Linux Kernel Module Cheat

24.10.4. gem5 config.ini

The m5out/config.ini file, contains a very good high level description of the system:

less $(./getvar --arch arm --emulator gem5 m5out_dir)"

That file contains a tree representation of the system, sample excerpt:

[root]
type=Root
children=system
full_system=true

[system]
type=ArmSystem
children=cpu cpu_clk_domain
auto_reset_addr_64=false
semihosting=Null

[system.cpu]
type=AtomicSimpleCPU
children=dstage2_mmu dtb interrupts isa istage2_mmu itb tracer
branchPred=Null

[system.cpu_clk_domain]
type=SrcClockDomain
clock=500

Each node has:

a list of child nodes, e.g. system is a child of root, and both cpu and cpu_clk_domain are children of system
a list of parameters, e.g. system.semihosting is Null, which means that Semihosting was turned off
- the type parameter shows is present on every node, and it maps to a Python object that inherits from SimObject.
  
  For example, AtomicSimpleCPU maps is defined at src/cpu/simple/AtomicSimpleCPU.py.

Set custom configs with the --param option of fs.py, e.g. we can make gem5 wait for GDB to connect with:

fs.py --param 'system.cpu[0].wait_for_remote_gdb = True'

More complex settings involving new classes however require patching the config files, although it is easy to hack this up. See for example: patches/manual/gem5-semihost.patch.

Modifying the config.ini file manually does nothing since it gets overwritten every time.

gem5 config.dot