First draft of 'Extending gem5 for Arm' (#17)
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+---
+layout: documentation
+title: Extending gem5 to run ARM binaries
+doc: Learning gem5
+parent: pt1
+permalink: /extending_configs/
+author: Julian T. Angeles
+---
+
+Extending gem5 for ARM
+======================
+
+This chapter assumes you've already built a basic x86 system with
+gem5 and created a simple configuration script.
+
+Downloading ARM Binaries
+------------------------
+
+Let's start by downloading some ARM benchmark binaries. Begin
+from the root of the gem5 folder:
+
+```
+mkdir -p cpu_tests/benchmarks/bin/arm
+cd cpu_tests/benchmarks/bin/arm
+wget gem5.org/dist/current/gem5/cpu_tests/benchmarks/bin/arm/Bubblesort
+wget gem5.org/dist/current/gem5/cpu_tests/benchmarks/bin/arm/FloatMM
+```
+
+We'll use these to further test our ARM system.
+
+Building gem5 to run ARM Binaries
+---------------------------------
+
+Just as we did when we first built our basic x86 system, we run
+the same command, except this time we want it to compile with the
+default ARM configurations. To do so, we just replace x86 with ARM:
+
+```
+scons build/ARM/gem5.opt -j20
+```
+
+When compilation is finished you should have a working gem5 executable
+at `build/ARM/gem5.opt`.
+
+Modifying simple.py to run ARM Binaries
+---------------------------------------
+
+Before we can run any ARM binaries with our new system, we'll have
+to make a slight tweak to our simple.py.
+
+If you recall when we created our simple configuration script, it was
+noted that we did not have to connect the PIO and interrupt ports to
+the memory bus for any ISA other than for an x86 system. So let's
+remove those 3 lines:
+
+```
+system.cpu.createInterruptController()
+#system.cpu.interrupts[0].pio = system.membus.master
+#system.cpu.interrupts[0].int_master = system.membus.slave
+#system.cpu.interrupts[0].int_slave = system.membus.master
+
+system.system_port = system.membus.slave
+```
+
+You can either delete or comment them out as above. Next let's set
+the processes command to one of our ARM benchmark binaries:
+
+```
+process.cmd = ['cpu_tests/benchmarks/bin/arm/Bubblesort']
+```
+
+If you'd like to test a simple hello program as before, just
+replace x86 with arm:
+
+```
+process.cmd = ['tests/test-progs/hello/bin/arm/linux/hello']
+```
+
+Running gem5
+------------
+
+Simply run it as before, except replace X86 with ARM:
+
+```
+build/ARM/gem5.opt configs/tutorial/simple.py
+```
+
+If you set your process to be the Bubblesort benchmark, your
+output should look like this:
+
+```
+gem5 Simulator System. http://gem5.org
+gem5 is copyrighted software; use the --copyright option for details.
+
+gem5 compiled Oct 3 2019 16:02:35
+gem5 started Oct 6 2019 13:22:25
+gem5 executing on amarillo, pid 77129
+command line: build/ARM/gem5.opt configs/tutorial/simple.py
+
+Global frequency set at 1000000000000 ticks per second
+warn: DRAM device capacity (8192 Mbytes) does not match the address range assigned (512 Mbytes)
+0: system.remote_gdb: listening for remote gdb on port 7002
+Beginning simulation!
+info: Entering event queue @ 0. Starting simulation...
+info: Increasing stack size by one page.
+warn: readlink() called on '/proc/self/exe' may yield unexpected results in various settings.
+ Returning '/home/jtoya/gem5/cpu_tests/benchmarks/bin/arm/Bubblesort'
+-50000
+Exiting @ tick 258647411000 because exiting with last active thread context
+```
