Gem 5 IOError: Can't find a path to system files. Full System X86 simulation setup

Question

I\'ve already got Gem5 installed. I\'m trying to do a full system simulation. I added M5_PATH

echo \"export M5_PATH==/home/sam/security/gem5/full/\" >&         


        

Answer 1

Update 2020-01

As of 82f6d6e90f36e400db1f38eef5fe17430313458e reviewed at https://gem5-review.googlesource.com/c/public/gem5/+/23672/7 the CLI insanity has reduced substantially:

• M5_PATH is not required anymore on X86 if you point to all required files explicitly:

  fs.py --kernel path/to/vmlinux --disk-image path/to/rootfs.ext2
  

  The second disk named linux-bigswap2.img and x86_64-vmlinux-2.6.22.9 are not needed anymore, and you can pass multiple disks at will with multiple --disk-image options, see: How to attach multiple disk images in a simulation with gem5 fs.py?

• on ARM, M5_PATH can also be dispensed, but you also need to point the bootloader with:

  fs.py --bootloader ./system/arm/bootloader/arm64/boot.arm64
  

If you miss any of those files, M5_PATH gets used.

Note that just like the PATH search algorithm, paths without / are only searched under M5_PATH, so if you want to point to a file in the current directory you need to add ./ as in:

fs.py --kernel ./vmlinux

see also: Why do you need ./ (dot-slash) before executable or script name to run it in bash?

Old answer

gem5 is picky about some path names, but you don't need to patch it to achieve a decent image setup.

For example, this working setup with gem5 e2656006df442a995bf80ee03fa9700d6ec14537 essentially runs:

M5_PATH=/full/path/to/system \
  build/X86/gem5.opt \
  configs/example/fs.py \
  --disk-image /any/path/to/rootfs.ext2 \
  --kernel /any/path/to/vmlinux

and /full/path/to/system contains:

./disks/linux-bigswap2.img
./binaries/x86_64-vmlinux-2.6.22.9

Both of those files are dummies which I generated from here with:

dd if=/dev/zero of=./binaries/linux-bigswap2.img count=1 bs=16k
touch disks/x86_64-vmlinux-2.6.22.9

Yes, this is a horrible workaround to gem5's opinionated image searching... someone should really patch gem5 to not look for those images if you pass --disk-image and --kernel yourself...

As always, have a try at debugging it with prints and PDB: it should then be simple to figure out why something didn't work for you.