAT0._BIF
Evaluation of \_SB.PCI0.LPC.EC.BAT0._BIF returned object 00000000c46fa555, external buffer length 170
 [Package] Contains 13 Elements:
  [Integer] = 0000000000000000
  [Integer] = 000000000000ABE0
  [Integer] = 0000000000009E34
  [Integer] = 0000000000000001
  [Integer] = 0000000000003B60
  [Integer] = 00000000000007E9
  [Integer] = 00000000000000C8
  [Integer] = 0000000000000001
  [Integer] = 0000000000000001
  [String] Length 07 = "00HW027"
  [String] Length 05 = "  409"
  [String] Length 03 = "LiP"
  [String] Length 03 = "SMP"

- find _BST
      \_SB.PCI0.LPC.EC.BAT0._BST Method       00000000ed98c5ba 01 Args 0 Len 001D Aml 00000000a48eaeb6

- execute \_SB.PCI0.LPC.EC.BAT0._BST
Evaluating \_SB.PCI0.LPC.EC.BAT0._BST
Evaluation of \_SB.PCI0.LPC.EC.BAT0._BST returned object 00000000c46fa555, external buffer length 78
 [Package] Contains 4 Elements:
  [Integer] = 0000000000000001
  [Integer] = 00000000000010C6
  [Integer] = 00000000000088B8
  [Integer] = 0000000000003FC9

acpidbg can decode bit fields and save time on counting bits. Try to run acpidbg to evaluate any _PLD objects and you will see what I mean :).

Ubuntu desktop

Learn how the Ubuntu desktop operating system powers millions of PCs and laptops around the world.

Newsletter signup

Select topics you’re interested in

In submitting this form, I confirm that I have read and agree to Canonical’s Privacy Notice and Privacy Policy.

Related posts

Open infrastructure, developer desktop and IoT are the focus for Ubuntu 19.04

18th April, 2019: Canonical today announced the release of Ubuntu 19.04, focused on open infrastructure deployments, the developer desktop, IoT, and cloud to edge software distribution. “The open-source-first on Ubuntu movement in telco,…

Debug ACPI DSDT and SSDT with ACPICA Utilities

Using acpidbg on Ubuntu 18.04 x64 can be quite handy; however, the Linux kernel with ACPI_DEBUGGER is not always available, such as on Ubuntu for ARM. In such cases, acpica also provides a set of utilities, named acpica-tools, for ACPI…

Make your snap development faster

“All my centurions develop using snaps.” Julius Caesar By and large, software development can be an enjoyable process. Until you hit the first error, that is. At that point, you want to get past the stumbling blocks as quickly as possible…