ACPI AML Runtime Debugger in Ubuntu 18.04 (x64)

Ubuntu is available in Cloud Server Linux. Contact us to find out our latest offers!

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: 
 ...
 ...

Examples

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.

  1. Find _BIF and _BST objects
  2. Evaluate _BIF and _BST objects (note _BST changes dynamically).

Example 2 – To determine battery information and status

- 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 :).

The post ACPI AML Runtime Debugger in Ubuntu 18.04 (x64) appeared first on Ubuntu Blog.

Ubuntu is available in Cloud Server Linux. Contact us to find out our latest offers!

Comments are closed.

>
WhatsApp chat WhatsApp us